Directrice de Recherche CNRS – Professeure attachée à l’ENS
Directrice du département Chimie de l’ENS
ENS – Département de chimie
24 rue Lhomond, 75005 Paris
Email: anne.boutin@ens.psl.eu
Phone: +33 144322429
Office: E135
Short bio
Education
- « Habilitation », University of Paris XI, Orsay 1999
- Ph. D. in chemical physics, University of Paris XI, Orsay, France 1992
- Graduate of « Ecole Normale Supérieure », Paris 1992
- M. Sc. (French Diplôme d’Etudes Approfondies) University of Paris XI 1990
Positions held
Research interests
- Thermodynamics of confined fluids
Awards and distinctions
- PhD award : « Nathalie Demassieux », Chancellerie des Universités de Paris, 1993
- Bronze Medal, Centre National de la Recherche Scientifique, Paris, 1999
- Légion d’honneur, 2017
Supervised students and post-doctorants
- 17 directions and co-directions
Teaching
- Statistical thermodynamics
Publications
2018 |
Structure and Dynamics of Water Confined in Imogolite Nanotubes Article de journal L Scalfi; G Fraux; A Boutin; F -X Coudert Langmuir, 34 (23), p. 6748–6756, 2018. @article{Scalfi:2018, title = {Structure and Dynamics of Water Confined in Imogolite Nanotubes}, author = {L Scalfi and G Fraux and A Boutin and F -X Coudert}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047523465&doi=10.1021%2facs.langmuir.8b01115&partnerID=40&md5=9455a53f6fa2fb1284823137a632d2e5}, doi = {10.1021/acs.langmuir.8b01115}, year = {2018}, date = {2018-01-01}, journal = {Langmuir}, volume = {34}, number = {23}, pages = {6748--6756}, abstract = {We have studied the properties of water adsorbed inside nanotubes of hydrophilic imogolite, an aluminum silicate clay mineral, by means of molecular simulations. We used a classical force field to describe the water and the flexible imogolite nanotube and validated it against the data obtained from first-principles molecular dynamics. With it, we observe a strong structuration of the water confined in the nanotube, with specific adsorption sites and a distribution of hydrogen bond patterns. The combination of number of adsorption sites, their geometry, and the preferential tetrahedral hydrogen bonding pattern of water leads to frustration and disorder. We further characterize the dynamics of the water, as well as the hydrogen bonds formed between water molecules and the nanotube, which is found to be more than 1 order of magnitude longer than water-water hydrogen bonds. Copyright © 2018 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We have studied the properties of water adsorbed inside nanotubes of hydrophilic imogolite, an aluminum silicate clay mineral, by means of molecular simulations. We used a classical force field to describe the water and the flexible imogolite nanotube and validated it against the data obtained from first-principles molecular dynamics. With it, we observe a strong structuration of the water confined in the nanotube, with specific adsorption sites and a distribution of hydrogen bond patterns. The combination of number of adsorption sites, their geometry, and the preferential tetrahedral hydrogen bonding pattern of water leads to frustration and disorder. We further characterize the dynamics of the water, as well as the hydrogen bonds formed between water molecules and the nanotube, which is found to be more than 1 order of magnitude longer than water-water hydrogen bonds. Copyright © 2018 American Chemical Society. |
On the use of the IAST method for gas separation studies in porous materials with gate-opening behavior Article de journal G Fraux; A Boutin; A H Fuchs; F -X Coudert Adsorption, 24 (3), p. 233–241, 2018. @article{Fraux:2018, title = {On the use of the IAST method for gas separation studies in porous materials with gate-opening behavior}, author = {G Fraux and A Boutin and A H Fuchs and F -X Coudert}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044316029&doi=10.1007%2fs10450-018-9942-5&partnerID=40&md5=094abd3fbb204080fc964f1f0781ba71}, doi = {10.1007/s10450-018-9942-5}, year = {2018}, date = {2018-01-01}, journal = {Adsorption}, volume = {24}, number = {3}, pages = {233--241}, abstract = {Abstract: Highly flexible nanoporous materials, exhibiting for instance gate opening or breathing behavior, are often presented as candidates for separation processes due to their supposed high adsorption selectivity. But this view, based on “classical” considerations of rigid materials and the use of the Ideal Adsorbed Solution Theory (IAST), does not necessarily hold in the presence of framework deformations. Here, we revisit some results from the published literature and show how proper inclusion of framework flexibility in the osmotic thermodynamic ensemble drastically changes the conclusions, in contrast to what intuition and standard IAST would yield. In all cases, the IAST method does not reproduce the gate-opening behavior in the adsorption of mixtures, and may overestimates the selectivity by up to two orders of magnitude. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract: Highly flexible nanoporous materials, exhibiting for instance gate opening or breathing behavior, are often presented as candidates for separation processes due to their supposed high adsorption selectivity. But this view, based on “classical” considerations of rigid materials and the use of the Ideal Adsorbed Solution Theory (IAST), does not necessarily hold in the presence of framework deformations. Here, we revisit some results from the published literature and show how proper inclusion of framework flexibility in the osmotic thermodynamic ensemble drastically changes the conclusions, in contrast to what intuition and standard IAST would yield. In all cases, the IAST method does not reproduce the gate-opening behavior in the adsorption of mixtures, and may overestimates the selectivity by up to two orders of magnitude. © 2018, Springer Science+Business Media, LLC, part of Springer Nature. |
Classical Polarizable Force Field to Study Hydrated Charged Clays and Zeolites Article de journal S Tesson; W Louisfrema; M Salanne; A Boutin; E Ferrage; B Rotenberg; V Marry Journal of Physical Chemistry C, 122 (43), p. 24690–24704, 2018. @article{Tesson:2018, title = {Classical Polarizable Force Field to Study Hydrated Charged Clays and Zeolites}, author = {S Tesson and W Louisfrema and M Salanne and A Boutin and E Ferrage and B Rotenberg and V Marry}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056108305&doi=10.1021%2facs.jpcc.8b06230&partnerID=40&md5=7039754c45487a2d939680ec685cf6d0}, doi = {10.1021/acs.jpcc.8b06230}, year = {2018}, date = {2018-01-01}, journal = {Journal of Physical Chemistry C}, volume = {122}, number = {43}, pages = {24690--24704}, abstract = {Following our previous works on dry clays, we extend the classical polarizable ion model (PIM) to hydrated dioctahedral clays by considering Na-, Cs-, Ca-, and Sr-montmorillonites in the mono- and bihydrated states. The parameters of the force field are determined by optimizing the atomic forces and dipoles on density functional theory calculations. The simulation results are compared with results obtained with CLAYFF force field and validated in comparison with the experiment. The X-ray diffraction patterns calculated from classical molecular dynamics simulations performed with the PIM force field are in very good agreement with experiments. We also demonstrate the transferability of PIM force field to other aluminosilicates: here, a faujasite-type zeolite compensated with Na+ with a significant improvement in cation locations compared to nonpolarizable force fields. © 2018 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Following our previous works on dry clays, we extend the classical polarizable ion model (PIM) to hydrated dioctahedral clays by considering Na-, Cs-, Ca-, and Sr-montmorillonites in the mono- and bihydrated states. The parameters of the force field are determined by optimizing the atomic forces and dipoles on density functional theory calculations. The simulation results are compared with results obtained with CLAYFF force field and validated in comparison with the experiment. The X-ray diffraction patterns calculated from classical molecular dynamics simulations performed with the PIM force field are in very good agreement with experiments. We also demonstrate the transferability of PIM force field to other aluminosilicates: here, a faujasite-type zeolite compensated with Na+ with a significant improvement in cation locations compared to nonpolarizable force fields. © 2018 American Chemical Society. |
Structure and Dynamics of Solvated Polymers near a Silica Surface: On the Different Roles Played by Solvent Article de journal E Perrin; M Schoen; F -X Coudert; A Boutin Journal of Physical Chemistry B, 122 (16), p. 4573–4582, 2018. @article{Perrin:2018, title = {Structure and Dynamics of Solvated Polymers near a Silica Surface: On the Different Roles Played by Solvent}, author = {E Perrin and M Schoen and F -X Coudert and A Boutin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046023808&doi=10.1021%2facs.jpcb.7b11753&partnerID=40&md5=454946e682d8338778f6c89c84b3f873}, doi = {10.1021/acs.jpcb.7b11753}, year = {2018}, date = {2018-01-01}, journal = {Journal of Physical Chemistry B}, volume = {122}, number = {16}, pages = {4573--4582}, abstract = {Whereas it is experimentally known that the inclusion of nanoparticles in hydrogels can lead to a mechanical reinforcement, a detailed molecular understanding of the adhesion mechanism is still lacking. Here we use coarse-grained molecular dynamics simulations to investigate the nature of the interface between silica surfaces and solvated polymers. We show how differences in the nature of the polymer and the polymer-solvent interactions can lead to drastically different behavior of the polymer-surface adhesion. Comparing explicit and implicit solvent models, we conclude that this effect cannot be fully described in an implicit solvent. We highlight the crucial role of polymer solvation for the adsorption of the polymer chain on the silica surface, the significant dynamics of polymer chains on the surface, and details of the modifications in the structure solvated polymer close to the interface. © 2018 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Whereas it is experimentally known that the inclusion of nanoparticles in hydrogels can lead to a mechanical reinforcement, a detailed molecular understanding of the adhesion mechanism is still lacking. Here we use coarse-grained molecular dynamics simulations to investigate the nature of the interface between silica surfaces and solvated polymers. We show how differences in the nature of the polymer and the polymer-solvent interactions can lead to drastically different behavior of the polymer-surface adhesion. Comparing explicit and implicit solvent models, we conclude that this effect cannot be fully described in an implicit solvent. We highlight the crucial role of polymer solvation for the adsorption of the polymer chain on the silica surface, the significant dynamics of polymer chains on the surface, and details of the modifications in the structure solvated polymer close to the interface. © 2018 American Chemical Society. |
2017 |
New Molecular Simulation Method to Determine Both Aluminum and Cation Location in Cationic Zeolites Article de journal M Jeffroy; C Nieto-Draghi; A Boutin Chemistry of Materials, 29 (2), p. 513–523, 2017. @article{Jeffroy:2017, title = {New Molecular Simulation Method to Determine Both Aluminum and Cation Location in Cationic Zeolites}, author = {M Jeffroy and C Nieto-Draghi and A Boutin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018467127&doi=10.1021%2facs.chemmater.6b03011&partnerID=40&md5=0af6ed3299d7a76f0f476eb3d12a61ea}, doi = {10.1021/acs.chemmater.6b03011}, year = {2017}, date = {2017-01-01}, journal = {Chemistry of Materials}, volume = {29}, number = {2}, pages = {513--523}, abstract = {The knowledge of aluminum distribution in zeolites is a difficult task due to limitations in experimental measurements. In the present paper, we propose a new methodology to simultaneously determined aluminum atoms distribution as well as the extraframework cation location in a given experimental structure of the framework and thus allows comparison of different synthesis routes. Aluminum mean distribution is obtained over a great number of configurations that are generated during the course of the simulations at finite temperature. The obtained aluminum atom repartition is in agreement with the experimental and model data available. The consequences of aluminum distribution on solid properties such as extraframework Na+ cation location have been analyzed and successfully compared with the available information for different zeolite topologies. The proposed methodology can be used as a powerful complementary tool for aluminum location on X-Ray or neutron experimental structure determinations. © 2016 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The knowledge of aluminum distribution in zeolites is a difficult task due to limitations in experimental measurements. In the present paper, we propose a new methodology to simultaneously determined aluminum atoms distribution as well as the extraframework cation location in a given experimental structure of the framework and thus allows comparison of different synthesis routes. Aluminum mean distribution is obtained over a great number of configurations that are generated during the course of the simulations at finite temperature. The obtained aluminum atom repartition is in agreement with the experimental and model data available. The consequences of aluminum distribution on solid properties such as extraframework Na+ cation location have been analyzed and successfully compared with the available information for different zeolite topologies. The proposed methodology can be used as a powerful complementary tool for aluminum location on X-Ray or neutron experimental structure determinations. © 2016 American Chemical Society. |
Classical Polarizable Force Field to Study Dry Charged Clays and Zeolites Article de journal S Tesson; W Louisfrema; M Salanne; A Boutin; B Rotenberg; V Marry Journal of Physical Chemistry C, 121 (18), p. 9833–9846, 2017. @article{Tesson:2017, title = {Classical Polarizable Force Field to Study Dry Charged Clays and Zeolites}, author = {S Tesson and W Louisfrema and M Salanne and A Boutin and B Rotenberg and V Marry}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020438967&doi=10.1021%2facs.jpcc.7b00270&partnerID=40&md5=b2f537a43ee14cace7b5baa0d4ca6bbd}, doi = {10.1021/acs.jpcc.7b00270}, year = {2017}, date = {2017-01-01}, journal = {Journal of Physical Chemistry C}, volume = {121}, number = {18}, pages = {9833--9846}, abstract = {We extend the classical Polarizable Ion Model (PIM) to charged clays. We focus on Na-, Ca-, Sr-, and Cs-montmorillonite with two types of structures for the octahedral sheet: trans- and cis-vacant. The full set of parameters of the force field is determined by density functional theory calculations, using maximally localized Wannier functions with a force- and dipole-optimization procedure. Simulation results for our polarizable force field are compared with the state-of-the-art nonpolarizable flexible force field named Clay Force Field (ClayFF) to assess the importance of taking polarization effects into account for the prediction of structural properties. This force field is validated by comparison with experimental data. We also demonstrate the transferability of this force field to other aluminosilicates by considering faujasite-type zeolites and comparing the cation distribution for anhydrous Na, Ca, and Sr Y (and X) faujasites predicted by the PIM model and with experimental data. © 2017 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We extend the classical Polarizable Ion Model (PIM) to charged clays. We focus on Na-, Ca-, Sr-, and Cs-montmorillonite with two types of structures for the octahedral sheet: trans- and cis-vacant. The full set of parameters of the force field is determined by density functional theory calculations, using maximally localized Wannier functions with a force- and dipole-optimization procedure. Simulation results for our polarizable force field are compared with the state-of-the-art nonpolarizable flexible force field named Clay Force Field (ClayFF) to assess the importance of taking polarization effects into account for the prediction of structural properties. This force field is validated by comparison with experimental data. We also demonstrate the transferability of this force field to other aluminosilicates by considering faujasite-type zeolites and comparing the cation distribution for anhydrous Na, Ca, and Sr Y (and X) faujasites predicted by the PIM model and with experimental data. © 2017 American Chemical Society. |
Transport and adsorption under liquid flow: the role of pore geometry Article de journal J -M Vanson; A Boutin; M Klotz; F -X Coudert Soft Matter, 13 (4), p. 875–885, 2017. @article{Vanson:2017a, title = {Transport and adsorption under liquid flow: the role of pore geometry}, author = {J -M Vanson and A Boutin and M Klotz and F -X Coudert}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85010756176&doi=10.1039%2fc6sm02414a&partnerID=40&md5=64e7bbfdf37a29044f640d6638941543}, doi = {10.1039/c6sm02414a}, year = {2017}, date = {2017-01-01}, journal = {Soft Matter}, volume = {13}, number = {4}, pages = {875--885}, abstract = {We study here the interplay between transport and adsorption in porous systems with complex geometries under fluid flow. Using a lattice Boltzmann scheme extended to take into account the adsorption at solid/fluid interfaces, we investigate the influence of pore geometry and internal surface roughness on the efficiency of fluid flow and the adsorption of molecular species inside the pore space. We show how the occurrence of roughness on pore walls acts effectively as a modification of the solid/fluid boundary conditions, introducing slippage at the interface. We then compare three common pore geometries, namely honeycomb pores, inverse opal, and materials produced by spinodal decomposition. Finally, we quantify the influence of those three geometries on fluid transport and tracer adsorption. This opens perspectives for the optimization of materials’ geometries for applications in dynamic adsorption under fluid flow. © The Royal Society of Chemistry.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We study here the interplay between transport and adsorption in porous systems with complex geometries under fluid flow. Using a lattice Boltzmann scheme extended to take into account the adsorption at solid/fluid interfaces, we investigate the influence of pore geometry and internal surface roughness on the efficiency of fluid flow and the adsorption of molecular species inside the pore space. We show how the occurrence of roughness on pore walls acts effectively as a modification of the solid/fluid boundary conditions, introducing slippage at the interface. We then compare three common pore geometries, namely honeycomb pores, inverse opal, and materials produced by spinodal decomposition. Finally, we quantify the influence of those three geometries on fluid transport and tracer adsorption. This opens perspectives for the optimization of materials’ geometries for applications in dynamic adsorption under fluid flow. © The Royal Society of Chemistry. |
Kinetic Accessibility of Porous Material Adsorption Sites Studied through the Lattice Boltzmann Method Article de journal J -M Vanson; F -X Coudert; M Klotz; A Boutin Langmuir, 33 (6), p. 1405–1411, 2017. @article{Vanson:2017, title = {Kinetic Accessibility of Porous Material Adsorption Sites Studied through the Lattice Boltzmann Method}, author = {J -M Vanson and F -X Coudert and M Klotz and A Boutin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85012885074&doi=10.1021%2facs.langmuir.6b04472&partnerID=40&md5=94b707833c0990403af7aa1b2264b31d}, doi = {10.1021/acs.langmuir.6b04472}, year = {2017}, date = {2017-01-01}, journal = {Langmuir}, volume = {33}, number = {6}, pages = {1405--1411}, abstract = {We present here a computational model based on the lattice Boltzmann scheme to investigate the accessibility of active adsorption sites in hierarchical porous materials to adsorbates in a flowing liquid. By studying the transport and adsorption of tracers after they enter the pore space of the virtual sample, we characterize their kinetics as they pass through the pore space and adsorb on the solid-liquid interface. The model is validated on simple geometries with a known analytical solution. We then use it to investigate the influence of regular grooves or disordered roughness on the walls of a slit pore geometry, looking at the impact on adsorption and transport. In particular, we highlight the importance of adsorption site accessibility, which depends on the shape and connectivity of the pore space as well as the fluid flow profile and velocity. © 2017 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present here a computational model based on the lattice Boltzmann scheme to investigate the accessibility of active adsorption sites in hierarchical porous materials to adsorbates in a flowing liquid. By studying the transport and adsorption of tracers after they enter the pore space of the virtual sample, we characterize their kinetics as they pass through the pore space and adsorb on the solid-liquid interface. The model is validated on simple geometries with a known analytical solution. We then use it to investigate the influence of regular grooves or disordered roughness on the walls of a slit pore geometry, looking at the impact on adsorption and transport. In particular, we highlight the importance of adsorption site accessibility, which depends on the shape and connectivity of the pore space as well as the fluid flow profile and velocity. © 2017 American Chemical Society. |
2016 |
Mechanism of water adsorption in the large pore form of the gallium-based MIL-53 metal-organic framework Article de journal G Weber; I Bezverkhyy; J -P Bellat; A Ballandras; G Ortiz; G Chaplais; J Patarin; F -X Coudert; A H Fuchs; A Boutin Microporous and Mesoporous Materials, 222 , p. 145–152, 2016. @article{Weber:2016, title = {Mechanism of water adsorption in the large pore form of the gallium-based MIL-53 metal-organic framework}, author = {G Weber and I Bezverkhyy and J -P Bellat and A Ballandras and G Ortiz and G Chaplais and J Patarin and F -X Coudert and A H Fuchs and A Boutin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945546147&doi=10.1016%2fj.micromeso.2015.10.003&partnerID=40&md5=a52eb07d01a83392f06ae166075ac9f9}, doi = {10.1016/j.micromeso.2015.10.003}, year = {2016}, date = {2016-01-01}, journal = {Microporous and Mesoporous Materials}, volume = {222}, pages = {145--152}, abstract = {Water adsorption in the large pore (lp-empty) form of Ga-MIL-53 was studied by TGA, DSC and in situ XRD and FTIR at 298 K. The large pore form can be stabilized at room temperature after activation under vacuum at 553 K. The isotherm of water adsorption in this large pore form (pore dimensions: 1.67 × 1.33 nm) is very similar to that measured on the narrow pore (np-empty) form (pore dimensions: 1.97 × 0.76 nm). Such a similarity is rather unusual given that the pore sizes of these two phases are very different. In order to understand the origin of this effect in situ XRD and FTIR measurements were particularly helpful. It was found that the adsorption of even small amount of water (0.05 mol per Ga atom at 0.2 hPa) in the large pore form of Ga-MIL-53 transforms ca. 50% of the solid into a narrow pore int phase, which is assumed to be present as a shell around the lp-empty core. Additional water molecules adsorbed at higher pressures do not interact with the parent lp-empty phase but with the narrow pore int phase. The phase transformations were confirmed by FTIR revealing significant band displacements in the corresponding pressure ranges. Such easy pore shrinking which occurs at very low water pressure (textless0.2 hPa) can have undesirable consequences in working conditions, as for example in separation adsorption processes, because the large pore structure of Ga-MIL-53 can be preserved only under anhydrous conditions. © 2015 Elsevier Inc.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Water adsorption in the large pore (lp-empty) form of Ga-MIL-53 was studied by TGA, DSC and in situ XRD and FTIR at 298 K. The large pore form can be stabilized at room temperature after activation under vacuum at 553 K. The isotherm of water adsorption in this large pore form (pore dimensions: 1.67 × 1.33 nm) is very similar to that measured on the narrow pore (np-empty) form (pore dimensions: 1.97 × 0.76 nm). Such a similarity is rather unusual given that the pore sizes of these two phases are very different. In order to understand the origin of this effect in situ XRD and FTIR measurements were particularly helpful. It was found that the adsorption of even small amount of water (0.05 mol per Ga atom at 0.2 hPa) in the large pore form of Ga-MIL-53 transforms ca. 50% of the solid into a narrow pore int phase, which is assumed to be present as a shell around the lp-empty core. Additional water molecules adsorbed at higher pressures do not interact with the parent lp-empty phase but with the narrow pore int phase. The phase transformations were confirmed by FTIR revealing significant band displacements in the corresponding pressure ranges. Such easy pore shrinking which occurs at very low water pressure (textless0.2 hPa) can have undesirable consequences in working conditions, as for example in separation adsorption processes, because the large pore structure of Ga-MIL-53 can be preserved only under anhydrous conditions. © 2015 Elsevier Inc. |
Cation Migration and Structural Deformations upon Dehydration of Nickel-Exchanged NaY Zeolite: A Combined Neutron Diffraction and Monte Carlo Study Article de journal W Louisfrema; J -L Paillaud; F Porcher; E Perrin; T Onfroy; P Massiani; A Boutin; B Rotenberg Journal of Physical Chemistry C, 120 (32), p. 18115–18125, 2016. @article{Louisfrema:2016, title = {Cation Migration and Structural Deformations upon Dehydration of Nickel-Exchanged NaY Zeolite: A Combined Neutron Diffraction and Monte Carlo Study}, author = {W Louisfrema and J -L Paillaud and F Porcher and E Perrin and T Onfroy and P Massiani and A Boutin and B Rotenberg}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983517960&doi=10.1021%2facs.jpcc.6b05657&partnerID=40&md5=d5dc0aa053088e7ec12d147a59adf760}, doi = {10.1021/acs.jpcc.6b05657}, year = {2016}, date = {2016-01-01}, journal = {Journal of Physical Chemistry C}, volume = {120}, number = {32}, pages = {18115--18125}, abstract = {Combining neutron diffraction and classical molecular simulations, we describe the cation migration and associated structural changes taking place in a Ni-exchanged NaY faujasite zeolite upon stepwise dehydration from room temperature up to 400 °C. The cation redistribution between sites and the related framework deformations taking place upon water removal are identified and quantified. Neutron diffraction allows monitoring the zeolite structure, the average cation location and the water content, whereas molecular modeling provides insights into the correlations between the positions of cations and water molecules. Importantly, we demonstrate that the migration of Ni2+ toward highly confined sites upon dehydration is the driving force behind deformation of the hexagonal prisms. The present work illustrates the relevance of combining these two experimental and theoretical approaches to clarify the complex interplay between cation hydration, cation location, and framework deformation. It also underlines the importance to capture the flexibility of the framework in molecular simulation of hydrated zeolite in particular when multivalent ions are involved. © 2016 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Combining neutron diffraction and classical molecular simulations, we describe the cation migration and associated structural changes taking place in a Ni-exchanged NaY faujasite zeolite upon stepwise dehydration from room temperature up to 400 °C. The cation redistribution between sites and the related framework deformations taking place upon water removal are identified and quantified. Neutron diffraction allows monitoring the zeolite structure, the average cation location and the water content, whereas molecular modeling provides insights into the correlations between the positions of cations and water molecules. Importantly, we demonstrate that the migration of Ni2+ toward highly confined sites upon dehydration is the driving force behind deformation of the hexagonal prisms. The present work illustrates the relevance of combining these two experimental and theoretical approaches to clarify the complex interplay between cation hydration, cation location, and framework deformation. It also underlines the importance to capture the flexibility of the framework in molecular simulation of hydrated zeolite in particular when multivalent ions are involved. © 2016 American Chemical Society. |
Heterometallic metal-organic frameworks of MOF-5 and UiO-66 families: Insight from computational chemistry Article de journal F Trousselet; A Archereau; A Boutin; F -X Coudert Journal of Physical Chemistry C, 120 (43), p. 24885–24894, 2016. @article{Trousselet:2016, title = {Heterometallic metal-organic frameworks of MOF-5 and UiO-66 families: Insight from computational chemistry}, author = {F Trousselet and A Archereau and A Boutin and F -X Coudert}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021680227&doi=10.1021%2facs.jpcc.6b08594&partnerID=40&md5=1d59350c3f3c291198fe5d4379de8dd5}, doi = {10.1021/acs.jpcc.6b08594}, year = {2016}, date = {2016-01-01}, journal = {Journal of Physical Chemistry C}, volume = {120}, number = {43}, pages = {24885--24894}, abstract = {We study the energetic stability and structural features of bimetallic metal-organic frameworks. Such heterometallic MOFs, which can result from partial substitutions between two types of cations, can have specific physical or chemical properties used for example in catalysis or gas adsorption. We work here to provide through computational chemistry a microscopic understanding of bimetallic MOFs and the distribution of cations within their structure. We develop a methodology based on a systematic study of possible cation distributions at all cation ratios by means of quantum chemistry calculations at the density functional theory level. We analyze the energies of the resulting bimetallic frameworks and correlate them with various disorder descriptors (functions of the bimetallic framework topology, regardless of exact atomic positions). We apply our methodology to two families of MOFs known for heterometallicity: MOF-5 (with divalent metal ions) and UiO-66 (with tetravalent metal ions). We observe that bimetallicity is overall more favorable for pairs of cations with sizes very close to each other, owing to a charge transfer mechanism inside secondary building units. For cation pairs with significant mutual size difference, metal mixing is globally less favorable, and the energy signifantly correlates with the coordination environment of linkers, determining their ability to adapt the mixing-induced strains. This effect is particularly strong in the UiO-66 family because of high cluster coordination number. © 2016 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We study the energetic stability and structural features of bimetallic metal-organic frameworks. Such heterometallic MOFs, which can result from partial substitutions between two types of cations, can have specific physical or chemical properties used for example in catalysis or gas adsorption. We work here to provide through computational chemistry a microscopic understanding of bimetallic MOFs and the distribution of cations within their structure. We develop a methodology based on a systematic study of possible cation distributions at all cation ratios by means of quantum chemistry calculations at the density functional theory level. We analyze the energies of the resulting bimetallic frameworks and correlate them with various disorder descriptors (functions of the bimetallic framework topology, regardless of exact atomic positions). We apply our methodology to two families of MOFs known for heterometallicity: MOF-5 (with divalent metal ions) and UiO-66 (with tetravalent metal ions). We observe that bimetallicity is overall more favorable for pairs of cations with sizes very close to each other, owing to a charge transfer mechanism inside secondary building units. For cation pairs with significant mutual size difference, metal mixing is globally less favorable, and the energy signifantly correlates with the coordination environment of linkers, determining their ability to adapt the mixing-induced strains. This effect is particularly strong in the UiO-66 family because of high cluster coordination number. © 2016 American Chemical Society. |
2015 |
Hydrothermal Breakdown of Flexible Metal-Organic Frameworks: A Study by First-Principles Molecular Dynamics Article de journal V Haigis; F -X Coudert; R Vuilleumier; A Boutin; A H Fuchs Journal of Physical Chemistry Letters, 6 (21), p. 4365–4370, 2015. @article{Haigis:2015, title = {Hydrothermal Breakdown of Flexible Metal-Organic Frameworks: A Study by First-Principles Molecular Dynamics}, author = {V Haigis and F -X Coudert and R Vuilleumier and A Boutin and A H Fuchs}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946822800&doi=10.1021%2facs.jpclett.5b01926&partnerID=40&md5=1ca30978fa4ef2cf6cb576e3f7b9ef21}, doi = {10.1021/acs.jpclett.5b01926}, year = {2015}, date = {2015-01-01}, journal = {Journal of Physical Chemistry Letters}, volume = {6}, number = {21}, pages = {4365--4370}, abstract = {Flexible metal-organic frameworks, also known as soft porous crystals, have been proposed for a vast number of technological applications, because they respond by large changes in structure and properties to small external stimuli, such as adsorption of guest molecules and changes in temperature or pressure. While this behavior is highly desirable in applications such as sensing and actuation, their extreme flexibility can also be synonymous with decreased stability. In particular, their performance in industrial environments is limited by a lack of stability at elevated temperatures and in the presence of water. Here, we use first-principles molecular dynamics to study the hydrothermal breakdown of soft porous crystals. Focusing on the material MIL-53(Ga), we show that the weak point of the structure is the bond between the metal center and the organic linker and elucidate the mechanism by which water lowers the activation free energy for the breakdown. This allows us to propose strategies for the synthesis of MOFs with increased heat and water stability. © 2015 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Flexible metal-organic frameworks, also known as soft porous crystals, have been proposed for a vast number of technological applications, because they respond by large changes in structure and properties to small external stimuli, such as adsorption of guest molecules and changes in temperature or pressure. While this behavior is highly desirable in applications such as sensing and actuation, their extreme flexibility can also be synonymous with decreased stability. In particular, their performance in industrial environments is limited by a lack of stability at elevated temperatures and in the presence of water. Here, we use first-principles molecular dynamics to study the hydrothermal breakdown of soft porous crystals. Focusing on the material MIL-53(Ga), we show that the weak point of the structure is the bond between the metal center and the organic linker and elucidate the mechanism by which water lowers the activation free energy for the breakdown. This allows us to propose strategies for the synthesis of MOFs with increased heat and water stability. © 2015 American Chemical Society. |
Unexpected coupling between flow and adsorption in porous media Article de journal J -M Vanson; F -X Coudert; B Rotenberg; M Levesque; C Tardivat; M Klotz; A Boutin Soft Matter, 11 (30), p. 6125–6133, 2015. @article{Vanson:2015, title = {Unexpected coupling between flow and adsorption in porous media}, author = {J -M Vanson and F -X Coudert and B Rotenberg and M Levesque and C Tardivat and M Klotz and A Boutin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937501168&doi=10.1039%2fc5sm01348h&partnerID=40&md5=27c27798ab0f7ff6c97d12fbfeea602a}, doi = {10.1039/c5sm01348h}, year = {2015}, date = {2015-01-01}, journal = {Soft Matter}, volume = {11}, number = {30}, pages = {6125--6133}, abstract = {We study the interplay between transport and adsorption in porous systems under a fluid flow, based on a lattice Boltzmann scheme extended to account for adsorption. We performed simulations on well-controlled geometries with slit and grooved pores, investigating the influence of adsorption and flow on dispersion coefficient and adsorbed density. In particular, we present a counterintuitive effect where fluid flow induces heterogeneity in the adsorbate, displacing the adsorption equilibrium towards downstream adsorption sites in grooves. We also present an improvement of the adsorption-extended lattice Boltzmann scheme by introducing the possibility for saturating Langmuir-like adsorption, while earlier work focused on linear adsorption phenomena. We then highlight the impact of this change in situations of high concentration of adsorbate. © The Royal Society of Chemistry 2015.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We study the interplay between transport and adsorption in porous systems under a fluid flow, based on a lattice Boltzmann scheme extended to account for adsorption. We performed simulations on well-controlled geometries with slit and grooved pores, investigating the influence of adsorption and flow on dispersion coefficient and adsorbed density. In particular, we present a counterintuitive effect where fluid flow induces heterogeneity in the adsorbate, displacing the adsorption equilibrium towards downstream adsorption sites in grooves. We also present an improvement of the adsorption-extended lattice Boltzmann scheme by introducing the possibility for saturating Langmuir-like adsorption, while earlier work focused on linear adsorption phenomena. We then highlight the impact of this change in situations of high concentration of adsorbate. © The Royal Society of Chemistry 2015. |
Softening upon Adsorption in Microporous Materials: A Counterintuitive Mechanical Response Article de journal F Mouhat; D Bousquet; A Boutin; L Bouëssel Du Bourg; F -X Coudert; A H Fuchs Journal of Physical Chemistry Letters, 6 (21), p. 4265–4269, 2015. @article{Mouhat:2015, title = {Softening upon Adsorption in Microporous Materials: A Counterintuitive Mechanical Response}, author = {F Mouhat and D Bousquet and A Boutin and L Bou\"{e}ssel Du Bourg and F -X Coudert and A H Fuchs}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946593609&doi=10.1021%2facs.jpclett.5b01965&partnerID=40&md5=a6ad98701fd642025fbeb18e719ad1a3}, doi = {10.1021/acs.jpclett.5b01965}, year = {2015}, date = {2015-01-01}, journal = {Journal of Physical Chemistry Letters}, volume = {6}, number = {21}, pages = {4265--4269}, abstract = {We demonstrate here that microporous materials can exhibit softening upon adsorption of guest molecules, at low to intermediate pore loading, in parallel to the pore shrinking that is well-known in this regime. This novel and counterintuitive mechanical response was observed through molecular simulations of both model pore systems (such as slit pore) and real metal-organic frameworks. It is contrary to common belief that adsorption of guest molecules necessarily leads to stiffening due to increased density, a fact that we show is the high-loading limit of a more complex behavior: a nonmonotonic softening-then-stiffening. © 2015 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We demonstrate here that microporous materials can exhibit softening upon adsorption of guest molecules, at low to intermediate pore loading, in parallel to the pore shrinking that is well-known in this regime. This novel and counterintuitive mechanical response was observed through molecular simulations of both model pore systems (such as slit pore) and real metal-organic frameworks. It is contrary to common belief that adsorption of guest molecules necessarily leads to stiffening due to increased density, a fact that we show is the high-loading limit of a more complex behavior: a nonmonotonic softening-then-stiffening. © 2015 American Chemical Society. |
2014 |
Reorientational Dynamics of Water Confined in Zeolites Article de journal Aoife C Fogarty; Francois-Xavier Coudert; A Boutin; D Laage Chemphyschem, 15 (3), p. 521-529, 2014, ISSN: 1439-4235, (WOS:000331407900015). @article{Fogarty:2014b, title = {Reorientational Dynamics of Water Confined in Zeolites}, author = {Aoife C Fogarty and Francois-Xavier Coudert and A Boutin and D Laage}, doi = {10.1002/cphc.201300928}, issn = {1439-4235}, year = {2014}, date = {2014-02-01}, journal = {Chemphyschem}, volume = {15}, number = {3}, pages = {521-529}, abstract = {We present a detailed molecular-dynamics study of water reorientation and hydrogen-bond dynamics in a strong confinement situation, within the narrow pores of an all-silica Linde type A (LTA) zeolite. Two water loadings of the zeolite are compared with the bulk case. Water dynamics are retarded in this extreme hydrophobic confinement and the slowdown is more pronounced at higher water loading. We show that water reorientation proceeds mainly by large-amplitude angular jumps, whose mechanism is similar to that determined in the bulk. The slowdown upon hydrophobic confinement arises predominantly from an excluded-volume effect on the large fraction of water molecules lying at the interface with the zeolite matrix, with an additional minor contribution coming from a structuring effect induced by the confinement.}, note = {WOS:000331407900015}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a detailed molecular-dynamics study of water reorientation and hydrogen-bond dynamics in a strong confinement situation, within the narrow pores of an all-silica Linde type A (LTA) zeolite. Two water loadings of the zeolite are compared with the bulk case. Water dynamics are retarded in this extreme hydrophobic confinement and the slowdown is more pronounced at higher water loading. We show that water reorientation proceeds mainly by large-amplitude angular jumps, whose mechanism is similar to that determined in the bulk. The slowdown upon hydrophobic confinement arises predominantly from an excluded-volume effect on the large fraction of water molecules lying at the interface with the zeolite matrix, with an additional minor contribution coming from a structuring effect induced by the confinement. |
Thermal and mechanical stability of zeolitic imidazolate frameworks polymorphs Article de journal L Bouëssel Du Bourg; A U Ortiz; A Boutin; F -X Coudert APL Materials, 2 (12), 2014. @article{BouesselDuBourg:2014, title = {Thermal and mechanical stability of zeolitic imidazolate frameworks polymorphs}, author = {L Bou\"{e}ssel Du Bourg and A U Ortiz and A Boutin and F -X Coudert}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919607978&doi=10.1063%2f1.4904818&partnerID=40&md5=e4337abaef0ab510bb01aa0f1605e6f9}, doi = {10.1063/1.4904818}, year = {2014}, date = {2014-01-01}, journal = {APL Materials}, volume = {2}, number = {12}, abstract = {Theoretical studies on the experimental feasibility of hypothetical Zeolitic Imidazolate Frameworks (ZIFs) have focused so far on relative energy of various polymorphs by energy minimization at the quantum chemical level. We present here a systematic study of stability of 18 ZIFs as a function of temperature and pressure by molecular dynamics simulations. This approach allows us to better understand the limited stability of some experimental structures upon solvent or guest removal. We also find that many of the hypothetical ZIFs proposed in the literature are not stable at room temperature. Mechanical and thermal stability criteria thus need to be considered for the prediction of new MOF structures. Finally, we predict a variety of thermal expansion behavior for ZIFs as a function of framework topology, with some materials showing large negative volume thermal expansion. © 2014 Author(s).}, keywords = {}, pubstate = {published}, tppubtype = {article} } Theoretical studies on the experimental feasibility of hypothetical Zeolitic Imidazolate Frameworks (ZIFs) have focused so far on relative energy of various polymorphs by energy minimization at the quantum chemical level. We present here a systematic study of stability of 18 ZIFs as a function of temperature and pressure by molecular dynamics simulations. This approach allows us to better understand the limited stability of some experimental structures upon solvent or guest removal. We also find that many of the hypothetical ZIFs proposed in the literature are not stable at room temperature. Mechanical and thermal stability criteria thus need to be considered for the prediction of new MOF structures. Finally, we predict a variety of thermal expansion behavior for ZIFs as a function of framework topology, with some materials showing large negative volume thermal expansion. © 2014 Author(s). |
What makes zeolitic imidazolate frameworks hydrophobic or hydrophilic? the impact of geometry and functionalization on water adsorption Article de journal A U Ortiz; A P Freitas; A Boutin; A H Fuchs; F -X Coudert Physical Chemistry Chemical Physics, 16 (21), p. 9940–9949, 2014. @article{Ortiz:2014a, title = {What makes zeolitic imidazolate frameworks hydrophobic or hydrophilic? the impact of geometry and functionalization on water adsorption}, author = {A U Ortiz and A P Freitas and A Boutin and A H Fuchs and F -X Coudert}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899784407&doi=10.1039%2fc3cp54292k&partnerID=40&md5=1160a078988025b014d51954b1f8732e}, doi = {10.1039/c3cp54292k}, year = {2014}, date = {2014-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {16}, number = {21}, pages = {9940--9949}, abstract = {We demonstrate, by means of Grand Canonical Monte Carlo simulation on different members of the ZIF family, how topology, geometry, and linker functionalization drastically affect the water adsorption properties of these materials, tweaking the ZIF materials from hydrophobic to hydrophilic. We show that adequate functionalization of the linkers allows one to tune the host-guest interactions, even featuring dual amphiphilic materials whose pore space features both hydrophobic and hydrophilic regions. Starting from an initially hydrophobic material (ZIF-8), various degrees of hydrophilicity could be obtained, with a gradual evolution from a type V adsorption isotherm in the liquid phase to a type I isotherm in the gas phase. This behavior is similar to what was described earlier in families of hydrophobic all-silica zeolites, with hydrophilic "defects" of various strength, such as silanol nests or the presence of extra-framework cations. © the Partner Organisations 2014.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We demonstrate, by means of Grand Canonical Monte Carlo simulation on different members of the ZIF family, how topology, geometry, and linker functionalization drastically affect the water adsorption properties of these materials, tweaking the ZIF materials from hydrophobic to hydrophilic. We show that adequate functionalization of the linkers allows one to tune the host-guest interactions, even featuring dual amphiphilic materials whose pore space features both hydrophobic and hydrophilic regions. Starting from an initially hydrophobic material (ZIF-8), various degrees of hydrophilicity could be obtained, with a gradual evolution from a type V adsorption isotherm in the liquid phase to a type I isotherm in the gas phase. This behavior is similar to what was described earlier in families of hydrophobic all-silica zeolites, with hydrophilic "defects" of various strength, such as silanol nests or the presence of extra-framework cations. © the Partner Organisations 2014. |
A thermodynamic description of the adsorption-induced structural transitions in flexible MIL-53 metal-organic framework Article de journal F -X Coudert; A Boutin; A H Fuchs Molecular Physics, 112 (9-10), p. 1257–1261, 2014. @article{Coudert:2014, title = {A thermodynamic description of the adsorption-induced structural transitions in flexible MIL-53 metal-organic framework}, author = {F -X Coudert and A Boutin and A H Fuchs}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901228951&doi=10.1080%2f00268976.2014.889325&partnerID=40&md5=a904704b473ad68285cee6634122b7ed}, doi = {10.1080/00268976.2014.889325}, year = {2014}, date = {2014-01-01}, journal = {Molecular Physics}, volume = {112}, number = {9-10}, pages = {1257--1261}, abstract = {We briefly review the concept of temperature-loading phase diagram that we derived from an osmotic statistical ensemble analysis of the adsorption-induced structural transitions observed in the MIL-53 family of metal-organic framework nanoporous materials. We highlight the generic nature of this diagram and comment on the occurrence of breathing transitions depending on the guest fluid, the framework functionalisation and the nature of the metal centre. © 2014 Taylor & Francis.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We briefly review the concept of temperature-loading phase diagram that we derived from an osmotic statistical ensemble analysis of the adsorption-induced structural transitions observed in the MIL-53 family of metal-organic framework nanoporous materials. We highlight the generic nature of this diagram and comment on the occurrence of breathing transitions depending on the guest fluid, the framework functionalisation and the nature of the metal centre. © 2014 Taylor & Francis. |
Challenges in first-principles NPT molecular dynamics of soft porous crystals: A case study on MIL-53(Ga) Article de journal V Haigis; Y Belkhodja; F -X Coudert; R Vuilleumier; A Boutin Journal of Chemical Physics, 141 (6), 2014. @article{Haigis:2014, title = {Challenges in first-principles NPT molecular dynamics of soft porous crystals: A case study on MIL-53(Ga)}, author = {V Haigis and Y Belkhodja and F -X Coudert and R Vuilleumier and A Boutin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906216632&doi=10.1063%2f1.4891578&partnerID=40&md5=ec0fa9a19fe3fa728216508d915c19a2}, doi = {10.1063/1.4891578}, year = {2014}, date = {2014-01-01}, journal = {Journal of Chemical Physics}, volume = {141}, number = {6}, abstract = {Soft porous crystals present a challenge to molecular dynamics simulations with flexible size and shape of the simulation cell (i.e., in the NPT ensemble), since their framework responds very sensitively to small external stimuli. Hence, all interactions have to be described very accurately in order to obtain correct equilibrium structures. Here, we report a methodological study on the nanoporous metal-organic framework MIL-53(Ga), which undergoes a large-amplitude transition between a narrow- and a large-pore phase upon a change in temperature. Since this system has not been investigated by density functional theory (DFT)-based NPT simulations so far, we carefully check the convergence of the stress tensor with respect to computational parameters. Furthermore, we demonstrate the importance of dispersion interactions and test two different ways of incorporating them into the DFT framework. As a result, we propose two computational schemes which describe accurately the narrow- and the large-pore phase of the material, respectively. These schemes can be used in future work on the delicate interplay between adsorption in the nanopores and structural flexibility of the host material. © 2014 AIP Publishing LLC.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Soft porous crystals present a challenge to molecular dynamics simulations with flexible size and shape of the simulation cell (i.e., in the NPT ensemble), since their framework responds very sensitively to small external stimuli. Hence, all interactions have to be described very accurately in order to obtain correct equilibrium structures. Here, we report a methodological study on the nanoporous metal-organic framework MIL-53(Ga), which undergoes a large-amplitude transition between a narrow- and a large-pore phase upon a change in temperature. Since this system has not been investigated by density functional theory (DFT)-based NPT simulations so far, we carefully check the convergence of the stress tensor with respect to computational parameters. Furthermore, we demonstrate the importance of dispersion interactions and test two different ways of incorporating them into the DFT framework. As a result, we propose two computational schemes which describe accurately the narrow- and the large-pore phase of the material, respectively. These schemes can be used in future work on the delicate interplay between adsorption in the nanopores and structural flexibility of the host material. © 2014 AIP Publishing LLC. |
Water adsorption in flexible gallium-based MIL-53 metal-organic framework Article de journal F -X Coudert; A U Ortiz; V Haigis; D Bousquet; A H Fuchs; A Ballandras; G Weber; I Bezverkhyy; N Geoffroy; J -P Bellat; G Ortiz; G Chaplais; J Patarin; A Boutin Journal of Physical Chemistry C, 118 (10), p. 5397–5405, 2014. @article{Coudert:2014a, title = {Water adsorption in flexible gallium-based MIL-53 metal-organic framework}, author = {F -X Coudert and A U Ortiz and V Haigis and D Bousquet and A H Fuchs and A Ballandras and G Weber and I Bezverkhyy and N Geoffroy and J -P Bellat and G Ortiz and G Chaplais and J Patarin and A Boutin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896346306&doi=10.1021%2fjp412433a&partnerID=40&md5=3446b29323bd4a444add6e88bea79bad}, doi = {10.1021/jp412433a}, year = {2014}, date = {2014-01-01}, journal = {Journal of Physical Chemistry C}, volume = {118}, number = {10}, pages = {5397--5405}, abstract = {Understanding the adsorption of water in metal-organic frameworks (MOF), and particularly in soft porous crystals, is a crucial prerequisite before considering MOFs for industrial applications. We report here a joint experimental and theoretical study on the behavior of a gallium-based breathing MOF, Ga-MIL-53, upon water adsorption. By looking at the energetics and thermodynamics of Ga-MIL-53, we demonstrate why it behaves differently from its sibling Al-MIL-53, showing a different phase at room temperature (a nonporous phase) and the presence of a hydrated narrow-pore structure at gas saturation pressure. Moreover, we present a complete water vapor pressure vs temperature phase diagram of Ga-MIL-53 upon water adsorption. © 2014 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Understanding the adsorption of water in metal-organic frameworks (MOF), and particularly in soft porous crystals, is a crucial prerequisite before considering MOFs for industrial applications. We report here a joint experimental and theoretical study on the behavior of a gallium-based breathing MOF, Ga-MIL-53, upon water adsorption. By looking at the energetics and thermodynamics of Ga-MIL-53, we demonstrate why it behaves differently from its sibling Al-MIL-53, showing a different phase at room temperature (a nonporous phase) and the presence of a hydrated narrow-pore structure at gas saturation pressure. Moreover, we present a complete water vapor pressure vs temperature phase diagram of Ga-MIL-53 upon water adsorption. © 2014 American Chemical Society. |
Molecular simulation of zeolite flexibility Article de journal M Jeffroy; C Nieto-Draghi; A Boutin Molecular Simulation, 40 (1-3), p. 6–15, 2014. @article{Jeffroy:2014, title = {Molecular simulation of zeolite flexibility}, author = {M Jeffroy and C Nieto-Draghi and A Boutin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896755630&doi=10.1080%2f08927022.2013.840898&partnerID=40&md5=50415e995710aefa00884ca84a9960e2}, doi = {10.1080/08927022.2013.840898}, year = {2014}, date = {2014-01-01}, journal = {Molecular Simulation}, volume = {40}, number = {1-3}, pages = {6--15}, abstract = {We present a transferable force field able to model the structure of zeolites when different cation types are considered. Based on simple functional forms and interactions, it can be easily implemented in most common molecular simulation codes. The optimised force field is validated on structural properties (lattice parameters and Si-O-Al angles) for a large variety of zeolites, including faujasites of different Si/Al ratio and different extra-framework cation types (Li+, Na+, K+, Mg2+, Ca2+ and Co2+). The transferability of the force field was successfully tested on zeolites of different topologies such as FAU, LTA, MFI, FER and TON. The predictive capabilities of the potential were tested on structural deformations of alkaline earth Na, Co-X faujasites with different ion-exchange ratios. © 2014 © 2013 Taylor & Francis.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a transferable force field able to model the structure of zeolites when different cation types are considered. Based on simple functional forms and interactions, it can be easily implemented in most common molecular simulation codes. The optimised force field is validated on structural properties (lattice parameters and Si-O-Al angles) for a large variety of zeolites, including faujasites of different Si/Al ratio and different extra-framework cation types (Li+, Na+, K+, Mg2+, Ca2+ and Co2+). The transferability of the force field was successfully tested on zeolites of different topologies such as FAU, LTA, MFI, FER and TON. The predictive capabilities of the potential were tested on structural deformations of alkaline earth Na, Co-X faujasites with different ion-exchange ratios. © 2014 © 2013 Taylor & Francis. |
Prediction of flexibility of metal-organic frameworks CAU-13 and NOTT-300 by first principles molecular simulations Article de journal A U Ortiz; A Boutin; F -X Coudert Chemical Communications, 50 (44), p. 5867–5870, 2014. @article{Ortiz:2014, title = {Prediction of flexibility of metal-organic frameworks CAU-13 and NOTT-300 by first principles molecular simulations}, author = {A U Ortiz and A Boutin and F -X Coudert}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899841926&doi=10.1039%2fc4cc00734d&partnerID=40&md5=b6d75dc4e7c1968af3403d8c919a71f6}, doi = {10.1039/c4cc00734d}, year = {2014}, date = {2014-01-01}, journal = {Chemical Communications}, volume = {50}, number = {44}, pages = {5867--5870}, abstract = {Based on first principles calculations, we predict and characterize the flexibility of two aluminium-based Metal-Organic Frameworks (MOFs), CAU-13 and NOTT-300. Both materials have a wine rack topology similar to that of MIL-53(Al), the archetypal breathing MOF, yet their flexibility has not been demonstrated so far. This journal is © the Partner Organisations 2014.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Based on first principles calculations, we predict and characterize the flexibility of two aluminium-based Metal-Organic Frameworks (MOFs), CAU-13 and NOTT-300. Both materials have a wine rack topology similar to that of MIL-53(Al), the archetypal breathing MOF, yet their flexibility has not been demonstrated so far. This journal is © the Partner Organisations 2014. |
2013 |
Temperature-induced structural transitions in the gallium-based MIL-53 metal-organic framework Article de journal A Boutin; D Bousquet; A U Ortiz; F -X Coudert; A H Fuchs; A Ballandras; G Weber; I Bezverkhyy; J -P Bellat; G Ortiz; G Chaplais; J -L Paillaud; C Marichal; H Nouali; J Patarin Journal of Physical Chemistry C, 117 (16), p. 8180–8188, 2013. @article{Boutin:2013, title = {Temperature-induced structural transitions in the gallium-based MIL-53 metal-organic framework}, author = {A Boutin and D Bousquet and A U Ortiz and F -X Coudert and A H Fuchs and A Ballandras and G Weber and I Bezverkhyy and J -P Bellat and G Ortiz and G Chaplais and J -L Paillaud and C Marichal and H Nouali and J Patarin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876846121&doi=10.1021%2fjp312179e&partnerID=40&md5=4744e3cc2a0005c3ab192b717e761862}, doi = {10.1021/jp312179e}, year = {2013}, date = {2013-01-01}, journal = {Journal of Physical Chemistry C}, volume = {117}, number = {16}, pages = {8180--8188}, abstract = {We report a structural and thermodynamic investigation of the phase behavior of Ga(OH,F)-MIL-53, a gallium-based metal-organic framework (MOF) having the MIL-53 topology containing 0.7 wt % fluorine bonded to the metal. Despite some small structural differences, especially for the hydrated form, the overall physical chemistry behavior of Ga(OH,F)-MIL-53 is very similar to standard fluorine free Ga-MIL-53 material. A combination of in situ X-ray diffraction, in situ Fourier transform infrared spectroscopy, differential scanning calorimetry, and heat capacity measurements allowed us to establish that Ga(OH,F)-MIL-53 under vacuum (i.e., the empty material) exhibits two stable phases: A nonporous narrow-pore (np) phase favored at low temperature and a large-pore (lp) phase favored at high temperature, accompanied by a huge hysteresis effect. Structure determination of the hydrated material Ga(OH,F)-MIL-53-np-H2O obtained after synthesis, activation, and rehydration was also performed. Density functional theory calculations show that it is not a stable structure of Ga(OH,F)-MIL-53 in the absence of adsorbed water molecules. Instead, this hydrated structure is a swollen variant of the np phase, where the flexible framework has expanded to accommodate water molecules. © 2013 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report a structural and thermodynamic investigation of the phase behavior of Ga(OH,F)-MIL-53, a gallium-based metal-organic framework (MOF) having the MIL-53 topology containing 0.7 wt % fluorine bonded to the metal. Despite some small structural differences, especially for the hydrated form, the overall physical chemistry behavior of Ga(OH,F)-MIL-53 is very similar to standard fluorine free Ga-MIL-53 material. A combination of in situ X-ray diffraction, in situ Fourier transform infrared spectroscopy, differential scanning calorimetry, and heat capacity measurements allowed us to establish that Ga(OH,F)-MIL-53 under vacuum (i.e., the empty material) exhibits two stable phases: A nonporous narrow-pore (np) phase favored at low temperature and a large-pore (lp) phase favored at high temperature, accompanied by a huge hysteresis effect. Structure determination of the hydrated material Ga(OH,F)-MIL-53-np-H2O obtained after synthesis, activation, and rehydration was also performed. Density functional theory calculations show that it is not a stable structure of Ga(OH,F)-MIL-53 in the absence of adsorbed water molecules. Instead, this hydrated structure is a swollen variant of the np phase, where the flexible framework has expanded to accommodate water molecules. © 2013 American Chemical Society. |
Adsorption induced transitions in soft porous crystals: An osmotic potential approach to multistability and intermediate structures Article de journal D Bousquet; F -X Coudert; A G J Fossati; A V Neimark; A H Fuchs; A Boutin Journal of Chemical Physics, 138 (17), 2013. @article{Bousquet:2013, title = {Adsorption induced transitions in soft porous crystals: An osmotic potential approach to multistability and intermediate structures}, author = {D Bousquet and F -X Coudert and A G J Fossati and A V Neimark and A H Fuchs and A Boutin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877763222&doi=10.1063%2f1.4802888&partnerID=40&md5=7e18e49c055d9e02e4ce984b29d554d8}, doi = {10.1063/1.4802888}, year = {2013}, date = {2013-01-01}, journal = {Journal of Chemical Physics}, volume = {138}, number = {17}, abstract = {Soft porous crystals are flexible metal-organic frameworks that respond to physical stimuli (temperature, pressure, and gas adsorption) by large changes in their structure and unit cell volume. We propose here a thermodynamic treatment, based on the osmotic ensemble, of the interplay between guest adsorption and host deformation, where the bare host material can undergo elastic deformation, as well as structural transitions between metastable phases in the case of a multistable material. We show that in addition to structural transitions between metastable phases of bistable or multistable host frameworks, a new guest-stabilized host phase can be created when the size of the adsorbate is larger than the empty materials pore size. We then confront the findings of our approach with experimental data for systems exhibiting phenomena such as gate opening and breathing. © 2013 AIP Publishing LLC.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Soft porous crystals are flexible metal-organic frameworks that respond to physical stimuli (temperature, pressure, and gas adsorption) by large changes in their structure and unit cell volume. We propose here a thermodynamic treatment, based on the osmotic ensemble, of the interplay between guest adsorption and host deformation, where the bare host material can undergo elastic deformation, as well as structural transitions between metastable phases in the case of a multistable material. We show that in addition to structural transitions between metastable phases of bistable or multistable host frameworks, a new guest-stabilized host phase can be created when the size of the adsorbate is larger than the empty materials pore size. We then confront the findings of our approach with experimental data for systems exhibiting phenomena such as gate opening and breathing. © 2013 AIP Publishing LLC. |
Metal-organic frameworks with wine-rack motif: What determines their flexibility and elastic properties? Article de journal A U Ortiz; A Boutin; A H Fuchs; F -X Coudert Journal of Chemical Physics, 138 (17), 2013. @article{Ortiz:2013a, title = {Metal-organic frameworks with wine-rack motif: What determines their flexibility and elastic properties?}, author = {A U Ortiz and A Boutin and A H Fuchs and F -X Coudert}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877783026&doi=10.1063%2f1.4802770&partnerID=40&md5=25fd00c04c54491bc9b1bb2abdb42f44}, doi = {10.1063/1.4802770}, year = {2013}, date = {2013-01-01}, journal = {Journal of Chemical Physics}, volume = {138}, number = {17}, abstract = {We present here a framework for the analysis of the full tensors of second-order elastic constants of metal-organic frameworks, which can be obtained by ab initio calculations. We describe the various mechanical properties one can derive from such tensors: directional Youngs modulus, shear modulus, Poisson ratio, and linear compressibility. We then apply this methodology to four different metal-organic frameworks displaying a wine-rack structure: MIL-53(Al), MIL-47, MIL-122(In), and MIL-140A. From these results, we shed some light into the link between mechanical properties, geometric shape, and compliance of the framework of these porous solids. We conclude by proposing a simple criterion to assess the framework compliance, based on the lowest eigenvalue of its second-order elastic tensor. © 2013 AIP Publishing LLC.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present here a framework for the analysis of the full tensors of second-order elastic constants of metal-organic frameworks, which can be obtained by ab initio calculations. We describe the various mechanical properties one can derive from such tensors: directional Youngs modulus, shear modulus, Poisson ratio, and linear compressibility. We then apply this methodology to four different metal-organic frameworks displaying a wine-rack structure: MIL-53(Al), MIL-47, MIL-122(In), and MIL-140A. From these results, we shed some light into the link between mechanical properties, geometric shape, and compliance of the framework of these porous solids. We conclude by proposing a simple criterion to assess the framework compliance, based on the lowest eigenvalue of its second-order elastic tensor. © 2013 AIP Publishing LLC. |
Investigating the pressure-induced amorphization of zeolitic imidazolate framework ZIF-8: Mechanical instability due to shear mode softening Article de journal A U Ortiz; A Boutin; A H Fuchs; F -X Coudert Journal of Physical Chemistry Letters, 4 (11), p. 1861–1865, 2013. @article{Ortiz:2013, title = {Investigating the pressure-induced amorphization of zeolitic imidazolate framework ZIF-8: Mechanical instability due to shear mode softening}, author = {A U Ortiz and A Boutin and A H Fuchs and F -X Coudert}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879244144&doi=10.1021%2fjz400880p&partnerID=40&md5=00d9f445cc597492b3f8a44a29915574}, doi = {10.1021/jz400880p}, year = {2013}, date = {2013-01-01}, journal = {Journal of Physical Chemistry Letters}, volume = {4}, number = {11}, pages = {1861--1865}, abstract = {We provide the first molecular dynamics study of the mechanical instability that is the cause of pressure-induced amorphization of zeolitic imidazolate framework ZIF-8. By measuring the elastic constants of ZIF-8 up to the amorphization pressure, we show that the crystal-to-amorphous transition is triggered by the mechanical instability of ZIF-8 under compression, due to shear mode softening of the material. No similar softening was observed under temperature increase, explaining the absence of temperature-induced amorphization in ZIF-8. We also demonstrate the large impact of the presence of adsorbate in the pores on the mechanical stability and compressibility of the framework, increasing its shear stability. This first molecular dynamics study of ZIF mechanical properties under variations of pressure, temperature, and pore filling opens the way to a more comprehensive understanding of their mechanical stability, structural transitions, and amorphization. © 2013 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We provide the first molecular dynamics study of the mechanical instability that is the cause of pressure-induced amorphization of zeolitic imidazolate framework ZIF-8. By measuring the elastic constants of ZIF-8 up to the amorphization pressure, we show that the crystal-to-amorphous transition is triggered by the mechanical instability of ZIF-8 under compression, due to shear mode softening of the material. No similar softening was observed under temperature increase, explaining the absence of temperature-induced amorphization in ZIF-8. We also demonstrate the large impact of the presence of adsorbate in the pores on the mechanical stability and compressibility of the framework, increasing its shear stability. This first molecular dynamics study of ZIF mechanical properties under variations of pressure, temperature, and pore filling opens the way to a more comprehensive understanding of their mechanical stability, structural transitions, and amorphization. © 2013 American Chemical Society. |
Investigation of structure and dynamics of the hydrated metal-organic framework MIL-53(Cr) using first-principles molecular dynamics Article de journal V Haigis; F -X Coudert; R Vuilleumier; A Boutin Physical Chemistry Chemical Physics, 15 (43), p. 19049–19056, 2013. @article{Haigis:2013, title = {Investigation of structure and dynamics of the hydrated metal-organic framework MIL-53(Cr) using first-principles molecular dynamics}, author = {V Haigis and F -X Coudert and R Vuilleumier and A Boutin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886894083&doi=10.1039%2fc3cp53126k&partnerID=40&md5=71f35bfbf47a044dc1b725bc8d6d6493}, doi = {10.1039/c3cp53126k}, year = {2013}, date = {2013-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {15}, number = {43}, pages = {19049--19056}, abstract = {The hydration behavior of metal-organic frameworks (MOFs) is of interest both from a practical and from a fundamental point of view: it is linked, on the one hand, to the hydrothermal stability (or instability) of the nanoporous material, which might limit its use in technological applications. On the other hand, it sheds light on the behavior of water in a strongly confined environment. Here, we use first-principles molecular dynamics (MD) to investigate two hydrated phases of the flexible MOF MIL-53(Cr), which adopts a narrow- or a large-pore form, depending on the water loading. Structure and dynamics of the two phases are thoroughly analyzed and compared, with a focus on the hydroxyl group of MIL-53(Cr) and the water molecules in the nanopores. Furthermore, the behavior of the confined water is compared to that of bulk water. Whereas in the narrow-pore form, water is adsorbed at specific crystalline sites, it shows a more disordered, bulk-like structure in the large-pore form. However, reorientation dynamics of water molecules in the latter is considerably slowed down with respect to bulk water, which highlights the confinement effect of the nanoporous framework. © 2013 the Owner Societies.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The hydration behavior of metal-organic frameworks (MOFs) is of interest both from a practical and from a fundamental point of view: it is linked, on the one hand, to the hydrothermal stability (or instability) of the nanoporous material, which might limit its use in technological applications. On the other hand, it sheds light on the behavior of water in a strongly confined environment. Here, we use first-principles molecular dynamics (MD) to investigate two hydrated phases of the flexible MOF MIL-53(Cr), which adopts a narrow- or a large-pore form, depending on the water loading. Structure and dynamics of the two phases are thoroughly analyzed and compared, with a focus on the hydroxyl group of MIL-53(Cr) and the water molecules in the nanopores. Furthermore, the behavior of the confined water is compared to that of bulk water. Whereas in the narrow-pore form, water is adsorbed at specific crystalline sites, it shows a more disordered, bulk-like structure in the large-pore form. However, reorientation dynamics of water molecules in the latter is considerably slowed down with respect to bulk water, which highlights the confinement effect of the nanoporous framework. © 2013 the Owner Societies. |
Adsorption deformation and structural transitions in metal-organic frameworks: From the unit cell to the crystal Article de journal F -X Coudert; A Boutin; A H Fuchs; A V Neimark Journal of Physical Chemistry Letters, 4 (19), p. 3198–3205, 2013. @article{Coudert:2013, title = {Adsorption deformation and structural transitions in metal-organic frameworks: From the unit cell to the crystal}, author = {F -X Coudert and A Boutin and A H Fuchs and A V Neimark}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885152274&doi=10.1021%2fjz4013849&partnerID=40&md5=ed9b4dadc96c53b18981f8ac8f022fa5}, doi = {10.1021/jz4013849}, year = {2013}, date = {2013-01-01}, journal = {Journal of Physical Chemistry Letters}, volume = {4}, number = {19}, pages = {3198--3205}, abstract = {Much attention has recently been focused on soft porous crystals, a fascinating subclass of metal-organic frameworks that behave in a remarkable stimuli-responsive fashion, presenting structural changes of large amplitude in response to guest adsorption, mechanical pressure, or variations in temperature. In this Perspective, we summarize the recently developed thermodynamic and mechanical theoretical models for the understanding of these materials, based on the concepts of adsorption stress and osmotic thermodynamic ensemble. We show how these models provide a coherent picture of adsorption-induced deformation and structural transitions in flexible metal-organic frameworks, all the way from the length scale of the unit cell to that of the full crystal. In particular, we highlight the new perspectives opened by these models, as well as some of the important open questions in the field. © 2013 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Much attention has recently been focused on soft porous crystals, a fascinating subclass of metal-organic frameworks that behave in a remarkable stimuli-responsive fashion, presenting structural changes of large amplitude in response to guest adsorption, mechanical pressure, or variations in temperature. In this Perspective, we summarize the recently developed thermodynamic and mechanical theoretical models for the understanding of these materials, based on the concepts of adsorption stress and osmotic thermodynamic ensemble. We show how these models provide a coherent picture of adsorption-induced deformation and structural transitions in flexible metal-organic frameworks, all the way from the length scale of the unit cell to that of the full crystal. In particular, we highlight the new perspectives opened by these models, as well as some of the important open questions in the field. © 2013 American Chemical Society. |
2012 |
Extension of Marcus picture for electron transfer reactions with large solvation changes Article de journal R Vuilleumier; K A Tay; G Jeanmairet; D Borgis; A Boutin Journal of the American Chemical Society, 134 (4), p. 2067–2074, 2012. @article{Vuilleumier:2012, title = {Extension of Marcus picture for electron transfer reactions with large solvation changes}, author = {R Vuilleumier and K A Tay and G Jeanmairet and D Borgis and A Boutin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856424997&doi=10.1021%2fja2069104&partnerID=40&md5=dad87e02b14fa27cc4d1c79a79892e4b}, doi = {10.1021/ja2069104}, year = {2012}, date = {2012-01-01}, journal = {Journal of the American Chemical Society}, volume = {134}, number = {4}, pages = {2067--2074}, abstract = {The standard Marcus theory of charge transfer reaction in solution, relying on a Gaussian solvation picture, or, equivalently, on a linear response approximation, and involving two parameters, the reorganization energy and the reaction free-energy parameter, may fail when the solvation has a different character in the reactant and product state. We propose two complementary theoretical extensions of Marcus theory applying to those cases, based either on a two-Gaussian-states solvation picture, or on a non-Gaussian solvation picture. As illustration, we show that such situations arise even for simple half oxido-reduction reactions involving the Cu +/Cu 2+ or Ag 0/Ag + couples, for which electron transfer free-energy surfaces have been generated using first-principle molecular dynamics simulations. The two theoretical extensions are shown to exhibit the correct nonlinear response behavior and to reproduce the simulation results quantitatively, whereas a simple one-Gaussian-state Marcus description breaks down. © 2011 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The standard Marcus theory of charge transfer reaction in solution, relying on a Gaussian solvation picture, or, equivalently, on a linear response approximation, and involving two parameters, the reorganization energy and the reaction free-energy parameter, may fail when the solvation has a different character in the reactant and product state. We propose two complementary theoretical extensions of Marcus theory applying to those cases, based either on a two-Gaussian-states solvation picture, or on a non-Gaussian solvation picture. As illustration, we show that such situations arise even for simple half oxido-reduction reactions involving the Cu +/Cu 2+ or Ag 0/Ag + couples, for which electron transfer free-energy surfaces have been generated using first-principle molecular dynamics simulations. The two theoretical extensions are shown to exhibit the correct nonlinear response behavior and to reproduce the simulation results quantitatively, whereas a simple one-Gaussian-state Marcus description breaks down. © 2011 American Chemical Society. |
Anisotropic elastic properties of flexible metal-organic frameworks: How soft are soft porous crystals? Article de journal A U Ortiz; A Boutin; A H Fuchs; F -X Coudert Physical Review Letters, 109 (19), 2012. @article{Ortiz:2012, title = {Anisotropic elastic properties of flexible metal-organic frameworks: How soft are soft porous crystals?}, author = {A U Ortiz and A Boutin and A H Fuchs and F -X Coudert}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869053381&doi=10.1103%2fPhysRevLett.109.195502&partnerID=40&md5=c1106eaa6e76d05937721e76a4a962ff}, doi = {10.1103/PhysRevLett.109.195502}, year = {2012}, date = {2012-01-01}, journal = {Physical Review Letters}, volume = {109}, number = {19}, abstract = {We performed ab initio calculations of the elastic constants of five flexible metal-organic frameworks (MOFs): MIL-53(Al), MIL-53(Ga), MIL-47, and the square and lozenge structures of DMOF-1. Tensorial analysis of the elastic constants reveals a highly anisotropic elastic behavior, some deformation directions exhibiting very low Young's modulus and shear modulus. This anisotropy can reach a 4001 ratio between the most rigid and weakest directions, in stark contrast to the case of nonflexible MOFs such as MOF-5 and ZIF-8. In addition, we show that flexible MOFs can display extremely large negative linear compressibility. These results uncover the microscopic roots of stimuli-induced structural transitions in flexible MOFs, by linking the local elastic behavior of the material and its multistability. © 2012 American Physical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We performed ab initio calculations of the elastic constants of five flexible metal-organic frameworks (MOFs): MIL-53(Al), MIL-53(Ga), MIL-47, and the square and lozenge structures of DMOF-1. Tensorial analysis of the elastic constants reveals a highly anisotropic elastic behavior, some deformation directions exhibiting very low Young's modulus and shear modulus. This anisotropy can reach a 4001 ratio between the most rigid and weakest directions, in stark contrast to the case of nonflexible MOFs such as MOF-5 and ZIF-8. In addition, we show that flexible MOFs can display extremely large negative linear compressibility. These results uncover the microscopic roots of stimuli-induced structural transitions in flexible MOFs, by linking the local elastic behavior of the material and its multistability. © 2012 American Physical Society. |