ORCID Profile
0000-0001-5318-3910
Current Organisations
École Normale Supérieure / PSL University
,
Chimie ParisTech, PSL University
,
Centre National de la Recherche Scientifique
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Publications
Defects in metal–organic frameworks: a compromise between adsorption and stability?
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5DT04330A
Abstract: Defect engineering has arisen as a promising approach to tune and optimise the adsorptive performance of metal–organic frameworks.
The Role of Temperature and Adsorbate on Negative Gas Adsorption in the Mesoporous Metal-Organic Framework DUT-49
Publisher: American Chemical Society (ACS)
Date: 28-01-2020
DOI: 10.26434/CHEMRXIV.11733408
Abstract: In this contribution, we present an extensive investigation of adsorption of a range of different gases at various temperatures in DUT-49, a metal-organic framework which features a negative gas adsorption (NGA) transition. Adsorption experiments at temperatures ranging from 21 to 308 K, were used to identify, for each guest, a critical temperature range in which NGA occurs. The experimental results were complemented by molecular simulations that rationalize the absence of NGA at elevated temperatures and the non-monotonic behavior observed upon temperature decrease.
Predicting the Mechanical Properties of Zeolite Frameworks by Machine Learning
Publisher: American Chemical Society (ACS)
Date: 29-08-2017
DOI: 10.26434/CHEMRXIV.5349151.V1
Abstract: We show here that machine learning is a powerful new tool for predicting the elastic response of zeolites. We built our machine learning approach relying on geometric features only, which are related to local geometry, structure and porosity of a zeolite, to predict bulk and shear moduli of zeolites with an accuracy exceeding that of force field approaches. The development of this model has illustrated clear correlations between characteristic features of a zeolite and elastic moduli providing exceptional insight into the mechanics of zeolitic frameworks. Finally, we employ this methodology to predict the elastic response of 590 448 hypothetical zeolites, and the results of this massive database provide clear evidence to stability trends in porous materials.
Engineering Micromechanics of Soft Porous Crystals for Negative Gas Adsorption
Publisher: American Chemical Society (ACS)
Date: 08-07-2020
DOI: 10.26434/CHEMRXIV.12619064
Abstract: Framework materials at the molecular level, such as metal-organic frameworks (MOF), were recently found to exhibit exotic and counterintuitive micromechanical properties. Stimulated by host-guest interactions, these so-called soft porous crystals can display counterintuitive adsorption phenomena such as negative gas adsorption (NGA). NGA materials are bistable frameworks where the occurrence of a metastable overloaded state leads to pressure lification upon a sudden framework contraction. How can we control activation barriers and energetics via functionalization of the molecular building blocks that dictate the frameworks’ 30 mechanical response? In this work we tune the elastic and inelastic properties of building blocks at the 31 molecular level and analyze the mechanical response of the resulting frameworks. From a set of 11 frameworks, we demonstrate that widening of the backbone increases elasticity, while elongation of the building blocks results in a decrease in critical yield stress of buckling. We further functionalize the backbone by incorporation of sp3 hybridized carbon atoms to soften the molecular building blocks, or stiffen them with sp2 and sp carbons. Computational modeling shows how these modifications of the building blocks tune the 36 activation barriers within the energy landscape of the guest-free bistable frameworks. Only frameworks with free energy barriers in the range of 800 to 1100 kJ mol–1 37 per unit cell, and moderate yield stress of 0.6 to 38 1.2 nN for single ligand buckling, exhibit adsorption-induced contraction and negative gas adsorption. Advanced experimental in situ methodologies give detailed insights into the structural transitions and the adsorption behavior. The new framework DUT-160 shows the highest magnitude of NGA ever observed for nitrogen adsorption at 77 K. Our computational and experimental analysis of the energetics and mechanical response functions of porous frameworks is an important step towards tuning activation barriers in dynamic framework materials and provides critical design principles for molecular building blocks leading to pressure lifying materials br
Conformational chiral polymorphism in cis-bis-triphenylphosphine complexes of transition metals
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8CE00337H
Abstract: Analysis of conformation polymorphism in cis -bis-triphenylphosphine complexes points to the importance of coordination numbers and homochirality of PPh 3 ligands.
Origins of Negative Gas Adsorption
Publisher: Elsevier BV
Date: 12-2016
Predicting the Mechanical Properties of Zeolite Frameworks by Machine Learning
Publisher: American Chemical Society (ACS)
Date: 25-08-2017
Microscopic Mechanism of Chiral Induction in a Metal–Organic Framework
Publisher: American Chemical Society (ACS)
Date: 09-05-2016
DOI: 10.1021/JACS.6B02781
Abstract: The recently reported process of chiral induction in a metal-organic framework (MOF) by nonchiral guest adsorption, demonstrated on the prototypical MOF-5, may revolutionize the production of MOFs for enantioselective separation and catalysis. Herein, we describe an investigation employing multiscale molecular simulation to discover the microscopic mechanism of chiral induction and investigate the stability of the resulting framework. Our results explain how the molecular size and chemical nature of N-methyl-2-pyrrolidone (NMP) give rise to the chiral transformation in MOF-5, whereas it cannot occur for other guest molecules, such as N,N-dimethylformamide (DMF). Moreover, we show that the guest-free CMOF-5 structure is energetically unstable, with either the achiral conventional structure or a closed pore structure preferred, demonstrating that chirality will not be retained upon activation of CMOF-5. While this limits the usability of chiral induction in MOFs, our study opens new avenues for the use of other guest molecules and provides microscopic insight into this unexpected outcome of guest-framework interactions in a soft porous crystal.
How Reproducible Are Surface Areas Calculated from the BET Equation?
Publisher: American Chemical Society (ACS)
Date: 26-05-2021
DOI: 10.26434/CHEMRXIV.14291644
Abstract: Porosity and surface area analysis play a prominent role in modern materials science, where 123 their determination spans the fields of natural sciences, engineering, geology and medical 124 research. At the heart of this sits the Brunauer-Emmett-Teller (BET) theory,[1] which has been 125 a remarkably successful contribution to the field of materials science. The BET method was 126 developed in the 1930s and is now the most widely used metric for the estimation of surface 127 areas of porous materials.[2] Since the BET method was first developed, there has been an 128 explosion in the field of nanoporous materials with the discovery of synthetic zeolites,[3] 129 nanostructured silicas,[4–6] metal-organic frameworks (MOFs),[7] and others. Despite its 130 widespread use, the manual calculation of BET surface areas causes a significant spread in 131 reported areas, resulting in reproducibility problems in both academia and industry. To probe 132 this, we have brought together 60 labs with strong track records in the study of nanoporous 133 materials. We provided eighteen adsorption isotherms and asked these researchers to 134 calculate the corresponding BET areas, resulting in a wide range of values for each one. We 135 show here that the reproducibility of BET area determination from identical isotherms is a 136 largely ignored issue, raising critical concerns over the reliability of reported BET areas in 137 the literature. To solve this major issue, we have developed a new computational approach 138 to accurately and systematically determine the BET area of nanoporous materials. Our 139 software, called BET Surface Identification (BETSI), expands on the well-known Rouquerol 140 criteria and makes, for the first time, an unambiguous BET area assignment possible.
Macroscopic Simulation of Deformation in Soft Microporous Composites
Publisher: American Chemical Society (ACS)
Date: 23-03-2017
DOI: 10.1021/ACS.JPCLETT.7B00397
Abstract: Soft microporous materials exhibit properties, such as gated adsorption and breathing, which are highly desirable for many applications. These properties are largely studied for single crystals however, many potential applications expect to construct structured or composite systems, ex les of which include monoliths and mixed-matrix membranes. Herein, we use finite element methods to predict the macroscopic mechanical response of composite microporous materials. This implementation connects the microscopic treatment of crystalline structures to the response of a macroscopic s le. Our simulations reveal the bulk modulus of an embedded adsorbent within a composite is affected by the thickness and properties of the encapsulating layer. Subsequently, we employ this methodology to examine mixed-matrix membranes and materials of negative linear compressibility. This application of finite element methods allows for unprecedented insight into the mechanical properties of real-world systems and supports the development of composites containing mechanically anomalous porous materials.
Charting a course for chemistry
Publisher: Springer Science and Business Media LLC
Date: 22-03-2019
Novel computational tools: general discussion
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0FD90034F
Towards General Network Architecture Design Criteria for Negative Gas Adsorption Transitions in Ultraporous Frameworks
Publisher: American Chemical Society (ACS)
Date: 13-03-2019
DOI: 10.26434/CHEMRXIV.7796543
Abstract: Critical design criteria for negative gas adsorption (NGA), a counterintuitive feature of pressure lifying materials, hitherto uniquely observed in a highly porous framework compound (DUT-49), are derived by analysing the physical effects of micromechanics, pore size, interpenetration, adsorption enthalpies, and the pore filling mechanism using advanced in situ X-ray and neutron diffraction, NMR spectroscopy, and calorimetric techniques parallelized to adsorption for a series of six isoreticular networks. Aided by computational modelling, we identify DUT-50 as a new pressure lifying material featuring distinct NGA transitions upon methane and argon adsorption. In situ neutron diffraction analysis of the methane (CD4) adsorption sites at 111 K supported by grand canonical Monte Carlo simulations reveals a sudden population of the largest mesopore to be the critical filling step initiating structural contraction and NGA. In contrast, interpenetration leads to framework stiffening and specific pore volume reduction, both factors effectively suppressing NGA transitions.
Predicting the Mechanical Properties of Zeolite Frameworks by Machine Learning
Publisher: American Chemical Society (ACS)
Date: 2017
DOI: 10.26434/CHEMRXIV.5349151
Abstract: We show here that machine learning is a powerful new tool for predicting the elastic response of zeolites. We built our machine learning approach relying on geometric features only, which are related to local geometry, structure and porosity of a zeolite, to predict bulk and shear moduli of zeolites with an accuracy exceeding that of force field approaches. The development of this model has illustrated clear correlations between characteristic features of a zeolite and elastic moduli providing exceptional insight into the mechanics of zeolitic frameworks. Finally, we employ this methodology to predict the elastic response of 590 448 hypothetical zeolites, and the results of this massive database provide clear evidence to stability trends in porous materials.
Metal-organic framework crystal-glass composites
Publisher: Springer Science and Business Media LLC
Date: 12-06-2019
DOI: 10.1038/S41467-019-10470-Z
Abstract: The majority of research into metal-organic frameworks (MOFs) focuses on their crystalline nature. Recent research has revealed solid-liquid transitions within the family, which we use here to create a class of functional, stable and porous composite materials. Described herein is the design, synthesis, and characterisation of MOF crystal-glass composites, formed by dispersing crystalline MOFs within a MOF-glass matrix. The coordinative bonding and chemical structure of a MIL-53 crystalline phase are preserved within the ZIF-62 glass matrix. Whilst separated phases, the interfacial interactions between the closely contacted microdomains improve the mechanical properties of the composite glass. More significantly, the high temperature open pore phase of MIL-53, which spontaneously transforms to a narrow pore upon cooling in the presence of water, is stabilised at room temperature in the crystal-glass composite. This leads to a significant improvement of CO 2 adsorption capacity.
Metal-Organic Framework Crystal-Glass Composites
Publisher: American Chemical Society (ACS)
Date: 18-09-2018
DOI: 10.26434/CHEMRXIV.7093862.V1
Abstract: The majority of research into metal-organic frameworks (MOFs) focuses on their crystalline nature. However, in recent research the vitrification of a number of MOFs has been revealed. We propose that the solid-liquid phase transitions involved in MOF-glass formation can provide unique opportunities for the creation of a new class of functional, stable and porous composite materials. Described herein is the design, synthesis, and characterisation of novel metal-organic framework (MOF) crystal-glass composites, formed by dispersing crystalline MOFs within a MOF-glass matrix. We demonstrate using structural characterisation and analytical electron tomography, that the coordinative bonding and chemical structure of a MIL-53 crystalline phase are preserved within the ZIF-62 glass matrix. Whilst separated phases, the microdomains of each lie close to one another and possess interfacial interactions which improve the mechanical properties of the composite glass. More significantly, the high temperature open pore phase of MIL-53, which spontaneously transforms to a narrow pore upon cooling, is stabilized at room temperature in the crystal-glass composite. This leads to a significantly higher gas adsorption capacity for the crystal-glass composite than for either constituent phase.
How Reproducible Are Surface Areas Calculated from the BET Equation?
Publisher: American Chemical Society (ACS)
Date: 26-05-2021
DOI: 10.26434/CHEMRXIV.14291644.V2
Abstract: Porosity and surface area analysis play a prominent role in modern materials science, where 123 their determination spans the fields of natural sciences, engineering, geology and medical 124 research. At the heart of this sits the Brunauer-Emmett-Teller (BET) theory,[1] which has been 125 a remarkably successful contribution to the field of materials science. The BET method was 126 developed in the 1930s and is now the most widely used metric for the estimation of surface 127 areas of porous materials.[2] Since the BET method was first developed, there has been an 128 explosion in the field of nanoporous materials with the discovery of synthetic zeolites,[3] 129 nanostructured silicas,[4–6] metal-organic frameworks (MOFs),[7] and others. Despite its 130 widespread use, the manual calculation of BET surface areas causes a significant spread in 131 reported areas, resulting in reproducibility problems in both academia and industry. To probe 132 this, we have brought together 60 labs with strong track records in the study of nanoporous 133 materials. We provided eighteen adsorption isotherms and asked these researchers to 134 calculate the corresponding BET areas, resulting in a wide range of values for each one. We 135 show here that the reproducibility of BET area determination from identical isotherms is a 136 largely ignored issue, raising critical concerns over the reliability of reported BET areas in 137 the literature. To solve this major issue, we have developed a new computational approach 138 to accurately and systematically determine the BET area of nanoporous materials. Our 139 software, called BET Surface Identification (BETSI), expands on the well-known Rouquerol 140 criteria and makes, for the first time, an unambiguous BET area assignment possible.
How Reproducible Are Surface Areas Calculated from the BET Equation?
Publisher: American Chemical Society (ACS)
Date: 31-03-2021
DOI: 10.26434/CHEMRXIV.14291644.V1
Abstract: Porosity and surface area analysis play a prominent role in modern materials science, where 123 their determination spans the fields of natural sciences, engineering, geology and medical 124 research. At the heart of this sits the Brunauer-Emmett-Teller (BET) theory,[1] which has been 125 a remarkably successful contribution to the field of materials science. The BET method was 126 developed in the 1930s and is now the most widely used metric for the estimation of surface 127 areas of porous materials.[2] Since the BET method was first developed, there has been an 128 explosion in the field of nanoporous materials with the discovery of synthetic zeolites,[3] 129 nanostructured silicas,[4–6] metal-organic frameworks (MOFs),[7] and others. Despite its 130 widespread use, the manual calculation of BET surface areas causes a significant spread in 131 reported areas, resulting in reproducibility problems in both academia and industry. To probe 132 this, we have brought together 60 labs with strong track records in the study of nanoporous 133 materials. We provided eighteen adsorption isotherms and asked these researchers to 134 calculate the corresponding BET areas, resulting in a wide range of values for each one. We 135 show here that the reproducibility of BET area determination from identical isotherms is a 136 largely ignored issue, raising critical concerns over the reliability of reported BET areas in 137 the literature. To solve this major issue, we have developed a new computational approach 138 to accurately and systematically determine the BET area of nanoporous materials. Our 139 software, called BET Surface Identification (BETSI), expands on the well-known Rouquerol 140 criteria and makes, for the first time, an unambiguous BET area assignment possible.
Metal-Organic Framework Crystal-Glass Composites
Publisher: American Chemical Society (ACS)
Date: 18-04-2019
DOI: 10.26434/CHEMRXIV.7093862.V2
Abstract: The majority of research into metal-organic frameworks (MOFs) focuses on their crystalline nature. However, in recent research the vitrification of a number of MOFs has been revealed. We propose that the solid-liquid phase transitions involved in MOF-glass formation can provide unique opportunities for the creation of a new class of functional, stable and porous composite materials. Described herein is the design, synthesis, and characterisation of novel metal-organic framework (MOF) crystal-glass composites, formed by dispersing crystalline MOFs within a MOF-glass matrix. We demonstrate using structural characterisation and analytical electron tomography, that the coordinative bonding and chemical structure of a MIL-53 crystalline phase are preserved within the ZIF-62 glass matrix. Whilst separated phases, the microdomains of each lie close to one another and possess interfacial interactions which improve the mechanical properties of the composite glass. More significantly, the high temperature open pore phase of MIL-53, which spontaneously transforms to a narrow pore upon cooling, is stabilized at room temperature in the crystal-glass composite. This leads to a significant improvement of CO 2 adsorption capacity.
How Reproducible are Surface Areas Calculated from the BET Equation?
Publisher: Wiley
Date: 23-05-2022
Abstract: Porosity and surface area analysis play a prominent role in modern materials science. At the heart of this sits the Brunauer–Emmett–Teller (BET) theory, which has been a remarkably successful contribution to the field of materials science. The BET method was developed in the 1930s for open surfaces but is now the most widely used metric for the estimation of surface areas of micro‐ and mesoporous materials. Despite its widespread use, the calculation of BET surface areas causes a spread in reported areas, resulting in reproducibility problems in both academia and industry. To prove this, for this analysis, 18 already‐measured raw adsorption isotherms were provided to sixty‐one labs, who were asked to calculate the corresponding BET areas. This round‐robin exercise resulted in a wide range of values. Here, the reproducibility of BET area determination from identical isotherms is demonstrated to be a largely ignored issue, raising critical concerns over the reliability of reported BET areas. To solve this major issue, a new computational approach to accurately and systematically determine the BET area of nanoporous materials is developed. The software, called “BET surface identification” (BETSI), expands on the well‐known Rouquerol criteria and makes an unambiguous BET area assignment possible.
The Role of Temperature and Adsorbate on Negative Gas Adsorption in the Mesoporous Metal-Organic Framework DUT-49
Publisher: American Chemical Society (ACS)
Date: 28-01-2020
DOI: 10.26434/CHEMRXIV.11733408.V1
Abstract: In this contribution, we present an extensive investigation of adsorption of a range of different gases at various temperatures in DUT-49, a metal-organic framework which features a negative gas adsorption (NGA) transition. Adsorption experiments at temperatures ranging from 21 to 308 K, were used to identify, for each guest, a critical temperature range in which NGA occurs. The experimental results were complemented by molecular simulations that rationalize the absence of NGA at elevated temperatures and the non-monotonic behavior observed upon temperature decrease.
Engineering micromechanics of soft porous crystals for negative gas adsorption
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0SC03727C
Abstract: We characterise the elastic properties of molecular building blocks and how they impact the mechanical properties of soft porous crystals.
Meta-MOFs: Framework Materials with Anomalous Behavior
Publisher: American Chemical Society (ACS)
Date: 05-12-2018
DOI: 10.26434/CHEMRXIV.7415249.V1
Abstract: As the number of framework materials known and characterized in the literature grows, it becomes apparent that they can carry properties rarely encountered in more conventional, dense inorganic materials. Among these materials with unusual physical or chemical properties are the ubiquitous metal–organic frameworks, covalent organic frameworks, dense coordination polymers, and molecular frameworks. Many can respond to stimulation by displaying structural responses and changes in properties that range from counter-intuitive to thermodynamically forbidden. In that, they share large similarities with metamaterials, which are engineered to generate properties not found in “normal” materials. We review here the surprising behavior of these meta-MOFs, that display properties “beyond” (μετά) the boundaries of common crystalline materials.
Nanoscale Metamaterials: Meta-MOFs and Framework Materials with Anomalous Behavior
Publisher: American Chemical Society (ACS)
Date: 11-02-2019
DOI: 10.26434/CHEMRXIV.7415249.V2
Abstract: As the number of framework materials known and characterized in the literature grows, it becomes apparent that they can carry properties rarely encountered in more conventional, dense inorganic materials. Among these materials with unusual physical or chemical properties are the ubiquitous metal–organic frameworks, covalent organic frameworks, dense coordination polymers, and molecular frameworks. Many can respond to stimulation by displaying structural responses and changes in properties that range from counter-intuitive to thermodynamically forbidden. In that, they share large similarities with metamaterials, which are engineered to generate properties not found in “normal” materials. We review here the surprising behavior of these meta-MOFs and other framework materials that display properties “beyond” (μετά) the boundaries of common crystalline materials.
Nanoscale Metamaterials: Meta-MOFs and Framework Materials with Anomalous Behavior
Publisher: American Chemical Society (ACS)
Date: 11-02-2019
DOI: 10.26434/CHEMRXIV.7415249
Abstract: As the number of framework materials known and characterized in the literature grows, it becomes apparent that they can carry properties rarely encountered in more conventional, dense inorganic materials. Among these materials with unusual physical or chemical properties are the ubiquitous metal–organic frameworks, covalent organic frameworks, dense coordination polymers, and molecular frameworks. Many can respond to stimulation by displaying structural responses and changes in properties that range from counter-intuitive to thermodynamically forbidden. In that, they share large similarities with metamaterials, which are engineered to generate properties not found in “normal” materials. We review here the surprising behavior of these meta-MOFs and other framework materials that display properties “beyond” (μετά) the boundaries of common crystalline materials. br
Computational Chemistry Methods for Nanoporous Materials
Publisher: American Chemical Society (ACS)
Date: 06-09-2016
Towards general network architecture design criteria for negative gas adsorption transitions in ultraporous frameworks
Publisher: Springer Science and Business Media LLC
Date: 12-08-2019
DOI: 10.1038/S41467-019-11565-3
Abstract: Switchable metal-organic frameworks (MOFs) have been proposed for various energy-related storage and separation applications, but the mechanistic understanding of adsorption-induced switching transitions is still at an early stage. Here we report critical design criteria for negative gas adsorption (NGA), a counterintuitive feature of pressure lifying materials, hitherto uniquely observed in a highly porous framework compound (DUT-49). These criteria are derived by analysing the physical effects of micromechanics, pore size, interpenetration, adsorption enthalpies, and the pore filling mechanism using advanced in situ X-ray and neutron diffraction, NMR spectroscopy, and calorimetric techniques parallelised to adsorption for a series of six isoreticular networks. Aided by computational modelling, we identify DUT-50 as a new pressure lifying material featuring distinct NGA transitions upon methane and argon adsorption. In situ neutron diffraction analysis of the methane (CD 4 ) adsorption sites at 111 K supported by grand canonical Monte Carlo simulations reveals a sudden population of the largest mesopore to be the critical filling step initiating structural contraction and NGA. In contrast, interpenetration leads to framework stiffening and specific pore volume reduction, both factors effectively suppressing NGA transitions.
Adsorption Contraction Mechanics: Understanding Breathing Energetics in Isoreticular Metal–Organic Frameworks
Publisher: American Chemical Society (ACS)
Date: 25-07-2018
Multicomponent Metal–Organic Frameworks as Defect-Tolerant Materials
Publisher: American Chemical Society (ACS)
Date: 21-12-2015
Nanoscale metamaterials: Meta-MOFs and framework materials with anomalous behavior
Publisher: Elsevier BV
Date: 06-2019
Polycatenated 2D Hydrogen-Bonded Binary Supramolecular Organic Frameworks (SOFs) with Enhanced Gas Adsorption and Selectivity
Publisher: American Chemical Society (ACS)
Date: 16-02-2018
Non-Interpenetrated Metal–Organic Frameworks Based on Copper(II) Paddlewheel and Oligoparaxylene-Isophthalate Linkers: Synthesis, Structure, and Gas Adsorption
Publisher: American Chemical Society (ACS)
Date: 03-2016
DOI: 10.1021/JACS.5B12312
Abstract: Two metal-organic framework materials, MFM-130 and MFM-131 (MFM = Manchester Framework Material), have been synthesized using two oligoparaxylene (OPX) tetracarboxylate linkers containing four and five aromatic rings, respectively. Both fof-type non-interpenetrated networks contain Kagomé lattice layers comprising [Cu2(COO)4] paddlewheel units and isophthalates, which are pillared by the OPX linkers. Desolvated MFM-130, MFM-130a, shows permanent porosity (BET surface area of 2173 m(2)/g, pore volume of 1.0 cm(3)/g), high H2 storage capacity at 77 K (5.3 wt% at 20 bar and 2.2 wt% at 1 bar), and a higher CH4 adsorption uptake (163 cm(3)(STP)/cm(3) (35 bar and 298 K)) compared with its structural analogue, NOTT-103. MFM-130a also shows impressive selective adsorption of C2H2, C2H4, and C2H6 over CH4 at room temperature, indicating its potential for separation of C2 hydrocarbons from CH4. The single-crystal structure of MFM-131 confirms that the methyl substituents of the paraxylene units block the windows in the Kagomé lattice layer of the framework, effectively inhibiting network interpenetration in MFM-131. This situation is to be contrasted with that of the doubly interpenetrated oligophenylene analogue, NOTT-104. Calculation of the mechanical properties of these two MOFs confirms and explains the instability of MFM-131 upon desolvation in contrast to the behavior of MFM-130. The incorporation of paraxylene units, therefore, provides an efficient method for preventing network interpenetration as well as accessing new functional materials with modified and selective sorption properties for gas substrates.
Towards General Network Architecture Design Criteria for Negative Gas Adsorption Transitions in Ultraporous Frameworks
Publisher: American Chemical Society (ACS)
Date: 13-03-2019
DOI: 10.26434/CHEMRXIV.7796543.V1
Abstract: Critical design criteria for negative gas adsorption (NGA), a counterintuitive feature of pressure lifying materials, hitherto uniquely observed in a highly porous framework compound (DUT-49), are derived by analysing the physical effects of micromechanics, pore size, interpenetration, adsorption enthalpies, and the pore filling mechanism using advanced in situ X-ray and neutron diffraction, NMR spectroscopy, and calorimetric techniques parallelized to adsorption for a series of six isoreticular networks. Aided by computational modelling, we identify DUT-50 as a new pressure lifying material featuring distinct NGA transitions upon methane and argon adsorption. In situ neutron diffraction analysis of the methane (CD4) adsorption sites at 111 K supported by grand canonical Monte Carlo simulations reveals a sudden population of the largest mesopore to be the critical filling step initiating structural contraction and NGA. In contrast, interpenetration leads to framework stiffening and specific pore volume reduction, both factors effectively suppressing NGA transitions.
Adsorption Contraction Mechanics: Understanding Breathing Energetics in Isoreticular Metal-Organic Frameworks
Publisher: American Chemical Society (ACS)
Date: 08-03-2018
DOI: 10.26434/CHEMRXIV.5962240
Abstract: In this article we report the synthesis and detailed analysis of the highly porous metal-organic framework DUT-48, isoreticular to DUT-49 a material which shows an adsorption-induced structural transition. DUT-48 has impressive porosity and methane storage capacity, however displays conventional adsorption behaviour. The contrasting flexibility of DUT-48 and DUT-49 were analysed and rationalised using a combination of novel experimental and computational techniques. Microcalorimetry measurements, in conjunction with molecular simulations, demonstrate that DUT-48 has a significantly lower adsorption enthalpy difference and a higher framework stiffness which leads to an absence of adsorption-induced transitions and negative gas adsorption (NGA). However, by analysing the mechanical behaviour of both DUT-48 and DUT-49, employing mercury porosimetry experiments, we discovered that both materials exhibit large volume changes under hydrostatic compression, demonstrating noteworthy potential as shock absorbers, and directly linking internal adsorption-induced contraction to external hydrostatic compression.
Adsorption Contraction Mechanics: Understanding Breathing Energetics in Isoreticular Metal-Organic Frameworks
Publisher: American Chemical Society (ACS)
Date: 08-03-2018
DOI: 10.26434/CHEMRXIV.5962240.V1
Abstract: In this article we report the synthesis and detailed analysis of the highly porous metal-organic framework DUT-48, isoreticular to DUT-49 a material which shows an adsorption-induced structural transition. DUT-48 has impressive porosity and methane storage capacity, however displays conventional adsorption behaviour. The contrasting flexibility of DUT-48 and DUT-49 were analysed and rationalised using a combination of novel experimental and computational techniques. Microcalorimetry measurements, in conjunction with molecular simulations, demonstrate that DUT-48 has a significantly lower adsorption enthalpy difference and a higher framework stiffness which leads to an absence of adsorption-induced transitions and negative gas adsorption (NGA). However, by analysing the mechanical behaviour of both DUT-48 and DUT-49, employing mercury porosimetry experiments, we discovered that both materials exhibit large volume changes under hydrostatic compression, demonstrating noteworthy potential as shock absorbers, and directly linking internal adsorption-induced contraction to external hydrostatic compression.
Engineering Micromechanics of Soft Porous Crystals for Negative Gas Adsorption
Publisher: American Chemical Society (ACS)
Date: 08-07-2020
DOI: 10.26434/CHEMRXIV.12619064.V1
Abstract: Framework materials at the molecular level, such as metal-organic frameworks (MOF), were recently found to exhibit exotic and counterintuitive micromechanical properties. Stimulated by host-guest interactions, these so-called soft porous crystals can display counterintuitive adsorption phenomena such as negative gas adsorption (NGA). NGA materials are bistable frameworks where the occurrence of a metastable overloaded state leads to pressure lification upon a sudden framework contraction. How can we control activation barriers and energetics via functionalization of the molecular building blocks that dictate the frameworks’ 30 mechanical response? In this work we tune the elastic and inelastic properties of building blocks at the 31 molecular level and analyze the mechanical response of the resulting frameworks. From a set of 11 frameworks, we demonstrate that widening of the backbone increases elasticity, while elongation of the building blocks results in a decrease in critical yield stress of buckling. We further functionalize the backbone by incorporation of sp3 hybridized carbon atoms to soften the molecular building blocks, or stiffen them with sp2 and sp carbons. Computational modeling shows how these modifications of the building blocks tune the 36 activation barriers within the energy landscape of the guest-free bistable frameworks. Only frameworks with free energy barriers in the range of 800 to 1100 kJ mol–1 37 per unit cell, and moderate yield stress of 0.6 to 38 1.2 nN for single ligand buckling, exhibit adsorption-induced contraction and negative gas adsorption. Advanced experimental in situ methodologies give detailed insights into the structural transitions and the adsorption behavior. The new framework DUT-160 shows the highest magnitude of NGA ever observed for nitrogen adsorption at 77 K. Our computational and experimental analysis of the energetics and mechanical response functions of porous frameworks is an important step towards tuning activation barriers in dynamic framework materials and provides critical design principles for molecular building blocks leading to pressure lifying materials
The role of temperature and adsorbate on negative gas adsorption transitions of the mesoporous metal–organic framework DUT-49
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0FD00013B
Abstract: Adsorption-induced contraction and negative gas adsorption in the mesoporous metal–organic framework DUT-49 for different gases and temperatures.
Related Organisations
University College London
Location: United Kingdom of Great Britain and Northern Ireland
Related Funding Activities
No related grants have been discovered for François-Xavier Coudert.