Crystals springing into action : metal–organic framework CUK-1 as a pressure-driven molecular spring

Mercury porosimetry and in situ high pressure single crystal X-ray diffraction revealed the wine-rack CUK-1 MOF as a unique crystalline material capable of a fully reversible mechanical pressure-triggered structural contraction. The near-absence of hysteresis upon cycling exhibited by this robust MOF, akin to an ideal molecular spring, is associated with a constant work energy storage capacity of 40 J g(-1). Molecular simulations were further deployed to uncover the free-energy landscape behind this unprecedented pressure-responsive phenomenon in the area of compliant hybrid porous materials. This discovery is of utmost importance from the perspective of instant energy storage and delivery

Exploration des sources de variabilité dans les réseaux métallo-organiques par adsorption à haut débit et méthodes calorimétiques

Les réseaux métallo-organiques (MOF) sont une nouvelle classe de matériaux poreux hybrides. Néanmoins leurs propriétés uniques introduisent également des difficultés significatives dans la caractérisation par adsorption de gaz. Dans cette thèse, la création d'un code source libre est détaillé, pour standardiser le traitement des isothermes. En utilisant ce code, un traitement à haut débit de plus de 18 000 isothermes est utilisé pour explorer l'échelle d'incertitude présente dans les données publiées sur l'adsorption dans les matériaux poreux. De plus, la mesure directe de l'enthalpie différentielle de l'adsorption en utilisant la microcalorimétrie s'avère être un excellent moyen d'obtenir la contribution des interactions particulières sur l'énergie d'adsorption. Ensemble, ces méthodes peuvent être utilisées pour étudier les sources d'incertitude des MOF. On étudie d’abord l’impact des défauts structurels au moyen d’une méthode post-synthétique alternative de génération de linker/cluster manquants dans l'UiO-66(Zr). Le traitement des matériaux pour leurs utilisations dans un environnement industriel par façonnage est étudié ici sous l’effet de la granulation par voie humide sur trois MOF topiques (UiO-66(Zr), MIL-100(Fe) et MIL-127(Fe)). Enfin, les comportements contre-intuitifs intrinsèques aux cristaux poreux «souples» sont étudiés, où la structure elle-même est responsable de la fluctuation dans les isothermes d'adsorption. Ici, une étude fondamentale sur un matériau flexible DUT-49 (Cu), apporte des informations sur la source de flexibilité induite par adsorption et sa changeabilité par modification structurelleMetal organic frameworks (MOF) are novel adsorption materials with unique and desirable properties. However, structural defects, processing and structural compliance can lead to irreproducibility in adorption measurements. In this thesis, the creation of an open-source codebase is detailed, which is intended to standardize the processing of isotherms. Using this framework, high throughput processing of over 18 000 isotherms is used to explore the scale of uncertainty present in published adsorption data. Then, direct measurement of the differential enthalpy of adsorption using microcalorimetry is shown to be an excellent avenue of obtaining further insight into the contribution of guest-host and host-host interactions to the overall energetics of adsorption. Together, these methods are used to study some of the sources of the variability of MOFs, and quantify their effect. First, the impact of structural defects is investigated, through an alternative post-synthetic method of missing linker/cluster generation in the prototypical UiO-66(Zr) MOF. The processing of materials for their use in an industrial environment through shaping is another potential source of performance modification, which is here studied as the effect of wet granulation on three topical MOFs (UiO-66(Zr), MIL-100(Fe) and MIL-127(Fe)). Finally, counterintuitive behaviours intrinsic to ``soft'' porous crystals are investigated, where the structure itself is responsible for fluctuation in adsorption isotherms. A fundamental study on a copper paddlewheel based material, DUT-49(Cu) yields know-how on the source of adsorption induced compliance and its tunability through structural modificatio

Data Mining for Binary Separation Materials in Published Adsorption Isotherms

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pyGAPS: A Python-Based Framework for Adsorption Isotherm Processing and Material Characterisation

Material characterisation through adsorption is a widely-used laboratory technique. The isotherms obtained through volumetric or gravimetric experiments impart insight through their features but can also be analysed to determine material characteristics such as specific surface area, pore size distribution, surface energetics, or used for predicting mixture adsorption. The pyGAPS (python General Adsorption Processing Suite) framework was developed to address the need for high-throughput processing of such adsorption data, independent of the origin, while also being capable of presenting individual results in a user-friendly manner. It contains many common characterisation methods such as: BET and Langmuir surface area, t and α plots, pore size distribution calculations (BJH, Dollimore-Heal, Horvath-Kawazoe, DFT/NLDFT kernel fitting), isosteric heat calculations, IAST calculations, isotherm modelling and more, as well as the ability to import and store data from Excel, CSV, JSON and sqlite databases. In this work, a description of the capabilities of pyGAPS is presented. The code is then be used in two case studies: a routine characterisation of a UiO-66(Zr) sample and in the processing of an adsorption dataset of a commercial carbon (Takeda 5A) for applications in gas separation

Can the NIST Adsorption Database Be Used to Highlight Potential Materials for Gas Separation?

Scientific literature is replete with descriptions of novel adsorbent materials, making the selection of such adsorbents for gas storage and separation a trudging task, and often resulting in overlooked materials. Here, we use a high throughput methodology o process a dataset of 28 000 adsorption isotherms from the NIST adsorption database (ISODB) and generate key performance indicators applicable to ambient temperature binary separation on 1500 materials in the collection, with 30 adsorbed guests. The procedure is validated against high-quality laboratory isotherms to confirm the accuracy of the derived indicators. The results are then collated in a powerful online dashboard, which can be used to explore the binary correlations. Finally, we use this toolchain to scrutinize several challenging and industrially relevant case studies and highlight somematerials which may be promising for further analysis.</div

Low Temperature Calorimetry Coupled with Molecular Simulations for an In-Depth Characterization of the Guest-Dependent Compliant Behavior of MOFs

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Investigating the Effect of Alumina Shaping on the Sorption Properties of Promising Metal-Organic Frameworks

Three promising MOF candidates, UiO-66(Zr), MIL-100(Fe) and MIL-127(Fe) are shaped through granulation with a rho-alumina binder. Subsequently, changes in the surface characteristics and adsorption performance are evaluated through adsorption microcalorimetry at 303 K with several common probes (N2, CO2, CO, CH4, C2H6, C3H8, C3H6 and C4H10), generating a detailed picture of adsorbate-adsorbent interactions. Vapour adsorption experiments with water and methanol were further used to gauge changes in hydrophobicity caused by the addition of the alumina binder. Upon shaping, a decrease in gravimetric capacity and specific surface area is observed, accompanied by an increased capacity on a volumetric basis, attributed to densification induced by the shaping process, as well as a surprising lack of pore environment changes. However, the magnitude of these effects depends on the MOF, suggesting a high dependence on material structure. Out of the three materials, MIL-127(Fe) shows the least changes in adsorption performance and is highlighted as a promising candidate for further study

Low Temperature Calorimetry Coupled with Molecular Simulations for an In-Depth Characterization of the Guest-Dependent Compliant Behaviour of MOFs

In this study adsorption microcalorimetry is employed to monitor the adsorption of four probes (argon, oxygen, nitrogen and carbon monoxide) on a highly flexible mesoporous metal-organic framework (DUT-49, DUT = Dresden University of Technology), precisely measuring the differential enthalpy of adsorption alongside high-resolution isotherms. This experimental approach combined with force field Monte Carlo simulations reveals distinct pore filling adsorption behaviours for the selected probes, with argon and oxygen showing abrupt adsorption in the open pore form of DUT-49, in contrast with the gradual filling for nitrogen and carbon monoxide. A complex structural transition behaviour of DUT-49 observed upon nitrogen adsorption is elucidated through an isotherm deconvolution in order to quantify the fraction of the open pore, contracted pore and intermediate pore forms that coexists at a given gas pressure. Finally, the heat flow measured during the guest-induced structural contraction of DUT-49 allowed an exploration of complex open-contracted pore transition energetics, leading to a first assessment of the energy required to induce this spectacular structural change

Investigating the effect of alumina shaping on the sorption properties of promising metal–organic frameworks

International audienceThree promising MOF candidates, UiO-66(Zr), MIL-100(Fe) and MIL-127(Fe) are shaped through granulation with a r-alumina binder. Subsequently, changes in the surface characteristics and adsorption performance are evaluated through adsorption microcalorimetry at 303 K with several common probes (N 2 , CO 2 , CO, CH 4 , C 2 H 6 , C 3 H 8 , C 3 H 6 and C 4 H 10), generating a detailed picture of adsorbate-adsorbent interactions. Vapour adsorption experiments with water and methanol were further used to gauge changes in hydrophobicity caused by the addition of the alumina binder. Upon shaping, a decrease in gravimetric capacity and specific surface area is observed, accompanied by an increased capacity on a volumetric basis, attributed to densification induced by the shaping process, as well as a surprising lack of pore environment changes. However, the magnitude of these effects depends on the MOF, suggesting a high dependence on material structure. Out of the three materials, MIL-127(Fe) shows the least changes in adsorption performance and is highlighted as a promising candidate for further study

Preface

Conference proceeding Document Type: Editoria