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Physical adsorption at cryogenic temperature (cryoadsorption) is a reversible mechanism that can reduce the pressure of conventional compressed gas storage systems. Metal–organic framework (MOF) materials are remarkable candidates due to the combination of high specific surface area and density which, in some cases, provide a high volumetric storage capacity. However, such extensive use of MOFs for this application requires the selection of affordable structures, easy to produce and made from feasible metallic and organic components. Herein, we introduce a MOF database detailing the crystallographic and porous properties of 3600 existing MOFs made from industrially relevant metals and their organic composition. The comparison of the available minimum costs of linkers allowed the creation of a database to select affordable structures with high potential for volumetric hydrogen storage by cryoadsorption, considering their composition based on individual or mixed building blocks. A user interface, available online, facilitates the selection of MOFs based on the properties or names of structures and linkers.
An amorphous Lewis-acidic zirconium chlorofluoride as HF shuttle: C–F bond activation and formation
(2023)
An exceptional HF transfer reaction by C–F bond activation of fluoropentane and a subsequent hydrofluorination of alkynes at room temperature is reported. An amorphous Lewis-acidic Zr chlorofluoride serves as heterogeneous catalyst, which is characterised by an eightfold coordination environment at Zr including chlorine atoms. The studies are seminal in establishing sustainable fluorine chemistry.
Ananion-dopedaluminiumchlorofluoride AlCl0.1F2.8(OTeF5)0.1(ACF-teflate) was synthesized.The material contains pentafluor-oorthotellurate(teflate)groups, which mimic fluoride ions electronically, but are sterically more demanding. They are embedded into the amorphous structure. The latter was studied by PDF analysis, EXAFS data and MAS NMR spectroscopy. The mesoporous powder is a Lewis superacid, and ATR-IR spectra of adsorbed CD3CN reveal a blue-shift of the adsorption band by73 cm-1, which is larger than the shift for SbF5. Remarkably,ACF-teflate catalyzes dehydrofluorination reactions of mono-fluoroalkanes to yield olefins in C6D6. In these cases,no Friedel-Crafts products were formed.
Mechanically flexible single crystals of molecular materials offer potential for a multitude of new directions in advanced materials design. Before the full potential of such materials can be exploited, insight into their mechanisms of action must be better understood. Such insight can be only obtained through synergistic use of advanced experimentation and simulation. We herein report the first detailed mechanistic study of elasto-plastic flexibility in a molecular solid. An atomistic origin for this mechanical behaviour is proposed through a combination of atomic force microscopy, μ-focus synchrotron X-ray diffraction, Raman spectroscopy, ab initio simulation, and computed elastic tensors. Our findings suggest that elastic and plastic bending are intimately linked and result from extensions of the same molecular deformations. The proposed mechanism bridges the gap between contested mechanisms, suggesting its applicability as a general mechanism for elastic and plastic bending in organic molecular crystals.
With increasing demand and environmental concerns, researchers are exploring new materials that can perform as well or better than traditional materials while reducing environmental impact. The BAMline, a real-life sample materials research beamline, provides unique insights into materials’ electronic and chemical structure at different time and length scales. The beamline specializes in x-ray absorption spectroscopy, x-ray fluorescence spectroscopy, and tomography experiments. This enables real-time optimization of material properties and performance for various applications, such as energy transfer, energy storage, catalysis, and corrosion resistance. This paper gives an overview of the analytical methods and sample environments of the BAMline, which cover non-destructive testing experiments in materials science, chemistry, biology, medicine, and cultural heritage. We also present our own synthesis methods, processes, and equipment developed specifically for the BAMline, and we give examples of synthesized materials and their potential applications. Finally, this article discusses the future perspectives of the BAMline and its potential for further advances in sustainable materials research.
This talk explores the intricate connections between scientists, focusing on the networking dynamics within the realm of metal-organic frameworks (MOFs). The study delves into the collaborative networks formed among scientists, shedding light on the synergistic relationships that contribute to advancements in MOF research.
Due to their favorable properties and high porosity, zeolitic imidazolate frameworks (ZIFs) have recently received much limelight for key technologies such as energy storage, optoelectronics, sensorics, and catalysis. Despite widespread interest in these materials, fundamental questions regarding the zinc coordination environment remain poorly understood. By focusing on zinc(II)2-methylimidazolate (ZIF-8) and its tetrahedrally coordinated analogues with Br-, Cl-, and H-substitution in the 2-ring position, we aim to clarify how variations in the local environment of Zn impact the charge distribution and the electronic properties of these materials. Our results from densityfunctional theory confirm the presence of a Zn coordinative bond with a large polarization that is quantitatively affected by different substituents on the organic ligand. Moreover, our findings suggest that the variations in the Zn coordination induced by the functionalization have a negligible effect on the electronic structure of the considered compounds. On the other hand, halogen terminations of the ligands lead to distinct electronic contributions in the vicinity of the frontier region which ultimately reduce the band gap size by a few hundred millielectron volts. Experimental results obtained from X-ray absorption spectroscopy (Zn K-edge) confirm the trends predicted by theory and, together with them, contribute to a better understanding of the structure−property relationships that are needed to tailor ZIFs for target applications.
The lattice enthalpies and monotropic relationship of two dehydroepiandrosterone (DEHA) polymorphs (forms I and II) were evaluated through a combination of differential scanning calorimetry (DSC), isothermal solution microcalorimetry, and drop-sublimation Calvet microcalorimetry experiments. The standard molar enthalpy of transition between both forms was determined as ΔtrsHom (II→I, 298.15 K) = - 0.90 ± 0.07 kJ mol-1 and ΔtrsHom (II→I, 417.8 K) = - 1.7 ± 1.0 kJ mol- 1, from measurements of standard molar enthalpies of solution in dimethyl sulfoxide and enthalpies of fusion, respectively. Drop-sublimation Calvet microcalorimetry experiments on form I led to ΔsubHom (cr I, 298.15 K) = 132.0±3.3 kJ mol - 1. This result, when combined with the more precise ΔtrsHom (II→I) value obtained by solution calorimetry, afforded ΔsubHom (cr II, 298.15 K) = 131.1±3.3 kJ mol - 1. The overall data indicate that on enthalpic grounds form I is more stable than form II from 298.15 K up to fusion. This conclusion, and the fact that DSC experiments indicated that form I has also a considerably higher temperature fusion, namely, Tfus(cr I)= 422.5±0.2 K and Tfus(cr II) = 413.1±0.2 K, suggest that the two polymorphs are monotropically related.