Crystalline B-N-H compounds of low molecular weight have been intensively investigated over the past two decades owing to their promises for chemical hydrogen storage. Hydrazine borane NH-NH-BH is one of the most recent examples of this family of materials. In the present work, we explored its structural behaviour under mechanical stimulus by synchrotron high pressure X-ray diffraction. It has been evidenced that hydrazine borane shows a gradual pressure-induced decrease of its unit cell dimension and the process is reversible when the applied pressure is released. The compressibility of this material was established to be relatively low (high bulk modulus) and highly anisotropic. As revealed by molecular simulations based on Density Functional Theory calculations, the mechanical behaviour of NH-NH-BH was correlated to the pressure-induced changes of its crystal structure in terms of intra- and intermolecular bond lengths and angles parameters.
The proton-conducting performances of a microporous Ti-based metal–organic
framework (MOF), MIP-207, were successfully tuned using a multicomponent
ligand replacement strategy to gradually introduce a controlled amount
of sulfonic acid groups as a source of Brönsted acidic sites
while keeping the robustness and ecofriendly synthesis conditions
of the starting material. Typically, multivariate sulfonic-based solids
MIP-207-(SO3H-IPA)
x
-(BTC)1–x
were prepared by combining various
ratios of trimesate 1,3,5-benzenetricarboxylate (BTC) moieties and
5-SO3H-isophthalate (SO3H-IPA). The best sulfonic-MOF
candidate that combines structural integrity with high proton conductivity
values (e.g., σ = 2.6 × 10–2 S cm–1 at 363 K/95% relative humidity) was further
investigated using ab initio molecular dynamics simulations.
These calculations supported that the −SO3H groups
act as proton donors and revealed that the proton transfer mechanism
results from the solvation structure of protons through the fast Zundel/hydronium
interconversion along the continuous H-bonded network connecting the
adsorbed water molecules.
The ZF-3 molecular crystal containing KCl ions pairs exhibits optimum humidity-sensitive performance in terms of ionic conductivity. Molecular Dynamics simulations evidence that the water-assisted conductivity behavior of ZF-3 results from...
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