In general, the relatively modest expansion experienced by most materials on heating is caused by increasing anharmonic vibrational amplitudes of the constituent atoms, ions or molecules. This phenomenon is called positive thermal expansion (PTE) and usually occurs along all three crystallographic axes. In very rare cases, structural peculiarities may give rise either to anomalously large PTE, or to negative thermal expansion (NTE, when lattice dimensions shrink with heating). As NTE and unusually large PTE are extremely uncommon for molecular solids, mechanisms that might give rise to such phenomena are poorly understood. Here we show that the packing arrangement of a simple dumbbell-shaped organic molecule, coupled with its intermolecular interactions, facilitates a cooperative mechanical response of the three-dimensional framework to changes in temperature. A series of detailed structural determinations at 15-K intervals has allowed us to visualize the process at the molecular level. The underlying mechanism is reminiscent of a three-dimensional (3D) folding trellis and results in exceptionally large and reversible uniaxial PTE and biaxial NTE of the crystal. Understanding such mechanisms is highly desirable for the future design of sensitive thermomechanical actuators.

The liquid-phase epitaxy (LPE) method was effectively implemented to deliberately grow/construct ultrathin (0.5-1 μm) continuous and defect-free ZIF-8 membranes. Permeation properties of different gas pair systems (O2-N2, H2-CO2, CO2-CH4, C3H6-C3H8, CH4-n-C4H10) were studied using the time lag technique.

Crystallographic pressure-lapse snapshots of a porous material responding to gas loading were used to investigate the stepwise uptake of carbon dioxide and acetylene molecules into discrete confined spaces. Based on the data, a qualitative statistical mechanical model was devised that reproduces even subtle features in the experimental gas sorption isotherms.

Free vacancies: A robust and porous metal–organic framework material with unique 4‐connected self‐catenating structure of {85⋅10} topology was synthesized. The structure features empty bipyridine metal‐chelating sites that can be doped with copper cations in a single‐crystal‐to‐single‐crystal post‐synthetic modification (see picture; scale bar 20 μm).

The concepts relating to the structures and properties of crystals involve numerous terms that might be especially bewildering to the nonspecialist. Many of these terms have been borrowed and/or adapted from mineralogy, a much older branch of crystallography and involving a different community of researchers, while others have been coined at will to describe either new concepts or concepts for which suitable terms did not exist before. As a result, crystallographic nomenclature is far from systematic and the lexicon of modern crystallography has evolved as a haphazard collection of terms. This contribution presents a survey of the concepts that arise during the crystallographic studies of crystals, with the rather ambitious goal of achieving disambiguation regarding nomenclature. The authors specifically discuss terms that they have identified as being highly relevant to modern chemical crystallography.

Mechanochemical synthesis has been used to obtain two Werner complexes and their solid solution that could not be obtained by conventional "wet" chemistry; remarkably, despite the structural and chemical similarity, the solid solution exhibits sorption properties that differ from those of the pure compounds.

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A quasiracemic mixture of Dianin's compound and its thiol derivative enforces additional anisotropy of the guest-accessible space, thus facilitating a net polar arrangement of guest molecules; guest alignment is rationalized in terms of van der Waals volume considerations.