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For adsorption processes, gas uptake usually increases with increasing pressure; however, here the phenomenon of negative gas adsorption is demonstrated in a metal–organic framework, which undergoes a sudden hysteretic structural deformation and pore contraction, releasing guest molecules.

Two-dimensional covalent organic frameworks (2D COFs) enable the construction of bespoke functional materials, but designing dynamic 2D COFs is challenging. Now it has been shown that perylene-diimide-based COFs can open and close their pores upon uptake or removal of guests, while fully retaining their crystalline long-range order. Moreover, the variable COF geometry enables stimuli-responsive optoelectronic properties.

Switchable porous materials offer adaptive voids mutating in size and shape in response to molecular stimuli. Here authors use PFG NMR to reveal the decisive role of metastable states leading to counterintuitive negative gas adsorption transitions in responsive MOFs.

The application of photoswitches as light-responsive triggers for phase transitions of porous materials remains poorly explored. Here, the authors report a light-responsive flexible metal-organic framework which undergoes pore contraction upon combined application of light irradiation and adsorption stress via a buckling process of the framework-embedded azobenzene photoswitch.

Pressure amplification phenomena have recently been observed in ordered mesoporous solids, but little is understood about this counter-intuitive behaviour. Here, Kaskel and colleagues demonstrate that crystal size can play an important role in modulating pressure amplification in metal-organic frameworks.

Inexpensive and selective electrocatalysts for CO₂ reduction hold promise for sustainable fuel production. Here, the authors report N-coordinated, non-noble metal-doped porous carbons as efficient and selective electrocatalysts for CO₂ to CO conversion.

High-valent iron compounds do not form spontaneously under ambient conditions and those that are synthetically available are rarely stable. Here, the authors synthesize stable iron(IV) hexahydrazide clathrochelate complexes in aqueous media via a metal-templated reaction accompanied by aerobic oxidation.

Porous framework material DUT-49 was recently demonstrated to exhibit a unique counterintuitive negative gas adsorption (NGA) behaviour. Here the authors identify framework DUT-50 as an additional pressure amplifying material that features distinct NGA transitions, and suggest structural design criteria to access other such materials.

As the field of metal-organic frameworks is maturing, understanding the dynamics of open frameworks is progressing and rational approaches are under development. Here, the authors outline challenges and potential routes to engineering the spatio-temporal evolution of dynamic metal-organic frameworks.