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Abstract Flexible metal–organic materials that exhibit stimulus-responsive switching between closed (non-porous) and open (porous) structures induced by gas molecules are of potential utility in gas storage and separation. Such behaviour is currently limited to a few dozen physisorbents that typically switch through a breathing mechanism requiring structural contortions. Here we show a clathrate (non-porous) coordination network that undergoes gas-induced switching between multiple non-porous phases through transient porosity, which involves the diffusion of guests between discrete voids through intra-network distortions. This material is synthesized as a clathrate phase with solvent-filled cavities; evacuation affords a single-crystal to single-crystal transformation to a phase with smaller cavities. At 298 K, carbon dioxide, acetylene, ethylene and ethane induce reversible switching between guest-free and gas-loaded clathrate phases. For carbon dioxide and acetylene at cryogenic temperatures, phases showing progressively higher loadings were observed and characterized using in situ X-ray diffraction, and the mechanism of diffusion was computationally elucidated. 

Abstract The capture of the xenon and krypton from nuclear reprocessing off‐gas is essential to the treatment of radioactive waste. Although various porous materials have been employed to capture Xe and Kr, the development of high‐performance adsorbents capable of trapping Xe/Kr at very low partial pressure as in the nuclear reprocessing off‐gas conditions remains challenging. Herein, we report a self‐adjusting metal‐organic framework based on multiple weak binding interactions to capture trace Xe and Kr from the nuclear reprocessing off‐gas. The self‐adjusting behavior of ATC‐Cu and its mechanism have been visualized by the in‐situ single‐crystal X‐ray diffraction studies and theoretical calculations. The self‐adjusting behavior endows ATC‐Cu unprecedented uptake capacities of 2.65 and 0.52 mmol g⁻¹for Xe and Kr respectively at 0.1 bar and 298 K, as well as the record Xe capture capability from the nuclear reprocessing off‐gas. Our work not only provides a benchmark Xe adsorbent but proposes a new route to construct smart materials for efficient separations.