Adaptive Corner-Pocket Channels in a Metal-Organic Framework for Acetylene Ultra-Fast Diffusion and Storage.

Ultra-microporous molecular sieving materials offer exceptional size- and shape-selective gas separation, yet their practical use is often limited by slow diffusion kinetics and low adsorption capacities. Here, we report a low-cost manganese-based metal-organic framework (MOF), Mn-dcbp, featuring an adaptive "corner-pocket" channel structure. While retaining C2H2/C2H4 sieving selectivity, the material successfully integrates a high acetylene (C2H2) uptake (126.3 cm3/cm3) with ultrafast diffusion kinetics (k = 0.01863 s-1). In situ single-crystal x-ray diffraction reveals a sub-angstrom-level structural adaptation mechanism induced by C2H2, leading to ordered, high-density packing of C2H2 within the channels and achieving a record storage density of 1.02 g/mL. Strong host-guest interactions enable the material to maintain excellent C2H2 adsorption capacity (110.6 cm3/cm3) even at elevated temperatures (75 °C), while also demonstrating superior separation performance for C2H2/C2H4 and C2H2/CO2 gas mixtures. Furthermore, Mn-dcbp can be produced on a large scale via an environmentally friendly route and exhibits excellent, water, thermal, and cycling stability, which is crucial for potential industrial implementation.