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.