Acetylene‐Triggered Gate‐Opening Behavior in a Stable Rigid‐Flexible MOF for Efficient C 2 H 2 /CO 2 Separation

Abstract High‐purity acetylene (C 2 H 2 ) is indispensable in the chemical industry. However, C 2 H 2 produced via the calcium carbide process contains trace CO 2 impurities, necessitating purification. Due to their comparable molecular dimensions (3.3 × 3.3 × 5.7 Å 3 for C 2 H 2 vs 3.2 × 3.3 × 5.4 Å 3 for CO 2 ), achieving effective separation remains a challenge. For the first time, this work achieves efficient C 2 H 2 /CO 2 separation in an ultra‐stable metal–organic framework (MOF) featuring a synergistic rigid‐flexible structure, characterized by a 2‐fold interpenetrating MOF that incorporates an unprecedented [Zn 4 N 9 ] n chain. The rigid molecular chains ensure stability, as the structure is retained after immersion in strong acidic environments for one month. The 2‐fold interpenetration architecture imparts controlled structural flexibility to the framework, triggering a stimuli‐responsive gate‐opening phenomenon upon C 2 H 2 adsorption. This dynamic structural transformation induces a significant pore environment modulation, as quantified by the expansion of the pore limiting diameter ( PLD ) from 3.09 to 3.34 Å. The precisely tuned aperture demonstrates exceptional molecular sieving capabilities, permitting selective C 2 H 2 permeation while effectively rejecting CO 2 molecules due to their differential kinetic diameters. Integrated analysis of gas adsorption isotherms, theoretical calculations, breakthrough experiments, and stability assessments synergistically confirm the structural robustness and selective separation efficacy of this interpenetrated framework.