Tailoring Pore Environments in Metal–Organic Frameworks for Efficient C2H2/CO2 and C2H2/C2H4 Separations

Abstract The efficient separation of acetylene (C 2 H 2 ) from carbon dioxide (CO 2 ) and ethylene (C 2 H 4 ) is of significant industrial importance but remains highly challenging due to their similar physicochemical properties. In this study, three isostructural metal–organic frameworks, [Co 4 ( µ 4 ‐SO 4 ) 2 (tpim) 2 (L) 2 ] (tpim = 2,4,5‐tri(4‐pyridyl)‐imidazole, L = dicarboxylate; termed as Co 4 ‐L), are constructed from sulfate‐capped Co 4 clusters extended by N‐rich tpim linkers and different‐sized dicarboxylate ligands. Among them, the Co₄‐1,4‐ndc framework, incorporating 1,4‐naphthalenedicarboxylic acid (1,4‐ndc), offers optimal pore confinement that promotes host–guest interactions between C₂H₂ molecules and framework. This material exhibits high C₂H₂ capture capacities of 4.30 and 3.40 mmol g − ¹ from equimolar C₂H₂/CO₂ and C₂H₂/C₂H₄ mixtures, respectively. Theoretical simulations reveal that the enhanced selectivity arises from multiple cooperative hydrogen‐bonding interactions between C₂H₂ and the framework Co₄‐1,4‐ndc , generating strong and preferential binding sites. This study highlights the role of pore‐environment engineering of metal‐organic frameworks (MOFs) for selective C₂H₂ separation, providing a foundation for the development of advanced adsorbents in industrial gas purification.