Ligand‐Orientation‐Controlled Pore‐Space Partitioning Enables Topology‐Preserving Pore Engineering for Efficient Acetylene Separation

ABSTRACT Efficient separation of acetylene (C 2 H 2 ) from C 2 H 2 /C 2 H 4 and C 2 H 2 /CO 2 mixtures remains a persistent challenge owing to the comparable physicochemical properties of the gases. Herein, a ligand‐orientation‐controlled pore‐space partitioning (LO‐PSP) strategy is proposed to regulate pore environments in metal–organic frameworks (MOFs). Isoreticular substitution of dicarboxylate ligands in two Zn 5 ‐cluster‐based MOFs ( Zn 5 ‐BDC and Zn 5 ‐ADC ) induces an approximately 90 ° rotation of the aromatic backbone, transforming a pore‐external to a pore‐intrusive configuration and subdividing large cavities into confined domains without altering framework topology. Consequently, Zn 5 ‐ADC exhibits improved C 2 H 2 uptake, reaching 1.5 times that of Zn 5 ‐BDC at 10 kPa and 298 K, together with enhanced dynamic separation performance. In particular, Zn 5 ‐ADC enables efficient removal of trace C 2 H 2 from C 2 H 2 /C 2 H 4 mixtures, directly delivering polymer‐grade (≥99.99%) C 2 H 4 with high productivity. Theoretical calculations reveal that the confined pore environment enables multiple binding configurations of C 2 H 2 through C–H···O/N and C–H···π cooperative interactions, giving rise to stronger and more diverse host–guest interactions than for C 2 H 4 and CO 2 .