LAUSR

Effective separation of ethyne from ethyne/ethylene (C2H2/C2H4) mixtures is a challenging and crucial industrial process. Herein, an ultra‐microporous metal–organic framework (MOF) platform, Cd(dicarboxylate)2(ditriazole), with triangular channels is proposed for high‐efficiency separation of C2H2 from C2H4. The targeted structures are constructed via a mixed‐ligand strategy by selecting different‐sized ligands, allowing for tunable pore sizes and volumes. The pore properties can be further optimized by additional modification via pore environment tailoring. This concept leads to the successful synthesis of three ultra‐microporous Cd‐MOFs (JLU‐MOF87–89). As intended, C2H2 uptake and C2H2/C2H4 selectivity gradually increase with progressively optimizing the pore structure by adjusting ligand length and substituents. JLU‐MOF89, functionalized with methyl groups, features the most optimal pore chemistry and shows selective recognition of C2H2 over C2H4, owing to the framework–C2H2 host–guest interactions. Furthermore, JLU‐MOFs are fabricated into mixed‐matrix membranes for C2H2/C2H4 separation. C2H2 permeability and C2H2/C2H4 permselectivity are substantially enhanced by ≥400% and ≥200%, respectively, after hybridization of JLU‐MOF88 and JLU‐MOF89 with a polyimide polymer (6FDA–ODA). These membranes can work efficiently and are stable under different conditions, demonstrating their potential in actual ethyne separation.