Oriented Ultrathin π‐complexation MOF Membrane for Ethylene/Ethane and Flue Gas Separations

Abstract Rational design and engineering of high‐performance molecular sieve membranes towards C 2 H 4 /C 2 H 6 and flue gas separations remain a grand challenge to date. In this study, through combining pore micro‐environment engineering with meso‐structure manipulation, highly c ‐oriented sub‐100 nm‐thick Cu@NH 2 ‐MIL‐125 membrane was successfully prepared. Coordinatively unsaturated Cu ions immobilized in the NH 2 ‐MIL‐125 framework enabled high‐affinity π‐complexation interactions with C 2 H 4 , resulting in an C 2 H 4 /C 2 H 6 selectivity approaching 13.6, which was 9.4 times higher than that of pristine NH 2 ‐MIL‐125 membrane; moreover, benefiting from π‐complexation interactions between CO 2 and Cu(I) sites, our membrane displayed superior CO 2 /N 2 selectivity of 43.2 with CO 2 permeance of 696 GPU, which far surpassed the benchmark of other pure MOF membranes. The above multi‐scale structure optimization strategy is anticipated to present opportunities for significantly enhancing the separation performance of diverse molecular sieve membranes.