Dual‐Wing Ligand Constructed Metal–Organic Framework Membranes with Finely Tuned Apertures for Natural Gas Separation

Abstract Metal–organic framework (MOF) membranes with apparent molecular sieving effects have great potential for gas separation. However, their application in light‐gas separation (e.g., CO 2 /CH 4 and H 2 /CH 4 ) remains challenging due to their enlarged pore structures under transmembrane pressure. In this work, a series of MOF membranes constructed from dual‐wing (DW) ligands including 2‐chloromethylbenzimidazole, 2‐methylbenzimidazole, 2‐ethylbenzimidazole, and 2‐phenylbenzimidazole are reported, to finely tune apertures and enhance molecule sieving property for small‐size gases. These DW‐ligands provide steric resistance in two directions perpendicular to the coordination bond, leading to a much finer pore structure. The introduction of the DW‐ligands endows the DW/ZIF‐8 membranes with an adjustable bottleneck door for regulating gas diffusion, blocking the transport of large‐sized CH 4 while allowing small‐sized H 2 and CO 2 to permeate. The membranes show significantly improved molecular sieving property with a CO 2 /CH 4 mixed‐gas selectivity of 58.6 in the case of 2‐chloromethylbenzimidazole 23 /ZIF‐8, which represents the highest value among the reported ZIF membranes. This membrane also exhibits exceptional separation performance for H 2 /CH 4 and H 2 /C 3 H 8 with separation factors of 430 and 34341, which are the highest values among the reported MOF membranes. This study presents a facile and efficient strategy for regulating MOF aperture and constructing high‐performance membranes for natural gas separation.