Covalent‐Linking‐Enabled Superior Compatibility of ZIF‐8 Hybrid Membrane for Efficient Propylene Separation

Abstract The interface is a critical issue for metal–organic‐framework hybrid membranes in propylene separation. Here, a covalent‐linking strategy is reported for strikingly reinforcing the interfacial compatibility in a ZIF‐8‐based membrane. A functionalized ZIF‐8 material named ZIF‐8‐CN is synthesized using the mixed‐ligand approach. ZIF‐8‐CN has an identical crystalline structure to ZIF‐8, and the 4,5‐dicyanoimidazole ligand is available for further functionalization. Covalent linkage of ZIF‐8‐CN with PIM‐1 is driven by the thermal reaction of the cyano groups on both entities, which strengthens the filler–polymer connection in the ZIF‐8‐CN@tPIM‐1 membrane. ZIF‐8‐CN@tPIM‐1 exhibits remarkably enhanced propylene permeation property with C₃H₆/C₃H₈ selectivity of ≈28, which is 350% and 180% higher than those on non‐treated ZIF‐8‐CN/PIM‐1 and non‐functionalized ZIF‐8@tPIM‐1, respectively. Additionally, ZIF‐8‐CN@tPIM‐1 shows the highest C₃H₆ permeability of ≈370 Barrer among all relevant ZIF‐8 membranes. This strategy opens an avenue for precise interface engineering in membranes and the resultant high performance is appealing in the propylene separation industry.