Asymmetrical covalent organic framework mixed matrix membranes for highly efficient gas separation

The asymmetrical and seamless Covalent organic framework (COF)-mixed matrix membranes (COF-MMMs) extending over the centimeter scale for highly efficient H₂/CO₂ separation are fabricated via a non-solvent induced phase separation (NIPS)-triggered in situ interfacial polymerization (IP) strategy. Here, a dense and ultrathin COF membrane (15-30 nm thick) is fabricated on the surface of the Polyether sulfone (PES) skin layer, and isolated COF nanocrystals (4-8 nm) are formed and highly dispersed inside the PES matrix through in situ interfacial polymerization. No interfacial defects are detected between the COF nanocrystals and the PES matrix. The COF-MMMs exhibit H₂/CO₂ selectivity of 88.8 ± 2.46 at an ambient temperature of 298 K, while maintaining a high H₂ permeance of 2738 ± 58.02 GPU. This study proposes a facile strategy to fabricate large-scale high-performance COF-MMMs for gas separation.