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. The preparation of thin covalent organic framework membranes on porous substrates using conventional in situ and secondary-growth methods is challenging. Here, the authors applied a non-solvent induced phase separation-triggered in situ interfacial polymerization strategy to produce covalent organic framework-mixed matrix membranes applied to gas separation.