Facile manufacture of COF-based mixed matrix membranes for efficient CO2 separation

Abstract

• In situ bottom-up growth strategy is proposed to manufacture 2D-COF-based MMMs. • The new method allows the favorable reduction of COF pore sizes. • MMMs contain uniformly distributed COFs and feature good interfacial compatibility. • MMM shows a 185.9% increase in permeability and a 32–77% enhancement in selectivity compared with pristine polymer membranes. Mixed-matrix membranes containing covalent-organic frameworks (COFs) and polymer phase hold great promise for effective and economical CO 2 separation due to the robust and tunable porous framework structures of COFs. However, the pore sizes of most reported COFs are larger than gas molecules. Meanwhile, the undesired COF aggregation impedes the preparation of continuous and defect-free membranes. Herein, we describe a new strategy for the facile manufacture of 2D-COF based mixed-matrix membranes via in situ “bottom-up” growth approach which involved the admixing of COF precursors with PEO monomers at the molecular level in a solvent-free system. Free radical polymerization allowed the formation of polymer membranes containing well-dispersed COF precursors. The 2D-COFs with uniform distributions were further generated via the covalent linkages of precursors within the cross-linked polymer network under microwave assisted Zincke reaction. The resulting mixed-matrix membrane exhibited a remarkable permeability of 803.9 barrer for CO 2 and selectivities of 61.4, 19.8, 15.0 for CO 2 /N 2 , CO 2 /CH 4 , CO 2 /H 2 , respectively, exceeding the known upper-bound limits reported for polymer membranes. Meanwhile, the membranes displayed a one-month stability confirming its exceptional long-term operational stability and great potential for industrial gas separations.