Enhanced performance of mixed matrix membrane by incorporating a highly compatible covalent organic framework into poly(vinylamine) for hydrogen purification

• COF shows good compatibility with PVAm.
• The PVAm/COF membrane possesses the character of CO2 preferential adsorption.
• The PVAm/COF membrane shows good CO2/H2 performance.

In this work, a highly compatible covalent organic framework (COF) was incorporated into poly(vinylamine) (PVAm) to enhance membrane performance. An imine-based COF with a 2-dimensional network was synthesized via a facile nucleophilic reaction. The PVAm/COF mixed matrix membrane (MMM) was prepared by casting PVAm-COF dispersion on polysulfone (PSf) ultrafiltration membrane, and the resulting membrane was applied for CO2/H2 separation. Suitable pores are incorporated into the MMM to enhance the diffusivity of CO2, and simultaneously amino groups of PVAm are adhered to the pore walls due to the hydrogen bonds between the polymer and the filler, thus enhancing CO2 preferential adsorption through reversible reaction. A notably improved gas separation performance of PVAm/COF membrane could be attained compared to PVAm membrane. With 10 wt% COF incorporated, the as-prepared MMM shows a CO2/H2 selectivity of 15 and a CO2 permeance of 396 GPU at 0.15 MPa. These results suggest that COFs with various structures have potential to possess good compatibility with polymers, thereby enabling fabrication of COF-based MMMs with superior performance.

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