Covalent triazine framework-based porous mixed matrix membranes for highly efficient dye/salt separation

Mixed matrix membranes (MMMs) incorporating porous covalent organic frameworks (COFs) as fillers have garnered significant attention in membrane separation for water purification. Covalent triazine frameworks (CTFs) possess high thermochemical stability, an inherent triazine conjugate structure, and tunable pore size. Despite these attributes, CTFs have been underutilized in MMMs. In this study, CTF-based porous MMMs were fabricated by blending 4,4′-biphenyldicarbonitrile (BPCN) monomer with polyacrylonitrile (PAN) and employing titanium dioxide nanoparticles (TiO2 NPs) as a pore-forming agent. The nature of PAN also makes the mixed matrix membranes have better hydrophilicity and mechanical properties. The optimized CTF-MMM exhibited an impressive water permeance of ∼ 204 L m−2 h−1 bar−1, accompanied by a remarkable dye rejection of ∼ 99 % and a low salt rejection. Moreover, the CTF-MMM demonstrated sustained water permeance and separation performance even after 48 h. This work introduces a synthesis strategy for fabricating high-performance CTF-based porous mixed matrix membranes, showcasing significant potential for applications in dye/salt separation.