Synthesis of stable COF-300 nanofiltration membrane via in-situ growth with ultrahigh flux for selective dye separation

Covalent organic frameworks (COFs) hold great promise for constructing the new-generation molecular sieving membranes due to their robust, ordered and versatile architectures. However, COF membranes generally suffer from the discontinuous crystal layer and the poor particle adhesion on the substrate, limiting their widespread application. In this work, a facile in-situ growth method was proposed under solvothermal conditions to prepare a high-quality COF-300 membrane supported on the NH2-modified porous ceramic support. A series of characterizations have demonstrated that the pre-grafting with 3-aminopropyltriethoxysilane (APTES) and tereph-thalaldehyde (TPA) served as a surface anchor for covalent linkers between the COF-300 membrane and the ceramic support, while the dense and uniform COF-300 layer was obtained by the in-situ growth. The COF-300 layer provides the high-efficiency transport pathways for water molecules and simultaneously effective rejection for dye molecules. As expected, COF-300 membrane showed a remarkable flux of 395.3 L m(-)(2) h(-1) at 5 bar, which is 5-10 times significantly higher than those of state-of-the-art nanofiltration membranes with similar rejection, and a high rejection of 97.4% for Chrome black T (molecule weight of 461 g mol(-1)). Importantly, benefiting from the high-quality COF-300 layer, an outstanding stability up to 90 h was realized. This in-situ growth method can speed up the paces toward practical applications of COF membranes in the future.