Ultra-rapid preparation of large-area high-crystallinity covalent organic framework membranes

It has been challenging to rapidly prepare high-crystallinity covalent organic framework (COF) membranes particularly in large areas because their crystallization often requires extensive time spent on trial and error and screening. Here, we have developed a reverse-phase microemulsion interfacial polymerization to ultra-rapidly prepare COF membranes in tens of seconds. By creating a special ionic liquid/acetic acid aqueous microemulsion, where the reactive monomers are orderly prearranged within the ionic liquid network, the polymerization and crystallization can concurrently proceed at the phase interface under confined spatial conditions. Meanwhile, the water by-products are promptly encapsulated by the reverse-phase microemulsion, significantly accelerating the polymerization reaction. Using the scraping-assisted process, a large-area high-crystallinity TbPa-COF composite membrane (0.4 × 1.0 m) has been successfully prepared, and the TbPa-COF membrane exhibits high permeability (111.3 L m^-2 h^-1 bar^-1), achieving a bioprotein desalination rate of up to 98% after six cycles, outperforming commercial benchmark membranes (82%). Therefore, through systematic investigation of the ultra-rapid growth mechanism of COF membranes, our work represents a significant milestone for advancing large-area highly crystalline COF membranes for use in practice.