Liquid–liquid–solid interfacial polymerization approach to rapid fabrication of large-sized, self-standing structured COF membranes†

Abstract

Covalent organic framework (COF) membranes, with their customizable chemical structures and regular nanochannels, are widely used for separation. However, challenges remain in the rapid and high-yield fabrication of robust, self-standing, flexible, large-sized, highly crystalline COF membranes, especially as self-standing or supported membranes. Here, we introduce a liquid–liquid–solid interfacial polymerization technique at high temperature for the rapid production (in a few hours) of large-sized, robust, flexible, and thickness-adjustable highly crystalline self-standing all COF membranes with hierarchical structure in which a nano COF membrane is integrated on COF hollow fiber networks of the same material, achieving impressive mechanical stability (tensile strength ∼23 MPa), which is maintained even after 500 bending cycles and 80% compression. Furthermore, we demonstrate the universality of this technique by preparing various imine-linked COFs on different porous substrates. Laboratory filtration experiments produced excellent results, highlighting the considerable potential of COF membranes for use in industrial wastewater purification applications going forward.