Ceramic hollow fibre supported covalent organic framework membranes prepared by direct interfacial polymerisation -potential for efficient dye removal from wastewater

Covalent organic frameworks (COFs) have emerged as promising membrane materials, owing to their tunable pore size and ease of functionalisation with potential applications in water purification and organic solvent nanofiltration. However, current COF membranes fabricated via interfacial polymerisation have primarily been limited to polymeric flat sheet substrates, which may not provide optimal mechanical stability over extended periods, as the COF materials are inherently brittle due to their rigid structures and hence prone to damage when applied them on flexible polymeric substrates. In this study, we utilized direct interfacial polymerisation to fabricate imine-linked COF-LZU1 membranes on pre-designed ceramic hollow fibres for efficient dye removal from aqueous solutions. The key parameters, i.e., reaction time and choice of organic solvents, were investigated to achieve a highly crystalline and defect-free COF layer. The resultant membranes exhibited a high pure water permeance of 28.5 L m−2 h−1 bar−1 with a rejection rate of over 90% for dyes with a molecular weight exceeding 500 g mol−1, highlighting the potential of the ceramic hollow fibre supported COF membranes for enhanced process intensification, i.e. high surface-to-volume ratio, better mechanical stability and structural integrity for long-term operations.