High-performance loose nanofiltration membranes with excellent antifouling properties for dye/salt separation

Polyethersulfone (PES) is a promising material for the development of loose nanofiltration (LNF) membranes. However, conventional PES membranes produced by the nonsolvent-induced phase inversion (NIPS) method suffer from low permeance and are prone to fouling. Here, we develop an ultrapermeable LNF membrane with excellent antifouling properties from an in situ dissolved PES in a colloidal COF using a recently developed approach that combines NIPS with the combined crystallisation and diffusion (CCD) technique, named NIPS-CCD. The integration of the anionic COF DABA-TFP not only imparted a negative charge to the membrane but also enhanced the membrane hydrophilicity. As a result, the water permeance of the COF-enhanced PES membranes was 10–100 times greater than that of commercial LNF membranes, with a flux recovery ratio exceeding 80 %. Performance tests involving dye-salt separation revealed a molecular weight cut-off (MWCO) for dyes of approximately 800–1000 Da while maintaining high salt permeability. This study offers a promising approach for manufacturing advanced PES-based membranes for loose nanofiltration applications.