Enhancing Permelectivity and Chlorine Resistance of Thin‐Film Nanocomposite Nanofiltration Membranes via β‐Cyclodextrin@g‐ C 3 N 4 Nanosheets

Conventional polyamide nanofiltration membranes face the dual challenges of chlorine‐induced degradation and the permeability–selectivity trade‐off. In this study, a thin‐film nanocomposite membrane was fabricated by incorporating β‐cyclodextrin‐functionalized g‐C 3 N 4 nanosheets into the polyamide layer via interfacial polymerization. The β‐CD@g‐C 3 N 4 nanosheets provide additional water transport pathways and reduce mass transfer resistance through their hydrophilic groups, β‐CD cavities, and intrinsic triangular nanopores. The optimized PCDN‐3 membrane achieved a water permeance of 15.30 L·m −2 ·h −1 ·bar −1 , 2.7 times that of the pristine membrane, while maintaining a Na 2 SO 4 rejection of 98.18% and a NaCl/Na 2 SO 4 separation factor of 47.27. Notably, the N–H groups on g‐C 3 N 4 act as sacrificial sites for active chlorine, resulting in only a 0.05% increase in salt rejection after exposure to 12,000 ppm·h active chlorine, demonstrating exceptional chlorine stability. Fouling experiments confirmed the composite membrane's excellent antifouling performance. This “cyclodextrin–carbon nitride” strategy provides a promising approach for developing nanofiltration membranes with high permeability, superior chlorine resistance, and robust antifouling properties.