Enhancing Permelectivity and Chlorine Resistance of Thin-Film Nanocomposite Nanofiltration Membranes via β-Cyclodextrin@g-C3N4 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. Highlights Membrane shows 2.7× water flux (15.30 L·m −2 ·h −1 ·bar −1 ) and 98.18% Na 2 SO 4 rejection. Hydrophilic –OH/–NH 2 improves antifouling; N–H bonds scavenge Cl radicals via sacrifice. High selectivity for NaCl/Na 2 SO 4 ( α = 47.27) via monovalent/divalent ion separation. PCDN membrane achieves > 90.05% FRR, exhibiting excellent antifouling durability.