Diffusion-Regulated Confined Interfacial Polymerization for Precise Pore Engineering in Tight Ultrafiltration Membranes

The selective separation of small organic molecules from high-salinity wastewater remains challenging due to the trade-off between organic rejection and salt permeability in conventional membrane processes. Tight ultrafiltration (TUF) membranes, with tunable pore sizes below 10 nm, provide a promising structural window to overcome this limitation. Herein, a water-phase monomer anchoring-enabled confined interfacial polymerization strategy is proposed for precise pore regulation in TUF membranes. A highly hydrophilic D-sorbitol is employed as the aqueous-phase monomer, whose strong hydrogen-bonding interactions with water retard interfacial diffusion and confine polymerization predominantly within membrane pores, enabling in situ polyester formation and pore-size narrowing. Molecular dynamics simulations reveal the diffusion-regulated confinement mechanism. The resulting membrane exhibits an average pore size of 1.69 nm (radius) and achieves a high separation factor of 239.54 for Congo red/NaCl, with rejection efficiencies exceeding 90% for bacitracin and tetracycline hydrochloride. Moreover, it maintains >99.0% CR rejection after 96 h sodium hypochlorite exposure and shows excellent antifouling property, benefiting from the multi-hydroxyl and steric structure of D-sorbitol. This work establishes a diffusion-regulated interfacial polymerization paradigm for high-performance organic-salt separation. • Confined interfacial polymerization enables precise pore control in TUF membranes. • Hydrogen-bond anchoring regulates diffusion and confines polymer growth in pores. • A 3.58 nm pore size and 239.54 selectivity factor are achieved for CR/NaCl. • Steric hindrance and ester linkages ensure chlorine resistance and antifouling.