Tuning monomer spatial configuration for high-performance polyesteramide loose nanofiltration membranes toward antibiotic separation

Polyesteramide (PEA) thin-film composite (TFC) membranes have emerged as promising candidates for antibiotic separation from water, yet rational monomer design to overcome the permeability-selectivity trade-off remains challenging. Herein, three tetrafunctional phenol-amine monomers with distinct spatial configurations—rigid twisted 2,2-bis(3-amino-4-hydroxyphenyl)propane (BAP), rigid rotatable 3,3-dihydroxybenzidine (HAB), and bulky side-group-containing 9,9-bis(3-amino-4-hydroxyphenyl)fluorene (BAF)—were respectively reacted with trimesoyl chloride via interfacial polymerization to fabricate novel PEA loose nanofiltration (LNF) membranes. Monomer configuration governed membrane morphology, extent of crosslinking reaction, pore architecture, and surface properties. DFT calculations and UV-Vis diffusion kinetics elucidated monomer reactivity and diffusion behavior. Among the three membranes, NF-HAB, derived from HAB, demonstrated the optimal overall performance. It achieved a high water permeance of 50.5 L m −2  h −1 ·bar −1 while maintaining excellent rejection rates of both weakly negative antibiotics (e.g., 92.0% for cefoperazone) and their negatively charged sodium salts (e.g., >96% for ceftriaxone sodium and cefoperazone sodium). Furthermore, all PEA membranes exhibited superior chlorine resistance and antifouling performance. This work establishes a structure-property-mechanism relationship, demonstrating that tuning monomer spatial configuration enables synergistic optimization of permeance and selectivity for high-performance PEA LNF membranes in antibiotic separation.