Covalently engineered light-responsive GO–PES nanohybrid membranes with enhanced antifouling and transport properties

Natural organic matter (NOM) fouling remains a major limitation in ultrafiltration membranes, motivating the development of hybrid materials with tunable interfacial properties and improved structural robustness. Here, we report a light-responsive graphene oxide–polyethersulfone (GO–PES) nanohybrid membrane fabricated by incorporating covalently grafted azobenzene–silane–functionalized GO (AZO-fGO) nanosheets into a PES matrix via non-solvent induced phase separation. Covalent functionalization enhances nanosheet dispersion and interfacial compatibility, leading to notable improvements in membrane hydrophilicity, mechanical strength, and thermal stability. The optimized membrane exhibits a high pure-water flux of 296.4 L m⁻² h⁻¹, ~ 90% rejection of NOM, and a flux recovery ratio of 91.9%, indicating strong antifouling performance. Under continuous filtration of real municipal wastewater for 72 h, the membrane maintains stable flux and rejection with minimal irreversible fouling. In addition, reversible azobenzene photoisomerization enables modest but repeatable tuning of water transport under UV and visible light without compromising structural integrity. These results demonstrate how covalent nanohybrid engineering can integrate mechanical reinforcement, antifouling functionality, and external responsiveness within a single composite membrane, offering a versatile design strategy for adaptive ultrafiltration materials.