Layer-by-layer self-assembly metal-phenolic network coatings for universal modification of porous substrates for efficient oil/water separation and photo-Fenton-like pollutant degradation

Industrial oily wastewater treated with membranes typically contains recalcitrant contaminants such as emulsified oil droplets, dyes, and antibiotics, which readily form a stubborn “oil-cake” layer on membrane surfaces, causing flux decline and irreversible fouling. Therefore, achieving the synergy of high-efficiency separation with in situ contaminant degradation has become a central challenge in membrane materials design. In this study, a layer-by-layer self-assembly strategy applicable to various porous substrates is developed. Specifically, tannic acid/regenerated silk fibroin (TA/SF) constructs a bioadhesive layer; bimetallic Fe/Cu coordination forms a stable metal-phenolic network (MPN), which markedly enhances catalytic-site stability and electron-transfer efficiency; and a durable hydrogel layer is then generated via polyvinyl alcohol (PVA) hydrogen-bond crosslinking,yielding a TA/SF–Fe/Cu MPN–PVA composite coating (TSMP). This three-layer synergistic coating—“adhesive fixation, metal coordination, and hydrogel crosslinking”—endows the membrane surface with superhydrophilicity/underwater superoleophobicity, anti-fouling, and self-cleaning capability. Under visible light/H₂O₂ conditions, the coating activates a photo-Fenton-like cycle, enabling in situ oil removal and pollutant degradation on the membrane. The strategy exhibits excellent compatibility and structural stability across distinct substrates, such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and natural palm bark. In pressure-driven separation of oil-in-water emulsions, TSMP-modified membranes achieved a flux of 1201.4 L m −2  h −1  bar −1 and a separation efficiency of 99.85%. After photo-Fenton self-cleaning, the flux recovery ratio (FRR) reached up to 90.37%. Meanwhile, TSMP-modified membranes exhibited excellent degradation efficiencies toward organic pollutants, including methylene blue, methyl orange, and representative antibiotics, while maintaining good cycling stability. Hence, the constructed supramolecular fiber-polyphenol functional coating offers a low-energy, scalable, and universal separation-degradation solution for complex oily organic wastewater.