pH-responsive ZnNb2O6/BiOBr-based membranes with photocatalytic, oil-water separation, and flame-retardant multifunctionality

Responsive superhydrophobic films have gained increasing interest for their tunable wettability and adaptive functionality, yet their poor environmental stability limits use in complex wastewater treatment. Herein, a multifunctional membrane integrating pH-responsive wettability, photocatalytic activity, efficient oil–water separation, and strong flame retardancy is reported. A ZnNb 2 O 6 /BiOBr composite with superior photocatalytic activity achieved 80% degradation of hydrochloric tetracycline (HTC). Based on this material, a ZnNb 2 O 6 /BiOBr/ODA patterned coating strategy was developed to construct a pH-responsive superwetting membrane capable of reversible transitions between superhydrophobic and superhydrophilic states, serving as a conductive/non-conductive liquid identification based on wettability differences and response under extremely acidic (pH ≤ 3) conditions indicator. The membrane also exhibits remarkable flame suppression, >97% oil–water separation efficiency, and excellent reusability under harsh conditions, including crude-oil-contaminated seawater. This work provides a robust and intelligent membrane platform for environmental monitoring, wastewater purification, oil spill remediation, and fire-safe applications.