Regenerable fluorine-free superhydrophobic membranes via synergistic interfacial engineering for oily PM filtration

Developing high-efficiency air filters capable of withstanding complex contaminants such as oily aerosols and high humidity without irreversible fouling remains a formidable challenge. Herein, a robust, fluorine-free superhydrophobic nanofiber membrane (MO/PVDF) was fabricated by synergizing moisture-induced phase separation with thiol-ene click chemistry. This dual-strategy approach constructed a hierarchically rough architecture stabilized by covalently grafted hydrophobic molecular brushes. The resulting membrane exhibits a water contact angle >151° and robust repellency towards low-surface-tension liquids including ethylene glycol. This effectively inhibits the capillary wicking of oily particulate matter, thereby transforming the filtration mechanism from a failure-prone depth filtration regime to a sustainable surface filtration mode. Consequently, the membrane maintains a filtration efficiency > 99.7% for oily PM 0.3 (particulate matter in the air with a diameter less than or equal to 0.3 micrometers) with a minimal increase in pressure drop. Under high-humidity conditions, the engineered low-adhesion surface facilitates a transition from film-wise to drop-wise condensation, enabling a spontaneous self-cleaning effect. Furthermore, in industrial-scale pulse-jet dust filtration tests, the membrane demonstrates exceptional fouling reversibility and a passive cake detachment mechanism, retaining a high dust stripping efficiency (> 86%) and structural integrity after 10,000 aging cycles. This work establishes a scalable and fluorine-free interfacial design paradigm for next-generation air filtration media operating under harsh, oily, and humid environments.