A smart superomniphobic membrane with switchable UV-cleaning and dark-healing for sustainable membrane distillation

Membrane fouling remains a critical barrier to the sustainable application of membrane distillation (MD) for organic wastewater treatment. To address this, we developed a superomniphobic membrane with switchable UV-cleaning and dark-healing capabilities. The 17F-STNRs/PVDF membrane was fabricated by grafting SiO₂-supported TiO₂ nanoarrays (STNRs) onto a PVDF substrate via silane coupling followed by fluorination. It exhibited exceptional stability and anti-wetting performance, with water and ethylene glycol contact angles exceeding 153° and sliding angles below 10°. In 24-h MD tests using simulated wastewater containing humic acid (HA), sodium dodecyl sulfate (SDS), and bovine serum albumin (BSA), it showed significantly enhanced anti-fouling performance, achieving flux retention rates 40.2%, 62.9%, and 10.8% higher, respectively, than pristine PVDF while maintaining near complete salt rejection. In a 72-h MD test with 3.5 wt% NaCl solution, the modified membrane exhibited exceptional stability with an extremely low flux decay rate of merely 12.3%. Crucially, the membrane enabled efficient UV-triggered self-cleaning, removing foulants within 4 h of exposure, and fully recovered its initial superomniphobicity after 24 h in the dark, demonstrating stable multi-cycle (≥5) reusability. Mechanistic studies combining EDS, XPS experimental analysis and DFT calculations revealed that this switchable behavior was driven by UV-induced radical-catalyzed oxidation followed by dark-assisted wettability recovery. This work demonstrates how integrating photocatalytic cleaning with reversible surface regeneration enables in situ, energy-efficient membrane maintenance, providing a feasible strategy toward sustainable MD.