Robust functional Janus nanofibrous membranes for efficient harsh environmental air filtration and oil/water separation

The massive discharge of industrial waste gas and oily wastewater seriously harms the ecological environment and human health. It still remains a tremendous challenge for researchers to develop robust functional materials to control air pollution and purify oily wastewater in actual harsh environments. Herein, a polyacrylonitrile (PAN)@TiO 2 /poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)@SiO 2 nanofibrous (PTPS NF ) Janus membrane was successfully prepared by sequential electrospinning strategy. Due to its unique bi-layer structure and synergistic effect of multiple components, the composite filter could overcome the trade-off effect of high filtration efficiency and low air resistance and realized filtration efficiency of 99.7 % (PM 0.3 removal) with a pressure drop of 27 Pa. The combination of the hygroscopic PAN@TiO 2 layer and the self-cleaning PVDF-HFP@SiO 2 layer endowed the Janus filter obvious advantage in the field of personal protection. Meanwhile, the PTPS NF membranes still remained excellent air filtration performance after strong acid/alkali treatments. Furthermore, due to its asymmetric wettability , the PTPS NF Janus membranes emerged switchable oil/water separation ability, which could efficiently separate different oil/water mixtures and emulsions with high flux and separation efficiency. Therefore, the robust functional Janus nanofibrous filter offers fascinating application prospects in harsh environmental air filtration and oil/water separation.