Multifunctional Switchable Nanocoated Membranes for Efficient Integrated Purification of Oil/Water Emulsions

Surfaces with unusual under-liquid dual superlyophobicity are attractive on account of their widespread applications, but their development remains difficult due to thermodynamic contradiction. Additionally, these surfaces may suffer from limited antifouling ability, which has restricted their practical applications. Herein, we report a successful in situ growth of a hybrid zeolitic imidazolate framework-8 and zinc oxide nanorod on a porous poly(vinylidene fluoride) membrane (ZIF-8@ZnO-PPVDF) and its application as a self-cleaning switchable barrier material in rapid filtration for emulsified oily wastewater. The novel ZIF-8@ZnO-PPVDF exhibits superior mechanical strength, reversible under-liquid dual superlyophobicity, photocatalytic self-cleaning property, and an effective alternate separation capacity toward both oil-in-water (O/W) and water-in-oil (W/O) emulsions with ultrahigh fluxes and efficiencies (>99%). By simply using a "bait-hook-eliminate" method to separate the O/W emulsions containing soluble organic pollutants, we demonstrate that the ZIF-8@ZnO-PPVDF can achieve stable separation fluxes over 600 L m^-2 h^-1 with high efficiencies and be completely/nondestructively regenerated by visible-light irradiation after each cycle. This study would demonstrate a new approach to prepare an under-liquid dual superlyophobic revivable membrane for various applications.