Robust superhydrophilic and underwater superoleophobic membrane optimized by Cu doping modified metal-organic frameworks for oil-water separation and water purification

The traditional oil-water separation methods suffer from many problems such as low separation efficiency, high energy consumption, and rapid contamination by oil. We fabricated superhydrophilic and underwater superoleophobic stainless steel mesh (SSM), which was modified by copper mesh (CM) doped UiO-66-NH2, named SSM/UiO-66-NH2/CMn, for efficient oil-water separation and organic matter degradation. Our fabrication strategy mainly includes the growth of structural tunable metal-organic frameworks (MOF, UiO-66) on metal meshes via hydrothermal reaction. The UiO-66 was doped and modified by reusable copper mesh, which enhanced the hydrophilicity and photocatalytic properties of the mesh. The SEM, XRD, AFM, FTIR, and XPS characterizations demonstrated that the meshes were successfully prepared and showed a rough structure surface. In virtue of the special wetting and robustness, the prepared meshes could maintain superhydrophilicity and underwater superoleophobicity with underwater oil contact angle (UWOCA) above 150° after oil/water separation at extreme conditions, including high salt concentrations, low/high temperatures, presence of organic solvents, alkaline and acidic solutions, sandpaper friction, and long-time UV irradiation. Even under harsh conditions, the mesh showed an excellent oil-water separation efficiency of up to 99.7%. Moreover, the fabricated meshes can degrade dye pollutants under visible light with a degradation rate of 99.5% within 80 min, which solves the dependence of traditional photocatalysts on UV and improves solar energy utilization. This research paves the way for preparing super wetting membranes for oil-water separation and organic matter degradation in actual complex oily wastewater.