A Cu₂O coated Cu mesh with micro-scale surface structure was produced by a controlled UV-ozone treatment. The modified Cu mesh exhibited superhydrophilicity and underwater superoleophobicity. To achieve switchable wettability, the mesh's superhydrophilicity was converted to superhydrophobicity by application of a self-assembled monolayer (SAM) with stearic acid (SA), which can be repeatedly reversed to its original state (superhydrophilicity and underwater superoleophobicity) by UV treatment that causes SA decomposition. Gravity-driven kerosene/water separation was demonstrated with the separation efficiency remaining over 95% after 20 cycles for both “water-removal” and “oil-removal” separation modes.