High-Flux Oil/Water Separation with Interfacial Capillary Effect in Switchable Superwetting Cu(OH)2@ZIF-8 Nanowire Membranes.

Highly ordered architectures with roughness and porous surface are the key challenges toward developing smart superwetting membranes. We prepared switchable superwetting Cu(OH)2@ZIF-8 core/shell nanowire membranes for high-flux oil/water separation as well as simultaneous heavy-metal ions removal in one step. The well-defined Cu(OH)2@ZIF-8 core/shell nanowire grown on copper mesh with average length of ca. 15 μm and diameter of ca. 162 nm exhibits high water contact angle (CA) of ca. 153 ± 0.6°. After modified by ethanol, the membrane holds the reverse superwettability with oil (dichloromethane as an example) CA of ca. 155 ± 0.8° underwater. The separation efficiencies of the membranes are higher than that of 97.2% with a remarkable flux rate higher than 90 000 L m-2 h-1 for the immiscible oil/water mixture. And the removal efficiency for Cr3+ ions at 10 ppb can arrive at 99.2 wt % in the toluene-in-water emulsion. The high performances of the smart superwetting membranes can be attributed to the interfacial capillary effects of the hierarchical Cu(OH)2@ZIF-8 core/shell nanostructures. This work may provide a new insight into the design of smart superwetting surfaces for oil/water separation and target adsorption in one step.