One-Step Solvothermal Construction of a Heterostructured Ti(OH) ₄ /BFC Membrane with Prewetting-Induced Switchable Wettability for On-Demand Oil–Water Separation

Compared to single-surface-specific wetting materials, prewetting-induced switchable wetting materials offer advantages of simple operation, energy efficiency, and powerful functionality. They can meet operational demands in complex environments and demonstrate considerable potential across various fields. Current prewetting-induced switchable wettability materials are constrained by the preparation materials, fabrication strategies, separation performance, and stability. This paper reports the preparation of Ti(OH) 4 /BFC prewetting-induced switchable wettability (superhydrophilic/submerged superoleophobic and superhydrophilic/submerged superhydrophobic) oil–water separation membranes via a one-step solvothermal method. Ti(OH) 4 utilizes the intermediate (HOOC–CH 2 –OH) as a molecular bridge to bond with BFC, constructing a heterostructure that leads to prewetting-induced switchable wettability. The membrane showed high water and oil fluxes (∼10 4 L·m –2 ·h –1 ) and over a 99% separation efficiency for gravity-driven oil–water mixtures. The chemical bonds connecting Ti(OH) 4 and BFC contribute to the strong mechanical stability of the separation membrane. Prewetting induces a stable liquid film on the Ti(OH) 4 /BFC surface, enabling durable and high-flux oil–water separation.