Green, robust self-cleaning superhydrophilic coating and on-demand oil–water separation

[Display omitted] •We developed a new way for simultaneously preparing roughness and hydrophilic groups on the surface.•Sodium periodate (SP) oxidized the phenolic hydroxyl on proanthocyanidin into a quinone group and promoted the deposition of proanthocyanidin on the surface.•At the same time, the SP further oxidized o-quinone groups to the carboxyl functional groups.•Superhydrophilic materials can efficiently separate immiscible oil–water mixtures and oil-in-water emulsions on demand.•The superhydrophilic materials had excellent underwater antifouling properties. Recently, biomimetic modified membranes for oil–water separation have attracted extensive attention. However, complex processing and severe oil fouling have always been the main obstacles to its application. To explore facile and green preparation methods is urgently desired. In this study, a green and facile modification strategy was proposed, when the feature that sodium periodate could promote procyanidin deposition was utilized to prepare superhydrophilic fabrics and superhydrophilic polyvinylidene fluoride membranes to separate oil–water mixtures on demand. This method could simultaneously build a rough structure and introduce polar functional groups on the substrate surface. The prepared materials possessed excellent oil–water separation ability and cycle stability. The flux and efficiency of separating immiscible oil–water mixtures through superhydrophilic fabrics could reach up to 38,100 L·m-2h−1 and 99.8%, while those of separating oil in water emulsion through superhydrophilic polyvinylidene fluoride membranes could be as high as 681 L·m-2h−1 and 99.5%, respectively, showing that the superhydrophilic materials wetted with water had excellent antifouling ability. The superhydrophilic coating was also featured with excellent chemical stability and mechanical durability. The preparation strategy of the superhydrophilic materials provided in this study can promote the development of oil–water separation technology.