Ultra-robust superwetting hierarchical membranes constructed by coordination complex networks for oily water treatment

Superhydrophilic and underwater superoleophobic (SHL&UWSOB) membranes possess unique advantages in treating oily wastewater. The hydrophilic surface coating and the hierarchical microstructure is significant for the fabrication of SHL&UWSOB membrane, however, the stability of the surface coating remain challenging. In this study, the hydrophilic hierarchical structure was first constructed based on amino-functionalized polyhedral oligosiloxane/proanthocyanidins (POSS-NH 2 /PC) surface coating. Then metal-phenol networks (MPN) was quickly derived from Fe (Ⅲ) and PC networks (FPN). The coordination complex networks formed by POSS-NH 2 /PC cross-linking and FPN synergy construct a hydrophilic hierarchical hybrid layer on poly (vinylidene fluoride) (PVDF) microfiltration (MF) membrane surface. Physicochemical characterizations demonstrate that FPN can greatly restrain the oxidation of phenolic hydroxyl group and reduce the electrostatic repulsion force and enhance the interaction between chain segments, hence, the stability of the coating in strong acidic or alkaline conditions was achieved. The synthesized membrane shows robust superhydrophilicity and underwater superoleophobicity, revealing high efficiency for separation of oil-in-water emulsion in harsh environment, and the oil rejections are over 99.0%. In addition, the resulted membrane has good anti-oil fouling performance even after three-cycles of oil/water separation. The designed membrane lights new prospects in the design of the facile and universality for other superwetting materials.