Superhydrophilic membranes have drawn much attention owing to

their outstanding anti-fouling performance and ultrahigh permeation

flux for wastewater treatment and oil–water separation. Since most

widely used polymer membranes have high intrinsic hydrophobicity,

a universal approach for superhydrophilic modification is highly

required. Yet, how to simply transform highly hydrophobic

membranes into superhydrophilic ones is still a challenge. Herein, we

develop a one-step and general strategy to achieve the hydrophobicto-superhydrophilic transformation of commercial membranes on the

basis of catechol chemistry,i.e., co-deposition of tannic acid (TA) and

3-aminopropyltriethoxysilane (APTES) in aqueous solution. Owing to

the distinct adhesion properties of TA and the reaction between the

oxidative product of TA and the hydrolysis product of APTES, hydrophilic and hierarchical layer-colloidal nanospheres can bein situ

assembled on various highly hydrophobic membranes including polyvinylidene fluoride (PVDF), polypropylene (PP), polytetrafluoroethylene (PTFE), copper mesh, stainless steel wire, and nylon mesh.

The resulting superhydrophilic membrane can realize high-efficiency

separation of various oil-in-water emulsions.