Surface molecular engineering of membranes for oil-in-water emulsion separation: Where we are and where to go

Abstract

Membrane separation is an effective strategy for treating oil/water emulsions, in which surface chemistry and microstructure play crucial roles. In this Perspective, we summarize advances in oil/water emulsion separation membranes from the perspective of surface molecular engineering. We first elucidate the interfacial physicochemical principles and molecular-level design parameters that govern surface wettability and capillary behavior. Strategies for constructing superhydrophilic/underwater superoleophobic membranes via organic and organic–inorganic molecular engineering are then systematically summarized. Beyond conventional symmetric designs, we discuss the concept of Janus membranes and their distinct demulsification-based separation mechanisms, together with emerging antifouling strategies that extend beyond traditional wettability control. Finally, key challenges in this field are highlighted to identify opportunities for next-generation membranes compatible with practical operation.