Substrate-independent surface/interface engineering for efficient water treatment membranes

Conventional separation membranes, in particular polymeric membranes, are typically constrained by permselectivity owing to their strong hydrophobicity, high fouling propensity, poor chemical stability, and broad pore size distribution. Traditional modification methods are substrate dependent, significantly featuring cumbersome operations, limited substrate compatibility, and low environmental benignity. This review focuses on six innovative substrate-independent membrane surface engineering techniques—plasma treatment, polydopamine (PDA) coating, polyphenol coating, aminomalononitrile (AMN) coating, atomic layer deposition (ALD), and protein coating—all of which feature universal substrate adaptability regardless of the chemical composition, physical state, or initial properties of the substrate. This study elucidates their distinct reaction mechanisms, such as plasma activation via high-energy particles and oxidative self-polymerization of monomers, links these mechanisms to enhanced membrane performance, compares their core merits and practical drawbacks, and highlights their applications in seawater desalination, oil–water separation, and wastewater purification. Future research should prioritize material–process coinnovation to develop low-cost, highly stable, smart-responsive coatings, thereby providing scalable green solutions for advancing high-performance membranes to address critical global water security challenges.