Surface and interface engineering provides a powerful tool to tailor the structures and properties of polymer membranes, sharpening their applications in sustainable development. Tremendous progress has been achieved in this field over the past 20 years. In this Perspective, we overview the conventional and emerging strategies for membrane surface engineering and present the current trends in surface and interface engineering for both porous and thin-film composite membranes. For porous membranes, the rise of Janus membranes motivates the evolution from uniform functionalization to asymmetric performance construction. For thin-film composite membranes, the research foci are moving to the surface modification of substrates, the fabrication of nanostructured interlayers, and especially the regulation of interfacial polymerization.

The deepening crisis of freshwater resources has been driving the further development of new types of membrane-based desalination technologies represented by nanofiltration membranes. Solving the existing trade-off limitation on enhancing the water permeance and the rejection of salts is currently one of the most concerned research interests. Here, a facile and scalable approach is proposed to tune the interfacial polymerization by constructing a calcium alginate hydrogel layer on the porous substrates. The evenly coated thin hydrogel layer can not only store amine monomers like the aqueous phase but also suppress the diffusion of amine monomers inside, as well as provide a flat and stable interface to implement the interfacial polymerization. The resultant polyamide nanofilms have a relatively smooth morphology, negatively charged surface, and reduced thickness which facilitate a fast water permeation while maintaining rejection efficiency. As a result, the as-prepared composite membranes show improved water permeance (~30 Lm−2h−1bar−1) and comparable rejection of Na2SO4 (>97%) in practical applications. It is proved to be a feasible approach to manufacturing high-performance nanofiltration membranes with the assist of alginate hydrogel regulating interfacial polymerization.

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