Harnessing surface chemistry: a comprehensive review on the role of functional groups in antifouling membrane design.

Membrane fouling remains a major barrier to reliable and cost-effective water treatment, motivating surface engineering strategies that suppress foulant attachment while preserving permeability and selectivity. This review critically examines antifouling membrane design through a functional-group-centred framework, focusing on grafted monomers and polymer architectures that regulate interfacial hydration, charge, polarity, and steric interactions. Oxygen-, nitrogen-, sulfur-, phosphorus-containing, zwitterionic, and multifunctional chemistries are comparatively evaluated across organic fouling, biofouling, colloidal deposition, and scaling. The analysis demonstrates that antifouling performance is governed not only by functional group identity but also by grafting density, chain conformation and mobility, spatial uniformity, and anchoring stability. Oxygen-rich and zwitterionic interfaces suppress foulant attachment primarily through strong hydration, while nitrogen-containing chemistries offer tuneable charge and antimicrobial functionality. Sulfur- and phosphorus-containing groups provide additional hydration and ion-coordination capabilities. However, no single chemistry is universally optimal across feed conditions. Major barriers to translation include reliance on short-term single foulant testing, limited cyclic cleaning and ageing studies, and inadequate verification of long-term graft stability. Future research should therefore prioritise durable multifunctional interfaces, standardised testing under realistic conditions, scalable grafting routes, and data-driven optimisation of structure-property-performance relationships.