Light‐Programmable Interfaces: From Molecular Photoswitching to Adaptive Membrane Separations

ABSTRACT Membrane‐based separation is widely applied in water purification, gas processing, and biomedical systems, but conventional membranes often suffer from fixed pore structures and static surface chemistries that limit selectivity and make them prone to fouling. Light‐responsive interfaces offer a promising solution by enabling reversible control of wettability, surface charge, and permeability. Incorporating photochromic switches such as azobenzene (AZO), spiropyran (SP), diarylethene (DAE), donor–acceptor Stenhouse adducts, and photoacid systems into polymeric matrices, porous frameworks, and hybrid composites allows precise modulation of interfacial properties under light stimuli. This capability provides new opportunities to enhance antifouling performance, improve separation selectivity, and realize programmable transport. Nevertheless, challenges remain, including limited light penetration in thick or turbid media, chromophore fatigue under repeated cycling, and difficulties in scaling fabrication strategies. This review adopts an interface‐centered perspective to compare design approaches such as covalent grafting, supramolecular assembly, mixed‐matrix integration, and photografting. Representative applications in water purification, gas separation, oil–water separation, and drug delivery are highlighted. By linking molecular photoswitch chemistry with interfacial responses and separation performance, this study outlines promising directions for developing durable, multifunctional, and scalable light‐responsive membranes for next‐generation separation technologies.