Function-Oriented and Waste-Derived Single-Atom Catalysts for Water Purification

Single-atom catalysts (SACs) present distinctive opportunities for environmental catalysis, not simply by maximizing atom utilization, but by enabling function-oriented control over heterogeneous interfacial chemistry in complex and fluctuating water matrices. In practical water purification, their catalytic value lies less in intrinsic activity alone than in their capacity to deliver selective reactivity, tolerance to matrix interference, durability, and system compatibility under realistic operating conditions. This review therefore develops a unified framework that links atomic-level SAC design to the key functional demands of water purification, including reactive-species pathway regulation, pollutant-oriented site design, resistance to deactivation and matrix interference, and system sustainability and compatibility. From this perspective, SACs are discussed as a platform for addressing the growing challenges of selective pollutant removal in interferent-rich waters via site-specific control of reactive species, interfacial microenvironments, and oxidant generation. Waste-derived SACs are further considered as a material-level extension of this concept toward environmental homology, circularity, and deployment-relevant design. By surveying waste-derived supports, metal sources, and fully coderived systems, we illustrate how catalyst synthesis can be coupled with waste management to advance closed-loop remediation. Finally, we outline future directions toward intelligent and adaptive environmental catalysis, where data-driven design and automation may accelerate multiobjective optimization across materials, interfaces, and reactors. More broadly, this Review positions SACs as a conceptual and materials platform for selective, robust, and sustainable water-treatment technologies.