Microenvironment engineering in carbon nitride supported metal single atoms for solar driven aqueous pollutant removal

• Present innovative strategies for designing nanostructured C 3 N 4 supported SACs. • Summarize regulation approaches for tailoring SA microenvironments in carbon nitride. • Disclose C 3 N 4 -SAC coordination effect on ROS generation in photocatalytic degradation. • Explore challenges and perspectives in optimizing microenvironments of C 3 N 4 -SACs. Photocatalytic technology has emerged as a promising solution for tackling environmental pollution, however, the development of efficient and durable catalysts remains a challenge. Carbon nitride-based single atom catalysts have garnered considerable attention for their high metal utilization and tuneable coordination environments, making them efficient photocatalysts. More importantly, tailoring the microenvironment of single atoms within carbon nitride materials holds great potential for enhancing reactive oxygen species (ROS) generation and improving pollutant removal efficiency, a topic that has yet to be thoroughly reviewed. As such, this review timely provides a comprehensive examination of microenvironment modulation in SACs-CN for efficient photodegradation of aqueous pollutants. It begins with an overview of commonly used synthesis approaches, followed by an in-depth discussion of key engineering strategies, including single metal regulation, coordination environment engineering, defect modulation, interlayer insertion, heteroatom doping, and cluster decoration. We also examine the influence of varied microenvironment of metal centre on the evolution of ROS and overall photocatalytic efficiency. Recent advancements in optimizing the chemical environments in SACs-CN are highlighted, alongside current challenges and future directions in this promising field. This work elucidates the relationships among the coordination of active centres, ROS selective generation, and pollutant removal, offering valuable insights into the design of high-performance photocatalysts for solar-driven wastewater treatment.