Recent Advances in Carbon Nitride Supported Single-Atom Catalysts: Synthesis, Characterization, and Applications for CO2 Photoreduction

Photoreduction of CO2 into value-added chemicals and fuels is a promising green technology for solar-to-chemical conversion. Owing to the atomic utilization, unique metal-support interaction, and unsaturated coordination active sites, single-atom catalysts (SACs) have been attracting great attention in achieving high activity and selectivity of CO2 photoreduction reactions. On the other hand, carbon nitride (C3N4) with abundant periodically unsaturated coordination of nitrogen atoms can serve as an excellent support for anchoring metal single atoms. In this context, extensive research efforts have been paid in C3N4-based SACs for CO2 photoreduction in recent years. In this review, we report the recent advances in C3N4 supported SACs for CO2 photoreduction. We start from the introduction of synthetic strategies of various C3N4 supported metal SACs. Secondly, the main advanced characterization techniques and calculation methods for identifying the single-atoms and their coordination environments of C3N4-based SACs are summarized. Thirdly, some state-of-the-art works on the rational design of C3N4-based SACs and their applications in CO2 photoreduction are introduced. Lastly, we briefly summarize the main challenges and propose important perspectives of C3N4-based SACs in CO2 photoreduction. This review is expected to provide some useful guidelines for the development of efficient and stable C3N4-based SACs for CO2 photoreduction.