Rational design of carbon-nitrogen based cluster catalysts for energy conversion applications.

Atomically precise cluster catalysts, composed of supported metal or metal oxide clusters, have emerged as a rapidly developing frontier in heterogeneous catalysis, bridging the advantages of single-atom catalysts (SACs) and traditional metal nanoparticles. Among various supports, carbon nitride (CN)-based materials have attracted significant attention due to their tunable electronic structures, abundant coordination sites, and strong metal-support interactions. These features facilitate the stabilization of ultrasmall clusters with well-defined coordination environments and dynamic reactivity under operating conditions. This review systematically summarizes recent advances in CN-supported metal and metal oxide clusters for key energy conversion reactions, including the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), nitrate reduction reaction (NO3RR), and carbon dioxide reduction reaction (CO2RR). We emphasize how the synergistic effects among the cluster composition, size, synthesis strategy, and CN coordination environment govern catalytic activity and selectivity through charge redistribution and multi-site cooperation. Finally, current challenges and future opportunities in the rational design and structural stabilization of CN supported cluster catalysts are discussed, aiming to guide their further development toward practical applications in sustainable energy conversion.