Controllable synthesis of M₁-N_{<italic>x</italic>}-C catalysts and research progress in reduction of CO₂

Under the dual-carbon context, the conversion of CO2 into high-value products has emerged as a prominent research focus in the global chemical and environmental science communities. Among various catalysts, metal single-atom nitrogen-carbon (M1-Nx-C) catalysts have garnered significant attention due to their exceptional atomic utilization efficiency and superior catalytic performance. However, the highly tunable coordination environments of M1-Nx-C catalysts complicate the establishment of clear structure-activity relationships between active site configurations and CO2 hydrogenation performance. This review systematically categorizes coordination structures of M1-Nx-C catalysts in CO2 hydrogenation reduction, including conventional symmetric coordination (M1-N4-C), axial coordination (M1-Nx-Z), and defect/unsaturated coordination structures (M1-Nx-C). Subsequently, we analyze synthesis strategies for materials with distinct coordination architectures, with special emphasis on the adsorption-activation mechanisms of reactants and reaction intermediates during CO2 hydrogenation mediated by different coordination configurations. Finally, we outline current challenges and potential prospects for M1-Nx-C catalysts in advancing CO2 hydrogenation technologies.