Carbon dots-assisted cobalt ions anchored on graphitic carbon nitride enables highly efficient photocatalytic CO₂ conversion

Artificial photosynthesis that converts solar energy and CO₂ into value-added chemicals such as CO represents a highly promising route for sustainable energy production. However, the inherent limitations of graphitic carbon nitride (g-C₃N₄), including the lack of efficient active sites and sluggish charge transfer, significantly hinder its photocatalytic CO₂ reduction performance. Herein, a novel strategy is proposed in which amino-functionalized carbon dots (pCDs) mediate the construction of Co-N coordination active centers on g-C₃N₄ nanosheets (Co-5pCDs-g-C₃N₄). Advanced characterizations reveal that Co ions are anchored on the surface of the pCDs through Co-N coordination with amino groups, while the structural incorporation of the pCDs effectively reduces the lateral dimensions of the g-C₃N₄ nanosheets. This structural design markedly enhances charge-carrier separation within Co-5pCDs-g-C₃N₄, promotes charge migration toward the Co-N active centers, and enables highly selective CO₂ to CO conversion. Notably, Co-5pCDs-g-C₃N₄ achieves a remarkable CO production rate of 616.1 μmol·g^–1·h^–1, 91 times higher than Co-g-C₃N₄ with a CO selectivity of 92%. Femtosecond transient absorption (fs-TA) spectroscopy provides crucial mechanistic insights into the improved performance. The incorporation of pCDs significantly prolongs the average lifetime of photogenerated charge carriers, whereas the introduction of Co further extends this lifetime by promoting charge separation and suppressing recombination. Owing to the dual functions of pCDs in modulating charge dynamics and tailoring the coordination environment, the resulting catalyst demonstrates markedly enhanced photocatalytic CO₂ reduction performance, underscoring its strong potential for advanced solar-driven catalytic applications.