Carbon dots-assisted cobalt ions anchored on graphitic carbon nitride enables highly efficient photocatalytic CO 2 conversion

Abstract 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.