Nitrogen-doped carbon dots as acid-base bifunctional and efficient catalysts for the cycloaddition of CO with epoxides

Carbon dots with good photoelectric properties are usually used as photocatalysts and electrocatalysts, but the good catalytic performance of carbon dots as nanomaterials for thermal catalysis is ignored. Herein, the application of novel efficient catalysts based on carbon dots for the transformation of carbon dioxide (CO 2 ) to carbonates under solvent-free conditions is described. Carbon dots containing carboxyl, hydroxyl, and amine groups were prepared by a microwave technique and employed together with KI, which showed exceptional catalytic activity in the cycloaddition of carbon dioxide with different epoxides. In addition, the catalyst was easily reusable and had stable recyclability. And the catalyst displayed outstanding catalytic performance due to the synergistic effect of carboxyl (-COOH), hydroxyl (-OH), and amine (-NH) groups. The developed new catalytic system NCDs-3/KI showed outstanding transformation (99%) of 4-phenyl-1,3-dioxolan-2-one for styrene oxide at 100 °C and 0.1 MPa in 3 h and solvent-free conditions.