Photocatalytic direct dehydrogenative coupling of alcohols using α-cyclodextrin decorated sulfur quantum dots

Sulfur quantum dots, a new type of non-metallic quantum dots, have gained widespread attention as a promising alternative material. In this work, we synthesized aqueous sulfur quantum dots modified with α-cyclodextrin (CD-S dots) by hydrothermal method. Under visible light irradiation, CD-S dots could promote the dehydrogenative cross-coupling reaction of alcohols and amines to produce imine products. We demonstrated the host-guest interaction between the ligand of CD-S dots and benzyl alcohol through experiments such as nuclear magnetic resonance (NMR) spectroscopy. Consequently, benzyl alcohol could easily approach the surface of CD-S dots without being affected by the ligand, and then it could be oxidized by holes. It was suggested that CD-S dots reduced the barriers of carrier transfer through host-guest interactions with benzyl alcohol, and improved the selectivity and efficiency of the reaction. Our work provided ideas for the application of emerging sulfur quantum dots in selective organic synthesis. Based on the rich tunability of quantum dot materials, various efficient and eco-friendly catalytic systems are expected to be developed.