Hot Electron Photocatalysis Using Nontoxic Self-Doped Quantum Dots

Colloidal semiconductor quantum dots (QDs) have emerged as versatile photocatalysts for organic transformations. However, a significant drawback is their reliance on toxic metals like lead and cadmium, which limits their widespread application in solar-to-chemical conversion. Furthermore, current systems primarily utilize band-edge carriers for simpler photoredox reactions, while the potential for harvesting hot carriers in chemical transformations remains largely unexplored. To address these challenges, we developed nontoxic, cost-effective, and recyclable ternary CuInS₂ and quaternary Cu─In─Zn─S QDs as potent photocatalysts. Our findings demonstrate that hot electrons can be effectively generated through an ultrafast Auger process, enabling the photoreduction of aryl halides (with reduction potentials up to -2.90 V versus saturated calomel electrode (SCE)) and various cross-coupling (C─C, C─P, C─B, and C─S) transformations. Notably, quaternary Cu─In─Zn─S QDs exhibit significantly higher reactivity compared to CuInS₂ QDs, which is attributed to enhanced Auger-mediated hot electron generation. This work underscores the potential of directly utilizing Auger-generated hot electrons for extreme-potential organic transformations under mild conditions using nontoxic QDs.