Low‐Toxicity ZnSe/ZnS Quantum Dots as Potent Photoreductants and Triplet Sensitizers for Organic Transformations
Chengming Nie, Xuyang Lin, Guohui Zhao, Kaifeng Wu
Abstract
Colloidal quantum dots (QDs) can photocatalyze diverse organic reactions. However, reported QD-photocatalysts often contain highly-toxic elements Cd or Pb, and have not surpassed prototypical transition-metal complexes in terms of their photoredox power or excited-state energy. Here we report low-toxicity ZnSe/ZnS core/shell QDs as potent visible photocatalysts to drive challenging organic transformations. To overcome the limitation of short excited-state lifetime of the QDs, we functionalize their surfaces with benzophenone ligands which can rapidly extract electrons from photoexcited QDs and sustain long-lived charge-separated states. The benzophenone anions function as potent electron relay to drive dehalogenation of aryl chlorides and additive-free polymerization of acrylates. Alternatively, the QDs are functionalized with biphenyl ligands to store energy in long-lived, energetic triplets, enabling [2+2] homo-cycloaddition of styrene and cycloaddition of carbonyls with alkenes.