Maneuvering the Directional Charge Flow for Photoredox Organic Conversion

Transition-metal chalcogenide quantum dots (TMC QDs) show great promise in artificial photosynthesis for excellent light-harvesting capability. Nonetheless, TMC QDs have limitations of ultrafast charge recombination rate, sluggish carrier migration kinetics, and generic photocorrosion, retarding their widespread applications. To solve these obstacles, herein, we demonstrate the stimulation of charge migration over TMC QDs with the aid of nonconjugated insulating polymer and graphene (GR) for a versatile photoredox selective organic transformation. To this end, an ultrathin insulating polymer layer, i.e., poly(allylamine hydrochloride) (PAH), grafted on the GR framework, is electrostatically intercalated at the interface of TMCs QDs and the GR framework via a self-assembly for constructing TMC QDs/PAH/GR three-dimensional spatially multilayered heterostructures. In this well-defined nanoarchitecture, TMC QDs function as a light-harvesting antenna, GR as a terminal electron reservoir, and PAH as an intermediate interfacial charge relay mediator. We ascertain that the ultrathin PAH interim layer unexpectedly fosters the photoelectron migration from TMCs QDs to the GR framework in a tunable fashion, boosting the charge separation of TMCs QDs and resulting in significantly improved photoactivities toward anaerobic reduction of aromatic nitro compounds to amino derivatives and oxidation of alcohols to aldehydes under visible light. Photoredox catalysis mechanisms of such TMC QDs/PAH/GR photosystems are elucidated, and the active species in these photoredox organic conversion reactions are comprehensively determined. Our work would open new frontiers to finely modulate the charge transport of TMCs QDs via nonconjugated insulating polymers for solar energy conversion.