Alloy nanocluster artificial photosystems steering photoredox organic transformation†

Abstract

Atomically precise alloy nanoclusters (NCs) represent an emerging sector of metal nanomaterials as a new generation of photosensitizers for light harvesting and conversion, owing to their distinctive atom-stacking pattern, quantum confinement effect, and enriched active sites. Despite the sporadic progress made in the past few years in constructing alloy NCs photosystems, photoinduced charge transfer characteristics and photocatalytic mechanisms of alloy NCs still remain elusive. In this work, we conceptually demonstrate the rational design of alloy NC (Au_1−xAg_x, Au_1−xPt_x, and Au_1−xCu_x)/transition metal chalcogenide (TMCs) heterostructure photosystems via a ligand-triggered self-assembly strategy. The results signify that electrons photoexcited in alloy NCs can smoothly transport to the TMC substrate with the aid of an intermediate ultrathin organic molecule layer, while holes migrate in the opposite direction, promoting the charge separation and prolonging the charge lifetime. Benefitting from the advantageous charge migration, the self-assembled alloy NC/TMC heterostructures exhibit significantly enhanced photoactivity towards selective photoredox organic transformation including selective reduction of aromatic nitro compounds to amino derivatives and selective oxidation of aromatic alcohols to aldehydes under visible light. The predominant active species during the photoredox catalysis are determined, through which alloy NC-dominated photoredox mechanisms are elucidated. Our work provides new insights into the smart construction of atomically precise alloy NC hybrid photosystems, and more importantly, paves the way for regulating the spatially vectorial charge transfer over alloy NCs to achieve solar-to-chemical energy conversion.