Atomically Precise Metal Nanocluster Photosystem: Electron Relay Boosts Photocatalytic Organic Transformation

Atomically precise metal nanoclusters (NCs) demonstrate emerging potential as a new generation of photosensitizers in photoredox catalysis. However, metal NCs suffer from intrinsic poor instability, which leads to the loss of photosensitization effect and hampers their widespread applications in heterogeneous photocatalysis. Herein, we corroborate the design of a spatially directional charge transfer pathway over transition metal chalcogenide (TMC)-based heterostructures by way of a facile and efficient electrostatic self-assembly approach. Positively charged solid-state nonconjugated insulating polymer of poly(allylamine hydrochloride) (PAH) and negatively charged glutathione (GSH) capped metal NCs [Ag₉@(GSH)₆] as building blocks were controllably and highly ordered anchored on the TMC substrate. It was unveiled that owing to the appropriate energy level alignment and interface configuration, photogenerated electrons over metal NCs can directionally flow to the TMC substrate with the aid of PAH, which functions as an interfacial charge transfer mediator, and simultaneously holes migrate in the opposite direction, thereby collaboratively contributing to substantially boosted charge separation and prolonged charge lifetime. Benefiting from these merits, the thus self-assembled TMCs/PAH/metal NC heterostructure unfolds conspicuously enhanced photoactivity toward anaerobic selective photocatalytic reduction of nitroaromatics to amino derivatives under visible light irradiation. This work would significantly reinforce our fundamental understanding of the charge transfer characteristic of atomically precise metal NCs and the charge-withdrawing capability of solid insulating polymers for solar energy conversion.