Surmounting the instability of atomically precise metal nanoclusters towards boosted photoredox organic transformation

Abstract

Atomically precise metal nanoclusters (NCs) have recently been recognized as an emerging sector of metal nanomaterials but suffer from light-induced poor stability, giving rise to the detrimental self-transformation into metal nanocrystals (NYs), losing the photosensitization effect and ultimately retarding their widespread applications in photoredox catalysis. Are metal NCs definitely superior to metal NYs in heterogeneous photocatalysis in terms of structural merits? To unlock this mystery, herein, we conceptually demonstrate how to rationally manipulate the instability of metal NCs to construct high-efficiency artificial photosystems and examine how the metal NYs self-transformed from metal NCs influence charge transfer in photoredox selective organic transformation. To our surprise, the results indicate that the Schottky-type electron-trapping ability of Au NYs surpasses the photosensitization effect of glutathione (GSH)-protected Au clusters [Au₂₅(GSH)₁₈ NCs] in mediating charge separation and enhancing photoactivities towards selective photoreduction of aromatic nitro compounds to amino derivatives and photocatalytic oxidation of aromatic alcohols to aldehydes under visible light irradiation. This work strategically provides new insights into the inherent instability of metal NCs utilized for photocatalysis and reinforces our fundamental understanding on metal NC-based artificial photosystems for solar energy conversion.