Maneuvering the Electronic State and Active Site of Assembled-Gold Nanoclusters through Polyoxometalate Implantation for Heterogeneous Green-Light Photocatalysis

Gold nanoclusters (AuNCs) exhibit unique molecule-like optical and electronic properties, making them promising candidates for photocatalysis. However, their application as primary photocatalysts in heterogeneous systems is limited by rapid electron recombination, small size, and high solubility. To overcome these limitations, we developed an approach combining AuNCs assemblies with electron trap centers to enhance charge separation and electron transfer. Using a depletion-driven assembly method, Keggin-type polyoxometalates (POMs), Na₁₀SiW₉O₃₄ (SiW₉), were uniformly embedded within spherical assemblies of glutathione-protected AuNCs, forming gold superclusters (AuSCs). The resulting AuSCs@SiW₉ exhibited complete photoluminescence quenching, enhanced metallicity, and stabilized photogenerated electrons via SiW₉, enabling their use as primary photocatalysts. The AuSCs@SiW₉ efficiently catalyzed the functionalization of terminal aryl alkyne with <i>N</i>-bromosuccinimide (NBS), achieving a tribromoketones yield of 94%, significantly outperforming AuSCs with lower or higher metallicity (38 and 65%, respectively). Mechanistic studies revealed that the improved gold metallicity in AuSCs@SiW₉ promotes charge transfer complex formation with NBS, while SiW₉ stabilizes photogenerated electrons, enhancing electron density under light irradiation. The AuSCs@SiW₉ exhibited strong visible-light absorption, photostability, and solvent dispersibility, enabling recyclability for up to five cycles and scalability for broader applications. This strategy positions gold as a viable primary photocatalyst, expanding its potential in heterogeneous photocatalysis toward synthesizing small molecules.