Synergistic Regulation of Excited-State Electrons Enables Sunlight-Driven C─Br Bond Activation Through In Situ Polymerized Polyoxometalate-Gold Nanocluster Assemblies.

While gold nanoclusters (AuNCs) offer unique molecule-like properties and discrete energy levels, their potential in photocatalysis remains largely untapped due to inherent stability and recombination issues. Herein, we report a ternary gold superclusters (AuSCs) architecture, AuSCs@SiW9@PDA, that overcomes these limitations through cooperative regulation of excited-state electron dynamics. The composite is constructed via depletion-driven assembly of glutathione-protected AuNCs with a Keggin-type polyoxometalate, (Na10SiW9O34 or SiW9), followed by encapsulation within a polydopamine (PDA) network. In this system, SiW9 serves as an efficient electron sink, while PDA enhances solar light absorption, promotes interfacial charge transport, and suppresses recombination, collectively increasing the density of photogenerated electrons. As a result, AuSCs@SiW9@PDA enables efficient sunlight-driven activation of the thermodynamically robust C─Br bond in CBr4, affording (1,3,3,3-tetrabromopropyl)benzene from terminal aryl alkenes in yields up to 90%. The activity markedly exceeds that of the corresponding binary analogues (AuSCs@SiW9 and AuSCs@PDA) and their physical mixtures, highlighting the critical role of synergistic excited-state electron-transfer. Mechanistic investigations reveal accelerated electron transfer to CBr4 and suppressed charge recombination as key factors governing C─Br bond cleavage. Overall, this work establishes AuSCs as robust, sunlight-driven photocatalysts and demonstrates excited-state electron management as a strategy for sunlight-driven bond activation.