Organic Photocatalysis by In Situ Polymerized Gold Nanocluster-Polydopamine Networks

Abstract

Gold nanoclusters (AuNCs), with their atomically precise structures and molecule-like electronic states, offer unique opportunities for photocatalysis. However, their application has been largely restricted to cocatalyst roles due to intrinsic limitations such as poor photostability and rapid charge carrier recombination. Here, we demonstrate the use of AuNCs as standalone photocatalysts for natural sunlight-driven organic synthesis. We develop a robust in situ polymerization-guided self-assembly approach to construct a hierarchical hybrid material, ISPGN-PDA, comprising ultrasmall AuNCs embedded within an aggregated network of polydopamine (PDA) nanosheets. This architecture enables broad solar light absorption, enhanced charge separation, and suppressed electron-hole recombination. The ISPGN-PDA composite efficiently catalyzes the oxidative cyclization of N-allylbenzamides to oxazole derivatives using N-bromosuccinimide (NBS) or N-iodosuccinimide (NIS), achieving up to 99% and 98% yields, respectively. Mechanistic studies reveal the formation of charge-transfer complexes between ISPGN-PDA and NBS/NIS, with AuNCs acting as the primary active photocatalyst. The PDA matrix serves dual roles: enhancing solar light harvesting and facilitating charge transport by capturing photogenerated electrons, thereby promoting charge separation and stability. Overall, this organic transformation proceeds under mild conditions, features a broad substrate scope, and demonstrates excellent catalyst recyclability and stability, highlighting the potential of AuNCs as efficient and durable standalone photocatalysts in solar-driven organic transformations.