A Critical Review on the Catalytic Applications of Non-Metallic Gold Nanoclusters: Selective Oxidation, Hydrogenation, and Coupling Reactions

In recent decade, gold nanoclusters with atomic precision (AunLm where L = ligand) have been demonstrated as a new and promising class of nanocatalysts. The AunLm catalysts of different sizes possess unique crystal and electronic structures, thereby providing an excellent opportunity to correlate the intrinsic catalytic performance with the catalysts' structure as well as to study mechanisms of chemical reactions catalyzed over gold nanoparticles. In this review, controlled synthesis of atomically precise gold nanoclusters and their thermal stabilities are explained. We demonstrate important roles played by the gold nanoclusters for catalytic reactions, including selective oxidation and hydrogenation as well as carbon-carbon coupling reactions. Tailoring of the catalysts' functions is discussed in terms of size-specificity, ligand engineering (e.g., aromatic vs aliphatic), and doping effects (e.g., copper, silver, palladium, and platinum). The proposed reactions' mechanisms and the structureactivity relationships at the atomic detail are presented. Keywords: Gold nanocluster, oxidation, hydrogenation, C-C coupling, DFT, size-specificity, ligand effects, doping effects.