An atomic-level strategy for unraveling gold nanocatalysis from the perspective of Au(n)(SR)m nanoclusters.

An atomic-level strategy is devised to gain insight into the origin of nanogold catalysis by using atomically monodisperse Au(n)(SR)(m) nanoclusters as well-defined catalysts for styrene oxidation. The Au(n)(SR)(m) nanoclusters are emerging as a new class of gold nanocatalyst to overcome the polydispersity of conventional nanoparticle catalysts. The unique atom-packing structure and electronic properties of Au(n)(SR)(m) nanoclusters (<2 nm) are rationalized to be responsible for their extraordinary catalytic activity observed in styrene oxidation. An interesting finding is that quantum size effects of Au(n)(SR)(m) nanoclusters, rather than the higher specific surface area, play a major role in gold-catalyzed selective oxidation of styrene. For example, Au(25)(SR)(18) nanoclusters (≈1 nm) are found to be particularly efficient in activating O(2), which is a key step in styrene oxidation, and hence, the ultrasmall Au(25) catalyst exhibits higher activity than do larger sizes. This atomic-level strategy has allowed us to obtain an important insight into some fundamental aspects of nanogold catalysis in styrene oxidation. The ultrasmall yet robust Au(n)(SR)(m) nanoclusters are particularly promising for studying the mechanistic aspects of nanogold catalysis and for future design of better catalysts with high activity and selectivity for certain chemical processes.