This review summarizes the studies on homogeneous and hetergeneous catalysis of ligand–free naked metal clusters, with an emphasis on the cooperative active–sites mechanism for catalytic CO oxidation, NO_x reduction, CO₂ reduction, dinitrogen and oxygen reduction, as well as hydrogen evolution and hydrocarbon conversion.

Abstract

The properties of sub–nano metal clusters are governed by quantum confinement and their large surface–to–bulk ratios, atomically precise compositions and geometric/electronic structures. Advances in metal clusters lead to new opportunities in diverse aspects of sciences including chemo–sensing, bio–imaging, photochemistry, and catalysis. Naked metal clusters having synergic multiple active sites and coordinative unsaturation and tunable stability/activity enable researchers to design atomically precise metal catalysts with tailored catalysis for different reactions. Here we summarize the progress of ligand–free naked metal clusters for catalytic applications. It is anticipated that this review helps to better understand the chemistry of small metal clusters and facilitates the design and development of new catalysts for potential applications.