Catalytic Reduction by Quasi-Homogeneous Gold Nanoclusters in the Liquid Phase

Reduction reactions play significant roles in industrial manufacture, and supported metal nanoparticles (NPs) show great prospect for mass production. The gold NPs have achieved expanding progress in selective reduction in recent years and will lead to a hot issue in the future. However, the designing of efficient catalysts is currently quite challenging because of the lack of systematic understandings on the fundamentals of the catalytic efficiency. Fortunately, tremendous advances can be expected with the aid of quasi-homogeneous NPs. This review highlights the unsupported gold NPs or nanoclusters (NCs) catalyzed reduction reactions, which include single-electron-transfer catalysis, selective hydrogenation of carbonyl and nitro groups. The tentative catalytic mechanism and the size-dependence of gold nanocatalyst have also been discussed in this review.