Metal Nanoparticles for Redox Reactions

Reduction and oxidation reactions (redox reactions) are fundamental and important transformation of chemicals in both laboratory and industrial chemistries. With regard to atom economy and the environmental demands, an ultimate goal of these reactions is to employ molecular hydrogen (H₂) or molecular oxygen (O₂). High-performance heterogeneous catalysts with high activity, selectivity, recoverability, and reusability are ideal for the development of green sustainable processes using H₂ or O₂. Moreover, the heterogeneous catalyst systems are the promising approach to solve the disadvantage of homogeneous ones, such as short lifetimes (low stability), risk of contaminating products with metals (low recoverability), tedious workups for reuse (low reusability), and so on. For the design of high-performance heterogeneous catalysts under liquid-phase redox reactions, metal nanoparticles (NPs) is the most promising strategy because of their unusual properties compared to bulk metal. This review provides an overview of metal NP heterogeneous catalysts developed for redox reactions using H₂ or O₂. The state-of-the-art metal NP catalysts show higher activity and selectivity for the chemoselective hydrogenations of carbonyl, nitro, and alkynyl compounds while retaining C=C bonds, and the aerobic oxidation of alcohols and the Wacker type oxidation of alkenes, which overcome the limitations of the conventional catalyst systems. This improved catalytic performance is due to significant advances in the precise fabrication of nanoscale metals, which has made it possible to explore novel catalysis and design metal active centers.