Metal single-atom catalysts for selective hydrogenation of unsaturated bonds

Selective hydrogenation is widely used in medicine, chemical production, printing and dyeing, health care products and other fields. A catalyst with excellent performance can not only improve the yield, but also produce great economic benefits. Single atom catalysts (SACs) can reduce the waste of metal resources in the synthesis process and have excellent catalytic performance in the catalytic reaction process. With the reduction of the particle size from nanoclusters to the single atom level, a sharp increase of surface energy and 100% atomic utilization provide a guarantee for their catalytic activity. However, these two factors are not the only reason for the excellent catalytic performance of SACs. Herein, the applications of SACs in the selective hydrogenation of unsaturated bonds (including carbon–carbon, nitrogen–oxygen, carbon–oxygen and carbon–nitrogen) are reviewed, and the factors affecting their catalytic activity are investigated by comparing the catalytic properties. Meanwhile, the effects of the synthesis method, composition content, monatomic coordination and charge relationship between the metal and carrier on the catalytic performance were introduced by combining different characterization and testing methods. A particular emphasis is given to the research progress of SACs in recent years and their future development and challenges.