Transfer hydrogenation reactions over single-atom catalysts

Transfer hydrogenation (TH) has become the new frontier of hydrogenation science owing to the use of non-H₂ hydrogen sources which are safer and easier handling for constructing various hydrogenated products. As for heterogeneous catalysts applied for TH which take advantages of convenient separation and recycling, single-atom catalysts (SACs) are attractive alternatives because of their maximum atom utilization, well-defined active sites and tunable local atomic structure. Recent literature has manifested the good performance of SACs for TH, gaining attention both from academia and industry. In this perspective, we review TH achieved by SACs according to classified hydrogen sources and provide a comprehensive understanding of the relationship between their structural characters and performance for TH. In addition, corresponding synthetic strategies of SACs are also demonstrated to reveal their roles in forming the featured structures. The remained challenges and potential opportunities in this field are also discussed in the end. This review will guide the design of better-performing SACs for TH and give an impetus to the development of green and cost-effective hydrogenation technology.