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.

Dual-active sites (DASs) catalysts have positive potential applications in broad fields because of their specific active sites and synergistic catalytic effects. Therefore, the controllable synthesis and finely regulating the activity of such catalysts has become a hot research area for now. In this work, we developed a pyrolysis-etching-hydrogen activation strategy to prepare the DASs catalysts involving single-atom Cu and B on N-doped porous carbon material (Cu₁-B/NPC). Numerous systematic characterization and density functional theoretical (DFT) calculation results showed that the Cu and B existed as Cu-N₄ porphyrin-like unit and B-N₃ unit in the obtained catalyst. DFT calculations further revealed that single-atom Cu and B sites were linked by bridging N atoms to form the Cu₁-B-N₆ dual-sites. The Cu₁-B/NPC catalyst was more effective than the single-active site catalysts with B-N₃ sites in NPC (B/NPC) and Cu-N₄ porphyrin-like sites in NPC (Cu₁/NPC), respectively, for the dehydrogenative coupling of dimethylphenylsilane (DiMPSH) with various alcohols, performing the great activity (> 99%) and selectivity (> 99%). The catalytic performances of the Cu₁-B/NPC catalyst remained nearly unchanged after five cycles, also indicating its outstanding recyclability. DFT calculations showed that the Cu₁-B-N₆ dual-sites exhibited the lowest energy profile on the potential energy surface than that of sole B-N₃ and Cu-N₄ porphyrin-like sites. Furthermore, the rate-limiting step of dehydrogenation of DiMPSH on Cu₁-B-N₆ dual-sites also showed a much lower activation energy than the other two single sites. Benefitting from the superiority of the Cu₁-B-N₆ dual-sites, the Cu₁-B/NPC catalyst can also be used for CO₂ electroreduction to produce syngas. Thus, DASs catalysts are promising to achieve multifunctional catalytic properties and have aroused positive attention in the field of catalysis.