Boosting Catalytic\nHydrogen Transfer Cascade Reactions\nvia Tandem Catalyst Design by Coupling Co Single Atoms with Adjacent\nCo Clusters

The catalytic hydrogen transfer (CHT) cascade reaction\ncoupling\nalcohols with nitro compounds to synthesize imines is highly significant\ndue to its remarkable efficiency and atom economy. However, the complicated\nmultistep reaction process makes single-site catalysts exhibit unsatisfactory\ncatalytic performance for the CHT cascade reaction. Herein, inspired\nby the findings of DFT calculations that Co nanocluster (Co<sub>NC</sub>) and Co single atom (Co<sub>SA</sub>) can act as the optimal active\nsites for alcohol oxidation and nitro reduction, respectively, one\ndual-active site catalyst (Co<sub>SA</sub>-Co<sub>NC</sub>/CN), containing\nCo<sub>SA</sub> and Co<sub>NC</sub> sites, was synthesized by a two-step\nvacuum pyrolysis strategy. Benefiting from the relay-like tandem catalysis\nof Co<sub>NC</sub> and Co<sub>SA</sub>, Co<sub>SA</sub>-Co<sub>NC</sub>/CN achieved an impressive 93% nitrobenzene conversion and 99% imine\nselectivity at 160 °C in 4 h, with a record turnover frequency\nof 20.9 h<sup>–1</sup>. This work provides insights into the\nfunctions of single-atom and nanocluster active sites in the CHT cascade\nreaction and sheds light on the rational preparation of tandem catalysts.