Synthesis of Cu Single Atom with Adjustable Coordination Environment and Its Catalytic Hydrogenation Performance※

The synthesis of stable single-metal site catalysts with high catalytic activity and selectivity with a controllable coordination environment is still challenging.Due to the different electronegativity of different coordination atoms (N, P, S, etc.), adjusting the coordination atom type of the active metal center is an effective and wise strategy to break the symmetry of the electron density.We adopted a cation exchange strategy to synthesize two Cu single-atom catalytic materials with different coordination structures.This strategy can change the coordination environment of Cu single atom by changing the different organics wrapped around Cu-CdS.This strategy mainly relies on the anion skeleton of sulfide and the N-rich polymer shell to produce a large number of S and N defects during the high-temperature annealing process, and the precise synthesis of a single-metal Cu site catalyst material with rich edge S and N double modification.In these two materials, one single Cu atom has double coordination of sulfur (S) and nitrogen (N), and the other single Cu atom has only a single S coordination.The first shell coordination number of Cu central atom is 4, the structure of Cu-S/N-C is Cu-S1N3, and the structure of Cu-S-C is Cu-S4.The results show that the catalytic performance of Cu-S/N-C in the hydrogenation of nitrobenzene compounds is much better than that of Cu-S-C, that is, the Cu monoatomic materials with S and N double-modified metal sites has better hydrogenation activity than single S-modified metal sites.After 20 min of reaction, under the catalysis of Cu-S/N-C, the conversion rate of nitrobenzene reached 100%, and the activity did not decrease significantly after being recycled for 5 times.It shows that the Cu-S/N-C catalytic material with a single-atom structure we synthesized has good stability.This discovery not only provides a feasible method for adjusting the coordination environment of the central metal to improve the performance of single-atom catalytic materials, but also provides an understanding of the catalytic performance of heteroatom modification.