Synergistic effect of Fe/Cu[sbnd]N[sbnd]C dual single-atom catalyst for C[sbnd]H bond oxidation

Abstract

Transition metal-based (Fe, Co, Cu, etc.) single-atom catalysts (SAC) have been widely used in the direct oxidation of ethylbenzene and benzene. However, their catalytic performance is limited by the low metal loading. Compared with traditional SAC, dual site single-atom catalysts (DSAC) show the advantages of abundant active sites, high metal loading, and excellent catalytic performance. Herein, a novel Fe/CuNC DSAC was prepared by facile one-pot pyrolysis of formaldehyde, dicyandiamide, and metal salts. Dicyandiamide acted as the carbon source with advantage of high nitrogen content, which promoted the formation of metal centers and increased the metal loading. Meanwhile, the synergistic effect between Fe and Cu active centers was revealed to adjust the coordination environment, thus improving the catalytic activity of oxygen activation. The synthesized Fe/CuNC DSAC demonstrated superior catalytic performance in ethylbenzene oxidation reaction with O2 as a green oxidant under mild reaction conditions, with a 99 % conversion of acetophenone and no significant degradation of activity after 10 circles. In addition, NaCl was added into the synthesis as a template to adjust the pore structure, and the modified Fe/CuNC DSAC showed excellent performance in benzene oxidation reaction with high product conversion. In conclusion, this work paves the way for the construction of efficient, green, and cost-effective catalysts for the direct oxidation of ethylbenzene and benzene.