Engineering atomically dispersed single Cu–N3 catalytic sites for highly selective oxidation of benzene to phenol†

Abstract

Developing efficient approaches for selective oxidation of arene C–H bonds has been a challenging goal. Here we report a facile and practical strategy to fabricate an N-doped reduced graphene oxide (NRGO) based single-atom Cu catalyst (SACu-NRGO) by calcinating dicyandiamide (DCDA) and graphene oxide (GO) wrapped with Cu mesh for the selective oxidation of benzene to phenol at room temperature. According to extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) analyses and density functional theory (DFT) calculations, single atomic Cu is anchored by three adjacent pyrrolic N atoms to form CuN₃ active sites in the NRGO skeleton, which originates from the gaseous Cu(NH₃)_n generated via the reaction between Cu mesh and the ammonia pyrolyzed from DCDA. The SACu-NRGO exhibits excellent catalytic performance towards oxidation of benzene with the selectivity of phenol up to 98.6%, owing to the large specific surface area, fully exposed and homogeneously dispersed CuN₃ active sites, as well as the coordination effect between Cu and N species. Furthermore, the structure of the single-atom active sites and the mechanism of the oxidation process are elucidated in depth by DFT calculations.