Searching for an efficient single-atom catalyst for benzene hydroxylation to phenol is of critical importance, but it still remains a challenge. Herein, a single-atom catalyst with unique Cu-N2 moieties (Cu1-N2/HCNS) was prepared and confirmed by HAADF-STEM and EXAFS. Turnover number (TON) over Cu1-N2/HCNS (6,935) is 3.4 times of Cu1-N3/HCNS (2,034) under the same reaction conditions, and both exhibit much higher phenol selectivity (close to 99%) and stability compared with Cu nanoparticles and nanoclusters. Experiments and DFT calculations reveal that atomically dispersed Cu species are active sites for benzene hydroxylation to phenol, and the Cu-N2 is more active than Cu-N3 owing to its much lower energy barrier concerning the activation of H2O2 led by its unique coordination state of local atomic structure. We envision that this work opens a new window for modulating coordination environments of single metallic atoms in catalysis design.
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