Engineering the asymmetric active moiety of Ce-N₃P for efficient selective oxidation of aromatic C–H bonds

Developing an effective catalyst for the selective oxidation of hydrocarbon to high value-added compounds remains as a challenge in terms of the growing global concerns about green chemistry and environmental sustainability. Herein, asymmetric nitrogen and phosphorus co-coordinated Ce single-atom sites (Ce-N₃P-C) were constructed for the activation of aromatic C–H bond. Ce-N₃P-C demonstrates excellent catalytic performance for efficient solvent-free aerobic oxidation of aromatic C–H bonds, especially for oxidation of ethylbenzene with 97% selectivity of acetophenone and high stability. The turnover frequency (TOF) value is 536 h⁻¹, which is the highest level among reported non-precious-metal catalysts in a similar system. The partial substitution of coordinated N with P atom breaks the symmetry of the active moiety of Ce and raises the electron density of Ce center. The reduced valence state of metallic Ce indicates that more electrons could transfer to the antibonding π-orbital of the adsorbed O₂, thus promoting the subsequent free radical reaction and accelerating the rate-determining step. The breaking of coordination symmetry of single-atom site catalyst by introducing heteroatoms to tune its active moiety paves a way to boost the catalytic performance of similar catalysts.