Ionic-liquid-assisted synthesis of metal single-atom catalysts for benzene oxidation to phenol

Ionic liquids (ILs) have the advantages of low cost, eco-friendliness, abundant heteroatoms, excellent solubility, and coordinated ability with metal ions. These features make ILs a suitable precursor for fabricating metal single-atom catalysts (SACs). Herein, we prepared various metal single atoms anchored on ultrathin N-doped nanosheets (denoted as Cu1/NC, Fe1/NC, Co1/NC, Ni1/NC, and Pd1/NC) by direct pyrolysis using ILs and g-C3N4 nanosheets as templates. Taking benzene oxidation to phenol with H2O2 as a model reaction to evaluate their catalytic performance and potential applications, Cu1/NC calcined at 1000°C (denoted as Cu1/NC-1000) exhibits the highest activity with a turnover frequency of about 200 h−1 in the first 1 h at 60°C, which is better than that of most metal SACs reported in the literature. High benzene conversion of 82% with high phenol selectivity of 96% and excellent recyclability were achieved using the Cu1/NC-1000 catalyst. This study provides an efficient general strategy for fabricating SACs using ILs for catalytic applications.