Finely dispersed CuO on nitrogen-doped carbon hollow nanospheres for selective oxidation of sp3 C-H bonds

Hollow nanostructured materials are of great importance in heterogeneous catalysis owing to their improved mass transfer and diffusion properties. In this study, we have successfully prepared a novel nanocomposite, CuO supported nitrogen-doped carbon hollow nanospheres (denoted as CuO/N-C-HNSs), by a template protection-sacrifice method employing SiO2 nanospheres as the sacrificial template. The diverse nitrogen species present in the support anchored the CuO nanoparticles firmly and stabilized them as fine particles having sizes below 10 nm. The as-prepared CuO/N-C-HNSs efficiently catalyze the selective oxidation of sp(3) C-H bonds under mild reaction conditions using t-butyl hydroperoxide as the oxidant and water as the green solvent. The strong coordination between CuO and nitrogen species prevents the aggregation as well as leaching of CuO nanoparticles during the catalytic reaction. A wide range of aromatic hydrocarbons were smoothly oxidized into the corresponding products at 80 degrees C in 20 h affording both conversion and selectivity as high as 99%. The excellent catalytic activity and reusability of CuO/N-C-HNSs can be attributed to the uniformly dispersed CuO sites, hollow nanostructure and the synergistic effect between CuO and nitrogen-doped carbon hollow nanospheres.