Enhanced Catalytic Performance of Subnano Copper Oxide Particles

Subnanoparticles (SNPs) with ultrasmall particle sizes (<1 nm) have potential to provide catalytic activity that is superior to that of nanoparticles. Size-controlled CunOx (n = 12, 28, and 60) materials supported on zirconia, prepared using a dendritic macromolecular reactor, exhibited increased ionicity of the Cu–O bonds with a decrease in size of the particles, which was suggested on the basis of the peak intensity in the Cu 2p3/2 region. The polarization of the Cu–O bonds in the ultrasmall copper oxides provides size-dependent catalytic activity in aerobic oxidation of the CH3 group bonded with aromatic rings. The smallest Cu12Ox materials achieved an excellent large turnover number (TON = 40 206) without any significant deactivation.