  Developing a green and cost-effective catalytic system for the selective
oxidation of biomass-derived alcohols is vital for the sustainable synthesis of
fine chemicals. Herein, highly dispersed subnanometric amorphous CoOx clusters
in anatase TiO2 nanosheets (Co-TiO2) fabricated by green solvent CO2 assisted
approach could directly activate peroxymonosulfate (PMS) for the highly
selective oxidation of various biomass-derived alcohols. Advanced
characterizations (e.g., EXAFS, EPR, AC HAADF-STEM) reveal that a strong
interaction of CoOx clusters and the anatase TiO2 support exist in Co-TiO2 and
Co atom in Co-TiO2 is mainly consisted of Co2+ and Co3+. The Co-TiO2 catalyst
offers superior catalytic performance in the conversion of six types of
alcohols (e.g., benzyl alcohol (BAL), 5-hydroxymethylfurfural (HMF)) with high
selectivity to produce corresponding aldehydes. Highly dispersed CoOx clusters
and the interaction between CoOx clusters and TiO2 support contribute to the
superior performance. Mechanism studies show that SO4 radicals play the
dominant role in the selective oxidation of model reactant BAL and 1O2
participates in the non-radical pathway. DFT calculations are well matched with
experiment and decipher that the strong interaction between CoOx clusters and
TiO2 support promotes the formation of SO4 and SO5.
