Beneficial Synergistic Intermetallic Effect in ZnCo 2 O 4 for Enhancing the Limonene Oxidation Catalysis.

Utilization of naturally occurring limonene from renewable biomass as a key starting material for the synthesis of valuable chemicals is a promising avenue to reduce both the dependence on nonrenewable fossil fuels and global CO 2 emission. Herein, we report a highly active tremella-like ZnCo 2 O 4 catalyst for the selective oxidation of limonene with molecular oxygen under mild reaction conditions. The developed ZnCo 2 O 4 catalyst exhibits an appealing reaction performance with a limonene conversion of 93.5% (reaction rate of 0.0823 mmol g cat -1 h -1 ) and selectivity of 75.8% for 1,2-limonene oxide (LO), far outperforming the monometallic oxides of ZnO and Co 3 O 4 . Detained experimental characterizations and analyses manifest that the substitution of Zn into the Co 3 O 4 framework can facilitate the formation of more unsaturated coordination sites and oxygen vacancies due to the modified chemical environment of Co atoms, inducing a beneficial synergistic intermetallic effect for the limonene oxidation catalysis.