Leveraging electron distribution reconstruction of spinel MnCo2O4 hollow microflowers for the aerobic oxidation of limonene

Abstract

The utilization of biomass-derived limonene is an emerging field. The heterogeneous oxidation of limonene to high value-added chemicals has been recently considered as a promising way, but still remains a big challenge. Here, we construct a highly active MnCo₂O₄ catalyst with an intriguing hollow microflower-like morphology assembled by uniform porous sheets (HMMF). When employed in the oxidation of limonene to 1,2-limonene oxide (LO), the HMMF catalyst achieves a LO yield of 64.0 % with the limonene conversion of 82.8 % and selectivity of 77.3 % to LO under mild reaction conditions, far outperforming the monometallic Co₃O₄ catalyst. The high performance can be attributed to the synergistic benefits of bimetallic spinel structure and the unique morphology. Experimental results and theoretical research unveil that the substitution of Mn into Co₃O₄ to form the well-defined MnCo₂O₄ spinel promotes the establishment of highly active asymmetric Mn−O−Co centers. The reconfigured electronic structure contributes to the generation of oxygen vacancy (OV) and redox couples, facilitating the production of active oxygen species and thus boosting the oxidation kinetics. The mesoporous structure with large surface area can enhance the contact of reactive molecules with the active sites and promote the transportation of reactants and products within the channels. This study offers a successful paradigm for the construction of bimetallic spinels with well-integrated assembled morphology for the applications in the selective oxidation of hydrocarbons and beyond.