Unraveling the synergistic role of oxygen vacancy and Co dual-site pairs in MOFs-derived defect-engineered Co3O4 catalysts with a hollow architecture for photothermal OVOCs degradation: Formation of reactive oxygen species

Abstract

Herein, we developed a solvent regulation strategy with dual organic ligands to synthesize a series of Co-MOF-74 isomer derivatives as model materials that were investigated the formation of reactive oxygen species (ROS) and photothermal OVOCs (methanol, acetone and ethyl acetate) degradation. As a result, the defect-engineered Co3O4-DIW-100 with hollow microsphere synthesized under an equivalent volume ratio of N, N-dimethylformamide (DMF), isopropanol and H2O, can efficiently improve the photothermal catalytic conversions for methanol (97 %), acetone (96 %) and ethyl acetate (93 %) oxidation under Xenon lamp irradiation, compared with unremarkable Co3O4-M catalyst. Thanks to its hollow architecture, the optimal Co3O4-DIW-100 possessed the enhanced low-temperature redox capability and more exposed Co3+ and VO sites. Furthermore, DFT and EPR results revealed that the VO and Co dual-site pairs at surrounding structural defects synergistically participated in the generation of abundant ROS (O2−) through a specific O2 activation configuration (Co2+=O–O–Co3+). Meanwhile, light irradiation could induce the separation and transfer of charge carriers to accelerate the formation of O2−. The superior absorption of visible light derived from the narrow Eg value on Co3O4-DIW-100 can boost a higher light-driven temperature to perform the photothermal OVOCs oxidation. The formation and transformation of sectional key reaction intermediates, such as CH3COOH, CH3OH and HCOOH, were accurately identified and investigated by in-situ DRIFTS results on the methanol, acetone and ethyl acetate oxidation.