Constructing MOFs-derived Co3O4 microsphere with atomic p-n homojunction as an efficient photothermal catalyst for boosting ethyl acetate oxidation under light irradiation

A synthetic strategy for Co-MOF-74-derived Co3O4-based materials (polyhedral prism, hexagonal-prism spindle and prism-assembly 3D microspheres with different surface dense degrees) with atomic p-n homojunctions were proposed by introducing a dual-ligand (2,5-dihydroxyterephthalic acid and 2-methylimidazole) approach in the hydrothermal process. Among these Co3O4-based catalysts, the Co3O4-M-3 catalyst with 3D prism-assembly microsphere exhibited the greatest photothermal catalytic activity for ethyl acetate oxidation (around 92%) under the visible-IR light intensity of 480 mW/cm2 (λ > 420 nm). The smart modulation of dual-ligand approach could effectively improve the oxygen storage capacity, abundant oxygen vacancies and outstanding reductive ability over the Co3O4-M-3 catalyst. In addition, Mott-Schottky plot characterization verified the formation of p-n homojunction over the Co3O4-M-3, and its suitable energy band level and Z-scheme charge transfer pathway effectively improved visible-light absorption capacity, accelerated charge pairs transportation and restrained photogenerated electron-hole recombination. Finally, in situ DRIFTS results demonstrated that the adsorbed oxygen and lattice oxygen would participate in the photothermal catalytic reaction. Ethanol and acetic acid were considered as a main reaction pathway, whereas methyl ethyl ketone as no-critical intermediate was generated in the strict condition with exclusive active lattice oxygen of catalyst and light irradiation.