Investigation into Enhanced Catalytic Performance for Epoxidation of Styrene over LaSrCo_<i>x</i>Fe_2–<i>x</i>O₆ Double Perovskites: The Role of Singlet Oxygen Species Promoted by the Photothermal Effect

Abstract

Current heterogeneous epoxidation catalysts are mainly based on the usage of peroxides as oxidants and rarely work under an oxygen atmosphere. Herein, we report the development of a photothermal catalytic approach with LaSrCoxFe2–xO6 double perovskite materials as heterogeneous epoxidation catalysts. Highest active LaSrCo1.6Fe0.4O6 (LSCF-1.6) material exhibited a conversion of 100% for styrene and selectivity of 87.8% for styrene oxide under an oxygen atmosphere (bubbled with oxygen, 100 °C). Based on the analysis of the results of electron paramagnetic resonance, density functional theory calculations, and controlled experiments, it is found that the singlet oxygen is the key reactive oxygen species for epoxidation of styrene over the LSCF-1.6 catalyst. The mechanistic study revealed that the epoxidation reaction proceeds through a photothermal mechanism and solvation effect, which involves the generation of hot electrons, holes, superoxides, and singlet oxygen species.