La0.4Sr0.6CoO3-Catalyzed Selective Oxidation of Ethylbenzene to Acetophenone without Solvent: A New Reactive Oxygen Species Transformation Mechanism Mediated by •O2– Derived from 1O2

Abstract

Developing a green, stable, and cost-effective heterogeneous catalyst and clarifying its catalytic mechanism for the selective oxidation of C–H bonds without solvent to carbonyl compounds hold a significant theoretical and practical value. Herein, we synthesize perovskite catalysts using the sol–gel method to catalyze the selective oxidation of ethylbenzene. Notably, La_0.4Sr_0.6CoO₃-800 (800 °C is the calcination temperature of the catalyst) demonstrates remarkable efficacy, converting 73% of ethylbenzene into acetophenone with a selectivity of 93%. Characterization analyses reveal that the incorporation of strontium moderately disrupts the internal balance of the perovskite structure, leading to increased oxygen vacancies and enhanced oxygen adsorption capacity. Moreover, electron paramagnetic resonance and mechanistic studies prove that molecular oxygen on the catalyst surface is converted to singlet oxygen (¹O₂) and superoxide radical anions (^•O₂^–). The presence of ¹O₂ significantly aids in the production of ^•O₂^–, thereby effectively promoting the oxidation of ethylbenzene. This research introduces a new reactive oxygen species (ROS) transformation mechanism and provides valuable insights into the selective oxidation of hydrocarbons.