Efficient photo-thermo synergy in solvent-free oxidation of cyclohexane to adipic acid under visible light over p-n heterojunction FeCeOx/WO3 composites

Abstract

Photothermal catalytic oxidation of cyclohexane was found to be an effective and green strategy for the production of cyclohexanol and cyclohexanone (KA oil). However, such strategy existed some obstacles, which hindered its application in the one-step synthesis of adipic acid (AA), necessitating further breakthroughs. Herein, a p-n heterojunction of Fe8Ce2Ox/WO3 was constructed by a simple combination of solvothermal and impregnation methods, enabling the one-step synthesis of AA via the photothermal cyclohexane oxidation under solvent-free and visible light conditions. Remarkably, the Fe8Ce2Ox/WO3 nanocomposites exhibited outstanding catalytic performance, achieving a conversion of cyclohexane reached 9.67% with the 92.45% selectivity towards AA (solid, 59.46%) and KA oil (liquid, 32.99%). The Fe8Ce2Ox/WO3 composites also demonstrated exceptional stability in the production of AA, further highlighting its potential as a catalyst for industrial applications. The exceptional catalytic properties of Fe8Ce2Ox/WO3 composites can be attributed to the promoted electronic excitation capability, enhanced separation and migration of electron-hole, suppressed charge complexation, broaden visible-light absorption, and effective photo-thermal co-catalytic effects. Furthermore, the Fe8Ce2Ox/WO3 composites possess a strong adsorption capacity for oxygen and suitable specific surface area, which can be effectively facilitate the interaction between O2 and cyclohexane, enabling the full utilization of oxygen in the oxidation of cyclohexane to form AA. The proposed approach offers a novel methodology for the design and fabrication of photothermal catalysts to achieve the direct synthesis of AA via the cyclohexane oxidation under solvent-free and visible light conditions in industry.