Photothermal oxidation of cyclohexane over CoLaOx/WO3 Z-scheme composites with p-n heterojunction in solvent-free conditions

Abstract

Photothermal oxidation of cyclohexane with molecular oxygen in solvent-free is considered to be an efficient approach for the formation of cyclohexanone and cyclohexanol (KA oil), and possesses the potential to generate the next stage product of adipic acid (AA) by one-pot oxidation in chemical industry. Herein, a unique type of Co8La1Ox/WO3 Z-scheme nanocomposites with p-n heterojunction was successfully constructed by a facile process of solvothermal reaction in conjunction with the simple impregnation method. The Co8La1Ox/WO3 Z-scheme heterojunction nanocomposites achieved an excellent catalytic performance for the photothermal oxidation of cyclohexane at 120 ℃ under visible light in solvent-free conditions. Surprisingly, 10.35% conversion of cyclohexane with 98.75% selectivity of KA oil (liquid, 80.97%) and AA (solid, 17.78%) was achieved during the reaction time of 3 h. Moreover, the desirable durability and stability of the Co8La1Ox/WO3 composites demonstrated a potential application as an industrial catalyst. The outstanding catalytic performance of the Co8La1Ox/WO3 composites could be ascribed to the enhanced electron excitation capacity, the accelerated electron-hole separation and migration, the inhibited charge recombination, the strong visible-light absorption, and the efficient synergetic catalytic effect of photo-thermo. Besides, high oxygen adsorption capacity and large specific surface area of the Co8La1Ox/WO3 composites can efficiently build a bridge between cyclohexane and O2 to fully utilize the oxygen participation in the oxidation. The present approach provides a promising perspective for the designing and constructing of Z-scheme heterojunction catalyst with a high-efficiency photo-thermo catalytic performance in the oxidation of cyclohexane to KA oil and AA in chemical industry.