Selective catalytic oxidation using air as the terminal oxidant is an ecofriendly route for the synthesis of fine and commodity chemicals. However, the catalyst generally faces the challenges of the inertness of molecular oxygen, limited substrate scope, poor selectivity, and high cost. Moreover, the toxicity of the catalyst should also be considered when the products are used in pharmaceutical or biotechnological areas. Here, upon investigating the dependence of catalytic oxidation on the crystal phases of iron oxides, we find that naked gamma-Fe2O3 particles exhibit excellent catalytic activity, selectivity, and stability in a series of imine synthetic reactions. The performance of gamma-Fe2O3 particles is significantly better than that of alpha-Fe2O3 and Fe2O3 under mild reaction conditions, and the gamma-Fe2O3 catalyst can be separated from the reaction mixture magnetically. Both experimental and theoretical calculation results show that gamma-Fe2O3 possesses supercapability for oxygen activation. The inverse spine] structure of gamma-Fe2O3 has abundant cation vacancies, which confers unique electronic properties on surface Fe species. These Fe species tend to transfer electrons to molecular oxygen to form O-2(-) or O-2(2-) species. These oxygen species are favorable for the dehydrogenation of alcohols, which is responsible for the high activity of gamma-Fe2O3 in this coupling reaction. (C) 2019 Elsevier Inc. All rights reserved.