Silica-supported highly dispersed cobalt oxides prepared by adsorption are likely to be poorly reducible Co-phyllosilicates or CoO species. Here we report the synthesis of silica-supported monodispersed spinel nano-Co3O4 catalysts by inner-sphere complexation using Co-III ammine hydroxo complexes as precursors. The precursors were facilely prepared by stirring ammoniacal Co-II solutions exposed to air. The cobalt loadings (up to 188 mg/g) and particle sizes (3-10 nm) were tailored by successive complexation-calcination cycles. Such catalysts showed significantly superior reducibility and catalytic activity in complete propane oxidation in comparison to supported Co-phyllosilicates and CoO. A further development of this synthesis process may provide a variety of cobalt-based catalysts for important catalytic applications. (C) 2018 Elsevier B.V. All rights reserved.