A facile route was developed for the large-scale preparation of core-shell CuO nanostructures based on a solvothermal route with subsequent calcination. The CuO nanostructures show core-shell shape and are composed of numerous nanoparticles with high porosity resulting from the thermal decomposition of the Cu2O precursors. A possible growth mechanism of the CuO core-shell nanostructures was proposed. The novel core-shell structure enlarges the range of absorbed light and enhances the absorption intensity of light. The as-obtained CuO core-shell nanospheres were evaluated for the degradation of hazardous organic contaminants in water such as phenol and methylene blue (MB) under visible light irradiation. Compared with other CuO products, the as-prepared CuO core-shell nanosphere possesses superior property on photocatalytic decomposition of phenol and MB. It is believed that the efficient photocatalytic property of the as-prepared CuO core-shell nanosphere is originated from its unique openly core-shell nanostructure, which is highly beneficial to the reagent diffusion, mass transportation and the light reflection and absorption inside the CuO nanostructure. (C) 2015 Elsevier B.V. All rights reserved.