A facile and green method was utilized to synthesize core-shelled Zn / ZnO microspheres by boiling Zn microparticles in water for improving the photocatalytic activity of ZnO . The synthesized Zn / ZnO core-shells were investigated by means of scanning electron microscope, X-ray diffractometer and photoluminescence spectrometer, respectively. The morphology analysis showed that the metallic Zn core was about 6 μm in diameter while the ZnO shell was about 600 nm in thickness. Compared to ZnO nanoparticles, the core-shelled Zn / ZnO microspheres exhibited improved photocatalytic activity in degrading methyl orange in water. Our results suggest that the metal–semiconductor junction formed at the Zn / ZnO interface is responsible for the enhanced photocatalytic activity of ZnO .