Fabrication and photocatalytic properties of spheres-in-spheres ZnO/ZnAl2O4 composite hollow microspheres

► S@S-ZnO/ZnAl2O4 microspheres have been fabricated via one-pot hydrothermal method. ► The formation of S@S-ZnO/ZnAl2O4 relies on the molar ratio of glucose to metal ion. ► The coupling of the ZnO and ZnAl2O4 enhanced photocatalytic performance. ► S@S-ZnO/ZnAl2O4 microspheres show superior photocatalytic activity. ► The synthesis strategy of composite materials with complex structure may be proposed.