Novel ZnO/ZnAl2O4 nanocomposites with ZnAl2O4 nanoparticles homogeneously dispersed inside a network of ZnO are fabricated by thermal treatment of a single-source precursor of ZnAl-layered double hydroxides (ZnAl-LDHs) at 800 degrees C. The effects of the Zn/Al molar ratio of the LDH precursors on the structure, composition, morphology, textural as well as UV-absorbing properties and photocatalytic activities of the nanocomposites are investigated in detail. The results show that the ZnO/ZnAl2O4 nanocomposites derived from the ZnAl-LDHs precursors have superior photocatalytic performances to either single phase ZnO or similar ZnO/ZnAl2O4 samples fabricated by chemical coprecipitation or physical mixing method. The heterojunction nanostructure and the strong coupling between the ZnO and ZnAl2O4 phase derived from ZnAl-LDHs precursors are proposed to contribute the efficient spatial separation between the photo-generated electrons and holes, which can concomitantly improve the photocatalytic activities. (C) 2011 American Institute of Chemical Engineers AIChE J, 58: 573-582, 2012