Ordered mesoporous Co3O4(3D) and Pd/Co3O4(3D) were prepared by a nanocasting route using mesoporous silica (KIT-6) as a hard template. In addition, Pd/Co3O4(3DL) was prepared as a reference by post-impregnation of Pd in Co3O4(3D). All catalysts were tested for the total oxidation of o-xylene in the temperature range of 150-300 degrees C. The mesoporous Co3O4(3D) showed better activity than bulk Co3O4 (B) for o-xylene oxidation. As for Pd-loaded samples, Pd/Co3O4(3D) had much higher activity than Pd/Co3O4(3DL). These catalysts were characterized by BET, XRD, TEM, XPS, H-2-TPR and XAFS methods. The characterization results show that the Pd/Co3O4(3D) synthesized by in situ nanocasting presented a more ordered mesostructure and more well-dispersed PdO species than the Pd/Co3O4(3DL) prepared with the post-impregnation method, which account for its excellent activity for o-xylene oxidation. In addition, it was demonstrated that Pd in the oxidized state is the active site for o-xylene oxidation. (c) 2013 Elsevier B.V. All rights reserved.