We demonstrate a supercritical CO2 (scCO(2)) deposition method to synthesize mesostructured Co3O4 with crystalline walls using SBA-15 as the hard template. By variation of the scCO(2) pressure, randomly organized nanorods or a highly ordered mesoporous structure of Co3O4 is obtained after only one filling operation. The catalytic tests show that the randomly organized Co3O4 nanorods display excellent activity for CO oxidation with the complete conversion of CO even at room temperature, while neither the ordered mesoporous nor bulk Co3O4 is active at this low-temperature, demonstrating the important role of Co3O4 morphology in catalysis.