The selective oxidation of organic compounds using heterogeneous catalysts is a major challenge in chemical industries and catalytic studies. Our research group has recently been evaluating metal-doped porous silica substrates as oxidation catalysts using peroxide as the oxygen source. This talk will focus on heterogeneous catalysis using acid-prepared mesoporous silica loaded with 1-5 wt% of the polyoxometalate H₅PV₂Mo₁₀O₄₀ ("POM-APMS"). Characterization by powder XRD, N₂ physisorption, IR, UV-Vis and 31P NMR showed the presence of isolated POM species at lower loadings. However, at higher loadings the surface areas and pore volumes of the catalysts decreased, indicating that the pores were becoming occluded by larger crystallites. A POM loading of 3 wt% produced the most active oxidation catalyst using tert-butyl hydroperoxide (TBHP) as the oxidant. All the reactions were performed under mild conditions. Characterization data, as well as the results of several reactions types including the selective oxidation of sulfides to sulfoxides, styrene to styrene oxide, and benzyl alcohol to benzaldehyde, will be presented.