Amorphous, microporous mixed oxides, based on silica with isolated Mn centers in the amorphous silica matrix, were prepared by means of an acid catalyzed sol-gel process. The materials have a narrow micropore distribution with a pore diameter of 0.8 nm. XANES investigations of the materials on the Mn absorption edge provide evidence that isolated octahedrally coordinated Mn-II sites predominate. Further characterizations include XRD, sorption measurements, and light microscopy. The good activity of the new catalysts for the selective oxidation of toluene to benzaldehyde is attributed to the homogeneously distributed manganese in the shape selective environment of the micropores.