Dehydroxylated silica was modified by grafting reaction of SiHMe2 groups. The resulting material was fully characterized by various methods including infrared and one- and two-dimensional solid-state NMR. This material can further react with dehydrated polyoxometalates (POMs), leading to the formation of a covalent POM-silica bond. In the case of H4PVMo11O40, hydrogen released during the grafting reaction reduces the POM. This leads to the formation of two surface species, which can be reoxidized in presence of oxygen. In the case of H3PW12O40, no reduction is observed. In both cases, (29)Si solid-state NMR shows that the POM-silica bond is covalent, contrary to what was observed in homogeneous conditions.