In this paper we report the first example of hybrid materials based on poly(methlymethacrylate) (PMMA) matrices covalently reinforced by MyOx(OH)w(O(O)CR)z oxoclusters (M=Zr or Hf), used as heterogeneous catalytic systems for hydrogen peroxide activation. The resulting hybrids were used to catalyze the oxidation of dibenzothiophene (DBT) to the corresponding sulfoxide (DBTO) and sulfone (DBTO2), in order to demonstrate their potential application for the oxydesulfurization (ODS) of a fuel. Thanks to catalyst confinement and to the higher affinity of the polymeric matrix towards polar substrates, the heterogeneous set-up displays improved performances with respect to the corresponding homogeneous systems. At 65°C, a DBT conversion higher than 84% was obtained in 24h, with a >94% selectivity for DBTO2. The stability of the hybrid materials under catalytic conditions was successfully assessed by a combined spectroscopic approach, based on FT-IR, resonance Raman, Solid State Nuclear Magnetic Resonance, X-ray Absorption and Small Angle X-ray scattering measurements.