CuO/[Si]MCM-41 catalysts with various Si/Cu molar ratios were prepared and characterized by X-ray diffraction, nitrogen physisorption, temperature-programmed reduction by H-2, and UV-vis and Raman spectroscopy. The effects of copper loading and pH on their activity in the decolorization of methyl orange were studied in a heterogeneous Fenton-like process. With decreasing Si/Cu ratio, dye decolorization increased from 18 to 75 % at pH 3. CuO/[Si]MCM-41 catalysts showed 75, 50, and 40 % conversion of methyl orange at pH 3, 5, and 7, respectively. This is a significant improvement to Fenton-like reactions involving copper, and thus CuO/[Si]MCM-41 catalysts are quite promising for pollutant degradation.