Materials belonging to defect pyrochlore structure have been the subject of considerable interest and expected to exhibit fast protonic conduction. The proton exchanged ternary metal oxides of composition HM0.33Te1.67O6 (M = Al, Cr and Fe) are prepared for the first time by ion exchange method at room temperature. These materials are characterized by X-ray Diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectroscopy (UV-vis DRS) and solid state NMR techniques. All the materials are crystallized in a cubic lattice with the Fd - 3m space group. Photocatalytic activity against methyl violet (MV) degradation under visible light irradiation is studied. The mechanistic degradation pathway of MV is studied by a fluorescence technique using terepthalic acid (TA) as a probe and Tertiary butanol (TB) as hydroxyl radical quencher. The dc conductivity of all three compositions is studied in the temperature range 300 – 673 K. The variation of dc conductivity with temperature is explained.