TiO2 and Sn-doped TiO2 materials were prepared by sol-gel method using titanium and tin alkoxides at different Sn concentration (0.1 mol%, 0.5 mol%, 1 mol%, 3 mol% and 5 mol%). Samples were characterized by thermo gravimetric analyzer with differential scanning calorimeter (TGA-DSC), X-ray Rietveld refinement, N2 adsorption (BET), transmission electron microscopy (TEM), UV-vis spectroscopies technology and Raman spectroscopy. Only anatase phase was observed in pure TiO2, whereas anatase and brookite were obtained in Sn-doped TiO2 samples. Sn dopant acts as a promoter in phase transformation of TiO2. The Rietveld refinements method was used to determine the relative weight of anatase and brookite, and crystallite size as a function of Sn concentration after calcination of samples at 673 K. It was also demonstrated the incorporation of Sn4+ into the anatase TiO2 structure. Sn4+ inhibits the growth of TiO2 crystallite size, which leads to an increase of the specific surface area of TiO2. From XRD analysis, the solid solution limit of Sn4+ into TiO2 is 5 mol% Sn. The photocatalytic activity on Sn4+ doped TiO2 was determined for the 2,4-dichlorophenoxyacetic acid reaction. The maximum in activity was attributed to the coexistence of anatase and brookite phases in the appropriate ratio and crystallite size.