The architectural structures of MOFs provide special properties as high thermal and mechanical stability, high surface areas and large pore sizes with potential applications in diverse areas. Rare Earth Elements (REEs) are widely used in the various disciplines: luminescent compounds, catalysis, coordination chemistry, solid state chemistry, organometallic compounds, and environmental chemistry. For environmental protection, the elimination of toxic metals from wastewaters previously releasing into the environment are required. Phosphonate MOFs were obtained in our labs by the reaction of divalent inorganic sulphates with phosphonoacetic acid (Cp) or styrylphosphonic (Sp) in hydrothermal conditions and characterized by FTIR and TGA. The phosphonate MOFs were used in the removal process of Cs(I) and Tl(I) ions from aqueous solutions done in batch mode, varying the initial concentration of the metal ions, keeping for all the samples a solid: liquid ratio of 1 g/L. From the experimental data were observed that the adsorption capacity developed by the studied materials increase in the following order: CuCp < CoCp < CoSp, both for the removal of Cs(I) ions and also for the elimination of Tl(I) ions. The adsorption kinetics was better described by pseudo-second-order kinetic model compare to pseudo-first-order model. The experimental data showed good fit to the Langmuir isotherm.