Two new layered polymeric frameworks have been synthesized under different hydrothermal conditions and characterized by single-crystal X-ray diffraction, thermal analysis, and variable temperature-Fourier Transform Infrared Spectroscopy.(VT-FTIR). The compound I, with formula [Er-2(dms)(3)(H2O)(4)], has a triclinic cell with parameters a=5.8506 angstrom, b=9.8019 angstrom, c=11.9747 angstrom, alpha=70.145 degrees, beta=80.234 degrees, and gamma=89.715 degrees, and the compound II, [Er-2(dms)(3)(H2O)], is monoclinic and its cell parameters are a=11.1794 angstrom, b=18.2208 angstrom, c=12.7944 angstrom, beta=112.4270 degrees, where dms=2,2-dimethylsuccinate ligand. A theoretical study including energy calculations of the dms conformers was carried out at the Density Functional Theory (DFT-B3LYP) level of theory, using the 6-311G* basis set. Further calculations of the apparent formation energies of I and II crystalline structures were performed by means of the periodic density functional theory, using DF plane-waves. The analysis of the structural features, theoretical relative stabilities, and the influence of synthesis conditions are presented here. The heterogeneous catalytic activity of the new compounds is tested and reported.