The three-dimensional coordination polymer [Eu(ptc).3H2O]n has been synthesized under hydrothermal conditions and characterized by powder X-ray, infrared, and thermogravimetric analyses. The compound crystallizes with cell parameters a = 12.127, b = 7.409, and c = 13.672 and cell volume = 1220.77 Å. This article presents an experimental and theoretical study to elucidate the structure of IR-LOFs by means of the Sparkle/PM3 quantum chemical model. For lanthanides, the Sparkle/PM3 model can predict the geometries of lanthanide complexes in cases when the central Ln3+ is directly coordinated to other atoms, like oxygen and nitrogen. Overall, the theoretical results obtained herein agree well with the experimental data. For the first time, the intensity parameters (Ω2, Ω4, and Ω6) of the LOF [Eu (ptc).3H2O]n have been calculated by using the Sparkle/PM3 structure and employed to determine the energy transfer (WET) and the back-transfer (WBT) rates. The intensity parameters have been used to predict the radiative decay rate.