Trivalent lanthanide Ln³⁺ ions have unique photophysical properties and their organic frameworks (LnMOFs) are relevant for many applications. These and other properties are dependent upon the interactions between the Ln³⁺ ions, which are ubiquitous in LnMOF. Therefore, they are interesting platforms to study these interactions. Pentafluorobenzoic acid (LH) is a strong acid (pK_a = 1.48) that can yield coordination compounds (mono and dinuclear and MOFs) with Ln³⁺ ions. Open synthesis at room-temperature and at 80 °C and liquid-assisted gridding (LAG) mechanochemical method were employed to synthesize the dimer [Ln₂(L)₆(H₂O)₈](H₂O)₂ (Ln = Eu, Gd, Tb) that is already described as well as a new mixed Eu-GdMOF [Ln(L)₂(LH)(H₂O)₄](Cl)(LH)(H₂O)₂. It structure, determined by crystallography, is quite unusual, because the Ln centers are connected by a single symmetric bridge ligand and a Ln-Ln distance of 6.865 Å, which has not been observed in frameworks of lanthanide-benzoates. The crystal asymmetric unit does not possess an inversion center, however, the crystal packing composed of four asymmetric units does present a center of inversion. Upon excitation at wavelengths larger than 277 nm, the emission intensity of the ⁵D₀ → ⁷F₂ transition in the EuMOF is less intense than the ⁵D₀ →⁷F₁, transition suggesting the presence of an inversion center. However, for the heteronuclear Eu-GdMOF presents the typical ⁵D₀ → ⁷F_J (J = 0 - 4) transitions, with ⁵D₀ → ⁷F₂ being more intense than ⁵D₀ →⁷F₁. These changes in the relative intensities suggest that (i) the Eu-GdMOF was obtained and the inversion center in the unit cell is no longer present because the replacement of Eu³⁺ by Gd³⁺, and (ii) the interactions between the Eu³⁺ ions are sufficiently strong for the four asymmetric units to behave as a single effective emission center. In the mixed Eu-TbMOF, the typical ⁵D₀ → ⁷F_J (J = 0 - 4) transitions of Eu³⁺ and ⁵D₄ → ⁷F_J (J = 6 - 1) of Tb³⁺ were observed upon excitation at the ligand states. The excitation spectra present a band due to the ⁷F₆ → ⁵D₄ Tb³⁺ transition when the emission were monitored at ⁵D₀ → ⁷F₂ or at ⁵D₄ → ⁷F₅, indicating energy transfer from Tb³⁺ to Eu³⁺ ions. The reverse energy transfer Eu³⁺ → Tb³⁺ was not observed either in the emission or the excitation spectra. The X-ray data as well as the luminescence results showed that the structure of the coordination compounds (dinuclear and MOF) depends on the synthetic method, that the Eu³⁺ ions interact strongly even at distances of ca. 7 Å, and that Tb³⁺ transfer energy to Eu³⁺ ions. In addition to the novelty of the LnMOF and mixed LnLn’MOFs, their photophysical properties are being explored in several applications.