A luminescent lanthanide metal-organic framework (MOF) based on Eu³⁺ and Tb³⁺ ions with 2-phenylsuccinate (EuTb-psa) was obtained solvothermally to explore its behavior as a temperature sensor in an unconventional temperature range through the study of the thermal evolution of the hypersensitive 4f–4f⁵D₀→⁷F² transition and the luminescence lifetime. The efficiency of the luminescence process was evaluated through the europium intrinsic quantum yield (QEu), and its variation as a function of temperature is also reported. The optical properties of four isostructural compounds (Pr-psa, Nd-psa, Gd-psa, and Tb-psa) were investigated and compared with those of related compounds. The energy of the triplet state of the ligand was also estimated. The samples were fully characterized by single-crystal and powder X-ray diffraction, thermal analysis, and vibrational spectroscopy. The heterogeneous catalytic activities of a series of Ln-psa MOFs (with Ln = Sm, Eu, Gd, Tb, EuGd, and EuTb) were evaluated in a one-pot cyanosilylation with benzaldehyde as the substrate.