The suitability of the computer package LUMPAC to calculate the photoluminescence properties of metal–organic frameworks was assessed by considering three systems based on the ditopic 1,4-phenylenebis(methylene)diphosphonic acid (H4pmd) ligand and Ln3+ ions, namely, [Eu(Hpmd)(H2O)] (1), [La2(H2pmd)(pmd)(H2O)2] (2) and [La2(H2pmd)3(H2O)12] (3, previously reported) and their isotypical materials doped with Eu3+ cations, [(La0.95Eu0.05)2(H2pmd)(pmd)(H2O)2] (4) and [(La0.95Eu0.05)2(H2pmd)3(H2O)12] (5). These materials were prepared, and their structures and luminescence properties were characterized. A straightforward approximation based on the simple crystallographic structural subunits of these materials was used and resulted in an excellent agreement between the calculated and experimental properties. The intramolecular energy transfer and back-transfer rates were predicted, and the T1 5D1 channel was shown to be the dominant pathway (9.03 × 104 s–1 for 1, 1.06 × 104 s–1 for 4 and 2.18 × 105 s–1 for 5).