Three lanthanide coordination polymers incorporating 5‐hydroxyisophthalate (L) and phen ligands, [Eu(L)(phen)]n (1) and [Ln(L)(phen)2]n [Ln = Sm (2) and Pr (3)], were synthesized. X‐ray structural analysis reveals that 1 features a (3,6)‐connected 3D rtl topology. Complexes 2 and 3 are isostructural and have 2D sheets with 63 topology. Comparison of the structural differences between 1 and 2 (or 3) suggests that the different metal sources play an important role in the formation of such coordination networks. Compounds 1 and 2 show photoluminescence and their emission properties are closely related to their corresponding central LnIII atoms.