Three lanthanide–transition-metal coordination polymers, namely, [Er2L6(H2O)][Cu2I2] (1), [ErL3][CuI] (2), and [Dy2L6(BPDC)0.5(H2O)4][Cu3I2] (3) (HL=4-pyridin-3-yl-benzoic acid, H2BPDC=4,4′-biphenyldicarboxylic acid) have been made by reacting Ln2O3 CuI with HL at different temperatures under hydrothermal conditions. All the complexes are characterized elemental analysis, IR spectroscopy, therm...