Six copper–lanthanide heterometallic coordination polymers (CPs) [LnCu(2,3-pydc)2(HCOO)(H2O)3]·H2O [Ln=La (1), Pr (2), Nd (3), Sm (4), Eu (5), and Gd (6), 2,3-H2pydc=pyridine-2,3-dicarboxylic acid] were synthesized successfully by the reactions of 2,3-H2pydc with LnCl3·nH2O and Cu(NO3)2·3H2O under solvothermal conditions of H2O–DMF or H2O–DMF–MeOH. They were structurally characterized by single-crystal X-ray diffraction and powder X-ray diffraction (PXRD). CPs 1–6 possess isostructural 2D (4,4) layer architectures built from the dinuclear Ln2(HCOO)2 and Cu2(2,3-pydc)4 units. The reaction solvents have an important effect on the formation of 1–6. The electrochemical properties of 1–6 were investigated.