Poly[[dodeca-aqua-(μ(4)-benzene-1,4-dicarboxyl-ato)(μ(2)-4,4'-bipyridine-κ(2)N:N')dicerium(III)] bis-(benzene-1,4-dicarboxyl-ate)].

The asymmetric unit of the title compound, {[Ce(2)(C(8)H(4)O(4))(C(10)H(8)N(2))(H(2)O)(12)](C(8)H(4)O(4))(2)}(n), consists of half a Ce(III) cation, a quarter of a coordinated benzene-1,4-dicarboxyl-ate (bdc(2-)) dianion, a quarter of a 4,4'-bipyridine (bpy) mol-ecule, three water mol-ecules and a half of an uncoordinated benzene-1,4-dicarboxyl-ate dianion. The Ce(III) ion is located on a twofold rotation axis and exhibits a distorted trigonal prism square-face tricapped coordination geometry. The coordinated and uncoordinated bdc(2-) ions and the bpy mol-ecule lie about special positions of site symmetries 2/m, m and 2/m, respectively. The Ce(III) ions are bridged by the bdc(2-) and bpy ligands, giving a sheet structure parallel to the ac plane. The uncoordinated bdc(2-) dianion exists between the sheets and links the sheets by inter-molecular O-H⋯O hydrogen bonds between the uncoordinated bdc(2-) and coordinated water mol-ecules. A π-π stacking inter-action between the uncoordinated bdc(2-) dianion and the bpy ligand [centroid-centroid distance = 3.750†(4)†à ] is also observed.