Poly[[dodeca­aqua­bis­(μ(3)-pyridine-2,6-dicarboxyl­ato)tetra­kis­(μ(2)-pyridine-2,6-dicarboxyl­ato)tri­calciumdieuropium(III)] 10.5-hydrate]

In the title compound, {[Ca(3)Eu(2)(C(7)H(3)NO(4))(6)(H(2)O)(12)]·10.5H(2)O}(n), the Eu(III) ion is nine-coordinated by three tridentate pyridine-2,6-dicarboxyl­ate (PDA) ligands, forming a [Eu(PDA)(3)](3−) building block. The Ca(2+) ions adopt two types of coordination geometries. One Ca(2+) ion, lying on a twofold rotation axis, is eight-coordinated by four carboxyl­ate O atoms from four PDA ligands and four water mol­ecules, and the other two Ca(2+) ions, each lying on an inversion center, are six-coordinated by two carboxyl­ate O atoms from two PDA ligands and four water mol­ecules. The carboxyl­ate groups bridge the Eu(III) and Ca(2+) ions into a three-dimensional porous framework, with channels extending along [010] and [001] in which lattice water mol­ecules are located. Two of the lattice water mol­ecules are disordered over two sets of sites with equal occupancy and one water mol­ecule is 0.25-occupied. Numerous O—H⋯O hydrogen bonds involving the water mol­ecules and carboxyl­ate O atoms are present.