Poly[[triaqua­(μ(3)-4-oxidopyridine-2,6-dicarboxyl­ato)holmium(III)] mono­hydrate]

In the title coordination polymer, {[Ho(C(7)H(2)NO(5))(H(2)O)(3)]·H(2)O}(n), the Ho(III) atom is eight-coordinated by a tridentate 4-oxidopyridine-2,6-dicarboxyl­ate trianion, two monodentate anions and three water mol­ecules, forming a distorted bicapped trigonal–prismatic HoNO(7) coordination geometry. The anions bridge adjacent Ho(III) ions into double chains. Adjacent chains are further connected into sheets. O—H⋯O hydrogen bonds involving both coordinated and uncoordinated water mol­ecules generate a three-dimensional supra­molecular framework.