Poly[aqua-[µ(3)-4-carb-oxy-2-(pyridin-4-yl)-1H-imidazole-5-carboxyl-ato-κN,O:N,O:N]nickel(II)].

The water-coordinated Ni(2+) cation in the title compound, [Ni(C(10)H(5)N(3)O(4))(H(2)O)](n), assumes an octa-hedral NiN(3)O(3) coord-ination mode and is N,O-chelated by two deprotonated 2-(pyridin-4-yl)-1H-imidazole-4,5-dicarb-oxy-lic acid (HPyImDC(2-)) ligands, forming a layer structure extending in the bc plane. The chains are arranged along the b-axis direction, forming a layer structure extending in the bc plane. O-H⋯O hydrogen bonding between the layers results in the formation of a three-dimensional supra-molecular framework. The structure is isotypic with the Zn analogue [Li et al. (2009). Cryst. Growth Des.6, 3423-3431].