In the title complex, [Zn(2)(C(8)H(4)O(4))(C(20)H(11)N(4)O(2))(2)]·4H(2)O, the Zn(II) atom is six-coordinated by two carboxyl-ate O atoms from one bidentate benzene-1,4-dicarboxyl-ate (1,4-BDC) ligand, two carboxyl-ate O atoms from two different monodentate 4-(1H-1,3,7,8-tetra-aza-cyclo-penta-[l]phenanthren-2-yl)benzoate (HNCP) ligands and two HNCP N atoms. The Zn(II) atoms are bridged by the centrosymmetric 1,4-BDC ligands, forming an extended single-chain structure. Neighbouring single chains are connected by the HNCP ligands from two opposite directions, resulting in a sheet. In addition, there are N-H⋯O hydrogen-bonding inter-actions between adjacent layers. As a result, the polymeric sheets are further extended into a three-dimensional supra-molecular structure.