A new supramolecular compound [Zn(H2EDTA)(H2O)](Q)2(H2O)2 (1), where H4EDTA=ethylenediaminetetraacetic acid and Q=4-(carboxylate)pyridinium, has been prepared by mild hydrothermal reaction and characterized by elemental analysis, IR spectrum and thermogravimetric analysis. Single-crystal X-ray diffraction of 1 [monoclinic, space group C2/c, a=11.310(4) Å, b=9.704(4) Å, c=23.798(10) Å, β=97.401(10)°, Z=4] revealed that the ZnII ion coordinates to the chelating tetradentate ligand H2EDTA and a water molecule, taking a distorted trigonal-bipyramid geometry. The mononuclear [Zn(H2EDTA)(H2O)] subunits are linked to form two-dimensional layered architectures by the lattice water moieties through O–H⋯O hydrogen bonds, which are further extended to a three-dimensional (3D) supramolecular network by 4-(carboxylate)pyridinium guests (resulting from the ring-opening hydrolysis of 2,5-bis(4-pyridyl)-1,3,4-oxadiazole) through extensive hydrogen-bonding interactions. The 3D supramolecular framework is also stabilized by significant face-to-face π–π stacking interactions between the aromatic pyridinium systems. [Copyright &y& Elsevier]