Isotype 1D polymers of cobalt(II) or zinc(II) constructed with square-planar tetraaqua-metal(2+) units and the bis-zwitterionic form of the μ2-O,O′-trans-1,4-dihydrogen-cyclohexanediaminotetraacetate(2−) ligand

► Synthesis and crystal structure of trans-1,4-H4CDTA acid are reported. ► Bis-zwitterionic trans-1,4-H2CDTA2− anion acts as bridging-dicarboxylate ligand. ► Crystal structures show the isotype nature of Co(II) and Zn(II) 1D-polymers. ► A bis-zinc 3D-coordination polymer guests H-bonded water in channels. ► Aqua ligands and noncoordinated water are removing in an overlapped step.