Two copper(II) coordination polymers [Cu(atza) 2 ] n ·2nH 2 O (1) and [Cu(atza) 2 (4,4′-bipy) 0.5 ·H 2 O] n (2) [atza=5-aminotetrazole-1-acetato] have been synthesized and characterized by X-ray diffraction analysis, element analysis and IR spectra. Compound 2 is a offspring from reaction of a preformed compound 1 with 4,4′-bipyridyl. The two connected modes of the 2D network layered are provided through μ-atza and/or 4,4′-bipyridyl bridges, and forming 3D supramolecular structures by hydrogen bonding interactions. The dehydration and rehydration processes of compound 1 was investigated