1,2,4,5-Benzenetetracarboxylic acid (btcH(4)) reacts with Cu(NO3)(2). 6H(2)O to form 2D coordination polymeric structure {[Cu-2(btc)(Py)(4). 2H(2)O].4H(2)O}(n), 1, in the presence of pyridine from water at room temperature. Puckered-boat-shaped hexameric water clusters resulting from four free water molecules and two water molecules coordinating to metal ions join these sheets to make a 3D network. These water clusters behave as pillars to join those sheets which is the key factor stabilizing the 3D network. Thermal analysis, X-ray powder diffraction, and X-ray structure analysis have been used to characterize this compound. Crystal data for 1 follow: triclinic space group P (1) over bar, a = 8.905(3) Angstrom, b = 11.137(4) Angstrom, c = 17.484(2) Angstrom, , alpha = 82.342(6)degrees, beta = 81.312(3)degrees, gamma = 82.361(4)degrees V = 1687.5(1)Angstrom(3), Z = 2, R1 = 0.0331, wR2 = 0.0886, S =1.066.