A OD discrete molecule [Co(3,5-pdc)(H2O)(5)]center dot 2H(2)O (1) was obtained in quantitative yield from the reaction Of CoCl2 center dot 6H(2)O and pyridine-3,5-dicarboxylate (3,5-pdc) in pure water solvent at ambient temperature. While a 1D zigzag chain species, [{Co(3,5-pdc)(H2O)(4)}center dot H2O](n) (2), was produced in a water-rich environment, a 2D layer compound, [Co(3,5-pdc)(H2O)21, (3), with a 6(3) topology Was generated under a water-reduced condition and a 2D sheet structure, [{Cu(3,5-pdc)(py)(2)}center dot H2O-EtOH](n) (4), was formed under a water-poor condition. Compounds 1, 2, and 4 were characterized by single-crystal X-ray diffraction analysis. The 1D zigzag chain 2 shows a recoverable collapsing property. Compound 4 adopts a 2D sheet structure with a 4.82 topology, observed for the first time for the 3,5-pdc-related metal-organic frameworks. Water content was found to be an important factor in determining the topologies of the products in the self-assembly of divalent metal ions (CO2+, Cu2+) and pyridine-3,5-dicarboxylate under mild conditions.