A unique 3D fourfold interpenetrated metal-organic framework, [Co(L)(H2O)(2)]center dot H2O (1), has been synthesized by the solvothermal reaction of H2L with Co(NO3)(2)center dot 6H(2)O (H2L = 5-(isonicotinamido)isophthalic acid). Compound 1 crystallizes in the monoclinic space group P2(1)/c, with the cell parameters: a = 81301(8), b = 107711(11), c = 167697(16) angstrom, beta = 92.656(2)degrees, V = 14669(3) angstrom(3), R-1 = 0.0325 and wR(2) = 0.0833. Its framework has (10,3)-b topology, where the cobalt atoms are alternately bridged by the pyridyl and the carboxylate groups of the L2- lig...