A series of coordination polymers with anionic, cationic, and neutral metal-carboxylate frameworks have been synthesized by using a flexible tetrapodal ligand tetrakis[4-(carboxyphenyl)oxamethyl] methane acid (H4X). The reactions between divalent transition-metal ions and H4X ligands gave [M3X2]center dot[NH2(CH3)(2)](2)center dot 8DMA (M = Co (1), Mn (2), Cd(3)) which have anionic metal-carboxylate frameworks with NH2(CH3)(2)(+) cations filled in channels. The reactions of trivalent metal ions Y(III), Dy(III), and In(III) with H4X ligands afforded cationic metal-carboxylate frameworks [M3X2 center dot(NO3)center dot(DMA)(2)center dot(H2O)]center dot 5DMA center dot 2H(2)O (M = Y(4), Dy(S)) and [In2X center dot(OH)(2)]center dot 3DMA center dot 6H(2)O (6) with the NO3 and OH serving as counterions, respectively. Moreover, a neutral metal-carboxylate framework [Pb2X center dot(DMA)(2)]center dot 2DMA (7) can also be isolated from reaction of Pb(II) and H4X ligands. The charged metal-carboxylate frameworks 1-5 have selectivity for specific counterions in the reaction system, and compounds 1 and 2 display ion-exchange behavior. Moreover, magnetic property measurements on compounds 1, 2, and 5 indicate that there exists weak antiferromagnetic interactions between magnetic centers in the three compounds.