Three different types of metal-organic polymers have been prepared by a solution diffusion process carried out at room temperature. Crystals of the copper coordination polymers [CuX(4,4′-bipy)]n (X = Cl, Br, I) have been obtained by the reaction of 4,4′-bipyridine ligands with Cu2X2 fragments to yield a three-dimensional network consisting of four interlocking planar lattices. Single crystals of [Cu2(1,2,4,5-BTC)(DMF)2]n (1,2,4,5-BTC = 1,2,4,5-benzene tetracarboxylate) have been grown by slow diffusion from solutions of a mixture of CuBr2, 2,2′-dithiosalicylic acid, and sodium azide plus a mixture of 1,2,4,5-H4BTC and 4-cyanopyridine. The complex [Co(1,3,5-BTC)(4,4′-bipy)]n (1,3,5-BTC = 1,3,5-benzene tricarboxylate) has a 3D open framework structure involving terminal cobalt atoms plus bridging 1,3,5-BTC and 4,4′-bipyridine ligands.