Coordination Polymers Constructed from Polycarboxylic Acids and Semi-Rigid Bis-pyridyl-bis-imide Ligands: Synthesis, Structures and Iodine Adsorption

Reactions of N,N′-bis(3-pyridylmethyl)-pyromellitic diimide (L1) or N,N’-bis(3-pyridyl)bicyclo(2,2,2,)oct-7-ene-2,3,5,6-tetracarboxylic diimide (L2) with 1,3,5-benzenetricarboxylic acid (1,3,5-H3BTC), 4,4′-sulfonyldibenzoic acid (H2SDA), or 4,4′-oxybisbenzoic acid (H2OBA) and divalent metal salts afforded {[Co(1,3,5-HBTC)(H2O)2(L1)]·H2O}n, 1, {[Co(1,3,5-HBTC)(H2O)3(L1)0.5]·H2O}n, 2, {[Co(SDA)(L1)0.5]·H2O}n, 3, {[Co(1,3,5-HBTC)(H2O(L2))]·H2O}n, 4, {[Ni(1,3,5-HBTC)(H2O)(L2)]·H2O}n, 5, [Ni(SDA)(L2)]n, 6, and [Ni(OBA)(L2)]n, 7, which were structurally characterized by using single-crystal X-ray diffraction. Complexes 1 and 2 are 1D chains with the 2,4C6 and 2,3C2 topologies, respectively, and 3 is a 2D layer with the 4,5L51 topology, whereas 4 and 5 are 1D chains with the 2,4C6 topology and 6 and 7 are 2D layers with the 2,4L2 topology. Complex 3 shows a better iodine-adsorption factor of 133.77 mg g−1 at 75 °C for 24 h than 5–7, revealing that the pi-pi conjugation of the dipyridyl ligand may govern the iodine adsorption capacity.