Effect of Solvent Molecule in Pore for Flexible Porous Coordination Polymer upon Gas Adsorption and Iodine Encapsulation

Four new Zn­(II)-coordination polymers, namely, [Zn₂(μ₆-ao₂btc)­(μ-obix)₂]_<i>n</i> (<b>1</b>), [Zn₂(μ₄-ao₂btc)­(μ-obix)₂]_<i>n</i> (<b>2</b>), [Zn₂(μ₄-ao₂btc)­(μ-mbix)₂]_<i>n</i> (<b>3</b>), and {[Zn₂(μ₄-ao₂btc)­(μ-pbix)₂]·2DMF·8H₂O}_<i>n</i> (<b>4</b>), where ao₂btc = dioxygenated form of 3,3′,5,5′-azobenzenetetracarboxylate and obix, mbix, and pbix = 1,2-, 1,3-, and 1,4-bis­(imidazol-1-ylmethyl)­benzene, have been synthesized with azobenzenetetracarboxylic acid and isomeric bis­(imidazole) ligands and characterized by elemental analyses, IR spectra, single-crystal X-ray diffraction, powder X-ray diffraction, and thermal analyses. X-ray results showed that <b>1</b>, <b>2</b>, and <b>4</b> had two-dimensional structures with 3,4L13 topology, while <b>3</b> was a three-dimensional coordination polymer with bbf topology. For <b>4</b>, two types of activation strategies, solvent exchange + heating (which produced <b>4a</b>) and direct heating (which produced <b>4b</b>), were used to investigate the effect of a guest molecule in a flexible framework. Gas adsorption and iodine encapsulation properties of activated complexes were studied. The CO₂ uptake capacities for <b>4a</b> and <b>4b</b> were 3.62% and 9.50%, respectively, and Langmuir surface areas calculated from CO₂ isotherms were 167.4 and 350.7 m²/g, respectively. Moreover, <b>4b</b> exhibited 19.65% and 15.27% iodine uptake in vapor phase and cyclohexane solution, respectively, which corresponded to 1.47 and 0.97 molecules of iodine/formula unit, respectively. Moreover, photoluminescence properties of the complexes were studied