Construction of Cucurbit[6]uril-Based Coordination Polymers Incorporating Multiaromatic Ligands with Amide Linkages and Their Iodine Adsorption Properties

To build high-dimensional cucurbit[n]uril-based (Q[n]) coordination polymers, the introduction of a second ligand has been proven to be a feasible strategy. In this work, we employed the multiaromatic carboxylate ligands with amide linkages, 4,4 ',4 ''-[1,3,5-benzenetriyltris(carbonylimino)]trisbenzoic acid (H(3)BTTA) and bis(3,5-dicarboxyphenyl)terephthalamide (H(4)BDTA), as the second ligand to react with Q[6] and KCl or CaCl2 to obtain four novel Q[6]-based coordination polymers successfully with formulas {[Ca(H2O)(2)(HBTTA)(Q[6])]<middle dot>11H(2)O} (1), {[Ca-2(H2O)(5)(CH3OH)(BTTA)(Q[6])]<middle dot>Cl<middle dot>24H(2)O} (2), {[K-2(H2O)(5)(BDTA)(0.5)(Q[6])]<middle dot>17H(2)O} (3), and {[Ca-2(H2O)(6)(BDTA)(Q[6])(0.5)]<middle dot>6H(2)O} (4). According to the crystal structural analysis, the coordination among the central metal cations K+/Ca2+, Q[6] molecules, and carboxylate ligands generates one-dimensional (1D) coordination chains in complex 1 and two-dimensional (2D) coordination networks in complexes 2-4, respectively, in which complex 2 displayed accessible one-dimensional (1D) channels along the a-axis. Meanwhile, the outer-surface interactions of Q[6] with the carboxylate ligands play an essential role in the formation of the final supramolecular three-dimensional (3D) frameworks of these complexes. Furthermore, the iodine adsorption properties of these four complexes were investigated and the results indicated that complex 2 was capable of effectively removing iodine from hexane and aqueous solution, while the other three complexes displayed no distinct absorption capacity for iodine, which may be related to the presence of 1D channels in complex 2.