Syntheses, Gas Adsorption, and Sensing Properties of Solvent-Controlled Zn(II) Pseudo-Supramolecular Isomers and Pb(II) Supramolecular Isomers

On the basis of the bifunctional 1,4-bis(imidazol-1-yl)terephthalic acid (H2BTA), four three-dimensional (3D) Pb(II)/Zn(II) coordination polymers (CPs), {[Zn(BTA)]·1.5(DOA)}n (1), [Zn(BTA)]n (2), [Pb(BTA)]n (3), and [Pb(BTA)]n (4), have been synthesized (DOA = dioxane). Structural analyses reveal that two Zn(II)-based complexes are 3D (4,4)-c pts pseudo-supramolecular isomers for 1 and 2, and two Pb(II)-based complexes are supramolecular isomers with a 3D (4,5,6)-c net for 3 and a 3D 6-c pcu net for 4, respectively. Furthermore, the gas adsorption behaviors of complexes 1 and 2 for N2, CO2, and CH4 have been studied in detail at varying temperatures, and the results showed that the adsorption capacities to CO2 at 273 K and 1 bar are stronger than those of other gases. Meanwhile, the selectivity of 1 and 2 for CO2/CH4 was evaluated by the usage of the ideal adsorbed solution theory, whose selectivity exceeded those of reported MOFs under similar conditions. In addition, the fluorescent measurements showed that 1–4 present high sensitivity and selectivity for Fe3+/Cr2O72– ions. And the possible fluorescence sensing mechanism of CPs to Fe3+ and Cr2O72– ions was also examined.