Highly selective sensing of Fe3+/Hg2+and proton conduction using two fluorescent Zn(ii) coordination polymers

A pair of homologues, [Zn(Hssa)(1,4-bib)center dot H2O](n)(1) and [Zn-3(ssa)(2)(1,4-bib)(3)center dot 4H(2)O](n)(2), were successfully assembled using the same metals and ligands [H(3)ssa = 5-sulfosalicylic acid; 1,4-bib = 1,4-bis(1H-imidazol-1-yl)benzene] under solvothermal conditions. Polymer 1 is a two-dimensional (2D)sqlnetwork and polymer 2 is a three-dimensional (3D) framework. Polymer 2 can be simplified into two topology types:bctandtfc. The two polymers show significant differences in the fluorescence sensing of metal ions and proton conductivity. Their applications in detecting metal ions and proton conductivity were explored. Polymer 1 shows high sensitivity and selectivity for Fe3+, while polymer 2 can detect Hg2+ ions. The limit of detection was 1.66 mu M with Fe3+ for 1 and 0.23 mu M with Hg2+ for 2 in water. In addition, both 1 and 2 exhibit high water stability and proton conductivity. At 60 degrees C and 95% relative humidity, their conductivities were 3.45 x 10(-5) and 6.26 x 10(-6)S cm(-1), respectively. A detailed analysis of the Hirshfeld surface and fingerprints was carried out for 1 and 2 to compare the interactions between the molecules, which is essential for analysing the relationship between their structures and material properties.