Four different dimensional Zn(II) coordination polymers as fluorescent sensor for detecting Hg²⁺, Cr₂O₇^2- in aqueous solution

Highlights: • Four Zn-based coordination polymers were solvethermally synthesized. • Compound 1 and 2 could mutual conversion between different solvent ratios. • Both 1 and 2 exhibit high selectivity for Cr₂O₇^2- and Hg²⁺ ions in aqueous solution. • The mechanism of sensing properties were discussed in details. - Abstract: Four Zn(II) coordination polymers (CPs), [Zn(4-pzpt)₂(H₂O)]_n (1), {[Zn(4-pzpt)₂]·CH₃OH}_n (2), [Zn₂(4-pzpt)₂(suc)(H₂O)]_n (3) and [Zn₂(4-pzpt)₂(ndc)]_n (4) were obtained from 3-(pyridin-4-yl)-5-(pyrazin-2-yl)-1H-1,2,4-triazole (4-Hpzpt), 1,4-Naphthalenedicarboxylic acid (H₂ndc) and succinic acid (H₂suc) ligands. Structural analysis reveals that 1 represents a five coordinated 0D structure. 2 possess a network featuring 2D 4⁴ grid-like layers structure. 3 displays a network featuring 2D (6³)-hcb layered structure. 4 shows a rare 3D (4,4)-connected topology with a Schläfli symbol of (4.6^4.7)₂(6^4.7²). Complexes 1 and 2 can mutual conversion between different solvent ratios. Luminescence properties reveal that 1 and 2 exhibit excellent selectivity for Hg²⁺ and Cr₂O₇^2- ions in aqueous solution, in which suggests that 1 and 2 is a promising multifunctional sensing materials. The possible sensing mechanism is also discussed.