Electrochemical and fluorescence sensing performance of four new coordination polymers tuned by different metal ions and dicarboxylic acids

Abstract

Four new coordination polymers (CPs), namely, [Zn(4-dptb)(2,2′-bha)]·4H₂O (CP 1), [Cd(4-dptb)(4,4′-odpa)(H₂O)₂]·H₂O (CP 2), [Ni(4-dptb)(4,4′-odpa)(H₂O)₂]·H₂O (CP 3), and [Co(4-dptb)(2,2′-bha)]·2H₂O (CP 4) (4-dptb = N³,N⁴-bis(pyridine-4-ylmethyl)thiophene-3,4-dicarboxamide, 2,2′-H₂bha = 2,2′-biphenyl acid, and 4,4′-H₂odpa = 4,4′-oxybisbenzoic acid), were successfully prepared by hydrothermal synthesis. Single-crystal X-ray diffraction, FT-IR spectra, and powder X-ray diffraction (PXRD) were used to characterize CPs 1–4. The synthetic details for CPs 1–4 were discussed, and the effects of metal ions and carboxylic acids on the structures of the title CPs were discussed. CPs 1 and 2 demonstrated excellent fluorescence quenching performance for Cr₂O₇²⁻ and CrO₄²⁻ anions with low limits of detection (LODs), fast response times, and satisfactory recycling stability. Fluorescence quenching mechanisms were further investigated through UV-vis absorption spectra and fluorescence lifetime. Cyclic voltammetry results and the current–time curve were used to investigate the electrochemical sensing properties of CPs 3 and 4 for Cr₂O₇²⁻ ions.