A Series of Cobalt-Based Coordination Polymer Crystalline Materials as Highly Sensitive Electrochemical Sensors for Detecting Trace Cr(VI), Fe(III) Ions, and Ascorbic Acid

Convenient, sensitive, and reliable detection of multiple heavy-metal ions is a significant and challenging task with the use of high-yielding and easily synthesized materials. To solve this challenge, five cobalt-based coordination polymers (CPs), [Co2(4-dptb)2(1,3-BDC)2]·2H2O (1), [Co(4-dptb)(5-DIP)] (2), [Co(4-dptb)(5-NIP)] (3), [Co(4-dptb)(5-AIP)] (4), and [Co(4-dptb)(5-MIP)] (5) (4-dptb = N3,N4-bis(pyridin-4-ylmethyl)thiophene-3,4-dicarboxamide, 1,3-BDC = 1,3-benzenedicarboxylate, 5-DIP = 5-hydroxyisophthalic acid, 5-NIP = 5-nitroisophthalic acid, 5-AIP = 5-methylisophthalic acid, 5-MIP = 5-aminoisophthalic acid), have been synthesized by hydrothermal methods. A remarkable electrochemical sensing for Cr(VI) and Fe(III) was confirmed by cyclic voltammetry (CV) and current–time curves (i–t). The results showed that all CPs have a low limit of detection (LOD) of Cr(VI) and Fe(III) and fast electrochemical responses of within 3 s. At the same time, compounds 1–5 have a significant electrocatalytic oxidation effect on ascorbic acid (AA) and can be used as electrochemical sensors for AA.