Construction of a new ionic Co(II) coordination polymer and its composite with CNTs showing dual electrochemical sensing to AA and Fe3+

A new ionic cobalt(II) chain coordination polymer, {[Co(bbbm)(H₂O)₄]·ATBIP·2DMA·2H₂O}_n (Co-CP) with the multi-functional 5-amino-2,4,6-tribromoisophthalic acid (H₂ATBIP) and flexible linker 1, 4-bis(benzimidazole-1-methyl)benzene (bbbm) was prepared with convenient slow evaporation method. Moreover, its composite with hydroxyl carbon nanotubes (CNTs) (Co-CP@CNTs) was constructed by “one pot” synthesis. Co-CP further assembles into a 3D supramolecular framework with 1D channels with the aid of the hydrogen-bonded tape. The amperometric response demonstrates that Co-CP/GCE and Co-CP@CNTs/GCE show sensitive and selective electrochemical oxidation sensing to ascorbic acid (AA) and reduction sensing to Fe³⁺ in 0.1 M H₂SO₄, respectively. Moreover, Co-CP@CNTs exhibits better electrocatalytic capability for the oxidation sensing of AA and reduction sensing of Fe³⁺ than that of Co-CP. Remarkably, the strategy was successfully applied in the portable screen-printed electrode (SPE). Among three electrodes, the Co-CP@CNTs/SPE shows the most rapid and sensitive sensing with the largest exponential range of 0.01 - 26 mM for AA and 0.01 - 21 mM for Fe³⁺, respectively. The limits of detection (LOD) reach to 0.74 μM (AA) and 0.96 μM (Fe³⁺) for Co-CP@CNTs/GCE, 0.32 μM (AA) and 0.91 μM (Fe³⁺) for Co-CP@CNTs/SPE, respectively. Furthermore, the portable Co-CP@CNTs/SPE has been successfully used as a platform for the practical detection of AA and Fe³⁺ in the real-world samples.