Proton-Conductive and Electrochemical-Sensitive Sensing Behavior of a New Mn(II) Chain Coordination Polymer

In this work, a novel Mn­(II) chain coordination polymer (Mn-CP), {[Mn­(iip)­(2bbpum)0.5(H2O)3]·2H2O} n [H2iip = 5-iodoisophthalic acid, 2bbpum = N,N′-bis­(2-pyridinemethyl)­oxamide] was synthesized under ambient conditions. Mn-CP further assembles into a 3D supramolecular architecture through hydrogen bonds, halogen bonds, and ππ stacking interactions. The composite Mn-CP/nafion membrane has low activation energy for proton transfer, which results in its temperature-insensitive proton conductivity. The cyclic voltammetry demonstrates that the Mn-CP electrode (Mn-CP/GCE) shows quite different redox properties in 0.1 M H2SO4 and 0.1 M PBS aqueous solutions. The Mn-CP/GCE exhibits a couple of irreversible redox peaks with an oxidation peak potential suitable for the nitrite oxidation in 0.1 M H2SO4. Quite differently, in the PBS aqueous buffer solution, the Mn-CP electrode has a couple of irreversible redox peaks. The reduction peak potential is appropriate for the H2O2 reduction. So, the Mn-CP/GCE can be used not only in the electrocatalytic oxidation of NO2 – but also in the electrocatalytic reduction of H2O2. The amperometric response reveals that the Mn-CP/GCE exhibits high-selective and extremely sensitive oxidation sensing of NO2 – and reduction sensing of H2O2. The exponential detection range is 0.01–20 mM for NO2 – and 0.01–10.5 mM for H2O2. The linear detection range for both H2O2 and NO2 – is 0.01–0.10 mM. The detection limit is 1.865 μM for NO2 – and 8.57 μM for H2O2. The Mn-CP/GCE exhibits high electrochemical stability and fine reproducibility. Moreover, the strategy can be translated to a portable screen-printed electrode (SPE). The Mn-CP/SPE shows more sensitive sensing to NO2 – and H2O2 than Mn-CP/GCE. Moreover, it can detect NO2 – and H2O2 efficiently in the real-world samples. So, Mn-CP may be a potential dual nonenzymatic electrochemical sensory material for NO2 – via oxidation sensing and H2O2 via reduction sensing.