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 H2O2via reduction sensing.