Polyoxometalate-based metal–organic complexes constructed from a new bis-pyrimidine-amide ligand with high capacitance performance and selectivity for the detection of Cr(VI)

In this paper, three new polyoxometalates (POM)-based metal–organic complexes constructed from a new semi-rigid organic ligand N,N'-bis(4-pyrimidinecarboxamido)-1,2-cyclohexane (4-bpmah) H2[Cu(4-bpmah)2(SiMo12O40)(H2O)2]·2H2O (1), H[Cu(4-bpmah)2(PMo12O40)(H2O)2]·2H2O (2) and [Cu(4-bpmah)(H2O)2]·[Cu2(TeMo6O24)(H2O)10]·4H2O (3) were synthesized by hydrothermal method. Single crystal X-ray analyses showed that complexes 1 and 2 were isostructural, in which the isolated Keggin-type [SiMo12O40]4–/[PMo12O40]3– anions and [Cu(4-bpmah)2(H2O)2]2n+ units were expanded into 3D supramolecular structures through hydrogen bond interactions. In complex 3, the 1D [Cu(4-bpmah)(H2O)2]2n+ metal–organic chains and isolated [Cu2(TeMo6O24)(H2O)10]2n– units were expanded into a 3D supramolecular framework by the hydrogen bond interactions. In this paper, carbon cloth working electrodes composited by the title complexes (1/CC, 2/CC and 3/CC) were prepared and used as electrodes for supercapacitors. The performance of supercapacitors as well as the influence of electrolyte solution and title complexes quality load on the performance of supercapacitors were studied. Furthermore, the electrochemistry and electrocatalytic behaviors of complexes 1–3 bulk-modified carbon paste electrodes (1-CPE, 2-CPE and 3-CPE) toward the reduction of KBrO3, KNO2, Cr(VI), as well as their sensing behaviors on Cr(VI) were investigated.