Two new polyoxometalate-based metal-organic complexes for the detection of trace Cr(VI) and their capacitor performance.

Two new Keggin-type polyoxometalate (POM)-based metal-organic complexes (MOCs) H3[Cu2(4-dpye)2(PMo12O40)] (1) and H[Cu2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2O (2) were constructed with a new N,N'-bis (4-pyrimidinecarboxamido)-1,2-ethane (4-H2dpye) ligand by the hydrothermal/solvothermal method. Complex 1 was a 2D layered structure constructed from 1D metal-organic chains [Cu(4-dpye)]n and Keggin-type [PMo12O40]3- polyoxoanions. Complex 2 displays a 3D supramolecular framework formed by discrete [PMo12O40]3- polyoxoanions and binuclear metal-organic loops [Cu2(4-Hdpye)2]. The electrocatalytic behaviors of carbon paste electrodes modified by complexes 1 and 2 (1-CPE and 2-CPE) were investigated. The 1-CPE and 2-CPE were used as electrochemical sensors to detect trace Cr(vi), and the low limits of detection (LOD) are 1.27 × 10-7 M for 1 and 1.71 × 10-7 M for 2, which are lower than the maximum allowable concentration of Cr(vi) in drinking water specified by the World Health Organization (WHO). In addition, the performances of complexes 1 and 2 modified carbon cloth electrodes (1-CC and 2-CC) as supercapacitor materials have also been studied. The influence of the structure on electrocatalytic and capacitor performances is discussed.