A series of polyoxometalate compounds by tuning N sites and numbers of ligands: syntheses, characterization and electrochemical sensing, and photocatalytic and supercapacitor properties?

New Journal of Chemistry Pub Date: 2022-04-02 DOI: 10.1039/D2NJ00674J

Abstract

By using different morpholine derivatives with different N sites and numbers, we have synthesized seven compounds by a hydrothermal method, namely [AgI2(HL1)][Cr(OH)6Mo6O18]·H2O (1), [AgI(H2L)][Cr(OH)6Mo6O18]·4H2O (2), [CoII(HL1)2(H2O)][Cr(OH)6Mo6O18]2·2H2O (3), [NiII(HL2)(H2O)][Cr(OH)6Mo6O18]·4.5H2O (4), [CoII(HL2)(H2O)][Cr(OH)6Mo6O18]·4.5H2O (5), [AgI(HL1)][(δ-Mo8O26)0.5]·2H2O (6) and [CoII(HL3)2(H2O)2](β-Mo8O26) (7) (L = 4-(2-aminoethyl)-morpholine, L1 = 4-[2-(5-pyridin-4-yl-[1,2,4]triazol-1-yl)-ethyl]-morpholine, L2 = 4-[2-(5-pyridin-2-yl-[1,2,4]triazol-1-yl)-ethyl]-morpholine, L3 = 4-[2-(5-pyrazin-2-yl-[1,2,4]triazol-1-yl)-ethyl]-morpholine, L = 4-[2-(dimethylamino)ethyl]morpholine). These compounds were characterized by single crystal X-ray diffraction, FT-IR and PXRD. Compound 1 exhibits a 3D framework constructed by 1D chains. Compounds 2 and 4–6 all show 2D structures, in which the 2D layer of 2 is only built by POM and transition metals (TMs). But in 4–6 both the POM and metal–organic subunits construct the layer structures. Compounds 3 and 6 are 1D structures, containing a POM-linked chain in 3 and only a metal–organic chain in 6. Compounds 1–7 can be used as bifunctional electrochemical sensors. They can detect not only NO2? anions, but also Cr(VI) and Fe(III) cations. For example, the response time of 1-CPE for Cr(VI) was 2.16 s and the detection limit was 4.3 × 10?3 M. Compound 4 also has certain capacitance performance. In addition, compounds 1–7 can be used as catalysts for the photodegradation of organic dyes and the reduction of Cr(VI).

Graphical abstract: A series of polyoxometalate compounds by tuning N sites and numbers of ligands: syntheses, characterization and electrochemical sensing, and photocatalytic and supercapacitor properties
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