Two new Wells–Dawson polyoxometalate-based organic-inorganic hybrid materials, namely, {[O]2.75[trz]7[α2-P2W17VO62]•12H2O}2(1) and {[O]11.5[trz]7[α2-P2W14.4V3.6O62]}2(2) (trz=1-H-1,2,4-triazole) were synthesized under mildconditions, and characterized by FT-IR, 1H NMR and 31P NMR spectroscopy, powder X-ray diffraction, TGA, field emission SEM and cyclic voltammetry. These hybrids constructed from trz ligand and Wells–Dawson polyoxoanions, in which trzis connected to a mono-vanadium substituted [α2-P2W17VO62]7− in 1 and a hexa-vanadium substituted [P2W12V6O62]12−in 2 by hydrogen bonding interactions. The structures of 1 and 2 were determined by single-crystal X-ray diffraction. Electrocatalytical activities of compounds 1 and 2 in the form of modified carbon paste electrode (MCPE) towards the reduction of nitrite ion have been studied in different pH values at acidic buffer solutions. Compounds 1-MCPE and 2-MCPE exhibit good electrocatalytical activity for reduction of NO2−. Also, the photocatalytical properties of the compounds 1 and 2 for the degradation of methylene blue have been studied.

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