Nonclassical Phosphomolybdates with Different Degrees of Reduction: Syntheses and Structural and Photo/Electrocatalytic Properties

Four nonclassical phosphomolybdates, formulated as (H2pytty)8[{Mn­(H2pytty)­(H2O)3}­{Sr⊂P6Mo6V Mo12VIO73}]2·16H2O (1), [{Mn­(H3pytty)­(H2O)3}2­{Sr⊂P6Mo4VMo14VIO73}]·18H2O (2), (H3pytp) (H2pytty)2[{Fe­(H2O)4}­{Sr⊂P6Mo3VMo15VIO73}]·5H2O (3), and (H2pytty)2[{Cd­(H2O)4}­{Cd­(H2O)3 (H3pytty)}­{Sr⊂P6Mo5VMo13VIO73}]·9H2O (4) (pytty = 3-(pyrazin-2-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl; pytp = 4′-(4″-pyridyl)-2,4′:6′,4″-terpyridine) were hydrothermally synthesized and fully characterized. The penta- and hexa-reduced basket clusters represent the highest reduced level of basket-based polyoxometalate so far. In addition, transition metal complexes as bridge units were introduced to basket system for the first time to induce rare two-dimensional inorganic–organic hybrid layer. The results indicate that reduced degrees of the basket clusters of compounds 1–4 can be tuned by altering the molar ratio of organic ligand pytty and Na2MoO4. Compounds 1–4 exhibit bifunctional electrocatalytic behaviors for oxidation of dopamine and reduction of H2O2. Electrocatalytic mechanism, chronoamperometric experiments and electrocatalytic stability are studied in detail. In addition, the compounds show highly efficient catalytic ability for the degradation of typical dyes under UV irradiation.