A novel organic-inorganic hybrid built upon both [VMo6O24]6- and [Mo7O24]6- units: Synthesis, crystal structure, surface photovoltage and electrocatalytic activities

Organic/Inorganic Species Synergistically Supported Unprecedented Vanadomolybdates

Vanadomolybdates (VMos), comprised of Mo and V in high valences with O bridges, are one of the most important types of polyoxometalates (POMs), which have high activity due to their strong capabilities of gaining/losing electrons. Compared with other POMs, the preparation of VMos is difficult due to their relatively low structural stability, especially those with unclassical architectures. To overcome this shortcoming, in this study, triol ligands were applied to synthesize VMos through a beaker reaction in the presence of V₂O₅, Na₂MoO₄, and organic species in the aqueous solution. The single-crystal X-ray diffraction results indicate that two VMo clusters, Na₄{V₅Mo₂O₁₉[CH₃C(CH₂O)₃]}∙13H₂O and Na₄{V₅Mo₂O₁₉[CH₃CH₂C(CH₂O)₃]}∙13H₂O, with a similar architecture, were synthesized, which were both stabilized by triol ligand and {MoO₆} polyhedron. Both clusters are composed of five V ions and one Mo ion in a classical Lindqvist arrangement with an additional Mo ion, showing an unprecedented hepta-nuclear VMo structure. The counter Na⁺ cations assemble into one-dimensional channels, which facilitates the transport of protons and was further confirmed by proton conductivity experiments. The present results provide a new strategy to prepare and stabilize VMos, which is applicable for developing other compounds, especially those with untraditional architectures.