Design and synthesis of rare earth organic-inorganic hybrid material based on dawson type polyoxometallate {P2Mo18}

We report a rare earth organic-inorganic hybrid material based on dawson type polyoxometallate formulated as [Eu(DMA)7]·[Eu(DMA)4.5]·[P2Mo18O62]·26DMF (1), which was synthesized under solvothermal method by the interaction of a Keggin-type polyoxometalate H3PMo12O40 precursor with Eu(NO3)3·H2O in DMA solvent. Single crystal X-ray diffraction showed that 1 crystallizes in the monoclinic space group P21/n and an O atom of the polyacid anion P2Mo18O622− (abbreviated as {P2Mo18}) bonds to the rare earth Eu ion directly. This compound was further characterized by various analytical techniques such as powder X-ray diffraction (PXRD), IR spectra, thermogravimetric (TG) analyses, ultraviolet–visible spectroscopy (UV/vis), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and electrochemistry. Surprisingly, the resulting hybrid has extremely sharp photochromic properties which shows a significant change in color under ultraviolet–visible light illumination due to the reduction of the Mo6+ centers of the polyoxometalate to Mo5+. At the same time, the compound 1 has good electrocatalytic reduction properties for H2O2, NaNO2, and NaBrO3.