Solvothermal Assembly of a Series of Organic-Inorganic Hybrid Materials Constructed from Keggin Polyoxometalate Clusters and Copper(I)-Organic Frameworks

Seven polyoxometalate (POM) hybrid materials based on Keggin polyanion building blocks and copper(I) -organic frameworks with pyrazine derivatives, namely, [Cu-4(I)(2Et,3Me-Pyr)(5)(SiW12O40)] (1), [Cu-4(I)(2,6-Pyr)(4)(SIW12O4O)] (2), [Cu-4(I)(2,5-Pyr)(4)(SiW12O40))(H2O)(2)] (3), [Cu-4(I)(2,3,5,6-Pyr)(4)(SiW12O4)](H2O) (4), [Cu-4(I)(2,5-Pyr)4(PMovii IMovaso)]center dot 1.5H(2)O (5), [Cu-3(I)(2,3,5-PYO4(PMOH2O4O)]center dot H2O (6), and '[Cu-4(I)(2Et,3Me-Pyr)(5)(PMoVI (11MoO40)-O-V)] (7); where 2Et,3Me-Pyr = 2-ethy1-3-methylpyrazine, 2,6-Pyr = 2,6-dirnethylpyrazine, 2,5-Pyr = 2,5-diinethylpyrazine, 2,3,5-Pyr = 2,3,5-trirnethylpyrazine, and 2,3,5,6-Pyr = 2,3,5,6tetramethylpyrazine, have been synthesized under solvothermal conditions. In 1 and 7, polyanions link Cu-I-organic sheets to generate 3D (3,4)-connected frameworks. In 2, the polyanion bridges Cu-I-organic chains to field a 3D (3,4,6)-connected framework. Both 3 and 4 exhibit 2D double layer structures. In 5, the Keggin polyaition bridges the Cu-I-Pyr chains to form an infinite 3D (3,4)-connected framework. In 6, Cu-I cations are bridged by the 2,3,5-Pyr and Keggin polyanions to generate a novel 2D (8,3) sheet. The roles of the pyrazine derivatives and the Keggin polyanions in the formation of the POM-based MOFs have been discussed.