Hydrothermal syntheses and crystal structures of crystalline catalysts based on 3-D Ln3+-pdc2- frameworks and [BW12O40]5- and their heterogeneous photocatalytic oxidation of thiophene

Five [BW12O40](5-)-containing metal-organic frameworks (MOFs), {K[Ln(H2O)(4)(pdc)](4)}[BW12O40]center dot 2H(2)O (Ln=La 1 and Ce 2, H(2)pdc = pyridine-2,6-dicarboxylate) and {K[Ln(H2O)(3)(pdc)](4)}[BW12O40]center dot 6H(2)O (Ln=Tb 3, Dy 4 and Er 5), are synthesized hydrothermally. Ln(3+) and pdc(2-) are built into 3-D MOF segments containing large channels and cavities which are occupied by [BW12O40](5). Herein, we report MOF-containing polyoxometalates (POMs) as photocatalysts to oxidize thiophene with O-2 as the oxidant. Photo-excited state species ([BW12O40](5-)) are generated under UV irradiation and then H2O is oxidized into OH radicals and O-2 is reduced into O-2(2-). The active oxygen species (O-2(2-), OH) oxidize thiophene in the presence of photocatalysts and SO3, CO2, and H2O are obtained as photoproducts. ESR measurements provide evidence that OH species are generated during photocatalysis.