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]·2H2O (Ln=La 1 and Ce 2, H2pdc = pyridine-2,6-dicarboxylate) and {K[Ln(H2O)3(pdc)]4}[BW12O40]·6H2O (Ln=Tb 3, Dy 4 and Er 5), are synthesized hydrothermally. Ln3+ and pdc2− 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 O2 as the oxidant. Photo-excited state species ([BW12O40]5−∗) are generated under UV irradiation and then H2O is oxidized into OH˙ radicals and O2 is reduced into O2 2−. The active oxygen species (O2 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.