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

Abstract

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 O₂²⁻. The active oxygen species (O₂²⁻, 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.

Keywords:

• Polyoxometalate
• Lanthanide polymer
• MOF
• Photocatalysis
• Desulfurization

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Corrigendum

Supplementary material

Crystallographic data for 1–5 have been deposited with the Cambridge Crystallographic Data Center, CCDC numbers 913822, 913823, 913824, 913825, and 913826, respectively. These data are available free of charge from The Cambridge Crystallographic Data Center via the Internet at www.ccdc.cam.ac.uk/data_request/cif.

Acknowledgments

This work is financially supported by the National Science Foundation of China (No. 20773057) and the National Key Basic Research and Development Program (No. 2009CB220010).