Ce(III) and Lu(III) metal–organic frameworks with Lewis acid metal sites: Preparation, sorption properties and catalytic activity in Knoevenagel condensation

• New metal–organic frameworks containing Ce(III) (1) and Lu(III) (2) ions are studied.
• Both frameworks contain structural channels filled with DMF and water molecules.
• Channels in 1 collapse after removal of solvents, while 2 exhibits open porosity.
• Framework of 2 displays very high thermal stability (500 °C in air, 620 °C in Ar).
• Compound 2 is capable of gas adsorption and catalysis in Knoevenagel condensation.

Two novel coordination polymers with composition {[Ln(BTC)(H2O)]·DMF}n (where Ln = Ce(III) (1) and Lu(III) (2), BTC = benzene-1,3,5-tricarboxylate, DMF = N,N′-dimethylformamide) have been prepared under solvothermal conditions. Properties of the compounds were investigated by single crystal X-ray diffraction, high-energy powder X-ray diffraction during in-situ heating, thermogravimetry with simultaneous evolved gas analysis, infrared spectroscopy performed at different temperatures, elemental analysis and inductively coupled plasma mass spectrometry. Sorption properties of the synthesized complexes were investigated using nitrogen and carbon dioxide adsorption experiments. Catalytic activity of compound 2 was tested in Knoevenagel condensation reactions in a series of aromatic and non-aromatic aldehydes with different active methylene compounds (malononitrile, methyl cyanoacetate), in which the reactivity of aldehydes in condensation reactions increases in the order: 2-naphthaldehyde < 4-tert-butyl benzaldehyde < benzaldehyde < cyclohexane carbaldehyde < n-heptanal.

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