A series of microporous and robust Ln-MOFs showing luminescence properties and catalytic performances towards Knoevenagel reactions

Abstract

A series of microporous Ln(III)-based metal–organic frameworks (1-Ln) have been hydrothermally synthesized using 4,4′,4′′-nitrilotribenzoic acid (H₃NTB). Single crystal X-ray diffraction analyses show that 1-Ln are isostructural and have 3D porous frameworks with remarkable stability and permanent porosity for Ar and CO₂ adsorption. In addition, 1-Ln exhibit diverse photoluminescence emissions depending on the nature of lanthanide ions. More importantly, 1-Ln are further studied in the Knoevenagel reactions of benzaldehyde derivatives and malononitrile under solvent-free conditions, and it is found that 1-Tb shows the best catalytic activities (yields up to 99%), providing a unique example to differentiate the roles of Ln ions within the frameworks in catalyzing Knoevenagel reactions.