Lanthanide metal organic frameworks based on dicarboxyl-functionalized arylhydrazone of barbituric acid: syntheses, structures, luminescence and catalytic cyanosilylation of aldehydes

Abstract

Five isostructural lanthanide MOFs, [Ln(1κOO′,2κO′′,3κO′′′,4κO′′′′-μ₄-L)(NO₃)(DMF)₂]_n·n(DMF) {Ln = La³⁺ (1), Ce³⁺ (2), Nd³⁺ (3), Sm³⁺ (4) and Dy³⁺ (5); L = 5-[2-{2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene}hydrazinyl]isophthalate; DMF = N,N′-dimethyl formamide}, based on dicarboxyl-functionalized arylhydrazone of barbituric acid were synthesized under solvothermal conditions. They were characterized by elemental analysis, FT-IR spectroscopy, thermogravimetric and X-ray diffraction analyses. Crystal structure analysis revealed that these frameworks possess a similar type of two dimensional (2D) structure with a dinuclear {Ln₂(COO⁻)₂} unit acting as a secondary building block. Topological analysis shows that these frameworks display a 3,6-connected kgd; Shubnikov plane (3.6.3.6)/dual net. They exhibit excellent heterogeneous catalytic activities (compound 2 is the most active one) towards the cyanosilylation of aldehydes under solvent-free conditions. These catalysts can be recycled at least up to five cycles without a loss of activity. Compounds 1–5 exhibit luminescence properties in the solid state at room temperature.