Lanthanide metal–organic frameworks with 2,2′-bipyridine-polycarboxylic acid: Synthesis, crystal structures and fluorescent properties

•Five crystallographic independent Eu ions in 1–3 have two coordination environments.•Complex 4 shows 3-D framework structure and considerable thermal stability.•H4bptc was decarboxylated to transform into bptc′3− ion in presence of Cu2+ ions.

Four lanthanide metal–organic frameworks, namely, [{[Ln5(bptc)3(Hbptc)(H2O)12]·4H2O}n (Ln = Eu, 1; Gd, 2; Tb, 3) and {[Eu(bptc′)]}n (4), (H4bptc = 2,2′-bipyridine-3,3′,6,6′-tetracarboxylic acid, H3bptc′ = 2,2′-bipyridine-3,6,6′-tricarboxylic acid) have been hydrothermally synthesized. Compounds 1–4 were structurally characterized by IR spectra, thermogravimetric analyses and single-crystal X-ray diffractions. Complexes 1–3 are the isostructural 2D layered structures, five crystallographic independent Eu(III) ions display the two different kinds of coordination environments. Complex 4 exhibits a 3D framework structure, while H4bptc was decarboxylated to transform into the tricarboxylate group of bptc′3− in the presence of Cu2+ ions under the hydrothermal conditions. The solid state fluorescent properties of 1, 3 and 4 were investigated at room temperature, respectively.

Graphical abstractFour lanthanide metal–organic frameworks based on 2,2′-bipyridine-polycarboxylic acid ligands exhibit the three isostructural 2D layered structures and a 3D framework structure. The solid state fluorescent properties of 1, 3 and 4 were investigated, respectively.Figure optionsDownload full-size imageDownload as PowerPoint slide