Channel regulation for four Cd-MOFs with phenylimidazole dicarboxylic acid: Synthesis, crystal structure and solid fluorescence properties

Abstract

Four new cadmium(II) organic frameworks (Cd-MOFs) containing phenylimidazole dicarboxylic acid ligands, [Cd4(HPhIDC)4(H2O)2]n (1), [Cd2(p-HMOPhIDC)2(NH3)(H2O)]n (2), {Na2[Cd2(p-MOPhIDC)2(4,4′-Bpy)]}n (3) and [Cd4(m-HMOPhIDC)4(4,4′-Bpy)4]n (4) (H3PhIDC = 2-phenyl-1H-imidazole-4,5-dicarboxylic acid, p-H3MOPhIDC = 2-(4-Methoxyphenyl)-1H-imidazole-4,5-dicarboxylic acid, m-H3MOPhIDC = 2-(3-Methoxyphenyl)-1H-imidazole-4,5-dicarboxylic acid, 4,4′-Bpy = 4,4′-bipyridine), have been synthesized by hydrothermal method and characterized. Channels in four Cd-MOFs show high structural diversity. The channel of 1 is a quadrilateral channel containing six Cd(II) ions, the channel of 2 is a double channel containing ten Cd(II) ions in a staggered arrangement of large and small quadrilaterals, the channel of 3 is a rectangular channel containing eight Cd(II) ions and the channel of 4 is an arched channel containing eight Cd(II) ions. The results show that the coordination mode of phenylimidazole dicarboxylic acid ligands and the auxiliary N-containing linkers have a crucial impact on the channel structural diversities of three-dimensional Cd-MOFs. Further, the fluorescence properties of Cd-MOFs 1–4 at room temperature in solid state were studied.