A series of uranium-organic frameworks: Crucial role of the protonation ability of auxiliary ligands

Abstract

Three new Uranium-organic compounds have been synthesized under thestrongacidcondition. Both of the compound 1 [(UO2)(TMA)](H2BPY)0.5·4H2O (TMA = trimesic acid, BPY = 4,4′-bipyridine, CCDC 1841538) and 2 [(UO2)(PMA)0.5](H2BPY)0.5 (PMA = pyromellitic acid, CCDC 1870479) show a “sandwich” 2D-structure. The double-protonated 4,4′-dipyridines stabilize the supramolecular structure without obvious interlayer interactions in 1, while there is weak NH⋯O hydrogen bonding in 2. Compound 3 [(UO2)2(PTA)(BPDO)] (PTA = terephthalic acid, CCDC1841602) was obtained by employing 4,4′-bipyridine-N-dioxide (BPDO) as auxiliary ligand. Owing to the much weaker protonation ability, the BPDO molecules can pillar the screwy uranyl layers via U-O covalent bonds to form a 3D framework. All the title compounds are well-characterized. The results indicate the intensity of the interaction between uranyl layer and the auxiliary ligand not only affect the assembly of the architecture, but also the fluorescent and adsorption behavior.