Removal of tetracycline hydrochloride from aqueous solution by three 3D uranyl-organic frameworks

Abstract

Nitroterephthalic acid (H2ntp), 2,5-dibromoterephthalic acid (H2bdc) and N,N′-donor ligands have been employed to synthesize three uranyl compounds: (H2-tmp)[(UO2)(ntp)2]·H2O (1), (2,2′-Hbpy)[(UO2)2(ntp)2.5]·H2O (2) and [(UO2)(bdc)(4,4′-bpy)0.5] (3) [where 2,2′-bpy = 2,2′-dipyridyl, 4,4′-bpy = 4,4′-dipyridyl, tmp = tetramethylpyrazine]. Single-crystal X-ray crystal structures of compounds 1–3 have been determined. Compounds 1 and 2 consist of dinuclear units, which are linked by ntp2− ligands on the equatorial plane to form 2D network, the layers are further bridged by the carboxylate at the angles of 118.69° (1) and 106.18° (2) in the axial position to form the 3D frameworks. In compound 3, each uranyl center is bridged by four bdc2− ligands to form a 3D framework with the carboxylate at the angle of 73.96° on the equatorial plane, and the 4,4′-bpy further consolidates the crystal structure. Compounds 1–3 have been characterized by IR, powder X-ray diffraction, UV-vis absorption spectroscopy, thermogravimetric analysis and photoluminescence spectroscopy. In addition, the photocatalytic degradation of 1, 3 and the performance for tetracycline hydrochloride adsorption of 2 have been investigated.