A unique terbium-fluoride-oxalate metal–organic framework containing [Tb-F]n chains with bifunctions of luminescent detection of Cr(VI) and catalyzing CO2 conversion to cyclic carbonates

Abstract

The low cost, including material cost and energy cost, in large-scale production is an important metric for a metal–organic framework (MOF) towards real-world applications. This requires that the MOF can be efficiently synthesized in a high yield under mild enough conditions, while the employed organic ligands should be simple in structure and cheap. Motivated by such consideration, we established our work on a Tb-fluoride-oxalate framework [TbF(C2O4)(H2O)2]n∙2nH2O (1), which meets the requirements stated above. The synthesis of its single-crystal sample and its crystal structure are first reported here. X-ray diffraction test shows 1 has a 3D microporous framework structure constructed by 1D [Tb-F]n chains and C2O42− bridges. In fact, 1 is the unique complex that comprises [Tb-F]n chains. Though [Tb-F]n chain is of great interest in the field of molecular nanomagnets, direct-current and alternating-current magnetic susceptibilities reveal no slow magnetic relaxation behavior in 1. Luminescence investigation reveals that 1 exhibits strong green photoluminescence emission and can be used as a “turn-off” luminescent sensor for toxic Cr2O72− and CrO42− ions in aqueous solution with high selectivity and sensitivity. Besides, the strong Lewis acidity of Tb3+ also makes 1 a good heterogeneous catalyst for the cycloaddition reaction of CO2 with epoxides to cyclic carbonates.