Fluorescent sensing response of metal-organic frameworks for the highly sensitive detection of Hg2+ and nitrobenzene in aqueous media

Abstract A novel 3D coordination polymer [Pb2(2-NCP)2(L1)]n (1) (2-HNCP = 2-(2-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline, H2L1 = 2-amino-1,4-benzenedicarboxylic acid) has been synthesized under hydrothermal conditions. The structure has been determined by single crystal X-ray diffraction analyses and further characterized by elemental analyses and infrared spectroscopy. Structural analyses revealed that the complex exhibit three-dimensional network structure with a Schlafli symbol of 412·63 topologies. The thermal stabilities and gas adsorption properties of complex 1 was studied. The experimental results show that complex 1 has good thermal stabilities and selective adsorption properties for CO2. In addition, the solid state luminescent properties of MOFs were studied under the irradiation of ultraviolet light at ambient temperature, the peak type of complex 1 is similar to that of ligands, which belongs to intra ligand fluorescence emission. The luminescent quenching tests indicate complex 1 showing a high selectivity and sensitivity for Hg2+ ions and nitrobenzene because of the quenching effect, which thus could make it be potential crystalline materials for detecting these substances. Furthermore, in the detection process, 1 can be simply and quickly regenerated and reused at least five times. There are also discussions of the mechanism of quenching effect and sensing properties of complex 1 in detail.