Highly Selective Detection of 2,4,6-Trinitrophenol and Cu2+ Ions Based on a Fluorescent Cadmium-Pamoate Metal-Organic Framework

A luminescent cadmium-pamoate metal-organic framework, [Cd-2(PAM)(2)(dpe)(2)(H2O)(2)]center dot 0.5(dpe) (1), has been synthesized under hydrothermal conditions by using pi-electron-rich ligands 4,4'-methylenebis(3-hydroxy-2-naphthalene-carboxylic acid) (H(2)PAM) and 1,2-di(4-pyridyl)ethylene (dpe). Its structure is composed of both mononuclear and dinuclear Cd-II building units, which are linked by the PAM and dpe ligands, resulting in a (4,8)-connected 3D framework. The pi-conjugated dpe guests are located in a 1D channel of 1. The strong emission of 1 could be quenched efficiently by trace amounts of 2,4,6-trinitrophenol (TNP), even in the presence of other competing analogues such as 4-nitrophenol, 2,6-dinitrotoluene, 2,4-dinitrotoluene, nitrobenzene, 1,3-dinitrobenzene, hydroquinone, dimethylbenzene, and bromobenzene. The high sensitivity and selectivity of the fluorescence response of 1 to TNP shows that this framework could be used as an excellent sensor for identifying and quantifying TNP. In the same manner, 1 also exhibits superior selectivity and sensitivity towards Cu2+ compared with other metal ions such as Zn2+, Mn2+, Mg2+, K+, Na+, Ni2+, Co2+, and Ca2+. This is the first MOF that can serve as a dual functional fluorescent sensor for selectively detecting trace amounts of TNP and Cu2+.