A luminescent Zn-MOF constructed from l-aspartic acid and 4,4-bipyridine: Selectively and sensitively detect Fe3+ and 2,4,6-trinitrophenol (TNP) in aqueous solution

A water-stable luminescent Zn-MOF [Zn2(IDS)(bipy)1.5] (complex 1) (H4IDS ​= ​meso-iminodisuccinic acid, bipy ​= ​4,4’-bipyridine) was successfully synthesised by hydrothermal method through in-situ formation of a meso-iminodisuccinic acid ligand from two l-aspartic acid precursors. Complex 1 presents a structure with crs architecture and a topological point symbol of {36.66.73}. It is found that complex 1 can selectively and sensitively detect Fe3+ and 2,4,6-trinitrophenol (TNP) by luminescence quenching in aqueous solution. The quenching constant (Ksv) for Fe3+ is 1.39 ​× ​104 ​M−1 with the detection limit (LOD) of 3.93 ​× ​10−5 ​M; and the Ksv for TNP is 2.6 ​× ​104 ​M−1 with the LOD of 6.47 ​× ​10−5 ​M. In particular, as the concentration of TNP increases, the red shift (about 23 ​nm) of emission spectra can also be obviously monitored. The mechanism of complex 1 to Fe3+ is due to inner filtration effect (IFE) and the interaction with uncoordinated oxygen atoms of the framework, while to TNP is because of IFE and fluorescence resonance energy transfer (FRET).