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

Highlights: • A water-stable luminescent Zn-MOF was successfully synthesised by hydrothermal method and structurally characterized. • A meso-iminodisuccinic acid ligand was converted from two L-aspartic acid precursor byin-situreaction. • The Zn-MOF can selectively and sensitively detect Fe³⁺and TNP by luminescence quenching in aqueous solution. • As the concentration of TNP increases, the red shift (about 23nm) of emission spectra can also be obviously monitored. 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 (K_sv) for Fe³⁺ is 1.39×10⁴M⁻¹ with the detection limit (LOD) of 3.93×10⁻⁵M; and the K_sv for TNP is 2.6×10⁴M⁻¹ with the LOD of 6.47×10⁻⁵M. In particular, as the concentration of TNP increases, the red shift (about 23nm) 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).