A water-stable Eu^III-based MOF as a dual-emission luminescent sensor for discriminative detection of nitroaromatic pollutants

Abstract

A water-stable Eu^III-based metal-organic framework (MOF) with dual-emission luminescence behavior, namely {[Eu₄(INO)₅(μ₃-OH)₂Cl₄(H₂O)]·(NO₃)·(H₂O)₅}_n (Eu-MOF; HINO = isonicotinic acid N-oxide), was successfully constructed by the solvothermal reaction of Eu³⁺ ions with the organic ligand HINO. The cationic 3D framework contains microporous channels with accessible Lewis-base sites and NO₃^- ions as balanced anions, which all contribute to the selective detection of multifarious analytes. This MOF shows ratiometric detection of acetone, Cr₂O₇^2- ions, and nitroaromatic compounds (NACs). In particular, it shows great recognition of four NACs in water, representing the first Ln^III-MOF which can display distinguishing fluorescence phenomena on NACs rather than relying on the quenching effect. Furthermore, this is also the first example of a MOF-sensor for detecting these explosives discriminatively by ratiometric methods. Additionally, the mechanisms for luminescent responses towards different analytes have been discussed in detail.