A sensitive and selective fluorescent probe for nitrobenzene based on Europium(III) post-functionalized Al(III)-based MOF

Abstract

A post-functionalized Eu 3+ @MIL-121 MOF was prepared through a facile hydrothermal approach and developed as a highly selective luminescent probe for detecting NB in aqueous solution. • A new MOF Eu 3+ @MIL-121 is designed and prepared. • A novel fluorescent strategy is proposed to specifically identify nitrobenzene in nitro-aromatic interferents in aqueous solution. • A new MOF fluorescent probe with the lower LOD for nitrobenzene compared to previous literature. Nitrobenzene (NB) is a substance with potential and possible hazards, which is widely used in industry field. In the current study, Europium(III) post-functionalized Al(III)-based metal–organic framework (Eu 3+ @MIL-121) was synthesized and utilized as an independently luminescent probe for the purpose of sensing NB. The red luminescence of Eu(III) could be quenched by NB through a process called fluorescence resonance energy transfer (FRET), and thus it could be used as a fluorescence off switch for NB, leading to its recognition. Eu 3+ @MIL-121 has its advantages of high sensitivity, selectivity, fast response time and wide response window. Compared with other MOFs, Eu 3+ @MIL-121 can specifically detect NB in aqueous solution, avoid secondary contamination by organic solvents, and has excellent linear range and LOD (limit of detection). Under the optimal conditions, the newly constructed Eu 3+ @MIL-121 fluorescent probe showed a satisfactory linear detection range of 0.005 to 20.000 μM, with a detection limit of 1.56 nM. Furthermore, the probe has been successfully applied to detect NB in real water samples.