A luminescent metal–organic framework with tetragonal nanochannels as an efficient chemosensor for nitroaromatic explosives detection

Abstract

A novel 3D MOF [(Zn₄O)(H₂O)₂(TPA)₂]·8DMA (1) (H₃TPA = 4,4′,4′′-nitrilotrisbenzoic acid; DMA = N,N-dimethylacetamide) with tetragonal nanochannels has been rationally obtained under solvothermal conditions using the fluorescent ligand H₃TPA. MOF 1 demonstrates a unique (3,6)-connected network with nanosized square channels, displaying strong blue emission. Interestingly, 1 can be used as a fluorescent probe, which can detect nitroaromatic explosives efficiently and selectively via fluorescence quenching phenomena. As the number of –NO₂ groups increase, fluorescence quenching becomes more obvious, which is maybe because the energy transfer from the electron-donating framework to electron-withdrawing nitroaromatic analytes becomes greater. Notably, the sensor is particularly sensitive to picric acid (PA), showing complete fluorescence quenching at a PA concentration as low as 30 ppm. MOF 1 can be recycled in the detection of nitroaromatic explosives with excellent recyclability. Additionally, the photo-induced electron transfer mechanism was validated through theoretical calculations for the fluorescence quenching.