A Systematic Study of Fluorescence‐Based Detection of Nitroexplosives and Other Aromatics in the Vapor Phase by Microporous Metal–Organic Frameworks

Abstract

A systematic study is conducted on four microporous metal–organic framework compounds built on similar ligands but different structures, namely [Zn3(bpdc)3(bpy)]⋅4 DMF⋅H2O (1), [Zn3(bpdc)3(2,2′dmbpy)]⋅4 DMF⋅ H2O (2), [Zn2(bpdc)2(bpe)]⋅2 DMF (3), and [Zn(bpdc)(bpe)]⋅DMF (4) (bpdc=4,4′‐biphenyldicarboxylate; bpy=4,4′‐bipyridine; 2,2′dmbpy=2,2′‐dimethyl‐4,4′bipyridine; bpe=1,2‐bis(4‐pyridyl)ethane; DMF=N,N′‐dimethylformamide) to investigate their photoluminescence properties and sensing/detection behavior upon exposure to vapors of various aromatic molecules (analytes) including nitroaromatic explosives. The results show that all four compounds are capable of detecting these molecules in the vapor phase through fluorescence quenching or enhancement. Both electrochemical measurements and theoretical calculations are performed to analyze the analyte–MOF interactions, to explain the difference in signal response by different analytes, and to understand the mechanism of fluorescence quenching or enhancement observed in these systems. Interestingly, compound 3 also shows an emission frequency shift when exposed to benzene (BZ), chlorobenzene (ClBZ), and toluene (TO), which provides an additional variable for the identification of different analytes in the same category.

A porous metal–organic framework formed by a V-shaped ligand and Zn(ii) ion with highly selective sensing for nitroaromatic explosives

“…The fluorescence quenching phenomenon should be mainly due to electron transfer from the framework to electron-deficient NB molecule. [58,59] The absorption band of TNP has a 20 considerable degree of overlap with the emission spectrum of JUC-135 in DMF (Fig. So we 60 further investigated the fluorescent property of JUC-135 to detect a series of nitroaromatic explosives, including 1, 3-DNB, 2, 4-DNT and TNP.…”

Nanocomposite of europium organic framework and quantum dots for highly sensitive chemosensing of trinitrotoluene

“…MOFs with metal centers of europium, cadmium, zinc, lithium, iridium have been recently reported for the detection of nitro-aromatic explosives [22][23][24][25][26]. However, some of our tests on the nitro aromatic explosive sensing with MOFs revealed that, at times, it is difficult to obtain reproducible results in different sets of experiments.…”

Fluorescence Detection of Anilines and Photocatalytic Degradation of Rhodamine B by a Multifunctional Metal–Organic Framework

“…In general, the electron transfer from the conduction band (CB) of the MOFs in the excited state to the low-lying lowest unoccupied molecular orbital (LUMO) of the analytes will result in a fluorescence quenching effect. [31,32] The fact that p-nitroaniline exhibits the strongest quenching effect may be attributed to the strongly electron-withdrawing NO 2 group. In contrast, if the excited electrons are transferred from a high-lying π* type LUMO orbital to the conduction band of MOF1, fluorescence enhancement will result.…”