Assembly of three new triphenylamine functionalized MOFs for the fluorescent sensing of nitrobenzene

The detection of nitrobenzene (NB) is very important because it has a series of irreversible effects on human health. Metal-organic frameworks (MOFs) show potential applications in this field due to their tunable and porous structures. In this work, three new MOFs, namely [Mn3(TCA)2(DMF)4]·DMF (JOU-28), [Cd21(TCA)14(H2O)9]·21DMF·21H2O (JOU-29), and [Cd3Cl3(TCA)(DMF)2]·H2O (JOU-30), were successfully prepared by solvothermal method (H3TCA = 4,4′,4″-tricarboxytriphenylamine; DMF = N,N′-Dimethylformamide). Single crystal X-ray diffractions showed that JOU-28 was a 3D porous supramolecular structure based on 2D coordination networks, while both JOU-29 and JOU-30 were 3D porous structures based on 1D chains. Due to its strong fluorescence emission, JOU-29 was selected as a representative to study the NB sensing performance. A linear relationship between the NB concentration and the fluorescence emission intensity of JOU-29 could be obtained as I0/I = 0.952 + 8089[NB]. This result showed that JOU-29 can be used for quantitative detection of NB. Further studies revealed that the fluorescence quenching of JOU-29 may be due to the fluorescence resonance transfer effect and the competitive absorption. This work provides clues for the design and synthesis of fluorescent MOFs for NB detection.