Highly Fluorescent Polyimide Covalent Organic Nanosheets as Sensing Probes for the Detection of 2,4,6-Trinitrophenol

Abstract

A new fluorescent polyimide covalent organic framework (PI-COF) has been successfully synthesized through solvothermal route using tetra(4-aminophenyl) porphyrin and perylenetracarboxylic dianhydride, which possesses porous crystalline and excellent thermal stability (>500 °C). Furthermore, few-layered PI covalent organic nanosheets (PI-CONs) can be easily obtained from the fluorescent PI-COF through a facile liquid phase exfoliation approach, which were confirmed by atomic force microscopy and transmission electron microscopy analysis. It is interesting that the fluorescent intensity of PI-CONs is obviously enhanced relative to that of PI-COF. The PI-CONs have been successfully utilized as an efficient fluorescent probe for the highly sensitive and selective detection of 2,4,6-trinitrophenol (TNP). The mechanism might be attributed to the combination of electron transfer and inner filter effect based on DFT calculations and spectral overlap data. The system exhibits a good linear response toward TNP over the range from 0.5 to 10 μM with a detection limit of 0.25 μM.

Table-salt enabled interface-confined synthesis of covalent organic framework (COF) nanosheets

“…11,17,18 CONs with a few nanometers in thickness not only offer more active sites, but also improve mass transfer efficiency. These features signicantly promote the performances of the devices assembled from CONs for applications such as sensing, 19,20 ion conductivity, 11 and separation. 15,21 Unfortunately, turning these polymeric crystalline networks into thin nanosheets with a high yield remains a great challenge due to the strong p-p stacking interaction between adjacent COF monolayers.…”

The effects of the crosslinking position and degree of conjugation in perylene tetraanhydride bisimide microporous polymers on fluorescence sensing performance

“…Hence, although the LUMO energies of DP 4 A 0 and DP 4 A 2 are lower than that of NB, DNT, p-NT, m-DNB, o-NP, and PhOH, a PET process can occur as well. 34,49 Generally speaking, nitro groups play an important part in uorescence quenching because their contribution to the LUMO energies is achieved by utilizing their electron withdrawing ability. Therefore, with increasing numbers of nitro groups, lower LUMO energy levels are obtained, thus improving electron transfer efficiency.…”

Porous Organic Frameworks: Advanced Materials in Analytical Chemistry

“…The theoretical calculations further indicated that the electrons of ground‐state transfer from the highest occupied molecular orbital (HOMO) of TNP − to the LUMO of protonated TfpBDH‐CONs, resulting in the observation of the fluorescence quenching. Zhang et al also fabricated thin‐layered fluorescent polyimide‐based CONs (PI‐CONs) from a solvothermal‐synthesized COFs through a ultrasonic‐assisted exfoliation method. The PI‐CONs were subsequently used for the fluorescent detection of TNP, demonstrating an excellent chemosensing ability for TNP, based on fluorescence quenching.…”