Novel Covalent Bonds and Hydrogen Bonds Linked Porous Organic Frameworks as Chemosensor for Detecting 2,4,6-Trinitrophenol in Water and Soil Samples

A novel and unconventional structural porous organic framework combined through the synergistic effect of covalent bonds and hydrogen bonds was prepared with the combination of 4,4′,4″,4‴-(pyrene-1,3,6,8-tetrayl)tetraaniline (Py) and 5-hydroxyisophthalaldehyde (HP). It was the second example of CHOF until now and had been designated as Py–HP CHOF. The suspension of Py–HP CHOF in various solvents, such as ethanol, CH3CN, and methanol, exhibited a remarkably selective and sensitive "on–off" fluorescence response toward 2,4,6-trinitrophenol (TNP) compared with other explosives, with exceptionally low detection limits. The X-ray diffraction (XRD) spectra confirmed that the framework of Py–HP CHOF collapsed after interaction with TNP and acid, further indicating the existence of hydrogen bonds in the framework of Py–HP CHOF. The fluorescence quenching can be ascribed to the photoinduced electron transfer and the absorption competition quenching, as supported by XRD, X-ray photoelectron spectroscopy results, UV–vis absorption spectra, and density functional theory calculations. Fluorescence channels can be utilized by Py–HP CHOF to function as chemosensor, enabling the identification and detection of TNP in water and soil, and Py–HP CHOF is also the second CHOF example of sensing TNP reported to date. The application of this technique exhibits considerable potential in the analysis and detection of environmental pollutants, thereby presenting substantial practical implications.