New porous organic framework Py-PDA CHOF as fluorescent chemosensor for detecting 2,4,6-trinitrophenol in environmental samples

Abstract

Covalent bonds and hydrogen bonds linked porous organic frameworks (CHOFs) as a new type of porous organic framework connected by both covalent bonds and hydrogen bonds has been reported recently. Py-PDA CHOF was synthesized using 4,4′,4′’,4′’’-(pyrene-1,3,6,8-tetrayl)tetraaniline (Py) and 2,6-pyridinedicarboxaldehyde (PDA) as building blocks. It has porous crystalline framework and exceptional thermal stability. The suspension of Py-PDA CHOF in ethanol exhibits a highly selective and sensitive “on-off” fluorescence response towards 2,4,6-trinitrophenol (TNP), with exceptionally low detection limits. The powder X-ray diffraction (PXRD) confirmed the collapse of the Py-PDA CHOF after interaction with TNP and acid, and this result further indicated the presence of hydrogen bonds within the framework. The absorption competition quenching (ACQ) and photoinduced electron transfer (PET) mechanism are responsible for fluorescence quenching of Py-PDA CHOF by TNP. As a fluorescent chemosensor capable of detecting explosives, Py-PDA CHOF holds potential application for the identification and detection of TNP in water and soil samples.