A new conjugated mesoporous polymer as fluorescence sensor for the detection of nerve agent simulant dimethyl chlorophosphonate via specific nucleophilic substitution reaction.

Conjugated micro/mesoporous polymers (CMPs) represent a category of porous organic materials formed via covalent bonds. Here, DAC-TFP CMP was synthesized using 3,6-diaminocarbazole (DAC) and 2-hydroxy-1,3,5-benzenetricarbaldehyde (TFP) as building blocks. DAC-TFP CMP is a porous conjugation polymer with remarkable thermal and chemical stability. DAC-TFP CMP suspension demonstrates selective "on-off" fluorescence response towards nerve agent simulant dimethyl chlorophosphonate (DMCP) in 1,4-dioxane with exceptionally low detection limits. DMCP and DAC-TFP CMP undergo a nucleophilic substitution reaction, leading to the formation of an N-P bond between N atom on carbazole of DAC-TFP CMP and P atom of DMCP. The new polymer DAC-TFP CMP@DMCP has electron donor-acceptor structure and the fluorescence quenching can be ascribed to the intramolecular charge transfer (ICT) from DAC-TFP CMP unit to DMCP group, as supported by XPS results and DFT calculation. Upon the addition of DMCP to the 1,4-dioxane suspension of DAC-TFP CMP, a subtle blue shift is observed in both the fluorescence emission spectra and UV-vis absorption spectra, providing further validation of the ICT mechanism. DAC-TFP CMP shows excellent recoveries in detecting DMCP in both soil and pesticide samples containing mesotrione and atrazine, highlighting its strong potential as a reliable chemosensor for DMCP detection and analysis.