Preparation of the Conjugated Hypercrosslinked Polymers Containing Phenylenediamine and Phenylenetriamine Derivatives for Fluorescent Sensing of Three Nitrophenols

Hypercrosslinked polymers (HCPs) are the most promising porous organic polymers for large-scale production due to their easy preparation, extensive raw material source, good stability, and large specific surface area. However, due to the lack of extended conjugability, their application in fluorescence sensing is limited. Herein, three conjugated hypercrosslinked polymers (the conjugated HCPs: TPPDA-DMB, TDPAB-DMB, and MTDAB-DMB) were easily prepared by the Friedel-Craft arylation reactions with phenylenediamine or phenylenetriamine derivatives and p-dimethoxybenzene (DMB). The extended conjugated structures and the 3D networks give the conjugated HCPs excellent fluorescence properties and fluorescence sensing performance for nitrophenols. TPPDA-DMB can sense 2,4-dinitrophenol (DNP) and picric acid (PA) with K values of 1.31 × 10 and 1.43 × 10 L mol, TDPAB-DMB can sense PA and o-nitrophenol (o-NP) with K values of 9.97 × 10 and 7.54 × 10  L mol, and MTDAB-DMB can sense DNP and PA with K values of 2.42 × 10 and 1.01 × 10 L mol, respectively. Experiments and theoretical calculations show that the fluorescence quenching mechanisms of the nitrophenols to the conjugated HCPs include electron transfer and energy transfer processes.