The flexible covalent organic frameworks containing tetraphenylethylene (TPE) for the detection of 2,4-dinitrophenol and uptaking iodine

Tetraphenylethene (TPE) is a typical aggregation-induced emission chromophore. However, there are no reports on the flexible COFs containing TPE units until now. Herein, two flexible TPE-COFs (HTATPE and TTATPE) were synthesized via Schiff base polymerization reaction. HTATPE and TTATPE exhibit significantly large specific areas of 2274 and 1777 m 2 g −1 , respectively, along with high thermal stability, and partial crystallinity. The flexible TPE-COFs demonstrate high sensitivity in fluorescence detection for 2,4-dinitrophenol (DNP). Their K SV values are measured at 3.96 × 10 4 and 3.30 × 10 4 M −1 . Their fluorescence sensing mechanisms to DNP were PET and IFE process. The recovery experiment in river sand samples proved that TTATPE has sufficient sensitivity as a chemical sensor for DNP in environmental samples. The iodine capture capacities of HTATPE and TTATPE were 4.28/4.04 g g −1 , 24.71/24.61 mg g −1 , and 284.85/287.26 mg g −1 in the I 2 vapor at 350 K, 100 mg L −1 iodine-cyclohexane solution, and 300 mg L −1 iodine-water solution. The iodine adsorption behaviors conformed to the pseudo-first-order model. PXRD and Raman spectra showed that iodine absorption is a chemical adsorption process caused by charge transfer.