Synthesis Of Triazine-Based Covalent Organic Frameworks And Their Applications As Fluorescent Sensors

Covalent organic frameworks(COFs)are a kind of crystalline organic polymer materials with porous structures connected by covalent bonds with C,H,0,N,B and other light elements.Because of their advantages of good thermal stability and chemical stability,large specific surface area,permanent porosity,adjustable structure and easy functional modification,they are widely applied in many fields.At present,the synthesis of COFs mainly adopts bottom-up strategy and post-synthetic modification method.In this paper,two kinds of COFs were prepared by post-synthetic modification method and used as fluorescent sensors for ion detection and temperature sensing.We chose TAPT-DHTA-COF as the precursor,which contains hydroxyl groups in the pores and can be used for functionalization TAPT-DHTA-COF was modified with R-(-)-2-benzoyl chloride or phosphorus oxychloride,respectively.The two new COFs,PP-TAPT-DHTA-COF and PC-TAPT-DHTA-COF have good stability and fluorescence performance in water and organic solvents.Among them,R-(-)-2-phenylpropionyl was success fully modified in the channel thro ugh acrylatio n,and the modified PP-TAPT-DHTA-COF has a dual fluorescence emissions.Few COFs with dual fluorescence emissions have been reported so far,such a dual-emission COF can be used as a ratiometric fluorescent sensor to improve the sensitivity and accuracy of sensing.The COF modified by phosphorus oxychloride,PC-TAPT-DHTA-COF,is similar to that of the raw material COF,with only one fluorescence emissions in aqueous solutionsThe modified COFs materials were used for ion detection and temperature sensing.PP-TAPT-DHTA-COF can be used as a fluorescent probe to detect MnO4-.Because the detection is based on the intensity ratio of the dual fluorescence emissions,the selectivity and sensitivity are much higher than that of the unmodified COF.At the same time,PP-TAPT-DHTA-COF can also be used as a temperature sensor.This is the first application of non-lanthanide COF as a ratio temperature sensor,which has the advantages of high accuracy,sensitivity and spatial resolution compared with traditional temperature sensors,and can satisfy more complex detection environment.PC-TAPT-DHTA-COF can detect Fe3+,CrO42-,Cr2O72-and MnO4-,but it has no obvious advantage over TAPT-DHTA-COF.