Adsorption And Detection Of PFCs On Covalent Organic Frameworks And Photonic Crystal Hydrogels

Perfluorinated compounds（PFCs）are persistent organic pollutants in the environment.Due to its hydrophobic and oil repellent characteristics,it has been widely used in the fields of textile,fire protection,metal electroplating and semiconductor production in the past few decades.Due to its wide application in the world and its difficult degradation in the ecological environment,the substance has been detected in the ecological environment all over the world in recent years.Therefore,the research on the adsorption and detection of PFCs is of great significance.Covalent organic frameworks（COFs）are a kind of crystalline polymer materials formed by covalent bonding of light weight elements such as carbon,nitrogen,hydrogen and oxygen.They have the characteristics of ordered porous structure,high specific surface area,easy functionalization,high chemical stability and thermal stability.They have become a research hotspot in the field of environmental analytical chemistry.The study of COFs materials with specific adsorption function has great application prospects for the treatment of pollutants in environmental water.In addition,photonic crystal hydrogel（PCH）has the characteristics of simple,convenient and visual expression.Compared with the traditional detection methods,it avoids the restriction of large instruments,professionals and long analysis time.In the present work,COFs materials with different functional groups were synthesed and characterized basing on ligand construction and functional modification design.The adsorption of PFCs in environmental water was realized by using the obtained COFs.At the same time,the cationic PCH was designed,synthesized and characterized,and applied succefully in the detection of PFCs in environmental water.The main research contents of this paper are as follows:（1）Based on the functionalized COF strategy,spherical vinyl COF was synthesized by using 2,5-Diethenyl-1,4-benzenedicarboxaldehyde（Dva）and 1,3,5-tris（4-aminophenyl）benzene（Tab）at room temperature.The amino group containing material COF-NH₂ was synthesized by click reaction and characterized by FT-IR,SEM,PXRD,TGA and N₂ adsorption and desorption.It was found that COF-NH₂ had excellent adsorption effect on a variety of PFCs through hydrogen bonding,with a removal rate of 99%.The saturated adsorption capacity reaches 175.44 mg/g,and the adsorption equilibrium can be reached within 6 h mainly with single-layer chemical adsorption,which meets the application requirements in practical water bodies.（2）Based on the ligand design strategy,the fluorine containing material COF-F was synthesized by solvothermal method using 4,4’,4’’-（1,3,5-Triazine-2,4,6-triyl）trianiline（TFTA）and 2,3,5,6-Tetrafluoroterephthalaldehyde（TAPT）.It was characterized by FT-IR,SEM,PXRD,TGA and N₂ adsorption and desorption.It was found that COF-F had excellent adsorption effect on a variety of PFCs through fluorine bond and hydrophobic interaction,with a removal rate of 99%.The saturated adsorption capacity reaches 192.31 mg/g,and the adsorption equilibrium can be reached in 6 h mainly with monolayer chemical adsorption,which is of great significance in the field of water purification.（3）In order to detect potassium perfluorooctane sulfonate（PFOS）in water,a methacrylic acid ethoxylated three methyl ammonium chloride（MTAC）modified photonic crystal hydrogel（PCH）was designed and prepared by crosslinking MTAC and polyethylene glycol two acrylate（PEGDA）to achieve the purpose of loading cationic CH₃NH⁺in the gel network structure.Through technical characterization and research,it is found that MTAC-PCH has a good detection effect on PFOS.After adsorption of PFOS,the gel film will shrink,leading to blue shift of PCH diffraction peak.The minimum detection concentration of PCH for PFOS is 1.8×10^-6 M.The sensor has good mechanical performance and reusability.It still has a good response to PFOS after repeated regeneration.The recovery of spiked standard was between93.6%-97.5%in the real samples determination.