Application Of Carboxyl Functionalized Covalent Organic Framework In Proton Conduction And Humidity Sensing

In the past decades,scientists have constructed a large number of diversified advanced porous materials,such as zeolite,porous organic polymers（POPs:Porous Organic Polymers）,metal organic frameworks（MOFs/PCPs:Metal Organic Frameworks/Porous Coordinative Polymers）and covalent organic frameworks（COFs:Covalent Organic Frameworks）,these porous materials in new energy,chemical,photoelectric materials and other scientific and technological fields can be widely applied to research.Among them,COFs,as a new and flourishing ordered porous material,have attracted more and more interest and attention from researchers since their first discovery.Covalent organic frameworks are porous polymers with two dimensional（2D）and three dimensional（3D）structures formed by strong covalent bonds between monomers.Due to the highly regular structure and the strong covalent bond structure,COFs have the advantages of high stability,low density,large surface area natural porosity and high crystallinity,so COFs are widely used in the fields of sensing,catalysis,energy storage,conduction and material separation.In this paper,we mainly synthesized a new type of COFs.Through a variety of characterization methods and data analysis,it was proved that the COFs material has high crystallizability and good chemical stability.We mainly studied the application of the new type of COFs in two aspects,such as proton conductor and humidity sensing.The specific works are as follows:（1）The carboxyl functional covalent organic framework Py-COOH-COF with high crystallization and excellent porosity was synthesized using the"bottom-up"strategy.Under 98%relative humidity,its conductivity reached 5.95×10^-3S cm^-1and activation energy was 0.16 e V.By loading polyethylenimide（PEI）into the pore of COFs by diffusion method,the proton conductivity of the composite can reach 2.34×10^-2S cm^-1and the activation energy is 0.04 e V at the relative humidity of 98%and the temperature of 80^oC,which meets the application standard of commercial proton membrane.（2）The above（1）covalent organic framework functionalized by carboxyl group will have obvious color changes when exposed to air due to the influence of humidity,and its color changes from orange to dark brown in a reversible and rapid process.Based on infrared spectroscopy,Raman spectroscopy,solid nuclear magnetic carbon and hydrogen spectra and water vapor adsorption data,it can be inferred that by introducing carboxylic acid base group,pyrene COFs is adjusted from hydrophobic structure to hydrophilic structure,and its water capture ability is greatly improved,which enables Py-COOH-COF to efficiently change its electron cloud distribution through ultrafast migration of protons under the condition of strong adsorption of water clusters.The band structure and appearance of the material were changed.The proton conductivity and humidity discoloration properties of the material make it an ideal humidity sensing material.