The Construction And Properties Of Two Types Of Covalent Organic Frameworks With Different Dimensions

Covalent organic frameworks(COFs)are a class of framework-type crystalline organic porous polymers formed by covalently connecting organic units.Directed by the principles of reticular chemistry,and with rational design of monomer structures,researchers can design and synthesize a variety of COFs with different pore structures,pore sizes,and physical/chemical microenvironments,which can be further applied in many fileds such as separation,catalysis,photoelectric and so on.The diversity of structural design and verstile applications of COFs make them very attractive.This thesis focuses on developing new strategies to enhance stability and diversity of COFs.Through the design and synthesis of a series of COFs with novel structures,the relevant factors that affect the stability of COF skeletons have been investigated,the construction of new one-dimensional COF has been studied,and their properties have also been explored,which provides guidance for the design,synthesis and applications of new COFs.This thesis consists of the following contents:In the first part,we summarizes the research background and current progress of COFs,with a focus on their structures,linkages,synthetic methods,and applications,from which this kind of emerging crystalline organic porous materials have been introduced in details.In the second part,three COFs with the same framework structure but different side units have been designed and synthesized through varing structures of the monomers.The three COFs,which carry hydrogen(T-COF-H),methyl(T-COF-CH₃),and trifluoromethyl(T-COF-CF₃)as side units,respectively,have been used to study the influence of side chain structures on the chemical stability of COFs.Moverover,carbon dioxide adsorption by the COFs has also been investigated to explore the difference in the adsorption performance caused by the difference in side chain structures,from which the structure-activity relationship between carbon dioxide adsorption capacity and side group structure is expected to be established.Through research,we found that the introduction of trifluoromethyl can improve the chemical stability of COFs and the adsorption performance of carbon dioxide.In the third part,we have designed a new one-dimensional COF.By screening and optimizing reaction parameters such as solvent conditions,reaction temperature and reaction time,the target one-dimensional COF with high crystallinity and specific surface area has been successfully synthesized.It was further postmodified on the modifiable sites exposing on the outside of the pores,based on which a method for post-synthesis modification of one-dimensional COFs has been developed.This research provides new ideas for the design and construction of one-dimensional COFs and modifications of their structures.