The Design, Synthesis and Exploration of Two-dimentional and Three-dimentional Covalent Organic Frameworks

Author:Liu Xiao Zhou

Supervisor:jin yong ri


Degree Year:2019





The development of organic porous polymers has enabled researchers to construct pore structures at nanoscale.Template method or self-assembly of block copolymer can usually be used to prepare organic porous polymers with specific morphology.However,it is still difficult to realize the precise control of pore diameters and pore structures at nanoscale.The direct synthesis method developed in recent years has produced a series of organic porous polymers with high specific surface areas,high stability and uniform pore diameter and the pore structure can be further regulated at nanoscale.Covalent Organic Frameworks(COFs)with high crystallinity were constructed by dynamic chemistry and consequently stand out among organic porous polymers.Regular pore structures,high specific surface areas,large pore volume,controllable pore size,and uniform pore environment endow COFs with good performances in gas adsorption,storage and separation,drug release,catalysis,sensors,biological molecules immobilization,low dielectric materials,photonic bandgap materials,filtration/separation membrane,photons exchange membrane,nano coating/printing templates,chromatographic column filling materials,energy storage electrode materials,reflection coating and many other domains.A variety of reversible chemical reactions,such as the boronic acid trimerization,Schiff base reaction,cyano trimerization reaction,Knoevengel condensation reaction,were used to construct COFs.Schiff base reaction is most widely used in the preparation of COFs due to the good reversibility of the reaction and high stability of the product.With good designability,COFs with different topologies,pore sizes and environments can be obtained by selecting specific organic monomers of different configurations,lengths and functionalities.Most of COFs are two-dimensional(2D)structures,while three-dimensional(3D)COFs are limited due to the difficulty in crystalline regulation.Therefore,the construction of new 3D topologies or new 3D COFs are of great significance for the development of COFs.Meanwhile,the study of COFs in the field of drug sustainable release and explosive detection is still in its infancy,and our studies are carried out under this background.In this paper,a variety of novel imine COFs were constructed with the design of novel organic building blocks.It was worth mentioning that three new 3D COFs with rare ctn or bor topologies were synthesized in this study,promoting the exploration of 3D COFs.Furthermore,we explored the performance of COFs in the field of drug sustainable release and explosive detection,promoting the development of COFs applications.In the second chapter,the design,synthesis and characterization of three COFs with rare three-dimensional ctn(JUC-530 and JUC-531)or bor(JUC-532)topologies were introduced.FT-IR,TGA,SEM and other techniques were conducted for COFs were analysis.The crystal structure of COFs was studied by PXRD combining with theoretical calculation.N2 adsorption-desorption analysis further demonstrated high specific surface areas and uniform pore diameter distribution of the acquired COFs.It is believed that their unique topological structure will have a significant impact on the performance of these materials in different fields.In chapter 3,a new 3D COF(JUC-533)was constructed with novel monomers.High specific surface area and uniform pore size distribution were observed for the synthesized COF.Afterwards,by doping PVK in its pore channel,the new PVK@COF composite material showed better performance in detection of trace explosives.The fourth chapter introduced the design and preparation of two new 2D COFs(JUC-516 and JUC-517).The successful preparation of COFs was confirmed by various characterizations such as FT-IR and TGA.High crystallinity ensures high specific surface area and uniform pore size distribution.Apart from that,the performance of JUC-516 in drug sustainable release was explored,which expanded the applications of COFs.