Study On The Controlled Synthesis And Property Of Several Novel 2D Covalent Organic Frameworks

Covalent organic frameworks(COFs)have been thoroughly studied over the past decade,and significant progresses have been achieved on the design,synthesis and properties of COFs.However,owing to the difficulties in the growth of single crystal COFs and the complexities in structure modeling from PXRD pattern,structure studies on COFs has been less developed.The majority of 2D COFs adopt eclipsed AA stacking and only a handful of them adopt other stackings.Since packing manner of the layers strongly affects not only the topology but also the physical and chemical properties of 2D COFs,we seek to study the main factors which affect the lay stacking of 2D COFs,and try to reveal the structure-properties relationship among 2D COFs with different stackings.Another challenge in functional COFs is the construction of chiral COFs(CCOFs),the direct synthesis of CCOFs with intrinsic chiral monomer through bound-up strategy still remains challenging,up to date,only TADDOL derivatives and M(salen)were used as chiral building blocks to make CCOFs,the majority of privileged ligands for asymmetric catalysis and enantioselective sensing remain untouched.This dissertation includes five chapters as follows:In Chapter 1,the research background was introduced including the rational design of linkages,structure study of COFs and their applications in various fields.The opportunities and challenges remained in this area together with overviews of the topic and research progress were also discussed and presented.In Chapter 2,by co-condensation of triamines with and without alkyl substituents(ethyl and isopropyl)and a di-or trialdehyde,a family of two-,three-,and four-component 2D COFs with AA,AB,or ABC stacking was prepared.The alkyl groups were periodically appended on the channel walls and their contents,which can be synthetically tuned by the multivariate(MTV)approach strategy,controlled the stacking model and chemical stability of 2D COFs by maximizing the total crystal stacking energy and protecting hydrolytically susceptible backbones through kinetic blocking.Specifically,the COFs with higher concentration of alkyl substituents adopted AB or ABC stacking,while lower amount of functionalities led to the AA stacking.The COFs bearing high concentration of isopropyl groups represent one of identified COFs that can retain crystallinity and porosity in boiling 20 M Na OH solution.After postsynthetic metalation with an iridium complex,the2,2?-bipyridyl-derived COFs can heterogeneously catalyze C-H borylation of arenes,whereas the COFs with isopropyl groups exhibits much higher activity than the COFs with ethyl groups and nonsubstituents due to the increased porosity and chemical stability.In Chapter 3,two CCOFs prepared by imine-condensation of enantiopure Binol-based di-aldehyde with tetra-aniline(CCOF 7)or symmetric tri-aniline(CCOF8)were obtained after fully screening the scope of various aniline monomers and synthesis condition.CCOF 7 was tested for fluorescence sensing towards chiral compounds in acetonitrile and it was enantioselective towards a range of terpenoids.CCOF 7 could be easily exfoliated into nanosheets(7-NS)in Me OH and the higher enantioselective ability was achieved when 7-NS was used in fluorescence sensing towards chiral terpenoids in acetonitrile,compared with that of bulky CCOF 7.Furthermore,7-NS was electrospun to make free-standing COF membrane,which was enantioselective towards a range of chiral terpenoids vapors,holding the great promise for the development of COFs for enantioselective sensing.In Chapter 4,proline-containing vinyl monomer was synthesized by one step reaction,methyl acrylate,proline-containing vinyl monomer and radical initiator(AIBN: 2,2-azobisisobutyronitrile)were then impregnated into the cavities of MIL-101/COF-TPBD,after that,in situ radical copolymerization were carried out,affording CP@MOF and CP@COF.The obtained hybrid materials revealed excellent diastereo-and enantioselectivities for the direct asymmetric aldol reactions with up to99% ee and 96:4 dr,showing better asymmetric catalytic property than that of proline,CP or most reported heterogeneous catalyst.In Chapter 5,a briefly summary and prospect of this thesis were given.