Covalent Organic Frameworks:Design,Synthesis And Their Applications In Catalytic Reactions

In the past few decades,scientists around the world have devoted a lot of effort to the research of porous materials,which results in its rapid development.Such materials have demonstrated excellent performance in energy storage,gas separation,catalysis,etc and have been used as photo-voltaic materials due to their unique structure.Metal-organic framework materials(MOFs)are the first kind of porous materials with grid structure designed based on topological principles.On this basis,Yaghi research group further developed covalent organic frameworks(COFs)in 2005.This thesis mainly focuses on the design,synthesis and characterization of COFs and their application in catalysis.The research contents are as follows:Functional modification of the COF material has become an efficient strategy to expand its applications in various fields.In the second chapter of this thesis,T-D COF has been synthesized via a solvothermal method using 2,4,6-tris(4-aminophenyl)pyridine(TAPP)and 2,6-dihydroxynaphthalene-1,5-dicarbaldehyde(DHNDA)as organic building blocks.While synthesizing T-D COF,hydroxy groups were strategically introduced to the adjacent sites of-C=N-groups in the T-D COF.This functional group binding site leads to a strong coordination between the loaded copper metal ion and COF structure.Furthermore,the obtained copper-containing COFs,i.e.Cu@T-D COF hybrid material was used as an efficient heterogeneous catalyst for the alkyne-azide “click reaction”.This reaction was conducted in methanol/water medium and the catalyst would be recovered and recycled for next reaction without further purification.The catalytic activity and the morphology of catalyst were remained almost unchanged after four cycles of recycling.Therefore,this COF-based complex hybrid material will be of great benefit to the eco-friendly organic reactions in future.In the third chapter of this thesis,TAPP and 2,5-dihydroxyl-terephthalaldehyde(Dha)were chose as the building blocks to synthesize the TA-DA COF.Since TA-DA COF has hydroxyl groups and a large number of imine bond functional groups,we adopt a postmodification method to load copper and palladium on TA-DA COF by a step-by-step impregnation to obtain Pd@Cu COF.This catalytic system can be effectively used in tandem reaction,in which the Suzuki Miyaura reaction of halogenated benzyl alcohol with phenylboronic acid was first catalyzed on palladium while the second reaction of oxidization of benzyl alcohol into aldehyde was performed on copper active sites under TEMPO and oxygen atmosphere.A high product yield was obtained in this reaction,and the catalyst can be recycled and reused well.After being reused more than five times,the catalytic activity was negligiblly reduced.Thus,the studied catalytic system can efficiently and greenly catalyze this type of tandem reaction,and exhibit great reproducibility.