Synthesis,Structural Regulation And Catalytic Application Of Ionic Covalent Organic Framework

As a new type of porous organic materials,covalent organic frameworks（COFs）have advantages of diverse synthesis methods,low density,designable porous structure,high thermal and chemical stability.Most of the reported COFs are electrically neutral.In contrast,ionic COFs（iCOFs）have been rarely reported probably due to the lack of suitable ionic monomers.Obviously,the design of iCOFs demonstrating ionic frameworks balanced by counter-ions would significantly enrich their properties and extend their applications.For example,the pore sizes of the iCOFs can be finely controlled by introducing counter-ions with different molecular sizes via ion exchange.In addition,introducing specific counter-ions with catalytic activities into the channels of iCOFs would develop novel COF-based heterogeneous catalysts.Therefore,the advantages of synthetic diversity and easy modification for iCOFs would greatly promote their potential applications in gas adsorption and separation,catalysis,etc.In this study,we have developed a range of iCOFs and studied their potential applications in heterogeneous catalysis,CO₂adsorption and conversion.This thesis can be divided into the following two parts.1.Polycondensation between 2,4,6-trihydroxy-1,3,5-benzenetricarbaldehyde and ionic monomer of triaminoguanidine hydrochloride formed an iCOF,named as COF-Cl.Ion exchange of COF-Cl with Na₂（PdCl₄）resulted in a ionic complex COF-PdCl₄,in which the Pd（II）species were further reduced into Pd（0）by Na BH₄.As a result,a novel nanocomposite COF-Pd（0）was formed.The nanocomposite was fully characterized by a range of analytic techniques including infrared（IR）spectroscopy,X-ray diffraction（XRD）,solid-state ¹³C nuclear magnetic resonance（NMR）,transmission electron microscopy（TEM）,X-ray photoelectron spectroscopy（XPS）,and N₂sorption measurement.Due the porous structure and the presence of Pd（0）nanoparticles,COF-Pd（0）was studied as a heterogeneous catalyst for a range of Suzuki coupling reactions,which showed high catalytic efficiency and good cyclic stability.2.Ion exchange of COF-Cl with Na BF₄formed a novel nanocomposite of COF-BF₄,which was fully characterized by the above-mentioned techniques.Interest,COF-BF₄showed doubled CO₂adsorption capacity compared to that of COF-Cl at the same conditions.The increased CO₂adsorption capacity can be attributed to the strong interactions between BF₄^-and CO₂ molecules.In addition,COF-BF₄demonstrated relatively high catalytic efficiency and good cyclic stability for cycloaddition of CO₂ with epoxides.This study may open up for new routes for the development of novel porous organic materials and their applications in heterogeneous catalysis,CO₂ capture and conversion.