Preparation And Application Of Covalent Organic Framework Materials

Covalent organic frameworks(COFs)are an emerging class of crystalline porous polymers that are linked by covalent bonds and both skeleton and pores of COFs can be topologically predesigned.COFs have received increasing attention due to their potential applications in adsorption,catalysis and optoelectronics.In this dissertation,the advantages of synthesizing two-dimensional(2D)COFs and three-dimensional(3D)COFs by using ionic liquids as solvent were studied,and the synthesized COFs showed excellent performance in catalysis and adsorption.Based on spirobifluorene monomer,conjugated 3D COFs were successfully synthesized and their catalytic application was realized by supported metal.Therefore,this dissertation is divided into two parts:The first part:the synthesis of COFs by ionic liquids as solvent and their application in catalysis and gas adsorption.In the third chapter of this dissertation,COF-229 has been successfully synthesized by different types of ionic liquids,including[Bmim][Tf₂N],[N₄₄₄₄][Tf₂N],[P₄₄₄₄][Tf₂N]and[P₄₄₄₄][CF₃COO].Powder X-ray diffraction shows that the crystallinity of the COF synthesized under ionothermal synthesis is significantly higher than that synthesized by solvothermal method.Out of our expectation,we found that the crystallinity of COF-229 synthesized by ionothermal method is better with the increase of reaction time as compared with solvothermal method.3D-COF-229 showed high activity and wide substrate applicability towards Knoevenagel reaction.Compared with the previously reported COFs,COF-229 has a larger pore size,which,as a result,shows a wider range of substrate size selection and better substrate applicability in the Knoevenagel reaction.In the fourth chapter of this dissertation,two kinds of 2D COFs,IL COF-1 and IL COF-2,were successfully synthesized by using ionic liquid[Bmim][Tf₂N]as solvent for the first time.Compared with the time-consuming and complex solvothermal method,this new method is fast and simple,and the COFs with high crystallinity and porosity were obtained.What's more,this method can get 2D COFs with regular macroscopic shape,which still remains a big challenge for the traditional solvothermal method.In terms of application,we analyzed the experimental data according to the adsorption kinetics and adsorption thermodynamics theory,and found that both IL COF-1 and IL COF-2 showed super adsorption rate and super adsorption capacity for bisphenol A(BPA),a common pollutant in water.In the second part,conjugated 3D COFs were successfully synthesized based on spirobifluorene monomer and their catalytic application was realized by supported metal.Since the pioneering work by Yaghi in 2005,many 2D COFs with layered structure have been reported,but the design,synthesis and structural analysis of 3D COFs still remains a big challenge.The synthesis,structure analysis and characterization of 3D COFs are more difficult than 2D COFs,which restricts the development of 3D COFs.In general,conjugated COFs are confined to 2D COFs that are composed of a large number of aromatic macromolecules.In contract,3D COFs with rigid structure are difficult to form conjugated frameworks due to the usage of non-conjugated tetrahedral building units.In the fifth chapter of this dissertation,3D COF-SOFL-BDPA and COF-SOFL-PYPA with conjugated structure were successfully prepared by using spirobifluorene monomer with conjugated biplane structure as building unit,and showed very good catalytic activity towards the reaction of epoxide to cyclocarbonate.In the fifth chapter of this dissertation,we used spirobifluorene monomer as building unit to condensate with 1,4-biphenyldialdehyde and 1,4-bipyridine dialdehyde monomer,and successfully prepared 3D COF-SOFL-BDPA and COF-SOFL-PYPA.The crystal structure and pores of the COFs were determined by PXRD,gas adsorption,SEM and FT-IR.Through a"one pot method",cobalt metal was coordinated to COF-SOFL-PYPA and used to catalyze the coupling reaction of CO₂ and dimethoxyethane.The Co/COF-SOFL-PYPA showed good catalytic activity with yield>90%.