Study On Construction Of Functionalized Porous Organic Polymer And Catalytic Performance For CO₂ Cycloaddition Reaction

The rapid development of industrialization and significant consumption of fossil fuels have led to significant emissions of carbon dioxide（CO₂）and greenhouse gases,resulting in increasingly serious environmental problems.The chemical conversion of CO₂ to synthesize high value-added chemicals is an important way to reduce carbon emissions.Among them,the high value-added product cyclic carbonate synthesized by CO₂ and epoxides has a 100%atomic utilization rate,which is in line with the concept of green chemical engineering and circular economy.Super crosslinked ionic polymers have excellent physical and chemical properties such as high specific surface area,large pore volume and easy chemical regulation,which can be used as heterogeneous catalysts for the catalytic cycloaddition of CO₂.In this paper,two types of imidazole based and histidine based super crosslinked ionic polymer catalysts were designed and constructed for CO₂ cycloaddition reaction,focusing on the difficulty in the catalyst separation from products of CO₂ cycloaddition reaction with traditional homogeneous catalysts and the problems of harsh reaction conditions and low reaction activity of current heterogeneous catalysts.The specific research content is as follows:Firstly,using N-benzylimidazole as a functional monomer,three imidazole functionalized super crosslinked ionic polymers（HIPs）with different structures were successfully constructed through quaternization and copolymerization reactions.The prepared catalysts were characterized using various characterization methods,and their CO₂ adsorption performance and cycloaddition reaction catalytic performance were investigated.The obtained imidazolyl HIPs have high specific surface area,large pore volume,rich mesoporous structure,and a large number of Lewis bases and ionic active sites.The prepared imidazolyl HIPs exhibit good CO₂ adsorption capacity and selectivity,and achieve efficient catalysis for CO₂ cycloaddition reactions under mild conditions without metals,cocatalysts,and solvents.In addition,this type of catalyst exhibits excellent cycle stability,structural stability,and substrate universality in CO₂cycloaddition reactions.In order to further improve the activity of the catalyst,a series of histidine based HIPs with different structures were successfully constructed by copolymerizing histidine monomers containing carboxyl,amino,and quaternary ammonium reaction sites with benzyl halides.The prepared histidine HIPs obtained outstanding structural characteristics,rich hydrogen bond donors,Lewis bases and ionic active site,and higher CO₂ adsorption performance,and could efficiently catalyze the progress of CO₂cycloaddition reaction under mild conditions without metal,cocatalyst and solvent.Moreover,the prepared histidine HIPs showed excellent cycle stability,structural stability and substrate universality.In addition,this type of catalyst can also achieve selective adsorption and catalytic conversion of low concentration CO₂.The synergistic effect between hydrogen bond donors,basic sites,nucleophilic halogen ions and outstanding structural characteristics make the catalyst show excellent catalytic performance for CO₂ cycloaddition reaction.