Construction And Performance Study Of Ionic Polymers For Efficient Capture And Conversion Of CO₂

As“carbon peak,carbon neutrality”has become a global consensus,the effective separation and resource utilization of CO₂ has become an important issue that researchers need to solve urgently.Among them,the preparation of cyclic carbonates by cycloaddition reaction of CO₂ and epoxides has become one of the important ways of CO₂ chemical utilization due to its greenness and high atom economy.Ionic polymers（IPs）,as relatively low-cost,structurally stable,charged organic polymers with abundant active sites,have been extensively studied in applications such as gas adsorption and heterogeneous catalysis.However,IPs suffer from the disadvantages of the conventional preparation method（solvothermal method）such as solvent dependence,harsh reaction conditions,poor product yields and poor CO₂ adsorption performance.Therefore,it is still very urgent to develop green synthetic methods and design new heterogeneous catalytic materials with good performance and high activity.Based on this,this paper designed and synthesized three new ionic polymers and their composite catalytic materials through various methods.The details of the research are as follows:（1）In this work,a class of imidazolium-based triazine ionomers were synthesized by mechanochemical method and proved to be successfully prepared by serial characterization.The experimental results showed that these IPs all showed good catalytic activity in catalyzing the cycloaddition reaction of CO₂ with epoxide under solvent-and cocatalyst-free conditions,with the yield of cyclic carbonate up to 99%,while the IPs catalysts also exhibited good cycling performance.（2）For heterogeneous catalysts,excellent CO₂ adsorption performance will be more favorable for their catalytic conversion reactions,while addressing the problem of insufficient CO₂ adsorption capacity（caused by low specific surface area and pore channel deprivation）of the IPs prepared in the previous work.Based on this,a series of triazine porous ionic polymers（PIPs）were constructed for CO₂ capture and conversion by post-crosslinking strategy in this work.These PIPs have a high surface area and their CO₂ adsorption capacity is increased about 10 times compared to the original materials(from 9.3mg·g^-1 to 103.2 mg·g^-1);they can also act as recoverable catalysts to efficiently catalyze the immobilization of CO₂ to cyclic carbonate with a yield of 99%.The synergistic catalytic mechanism based on triazine and imidazole moieties was proposed jointly with the reaction kinetics and in situ FTIR experimental results.This idea of preparing functionalized PIPs materials by a post-crosslinking strategy provides new insights into the field of CO₂separation and conversion.（3）Usually ionic covalent organic frameworks（iCOF）as an ionic polymer material are widely used in catalysis because of their abundant ionic sites,but they are usually limited by expensive linkers,complicated synthesis,low specific surface area and insufficient CO₂adsorption capacity.Therefore,it is necessary to develop a simple and low-cost iCOF for synthesis.Therefore,a series of M@iCOF core-shell hybrid materials with built-in NH₂-UIO-66 were constructed for CO₂ adsorption and conversion.Experimental results showed that the M@iCOF materials achieved a significant increase in CO₂ adsorption from 0.99mmol·g^-1（iCOF）to 3.33 mmol·g^-1（M@iCOF）.Furthermore,M@iCOF not only maintains excellent catalytic activity in catalytic reactions,but also has great advantages in terms of reaction kinetics.This strategy provides a simple and effective way to construct core-shell materials with low cost and good adsorption and conversion performance.