Study On The Preparation Of Metal Complex-based Porous Ionic Polymers And Their Catalysis For The Production Of Cyclic Carbonate From CO₂

Carbon dioxide（CO₂）is a major gas responsible for the global greenhouse effect.Therefore,CO₂ capture,utilization and storage（CCUS）is particularly important.However,the inert properties of CO₂ have a certain limitation on its conversion.The cycloaddition reaction of CO₂ with epoxides to prepare cyclic carbonates can not only solve this problem,but also achieve 100%atom economic and high-value utilization of CO₂.However,homogeneous catalysts that have been developed to catalyze the reaction of CO₂ with epoxides generally suffer from difficult separation and high post-treatment costs.Therefore,the development of heterogeneous catalysts is crucial for realizing industrial applications.However,in order to obtain high catalytic activity,single-functional heterogeneous catalysts often require the reaction conditions of co-catalysts and addition of organic solvents.As an important platform for the construction of bifunctional heterogeneous catalysis,Porous organic polymers（POP）also showed excellent performance in CO₂adsorption.If environmentally friendly ionic liquids（ILs）and metal complexes containing active centers are built into the POP,the coupling of capture and transformation will be achieved.Herein,we designed a series of bifunctional heterogeneous catalysts for catalyzing CO₂ and epoxides to prepare cyclic carbonates.First,we successfully synthesized a novel Salen metal-based covalent triazine ionic polymers（Sabp Al-CTFs）by an ionothermal method.Under the conditions of 273 K and 1 bar,the CO₂ adsorption capacity of Sabp Al-CTFs can reach 41.6 cm³·g^-1.Moreover,the initial slope ratio of the CO₂/N₂ adsorption curve was as high as 51.5,showing excellent CO₂ selective adsorption.In addition,Sabp Al-CTFs can achieve epichlorohydrin conversion greater than99%for the reaction of CO₂ and epichlorohydrin at 1.0 MPa and 120℃without co-catalyst and added solvent,showing high catalytic activity.Second,we successfully synthesized a bifunctional Salen metal-based porous ionic polymer（HCPBr-Salen M,M=Co or Zn）using a polymerization strategy.This strategy resulted in a certain improvement in the specific surface area of ionic polymers(S_BET=124 or 201 m²·g^-1).Among them,HCPBr-Salen Co exhibited high thermal stability and excellent CO₂ adsorption capacity(273 K,1bar,44.0 cm³·g^-1),As expected,HCPBr-Salen Co gave high yields of cyclic carbonates（97%and 86%）using pure CO₂ or low concentrations of CO₂（15%CO₂/85%N₂,v/v）as raw materials under the reaction conditions of no cocatalyst,no added solvent,and 100℃,and the reaction was carried out for 9h and 15 h respectively.Finally,think of the catalytic acceleration of enzymes under acid-base catalysis,and porphyrin,as an enzyme catalyst or a compound in metal complexes,can also be used to catalyze CO₂ cycloaddition after metallization.performance.Therefore,we adopted a“bottom-up”synthesis strategy and successfully synthesized a bifunctional heterogeneous metalloporphyrin-based catalyst（Zn Por-PiP）.The subsequent catalytic performance tests showed that Zn Por-PiP with electrophilic sites Zn²⁺and nucleophilic sites Br^-had excellent catalytic performance（1 MPa,100℃,5 h,the yield of chloromethyl ethylene carbonate can reach 99%）even in the absence of cocatalysts and added solvents.Moreover,the heterogeneous catalyst Zn Por-PiP also obtained a yield of 96%using CO₂ in simulated flue gas as raw material,showing high catalytic activity.In addition,Zn Por-PiP also has excellent substrate expansion and recyclability,and has no obvious inactivation after 6 consecutive uses,showing great potential for industrialization.