Preparation Of Functionalized Ionic Liquid Polymer And Its Application In CO₂ Adsorption And Conversion

The aggravation of greenhouse effect is mainly caused by CO₂ emission,but CO₂is also an important C1 resource.Therefore,the research of CO₂ capture and conversion technology has gained much attention.Ionic liquid polymer possessed good structure designability,which means functional group can be introduced into the structure.Meanwhile,ionic liquid polymer can be prepared as porous material,thus it can be used as adsorbent or catalyst.In this paper,the functionalized porous ionic liquid polymers were synthesized and applied for CO₂ adsorption and conversion.Firstly,the functionalized ionic liquid monomer 1-vinyl-3-methoxyethyl imidazolium glycinate?[VMOEim][Gly]?was synthesized by two-step method.Then,P?[VMOEim][Gly]?was prepared via homopolymerization.[VMOEim][Gly]was copolymerized with the crosslinker divinylbenzene?DVB?to prepare ionic liquid copolymer P?nDVB-[VMOEim][Gly]?,in which n is the molar ratio of DVB to[VMOEim][Gly].The structures of ionic liquid monomers and polymers were confirmed by NMR and FT-IR spectra.XRD analysis indicated that ionic liquid polymers were amorphous.SEM and TEM images showed that P?[VMOEim][Gly]?had a dense block,structure while P?nDVB-[VMOEim][Gly]?possessed a loose stacking structure formed by the accumulation of small particles or lamellar structures.With the increase of DVB amount,the stacking structure became looser.N₂adsorption-desorption isotherms suggested that P?[VMOEim][Gly]?possessed a non-porous structure,while P?nDVB-[VMOEim][Gly]?contained slit pores formed by the stack of lamellar structures.The results of DFT model analysis demonstrated that the ionic liquid copolymers contained mesopores and a small amount of micropores.P?0.6DVB-[VMOEim][Gly]?was further crosslinked by Friedel-Craft reaction to obtain highly crosslinked ionic liquid copolymer HP?0.6DVB-[VMOEim][Gly]?,which had increased pore volume of 0.905 cm³.g^-1and higher BET specific surface area of 508 m².g^-1.TG analysis showed that the initial decomposition temperature of ionic liquid polymers was about 160 ^o C.The prepared ionic liquid homopolymer was used for CO₂ adsorption.It was found that low temperature and low CO₂ flow rate were favorable for CO₂ adsorption,and the maximum CO₂ adsorption capacity of P?[VMOEim][Gly]?was 26 mg·g^-11 at25 ^oC and 10 mL·min^-1(space velocity 20 mL·g^-1·min^-1)CO₂ flow rate.The CO₂adsorption capacity of ionic liquid copolymers was compared under the same conditions.The result showed that as the increase of pore volume and specific surface area,both physical adsorption and chemical adsorption were enhanced.So the CO₂adsorption capacity strengthened and HP?0.6DVB-[VMOEim][Gly]?had the maximum adsorption capacity of 64 mg·g^-1.The kinetics of CO₂ adsorption on ionic liquid polymers were studied and the result revealed the pseudo-second order model fitted well with the kinetic data of CO₂ adsorption.Furthermore,the ionic liquid homopolymer P?[VMOEim][Gly]?showed good reusability and the CO₂ adsorption capacity was reduced by 15%after ten-cycle adsorption-desorption experiments.However,the cycle performance of HP?0.6DVB-[VMOEim][Gly]?was unsatisfactory due to the collapse of pores during the regeneration process.Ionic liquid copolymers were also used as the catalyst for the cycloaddition reaction of CO₂ with epichlorohydrin.HP?0.6DVB-[VMOEim][Gly]?possessed the highest catalytic activity among six ionic liquid copolymers.The yield of product4-?chloromethyl?-1,3-dioxolan-2-one was 94%under the following conditions:atmospheric pressure,the catalyst amount of 4%,the reaction temperature at 130 ^oC,and the reaction time for 10 h.And the catalytic activity was maintained after five-cycle experiments.