Basic Study On CO₂ Capture By Grafting Organic Amine Onto Graphite Oxide

Graphene oxide grafted with organic amine is a potential CO₂ adsorbent.In order to promote the development and design of polyamine graphene oxide,it is urgent to conduct a detailed and in-depth study of its micro-reaction mechanism.In this paper,the quantum chemistry method is used to study the microcosmic mechanism of three kinds of amine groups grafted with graphene oxide（GO）and captured CO₂ in detail,which provides a reliable theoretical reference for the development and design of solid CO₂ adsorbent based on graphene oxide in the future and promotes the development of CO₂ emission control technology.The mechanism of amine grafted GO was explored and the stability of three amine grafted GO was compared.A graphene oxide model was constructed,and the mechanism of grafting GO with EDA was explored in detail.Based on this mechanism,GO was grafted with DETA and TETA,and the potential energy of the product was calculated.The theoretical calculation results show that for the epoxy group on GO,EDA can be grafted by attacking the active C atom adjacent to the epoxy group,while for the carboxyl group on GO,EDA can be directly grafted by attacking the C atom of the carboxyl group,and the grafting reaction can be catalyzed by H₂O and EDA;The reaction activation energy of EDA grafted carboxyl group（23.19 kcal/mol）is lower than that of EDA grafted epoxy group（28.57 kcal/mol）,indicating that the thermal stability of EDA grafted GO carboxyl group is much better than that of EDA grafted GO epoxy group;The potential energy of DETA grafted GO products（about 14-25 kcal/mol）and TETA grafted GO products（about33-49 kcal/mol）are higher than those of EDA grafted GO products.Therefore,EDA grafted GO is the most stable and amine is more easily and effectively grafted onto the carboxyl group on GO than epoxy.Based on the mechanism study of amine grafted GO,three models of amine grafted GO were obtained and their CO₂ adsorption properties were theoretically studied.Predict potential reaction sites through electrostatic potential analysis diagrams and perform physical adsorption calculations,and ultimately determine chemical adsorption sites through the advantages and disadvantages of physical adsorption.Based on the calculation and analysis of the physical and chemical adsorption of three types of graphene diamine oxide,it is concluded that water catalysis can greatly reduce the reaction energy barrier of three types of amine grafted GO and promote the progress of the reaction;In the presence of water catalysis,EDA-GOCA（23.3 k J/mol）and TETA-GOCA（39.1 k J/mol）are relatively easier to adsorb CO₂ than EDA-GOEP（41.1 k J/mol）and TETA-GOEP（78.0 k J/mol）.Therefore,these two types of amine grafted graphene oxide can improve the conversion of hydroxyl and epoxy groups to carboxyl groups in practical production,thereby improving the CO₂ adsorption efficiency;When catalyzed by water,DETA-GOEP（37.1 k J/mol）is relatively easier to adsorb CO₂ than DETA-GOCA（56.5 k J/mol）.Therefore,DETA-grafted graphene oxide can improve the conversion of hydroxyl and carboxyl groups to epoxy groups in practical production,thereby improving the CO₂ adsorption efficiency.In terms of stability,EDA grafted GO has the best stability,and the stability order of the three amino grafted GO is:EDA-GO>DETA-GO>TETA-GO;From the perspective of CO₂ adsorption performance,combining direct adsorption,one water catalysis,and two water catalysis,EDA has the best performance.The order of CO₂ adsorption performance is:EDA-GO>DETA-GO>TETA-GO.Therefore,amine grafting stability and adsorption performance are consistent.Among the three amine grafting GOs,EDA-GO is the best solid adsorbent,and compared to EDA-GOEP,EDA-GOCA has better adsorption performance and grafting stability.It can further enhance the CO₂ adsorption efficiency of EDA-GO by improving the conversion rate of hydroxyl and epoxy groups to carboxyl groups.