Design And CO₂ Capture Mechanism Of Ployamine Functionalized Materials With High Efficiency And Low Consumption

China is the major emitter of carbon dioxide(CO2)in the world.In order to achieve the goals of carbon peaking and carbon neutrality(double carbon)with high quality,it is necessary to develop novel CO2 capture technologies with high efficiency and low consumption.Compared with the most common techonoly,liquid amine-based absorption method,the solid amine-functionalized adsorption method has the great application potential due to the advantages of low regeneration heat,low corrosion,etc.However,the aggregation of amine molecules limits the further improvement of adsorption performance.According to the concept of "theoretical guidancemicrostructure modulation-mechanism analysis",this study designed the structure of amine-functionalized adsorption materials to realize the high dispersion of amine molecules,fundamentally solve the problem of amine-molecule agglomeration,and developed a highly efficient and low consumption ployamine functionalized adsorption materials.The main innovation achievements are as follows:(1)The research method of structural regulation guided by theoretical calculation was constructed,and the theoretical structure of highly dispersed polyamine molecules was designed and verified.In addition,the binding sites and interactions of polyamine molecules on highly dispersed carriers were revealed.Van der Waals regional analysis showed that the polyamine molecule entering the size matched pore can greatly enhance van der Waals effect.The flexible folding deformation of polyamine molecules was simulated by ab initio molecular dynamics(AIMD).It was found that the size of polyamine molecule will affect the distance between the folded amine group and the carrier dispersion site.Among them,the amine group of tetraethylenepentamine(TEPA)is the closest to the dispersion site,which is only 3.48～3.94 (?).The characterization results confirmed that polyamine molecules can accurately bind to the dispersed sites on the carrier through electrostatic interaction or covalent bonds.(2)The intrinsic structure-activity relationship between the amine loading of the polyamine-functionalized adsorption materials and the density of the dispersed sites and their adsorption properties was found,and it was confirmed that the degree of dispersion of amine groups was the limiting factor for the improvement of adsorption properties.The results of optimization and screening showed that the dispersion degree of TEPA molecule reached the maxium when it combined with the carrier dispersion site with an equal molar ratio.After TEPA molecule combined with ZIF-8 cage site(TEPA@ZIF-8),its adsorption capacity,adsorption rate constant and adsorption selectivity can be increased by 2.5,1.3 and 4.4 times respectively.Furthermore,when the dispersed sites act as proton receptors,the adsorption performance will be further improved.After TEPA molecule combined with point defect sites in proper density(TEPA-dGA),it can show an ultra-high CO2 uptake of 12.58 mmol g-1 and a 90%utilization rate of amine groups.Moreover,after 100 adsorption/regeneration cycles,the adsorption performance is stable,while the CO2 retained time can be up to 950 min g-1 under the 15/85 volume fraction CO2/N2 adsorption penetration experiment.(3)The CO2 adsorption reaction path of polyamine-functionalized materials was clarified.And the coordination mechanism of CO2 adsorption by amine groups and dispersed sites was verified.Theoretical calculation and in situ characterization results show that highly dispersed TEPA molecules can help CO2 achieve deep adsorption state.Compared with ZIF-8,TEPA@ZIF-8 can be released 15 kJ mol-1 of the system potential energy.The van der Waals interaction between amine groups and dispersed sites can effectively adjust the binding energy of CO2,which reported the physisorption of CO2 on amine-functionalized materials for the first time.The Gibbs free energy change of the system shows that the distance between the amine site and defect is proportional to the activation energy barrier of CO2 adsorption.The reduced density gradient analysis shows that the reduction of this distance will increase the attraction of point defects to hydrogen protons,which is easier to cooperate with amine sites to complete the deprotonation process and greatly improving the CO2 adsorption efficiency.(4)The adsorption material application process of high-flux CO2 adsorption combined with rapid electrothermal desorption was developed.Since the powder material TEPA@ZIF-8 is not suitable for high-flux CO2 adsorption research,this work mainly explores the industrial application potential of the macroscopic material TEPAdGA.Because inheriting the characteristics from the graphene aerogel,TEPA-dGA has excellent mechanical robustness.It retains 84%stress after 1000 times of compression,and the energy loss coefficient is only 0.051.Unsurprisingly,the high porosity of 98.8%allows TEPA-dGA to maintain a low pressure drop(less than 0.5 kPa cm-1)under the 1.6 m s-1 mixed gas in the high-flux adsorption test.In addition,since water molecules can reduce the energy barrier into the deprotonation process to improve the reaction kinetics rate,the CO2 retained time of TEPA-dGA under the 7%water content is 44.2%higher than that under the dry condition.The results of electrothermal desorption show that with the low current of 0.6 A,TEPA-dGA can completely desorb CO2 within 30 s,and the energy consumption of electrothermal desorption is only 0.6 kJ g-1 CO2.This research has designed the ideal structure of polyamine molecules anchored by dispersion sites to break the "double-layer" theoretical limit,realized the high dispersion of polyamine molecules on the carrier,developed a serial of polyamine functionalized CO2 adsorption material with high efficiency and low consumption,illustrated the the coordination mechanism of CO2 adsorption by amine groups and dispersion sites,and expanded the basic application of polyamine functionalized adsorption materials.It solves the problem of agglomeration restriction in traditional methods for obstructing the improvement of adsorption performance,and provided the important reference and theoretical guidance for the development and practical application of novel adsorption materials in the future.