Computational Research On The Conversion Of Carbon Dioxide In Homogeneous Solution

With the emergence of environmental issues such as global warming,melting glaciers,and sandstorms,human beings are paying more and more attention to environmental protection.Excessive concentrations of carbon dioxide（CO₂）will cause the greenhouse effect.How to use CO₂ rationally is a problem that scientists have been devoted to.If CO₂ can be converted into other valuable substances through chemical technologies,it will not only alleviate these problems,but also obtain other valuable molecules.Organic bases play a key role in the catalytic conversion of CO₂.Among them,organic bases with specific structures can fix and release CO₂ under certain conditions,which provides a preliminary preparation for the CO₂ conversion reactions.Ionic liquid catalysts can be used to catalyze reactions of CO₂ with small organic molecules,which can convert CO₂ into other valuable organic substances,improve the efficiency of CO₂ conversion,and thereby alleviate environmental problems like the greenhouse effect.The rapid development of modern technology has greatly promoted the research and development in the field of designing various chemical calculation software,combining theoretical calculations with experiments,analyzing experimental data from a microscopic perspective,and providing theoretical support for experimental results.Based on this,this paper carried out two calculations about CO₂:1.Using DFT calculations,the mechanism of the homogeneous cycloaddition reaction of CO₂ and epichlorohydrin catalyzed by amino functionalized ionic liquid（AFIL）was systematically studied.The catalysis and auxiliary ring opening of AFIL in the reaction process were analyzed.The results showed that the reaction mechanism included two parts.Firstly,carbonic acid（H₂CO₃）formed by dissolving CO₂ in water interacts with AFIL to generate protonated AFIL and bicarbonate（HCO₃^-）.Secondly,the protonated AFIL which has dual function of liquid and organic base can catalyze the homogeneous cycloaddition reaction of CO₂ and epichlorohydrin to produce cyclic carbonate.Among them,the imidazole ring part of AFIL is responsible for assisting the ring-opening reaction of epichlorohydrin in the early stage of the cycloaddition reaction.The protonated amino is responsible for stabilizing the Br^-anion for nucleophilic attack.Enlightened by the DFT calculations,we assume that it is possible to further design a dual-functional catalyst with a similar structure to improve the conversion rate of CO₂.2.Multifunctional 1,3-diphenylguanidine（DPG）can effectively and reversibly capture CO₂ in the form of crystalline hydrogen bonds to yield bicarbonate dimers under mild conditions.In order to explore the binding form on the molecular scale and get a preliminary understanding of the hydrogen bond interaction in the process of CO₂ fixation and capture,we performed molecular dynamics（MD）simulations on the simple DPG system,the mixed system of CO₂ and DPG solution,and the protonation system.The calculation results of this study include the number of hydrogen bonds and the length of hydrogen bond in different systems.In the hydrogen bond model of protonated diphenylguanidine（DPGH⁺）and HCO₃^-,the simulated double hydrogen bond model is consistent with the experimental results.The hydrogen bond interaction between DPG/CO₂ and DPGH⁺/HCO₃^-can show that DPG solution can effectively capture CO₂.In addition,other organic bases TMG and TPG,with similar structure to DPG,were also quantified to calculate the energy required for the formation of double hydrogen bonds.At the same time,the mechanism of the cycloaddition reaction of CO₂ and N-benzyl amine catalyzed by DPG and Ag⁺was also preliminary calculated.