Theoretical Study Of The Effect Of Ionic Liquids On The Thermodynamics Of H₂ Activation Reaction By FLPs

Catalytic conversion of carbon dioxide into organic compounds such as methanol can not only alleviate the environmental crisis caused by climate warming caused by CO₂,but also solve the energy crisis caused by fossil energy shortage.In the reaction of CO₂+H₂,H₂activation is the most important step,but efficient H₂ activation is a difficult task.Frustrated Lewis pairs（FLPs）,as a non-metallic catalyst,play an important role in the activation of H₂.In addition,the solvation effect also plays a great role in the activation of H₂.However,in the research of FLPs to activate H₂,neutral organic solvents are mostly used.Due to the volatility of aromatic organic solvents,this may have a negative impact on the environment,this paper selects ionic liquids（ILs）as a green solvent to replace the currently commonly used aromatic organic solvents.Aiming at the influence of ILs on the H₂ activation of FLPs,the quantum chemistry simulation software Gaussian09 was used to study thermodynamics.The main research contents are as follows:（1）Using density functional theory（DFT）,combined with the SMD implicit solvation model,the thermodynamic study of the inter-and intra-molecular FLPs activate H₂ reaction in toluene solvent and ILs solvents are carried out.The free energies of reaction Gibbs and the free energies of solvation are calculated.The results show that the ILs solvents have a more positive impact on the overall Gibbs free energies,that is,the computed overallΔG in the ILs solvents is about 10 kcal mol^-1 smaller than the computed overallΔG in the toluene solvent,indicating that ILs is easier to promote than toluene FLPs activate the hydrogen reaction to proceed.Through thermodynamic energy decomposition analysis,it is found that ILs are more conducive to the cleavage of H-H bonds,and are not conducive to proton attachment,hydride attachment and zwitterionic stabilization.More importantly,the type of FLPs has a greater impact on the catalytic reaction.More importantly,the catalytic reaction of solvents to FLPs is related to the type of FLPs.The results show that the contribution of ionic liquids to the activation of hydrogen by intra-molecular FLPs is greater than the contribution of inter-molecular FLPs to H₂ activation.（2）The B3LYP/6-311++G**method was used to calculate the single-point energy of the structure of the zwitterionic products of FLPs,and the natural bond orbital theory（NBO）was used to calculate the charge in the above structure.Through the analysis of the electronic structure of the zwitterionic products,that is,the distance between Lewis acid and base centers,the natural population analysis（NPA）charge,and dipole moments,it is found that the catalytic performance of FLPs activated hydrogen is mainly related to the polarizability:1)Compared with neutral organic solvents,ILs composed of cation and anion have greater polarizability;2)Compared with inter-molecular FLPs products,due to the localized partial positive and negative charges are easier to separate,the intra-molecular FLPs products get more polarized.Therefore,intra-molecular FLPs have higher catalytic activity for H₂activation than inter-molecular FLPs.Through the above theoretical research,we proposed the possibility of constructing an ILs-based FLPs catalytic system and using it for H₂activation and other important reactions.