Construction Of Imidazolium Carboxylic Acid Zwitterionic Materials And Their Catalytic CO₂ N-formyl(methyl)ation

Since the second industrial revolution,the burning of fossil energy has greatly promoted the development of human life and the progress of science and technology.However,there are two sides to everything.At the same time,the progress is the global climate change caused by a large number of greenhouse gas emissions,temperature rise,frequent extreme climate,ecological changes,species extinction and so on.Therefore,in order to solve the problem of excessive CO₂ concentration in the earth's atmosphere,many methods of CO₂ utilization have been studied and explored.Among them,the synthesis route of high value-added drug molecules using CO₂ as carbon source has attracted extensive attention of scientific research.In different chemical transformations of CO₂,formylation and methylation of amines have been widely studied because of the wide application of C-N bond in drugs.However,there are still some defects in the N-formylation reaction using CO₂ as carbon source,such as easy decomposition of catalyst,complicated preparation,strong corrosion,catalyst recovery and complex purification process.In view of these defects.In this project,hydrogen containing silane was selected as hydrogen donor,and imidazolium carboxylic acid amphoteric salt and imidazolium carboxylic acid amphoteric salt were used as catalysts to catalyze N-formylation.1.Chemocatalytic upgrading of greenhouse gas CO₂ to valuable chemicals and biofuels has attracted broad attraction in recent years.Among the reported approaches,N-formylation of CO₂ with an amine is of great significance due to its versatility in construction of N-containing linear and cyclic skeletons.Herein,a stable N-heterocyclic carbene-carboxyl adduct(NHC-CO₂)was facilely prepared and could be used as a recyclable zwitterionic catalyst for efficient CO₂ reductive upgrading via either N-formylation or further coupled with cyclization under mild conditions(25?,1 atm CO₂)using hydrosilane as hydrogen source.More than 30 different alkyl and aromatic amines could be transferred into corresponding formamides or benzimidazoles with remarkable yields(74%-98%).The electronic effect of the introduced substituent on NHC-CO₂ was found to evidently affect the thermostability and nucleophilicity of the zwitterionic catalyst,which is directly correlated with their catalytic activity.Moreover,NHC-CO₂ could supply CO₂ by in-situ decarboxylation at a specific temperature that is dependent on the introduced substituent type.Experimental and computational studies showed that carboxyl species on NHC-CO₂was not only a nucleophilic center but also a C1 source by rapidly capturing or substituting with ambient CO₂ during hydrosilylation.In addition,a simple conceptual process was designed for the product purification and catalyst recycling,with good small-scale feasibility.2.On the basis of(1),we designed a catalytic material containing amphoteric imidazolium carboxylate.In this part,we found a good balance between preventing water adsorption in air and promoting the catalytic activity of zwitterionic imidazolium carboxylate by introducing hydrophilic pyrrolidone group and hydrophobic benzene group.Under the same reaction conditions,the catalytic material showed better catalytic activity.In addition,the chemical structure of the polymer containing imidazolium carboxylate amphoteric salt has been confirmed by IR and NMR,which is consistent with the preliminary design.3.On the basis of(2),we further designed a polyvinylbenzene microspheres with high dispersion.Polyethylene spheres with uniform size and regular morphology were synthesized by two-phase method,and their catalytic activities were much higher than those of imidazolium carboxylic acid amphoteric salt catalyst and Han imidazolium carboxylic acid amphoteric salt catalyst.The surface morphology of the polythene microspheres containing imidazolium carboxylate amphoteric salt was characterized by SEM.It was found that the polythene microspheres had regular morphology and porous surface.The porous surface was also found to be the source of its high catalytic activity by BET characterization.The reusability of the polythene microspheres containing amphoteric imidazolium carboxylate was discussed,and it was found that the polythene microspheres had good reusability.