The Catalytic Conversion Of Carbon Dioxide To Organic Carbonates Under Mild Conditions

Recent years,the global climate change,caused by the accumulation of anthropogenic greenhouse gases(GHGs)in the atmosphere,has aroused worldwide attentions.Many efforts,such as reducing the GHG production,limiting the GHG emission and lowering the amount of existed GHGs,are taken to mitigate the greenhouse effect.Among all of the approaches,the CO₂ chemical conversion is considered promising due to its simplicity and high efficiency,and is widely used in the industrial processes.The cycloaddition of CO₂ and epoxides is a thermodynamic spontaneous reaction with 100%theoretical atom efficiency,and these features make it more advantageous than other methodologies.Up to now,there are a variety of catalysts developed to catalyzing the cycloaddition reaction,and most of them are reported to be effective.However,the toxicity,low stability and recyclability of homogeneous catalysts,as well as the activity loss and low TON/TOF of heterogeneous catalysts,still need to be improved to meet the principles of green chemistry.Therefore,ionic liquid was chosen as the research object in this work,and systematic research was conducted about its application in the CO₂ cycloaddition reaction.Besides,the application of protic ionic liquid in open-chained carbonate synthesis was also studied.This thesis was composed of 5 chapters.Chapter I.The cause of greenhouse effect and the significance of CO₂ chemical conversion were reviewed in this chapter.The available chemical conversion methodologies and the corresponding catalytic systems were listed.Besides,the concepts related to ionic liquids and supramolecular chemistry were also introduced.Chapter II.A series of N-alkyl-N-methyl morpholinium bromides were obtained using one-step synthesis.These ILs were taken to cooperate with metal salts,and used as catalysts in the CO₂ cycloaddition reaction.As a result,the>99%conversion of epoxide and 100%selectivity of cyclic carbonate was achieved under 298 K and 1 bar CO₂ pressure.Besides,the reaction system was studied using NMR and ESI-MS,and a possible mechanism was supposed based on the characterizations.Chapter III.The potential reaction routes of morpholinium IL-zinc bromide catalyzed CO₂ cycloaddition reaction was investigated using conditional control experiment and computational chemistry method.Besides,the net CO₂ emission of the system was estimated as well.Chapter IV.Based on chaotropic effect,a new supramolecular complex BOF[6]was synthesized with Na₂B₁₂H₁₂ and cucurbit[6]uril.The BOF[6]was characterized and applied in immobilizing morpholinium ILs.The catalytic activity of immobilized IL in CO₂ cycloaddition reaction was also tested in this chapter.Chapter V.Tetramethylguanidine was taken to promote the reaction of alcohol,alkyl bromide and CO₂,the reaction species were characterized with NMR,and the reaction mechanism was investigated.