Asymmetric Electrocarboxylation Of Halide With Amino Functionalized MIL Types MOFs

The emission of CO₂ is one of the causes for global climate deterioration.On the other side,CO₂ is the most important and abundant carbon resource in nature.Reasonable use of CO₂ has become a hot research in catalysis.The method of fixing CO₂ via electroorganic synthesis has mild conditions and simple process.Electrocarboxylation of organic compounds in the CO₂ environment to produce the corresponding carboxylic acid is one of the effective methods for fixing CO₂.Although there are many reports about electrocarboxylation,few reports on asymmetric electrocarboxylation have been published.Optically active carboxylic acids,which can be obtained by asymmetric electrocarboxylation,have important applications in medical,agricultural,and fine-chemical production.Therefore,the fixation of CO₂ by asymmetric electrocarboxylation has great research significance and application prospects.Generally,metal plate electrodes are the most widely used electrodes in electrochemistry.However,electrocatalytic reaction sites for the substrates are limited due to the limitation of the geometric areas of plate electrodes.MOFs has a high specific surface area,an adjustable structure and good thermal stability.In addition,CO₂ can interact with metal ions and organic ligands in MOFs.Thus,MOFs are often used in CO₂ adsorption and conversion.Due to the affinity of amino groups for CO₂,the introduction of amino groups into the organic ligands of MOFs can further improve the capture capacity of MOFs for CO₂.MIL types have relatively high thermal and chemical stability,excellent porosity and high specific surface area,thus they can be used to catalyse molecular reactions.In recent years,MOFs have been increasingly used in asymmetric catalysis,but there are no reports of using MOFs in asymmetric electrocarboxylation.In this thesis,amino-modified MIL types MOFs with large specific surface area and excellent CO₂ adsorption performance were used as heterogeneous catalysts for CO₂ conversion to achieve asymmetric electrocarboxylation of halide.Considering the larger pore size of MOFs and their functionalization which can provide conditions for chiral inducer loading,we tried to load t-Bu?R,R?salen?Co?II??on the MIL types MOFs to obtain chiral modified materials.The chiral modified materials were further used in the asymmetric electrocarboxylation of halide.The main research contents are as follows:?1?Three amino-functionalized MIL types of MOFs,namely,MIL-101-NH₂?Cr?,MIL-101-NH₂?Al?and MIL-53-NH₂?Al?,were prepared.These three MOFs were characterized and their electrocatalytic performance were explored.It showed that the ability of MOFs to adsorb CO₂ is not only related to the specific surface area,but also to the presence of amino groups.With t-Bu?R,R?salen?Co?II??as chiral inducer,these three MOFs were used as heterogeneous catalysts for the asymmetric electrocarboxylation of?1-chloroethyl?benzene.The effects of electrolysis potentials and electrode materials on the asymmetric electrocarboxylation were investigated.The experimental results showed that these three MOFs can catalyze the asymmetric electrocarboxylation of?1-chloroethyl?benzene.Through investigation,it was found that when MIL-101-NH₂?Cr?was used as the working electrode,the yield and optical activity?ee value?of 2-phenylpropionic acid were the best.Therefore,MIL-101-NH₂?Cr?was selected as the working electrode to investigate the influence of electrolysis conditions such as the amount of catalysts,charge and temperature on the electrolysis.?2?The chiral inducer was loaded onto MIL-101-NH₂?Cr?by post synthetic modification and double solution approach to obtain t-Bu?R,R?salen?Co?II??@MIL-101-AM and t-Bu?R,R?salen?Co?II??@MIL-101-NH₂?DSA?.XRD characterization showed that chiral inducer loading did not affect the crystalline of MOFs;FT-IR,ICP and N₂ adsorption-desorption characterizations proved that t-Bu?R,R?salen?Co?II??was successfully loaded on MOFs.The chiral modified materials were applied to electrocatalysis.The experimental results showed that t-Bu?R,R?salen?Co?II??@MIL-101-AM and t-Bu?R,R?salen?Co?II??@MIL-101-NH₂?DSA?can catalyze the asymmetric electrocarboxylation of?1-bromoethyl?benzene.