CNT Covalently Grafted N-Heterocyclic Carbene Silver,Copper Catalyzed CO₂ Cured

In the last several decades,CO₂ emission has caused a lot of environmental problems.To mitigate the concentration of CO₂ in the atmosphere,various strategies have been implemented,one of which is the use of N-heterocyclic carbenes（NHCs）and related complexes to accomplish the capture,fixation,and activation of CO₂ effectively.In this review,we summarize CO₂ capture,fixation,and activation by utilizing NHCs and related complexes;homogeneous reactions and their reaction mechanisms are discussed.Free NHCs and NHC salts can capture CO₂ in both direct and indirect ways to form imidazolium carboxylates,and they can also catalyze the reaction of aromatic aldehydes with CO₂ to form carboxylic acids and derivatives.Moreover,associated with transition metals（TMs）,NHCs can form NHC-TM complexes to transform CO₂ into industrial acid or esters.Non-metal-NHC complexes can also catalyze the reactions of silicon and boron complexes with CO₂ .In addition,catalytic cycloaddition of epoxides with CO₂ is another effective function of NHC complexes,and NHC ionic liquids perform excellently in this aspect.Carbon nanotubes（CNTs）are currently a new type of high strength carbon fiber material,not only has the unique properties of carbon materials,but also with the thermal conductivity and conductivity of metal materials,textile fiber weaving,ceramic corrosion resistance and heat resistance,As well as the light and easy processing of polymer materials.Carbon nanotubes as a composite can show good strength,elasticity,fatigue resistance,can predict the participation of carbon nanotubes will bring an unprecedented leap in the performance of composite materials.The graphene has a two-dimensional atomic crystal structure formed by the tight accumulation of sp² carbon atoms.It has been widely used in high performance nanoelectronic devices,gas sensors,field emission due to its excellent surface area,good electrical conductivity and excellent mechanical properties.Materials,composites,imaging technology and communications technology.In this paper,the synthesis of N-heterocyclic carbene and carbene copper onto MWCNs or reductive graphene（RGO）is carried out by utilizing the stability and excellent conductivity of the carrier CNT and RGO.The catalytic activity and recovery catalyst were obtained,and the four kinds of chemical reactions were tried by using the catalyst.The catalyst was characterized by such as BET,XPS,ICP-AES,SEM and TEM catalyst of the reactivity,etc.The synthesis is divided into five parts.（1）The effects of CNT-NHC-Ag and CNT-NHC-Cu on the effect of 2-methyl-3-butyn-2-ol and CO₂ curing reaction（catalyst concentration,reaction temperature,reaction pressure,reaction time）The reaction trend of the reaction,and then explain why the reason for this situation to explain or argue;Finally,the effect of electron effect and steric hindrance on the reaction of propargyl alcohol and the catalytic reaction of four catalysts were explained.（2）Using CNT-NHC-Ag and CNT-NHC-Cu to participate in the coupling reaction of alkynol and O₂,and adding Cu I as a control experiment to verify the reaction mechanism of propargyl alcohol and CO₂ to exclude other mechanism interference.（3）The effect of co-catalyst on its catalyst was investigated by the reaction of co-catalyst,co-catalyst,soluble silver salt,CNT-NHC-Ag and CNT-NHC-Cu catalyzed by propylene oxide and CO₂ .And then through the substrate expansion to explore the steric effect and electronic effects on its impact.（4）CNT-NHC-Ag,CNT-NHC-Cu,GN-NHC-Ag,GN-NHC-Cu catalysts catalyze the amination of 2-methyl-3-butyn-2-ol,CO₂ and organic amines（primary and secondary amines）and by expanding the substrate,blank control,and finally by expanding the silver salt and copper salt to illustrate the general mechanism of the experiment.（5）The use of catalyst ICP-AES to illustrate the metal loading,BET to explain the catalyst specific surface area,particle size distribution,etc,by SEM,TEM to explain whether the catalyst is well loaded and uniform degree,XPS characterization can accurately describe the specific metal load and the surface metal content,the catalyst recovery experiment can roughly explain the catalyst life.