Preparation Of Nitrogen-Heterocyclic Carbenes Embedded In Covalent Organic Framework Materials And Research On Their Catalytic Performance

As one of the emerging frontiers in the field of chemistry and materials science,covalent organic framework materials（COF）have a wide range of applications in energy and environmental protection,biomedicine,information industry,fine chemicals,and environmental industries.Although this functionalized porous material has good application prospects,there are few research reports on COF materials in the field of catalysis.As a widely used catalyst,nitrogen heterocyclic carbene plays an important role in asymmetric catalysis,photochromism,chiral separation,molecular semiconductor and other fields.In this paper,combining the advantages of COF materials and nitrogen heterocyclic carbene,a functional covalent organic framework material containing nitrogen heterocyclic carbene ligands is designed.The palladium atom was coordinated to the COF material,and its catalytic performance was studied.The research work of this paper mainly includes the following contents:We designed a new type of COF monomer dialdehyde（TMA）as the precursor and reacted with 1,3,5-Tris（4-aminophenyl）benzene（TAPB）to obtain a functional covalent organic framework connected by imine bonds（C=N）Material COF-NHC-TAPB.Then we reacted the prepared COF material with Pd（OAc）₂to obtain a new heterogeneous catalyst Pd@COF-NHC-TAPB,which realized the application of COF material in the field of heterogeneous catalysis.Characterization by PXRD,SEM,TEM,BET,TGA and other analysis shows that the material has a certain degree of crystallinity,and the catalytically active sites of imidazole are uniformly distributed in the COF pores.Heck reaction is one of the more widely used in palladium-catalyzed C-C coupling reactions,and it is one of the methods to construct C-C bonds.When we use Pd@COF-NHC-TAPB as the catalyst,styrene and bromobenzene as the reaction substrate,and anhydrous DMF as the reaction solvent,the reaction was carried out at 110°C for 6 hours and the conversion rate reached more than 95%.Compared with COF-NHC-TAPB（yield85%）,benzo9-crown-3 azaheterocyclic carbene ligand（yield 75%）,the heterogeneous catalyst Pd@COF-NHC-TAPB has a higher High catalytic activity.Test the catalytic activity of Pd@COF-NHC-TAPB through the classic C-C coupling reaction（Suzuki-Miyayra）in this paper and compared with nitrogen heterocyclic carbene catalyst.In the reaction of phenylboronic acid and aryl halide,the The experimental results show that the best condition are ethanol,K₂CO₃,50℃,air atmosphere.The reaction is complete and the yield is high.Pd@COF-NHC-TAPB,which is a heterogeneous catalyst,did not decrease obviously in reaction activity after repeated use for 6 times.