Application Of Covalent Organic Framework Materials As Heterogeneous Ligands In Coupling Reactions

Covalent organic frameworks(COFs)are a new type of crystalline porous materials composed of light elements(C,O,N,B,etc.)through covalent bonds.Due to their high specific surface area,high porosity,and high crystallinity,COFs have advantages unmatched by other traditional materials.Covalent organic framework materials provide an emerging material platform for structural control and functional design,due to their highly ordered structure,chemical tunability,and porosity,as heterogeneous ligands for metal nanoparticles(NPs),forming a good heterogeneous catalyst.The advantage of supported catalysts is that they can be easily separated and recovered from the reaction mixture by simple filtration and can be reused.Therefore,immobilizing transition metal catalysts on the framework is one of the best ways to maximize product quality and reduce waste,and is very meaningful for studying various organic synthesis reactions.Based on the excellent properties of covalent organic framework materials,three different covalent organic framework materials were synthesized,which were loaded with metal ions by post-modification methods.After post-modification method to load metal ions,three kinds of covalent organic framework material catalysts were formed,namely Pd/TFPT-Azine-COF,TFPT-BZ COF/Pd,TPT-COF-Cu.By infrared spectroscopy(FT-IR),X-ray diffraction(XRD),pore size and surface area analysis(BET),scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),inductively coupled plasma emission spectrometry(ICP-OES),thermogravimetric analysis(TGA)and elemental analysis were used to characterize it,and to explore its catalytic performance for different coupling reactions.The details are as follows:In the two chapter,an azine-linked covalent organic framework(COF)with high thermal and chemical stability was prepared using a deep eutectic solvent(DES)as a green medium.The synthesized COF was used as a heterogeneous ligand to immobilize Pd ^II,and the obtained Pd modification COF nanoparticle catalyst(defined as Pd/TFPT-Azine-COF)was found to be an efficient heterogeneous catalyst for aryl halides Hirao reaction with dialkyl phosphite or diphenylphosphine oxide with excellent recyclability,reusability and crystallinity retention.In the three chapter,a covalent organic framework(COF)with high thermal and chemical stability was prepared using deep eutectic solvent(DES)as the green medium.The metal palladium was coordinated by the solvent reflux method to obtain a covalent organic framework material catalyst(defined as TFPT-BZ COF/Pd).It was used as a catalyst for the coupling reaction of substituted bromobenzene with benzothiazole,benzoxazole and thiazole,and 2-arylazole compounds were synthesized.The reaction yield was high and showed excellent catalytic performance.In the four chapter,a layered covalent organic framework(COF)based on imine bonds with high thermal and chemical stability was prepared using deep eutectic solvent(DES)as the green medium,and its specific surface area can reach 1597 m²/g.The as-synthesized COF materials were modified with copper chloride to obtain covalent organic framework material catalysts decorated with Cu sites(defined as TPT-COF-Cu).This crystalline porous catalyst exhibits excellent photocatalytic performance in the visible light-driven coupling reaction of terminal alkynes with H-phosphonates at room temperature.Furthermore,the photocatalyst can be recovered and recycled eight times without significantly reducing its reactivity.A total of eighty-three compounds were synthesized,all of which were identified by IR,¹H NMR,¹³C NMR and mass spectrometry.