The Synthesis Of Imine Covalent Organic Frameworks And Its Catalytic Performance

Covalent Organic Framework materials(COFs)are a kind of organic porous polymers with periodic structure and crystallinity,which are constructed by covalent bonds.In this thesis,the application of imine covalent organic frameworks in heterogeneous catalysis was studied.The main contents are divided into two parts.The first part:Covalent Organic Frameworks featured unique light porous structure,and silver nanoparticles featured high efficiency in degradation of environmental pollutants.However,the field of combination of COFs with silver nanoparticles has never been reported till now.2,4,6-tris-(4-formylphenoxy)-1,3,5-triazine(TPT-CHO)and hydrazine hydrate were selected as construction units of COF material(TPHH-COF),which possesses rich nitrogen and oxygen sites.Then a new type of composite catalyst(Ag@TPHH-COF)was successfully obtained by solution infiltration.The obtained materials were also fully characterized by standard methods.Results showed that the silver nanoparticles(with diameter to be 5±3 nm)were uniformly dispersed on the surface and interlayer gap of the TPHH-COF substrate.Catalytic studies showed that Ag@TPHH-COF could catalyze the reduction of the various nitroaromatic compounds(NACs)with high efficiency,such as 4-nitrophenol,2-nitrophenol,4-nitroanilin,nitrobenzene,4-nitrotoluene and 1-butyl-4-nitrobenzene.Ag@TPHH-COF could also catalyze the reduction of organic dyes such as Rhodamine B(Rh B),Methylene Blue(MB),Methyl Orange(MO)and Congo Red(CR).Moreover,Ag@TPHH-COF has good reusability and high recovery.The second part:Porphyrin compounds have good application prospects in the field of photocatalysis because of their unique tetragonal?conjugate structure and good visible light absorption ability.We explored the application of porphyrin-COF as gas-solid photocatalytic reduction of CO₂.2,5-dibromo-1,4-benzaldehyde and 5,10,15,20-tetrakis(4-aminophenyl)porphyrin(TAPPP)were synthesized and used to synthesized Imine covalent organic framework(TAPBB).COF-366 was also synthesized by1,4-phthalaldehyde and TAPP.The conduction band of TAPBB is-0.83V,the valence band is+1.10 V and the band gap is 1.93 V.The conduction band of COF-366 is-0.88 V,the valence band is+0.86 V and the band gap is 1.74 V.By using a bottom-up strategy,the brominated modification of monomers 1,4-benzaldehyde adjusted porphyrin COF from0.86 V to 1.10 V.The ability of TAPBB and COF-366 as photocatalysts under pure water as sacrificial agent for the reduction of CO₂ to CO in gas-solid mode was studied.The yield of CO was 24.6?mol·g^-1·h^-1,which was 3 times as much as COF-366 and 1.5 times of that of g-C₃N₄ under full wavelength illumination.The yield of CO was 12.4?mol·g^-1·h^-1,which was three times higher than that of COF-366 and four times of that of g-C₃N₄ under visible light illumination.The experimental results showed that the photocatalytic activity of porphyrin COF can be enhanced by adjusting the energy band of porphyrin.