Synthesis Of Functional Porous Organic Frameworks And Their Applications In Gases Adsorption And Separation

With the fast development of the economy,human are increasingly demanding for energy,such as high-quality energy raw materials,C2H6 and C2H4.However,there are also serious environmental problems needing great attentions,for examples,excessive emission of greenhouse gases such as CO2 induces global warming.In order to better solve energy and environmental problems,researchers have done extensive researches on this,in which the adsorption and separation of target gases by porous materials is regarded as an effective method.As a member of the porous materials,porous organic frameworks?POFs?have many advantages,such as high surface area,lower skeleton density and high stability.Because of the diversity of synthetic pathways,POFs can be targeted synthesized by adjusting the length and types of the monomers.Functional POFs can also be obtained by functionalization of bare materials,which includes post modification and in situ synthesis.The latter method is better than the former,since the functional groups introduced in the frameworks would disperse more uniformly by in situ synthesis way.In this thesis,we synthesized two kinds of functional POFs,PAF-73-V_x%and PAF-74-NH₂,and study their applications in gases adsorption and separation.Firstly,we selected the monomer 2,5-divinyl-p-benzaldehyde and terephthaldehyde without vinyl functional groups.By adjusting their mole rations adding in the polymerization and aggregating with tetra-?4-anilyl?-methane,we obtained PAF-73-V_x%containing different proportions of vinyl groups.The successful synthesis was proved by a series of basic characterizations.Nitrogen adsorption results show PAF-73-V_x%have high surface areas and the surface areas of the material decreased with the introduction of vinyl.We tested the adsorptions of C2H6 and C2H4 and the results show that with the increasing in the content of vinyl in the polymer,the adsorption of C2H6 and C2H4 is also increased.This indicates that the vinyl functional group can enhance the adsorptions amount of C2H6 and C2H4.Secondly,we selected the monomers 1,3,5-tris?4-ethynylphenyl?benzene and4,4'-Dibromobiphenyl,1,1'-biphenyl-2-amine to react via Sonogashira-Hagihara reaction to obtain the POF materials PAF-74-NH2 and PAF-74,in which the amino functional group retains perfectly.According to the Brunauer–Emmett–Teller?BET?model,PAF-74-NH2 and PAF-74 present high surface areas of 918 and 1230 m²/g,pores of 1.31 and 1.72 nm,respectively.Besides,they have high thermal and chemical stability.We tested the adsorption abilities of CO2 and N2,finding that PAF-74-NH2 and PAF-74 have different adsorption amounts for them and PAF-74-NH2 has better ability of separation for CO2/N2 than PAF-74.And PAF-74-NH₂ also has high selectivity in the separation of CO₂/CH₄.The above results indicate that the introduction of amino functional group into the porous organic framework material can provide a functionalized porous material with a good carbon dioxide separation effect.In summary,we synthesized two kinds of functional POFs,PAF-73-Vx%and PAF-74-NH2,which are synthesized by using in situ synthesis method,and the characterizations proved that the vinyl functional group of PAF-73-V_x%can enhance the adsorption capacity of C2H6 and C2H4 and PAF-74-NH2 with amino functional groups has certain selectivity for CO₂/N₂ and CO₂/CH₄.