Design,synthesis And Carbon Dioxide Capture/Conversion Of Covalent Triazine Framework

Carbon dioxide produced by humans using fossil fuels is not only the most important greenhouse gas,but also a renewable C1 resource.Carbon dioxide catalytic conversion is considered to be one of the most promising technologies for controlling carbon dioxide emissions,which is of great significance for building a green,low-carbon and recycling sustainable society.As the highest oxidation state of carbon,non-toxic and non-flammable carbon dioxide is very stable in thermodynamics and kinetics.However,the development of catalytic conversion of CO₂（organic catalysis,metal catalysis,photocatalysis,electrocatalysis and bio-catalysis）has made it possible to selectively capture and efficiently convert atmospheric CO₂ into high value-added chemicals and fuels.Various porous solid adsorbents,such as activated carbon,metal oxides,zeolites,metal-organic frameworks and porous organic polymers,have been successfully applied in the field of adsorption,separation and conversion of carbon dioxide.As an important branch of organic porous materials,the covalent triazine framework（CTF）has been widely used in the fields of carbon dioxide adsorption/separation and heterogeneous catalysis due to its high BET specific surface area,porosity,nitrogen content,physical and chemical stability,excellent carbon dioxide adsorption capacity and structural designability.In this thesis,by introducing nitrogen heterocycles,changing the polymerization temperature and adjusting the ratio of monomer to zinc chloride,two kinds of CTFs materials were successfully synthesized by ionothermal trimerization.Pyrazine-based monomer was selected as the building block to prepare CTF material,and the pore structure and nitrogen content were optimized by adjusting the reaction temperature.Then,it was applied to the adsorption and separation of carbon dioxide,and the synergistic catalysis of carbon dioxide to cyclic carbonate by CTF grafted zinc iodide was further studied.A series of CTF materials with high catalytic activity of carbon dioxide were synthesized from bibenzimidazole-based precursors and applied to the adsorption and conversion of carbon dioxide.The main research results of this thesis are as follows:1.A series of pyrazine-functionalized CTF materials（CTF-BCPP）were successfully synthesized by using 2,5-bis（4-cyanophenyl）pyrazine（BCPP）as the precursor through ionothermal trimerization reaction at different temperatures for 40 h.The effects of reaction temperature on the porosity,BET specific surface area and nitrogen content of the material were studied.CTF-BCPPs have high specific surface area(950-2031 m² g^-1)and good carbon dioxide adsorption performance.CTF-300 has the highest nitrogen content（11.23%）and the largest micropore ratio(V_micro/V_tot=0.73),which makes it has a good affinity for carbon dioxide(Q_st=36.4 k J mol^-1).CTF-300has excellent carbon dioxide capture performance(4.17 mmol g^-1)and high selective separation ratio for CO₂/N₂ mixed gas（102）at 273 K and 1 bar.At the same time,CTF-300 grafted zinc iodide showed excellent catalytic performance in the catalytic conversion of carbon dioxide to cyclic carbonate,and the highest catalytic conversion rate of CTF-300-I-1 for propylene oxide was up to 98.0%.Subsequently,the synergistic catalytic mechanism of CTF-300 and Zn I₂ was studied in depth by combining with previous reports of related work and catalytic data.2.A series of CTF materials（CTF-DCBBMs）with bibenzimidazole functional groups were successfully synthesized using 6,6’-dicyano-1H,1’H-2,2’-dibenzimidazole（DCBBM）as the building block by ionothermal trimerization.The effects of different amounts of zinc chloride on porosity,BET specific surface area,nitrogen content,and carbon dioxide adsorption and conversion performance were investigated.CTF-DCBBMS has excellent thermal stability,good microporous structure and excellent carbon dioxide adsorption performance.At the same time,CTF-DCBBM-20 showed excellent catalytic performance in the catalytic carbon dioxide cycloaddition reaction,and the maximum conversion of CTF-DCBBM-20 for epichlorohydrin reached 99.0%.The research work of this thesis has enriched the structural types of CTF materials,expanded the application of CTF materials in the field of carbon dioxide adsorption and conversion,and provided corresponding practical and theoretical references for further material synthesis and application.