Synthesis Of Ionic Porous Aromatic Frameworks And Their Applications In Gas Adsorption And Catalysis

Porous aromatic frameworks(PAFs)are an important part of porous materials.They have many advantages,such as low density,high design ability,high stability and large specific surface area.Their potential applications in molecular storage,separation,photoelectricity and catalysis have attracted extensive attention of scientists It is mainly connected by a strong C-C covalent bond,which makes it stable in harsh environments.The PAFs skeleton also has flexible functionality.This may come from the active sites in their own building units,or may be achieved through post-modified functional groupsWith the continuous development of the economy,the continuous increase of CO2 content in the atmosphere has brought about a series of serious environmental problems,such as sea level rise,extreme weather,etc.How to effectively control this problem is a major challenge facing society at present.Carbon capture and conversion methods are a potential way to reduce the CO2 content in the atmosphere.The use of suitable porous materials to convert CO2 into chemical substances while capturing CO2 will have more positive impacts on economic development.The 5-member cyclic carbonate synthesized by cycloaddition reaction of CO2 as carbon source and epoxy compound can be used as monomer of polarity fine chemical polymer and electrolyte of lithium ion battery.It is an atomic economy and effective use of CO2 way.Based on the above considerations,this paper designed and synthesized two ionic PAFs with excellent selective adsorption capacity and catalytic conversion performance for CO2:iPAF-167 and iPAF-168.The specific content is as follows:1.Choose 1,3,5-tris(4-ethynylphenyl)benzene as the building element,1,4-dibromo-2,3,5,6-tetramethylbenzene and 1,4-dibromo-2,5-bis(bromomethyl)benzene are used as the linking unit.PAF-167 and PAF-168 were synthesized by Sonogashira coupling reaction,respectively.The imidazole salt functional groups were respectively connected to the two linking unit monomers.Ionic PAFs materials: iPAF-167 and iPAF-168 were synthesized by in-situ introduction method.The characterization results from infrared spectroscopy,thermogravimetry and solid-state nuclear magnetism proved that the imidazole salt bond group has been successfully dated into the PAFs framework.By studying the gas adsorption performance of these four materials,we found that compared to PAF-167 and PAF-168,ionic PAFs have better CO2 selective adsorption performance.2.Based on the potential catalytic activity of imidazole salt functional groups,we tested the catalytic activity of iPAF-167 and iPAF-168 in the cycloaddition reaction of CO2 and epoxy compounds.In a pure CO2 gas atmosphere,iPAF-167 and iPAF-168 have high catalytic activity on different epoxy substrates.We carried out a cycle test with allyl glycidyl ether as a substrate.The results showed that both of them still had high catalytic activity after 5 cycles.We used the CO2 /N2=1:4 mixed gas as the gas atmosphere for the catalytic reaction to test the CO2 capture and conversion capabilities of iPAF-167 and iPAF-168.Under the condition of using allyl glycidyl ether as the substrate,when the mixed gas pressure is 3.0 Mpa the conversion rate of the substrate can reach more than 95%.It shows that iPAF-167 and iPAF-168 can successfully capture CO2 from the mixed gas and effectively convert it into organic carbon compounds.iPAF-167 and iPAF-168 show high CO2 capture and conversion performance.In summary,we have successfully synthesized four PAFs materials(PAF-167,PAF-168,iPAF-167 and iPAF-168),which have high specific surface area and high chemical stability.Through testing,we found that the imidazole salt functionalized iPAF-167 and iPAF-168 have excellent selective adsorption capacity for CO2.At the same time,they have high catalytic activity in the cycloaddition reaction of CO2 and epoxy compounds.In the mixed gas system,iPAF-167 and iPAF-168 can effectively achieve CO2 capture and conversion,and have good application prospects.