Synthesis Of Triphenylimidazolium Iodide-containing Porous Organic Polymers And Their Application In CO₂ Cycloaddition

Cycloaddition reaction of CO₂ and epoxides is one of the most important CO₂conversion reactions,which is featured by the high atomic efficiency(100%)and the wide application of cyclic carbonate products.However,such a cycloaddition reaction usually requires the use of highly efficient catalysts due to the inherently chemical inertness of CO₂.In this thesis,four types of triarylimidazole-containing porous organic polymers(namely,PTPI,PBPI,PFBI and PMBI)were prepared by separately polycondensation of 1,2,4,5-benzenetetraamine with 4,4',4''-(1-butyl-1H-imidazole-2,4,5-triyl)tribenzaldehyde(TPI),4,4',4'',4'''-(1,4-phenylenebis(1-butyl-1 H-imidazole-2,4,5-triyl))tetrabenzaldehyde(BPI),4,4'-(1-butyl-2-(8-formyl-6H,12H-5,11-meth-anodibenzo[b,f][1,5]diazocin-2-yl)-1H-imidazole-4,5-diyl)dibenzaldehyde(FBI)and4,4',4'',4'''-((6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine-2,8-diyl)-bis(1-butyl-1H-imidazole-2,4,5-tri-yl))tetrabenzaldehyde(MBI).The as-synthesized four porous organic polymers all have both high specific surface areas(S_BET)and relatively high CO₂adsorption capacities.Subsequently,triphenylimidazolium-containing porous organic polymers,namely PBPI-IL and PMBI-IL,were synthesized by post-treatment of PBPI and PMPI with methyl iodide.Owing to the H-bonding interaction between epoxides and benzbisimidazole ring,the?-?bonding interactions between benzbisimidazole rings and CO₂molecules,and the high nucleophilicity of I^-anion,both PBPI-IL and PMBI-IL are capable of efficiently catalyzing the cycloaddition of CO₂to epoxides.In addition,the as-synthesized heterogeneous catalysts also have characteristics of easy recovery and good recyclability.The main research contents of this thesis are as follows:(1)Synthesis of triphenylimidazolium iodide-containing pore organic polymers and their application in CO₂cycloaddition.In this chapter,two monomers,TPI and BPI,were synthesized via the protection,benzoin condensation,Debus-Radziszewski reaction,alkylation,and de-protection by using terephthalaldehyde as the starting material.Subsequently,porous organic polymers,namely PBPI and PTPI,were separately synthesized by polycondensation of 1,2,4,5-benzenetetraamine tetrahydrochloride with BPI and TPI.The specific surface areas(S_BET)of PBPI and PTPI are found to be 575 m²g^-1and 480 m²g^-1,respectively,while the CO₂adsorption capacities of PBPI and PTPI are around 2.64 mmol g^-1and 2.48 mmol g^-1,respectively,at 273 K/1 bar.Based on PBPI,triphenylimidazolium iodide-containing porous organic polymers with different degrees of ionization,namely PBPI-IL1,PBPI-IL2 and PBPI-IL3,were synthesized by post-treatment of PBPI with methyl iodide under different conditions.The as-synthesized PBPI-IL2 with an ionization degree of around 31.94 mol%exhibited a specific surface area(S_BET)of 350 m²g^-1and a CO₂adsorption capacity of 1.88 mmol g^-1.As such,the PBPI-IL2 showed highly catalytic activity for the cycloaddition of CO₂to epoxides,for example,the conversion and selectivity could be as high as 96%and 99%,respectively,for cyclohexene oxide in the absence of co-catalyst.(2)Synthesis of triphenylimidazolium/tr(?)ger's base iodide-containing POPs and their application in CO₂cycloaddition.By use of the above-synthesized 1,2-bis(4-(1,3-dithiolan-2-yl)phenyl)ethane-1,2-dione and newly synthesized 6,12-dihydro-5,11-methanodibenzo[b,f][1,5]diazocine-2,8-dicarbaldehyde,two monomers,FBI and MBI,were synthesized through Debus-Radziszewski reaction,alkylation,and deprotection.In a similar way,porous organic polymers,PFBI and PMBI,were separately prepared by polycondensation of 1,2,4,5-benzenetetraamine tetrahydrochloride with FBI and MBI.The specific surface areas(S_BET)of PFBI and PMBI are determined to be 441 m²g^-1and431 m²g^-1,respectively,whereas the CO₂uptake capacities of PFBI and PMBI are around 2.27 mmol g^-1and 2.59 mmol g^-1,respectively,at 273 K/1 bar.Then the triphenylimidazolium/tr(?)ger's base iodide-containing POP with an ionization degree of around 65.92 mol%,PMBI-IL,was synthesized by post-treatment of PMBI with CH₃I.The as-synthesized PMBI-IL with a specific surface area(S_BET)of 108 m²g^-1and a CO₂adsorption capacity of 1.47 mmol g^-1also showed highly catalytic activity for the cycloaddition of CO₂ to epoxides.