Design And Synthesis Of Nitrogen-rich Poly(ionic Liquid)s And Its Application In Catalytic Reaction

Poly(ionic liquid)s(PILs)are polyelectrolyte materials bearing ionic liquids(ILs)species in either cationic or anionic form.Ionic liquids are polymerized through organic synthesis strategies,which can preserve the unique properties of ionic liquids themselves in the polymer backbone.In this work,we use PILs as a platform to uniformly introduce nitrogen into polymer frameworks through molecular design.Nitrogen-rich materials can significantly affect the electronic,magnetic,and optical properties of materials due to the difference in electron and electronegativity caused by the introduction of nitrogen atoms,thus playing a greater role in the field of catalysis.Using nitrobenzene hydrogenation as a template reaction,the PILs carrier capable of efficiently supporting metals was synthesized,and an efficient and recyclable metal-free catalyst was synthesized through rational molecular design.Firstly,nitrogen-rich ILs based on 1,3,5-triimidazole triazine were used to construct PILs through free radical polymerization,and supported palladium nanoparticles(Pd NPs),which were used in the catalytic hydrogenation of nitrobenzene.The resulting N-rich PILs had a good dispersion effect and ultrafine Pd NPs as shown by SEM and TEM,thereby significantly enhancing the stability of the loaded metal NPs.The XPS results indicated that the metal-support interaction improved the catalytic performance of the catalyst.In particular,the effects of different anions(Tf₂N^-,PF₆^-,and Cl^-)on the PILs were investigated,and the results showed that the Tf₂N anion exhibited the best catalytic effect on the hydrogenation of nitrobenzene.Furthermore,density functional theory(DFT)calculation confirmed that anions played a key role in activating the substrate in the hydrogenation of nitrobenzene.The corresponding results were consistent with the experimental results,which provided reference and research for the application of PILs in the future.Next,by designing imidazole-based ILs,nitrogen-rich metal-free PILs catalysts are obtained,and hypercross-linked PILs are prepared by cross-linking method.Metal-free imidazole-based nitrogen-rich PILs catalysts were synthesized.Innovative research on selective hydrogenation of nitrobenzene used ethanolamine as a hydrogen source.Using5 ml of ethanolamine as the hydrogen source,the reaction was carried out at 120°C under 1 atm N₂ atmosphere for 3 h,the nitrobenzene was completely reacted,and 65%of the hydrogenation product was aniline.While using 2 MPa H₂ as the additional hydrogen source,93%of the product was aniline.DFT calculations were also performed to explore how ILs activate ethanolamine as a hydrogen source,and a possible reaction mechanism for the selective synthesis of aniline and azobenzene by hydrogenation of nitrobenzene was proposed.In general,this paper developed supported nitrogen-rich PILs catalysts and nitrogen-rich hypercrosslinking metal-free catalysts.The supported catalysts can efficiently activate H₂ to achieve hydrogenation catalytic reaction under mild conditions,while the metal-free catalysts can effectively activate ethanolamine to achieve catalytic hydrogenation through hydrogen transfer.It provides a new method and idea for expanding the catalytic application of nitrogen-rich polymer materials.