Design And Synthesis Of Porous Poly(Ionic Liquid)s For Efficient Heterogenous Catalysis

Ionic liquids（ILs）have attracted considerable attention in the fields of synthesis and catalysis due to their properties of green,designability and excellent stability.However,using ILs for large-scale application in the field of industrial catalysis has been severely restricted by their high cost,high viscosity,difficult to separate and reuse catalyst.Poly（ionic liquid）s（PILs）are a kind of polyelectrolyte with polymer skeletons and repeated IL units,which not only maintain the advantages of ILs but also overcome their disadvantages.Furthermore,porous poly（ionic liquid）s（PPILs）are advanced IL functional materials prepared by introducing porous structure into PILs,which own the high specific surface area of porous materials and the characteristics of poly（ionic liquid）s,so they have been widely applied in the field of heterogeneous catalysis.In this work,two mesoporous materials were firstly prepared by either Friedel-Crafts reaction or high temperature polymerization from low-cost raw materials.Subsequent simple post-modification produced a series of mesoporous poly（ionic liquid）s.The as-obtained heterogeneous catalysts were systematically characterized by NMR,FT-IR,BET,TGA and XRD,and their catalytic performance was further investigated in green media.This study can be divided into following two parts:（1）A Pd-containing,highly-crosslinked,mesoporous poly（ionic liquid）heterogeneous catalyst（SMPIL-Pd）was prepared by hyper-crosslinking of salen-containing mesoporous poly（ionic liquid）via simple Friedel-Crafts alkylation reaction with following Pd（Ⅱ）coordination via the-N₂O₂-tetradentate ligand structure of salen.Mesoporous SMPIL-Pd possessed extremely rigid networks,predominant porosity,large specific surface area(502 m² g^-1),mesoporous structures,and highly dispersed catalytic active sites.In air atmosphere and using Et OH:H₂O=3:1（v/v）as reaction medium,SMPIL-Pd could efficiently catalyze Suzuki-Miyaura coupling reactions of various halogenated benzenes and arylboric acids with yield over 85%.In addition,hot filtration experiments and cycling experiments showed that SMPIL-Pd had outstanding stability and recyclability,and it can be reused seven cycles without a significant loss of activity.（2）A protic salt pPDA was realized by simply neutralization of p-phenylenediamine with sulfuric acid and then subjected to polymerization at 400°C under Ar atmosphere by removing small molecules（H₂O and SO₂）.The high-temperature polymerization resulted in mesoporous organic material pPDA400 with high nitrogen content.Then,mesoporous acidic poly（ionic liquid）pPDA400-[C₃N][HSO₄]was prepared by quaternization of the pPDA400 precursor with 1,3-propanesultone with subsequent acidization by concentrated H₂SO₄.The as-synthesized porous solid acid catalyst possesses large specific surface area(113 m² g^-1),ordered mesoporous structure（4.97 nm）,high acid content(1.87 mmol g^-1),and outstanding thermal stability.PPDA400-[C₃N][HSO₄]showed good catalytic performance in Prins reaction and acetal reaction.In particular,93%α-methylstyrene conversion and 97%selectivity could be obtained for Prins reaction ofα-methylstyrene and formaldehyde in water medium,which was superior to that of liquid acid H₂SO₄ and conventional solid acid catalysts（such as Amberlite IR-120（H）and Amberlyst-15）.Excellent conversion（88%）and selectivity（94%）could be maintained after running five times.