Synthesis And Properties Of Porous Aromatic Framework Immobilized Pd-based Organometallic Catalysts

Porous aromatic frameworks?PAFs?are formed by aromatic rings through stable covalent bonds.PAFs not only have very high surface area,porosity,but also have high thermal,physical and chemical stability.Furthermore,they have adjustable pores and structures.In the past decade,PAFs are widely concerned by scientists because of these excellent properties.PAFs exhibit wide application prospects in the fields of gas storage and separation,sensing,and heterogeneous catalysis.However,the study of PAFs in the field of organometallic catalysis is still in the initial stage so far.In this paper,some PAFs?PAF-45,PAF70-NH₂ and PAF-1?were used to immobilize Pd-based organometallic catalysts by post-modifications and the catalytic properties of the obtained immobilized catalysts were studied systematically.In the first part of this paper,we choose PAF-45 which was developed by our group before as the platform.PAF-45 with micropores was synthesized through the Scholl reaction of biphenyl catalyzed by anhydrous aluminum chloride in trichloromethane.Then through nitration,reduction,schiff base reaction of PAF-45,PAF45-N=CPy with N,N-bidentate ligand was obtained.Finally,after reaction with palladium acetate,Pd-based organometallic catalyst PAF45-Pd was obtained.Then we studied the catalytic properties of PAF45-Pd for catalyzing the Suzuki�Miyaura coupling reaction and Heck reaction.The experimental results showed that PAF45-Pd catalyst has a good catalytic activity.In the second part of this paper,we select PAF70-NH₂ reported by our group recently as the platform.PAF70-NH₂ with mesopores is synthesized through the literature step reported by our group.After two-step modifications of PAF70-NH₂ the Pd-based organometallic catalyst which is named PAF70-Pd was successfully synthesized.Because PAF70-NH₂ containing mesoporous?3.8 nm?can afford large enough pore space,PAF70-Pd has very high Pd content?23.0 wt%?.We then studied the catalytic performance of PAF70-Pd for catalyzing Suzuki�Miyaura coupling reaction and Heck reaction.It was found that PAF70-Pd has high activity for the above reactions.Compared with the traditional organic porous material immobilized Pd catalysts,PAF70-Pd has the highest Pd content and exhibits far higher TOF value when catalyzing the same Suzuki-Miyaura coupling reaction.Moreover,PAF70-Pd is easy to be recoverd and reused in catalyzing the Suzuki-Miyaura coupling reaction.Using PAFs as platforms to immobilize organometallic catalysts by post-modifications expands the application range of PAFs.Because of their stability and high catalytic activity as well as easy recyclability,PAF-immobilized organometallic catalysts show great application potential in the chemical industry and pharmaceutical industry.