Palladium nanoparticles encapsulated in polyimide nanofibers: An efficient and recyclable catalyst for coupling reaction

In this study, palladium‐encapsulated poly(amic acid) (Pd@PAA) nanofibers were prepared by electrospinning, followed by thermal imidization to synthesize palladium‐encapsulated polyimide (Pd@PI) nanofibers. Scanning electron microscopy (SEM) images confirmed the preparation of uniform and smooth Pd@PAA and Pd@PI nanofibers. Thermogravimetric analysis (TGA) results reveal that the Pd@PI nanofibers possessed excellent thermal stability. The dispersion of palladium nanoparticles in the polyimide nanofibers was characterized by transmission electron microscopy (TEM) and X‐ray diffraction (XRD). The catalysis results show that this Pd@PI fibrous catalyst was very efficient to catalyze the cross‐coupling reactions of aromatic iodides with n‐butyl acrylate (Heck reaction) or phenylboronic acid derivatives (Suzuki reaction) to afford the desired products in good to excellent yields. Moreover, the Pd@PI catalyst could be easily separated and recovered from the reaction mixture by simple filtration due to the regular fibrous structure and reused for 10 times for both Heck and Suzuki reactions without obvious loss of its initial catalytic activity. Thus, the Pd@PI nanofiber catalyst holds great potential in chemical industry in terms of its excellent catalytic activity and stability. Ultrasmall palladium nanoparticles stabilized by polyimide nanofibers were readily prepared by electrospinning and thermal imidization. These composite nanofibers possessed superior thermal property and chemical resistance as well as mechanical properties. Moreover, the palladium nanoparticles inside the nanofibers exhibited excellent catalytic activity and stability for the Heck and Suzuki coupling reactions. Due to fibrous structure, these composite nanofibers could be easily separated from the reaction mixture and reused for 10 times.