A hierarchically porous polyimide composite prepared by one-step condensation reaction inside a sponge for heterogeneous catalysis

Abstract

A compressible polyimide composite having metal binding sites was prepared by in situ polymerization inside a melamine sponge. 1,3,5-Tris(4-aminophenyl)benzene and pyromellitic dianhydride were used as a triamine and a dianhydride monomer, respectively, to construct the microporous framework, and 5-amino-1,10-phenanthroline was used as a functional monomer. The microporous polyimide containing phenanthroline groups (MPI-Phen) was obtained as insoluble powders. However, when the polymerization was carried out in the melamine sponge, MPI-Phen formed a coating layer on the sponge skeletons. The melamine sponge/microporous polyimide composite (MS/MPI-Phen) had an open cellular structure with a hierarchical porosity composed of macropores between the sponge skeletons and meso- and micropores of the MPI-Phen coating. It showed the higher compressive strength than the melamine sponge, indicating the reinforcement by the microporous polymer. The BET surface areas of MPI-Phen and MS/MPI-Phen were 723 m2g-1 and 524 m2g-1, respectively. Pd(II) ions were coordinated with the phenanthroline groups of MS/MPI-Phen for heterogeneous catalysis. The catalytic activity of MS/MPI-Phen-Pd was evaluated for the Suzuki coupling reaction between bromobenzene and phenylboronic acid.