Highly selective reduction of nitroarenes with gold nano-catalysts immobilized in porous aromatic frameworks

Abstract

Abstract Gold nanoparticles (AuNPs) are highly activated nano-catalysts because of their significantly high surface-to-volume ratio. However, the agglomerative trend of NPs in the solutions causes reduced catalytic activity and inhibits their practical applications. Porous aromatic frameworks (PAFs) with high surface area and enduring stability are ideal support materials for AuNPs immobilization, and their diverse functionalized frameworks would greatly facilitate AuNPs incorporation, thus can be applied as excellent heterogeneous catalysts. By selecting triphenylphosphine and diphenyl-2-pyridylphosphine as monomers, which are the most preferential species to prepare ligand-protected AuNPs, PAF-95 and PAF-96 with high surface areas as well as uniform micropores were successfully synthesized with anhydrous FeCl3 catalysts. With the potential coordination sites of phosphine unit and pyridyl group in PAFs’ skeletons, NPs aggregation was suppressed and AuNPs were evenly dispersed in the resultant Au-PAFs. Benefiting from the high surface area of PAFs and uniform AuNPs incorporation, Au-PAFs nano-catalysts exhibited highly efficient and selective catalytic performance for the reduction of nitroarenes. Meanwhile, their valuable stability enabled good recyclability: retaining high catalytic activities after five cycles.