Gold nanoparticles embedded into imidazolium-functionalized porous aromatic frameworks as heterogenous nanoreactors for the hydrogenation of nitroaromatics

Abstract

Gold nanoparticles (AuNPs) supported by porous materials are regarded as promising heterogeneous catalysts, of which adjustable catalytic sites and recyclable merits are prerequisites for their superiority to homogeneous catalysts. The choice of support materials is a pivotal factor for controlled AuNPs size and distribution. iPAF-167 and iPAF-168 containing rich imidazolium groups are great supports, among which iPAF-168 bears a high density of imidazolium series per unit. Benefiting from their cationic frameworks and imidazolium units, Au-iPAF-167 and Au-iPAF-168 with dispersive and nano-sized AuNPs are synthesized by utilizing the synergistic effect of electrostatic and coordination interactions. Both Au-iPAFs exhibit great catalytic performance towards nitroaromatics hydrogenation with a high conversion of 99.9%. Especially, Au-iPAF-168 has a high dynamic catalytic activity with an apparent rate constant (k_app) of up to 1.9 × 10⁻² s⁻¹ for the reduction of 4-nitrophenol (4-NP) because of the higher loading content and smaller size of AuNPs.