Development of Aqueous-Phase Heterogeneous Catalyst Based on Palladium-nanoparticle Imbedded inside Silica Nanotube

Abstract

The one of the most important advantages of heterogeneous catalysis over the homogeneous counterpart is that separation of catalyst from the product phase is relatively easy and that it is unnecessary to use expensive supporting ligands. However, development of heterogeneous catalytic system for organic reactions that has comparable catalytic activity to homogeneous catalysis is a challenging issue, especially for those occurring in aqueous phase. Herein, Pd nanoparticles imbedded on silica nanotubes for heterogeneous catalysis mediating were various organic transformations in neat water, a cheap and less hazardous solvent. Pd@SNT heterogeneous catalyst prepared by selective functionalization of the inner surface of silica nanotubes with Pd nanoparticles. With the virtue of unmodified outer surface of Pd@SNTs, this heterogeneous catalytic system forms a uniform suspension in water. The catalytic performance was examined in Suzuki-Miyaura and C-H arylation reactions. An exceptionally high TON and TOF and the absence of catalyst leaching was demonstrated for Suzuki-Miyaura reaction in water. In addition, a facile modification of inner surface of Pd@SNT with APTES led to a two-fold increase in catalytic activity.