(544ax) Yolk-Shell Nanoparticle Functionalization for Heterogeneous Hydroamination
Homogeneous catalysts, despite their versatility and tunability, are near impossible to separate from solution once the reaction reaches completion. Various supported nanoparticle systems have been designed to increase ease of separation, but come at the cost of decreased catalytic capabilities. Functionalized yolk-shell nanoparticles (f-YSNPs) provide a potential solution to this problem. A functionalized yolk-shell nanoparticle consists of a thin silica âshellâ with a ligand monolayer on the surface (functionalizing the surface), containing a metal âyolkâ within the cavity. By modifying the silica surface, we have developed a novel method using f-YSNPs to catalyze reactions that otherwise require a homogeneous catalyst. The f-YSNPs are easily suspended but naturally heterogeneous, settling out of solution on sub-hour timescales. Like other silica-encased nanoparticles they are naturally aggregation resistant, maintaining high reactivity after several reuses. Using gold yolk-shell nanoparticles functionalized with aminopropyl groups, we were able to perform alkyne hydroamination, a reaction limited to homogeneous catalysis until this point. It is hypothesized the amine groups near the metal surface form a weakly covalent bond, imbuing the metal with a positive charge similar to a homogeneous gold catalyst. The products where characterized using gas chromatography, showing evidence of product formation.