Heterogeneous Nanocatalysts

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Invention Summary: The use of metal nanopar­ticles (MNPs) in catalysis has rapidly increased in recent years because of their efficient and intrinsic size dependent catalytic properties as well as their ability to catalyze a range of chemical reactions. For many MNPs to catalyze reactions and result in efficient catalysis, the reacting substrates must directly interact with the metal surface. This metal-substrate interaction could be greater if the MNPs were synthesized “naked”. Unfortunately, atoms of a “naked” MNP have a greater tendency to aggregate into a bulk material due to their high surface energies and lose their intrinsic catalytic activities.  This is often responsible for the decrease in, or loss of catalytic activity and selectivity over time of many MNP catalysts. In particular, Pd nanoparticles (PdNPs), which are known for their catalytic activities, can easily aggregate to form Pd-black because Pd has among the highest surface energies of metals.  Although the degree of aggregation of PdNPs or other MNP catalysts can be overcome or mini­mized by passivating the metal’s surface with organic ligands, this too will unfortunately be accompanied by the loss of catalytic activity. Rutgers researchers have developed a new method that al­lows the synthesis of novel nanostructured catalysts composed of silica-dendrimer core-shell nanostructures. The dendrimer shells further contain metallic and metal oxide nanoparticles that are active catalysts.  Because the metallic nanoparticles are encapsulated within the dendrimer shell, they have much lower tendency to aggregate or sinter and maintain their inherent catalytic activities, even after multiple recycling. Furthermore, because the metallic nanoparticles or dendrimer shells are on the external surface of the core-shell nanospheres, these metallic nanoparticles are exposed to reactant and, hence, show enhanced catalytic activities. Their recyclable catalytic activities have been demonstrated with two of the most com­monly used chemical transformations in chemical and phar­maceutical industries, hydrogenation and C-C bond coupling reactions. The performance of the catalysts is much better in terms of efficiency, selectivity as well as recyclability compared to commercially used Pd/C catalyst based on comparison of catalytic turn-over-numbers (TONs) and turn-over-frequen­cies (TOFs).   Market Application: Pharmaceuticals and Industrial Chemical Production.   Advantages: • Easily recyclable catalyst for hydrogenation of various olefins, alkynes, keto and nitro groups • ~100 % conversion and high turn-over-numbers (TONs) under 10 bar H2 pressure and room temperature • Recycled up to five cycles without significant loss of their catalytic activity and selectivity