About the event
Speaker: Anika Auni
Group/Host: Zhang Group
Title: Probing The Role of Zinc-Zirconium Mixed Oxide (ZnO-ZrO2) as Support in Single Atom Catalysis
Single atom (SA) catalysis, a leading field in catalytic research, excels in efficiency and minimizes metal use. The effectiveness of single atoms is linked to their dispersion on support materials. Choosing the right support is vital due to the tendency of single atoms to aggregate. Metal oxides are favored supports for their simple synthesis and versatility. However, using a single metal oxide limits dispersion and performance. Blending different metal oxides, like ZnO and ZrO2, creates more diverse binding sites and adjustable SA-support interactions.
We have synthesized various ZnO-ZrO2 compositions via co-precipitation method, forming solid solutions due to their compatible crystal structures. We have used X-ray diffraction, X-ray fluorescence, gas adsorption, and other spectrometric techniques to investigate the limits of solid solution formation allowing us to pinpoint the optimal ZnO-ZrO2 composition for SA catalysis. In one project, we anchored palladium (Pd) ions to our mixed oxide, resulting in a controlled Pd integration. The atomically dispersed states of the Pd atoms on the ZnO-ZrO2 support was confirmed by X-ray absorption. Using this ZnO-ZrO2 supported Pd catalyst (0.06 wt%) in carbon-carbon coupling (Heck) reactions, we have achieved over 99.9% conversion, high yield, and good selectivity at 85°C in an environmentally friendly ethylene glycol-water mixed solvent system. We also anchored copper (Cu) to the ZnO-ZrO2 support, using this Cu catalyst (3.4 wt%) for azide-alkyne Click reactions. Operating under eco-friendly conditions using an ethylene glycol-water mix as the solvent media, we observed >99.9% conversion with excellent yield and selectivity. Moreover, with minimal Cu leaching, this catalyst was efficiently recycled through simple centrifugation, demonstrating its robustness and reusability. In conclusion, our study presents a novel approach for controlled metal loading on supports using mixed metal oxides, demonstrating significant catalytic efficiencies in Heck and Click reactions.