Controlling the Selectivity of Styrene Oxidation Catalyzed by Atomically Precise Aun Nanoclusters

Controlling the Selectivity of Styrene Oxidation Catalyzed by Atomically Precise Au_n Nanoclusters

Yan Zhu^1,2*, and Yuhan Sun¹

¹Shanghai Advanced Research Institute, Chinese Acadamy of Sciences, Shanghai , China;

²Department of Chemistry, Carnegie Mellon Univeristy, Pittsburgh, USA

E-mail: zhuy@sari.ac.cn

The major limitations of conventional nanocatalysts, such as the inherent size polydispersity and precise size control at the atomic level, preclude fundamental investigations on the precise structure-catalytic activity relationships. Therefore, it is of paramount importance to attain atomically precise metal nanoparticles and use such nanoparticles as well-defined catalysts. By solving their atomic structure of the nanoclusters, one will be able to precisely correlate the catalytic properties with the exact atomic structure of the nanoclusters and to learn what control the surface activation, surface active site structure and catalytic mechanism. By learning these fundamental principles, one will ultimately be able to design new types of highly active and highly selective nanocatalysts for a variety of catalytic processes.

Au_n (n=number of gold atom in cluster are ideally composed of an exact number of gold atoms, e.g., n ranging from a dozen to hundreds) nanoclusters demonstrate the huge power of atomically precise Au_n nanoclusters for achieving super catalytic performance and atomically precise structure-property relationships, and achieving the controllable obtainment of the desired products in uncertain catalytic processes. Au_n nanoclusters are utilized to catalyze the partial oxidation of styrene as an example. The partial oxidation of styrene typically produces benzaldehyde and epoxide as major products. Herein, we found a strategy for controlling the catalytic selectivity by exploring the kinetic factor and the promotion effect of acetonitrile. High selectivity for benzaldeyde (~100%) under one set of conditions and for epoxide (>95%) under the other set of conditions has been respectively attained by tuning the site-specific catalytic properties of gold nanoclusters. Our present study not only provides new opportunities for unraveling gold nanocatalysis at the atomic level, but also benefit the future design of new catalysts for certain chemical processes to obtain the desired products with high selectivity.

Figure. The geometric structure of Au₂₅S₁₈ (the CH₂CH₂Ph moiety is omitted for clarity); (B) ball model; (C) electronic structures of Au₂₅S₁₈ nanoclusters. Color labels: pink for Au₁₃ core atoms, blue for Au₁₂ shell atoms, yellow for S.

Scheme. Proposed mechanism for the epoxidation of styrene catalyzed by Au₂₅ nanoclusters with TBHP as oxidant and CH₃CN as a promoter. (Magenta: Au₁₃ core atoms, Cyan: Au₁₂ shell atoms, the thiolate ligands are omitted for clarity.)

Acknowledgements

We thank financial support from CMU and SARI.

References

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