(87f) 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

1.    Zhu, M. Z.; Aikens, C. M.; Hollander,
F. J.; Schatz, G. C.; Jin, R. C. J. Am.
Chem. Soc. 2008, 130, 5883.

2.    Qian, H. F.; Eckenhoff, W. T.; Zhu, Y.; Pintauer,
T.; Jin, R. C. J. Am. Chem. Soc. 2010, 132, 8280.