Heterogeneous Catalysis of Molecular‐Like Au8M(PPh3)8 Clusters Cultivated in Mesoporous SBA‐15

Abstract

It is a dream of researchers to be able to tailor the catalytic performances by adjusting heterogeneous catalysts at the atomic level. Atomically precise metal clusters provide us with the possibility to achieve this challenge. Here, we design a push‐and‐pull synthesis strategy coupled with TiOx coating to prepare the heterogeneous catalysts denoted as TiOx/Au8M@SBA via cultivating atomically precise Au8M(PPh3)8ⁿ⁺ (M=Pd, Pt or Au; n=2 for Pd/Pt and 3 for Au) clusters in mesoporous molecular sieve. The catalysts are made up of the three functional units, which include Au8M(PPh3)8ⁿ⁺ clusters that can act as the active sites, the pore environment of the SBA‐15 that can announce a catalysis show for the clusters with precise number of atoms maintained during the chemical reactions, and the TiOx coating that can further inhibit the migration of the clusters under reaction conditions. The selective hydrogenation of acetylene performed in the fixed‐bed reactor taken, for example, we learn how the atom‐by‐atom tailoring of a heterogeneous catalyst can switch on elusive heterogeneous mechanisms with cluster catalysis. This work sheds light on the fundamental insight into catalysis origin of heterogeneous catalysts and achieves a distinguished level of detail for cluster catalysis.

Full text

Heterogeneous Catalysis Very Important Paper
Heterogeneous Catalysis of Molecular-Like Au8M(PPh3)8
n+Clusters
Cultivated in Mesoporous SBA-15
Tianqi Sun+, Bingqing Ge+, Shuangshuang Huang, Xiuwen Wang, Yiqi Tian, Xiao Cai,
Weiping Ding, and Yan Zhu*
Abstract: It is a dream of researchers to be able to tailor
the catalytic performances by adjusting heterogeneous
catalysts at the atomic level. Atomically precise metal
clusters provide us with the possibility to achieve this
challenge. Here, we design a push-and-pull synthesis
strategy coupled with TiOxcoating to prepare the
heterogeneous catalysts denoted as TiOx/Au8M@SBA
via cultivating atomically precise Au8M(PPh3)8
n+(M=
Pd, Pt or Au; n=2 for Pd/Pt and 3 for Au) clusters in
mesoporous molecular sieve. The catalysts are made up
of the three functional units, which include Au8M-
(PPh3)8
n+clusters that can act as the active sites, the
pore environment of the SBA-15 that can announce a
catalysis show for the clusters with precise number of
atoms maintained during the chemical reactions, and the
TiOxcoating that can further inhibit the migration of the
clusters under reaction conditions. The selective hydro-
genation of acetylene performed in the fixed-bed reactor
taken, for example, we learn how the atom-by-atom
tailoring of a heterogeneous catalyst can switch on
elusive heterogeneous mechanisms with cluster catalysis.
This work sheds light on the fundamental insight into
catalysis origin of heterogeneous catalysts and achieves
a distinguished level of detail for cluster catalysis.
Introduction
Catalysis involving heterogeneous and homogeneous cata-
lysts is of considerable interest for both fundamental
research and application development. Homogeneous cata-
lysts always exhibit the defined molecular structures, there-
by the catalytic active sites being identified and the
structure–property relationship being established.[1–3] Espe-
cially, the catalytic performances of homogeneous catalysts
can be feasibly tuned by atomic-level tailoring of specific
groups in the molecular catalysts without changing other
bonds and compositions.[4,5] For heterogeneous catalysts, it is
extremely difficult to realize the precise tailoring of particle
structure and functionality in the catalysts at an atomic level,
as the conventional particle catalysts show the structural
polydispersity and heterogeneity, which can preclude funda-
mental investigations on the precise structure-catalytic
activity relationships.[6–8] Although significant efforts have
been invested in preparing well-defined heterogeneous
catalysts, fundamental catalysis researches still significantly
lag behind and thereby an in-depth understanding of the
structure-dependence origin and the identification of the
catalytical active sites in particle catalysts remain elusive.
Therefore, it is of paramount importance to attain
atomically precise heterogeneous catalysts, by solving their
precise formulas and total structures, which can become
possible to pinpoint the active sites and tailor the active
structures, akin to the homogeneous molecular catalysts.
Atomically precise metal clusters with crystallographic
structures are composed of an exact number of metal atoms
ranging from a dozen to hundreds.[9–11] Their total structures
can be solved by single crystal X-ray analysis and they
behave like molecules.[12–16] On the basis of their atom-
packing structures, these clusters can permit a precise
correlation of particle structure with catalytic properties and
also allow for identification of active sites on the
particle.[17–21] More notably, an atom-by-atom tailoring can
be achieved on the clusters, for example, adding or deleting
one metal atom and single-atom substitution.[22–26] Such
tailored cluster catalyst provide opportunities to learn how
different sites or even different atoms in the catalyst
contribute to its overall catalytic property that would not be
observable with conversional heterogeneous catalysts, since
almost all of the current studies give rise to an ensemble
average of the catalytic performance.[27–31]
Herein, we design the heterogeneous catalysts denoted
as TiOx/Au8M@SBA that can be viewed as the Au8M-
(PPh3)8
n+clusters capped by SBA-15 and TiOx, and thereby
these precise clusters can show unique catalysis on the
performance stage built by the surrounding environment of
SBA-15 and TiOx. It is found that, for the selective hydro-
genation of acetylene carried out in the fixed-bed reactor,
the TiOx/Au8Pt@SBA catalyst has little activity and TiOx/
Au9@SBA catalyst shows structural lability, while the TiOx/
Au8Pd@SBA catalyst exhibits an excellent performance. A
[*] T. Sun,+Dr. B. Ge,+Y. Tian, X. Cai, Prof. W. Ding, Prof. Y. Zhu
School of Chemistry and Chemical Engineering, Nanjing University
Nanjing 210093, China
E-mail: zhuyan@nju.edu.cn
Dr. S. Huang
School of Physics and Technology, Wuhan University
Wuhan 430072, China
Dr. X. Wang
Center for Microscopy and Analysis, Nanjing University of
Aeronautics and Astronautics
Nanjing 211106, China
[+] These authors contributed equally to this work.
Angewandte
Chemie
Research Article www.angewandte.org
How to cite: Angew. Chem. Int. Ed. 2024, e202420274
doi.org/10.1002/anie.202420274
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