DOI: 10.1002/chem.200800980
Deposition of Gold Clusters on Porous Coordination Polymers by Solid
Grinding and Their Catalytic Activity in Aerobic Oxidation of Alcohols
Tamao Ishida,[a, b] Megumi Nagaoka,[a] Tomoki Akita,[b, c] and Masatake Haruta*[a, b]
Gold has turned out to be one of the most attractive ele-
ments in catalysis research since the discovery of CO oxida-
tion at À708C over Au nanoparticles (NPs) supported on
base metal oxides.[1] During the last decade, Au NPs sup-
ported on metal oxides[2] and activated carbons (AC)[3] have
been widely studied for liquid phase reactions.[4] In liquid
phase reactions, catalytic performance of Au particles is
mainly defined by two major factors: i) the nature of sup-
ports and ii) the size of Au particles.In particular, the size
of 2 nm appears to be a critical point, where the Au particles
dramatically change their catalytic and physicochemical
properties.[5] However, the conventional deposition–precipi-
tation method is not applicable to AC due to the acidic
nature of AC.Mixing Au colloids with AC could hardly give
Au clusters with a diameter smaller than 2 nm.A latest
trend in the selection of supports is the use of organic poly-
mers.[6–8] Recently, some organic polymers were found to be
effective to stabilize colloidal Au in a cluster size, which
showed high catalytic activity for aerobic oxidation of alco-
hols at room temperature.[7] However, a constraint is that
sophisticated synthetic techniques are usually required to
obtain Au clusters.
On the other hand, porous coordination polymers (PCPs)
consisting of metal ions and organic ligands with highly reg-
ular nanometer-sized cavities or channels are an emerging
class of porous materials.[9] They are expected to be efficient
supports for metal clusters to control size and shape by
means of their cavities.[10–12] In addition, PCPs have a wide
variety of porous structures, various kinds of components,
and surface properties which would lead to tailor-made cata-
lysts for the desired reactions.Thus, investigations of the
preparation methods for PCP supported Au clusters and the
support effect of PCPs would offer a new frontier in cataly-
sis by Au.Fischer and co-workers have reported the prepa-
ration of Pd, Cu, Ru clusters, and Au NPs stabilized by Zn-
containing PCP, MOF-5 ([Zn4O(bdc)3]n (bdc=benzene-1,4-
N
dicarboxylate)[13] by chemical vapour deposition (CVD).[11]
Although Au particles could be hardly deposited in cluster
size, they were obtained as NPs in the range of 5 to 20 nm
on MOF-5 due to weak interaction.[11,12] Therefore, the gen-
eration of Au clusters that fit in and/or on the cavities of
PCPs is still a challenging research target.
Herein we report a very simple but the most effective
method for the direct deposition of Au clusters onto several
kinds of PCPs including MOF-5 by solid grinding with a vol-
atile organogold complex without using organic solvents.We
also investigated their catalytic properties for the liquid
phase alcohol oxidation with molecular oxygen.To the best
of our knowledge, catalysis of PCP supported Au clusters in
liquid phase has not yet been studied.
[a] Dr.T.Ishida, M.Nagaoka, Prof.Dr.M.Haruta
Department of Applied Chemistry
Graduate School of Urban Environmental Sciences
Tokyo Metropolitan University, 1-1 Minami-osawa
Hachioji, Tokyo 192-0397 (Japan)
Fax : (+81)42-677-2851
The PCP supports used were one-dimensionally channel-
led PCPs such as CPL-1 ([Cu
zine-2,3-dicarboxylate, pyz=pyrazine),[14] CPL-2 ([Cu2-
(pzdc)2(bpy)]n, Al-MIL53
bpy=4,4’-bipyridine),[14]
([Al(OH)
(bdc)]n)[15] with pores of 46, 68, 8.58.5 2, re-
spectively, and three-dimensional PCPs such as MOF-5 and
Cu-BTC ([Cu3
(btc)2]n (btc=benzene-1,3,5-tricarboxylate)[16]
with pores of 1515 and 1111 2, respectively.Volatile or-
ganogold complex, Me2Au(acac) (acac=acetylacetonate)
A
G
[b] Dr.T.Ishida, Dr.T.Akita, Prof.Dr.M.Haruta
Japan Science and Technology Agency (JST)
CREST, 4-1-8 Hon-cho, Kawaguchi
Saitama 322-0012 (Japan)
A
ACHTREUNG
AHCTREUNG
[c] Dr.T.Akita
AHCTREUNG
Research Institute for Ubiquitous Energy Devices
National Institute of Advanced Industrial Science
and Technology (AIST), 1-8-31 Midorigaoka
Ikeda, Osaka 563-8577 (Japan)
AHCTREUNG
and PCPs were ground in an agate mortar in air for 20 min
at room temperature.Then the mixture was treated in a
stream of 10 vol% H2 in N2 at 1208C for 2 h to obtain Au/
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8456
ꢀ 2008 Wiley-VCH Verlag GmbH & Co.KGaA, Weinheim
Chem. Eur. J. 2008, 14, 8456 – 8460