3D open-framework vanadoborate as a highly effective heterogeneous pre-catalyst for the oxidation of alkylbenzenes

Article abstract of DOI:10.1021/cm401400m

Three three-dimensional (3D) open-framework vanadoborates, denoted as SUT-6-Zn, SUT-6-Mn, and SUT-6-Ni, were synthesized using diethylenetriamine as a template. SUT-6-Zn, SUT-6-Mn, and SUT-6-Ni are isostructural and built from (VO)₁₂O₆

Full text of DOI:10.1021/cm401400m

Article
pubs.acs.org/cm
3
D Open-Framework Vanadoborate as a Highly Effective
Heterogeneous Pre-catalyst for the Oxidation of Alkylbenzenes
Hong Chen,†,‡ Youqian Deng, Zhengbao Yu, Huishuang Zhao, Qingxia Yao, Xiaodong Zou,
Jan-E. Backvall,* and Junliang Sun*
̈
§
∥
†
†
†
,
§
,†,∥
†
‡
§
Department of Materials and Environmental Chemistry, Stockholm University, SE-106 91 Stockholm, Sweden
Faculty of Material Science and Chemistry, China University of Geosciences, 430074 Wuhan, China
Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
∥College of Chemistry and Molecular Engineering, Peking University, 100871 Beijing, China
*
S Supporting Information
ABSTRACT: Three three-dimensional (3D) open-framework vanadoborates, denoted as SUT-6-Zn, SUT-6-Mn, and SUT-6-
Ni, were synthesized using diethylenetriamine as a template. SUT-6-Zn, SUT-6-Mn, and SUT-6-Ni are isostructural and built
from (VO) O B O (OH) clusters bridged by ZnO , MnO , and NiO polyhedra, respectively, to form the 3D frameworks.
12
6
18 36
6
5
6
6
SUT-6 is the first vanadoborate with a 3D framework. The framework follows a semiregular hxg net topology with a 2-fold
interpenetrated diamond-like channel system. The amount of template used in the synthesis played an important role in the
dimensionality of the resulting vanadoborate structures. A small amount of diethylenetriamine led to the formation of this first
3
D vanadoborate framework, while an increased amount of diethylenetriamine resulted in vanadoborates with zero-dimensional
(
0D) and one-dimensional (1D) structures. SUT-6-Zn was proved to be an efficient heterogeneous precatalyst for the oxidation
of alkylbenzenes.
KEYWORDS: vanadoborates, open-framework materials, hxg topology, heterogeneous catalysis, oxidation
INTRODUCTION
states of vanadium ions (+3, +4, or +5) could also provide
interesting catalytic or magnetic properties.
■
Inorganic microporous materials such as silicates, borates,
phosphates, and germanates attracted great interest during the
past decades due to their industry applications in catalysis,
adsorption, and separation.
like B, Al, Si, Ge, P are typical elements frequently used in
constructing this kind of material. Recently, transition metals,
such as zinc, titanium, nickel, etc., were introduced to
synthesize new microporous materials for different catalytic
applications. Vanadium, one of the most studied elements for
catalytic applications, has also been used to synthesize inorganic
Ever since 1998, when Rijssenbeek reported the first
13
vanadoborate clusters, a great number of vanadoborate
3− 14
clusters such as V6B in [(VO) {B O (OH) } ] , V6B
1
−5
20
6
10 16
6
2
22
Group III, IV, and V elements
8− 15
in [V B O (OH) ]
,
V B
in [Mn (C O )-
6
22 44
10
10 28 4 2 4
1 0 − 1 6
(
{
{
[
V 1 0 B 2 8 O 7 4 H ) ]
,
V 1 2 B 1 6 i n [ ( V O ) 1 2 O 4
8
8−
1
7
B O (OH) } ] , V B in [(VO) O {B O (OH) }
8
17
4
2
12 17
12
4
8
17
4
in
6
,7
8
−
B O (OH) (H NCH CH NH )}] , V1 2
B
1 8
18,19
9
1 8
4
2
2
2
3
1
0− 13
(VO) O {B O (OH)} ]
,
and V B
in
1
2
6
3
6
6
12 32
1
2−
([(VO) {B O (OH) } ] ) have been reported. Compared
12
16 32
4 2
with vanadogermanates or vandosilicates, where all cage-like
8
microporous materials such as vanadogermanates, vanadosili-
clusters can be derived from the V O cluster by replacing n
18
42
9
,10
11
cate,
and vanadophosphates, which show enhanced
VO square pyramids with n Ge O or Si O groups (n =
5 2 7 2 7
8
12
catalytic or magnetic properties. As the vanadium compounds
show similar bond lengths and coordination environment as
germanium, using vanadium to replace those traditional
elements for constructing inorganic microporous materials
seems very promising. In addition, various types of valence
2,3,4), vanadium polyhedra and boron species are much more
Received: April 28, 2013
Revised: November 27, 2013
Published: December 9, 2013
©
2013 American Chemical Society
5031
dx.doi.org/10.1021/cm401400m | Chem. Mater. 2013, 25, 5031−5036

Chemistry of Materials
Article
flexible in constructing different types of vanadoborate clusters.
Other Characterizations. The composition of the as-synthesized
SUT-6-Zn was determined by CHN elemental analysis and inductively
coupled plasma (ICP) analysis. Thermogravimetric (TG) analysis was
conducted using a Perkin-Elmer TGA7 on SUT-6-Zn under nitrogen
atmosphere in a platinum crucible between 20 and 800 °C at a heating
16
Other kinds of transition metals, transition metal com-
2
0,21
22,21
plexes,
or even organic groups
can be incorporated into
the cluster to enhance the diversity of the vanadoborate
clusters. For instance, when the Zn (μ-B O H ) group was
−1
4
2
4
2
rate of 10 °C min . An in-situ PXRD experiment was performed on
incorporated into the V B cyclic bend, a new type of
1
0
28
an X’Pert PANalytical Pro MRD using Cu Kα radiation (λ = 1.5418 Å)
and variable divergent slits. The sample was heated in an Anton-Parr
XRK900 reaction chamber. The chamber was equilibrated for 2 min
prior to each data collection. The samples were heated in air from 30
1
6
Zn V B
cluster was obtained. Interestingly, while a large
4
10 30
number of different types of three-dimensional (3D)
vanadogermanate or vanadosilicate frameworks were re-
8
,9
−1
ported,
typical vanadoborates only have lots of lower
to 500 °C with a heating rate of 7 °C min . PXRD patterns were first
recorded at room temperature and 50 °C, then up to 300 °C with an
increment of 50 °C, and finally to 500 °C with an increment of 100
°C. Room temperature PXRD used for phase confirmation was also
collected on the same diffractometer with a silicon holder. UV−vis-
NIR Spectroscopy data were acquired from a single crystal of SUT-6-
Zn using a Craic Technologies microspectrometer. The crystal was
placed on quartz slides under Krytox oil, and the data were collected
from 200 to 1600 nm. The topology of SUT-6 was determined from
dimensional structures, such as one-dimensional (1D) cluster
chain and two-dimensional (2D) net structures. Ian D.
2
3
Williams et al. claimed 3D microporous vanadoborates a
decade ago, but there were no details about the structure.
24
Recently Zhou et al. reported the first dense 3D vanadoborate
in which all V B clusters are connected by the 3D Na−O−
12 18
Na network forming a dense structure. However, the Na−O
bonds are ionic bonds, and no porosity was observed.
Compared with other borates or vanadium-incorporated
cluster-based materials where 3D open-frameworks have been
widely studied, no 3D open-framework vanadoborate has been
reported until now. Here, we synthesized a 3D open-framework
vanadoborate, SUT-6 with diethylenetriamines as templates,
and Zn, Ni, and Mn polyhedra as linkers. SUT-6-Zn was proved
to be an effective heterogeneous oxidation precatalyst.
2
7
the TOPOS software package.
RESULTS AND DISCUSSION
Crystal Structure of SUT-6-Zn. Single crystal X-ray
diffraction analysis revealed that all three compounds are
isostructural and crystallize in a cubic space group Pn3. The
representative crystal structure of SUT-6-Zn is discussed in
detail here.
■
̅
The framework of SUT-6-Zn is constructed from V B
1
2 18
EXPERIMENTAL SECTION
clusters bridged by ZnO polyhedra. The V B cluster (Figure
■
5
12 18
Synthesis. The title compound was synthesized by hydrothermal
reaction of M(NO ) ·6H O (M = Zn, Ni, or Mn) with diethylenetri-
1a) consists of a puckered B O (OH) ring (Figure 1b)
18 36 6
3
2
2
amine, NH B O , NH VO , and H BO in H O at 180 °C for 7 days.
All chemicals were of analytical grade and used as supplied.
4
5
10
4
3
3
3
2
Synthesis of SUT-6-Zn. A mixture of NH B O (0.2725 g, 1
4
5
10
mmol), NH VO (0.0421 g, 0.4 mmol), H BO (0.1212 g, 2 mmol),
4
3
3
3
Zn(NO ) .6H O (0.0604 g, 0.2 mmol), NH(CH CH NH ) (0.11
3
2
2
2
2
2 2
mL, 1 mmol), and 2 mL of H O in a molar ratio of 10:4:20:2:10:110
2
was sealed in a 5 mL Teflon tube seated in stainless steel, heated at
1
80 °C for 7 days, and then cooled to room temperature in air. Red-
brown octahedral crystals of SUT-6-Zn were recovered by filtration,
washed with distilled water, and dried in air, and the yield is about 80%
based on NH VO . The purity was confirmed by powder X-ray
4
3
diffraction as shown in Figure S1, Supporting Information.
SUT-6-Mn and SUT-6-Ni were synthesized by the same procedure
with a recipe similar to that for SUT-6-Zn except for replacing the
metal source Zn(NO ) ·6H O with Mn(NO ) ·6H O and Ni(NO ) ·
3
2
2
3
2
2
3 2
6
H O.
2
Structure Characterization. Single crystal X-ray diffraction data
were collected at 100 K on an Oxford Diffraction Xcalibur CCD
diffractometer with Mo Kα radiation (λ = 0.71073 Å). Data integration
and multiscan absorption correction were carried out by the CrysAlis
25
Figure 1. (a) Structure building units in SUT-6-Zn. (b) B O ring.
18 40
software package from Oxford Diffraction. Structure refinements
26
(
c) V O oxo clusters. (d) Node representation of the
were done with the SHELXL97 program. Crystallographic data for
6 19
(
ZnO ) (VO) O B O (OH) cluster. Color codes: VO , dark
SUT-6-Zn: cubic, space group Pn3, a = 18.8164(1)Å, Z = 4, R =
̅
3
6
12
6
18 36
6
5
1
green; BO and BO , yellow; ZnO , green; and oxygen atoms, red.
0
.0411, and wR2 = 0.1404 (all data). Crystallographic data for SUT-6-
3
4
5
Ni: cubic, space group Pn3
̅
1
=
0.1918(all data). Crystallographic data for SUT-6-Mn: cubic, space
group Pn3
data).
̅
, a = 18.9341(2) Å, Z = 4, R = 0.0684, wR2 = 0.2008 (all
sandwiched by two V
6
O
18 triangles. The B18O36(OH) ring
6
1
6
−
contains six B O (OH) units that exhibits a cyclohexane-like
3
7
6−
Catalytic Reactions. SUT-6-Zn was used as a catalyst to study the
oxidation of alkylbenzenes. The typical procedure for oxidation of
alkylbenzenes is as follows: SUT-6-Zn (8.4 mg, 0.002 mmol),
chair conformation with the B O (OH) unit at each of the six
vertices. According to the fundamental building theory
3 7
28
6−
proposed by Kniep Ru
̈
diger,
the B O (OH)
and
3
7
ethylbenzene (212 mg, 2 mmol), TBHP (1.286 g, 70 wt % in H O,
24−
2
B O (OH)
units can be described as Δ2□:<Δ2□> and
18
36
6
1
0 mmol), CH CN (1 mL), and HOAc (0.2 mL) were stirred at 65 °C
3
1
6Δ12□:<12□≥<Δ2□> <Δ2□><Δ2□><Δ2□><Δ2□>
for 24 h. The product was identified by H NMR with known
<
>
Δ2□>, respectively (□, tetrahedron; Δ, trigonal planar; <···
literature data. The used SUT-6-Zn was recovered by centrifugation,
washed with CH CN, and subsequently used in the successive runs.
, ring motif; [···], branching polyhedron/anion; |, separator for
3
The crude reaction mixture from the catalytical reaction was analyzed
branches; −,=, ≡ ···, 1, 2, 3, ··· common polyhedra). The V O
6 18
1
by H NMR.
unit is a triangular metal oxo moiety and is composed of six
5
032
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Chemistry of Materials
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alternatively cis/trans edge-shared VO square pyramids (Figure
5
1
c). The V O triangles sandwich the puckered B O (OH)
6 18 18 36 6
rings through six B-(μ -O)-V bonds and three B -(μ -O)-V
3
2
2
3
bonds with all VO pyramids pointing outside of the cluster.
5
The formed V B clusters were then linked into a 3D
12 18
framework by ZnO polyhedra. Unlike the zinc-incorporated
5
c l u s t e r i n { [ Z n ( d i e n ) ] [ Z n ( d i e n ) ( H O ) ]
2
2
4
29
[
(VO) O [B O (OH) (H O)} ·15H O, where six zinc
12 6 18 36 6 2 2 2
atoms show two different coordination configurations with
four in octahedra and two in distorted bipyramids, each zinc
atom in SUT-6 is coordinated to one water molecule and two
pairs of oxygen atoms from two separate V B clusters to form
1
2 18
a square pyramid.
The 3D framework of SUT-6-Zn can be clearly presented
using topology analysis. Each V B cluster connects to six
1
2 18
V B clusters through the ZnO polyhedra in a planar manner
12
18
5
(
Figure 2a), which can be represented by a hexagon where each
Figure 3. Hexagon representation of SUT-6: (a) 12-ring windows
along the ⟨100⟩ direction. (b) 18-ring windows along the ⟨110⟩
direction. (c) 18-ring windows along the ⟨111⟩ direction. (d)
Interpenetrated diamond-like channel system is shown as red nets.
3
.1%; H 2.54%; N 5.75%). The channels are mainly occupied
+
by the organic templates, NH , and water molecules. Because
4
of the disorders of the guest specises, it was not possible to
determine their exact positions. TGA (Figure S2, Supporting
Information) and in-situ powder X-ray diffraction (Figure 4)
Figure 2. (a) Node (the V B cluster) and edge (the ZnO5
polyhedron) in SUT-6. (b) Orientation of the adjacent hexagons in
SUT-6. (c) hxg topology of SUT-6.
1
2 18
ZnO polyhedron is a vertex with the V B cluster in the
5
12 18
center (Figure 1d). Different from the normal assembling of
hexagons where a regular hexagonal layered topology is formed,
adjacent hexagons in SUT-6 have a dihedral angle of 70.5° from
each other (Figure 2b) and are connected into a cubic network
3
0
(
Figure 2c). This network shows a semiregular hxg topology,
6
4
which has the isohedral natural tiling 4 ·6 and a transitivity of
122. Unlike the regular nets which are often found in many
1
open-frameworks especially inorganic structures, the hxg
topology is rare in inorganic structures. Only a few examples
3
1,32
were reported in metal−organic frameworks.
According to
our knowledge, SUT-6 is the first example of inorganic
frameworks with the hxg topology.
The channel system in SUT-6-Zn is mainly formed by the
V B clusters with BO and VO groups pointing to the
1
2
18
3
channel. On the basis of the topology analysis, each edge of the
hexagon in Figure 1d contributes two T atoms (B O ), and
Figure 4. In situ powder X-ray diffraction patterns of SUT-6-Zn in air.
2
7
each connection of the hexagons contributes one T atom
ZnO ) as shown in Figure 1a. Thus, the channel system in
SUT-6 can also be clearly represented by these hexagons. As
shown in Figure 3, different windows can be observed along
different directions. Along the ⟨100⟩ direction, four edges form
(
show that the guest molecules could be partially removed by
heating the sample up to 350 °C while the framework remained
intact. By further increasing the temperature, the structure
collapsed, and all guest molecules were released slowly.
5
1
2-ring windows as shown in Figure 3a, but due to the BO and
To check the charge balance of the whole structure, bond
valence sum was calculated for vanadium. It shows that
vanadium has an average bond valence sum of about +4.094 in
3
VO pointing to the channel, this window is almost closed.
Along the ⟨110⟩ and ⟨111⟩ directions, 18-ring windows are
formed by six edges as shown in Figure 3b−c. Small cage-like
voids in SUT-6 are connected through these 18-ring windows
and form two interpenetrated diamond-like channel systems as
shown in Figure 3d.
On the basis of the structure refinement and CHN elemental
analysis (obsd: weight ratio of C 2.9%; H 2.6%; N 5.8%), the
chemical formula of SUT-6-Zn was deduced as
4
+
SUT-6-Zn without any preferential occupancies for V and
5+[13]
V
indicating possible mixed oxidation states of 4+ and 5+.
The mixed oxidation explains the red-brown color of the
3
3,22
crystals.
A similar observation was reported in other
21
vanadoborate compounds. This result is inconsistent with the
XPS results with a peak at 516.1 eV for V and a shoulder at
4+
5+
4+
3/2
about 517.1 eV for V , which are attributed to V 2p and
5+
3/2
[
V B Zn O H ]·3(C N H )·10NH ·5H O (calcd: C
V
2p , respectively (Figure S3, Supporting Information,
1
2
18
3
63 12
4
3
16
4
2
5
033
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Chemistry of Materials
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3
4
ESI). Because of the broad peak width, the accurate ratio of
4+
5+
V
and V in SUT-6 could not be obtained from XPS.
SUT-6 could also be obtained using metals other than Zn, for
example, Ni and Mn. The structures of SUT-6-Ni and SUT-6-
Mn were determined by single crystal X-ray diffraction. Both
SUT-6-Ni and SUT-6-Mn have a similar unit cell, the same
building units, and the same topology as SUT-6-Zn. The only
difference for the three structures is the coordination
environments for the metal ions. Unlike the square pyramidal
coordination for the Zn ions (Figure 5a), Ni and Mn ions have
Figure 6. Low-dimensional V B structures synthesized with large
12 18
amounts of amine templates. (a) One-dimensional chain structure
with B O as bridges in VB1; (b) zero-dimensional cage structure in
2
5
monoclinic symmetry viewed along the b axis in VB2; (c) zero-
dimensional cage structure in trigonal symmetry viewed along the c
axis in VB3.
vanadoborates with metal polyhedra as linkers, it is important
to use small amounts of amine templates.
Figure 5. Coordination environment of Zn, Ni, and Mn in SUT-6. Ow
indicates the oxygen from water molecule, and the other oxygen atoms
are from V B clusters.
Catalytic Performance. Considering SUT-6-Zn having V-
species with mixed oxidation states, which may have potential
3
7
12
18
as a heterogeneous catalyst in benzylic C−H bond oxidation,
we were encouraged to investigate its activity in the oxidation
of alkylbenzenes to phenylketones. To our delight, the
oxidation of ethylbenzene catalyzed by SUT-6-Zn was realized
slightly twisted octahedral coordinations (Figure 5b−c), with
four equatorial oxygen atoms from two different BO and two
in a mixed solvent of CH CN/HOAc (5/1) at 65 °C for 24 h
4
3
1
axial oxygen atoms from water molecules.
with tert-butylhydroperoxide (TBHP) as the oxidant. H NMR
Synthesis Conditions. It seems that the introduction of
metal ions Zn, Ni, or Mn plays a very important role in
assembling the open-framework vanadoborate structures since
they serve as linkers to connect the isolated V B clusters.
analysis of the crude reaction mixture showed that only one
product, acetophenone, was formed in a good yield of 75% with
0.1 mol % catalyst loading (Table 1, entry 1). A control
experiment omitting SUT-6-Zn under the same conditions gave
only <2% yield of product, which confirms that SUT-6-Zn plays
an important role as a highly efficient catalyst in this
transformation (Table 1, entry 2).
1
2 18
However, similar synthesis routines were widely used in
1
6,17,20,21,24,33,35,36
previous work,
but no 3D structures were
35
36
obtained. Zhang et al. and Liu et al. successfully synthesized
the zinc complexes and modified the V B clusters using
SUT-6-Zn can also catalytically oxidize various alkylbenzenes
under the above-mentioned reaction conditions (Table 1,
entries 3−6). Structurally similar propylbenzene and isobu-
tylbenzene were tried and gave the corresponding phenyl-
ketones in low yields (Table 1, entries 3 and 4). However,
SUT-6-Zn could efficiently catalyze the oxidation of diphenyl-
methane and fluorene to the corresponding ketones in 94% and
91% yields, respectively (Table 1, entries 5 and 6). These
results clearly indicate that the oxidations of alkylbenzenes
using SUT-6-Zn as the catalyst were not substrate size-selective
and that the oxidations most likely occur on the solid surface.
The electronic effect of the substrates may also affect the yields
to some extent.
1
2 18
ethylenediamine and N,N′-bis(3-aminopropyl)-1,3-propanedi-
amine, separately. However, the zinc atoms were five-
coordinated with one coordination site from a V B cluster
12 18
and the other four sites saturated by either two ethylenediamine
ions or one N,N′-bis(3-aminopropyl)-1,3-propanediamine ion.
There is no other coordination site to link the V B clusters
1
2 18
further. This indicates that the small amount of amines might
be the reason for forming 3D vanadoborates in SUT-6.
Therefore, we systematically investigated the synthesis
conditions in SUT-6-Zn. We kept all synthesis parameters
except for the amount of diethylenetriamine, which was varied
from 0.5 to 2 mmol. When the amount of diethylenetriamine
was between 0.5 and 1 mmol, pure SUT-6 could be
synthesized. When the amount of diethylenetriamine was
increased to 1.5 mmol, SUT-6 was formed together with two
impurities VB1 with 1D chains (Figure 6a) and VB2 with 0D
cages (Figure 6b). When the amount of diethylenetriamine was
further increased to 2 mmol, a mixture of VB2 and another 0D
cage structure VB3 (Figure 6c) were obtained without any
SUT-6. It is worth noting that although there are Zn ions in the
The heterogeneous nature of the catalyst was proved by the
following control experiment. After the reaction of ethyl-
benzene, SUT-6-Zn, and TBHP in CH CN/HOAc at 65 °C for
3
2 h, the solid was filtrated off, and the filtrate was subsequently
1
stirred at 65 °C for another 22 h. H NMR analysis of the
resulting crude reaction mixture showed that the conversion of
ethylbenzene had not changed and was still only 27%, which
suggests that this catalyst system is heterogeneous (compare
this result with entry 1 in Table 1).
1
D VB1 structure, the chains are formed by B O bridges
2 5
instead of Zn polyhedra. In fact, the Zn ions are in trigonal
bipyramidal coordination, and three of the coordination sites
are occupied by diethylenetriamine, which leaves no additional
space to link V B clusters further. Thus, these results confirm
that with high concentration of diethylenetriamine, the possible
linker (Zn) is more likely to be saturated by amines and only
low dimensional structures were obtained. To synthesize 3D
The catalyst can be easily recovered by centrifugation and
filtration after the oxidation, and subsequently used in the
succesive runs for 8 cycles without significant loss in yield
(Figure 7). This remarkable catalytic activity was also
demonstrated with a large-scale reaction of ethylbenzene (50
mmol, 5.3 g) catalyzed by only 9 mg of SUT-6-Zn (0.002
mmol) in 72% isolated yield. It should be noted that to the best
12 18
5
034
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Chemistry of Materials
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Table 1. [SUT-6-Zn]-Catalyzed Oxidation of Alkylbenzenes
to Phenylketones
of our knowledge, this catalyst is significantly superior to other
a
reported vanadium heterogeneous catalysts for the oxdiation of
37,38
ethylbenzene to acetophenone.
It has been proposed that benzylic C−H oxidation catalyzed
by vanadium-incorporated zinc complexes may involve a C−H
37
abstraction mechanism via a benzylic alcohol intermidate,
which was further supported in this case by the successful
conversion of 1-phenylethanol to acetophenone catalyzed by
SUT-6-Zn in 80% yield (see Supporting Information).
We checked the catalyst recovered after the first and the
eighth cycles by powder X-ray diffraction. To our surprise,
SUT-6-Zn was converted to a vanadium-incoporated ZnC O ·
2
4
2
H O during the first reaction cycle, as shown in Figure S6 and
2
S7 (Supporting Information). The crystallinity of ZnC O ·
2
2
4
H O was improved after each cycle, and the reaction activity
2
remained. In order to find out which is the actual effective
catalyst, several control experiments were carried out. We
found that a commercial ZnC O ·2H O did not give any
2
4
2
oxidation products, and when NH VO or NH VO together
4
3
4
3
with ZnC O ·2H O were used, the reactions afforded
2
4
2
acetophenone in yields comparable to those of SUT-6-Zn.
However, it was difficult to recycle the catalyst after the
oxidation since NH VO was soluble in the reaction system in
4
3
contrast to SUT-6-Zn. These results indicate that the actual
heterogeneous catalyst is a vanadium-incoporated ZnC O ·
2
4
2
H O compound, which is stable and effective throughout the
2
different cycles. The TEM image shows that the recovered
catalyst after eight cycles has a plate-like morphology, which is
consistent with the different peak widths in the PXRD pattern.
ICP results show that the recoved catalyst contains zinc and
vanadium with the Zn/V ratio of about 52:1. It was speculated
that the active vanadium-incorporated zinc catalyst may be
generated in situ in the reaction system. Thus, SUT-6-Zn can
be considered as a precatalyst for the oxidation of
alkylbenzenes, and the mechanism of the formation of the
vanadium-incoporated ZnC O ·2H O is still under investiga-
2
4
2
tion.
CONCLUSIONS
a
■
Alkylbenzene (2 mmol), TBHP (5 equiv, 70 wt % in H O), SUT-6-
2
In summary, three 3D open-framework vanadoborates (SUT-6-
Zn, SUT-6-Mn, and SUT-6-Ni) were synthesized. Single crystal
X-ray diffraction revealed that they have the same hxg topology
with 18-ring channel systems. We found that the key
experimental factor for achieving 3D vanadoborates was using
lower amounts of amine templates to facilitate the transition
metal ions to link V B clusters into 3D frameworks. The
Zn (0.002 mmol), CH CN (1 mL), and HOAc (0.2 mL) were stirred
at 65 °C for 24 h. Yield determined by NMR spectroscopy with
anisole as the internal standard. Yield of isolated product. No
3
b
c
d
e
f
catalyst. Second cycle. Eighth cycle.
12 18
catalytic test shows that SUT-6-Zn works as a precatalyst and
has highly effective heterogeneous catalytic oxidation proper-
ties.
ASSOCIATED CONTENT
■
*
S
Supporting Information
TG, UV−vis-NIR spectrum, simulated PXRD, XPS of SUT-6-
Zn, PXRD, TEM image, EDS of SUT-6-Zn after a catalytic
reaction, and other details of catalytic reaction performance
(
PDF and CIF). This material is available free of charge via the
Internet at http://pubs.acs.org.
Figure 7. Catalytic oxidation of ethylbenzene by SUT-6-Zn at different
runs.
AUTHOR INFORMATION
■
Corresponding Authors
(J.S.) E-mail: junliang.sun@mmk.su.se.
(J.-E.B.) E-mail: jeb@organ.su.se.
*
*
5
035
dx.doi.org/10.1021/cm401400m | Chem. Mater. 2013, 25, 5031−5036

Chemistry of Materials
Article
Notes
(29) Liu, X.; Zhou, J.; Zhou, Z.; Zhang, F. J. Clust. Sci. 2011, 22, 65.
(
30) Friedrichs, O. D.; O’Keeffe, M.; Yaghi, O. M. Acta Crystallogr.,
Sect. A 2003, 59, 515.
31) Liu, C. S.; Yang, X. G.; Hu, M.; Du, M.; Fang, S. M. Chem.
Commun. 2012, 48, 7459.
32) Yuan, N.; Sheng, T. L.; Zhang, J.; Tian, C. B.; Hu, S. M; Huang,
The authors declare no competing financial interest.
(
ACKNOWLEDGMENTS
This project was supported by Swedish Research Council (VR),
Swedish Governmental Agency for Innovation Systems
■
(
X. H.; Wang, F.; Wu, X. T. CrystEngComm 2011, 13, 5951.
(33) Zhou, J.; Liu, X.; Hu, F. L.; Zou, H. H.; Li, X. J. Inorg. Chem.
Commun. 2012, 25, 51.
(34) Duan, W. J.; Cui, X. B.; Xu, Y.; Xu, J. Q.; Yu, H. H.; Yi, Z. H.;
Cui, J. W.; Wang, T. G. J. Solid State Chem. 2007, 180, 1875.
(
VINNOVA) through Berzelii EXSELENT, National Basic
Research Program of China (2013CB933402), and Diamond
Light Source I19. H.C. thanks China Scholarship Council.
(
35) Zhang, L. R.; Shi, Z.; Yang, G. Y.; Chen, X. M.; Feng, S. H. J.
REFERENCES
■
Solid State Chem. 1999, 148, 450.
(
1) Maspoch, D.; Molina, D. R.; Veciana, J. Chem. Soc. Rev. 2007, 36,
(
(
36) Liu, X.; Zhou, J. Z. Naturforsch., B: Chem. Sci. 2011, 66.
37) Xia, J.-B.; Cormier, K. W.; Chen, C. Chem. Sci. 2012, 3, 2240
770.
(
2) Wilson, S. T.; Lok, B. M.; Messina, C. A.; Cannan, T. R.;
Flanigen, E. M. J. Am. Chem. Soc. 1982, 104, 1146.
3) Lok, B. M.; Messina, C. A.; Patton, R. L.; Gajek, R. T.; Cannan,
T. R.; Flanigen, E. M. J. Am. Chem. Soc. 1984, 106, 6093.
4) Cheetham, A. K.; Ferey, G.; Loiseau, T. Angew. Chem., Int. Ed.
999, 38, 3268.
5) Christensen, K. E.; Inge, A. K.; Zou, X. D. Cryst. Rev. 2010, 16,
1.
and references cited therein..
(38) (a) Yang, X.-L.; Xie, M.-H.; Zou, C.; He, Y.; Chen, B.; O’Keeffe,
(
M.; Wu, C.-D. J. Am. Chem. Soc. 2012, 134, 10638. (b) Zou, C.; Zhang,
Z.; Xu, X.; Gong, Q.; Li, J.; Wu, C.-D. J. Am. Chem. Soc. 2012, 134, 87.
(
1
(
9
(
(
́
(
c) Aguadero, A.; Falcon, H.; Campos-Martin, J. M.; Al-Zahrani, S. M.;
Fierro, J. L. G.; Alonso, J. A. Angew. Chem., Int. Ed. 2011, 50, 6557.
d) Dhakshinamoorthy, A.; Alvaro, M.; Garcia, H. Chem.Eur. J.
011, 17, 6256. (e) Ghiaci, M.; Molaie, F.; Sedaghat, M. E.; Dorostkar,
(
2
6) Natarajan, S.; Mandal, S. Angew. Chem., Int. Ed. 2008, 47, 4798.
7) Huang, S. L.; Christensen, K. E.; Peskov, M. V.; Yang, S. H.; Li,
N. Catal. Commun. 2010, 11, 694. (f) Yu, F.; Long, Y.-X.; Ren, Y.-P.;
Kong, X.-J.; Long, L.-S.; Huang, R.-B.; Zheng, L.-S. Dalton Trans.
K.; Zou, X. D.; Sun, J. L. Inorg. Chem. 2011, 50, 9921.
8) Zhou, J.; Zhang, J.; Fang, W. H.; Yang, G. Y. Chem.Eur. J. 2010,
6, 13253.
9) Wang, X. Q.; Liu, L. M.; Jacobson, A. J. J. Am. Chem. Soc. 2002,
24, 7812.
10) Tripathi, A.; Hughbanks, T.; Clearfield, A. J. Am. Chem. Soc.
003, 125, 10528.
11) Soghomonian, V.; Chen, Q.; Haushalter, R. C.; Zubieta, J.
Angew. Chem., Int. Ed. 1993, 32, 610.
12) Leithall, R. M.; Shetti, V. N.; Maurelli, S.; Chiesa, M.; Gianotti,
E.; Raja, R. J. Am. Chem. Soc. 2013, 135, 2915.
13) Rijssenbeek, J. T.; Rose, D. J.; Haushalter, R. C.; Zubieta, J.
Angew. Chem., Int. Ed. 1997, 36, 1008.
14) Cai, Q. H.; Lu, B.; Zhang, J. W.; Shan, Y. K. J. Chem. Crystallogr.
008, 38, 321.
15) Liu, X.; Zhou, J.; An, L. T.; Chen, R.; Hu, F. L.; Tang, Q. L. J.
Solid State Chem. 2013, 201, 79.
16) Wu, M. M.; Law, T. S. C.; Sung, H. H. Y.; Cai, J. W.; Williams, I.
D. Chem. Commun. 2005, 14, 1827.
17) Warren, C. J.; Haushalter, R. C.; Rose, D. J.; Zubieta, J. Inorg.
Chem. Acta 1998, 282, 123.
18) Yamase, T.; Suzuki, M.; Ohtaka, K. J. Chem. Soc., Dalton Trans.
997, 2463.
19) Warren, C. J.; Rose, D. J.; Haushalter, R. C.; Zubieta, J. Inorg.
Chem. 1998, 37, 1140.
20) Kareen, B.; Pierre, E. C.; Andres
2
010, 39, 7588. (g) Singh, A. P.; Torita, N.; Shylesh, S.; Iwasa, N.;
(
1
(
1
(
2
(
Arai, M. Catal. Lett. 2009, 132, 492. (h) Mohapatra, S. K.; Selvam, P. J.
Catal. 2007, 249, 394. (i) Radhika, T.; Sugunan, S. Catal. Commun.
2
007, 8, 150. (j) Zhang, J.-L.; Huang, J.-S.; Che, C.-M. Chem.Eur. J.
2
006, 12, 3020. (k) Bhoware, S. S.; Shylesh, S.; Kamble, K. R.; Singh,
̇
A. P. J. Mol. Catal. A: Chem. 2006, 255, 123. (l) Burri, E.; ohm, M.;
Daguenet, C.; Severin, K. Chem.Eur. J. 2005, 11, 5055. (m) Khenkin,
A. M.; Neumann, R. J. Am. Chem. Soc. 2004, 126, 6356.
(
(
(
2
(
(
(
(
1
(
(
́ ́
, V.; Diego, V. Y.; Veronica, P.
G.; María, G. F. V.; Rafael, A. A.; Pivan, J. Y.; Eric, L. F.; Evgenia, S.
Inorg. Chim. Acta 2011, 367, 21.
(
21) Hermosilla-Ibanez, P.; Car, P. E.; Vega, A.; Costamagna, J.;
Caruso, F.; Pivan, J.-Y.; Le Fur, E.; Spodine, E.; Venegas-Yazigi, D.
CrystEngComm 2012, 14, 5604.
(
(
22) Sun, Y. Q.; Li, G. M.; Chen, Y. P. Dalton Trans. 2012, 41, 5774.
23) Williams, I. D.; Wu, M.; Sung, H. H. Y.; Law, T. S. C.; Zhang, X.
X. Contemp. Boron Chem. 2000, 104−112.
24) Zhou, J.; Liu, X.; Hu, F. L.; Zou, H. H.; Li, R.; Li, X. J. RSC Adv.
012, 2, 10937.
25) Crysalis Sofware System, version 171.35.19; Xcalibur CCD
System; Oxford Diffraction Ltd.: Yarnton, U.K., 2011.
26) (a) Sheldrick, G. M. SHELXS-97, Program for Solution of Crystal
Structures; University of Gottingen: Germany, 1997; Sheldrick, G. M.
Acta Crystallogr., Sect. A 2008, 64, 112.
27) Blatov, V. IUCr CompComm Newsletter. 2006, 7, 4. TOPOS is
available at http://www.topos.ssu.samara.ru.
28) Ewald, B.; Huang, Y. X.; Kniep, R. Z. Anorg. Allg. Chem. 2007,
33, 1517.
(
2
(
(
̈
(
(
6
5
036
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