Au@Cu(II)-MOF: Highly Efficient Bifunctional Heterogeneous Catalyst for Successive Oxidation-Condensation Reactions

Article abstract of DOI:10.1021/acs.inorgchem.6b00925

A new composite Au@Cu(II)-MOF catalyst has been synthesized via solution impregnation and full characterized by HRTEM, SEM-EDS, XRD, gas adsorption-desorption, XPS, and ICP analysis. It has been shown here that the Cu(II)-framework can be a useful platform to stabilize and support gold nanoparticles (Au NPs). The obtained Au@Cu(II)-MOF exhibits a bifunctional catalytic behavior and is able to promote selective aerobic benzyl alcohol oxidation-Knoevenagel condensation in a stepwise way.

Full text of DOI:10.1021/acs.inorgchem.6b00925

Article
pubs.acs.org/IC
Au@Cu(II)-MOF: Highly Efficient Bifunctional Heterogeneous Catalyst
for Successive Oxidation−Condensation Reactions
Jing-Si Wang, Fa-Zheng Jin, Hui-Chao Ma, Xiao-Bo Li, Ming-Yang Liu, Jing-Lan Kan, Gong-Jun Chen,*
and Yu-Bin Dong*
College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for
Chemical Imaging in Universities of Shandong, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong
Normal University, Jinan 250014, P. R. China
S
* Supporting Information
ABSTRACT: A new composite Au@Cu(II)-MOF catalyst has been
synthesized via solution impregnation and full characterized by HRTEM,
SEM-EDS, XRD, gas adsorption−desorption, XPS, and ICP analysis. It
has been shown here that the Cu(II)-framework can be a useful platform
to stabilize and support gold nanoparticles (Au NPs). The obtained Au@
Cu(II)-MOF exhibits a bifunctional catalytic behavior and is able to
promote selective aerobic benzyl alcohol oxidation−Knoevenagel
condensation in a stepwise way.
embedded composite catalyst Au@Cu(II)-MOF (1) via
solution impregnation. The obtained 1 exhibits a bifunctional
heterogeneous catalytic nature and, furthermore, catalyzes
benzyl alcohol oxidiation and Knoevenagel condensation
reactions in a successive manner.
INTRODUCTION
■
Heterogeneous catalysis has received more and more attention
in the past few decades.1 The fabrication of a composite type of
heterogeneous catalysts is one of the practical approaches to
access solid catalysts for heterogeneous catalysis.2 For design
and synthesis of composite catalysts, various porous materials,
such as zeolites, mesoporous aluminosilicates, metal oxides,
carbon, and polymers, have been chosen and used as supports
to upload active catalytic metal species, especially the high
catalytic performance Au nanoparticles (Au NPs).3 As we
know, Au NPs have been recognized as very active and effective
green catalysts and are widely used in promoting many types of
organic reactions such as oxidation of alcohols, reduction of
nitro-aromatic compounds, water−gas shift reaction, and so
on.4
As a unique class of porous materials, metal−organic
frameworks (MOFs) are promising platforms for creating a
composite heterogeneous catalyst system.5 Owing to their
diverse chemical compositions, high surface areas, tunable pore
size, and internal microenvironments, MOFs allow the
implementation of catalytic properties by embedding metal
NPs.6 This strategy is widely accepted and becomes a
significant tool for expanding MOF-supported application in
catalysis. On the other hand, MOFs themselves are inherent
heterogeneous catalysts due to their inorganic−organic hybrid
composition and polymeric nature. Therefore, the incorpo-
ration of MOF-supports with the metal NPs would lead to
enhanced or even novel catalytic properties compared to their
pristine counterparts.7
EXPERIMENTAL SECTION
■
Materials and Chemicals. The reagents and solvents employed
were commercially available and used without further purification.
Cu(II)-MOF (Cu3L6) was prepared by the combination of a pyridyl
substituted diketonate ligand (HL) and Cu(OAc)2 in a CH2Cl2/
MeOH mixed solvent system, which was reported by us previously.8a,9
Instrumentation. The powder diffractometer (XRD) patterns
were collected by a D8 ADVANCE X-ray with Cu Kα radiation (λ =
1.5405 Å). The total surface areas of the catalysts were measured by
the BET (Brunauer−Emmer−Teller) method using carbon dioxide
adsorption at 195 K; this was done by the Micromeritics ASAP 2000
sorption/desorption analyzer. ICP-LC was performed on an IRIS
InterpidII XSP and NU AttoM. HRTEM (high resolution transmission
electron microscopy) analysis was performed on a JEOL 2100 electron
microscope at an operating voltage of 200 kV. Scanning electron
microscopy (SEM) images and energy dispersive X-ray (EDX)
spectroscopy were taken on a SUB010 scanning electron microscope
with acceleration voltage of 20 kV. Gas chromatography (GC) analysis
was performed on an Agilent 7890B GC. Electron spin resonance
(ESR) spectra were obtained from a Bruker A300-10/12/S-LC. XPS
spectra were obtained from PHI Versaprobe II. UV−vis absorption
spectra were recorded at room temperature in quartz cells of 1 cm path
length using a TU-1800 SPC spectrophotometer.
As a continuation of our work with the NPs-loaded MOFs
Received: April 14, 2016
materials,8 we report herein the fabrication of Au NPs
© XXXX American Chemical Society
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Scheme 1. Schematic Representation of Synthesis of 1 from Cu(II)-MOF and HAuCl4
Synthesis of 1. Cu(II)-MOF (15 mg, 0.003 mmol) was added to a
CH3OH (10 mL) solution of chloroauric acid (20 mg, 0.2 mmol). The
mixture was stirred for 1 h at room temperature. The resulting solid
was isolated by centrifugation and washed with CH2Cl2. The obtained
green-yellow crystalline solid was mixed with NaBH4 (50 mg, 1.3
mmol) in water (4 mL), and the mixture was stirred for an additional 5
h to afford 1 as a dark brown solid. The obtained crystalline solids
were washed with CH3CN and EtOH and dried in air. Inductively
coupled plasma (ICP) measurement indicated that the encapsulated
amount of Au NPs in 1 is 9.38 wt %.
Reduction of 4-Nitrophenol (4-NP) to 4-Aminophenyl (4-
AP). Freshly prepared NaBH4 aqueous solution (2 M, 30 equiv) was
added to an aqueous solution (3 mL) of 4-NP (0.35g, 2.5 mmol) with
1 (5.4 mg, 0.1 mol %) at room temperature. The absorbance spectra
were used to monitor (wavelength range 280−600 nm) the reaction
progress.
the reduction of Au(III)@Cu(II)-MOF with NaBH4 in
aqueous solution along with a distinct color change (from
green-yellow to dark brown, Scheme 1). The uploaded amount
of Au, as determined by inductively coupled plasma (ICP)
measurement, is up to ca. 9.38 wt %. The oxidation state of the
encapsulated Au after reduction was determined by X-ray
photoelectron spectroscopy (XPS). The observation of the Au
4f7/2 and 4f5/2 peaks at 83.86 and 87.46 eV in XPS of 1
demonstrated the reduction from Au(III) to Au(0) (Support-
ing Information, Figure S1).9,10 In addition, the ESR spectra
show that no valence state change of the Cu(II) in 1 was
observed after the treatment by NaBH4 in aqueous solution
under the reaction conditions (Supporting Information, Figure
S2).
High resolution transmission electron microscopy
(HRTEM) was used to investigate the dispersion and size
distribution of the Au NPs in 1. As shown in Figure 1, nearly
Benzyl Alcohol Oxidation Reaction Procedure. The catalytic
activity of 1 for the aerobic oxidation of benzyl alcohol to
benzaldehyde was tested in air. A mixture of benzyl alcohols (20 μL,
0.20 mmol), 1 (13 mg, Au 3 mol %), and toluene (3 mL) was stirred
at 110 °C for 15 h in air (monitored by GC) to afford the
corresponding aldehydes.
Benzyl Alcohol Oxidation−Knoevenagel Reaction Proce-
dure. A mixture of benzyl alcohols (30 μL, 0.30 mmol) in the
presence of 1 (19 mg, 3 mol %) in toluene (3 mL) was heated at 110
°C for 15 h in air. After cooling down to the room temperature, a
MeOH solution (2 mL) of malononitrile (13.4 μL, 0.34 mmol) was
added to the above system. The mixture was stirred for an additional 7
h at room temperature in air to afford the corresponding 2-
benzylidenemalononitriles (monitored by GC).
Catalyst Regeneration. Material 1 was recovered by centrifuga-
tion, then washed with ethanol (3.0 mL) and dichloromethane (3.0
mL) (3 times), and dried at 90 °C in vacuum for the next run under
the same reaction conditions.
Figure 1. Left: HRTEM image of 1. Right: XRPD patterns of Cu(II)-
MOF, Au(III)@MOF, and 1.
monodisperse Au NPs with approximately spherical shape were
uniformly distributed in 1, and the average particle size was ca.
2 nm. The atomic lattice fringes with spacing of 0.23 nm
corresponding to Au (111) planes were observed.11 The SEM-
EDX elemental mapping of 1 was also measured. Figure 2
shows the elemental maps of the Au and Cu images,
respectively, indicating that Au NPs were highly dispersed in
Leaching Test. The solid catalyst Au@Cu(II)-MOF (1) was
separated from the hot solution right after reaction for 6 h. The
reaction was continued with the filtrate in the absence of 1 for
additional 14 h. No further increase in either the conversion of benzyl
alcohol or selectivity of aldehyde was detected, which confirms the
catalytically active sites for this oxidation reaction located on 1.
RESULTS AND DISCUSSION
■
Synthesis and Characterization of 1. Cu(II)-MOF was
prepared by our previously reported method. It possesses a 3-
fold interpenetrating NbO-type of network with nanosized
hexagonal channels.8a,9 The opposite Cu···Cu distance in the
channel is 22.9330(3) Å. Material 1 was prepared via solution
impregnation (Scheme 1). The combination of HAuCl4 and
Cu(II)-MOF in CH3OH at room temperature (1 h) yields
Au(III)@Cu(II)-MOF as green-yellow crystalline solid
(Scheme 1). The Au NPs-embedded 1 was synthesized by
Figure 2. SEM image and SEM-EDX elemental mapping of 1.
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Cu(II)-MOF matrix. Notably, the XRPD pattern of 1 is in good
agreement with that of Cu(II)-MOF and 1 (Figure 1), which
indicates that the structural integrity of the Cu(II)-MOF is
well-preserved.
In addition, the permanent porosity of 1 was determined by
measuring carbon dioxide gas (CO2) adsorption at 195 K
(Supporting Information, Figure S3). Compared to that of
Cu(II)-MOF, the surface area of 1 decreased from 1129.24 to
70.27 m2/g. The adsorption change was clearly caused by the
Au NPs doping. The mesopore size distribution curve,
calculated from Barrett−Joyner−Halenda analysis, shows a
narrow pore diameter distribution at ca. 1.3 nm and ca. 0.9 nm
for Cu(II)-MOF and Au@Cu(II)-MOF (1), respectively
(Supporting Information, Figure S3).
the Au NPs are well-embedded in the MOF matrix without
observable aggregation, and crystallinity of the MOF was
maintained after the reaction (Supporting Information, Figure
S4). Next, we find that 1 exhibits similar reactivity with
excellent yields toward the reduction of 2-nitrophenol (2-NP)
and 3-nitrophenol (3-NP) under the same conditions
(Supporting Information, Figures S5 and S6). The peaks at
400 (for 2-NP) and 420 (for 3-NP) nm disappeared;
meanwhile, the new peaks at 279 and 285 nm attributed to
2-aminophenol (2-AP) and 3-aminophenol (3-AP) appeared,
and no more changes in the UV−vis spectra have been
observed in 30 min, indicating the reactions were finished. On
the basis of the above observation, 1 can be considered as a
highly effective Au NP-based heterogeneous catalyst.
Catalytic Activity Test of 1. The catalytic activity of the
encapsulated Au NPs in 1 was preliminarily examined by the
reduction reaction of 4-NP. The catalytic reduction reaction of
4-NP is not only an effective approach for degradation toxic
organic pollutant, but also a model reaction for evaluation of Au
NPs-loaded catalysts.12 The reaction was carried out in the
presence of a hydrogen source, NaBH4. Initially, the 4-NP
solution has a light yellow color, which turned dark yellow
upon the addition of NaBH4 because of the generation of 4-
nitrophenolate. Notably, with the use of 1 (0.1 mol %), the
yellow color gradually faded away and completely vanished in
about 30 min, indicating that the reduction of 4-NP to 4-AP
was finished. Besides naked-eye detectable color change, the
reaction progress was monitored by UV−vis spectra. As
indicated in Figure 3, the adsorption of 4-NP at 400 nm
Oxidation of Benzyl Alcohol in Air. Reaction Conditions
and Leaching Test. It is well-known that the selective catalytic
oxidation of benzyl alcohols to benzaldehydes is one of the
most important organic transformations in modern synthetic
chemistry and in the industry, so the development of high
performance and stable heterogeneous catalysts are very
significant.13 The selective aerobic oxidation of benzyl alcohol
was chosen as a model reaction to evaluate the catalytic activity
of 1 and optimize the reaction conditions. Reactions were
carried out in air (with 1, 3 mol % Au) and base-free
conditions.
As shown in Table 1, weak polar toluene (entries 3−5,
Supporting Information, Figures S9−S15) instead of water
Table 1. Optimization of the Benzyl Alcohol Oxidation
a
Reaction Conditions
entry T (°C)
solvent
t (h) conversion (%) benzaldehyde (%)
1
2
3
4
5
95
70
H2O
20
20
20
20
20
8
12
37
63
98
>99
>99
>99
>99
>99
CH3CN
toluene
toluene
toluene
60
90
110
a
Reaction conditions: air, benzyl alcohol (0.20 mmol), 1 (13 mg, 3
mol % Au), solvent (3 mL).
(entry 1, Supporting Information, Figure S7) and acetonitrile
(entry 2, Supporting Information, Figure S8) is an ideal solvent
for this aerobic selective oxidation. The influence of temper-
ature on the catalytic performance of the present reaction
system was also investigated in toluene. With the increase of
the reaction temperature from 60 to 110 °C, the conversion of
benzaldehyde was significantly enhanced (Supporting Informa-
tion, Figures S9−S15). The excellent conversion (98%) and
selectivity (>99%) were achieved when the reaction was carried
out at 110 °C. The total number (TON) and turnover
frequency (TOF) for oxidation of benzyl alcohol are 32.67 and
2.18 h−1, respectively, under the investigated conditions. It is
noteworthy that the Au NPs free Cu(II)-MOF showed almost
no conversion (only 3%) of benzyl alcohol (Supporting
Information, Figure S16), demonstrating the requirement of
the Au NPs to perform this aerobic oxidation.
Figure 3. Representative time-dependent UV−vis adsorption spectra
for the reduction of 4-NP over 1 in aqueous solution at room
temperature. The color change of 4-NP reduction with 1 and NaBH4
in aqueous media.
rapidly decreased with a concomitant increase in the peak at
300 nm, and no change in UV−vis spectra was observed in 30
min. On the other hand, the isosbestic point between the two
peaks further confirmed a direct conversion of 4-NP to 4-AP
under the reaction conditions. Since the concentration of
NaBH4 is much higher than those of 4-NP and 1, and it is
reasonable to assume that the concentration of NaBH4 remains
constant during the reaction. The TON and TOF for the
reduction of 4-NP reaction are 1000 and 2000 h−1. After the
reaction, the catalyst can be readily recovered by centrifugation.
The HRTEM analysis and XRPD patterns demonstrated that
The relationship between conversion and reaction time is
shown in Figure 4. The initial conversion of benzaldehyde is
continuously increased, and the maximum yield (98%) was
observed at 15 h (Supporting Information, Figure S15). In
C
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can be a beneficial complement for the MOFs to heterogeneous
catalysts for the selective aerobic benzyl alcohol oxidation.
Recyclability Studies. The recyclability of 1 was examined.
After each catalytic run, the solid catalyst was easily collected by
centrifugation, washed with acetonitrile, dried at 90 °C, and
reused in the next run under the same conditions. Yields of
between 98% and 94% were obtained within the five recycling
runs with the excellent selectivity (>99%) (Figure 5a and
Supporting Information, Figures S17−S20). The XRD patterns
of 1 and that after reused for five catalytic cycles indicated that
the structural integrity of the Cu(II)-MOF was well-preserved,
indicating the Cu(II)-MOF herein is an ideal support for
uploading Au NPs (Figure 5b). The diffraction at 38.2° related
to Au NPs gradually appeared with the increase of catalytic runs
which might be caused by intensity decrease of the MOF peaks
after reaction. On the other hand, HRTEM image of used 1
only shows slight aggregation of Au NPs (Figure 5c), which
does not significantly affect the activity of the catalyst within
five catalytic cycles. This result demonstrates that the Cu(II)-
MOF can effectively prevent the uploaded Au NPs from
sintering and aggregation in the MOF matrix even at higher
reaction temperature. In addition, the elemental maps of the Au
and Cu images confirm Au NPs highly dispersed in Cu(II)-
MOF matrix (Figure 5d, and Supporting Information, Figure
S21) and the ICP measurement indicated that the Au content
in 1 is basically unchanged (9.24%) even after five catalytic
runs.
Figure 4. Reaction time examination and leaching test for benzyl
alcohol reaction based on 1. Reaction conditions: air, 1 (3 mol % Au),
benzyl alcohol (0.21 mmol), and toluene (3 mL). The solid catalyst
was filtrated from the reaction solution after 6 h, whereas the filtrate
was transferred to a new vial and reaction was carried out under the
same conditions for an additional 14 h.
order to gain insight into the heterogeneous nature of 1, the
hot leaching test was carried out. As indicated in Figure 4, no
further reaction took place without 1 after ignition of the
oxidation reaction at 6 h. This finding demonstrated that 1
exhibits a typical heterogeneous catalyst nature.
Compared to most other reported Au NPs-loaded catalysts, 1
herein exhibits better conversion and selectivity for the selective
aerobic benzyl alcohol oxidation. As shown in Table 2, most
reported benzyl alcohol oxidations are carried out in O2,
sometimes with higher pressure, instead of in air. In addition,
Au@Cu(II)-MOF herein shows a good reusability compared to
many other Au catalysts loaded on inorganic or inorganic−
organic composite supports. So Au@Cu(II)-MOF (1) herein
After that, we investigated the catalytic activity of 1 for the
selective aerobic oxidation of a series of other substituted
Table 2. Summary of the Reported Benzyl Alcohol to Benzaldehydes Oxidation Reactions Using Au NPs as the Heterogeneous
Catalysts
entry
catalyst
Au NPs-rGO
condition
O2, 130 °C
run
conv (%)
selectivity (%)
ref.
1
1
4
3
1
1
3
2
1
1
4
3
4
1
6
1
1
4
9
5
5
3
1
2
3
1
1
1
5
75
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
2
Au/MgO
O2, 120 °C
visible light
55.5
72.93
42
95.0
96.78
100
95
3
Au/HT-3
4
Au (45 nm)/TiO2
IMAuH
O2, 120 °C
O2, 80 °C
O2, 90 °C
O2, 80 °C
10 atm, O2, 100 °C
10 atm, O2, 110 °C
1.0 MPa, O2, 80 °C
O2, 140 °C
6 atm, O2, 100 °C
solvent-free aerobic oxidation
308 K, air
5
42.9
43.22
85.7
15
6
Au/Mn-CeO2
Au/CuOco
99
7
>99
100
66
8
Au/MgO
9
Au/Mg-500
78
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
Au/NaY
94.4
49.0
84.3
21.90
99
magnetitite−silica−gold
Au/Fe3O4@SiO2
Au/SiO2@Al2O3
Au/MIL-101
Au@ZIF-8
97.1
95
72.32
99
O2, 80 °C
O2, 80 °C
air flow, 80 °C
O2 flow, 80 °C
O2, 100 °C
81
98
Au/ZnO@MOF-5
Au/PMAMIL-101
Au@UiO-66
Au@UiO-66-NH2
Au/HT
74
60
100
100
64
94
393 K
89
99
99
Au/NiAl-LDH-F-36
Au/TiO2
O2, 100 °C
53
TBHP, 94 °C
5 bar O2, 80 °C
O2 (0.2 MPa), 120 °C
steady-state liquid phase
O2 (3 mL/min), 393 K
water, 60 °C
50
Au101/TiO2−O2
Au/MnO2
96
73
8.8
98.5
43.4
99
Au/SiO2
11.3
99
Au/HT
Au−C
Au@Cu(II)-MOF
99
99
toluene, 110 °C, air
>95
>99
this work
D
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Figure 5. Recycling test. (a) The conversion and selectivity obtained at 15 h in repeated runs of the benzyl alcohol aerobic oxidation promoted by 1
(air, 110 °C, 3 mol % Au). (b) Corresponding XRPD patterns. (c) HRTEM image after five catalytic runs. (d) SEM image and SEM-EDX elemental
mapping of 1 after five catalytic runs.
benzyl alcohols (Table 3). We found that our 1 exhibits high
reactivity with excellent conversion toward other kinds of
temperature; the GC analysis indicated that the condensation
reaction was finished in 7 h to afford 2-benzylidenemalononi-
trile as the expected product with the excellent conversion
(98%) and selectivity (99%) (Supporting Information, Figure
S28). On the basis of this result and the above observation, 1
could be a bifunctional catalyst to promote benzyl alcohol
oxidation and the following Knoevenagel condensation in due
succession.
Table 3. Oxidation Reactions of Benzyl Alcohols with
a
Different Substituted Groups Catalyzed by 1
When a toluene solution (2 mL) of benzyl alcohol (0.3
mmol) in the presence of 1 (3 mol %) was heated at 110 °C for
15 h, a MeOH solution (2 mL) of malononitrile (0.34 mmol)
was added to the above system after cooling down to room
temperature. The mixture was stirred for an additional 7 h at
room temperature to afford benzylidenemalononitrile with
excellent conversion (98%) and selectivity (99%). The TON
and TOF for the oxidation−Knoevenagel reaction are 32.67
and 1.48 h−1 (Supporting Information, Figure S29). Again, the
diffractions (2θ value at 38.2°) of Au NP species were detected
from powder XRD patterns after oxidation−Knoevenagel
reaction with the decrease of crystallinity of the Cu(II)-MOF
support after three runs (Figure 6a, Supporting Information,
Figures S30−S31). HRTEM analysis revealed that the mean
diameter of the Au NPs slightly increases (<5 nm) after three
runs (Figure 6b), which is attributed to the slight aggregation of
Au NPs. This could be the reason for the slight decrease in the
overall conversion in the second and third runs (Figure 6c,
Supporting Information, Figure S32). However, high dispersion
of the Au NPs was still kept in the Cu(II)-MOF matrix after
three catalytic runs (Figure 6d).
a
Reaction conditions: air, benzyl alcohols with different substituted
groups (0.20 mmol), 1 (13 mg, 3 mol % Au), toluene (3 mL), 110 °C.
benzyl alcohols regardless of the types and position of the
substituted functional groups. Notably, the reaction selectivity
toward benzaldehydes is almost 100% in all cases (Supporting
Information, Figures S22−S27).
Benzyl Alcohol Oxidation−Knoevenagel Reaction.
Besides aerobic oxidation, the catalytic behavior of 1 for the
Knoevenagel reaction, which is an important C−C coupling
reaction and widely used in the synthesis of fine chemicals, was
also investigated. In a typical reaction, a MeOH/toluene mixed
solvent solution of benzaldehyde and malononitrile (1:1.2,
molar ratio) in the presence of 1 (3 mol %) was stirred at room
To expand the applicability of 1 for successive selective
oxidation−Knoevenagel reaction, the examination of 1 for
various alcohols other than benzyl alcohols in toluene/MeOH
mixed solvent system was performed under the same
conditions. As indicated in Table 4, 1 was also effective in
facilitating oxidation−condensation reactions to afford corre-
sponding substituted benzylidenemalononitriles based on
various other benzyl alcohols in a stepwise way (Supporting
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Figure 6. Recycling test. (a) The XRPD patterns of Cu(II)-MOF and 1 after three catalytic runs. (b) HRTEM image after three catalytic runs. (c)
Conversion and selectivity obtained in repeated runs of the benzyl alcohol oxidation−knoevenagel reaction promoted by 1 (air, 3 mol % Au). (d)
SEM image and SEM-EDX elemental mapping of 1 after three catalytic runs.
for selective oxidation−Knoevenagel condensation of various
aromatic alcohol compounds.
Table 4. Oxidation−Knoevenagel Reactions of Benzyl
Alcohols with Different Substituted Groups Catalyzed by
Au@Cu(II)-MOF (1)
a
CONCLUSION
■
In summary, a new Au NPs-loaded 1 was prepared via solution
impregnation. The obtained Au NPs embedded 1 herein
exhibits a typical bifunctional heterogeneous catalytic nature
and readily promotes benzyl alcohol oxidation and condensa-
tion reactions in a stepwise manner. The results herein could be
an alternative useful approach for construction of a variety of
high performance bifunctional or even multifunctional solid
catalysts for a broad scope of organic reactions.
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.6b00925.
XPS spectra, ESR spectra, CO2 adsorption properties,
HRTEM and SEM-EDS measurements, UV−vis spectra,
GC analysis for oxidation reactions, and oxidation−
Knoevenagel reactions (PDF)
AUTHOR INFORMATION
Corresponding Authors
*E-mail: gongjchen@126.com.
*E-mail: yubindong@sdnu.edu.cn.
■
a
Reaction conditions: first step, toluene solution (2 mL) of benzyl
Notes
alcohols with different substituted groups (0.3 mmol), 1 (3 mol %
Au), 110 °C, 15 h; second step, MeOH solution (2 mL) of
malononitrile (0.34 mmol), rt, 7 h.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We are grateful for financial support from NSFC (Grant nos.
21475078, 21271120, 21301109, and 21501111), 973 Program
(Grant nos. 2012CB821705 and 2013CB933800), Taishan
Scholar’s Construction Project, Reward Fund for Outstanding
Young and Middle Aged Scientists of Shandong Province (no.
BS2012CL032), and Jinan Science and Technology Bureau
(OUT_06623).
Information, Figure S33). Compared to benzyl alcohol, we
found that benzyl alcohols with either a CH3 or F group gave
lower overall conversions (88−89%), while overall conversions
for the rest of the reaction systems are comparable to that of
benzyl alcohol. All reaction systems, however, provide the high
selectivity larger than 99%, indicating that 1 herein can be used
F
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(14) Sharma, P.; Darabdhara, G.; Reddy, T. M.; Borah, A.;
Bezboruah, P.; Gogoi, P.; Hussain, N.; Sengupta, P.; Das, M. R.
Catal. Commun. 2013, 40, 139−144.
REFERENCES
■
(1) (a) Mizuno, N.; Misono, M. Chem. Rev. 1998, 98, 199−218.
(b) Coper
́
et, C.; Comas-Vives, A.; Conley, M. P.; Estes, D. P.;
(15) Choudhary, V. R.; Dumbre, D. K. Catal. Commun. 2011, 13,
82−86.
Fedorov, A.; Mougel, V.; Nagae, H.; Nunez-Zarur, F.; Zhizhko, P. A.
́
̃
Chem. Rev. 2016, 116, 323−421. (c) Jia, M. Q.; Bandini, M. ACS Catal.
2015, 5, 1638−1652.
(16) Yu, J.; Li, J. Y.; Wei, H. L.; Zheng, J. W.; Su, H. Q.; Wang, X. J. J.
Mol. Catal. A: Chem. 2014, 395, 128−136.
(2) (a) Schwarz, J. A.; Contescu, C.; Contescu, A. Chem. Rev. 1995,
95, 477−510. (b) Dahl, M.; Liu, Y. D.; Yin, Y. D. Chem. Rev. 2014,
114, 9853−9889. (c) Zaera, F. Chem. Soc. Rev. 2013, 42, 2746−2762.
(d) Aijaz, A.; Xu, Q. J. Phys. Chem. Lett. 2014, 5, 1400−1411.
(3) (a) Sun, L. B.; Liu, X. Q.; Zhou, H. C. Chem. Soc. Rev. 2015, 44,
5092−5147. (b) Feng, J. T.; He, Y. Y.; Liu, Y. N.; Du, Y. Y.; Li, D. Q.
Chem. Soc. Rev. 2015, 44, 5291−5319. (c) Chughtai, A. H.; Ahmad, N.;
Younus, H. A.; Laypkov, A.; Verpoort, F. Chem. Soc. Rev. 2015, 44,
6804−6849. (d) Stratakis, M.; Garcia, H. Chem. Rev. 2012, 112, 4469−
4506. (e) Tang, H. L.; Wei, J. K.; Liu, F.; Qiao, B. T.; Pan, X. L.; Li, L.;
Liu, J. Y.; Wang, J. H.; Zhang, T. J. Am. Chem. Soc. 2016, 138, 56−59.
(f) Min, B. K.; Friend, C. M. Chem. Rev. 2007, 107, 2709−2724.
(g) Liu, X.; He, L.; Liu, Y. M.; Cao, Y. Acc. Chem. Res. 2014, 47, 793−
804. (h) Wittstock, A.; Baumer, M. Acc. Chem. Res. 2014, 47, 731−739.
(i) Villa, A.; Dimitratos, N.; Chan-Thaw, C. E.; Hammond, C.; Prati,
L.; Hutchings, G. J. Acc. Chem. Res. 2015, 48, 1403−1412.
(4) (a) Liu, X.; He, L.; Liu, Y. M.; Cao, Y. Acc. Chem. Res. 2014, 47,
793−804. (b) Zhang, Y.; Cui, X. J.; Shi, F.; Deng, Y. Q. Chem. Rev.
2012, 112, 2467−2505.
(17) Sreedhala, S.; Sudheeshkumar, V.; Vinod, C. P. Catal. Today
2015, 244, 177−183.
(18) Ma, C. Y.; Cheng, J.; Wang, H. L.; Hu, Q.; Tian, H.; He, C.;
Hao, Z. P. Catal. Today 2010, 158, 246−251.
(19) Mandal, S.; Santra, C.; Bando, K. K.; James, O. O.; Maity, S.;
Mehta, D.; Chowdhury, B. J. Mol. Catal. A: Chem. 2013, 378, 47−56.
(20) Wang, H.; Fan, W. B.; He, Y.; Wang, J. G.; Kondo, J. N.;
Tatsumi, T. J. Catal. 2013, 299, 10−19.
(21) Costa, V. V.; Estrada, M.; Demidova, Y.; Prosvirin, I.;
Kriventsov, V.; Cotta, R. F.; Fuentes, S.; Simakov, A.; Gusevskaya,
E. V. J. Catal. 2012, 292, 148−156.
(22) Estrada, M.; Costa, V. V.; Beloshapkin, S.; Fuentes, S.; Stoyanov,
E.; Gusevskaya, E. V.; Simakov, A. Appl. Catal., A 2014, 473, 96−103.
(23) Zhou, L. P.; Yu, W. J.; Wu, L.; Liu, Z.; Chen, H. J.; Yang, X. M.;
Su, Y. L.; Xu, J. Appl. Catal., A 2013, 451, 137−143.
(24) Kokate, M.; Dapurkar, S.; Garadkar, K.; Gole, A. J. Phys. Chem.
C 2015, 119, 14214−14223.
(25) Oliveira, R. L.; Kiyohara, P. K.; Rossi, L. M. Green Chem. 2010,
12, 144−149.
(5) (a) Corma, A.; García, H.; Xamena, F. X. L. Chem. Rev. 2010,
110, 4606−4655. (b) Cook, T. R.; Stang, P. J. Chem. Rev. 2015, 115,
7001−7045. (c) Durot, S.; Taesch, J.; Heitz, V. Chem. Rev. 2014, 114,
8542−8578. (d) Li, M.; Li, D.; O’Keeffe, M.; Yaghi, O. M. Chem. Rev.
2014, 114, 1343−1370. (e) O’Keeffe, M.; Yaghi, O. M. Chem. Rev.
2012, 112, 675−702. (f) Chughtai, A. H.; Ahmad, N.; Younus, H. A.;
Laypkov, A.; Verpoort, F. Chem. Soc. Rev. 2015, 44, 6804−6849.
(6) (a) Wang, S. S.; Yang, G. Y. Chem. Rev. 2015, 115, 4893−4962.
(b) Liu, Y. Y.; Zhang, W. N.; Li, S. Z.; et al. Chem. Mater. 2014, 26,
1119−1125. (c) Chen, Y. Z.; Zhou, Y. X.; Wang, H. W.; Lu, J. L.;
Uchida, T.; Xu, Q.; Yu, S. H.; Jiang, H. L. ACS Catal. 2015, 5, 2062−
2069. (d) Liu, Y. L.; Tang, Z. Y. Adv. Mater. 2013, 25, 5819−5825.
(7) (a) Jiang, H. L.; Akita, T.; Ishida, T.; Haruta, M.; Xu, Q. J. Am.
Chem. Soc. 2011, 133, 1304−1306. (b) Gole, B.; Sanyal, U.; Banerjee,
R.; Mukherjee, P. S. Inorg. Chem. 2016, 55, 2345−2354. (c) Jiang, H.
L.; Liu, B.; Akita, T.; Haruta, M.; Sakurai, H.; Xu, Q. J. Am. Chem. Soc.
2009, 131, 11302−11303.
(26) Li, Z.; Ji, Y.; Cadigan, C.; Richards, R. M. Catal. Sci. Technol.
2014, 4, 2520−2525.
(27) Liu, H. L.; Liu, Y. Y.; Li, Y. W.; Tang, Z. Y.; Jiang, H. F. J. Phys.
Chem. C 2010, 114, 13362−13369.
(28) Esken, D.; Turner, S.; Lebedev, O. I.; Van Tendeloo, G. V.;
Fischer, R. A. Chem. Mater. 2010, 22, 6393−6401.
(29) Muller, M.; Turner, S.; Lebedev, O. I.; Wang, Y. M.; van
Tendeloo, G.; Fischer, R. A. Eur. J. Inorg. Chem. 2011, 2011, 1876−
1887.
(30) Juan-Alcaniz, J.; Ferrando-Soria, J.; Serra-Crespo, I. L.; Skupien,
P. E.; Santos, V. P.; Pardo, E.; Xamena, F. X. L. I.; Kapteijn, F.;
Gascon, J.; Luz, I. J. Catal. 2013, 307, 295−304.
(31) Zhu, J.; Wang, P. C.; Lu, M. Appl. Catal., A 2014, 477, 125−131.
(32) Luan, Y.; Qi, Y.; Gao, H. Y.; Zheng, N. N.; Wang, G. J. Mater.
Chem. A 2014, 2, 20588−20596.
(33) Fang, W. H.; Chen, J. S.; Zhang, Q. H.; Deng, W. P.; Wang, Y.
Chem. - Eur. J. 2011, 17, 1247−1256.
(34) Du, Y. Y.; Jin, Q.; Feng, J. T.; Zhang, N.; He, Y. F.; Li, D. Q.
Catal. Sci. Technol. 2015, 5, 3216−3225.
(8) (a) Chen, G.-J.; Wang, J.-S.; Jin, F.-Z.; Liu, M.-Y.; Zhao, C.-W.;
Li, Y.-A.; Dong, Y.-B. Inorg. Chem. 2016, 55, 3058−3064. (b) Li, Y.-A.;
Yang, S.; Liu, Q.-K.; Chen, G.-J.; Ma, J.-P.; Dong, Y.-B. Chem.
Commun. 2016, DOI: 10.1039/C6CC01194B. (c) Zhao, C.-W.; Li, Y.-
A.; Wang, X.-R.; Chen, G.-J.; Liu, Q.-K.; Ma, J.-P.; Dong, Y.-B. Chem.
Commun. 2015, 51, 15906−15909.
(35) Enache, D. I.; Edwards, J. K.; Landon; Solsona-Espriu, P. B.;
Carley, A. F.; Herzing, A. A.; Watanabe, M.; Kiely, C. J.; Knight, D. W.;
Hutchings, G. J. Science 2006, 311, 362−365.
(36) Adnan, R. H.; Andersson, G. G.; Polson, M. I. J.; Metha, G. F.;
Golovko, V. B. Catal. Sci. Technol. 2015, 5, 1323−1333.
(37) Alhumaimess, M.; Lin, Z. J.; He, Q.; Lu, L.; Dimitratos, N.;
Dummer, N. F.; Conte, M.; Taylor, S. H.; Bartley, J. K.; Kiely, C. J.;
Hutchings, G. Chem. - Eur. J. 2014, 20, 1701−1710.
(38) Chen, K.; Wu, H. T.; Hua, Q.; Chang, S. J.; Huang, W. X. Phys.
Chem. Chem. Phys. 2013, 15, 2273−2277.
(9) Chen, G. J.; Wang, J. S.; Jin, F. Z.; Liu, M. Y.; Zhao, C. W.; Li, Y.
A.; Dong, Y. B. Inorg. Chem. 2016, 55, 3058−3064.
(10) (a) Feng, Y. H.; Yin, H. B.; Gao, D. Z.; Wang, A. L.; Shen, L. Q.;
Meng, M. J. J. Catal. 2014, 316, 67−77. (b) Cuenya, B. R.; Baeck, S.
H.; Jaramillo, T. F.; McFarland, E. W. J. Am. Chem. Soc. 2003, 125,
12928−12934. (c) Liu, L. C.; Gu, X. R.; Cao, Y.; Yao, X. J.; Zhang, L.;
Tang, C. J.; Gao, F.; Dong, L. ACS Catal. 2013, 3, 2768−2775.
(d) Jaramillo, T. F.; Baeck, S.; Cuenya, B. R.; McFarland, E. W. J. Am.
Chem. Soc. 2003, 125, 7148−7149.
(39) Chen, J. S.; Fang, W. H.; Zhang, Q. H.; Deng, W. P.; Wang, Y.
Chem. - Asian J. 2014, 9, 2187−2196.
(40) Wang, S.; Wang, J.; Zhao, Q. F.; Li, D. D.; Wang, J. Q.; Cho, M.
Y.; Cho, H.; Terasaki, O.; Chen, S. J.; Wan, Y. ACS Catal. 2015, 5,
797−802.
(11) Liu, L. C.; Gu, X. R.; Cao, Y.; Yao, X. J.; Zhang, L.; Tang, C. J.;
Gao, F.; Dong, L. ACS Catal. 2013, 3, 2768−2775.
(12) (a) Gangula, A.; Podila, R.; M, R.; Karanam, L.; Janardhana, C.;
Rao, A. Langmuir 2011, 27, 15268−15274. (b) Zheng, G. C.;
́ ́
Polavarapu, L.; Liz-Marzan, L. M.; Pastoriza-Santos, I.; Perez-Juste, J.
Chem. Commun. 2015, 51, 4572−4575. (c) Sharma, B.; Mandani, S.;
Sarma, T. K. J. Mater. Chem. B 2014, 2, 4072−4079. (d) Evangelista,
V.; Acosta, B.; Miridonov, S.; Smolentseva, E.; Fuentes, S.; Simakov, A.
Appl. Catal., B 2015, 166, 518−528.
(13) Pina, C. D.; Falletta, E.; Rossi, M. Chem. Soc. Rev. 2012, 41,
350−369.
G
DOI: 10.1021/acs.inorgchem.6b00925
Inorg. Chem. XXXX, XXX, XXX−XXX