Highly efficient metal organic framework (MOF)-based copper catalysts for the base-free aerobic oxidation of various alcohols

Article abstract of DOI:10.1039/c6ra28743c

Copper (Cu) containing metal organic frameworks (MOFs) are found to be highly efficient heterogeneous catalysts for oxidation of various alcohols. A wide range of alcohols, including alcohols containing inactive hetero-aryl and long-chain alkyl units, are

Full text of DOI:10.1039/c6ra28743c

RSC Advances
View Article Online
View Journal | View Issue
PAPER
Highly efficient metal organic framework (MOF)-
based copper catalysts for the base-free aerobic
oxidation of various alcohols†
Cite this: RSC Adv., 2017, 7, 17806
Abu Taher, Dong Wook Kim and Ik-Mo Lee*
Copper (Cu) containing metal organic frameworks (MOFs) are found to be highly efficient heterogeneous
catalysts for oxidation of various alcohols. A wide range of alcohols, including alcohols containing inactive
hetero-aryl and long-chain alkyl units, are selectively converted into their corresponding products. The
catalytic efficiency of the Cu containing MOFs, along with the co-catalyst 2,2,6,6-tetramethyl-piperidyl-
1
-oxy (TEMPO), was demonstrated by the high conversion of the reactants with 100% selectivity under
Received 27th December 2016
Accepted 5th March 2017
base-free conditions. The use of an inexpensive copper containing catalyst, the broad substrate scope,
and the open air conditions and absence of base additive make this protocol very practical. The catalyst
maintained a unique structural framework and it could be reused at least five times without significant
loss of activity.
DOI: 10.1039/c6ra28743c
rsc.li/rsc-advances
8
waste disposal problems, as well as separation difficulties for
catalytic recycling. Importantly, the presence of a base is not
Introduction
9
In recent years, metal organic frameworks (MOFs) have been desirable from an industrial point of view due to corrosion, and
actively investigated and successfully used for different it can adversely affect the stereoselectivity and cannot be used
1
10
purposes in various branches of the pure and applied sciences.
for a base-sensitive alcohol, a fact that is very important in the
MOFs are three dimensional porous structures made of metal pharmaceutical industry. Interestingly, some Cu(II) complexes
ions or clusters linked by organic molecules. The most attractive can catalyze alcohol oxidation by using TEMPO as a co-catalyst
11
features of MOFs are their extremely high surface areas, as well without base additives. Unfortunately, these copper catalysts
1c
as their tunable pore size and topology. These key features, are still homogeneous and are difficult to separate aer the
along with other characteristics, make them excellent candi- reaction.
dates for a wide range of applications in heterogeneous catal-
ysis. These catalysts can be readily recovered and reused,
On the other hand, the oxidation of alcohols to their corre-
sponding carbonyl compounds is one of the most important
2
3
which is highly desirable for cost effectiveness and sustain- reactions in organic synthesis, due to the wide-ranging utility of
ability considerations in organic synthesis. In addition, copper these carbonyl products as essential precursors and interme-
4
(
Cu), as a classical transition metal, is considered to be one of diates for the development of many drugs, fragrances, and ne
12
the most attractive catalysts for use in the oxidation of alcohols chemicals. It traditionally requires numerous stoichiometric
due to its abundance of resources, low cost, non-toxic properties oxidants, and most of these alcohols are oxidized by toxic,
and high catalytic efficiency. In particular, Cu(II) complexes corrosive and expensive oxidants, such as DMSO-coupled
13
14
combined with TEMPO have been proven to have good catalytic reagents, hypervalent iodines, and heavy-metal reagent-
5
12a,b
performance for alcohol oxidation. Up to now, even though s.
Unfortunately, these reactions result in large quantities of
many efficient Cu(II)/TEMPO catalytic systems have been re- toxic materials and call for the use of stoichiometric quantities
6
ported, there are only a limited number of studies on MOF- of moisture-sensitive, unrecoverable and expensive chemical
7
based Cu(II)/TEMPO systems for alcohol oxidation. However, reagents. Importantly, satisfactory results were obtained in only
Cu/TEMPO catalysts oen require a large excess of base addi- limited cases, in which a large excess of additives was required.
tives, which always results in a carboxylate product and basic Therefore, the development of potential catalysts for oxidation
under mild conditions is highly desirable, but challenging, and
a hot topic in both green chemistry and current organic
Department of Chemistry, Inha University, Incheon 402-751, South Korea. E-mail: synthesis. Herein, we report a highly efficient and reusable
imlee@inha.ac.kr; Fax: +82-32-867-5604; Tel: +82-32-860-7682
Cu(II)/MOF (3) composite assisted by TEMPO, as the co-catalyst,
†
Electronic supplementary information (ESI) available: Synthetic details, digital
for the selective oxidation of various alcohols to their corre-
sponding products under mild conditions, without the assis-
tance of any base additives (Scheme 1).
1
images, H NMR spectra, EDS spectrum, N
2
adsorption–desorption isotherms,
pore volume vs. diameter curve, XPS spectra, X-ray powder diffraction, effect of
catalyst loading and FTIR spectrum. See DOI: 10.1039/c6ra28743c
17806 | RSC Adv., 2017, 7, 17806–17812
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
2
Scheme 1 Post-functionalization route of the Cu(II)/MOF-NH (3) composite.
18
formation of the Cu-amine functionalized-MOF complex.
Furthermore, the characteristic XRD peak of Cu (112) at 2q ¼
Results and discussion
ꢀ
2+
The azide-functionalized MOF-N
reaction of an organic linker, containing the azide functional which means that the structure of the amine-functionalized
3
(1) was prepared from the 12.6 is assigned due to the insertion of Cu in 2 (Fig. 2b),
2
+
group, with zinc nitrate hexahydrate in DEF, as described MOF has coordinated with Cu , and a new complex has been
15
19
earlier. Subsequently, we tried to reduce the azide groups formed that is in accordance with earlier reports. In addition,
using triphenylphosphine (PPh
) in DEF, as described in our it is found that aer the yellow amine-functionalized MOF
earlier reports, and the detailed synthesis and characterization powders were added into the green copper(II) chloride con-
3
16
procedure of MOF-NH (2) is presented elsewhere. The FTIR taining ethanoic solution, the solution turned colourless
2
and XRD spectra of the as-synthesized compounds 1 and 2 are (Fig. 1f), which further conrmed the likely formation of the
similar to those of the dened compound, as shown in Fig. S2a MOF copper complex under the dened conditions. The XRD
and b, respectively (ESI†). Moreover, an elemental analysis of 1 pattern of the reacted 3 crystals exhibited no apparent changes
and 2 was in good agreement with their formula unit (Table S1, of the pattern from the starting 2, as shown in Fig. 2b, and the
ESI†). The catalyst 3 was synthesized by loading the Cu
precursor, copper(II) chloride, into 2 in ethanol. The colour of
the solution changed from green to colourless (Fig. 1f). Aer
separating the MOF crystal by ltration, we dried the crystal
ꢀ
under vacuum at 80 C to afford 3 as a green solid (Fig. S3, ESI†).
The copper complex was anchored on the amine-functionalized
17
MOF layer through coordination, and the presence of the Cu
complexes was examined by FTIR, HRSEM, TEM, XPS, EDS, TGA
and ICP spectroscopic analyses. The loading of Cu in MOF-NH
2
was 5.02 wt%, which was measured by inductively coupled
plasma atomic emission spectroscopy (ICP-AES) and exactly
matched the calculated value. The morphology of 3 was
observed by SEM and TEM analyses. The HRSEM images at
different magnications are shown in Fig. 1a–c, and the TEM
image of the catalyst 3 is shown in Fig. S4, (ESI†). The SEM, and
corresponding elemental mapping by energy-dispersive X-ray
spectroscopic analysis (EDS) of 3, demonstrated the homoge-
neous distribution of copper and chloride ions in the amine-
functional MOF (Fig. 1d and e). The successful loading of Cu
in 2 was conrmed by EDS spectroscopy. As shown in Fig. S5
(
ESI†), a clear Cu peak was resolved when we probed the
selected area 1 on the Cu loaded MOF. Furthermore, the XPS
survey spectra of 3 conrmed the existence of Cu and Cl in 3
Fig. S6b†). It can be remarked that the FTIR stretching band of
2
(
ꢁ
1
the catalyst 3 at 1656 cm is decreased, which may be attrib-
uted to the coordination interaction with CuCl (Fig. 2a). In
particular, the amino group related peaks at 3373 cm and
3
3
2
ꢁ1
Fig. 1 SEM images of the surface of 3 at different magnifications (scale
bars are shown at bottom left or right) for 5.00 mm, 1.00 mm and 300
ꢁ
1
ꢁ1
290 cm shied to lower wave numbers at 3255 cm and
ꢁ1
158 cm , respectively, in 3 because of the electron donation mm respectively (a, b & c); the corresponding quantitative EDS mapping
from the amino group to the Cu(II) center, which resulted in the of Cu (d) and Cl (e); the color of the solution of catalyst 3 before and
after reaction (f).
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 17806–17812 | 17807

View Article Online
RSC Advances
Paper
2
2
(
Fig. 2f). Generally, the characteristic shakeup satellite is
9
peculiar for the Cu(II) species, which relates to the d congu-
ration of Cu. Whereas, in the case of Cu(I), no satellite peaks can
be observed because the screening via a charge transfer into the
d states is not possible due to the presence of a completely lled
22
d shell.
The catalytic activity of the prepared catalyst 3 was tested
with a representative set of primary and secondary benzylic and
aliphatic alcohols. Initially, to investigate the catalytically active
components of the CuCl /MOF-NH composite, a series of
2
2
controlled experiments were carried out under exactly the same
ꢀ
reaction conditions. The reactions were performed at 70 C, and
under atmospheric pressure, using air as the oxidant under
base-free conditions, and the results are summarized in Table 1.
As shown in Table 1 (entry 1), 3 was an active catalyst for this
reaction and 100% conversion (GC yield) of benzyl alcohol to
benzaldehyde was achieved. On the contrary, 1 and 2 gave no
conversion of benzyl alcohol (entries 2–4) in the absence of any
catalyst, which conrmed the oxidation of benzyl alcohol to
7
benzaldehyde is catalysed by Cu. In addition, when only CuCl2
or a mixture of 2 and CuCl
2
was used, relatively poor yields were
obtained (entries 5 and 6). According to the literature, this may
23
Fig. 2 (a) FTIR and (b) XRD spectra of compounds 2 and 3; TGA of
compounds 2 and 3 (c); XPS spectra of the nitrogen N 1s peaks for
compound 2 (d) and for compound 3 (e); Cl S1 peaks for 3 (e, inset);
XPS spectra of Cu 2p peaks of compound 3 (f).
be due to the absence of coordinating ligands. Importantly,
the results demonstrate that the connected ligand between the
amine functionalized-MOF and the Cu moieties promoted the
catalytic reaction of aerobic oxidation of benzyl alcohols under
the dened conditions.
In order to obtain optimized catalytic performance, we
investigated the effect of the solvent and found that CH CN was
3
C–O band was still maintained along with the Zn metal (Fig. S6a
and b, ESI†), which indicated that the modied MOF framework
was constructed by zinc ions and carboxylate anions with
a similar structural framework. Thermogravimetric analysis
the best solvent for this reaction (Fig. 3a). It is signicant to note
that 3 showed poor catalytic activity and the crystal structure
deformed when water was used as the solvent (Fig. S9, ESI†).
Then, in a quick survey of the bases, the conversion of alcohol
without using any base was similar to that when using K CO as
(
TGA) indicates that 3 is thermally stable, and it shows thermal
stability that is identical to the parent compound (Fig. 2c).
Fig. S7 (ESI†) shows the N adsorption–desorption isotherm
2
3
2
a base (Fig. 3b). In this catalytic system, the reason for the high
efficiency without base is supposedly that 3 acts not only as
a catalyst but also as a base, which has a much higher tendency
to coordinate to copper to form the active species. So it might be
thought that the MOF containing an amino group had adequate
proles of 2 and 3. All of the adsorption–desorption isotherms
show a type I shape, which is a characteristic of microporous
materials. The BET surface area and pore volume of 2 were
2
ꢁ1
3
ꢁ1
calculated to be 582.20 m g and 0.31 cm g , respectively.
Compared to 2, the BET surface area and pore volume of 3
2
ꢁ1
3
ꢁ1
decreased to 156.04 m
g
and 0.07 cm g , respectively,
mainly because of the added mass of copper(II) chloride to 2.
To gain further insights, we have also performed X-ray
photoelectron spectroscopy (XPS) analysis. The N 1s spectrum
is very useful for analyzing the nature of the N functionalities.
Careful XPS analysis showed the presence of a split peak with
maxima at 398.1 and 399.2 eV for the functional groups of the
Table 1 Aerobic oxidation of benzyl alcohol catalysed by various
catalysts in CH CN
3
a
20
primary amine (Fig. 2d), whereas N 1s has a single peak at
00 eV for the catalyst (Fig. 2e) which suggested strong coordi- Entry
b
4
Catalyst
Time (h)
Yield (%)
21
nation with copper(II) chloride. We also tried to determine the
oxidation state of Cu in 3 using XPS. The CuCl related peak at
34.8 eV was evident in the Cu 2p spectra of the catalyst, 3
1
2
3
4
5
6
CuCl
MOF-N
MOF-NH
None
MOF-NH
2
@MOF-NH
(1)
2
(3)
6
6
6
6
6
6
100
0
0
0
48
35
2
c
c
3
9
2
(2)
18
(Fig. 2f). The spectra of CuCl in 3 was more clearly revealed in
2
2
+ CuCl
2
the Cl 1s spectra (284.1 eV), as shown in Fig. 2 (e, inset).
Furthermore, the Cu 2p XPS spectrum of CuCl /MOF showed
shakeup satellite peaks of the Cu 2p3/2 at 942 and Cu 2p1/2 at
2
62 eV, which conrmed the presence of Cu(II) species (CuCl )
CuCl
2
2
a
Reaction conditions: benzyl alcohol (1.0 mmol), TEMPO (1.0 mmol),
b
c
CH CN (6 mL) and air as an oxygen source. GC yield. Calculated to
have the same amount of Zn (when comparing 3 with 1 and 2).
3
9
2+
17808 | RSC Adv., 2017, 7, 17806–17812
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
Table 2 Aerobic oxidation of various alcohols catalysed by 3 in
a
3
CH CN
b
Entry
Substrate
Product
Time (h)
Yield (%)
1
2
6
98
98
5.5
3
4
5
6
5.5
6
96
90
96
82
Fig. 3 Aerobic oxidation of benzyl alcohol catalysed by 3 (a) in
different solvents, (b) with base and without base, and the (c) hot
filtration test and (d) recyclability test. In all cases, the reaction
conditions are the same as in Table 2 (entry 1).
7
7.5
basicity for deprotonation, and the oxidation could occur
7
8
9
7
98
96
98
93
94
61
24
without any external base. Subsequently, we optimized the
effect of the catalyst loading and found that 1 mol% of Cu had
the best efficiency for alcohol oxidation (Fig. S1†). These ob-
tained results suggested that 3 (1 mol%) is required to promote
8
7
3
base-free air oxidation in CH CN. With these optimized results
on hand, the reactions of various aryl, alkyl and hetero-aryl
substrates were investigated, with the assistance of TEMPO as
the co-catalyst, and the results are summarized in Table 2.
In order to extend the scope of the aerobic oxidation by 3, we
performed the aerobic oxidation of various aromatic and
aliphatic alcohols (Table 2). All of the reactions, such as for
benzyl alcohol (entry 1), proceeded smoothly to give the corre-
sponding products in high yield with 100% selectivity under
base-free conditions. Where possible, the product peaks were
1
1
1
0
1
2
7
7
11.5
1
3
11
8
58
65
48
25,26
14
compared to those reported in the literature.
The electronic
nature of the substituents on the benzylic alcohol did have an
effect on the reaction. Electron-donating group (EDG) contain- 15
ing substrates, such as p-tolylmethanol, (4-methoxyphenyl)
methanol and (2-methoxyphenyl)methanol, reacted to give the
products (entries 2–4) with yields (90–98%) that are obviously
8
a
Reaction conditions: alcohol (1.0 mmol), TEMPO (1.0 mmol), CH CN
3
b
(6 mL) and air as an oxygen source. Isolated yield. Selectivity 100%.
higher than the yields for the electron-withdrawing group
(EWG) containing substrates, such as (4-chlorophenyl)meth-
anol, (2-chlorophenyl)methanol, (4-bromophenyl)methanol 13) in moderate yield (58–61%). In the case of the aliphatic
and (4-nitrophenyl)methanol (entries 5–8). Nevertheless, these alcohols, the product (entries 14–15) yields (48–65%) were lower
results demonstrate that 3 successfully promoted the aerobic than those of the benzylic alcohols. In all cases, the catalyst
oxidation of various alcohols with either an EDG or EWG. It was exhibited good activity in the oxidation of various alcohols.
noteworthy that the aerobic oxidation of secondary alcohols to Importantly, the results demonstrated that the selectivity of the
their corresponding ketones is difficult, which is probably due primary alcohols along with the secondary alcohols was excel-
27
to steric reasons. However, secondary alcohols such as 1- lent (100% selectivity), and the aliphatic alcohols showed
phenylethan-1-ol, 1-(p-tolyl)ethan-1-ol and 1-(4-methoxyphenyl) similar trends.
ethan-1-ol also gave the expected products (entries 9–11) in
In order to gain insight into the heterogeneous nature of 3,
good yield (93–98%). The oxidation of heterocyclic alcohols, a leaching test was carried out, in which the solid catalyst was
such as pyridin-3-yl-methanol and furan-2-yl-methanol, pro- centrifuged and removed aer 2 h, and the reaction continued.
ceeded smoothly to provide the desired products (entries 12 and As indicated in Fig. 3c, no further reaction took place without 3
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 17806–17812 | 17809

View Article Online
RSC Advances
Paper
aer initiation of the reaction at 4 h, and the possible leaching Aer all the starting materials had disappeared (monitored by
of Cu aer completion of the reaction was monitored by ICP FTIR spectroscopy), MOF-NH was given as a slightly yellow
2
16
analysis. This nding indicates that no leaching of the catalyt- solid (Fig. S3c, ESI†). The crystals were ltered off and washed
ically active sites occurs, and that 3 exhibits a typical hetero- with fresh DEF (20 mL ꢂ 4) and ethanol, and then immersed in
ꢀ
geneous catalyst nature, demonstrating that there was excellent ethanol for 12 h. The material was dried at 80 C under vacuum
2
+
coordination interaction between Cu and the amine func- for 24 h. Finally, 0.04 g (0.30 mmol) of copper(II) chloride was
tionalized MOF. As a heterogeneous catalyst, 3 can be reused. dissolved in ethanol (12 mL), and 0.30 g of compound 2 was
Aer each catalytic cycle, 3 could be easily recovered by centri- added to the solution in a 20 mL vial. The reaction mixture was
ꢀ
fugation or ltration, and directly reused in the next run under kept in an oil bath at 45 C for 24 h, and the color of the solution
the same reaction conditions. It was observed that similar yields changed from blue to colorless (Fig. 1f, ESI†). The crystals were
(
98–100%) were obtained by carrying out ve runs without any ltered off and washed with fresh ethanol (20 mL ꢂ 4), and
signicant loss of activity (Fig. 3d). More importantly, the Cu(II)/MOF-NH (3) was given as a blue solid (Fig. S3d, ESI†).
catalyst maintained 100% selectivity during ve consecutive The material was dried at 80 C under vacuum for 24 h.
2
ꢀ
runs. Evidently, the catalyst 3 is highly stable against the Inductively coupled plasma (ICP) analysis showed 5.02% (wt)
migration and sintering of Cu and exhibits excellent activity, Cu in the resulting compound, 3.
selectivity, and stability for the oxidation of alcohols under mild
reaction conditions without the assistance of any base addi-
tives. The FTIR, XRD and XPS spectra of the catalyst, 3, were General procedure for the oxidation reaction
similar to those of the fresh catalyst aer recycling ve times
Fig. S10 and S6c, ESI†), which suggests that the structure and
composition of 3 was maintained.
The oxidation of alcohols was carried out using air oxygen (open
air) at atmospheric pressure in a reaction vial. In a typical run,
a solution of substrate (1.0 mmol) and TEMPO (1.0 mmol) in
(
The well-dened pores of MOFs may offer unique advantages
for catalytic applications, compared with other catalysts in
which the pores may favor size and shape selective catalysis.
The pore size of the as-synthesized catalyst, 3, was bigger than
all of the substrates, as shown in Table 2. For example, the size
CH
3
CN (6 mL) was added to 3 (1 mol%) without base, and the
ꢀ
mixture was heated at 70 C under atmospheric air. Aer
completion of the reaction, the catalyst was ltered off and the
conversion was measured using a GC (Agilent Technologies
3b,28
7890A GC System). The crude product was obtained by
˚
of benzyl alcohol is 6.9 by 4.9 A, and the size of (4-methox-
concentrating the resultant solution under reduced pressure,
and it was puried by column chromatography (on silica gel)
using a mixture of EtOAc–hexane to give the pure corresponding
product (Table 2). All the desired products are known
compounds, which were characterized by comparison of their
spectra with those reported in the previous literature.
˚
yphenyl)methanol is 9.0 by 4.9 A (Fig. 4), which is smaller than
˚
the pore size of 3 (18.3 A) as shown in Fig. S7 and S8† respec-
tively. Therefore, this enhancement and the high selectivity
would be due to the structure of the pores and surface func-
tionality of the MOF frameworks.
25,26
The
separated catalyst was successively reused for the next reaction
without any retreatment. A hot ltering experiment was carried
out by separating the catalyst quickly from the reaction mixture
Experimental
Catalyst preparation
aer 2 h reaction time, and the ltrate was then maintained at
ꢀ
7
0 C for an additional 4 h.
MOF-N
3
(1) was prepared according to the literature proce-
15
dure, and the amine-functionalized MOFs (2) were synthesized
16
by our earlier reported procedure. Typically, 0.31 g of MOF-N
crystals was placed in a 30 mL screw vial, and a solution of 0.80 g
of triphenylphosphine (3.0 mmol) in DEF (30 mL) was added.
3
Conclusions
In summary, we have developed a novel, highly efficient Cu(II)
containing MOF catalytic system, which can be used with the
co-catalyst TEMPO for alcohol oxidation. Numerous practical
features associated with this method should facilitate its use in
synthetic organic chemistry, including use without base addi-
tives, fast reaction rates, mild reaction conditions, and
compatibility with 100% selectivity. More importantly, it is
a highly active recyclable solid catalyst for the oxidation of
various organic substrates under mild conditions. These results
indicate that copper plays a central role in catalytic oxidation.
Together, these catalyst systems provide compelling aerobic
alternatives to traditional alcohol oxidation methods without
the assistance of any base additives. Moreover, the exceptional
reactivity of the novel catalyst system prompted our concurrent
inquiry into the applications of these catalytic matrices in
a multitude of catalytic reactions and engineering processes.
ꢀ
The vial was kept at 80 C in an oil bath for 10 h without stirring.
Fig. 4 Size and shape selectivity in the aerobic oxidation of benzyl
alcohol and (4-methoxyphenyl)methanol using 3.
17810 | RSC Adv., 2017, 7, 17806–17812
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
8
9
(a) H. Miyamura, R. Matsubara, Y. Miyazaki and
S. Kobayashi, Angew. Chem., Int. Ed., 2007, 46, 4151–4154;
(b) H. Chen, Q. H. Tang, Y. T. Chen, Y. B. Yan, C. M. Zhou,
Z. Guo, X. L. Jia and Y. H. Yang, Catal. Sci. Technol., 2013,
Acknowledgements
This work is supported by the Inha University Research Grant
(Inha 2016).
3
, 328–338.
N. F. Zheng and G. D. Stucky, Chem. Commun., 2007, 3862–
864.
3
Notes and references
10 B. A. D’Sa, D. McLeod and J. G. Verkade, J. Org. Chem., 1997,
1
2
(a) A. U. Czaja, N. Trukhanb and U. Muller, Chem. Soc. Rev.,
62, 5057–5061.
2
009, 38, 1284–1293; (b) S. Keskin and S. Kızılel, Ind. Eng. 11 (a) M. F. Semmelhack, C. R. Schmid, D. A. Cort ´e s and
Chem. Res., 2011, 50, 1799–1812; (c) H. Furukawa,
K. E. Cordova, M. O’Keeffe and O. M. Yaghi, Science, 2013,
C. S. Chou, J. Am. Chem. Soc., 1984, 106, 3374–3376; (b)
A. Cecchetto, F. Fontana, F. Minisci and F. Recupero,
Tetrahedron Lett., 2001, 42, 6651–6653.
341, 1230444; (d) R. Ricco, C. Pfeiffer, K. Sumida,
C. J. Sumby, P. Falcaro, S. Furukawa, N. R. Champness and 12 (a) R. A. Sheldon and J. K. Kochi, Metal-Catalyzed Oxidation
C. J. Doonan, CrystEngComm, 2016, 18, 6532–6542.
(a) D. Farrusseng, S. Aguado and C. Pinel, Angew. Chem., Int.
Ed., 2009, 48, 7502–7513; (b) A. Corma, H. Garcia and
F. X. Llabr ´e s i Xamena, Chem. Rev., 2010, 110, 4606–4655;
of Organic Compounds, Academic Press, New York, 1981; (b)
M. Hudlicky, Oxidations in Organic Chemistry, American
Chemical
Society,
Washington,
D.C.,
1990;
(c)
R. A. Sheldon, I. W. C. E. Arends, G. J. Brink and
A. Dijksman, Acc. Chem. Res., 2002, 35, 774–781; (d)
J. Muzart, Tetrahedron, 2003, 59, 5789–5816; (e)
M. Baumann and I. R. Baxendale, Beilstein J. Org. Chem.,
2013, 9, 2265–2319.
(
1
c) M. Yoon, R. Srirambalaji and K. Kim, Chem. Rev., 2012,
12, 1196–1231; (d) J. Gascon, A. Corma, F. Kapteijn and
F. X. Llabr ´e s i Xamena, ACS Catal., 2014, 4, 361–378; (e)
J. W. Liu, L. F. Chen, H. Cui, J. Y. Zhang, L. Zhang and
C. Y. Su, Chem. Soc. Rev., 2014, 43, 6011–6061.
(a) X. Feng, C. Xu, Z.-Q. Wang, S.-F. Tang, W.-J. Fu, B.-M. Ji
and L.-Y. Wang, Inorg. Chem., 2015, 54, 2088–2090; (b) 14 (a) R. D. Ri-chardson and T. Wirth, Angew. Chem., Int. Ed.,
13 B. A. Steinhoff, S. R. Fix and S. S. Stahl, J. Am. Chem. Soc.,
2002, 124, 766–767.
3
4
Y. Qi, Y. Luan, J. Yu, X. Peng and G. Wang, Chem.–Eur. J.,
015, 21, 1589–1597; (c) J. Wang, F.-W. Ding, J.-P. Ma,
Q.-K. Liu, J.-Y. Cheng and Y.-B. Dong, Inorg. Chem., 2015,
4, 10865–10872.
(a) S. Pande, A. Saha, S. Jana, S. Sarkar, M. Basu, M. Pradhan,
2006, 45, 4402–4404; (b) M. Uyanik and K. Ishihara, Chem.
Commun., 2009, 2086–2099; (c) M. Uyanik, M. Akakura and
K. Ishihara, J. Am. Chem. Soc., 2009, 131, 251–262.
15 Y. Goto, H. Sato, S. Shinkai and K. Sada, J. Am. Chem. Soc.,
2008, 130, 14354–14355.
2
5
A. K. Sinha, S. Saha, A. Pal and T. Pal, Org. Lett., 2008, 10, 16 A. Taher, D.-J. Lee, B.-K. Lee and I.-M. Lee, Synlett, 2016, 27,
179–5181; (b) S. E. Allen, R. R. Walvoord, R. P. Salinas and 1433–1437.
M. C. Kozlowski, Chem. Rev., 2013, 113, 6234–6237; (c) 17 (a) R. K. Sharma, S. Dutta and S. Sharma, Dalton Trans., 2015,
5
B. R. Kim, J. S. Oh, J. Kim and C. Y. Lee, Bull. Korean
Chem. Soc., 2015, 36, 2799–2800; (d) Z. Miao, Y. Luan,
C. Qib and D. Ramellac, Dalton Trans., 2016, 45, 13917–
44,
1303–1316;
(b)
A.
Ghorbani-Choghamarani,
Z. Darvishnejad and M. Norouzi, Appl. Organomet. Chem.,
2015, 29, 170–175; (c) Q.-L. Yan, A. Cohen, N. Petrutik,
A. Shlomovich, J.-G. Zhang and M. Gozin, ACS Appl. Mater.
Interfaces, 2016, 8, 21674–21682.
13924; (e) B. R. Kim, J. S. Oh, J. Kim and C. Y. Lee, Catal.
Lett., 2016, 146, 734–743.
5
(a) E. T. T. Kumpulainen and A. M. P. Koskinen, Chem.–Eur. 18 (a) Y.-H. Choi and S.-H. Hong, Langmuir, 2015, 31, 8101–
J., 2009, 15, 10901–10911; (b) K. T. Mahmudov,
M. N. Kopylovich, M. Silva, P. J. Figiel, Y. Y. Karabach and
8110; (b) K. J. Lee, Y.-I. Lee, I.-K. Shim, J. Joung and
Y. S. Oh, J. Colloid Interface Sci., 2006, 304, 92–97.
A. J. L. Pombeiro, J. Mol. Catal. A: Chem., 2010, 318, 44–50; 19 Y. Zhang, Z. Xie, Z. Wang, X. Feng, Y. Wang and A. Wu,
c) X. Zhang, W. Dong, Y. Luan, M. Yang, L. Tan, Y. Guo,
Dalton Trans., 2016, 45, 12653–12660.
H. Gao, Y. Tang, R. Dang, J. Li and G. Wang, J. Mater. 20 A. Adenier, M. M. Chehimi, I. Gallardo, J. Pinson and N. Vila,
Chem. A, 2015, 3, 4266–4273.
Langmuir, 2004, 20, 8243–8253.
(a) P. Gamez, I. W. C. E. Arends, J. Reedijk and R. A. Sheldon, 21 J. Marsh, L. Minel, M. G. Barth ´e s-Labrousse and D. Gorse,
Chem. Commun., 2003, 2414–2415; (b) P. J. Figiel, A. Sibaouih, Appl. Surf. Sci., 1998, 133, 270–286.
J. U. Ahmad, M. Nieger, M. T. R ¨a is ¨a nen, M. Leskel ¨a and 22 (a) M. Gopiraman, S. G. Babu, Z. Khatri, W. Kai, Y. A. Kim,
(
6
7
T. Repo, Adv. Synth. Catal., 2009, 351, 2625–2632; (c)
Q. F. Wang, Y. Zhang, G. X. Zheng, Z. Z. Tian and
G. Y. Yang, Catal. Commun., 2011, 14, 92–95.
M. Endo, R. Karvembu and I. S. Kim, Carbon, 2013, 62,
135–148; (b) M. Gopiraman, D. Deng, S. G. Babu,
T. Hayashi, R. Karvembu and I. S. Kim, ACS Sustainable
Chem. Eng., 2015, 3, 2478–2488.
(a) A. Dhakshinamoorthy, M. Alvaro and H. Garcia, ACS
Catal., 2011, 1, 48–53; (b) M. Paul, N. N. Adarsh and 23 (a) C. Bai, Q. Zhao, Y. Li, G. Zhang, F. Zhang and X. Fan,
P. Dastidar, Cryst. Growth Des., 2014, 14, 1331–1337; (c)
L. C. Li, R. Matsuda, I. Tanaka, H. Sato, P. Kanoo,
Catal. Lett., 2014, 144, 1617–1623; (b) A. Taher, D.-J. Lee
and I.-M. Lee, Synlett, 2016, 27, 2333–2338.
H. J. Jeon, M. L. Foo, A. Wakamiya, Y. Murata and 24 S. Mannam, S. K. Alamsetti and G. Sekar, Adv. Synth. Catal.,
S. Kitagawa, J. Am. Chem. Soc., 2014, 136, 7543–7546. 2007, 349, 2253–2258.
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 17806–17812 | 17811

View Article Online
RSC Advances
Paper
2
2
2
5 G. Zhang, X. Han, Y. Luan, Y. Wang, X. Wen and C. Ding,
Chem. Commun., 2013, 49, 7908–7910.
J. Xu, Q. Gu, L. M. Chen and X. X. Wang, ACS Catal., 2012,
2, 622–631.
6 C. Bai, A. Li, X. Yao, H. Liu and Y. Li, Green Chem., 2016, 18, 28 S. Horike, M. Dinca, K. Tamaki and J. R. Long, J. Am. Chem.
061–1069. Soc., 2008, 130, 5854–5855.
1
7 (a) R. H. Liu, X. M. Liang, C. Y. Dong and X. Q. Hu, J. Am.
Chem. Soc., 2004, 126, 4112–4113; (b) J. L. Long, X. Q. Xie,
17812 | RSC Adv., 2017, 7, 17806–17812
This journal is © The Royal Society of Chemistry 2017