Copper Nanoparticles on Ordered Mesoporous Carbon Nitride Support: a Superior Catalyst for Homo- and Cross-Coupling of Terminal Alkynes under Base-Free Conditions

Article abstract of DOI:10.1002/ejoc.201901296

A novel ordered mesoporous carbon nitride (OMCN) was synthesized as a functionalized support with 2,4,6-trichloro-1,3,5-triazine and benzidine as starting materials in the presence of SBA-15 as a template. Copper nanoparticles were then loaded on the C–N material to achieve a novel nanocomposite catalyst (Cu NPs-OMCN). The nanocomposite was utilized as a highly efficient catalyst for homo- and cross-coupling of terminal alkynes under base-free conditions in ethanol, and various symmetrical and unsymmetrical 1,3-diynes were obtained with good to excellent yields. Moreover, based on this reaction, a one-pot approach to synthesize 2,5-disubstituted thiophenes and furans from terminal alkynes were developed. Furthermore, the heterogeneous catalyst could be recovered and reused conveniently for several times with satisfactory yields.

Full text of DOI:10.1002/ejoc.201901296

DOI: 10.1002/slct.201902475
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Poly (amic acid) Salt-stabilized Au-Ag Alloy Nanoparticles
as Efficient and Recyclable Quasi-homogeneous Catalysts
for the Imines Synthesis from Alcohols and Amines in
Water
Jiali Xu,[a] Faguo Luo,[a] Jun Li,[b] Ke Yang,[a] and Hengfeng Li*[a]
Water-soluble AuÀ Ag bimetallic nanoparticles with different
Au/Ag molar ratios stabilized by poly (amic acid) salt (PAAS)
were synthesized by a one-pot method and characterized by
ultraviolet-visible spectrophotometer (UV-vis), X-ray diffractom-
eter (XRD), X-ray photoelectron spectroscope (XPS) and High-
Angle Annular Dark Field scanning transmission electron micro-
scope (HAADF-STEM). The AuÀ Ag/PAAS catalysts displayed
high activity for the aerobic oxidative coupling reaction of
alcohols and amines in water. Attributing to the synergistic
effect between Au and Ag, the activity of the bimetallic
catalysts was superior to that of the corresponding mono-
metallic catalysts. The catalyst with an Au/Ag molar ratio of 6/1
showed the best catalytic performance, which could be easily
recovered and reused without significant loss of activity for
over 5 times due to the pH response of PAAS.
24 Introduction
25
Imines, which own reactive C=N bonds, are common inter-
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mediates for the synthesis of pharmaceutically and biologically
active compounds and fine chemicals.[1] Conventionally,
carbonyl compounds, especially unstable aldehydes are usually
required in the condensation with amines to produce imines.
The necessity of dehydrating agents and Lewis acid make the
reaction suffer from various drawbacks such as energy
consumption and complicated operation.[2] Therefore ecological
friendly synthesis of imines remains a challenge and develop-
ing an efficient and durable catalyst is highly desirable.[3]
Recently, the direct synthesis of imines via oxidative coupling
of alcohols with amines has received much attention as it
meets the requirements of green chemistry for the following
advantages: i) the starting materials are readily available; ii)
molecular oxygen or air can serve as the terminal oxidant; iii)
the only byproduct is water and iv) various imines can be easily
obtained by choosing different starting substrates.[4] The
reaction of synthesis of imines from amines and alcohols was
normally thought to be divided into two steps shown in
Scheme 1.[5] During the transformations, a molecular of alcohol
Scheme 1. Two step synthesis of imines from amines and alcohols.
is oxidized to corresponding aldehyde as the intermediate.
Then the cross-coupling reaction occurred between amine and
aldehyde to form imine, amide or other product during which
selectivity depends on the nature of catalysts and reaction
condition.[6]
Many homogeneous transition-metal complexes have been
reported in the application of the cross-coupling of alcohols
with amines. However, some problems, such as recycling,
reusing strict reaction conditions and high cost of ligands, have
not been well solved.[7] In contrast, owing to inherent
advantages of heterogeneous systems such as high activity,
convenience of handling and recovery, diverse heterogeneous
transition-metal catalysts were designed to prepare imines
from alcohols and amines. Among them noble metals like Pd,[8]
Pt,[9] Ru,[10] and Au[11] are usually selected as the active species
of catalysts. However, sometimes a high temperature is still
required, while in most cases the coupling of amines with
alcohols is carried out in organic solvent. Great efforts have
been made for the utilization of water as solvent in the reaction
by researchers. Zhang et al. reported an AuÀ Pd/resin catalyst
which can catalyze the aerobic oxidative coupling of alcohols
with amines in water phase,[3] however, low yield of imines was
obtained. To improve the yield of imines in aqueous phase,
Wang et al. developed an Au/HT catalyst and the highest yield
of imines reached 99% under mild conditions.[12] But a draw-
back is that the yield of imines decreased dramatically when
the catalyst was put into use for the second run.
[a] J. Xu, F. Luo, Dr. K. Yang, Dr. H. Li
School of Materials Science and Engineering
Central South University
932 South Lushan Road, Changsha 410083, China
E-mail: lihf@csu.edu.cn
[b] J. Li
Hunan Key Laboratory of Biomedical Nanomaterials and Devices, College
of Life Sciences and Chemistry
Hunan University of Technology, 88 Taishan Road, Zhuzhou 412007,
China
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/slct.201902475
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Figure 1. (a) UV-visible absorption spectra of AuÀ Ag alloy nanoparticles, (b) A linear plot of surface plasmon bands against the mole fractions of Au atoms in
alloy nanoparticles.
During the past decades, bimetallic nanomaterials have Results and Discussion
attracted considerable attention due to their improved catalytic
Characterization of the Ag/PAAS, Au/PAAS and Au-Ag/PAAS
activity, selectivity, and stability derived from synergistic
materials
effects.[13] Among all the bimetallic systems, AuÀ Ag alloy
nanostructure have a great potential in the synthesis of fine
chemicals,[14] especially in catalytic oxidation reactions. In
addition, the activity and selectivity of AuÀ Ag bimetallic
nanocatalysts can be controlled via varying the Au/Ag molar
ratio. Huang et al. reported selective oxidation of alcohols
catalyzed by P123-stabilized AuÀ Ag alloy nanoparticles and the
catalyst with a composition of Au0.95Ag0.05 showed the best
catalytic activity and selectivity of alcohols.[15] However, to the
best of our knowledge, no research of applying AuÀ Ag
bimetallic nanocatalysts to direct synthesis of imines from
alcohols and amines has been reported.
UV-vis spectroscopy has been proved to be helpful to
distinguish the structure of bimetallic particles. In case of a
physical mixture of monometallic Ag and Au nanoparticles as
well as system with a core-shell structure, there should appear
two surface plasmon resonance (SPR) bands while exclusive
peak to an alloy structure, whose position fall in between
monometallic nanoparticles.[17] As shown in Figure 1(a), plas-
mon absorption peaks of monometallic Au and Ag nano-
particles were observed at 532 nm and 413 nm, respectively.
Single absorption peaks were observed for each alloy cases.
Meanwhile, the peaks in Figure 1(b) showed a red-shift linearly
with the increasing of Au content. These results helped to
deduce that the obtained Au-AgNPs are alloy structure.[18]
TEM image displayed in Figure S1 showed that AuÀ Ag
bimetallic nanoparticles were typically spherical and highly
dispersed in the PAAS solution proving the protective effect of
PAAS chains. Clearly, all of bimetallic nanoparticles have
relatively smaller sizes than monometallic ones. The sizes of
Au6Ag1NPs in Figure 2(a) were collected and the statistic was
displayed in Figure 2(b) with a counted diameter of 10�5 nm.
HAADF-STEM was employed to characterize AuÀ Ag bimetallic
nanoparticles. It is well-known that HAADF imaging is partic-
ularly sensitive to atomic number, which could distinguish the
structure of bimetal through the degree of light and shade.[19]
Therefore, an alloy structure could be deduced clearly from
uniform intensity distribution in the particle region in Fig-
ure 2(c).[20]
Nowadays, novel quasi-homogeneous catalysts combining
the efficiency of homogeneous catalysts and the durability of
heterogeneous catalysts offer the possibility of designing an
efficient and durable catalyst which can catalyze the synthesis
of imines under mild conditions in aqueous media. In prior
work, Ag nanoparticles stabilized by pH-responsive poly (amic
acid) salt (Ag/PAAS) were prepared successfully via a one-pot
method.[16] The Ag/PAAS was found to have high activity for
the catalytic hydration of various nitriles in aqueous medium
and could be recycled and reused easily by adjusting pH of the
system. In this paper, we present a one-pot synthesis of AuÀ Ag
alloy nanoparticles stabilized by poly (amic acid) salt (AuÀ Ag/
PAAS). The nanoparticles were applied in catalyzing the
synthesis of imines via oxidative coupling of alcohols with
amines under mild condition in water. The catalyst with a
composition of Au6Ag1 demonstrated the highest activity and
selectivity. Ascribing to its pH response, the catalyst was able
to be easily recycled for 5 times at least without apparent
decrease of activity after the reaction.
The XRD patterns for the monometallic Ag, Au and their
bimetallic nanoparticles were given in Figure 3. The four peaks
°
°
°
°
appearing at 2θ= 38.60 , 44.22 , 64.92 , 77.72 were assigned
to the (111), (200), (220) and (311) planes of the face centered
cubic Ag (or Au) particles.[21] Since gold and silver have the
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Figure 2. (a) TEM micrographs, (b) size distribution of Au6Ag1 nanoparticles and (c) HAADF-STEM images of Au6Ag1NPs.
bimetallic AuÀ Ag and monometallic Au or Ag nanoparticles
shown in Table 1 were in good agreement with reported
Table 1. Positions of XPS peaks and surface compositions for AuÀ Ag
nanoparticles with different composition
Binding energy (eV)
Au
Ag
Catalysts
Au:Ag(by XPS)
4f7/2
4f5/2
3d5/2
3d3/2
Au
1:0
84.26
84.11
84.06
84.11
83.96
-
87.86
87.75
87.73
87.78
87.60
-
-
-
Au9Ag1
Au6Ag1
Au4Ag1
Au1Ag1
Ag
9.25:1
6.22:1
4:1
1:1
0:1
367.73
367.71
367.74
367.77
368.26
373.66
373.72
373.75
373.80
374.29
Figure 3. X-ray diffraction patterns of the catalysts with different composi-
tion.
literatures.[24] Firstly, zero valent state of Au and Ag atoms in
alloy was actually proved. The minute shift of BE values was
another indication that the Au and Ag metals have formed
alloy nanoparticles rather than monometallic nanoparticles.[25]
Besides, for bimetallic core-shell structure, the surface atomic
composition should be exclusive. As displayed in Table 1, the
surface composition analyzed by XPS changed with the differ-
ent addition of Au and Ag, further indicating the formation of
AuÀ Ag alloy rather than core-shell structure.[26] The weak peak
at 200 eV only appearing on monometallic AgNPs (Figure S2)
indicated the traces of AgCl, which is in accord with XRD
results. The analysis of XPS spectra also confirmed the presence
of polymer (C1s) as stabilizing agents of the AuÀ Ag alloy
nanoparticles.
same face-centered cubic (fcc) structure and almost the same
lattice constant, thus, it is difficult to distinguish AuÀ Ag alloy
from a mixture of the monometallic phases by XRD pattern.
The result matches with the earlier reports.[22] Broader bands
appeared for bimetallic combinations than monometallic nano-
particles, which is in accordance with the sizes comparison
from TEM images. The appearance of diffraction peaks
belonging to fcc AgCl species (the values of
°
°
°
°
27.90 ,32.30 ,46.30 and 54.99 corresponding to the (111),
(200), (220) and (311) planes of AgCl in the XRD pattern of Ag/
PAAS) indicated that silver ions could not be reduced
completely by using piperidine as reducing agent. The
phenomenon disappeared after Au ions was added simulta-
neously, and it could be assumed that the addition of Au
catalyzed the reduction of the other kind of ions.
Catalytic applications for the oxidative cross-coupling of
amines and alcohols
The catalytic performance of Ag/PAAS, Au/PAAS and AuÀ Ag/
PAAS were explored by selecting the synthesis of imines via
oxidative coupling of alcohols with amines under aqueous
conditions as the model reaction. Firstly, the effect of the Au/
Ag ratio was investigated with aniline and benzyl alcohol as
substrates and the results were listed in Table 2. The reaction
XPS was applied in order to evaluate the surface composi-
tion and chemical states of metal atoms in the composites. The
XPS trace of AuÀ Ag alloy shown in Figure S2 containing peaks
of both Au 4f and Ag 3d confirmed the bimetallic nature of
alloy nanoparticles.[23] The binding energy (BE) values for the
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Figure 4. (a) and (b) XPS analysis of AuÀ Ag nanoparticles with different composition.
Table 2. Catalytic performance of AuÀ Ag/ PAAS on the cross-coupling of
aniline and benzyl alcohol[a]
conversion was achieved by using the Au6Ag1/PAAS as catalyst
(entry 4). In this way, a new method is provided to control the
activity of the cross-coupling of amines and alcohols in water
phase by tuning the Au/Ag molar ratios. Clearly, the bimetallic
catalysts earned more outstanding conversion than corre-
sponding monometallic catalysts and the result should to be
attributed to the synergistic effect between Au and Ag.[14g,27] It
was also found that gold-rich catalysts were much more active
than silver-rich catalysts, hence Au atoms should be considered
as the active species in the reaction. It is because of adding Ag
to form alloy structure with Au dramatically increased the
catalytic activity. In addition to the composition of metal, base
is another important factor in comparison of entries 8–12 that
affected reaction process as a kind of co-catalyst for the
hydrolysis of imine can be inhibited to some extent by base.[11d]
However, different base afforded various results and among
LiOH, NaOH, KOH and K2CO3, LiOH displayed best performance
with an optimal amount of 1.1 equivalent. Too much base
gained lower yield of N-Benzylideneaniline but resulted more
N-benzyl aniline which seemed to be more suitable to excess
base in the final product.
Entry
Catalysts
Base(equiv.)
Yield %[b]
1
2
3
4
5
6
7
8
PAAS
Au/PAAS
LiOH(1.1)
LiOH(1.1)
LiOH(1.1)
LiOH(1.1)
LiOH(1.1)
LiOH(1.1)
LiOH(1.1)
KOH(1.1)
NaOH(1.1)
K2CO3(1.1)
LiOH(0.5)
LiOH(2.0)
None
<2
64
80
90
52
16
2
58
62
4
Au9Ag1/PAAS
Au6Ag1/PAAS
Au4Ag1/PAAS
Au1Ag1/PAAS
Ag/PAAS
Au6Ag1/PAAS
Au6Ag1/PAAS
Au6Ag1/PAAS
Au6Ag1/PAAS
Au6Ag1/PAAS
Au6Ag1/PAAS
9
10
11
12
13
32
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<1
[a] aniline (0.25 mmol), benzyl alcohol (0.5 mmol), catalyst (2 mol%), H2O
(2 mL). [b] The yield was detected by GC-FID according to the peak area.
°
did not proceed at 60 C even after 20 h in blank PAAS
With the adjusted optimum catalyst, the application scope
of the Au6Ag1/PAAS catalyst was then examined with various
combinations of amines and alcohols (Table 3). As expected,
the anilines with various substituents were successfully con-
verted to the corresponding imines by condensation with
benzyl alcohol (entries1-6). The halide-substituted anilines were
successfully cross-coupled with benzyl alcohol and earned a
moderate conversion without dehalogenation (entries 5–6).
Besides, the electron-donating substituents on the aromatic
ring were more suitable for the imidization reaction than the
electron-withdrawing substituents through comparing entries
2–3 with entries 5–6. The low water-solubility of halogen-
substituted aniline was speculated as the reason of only 67%
conversion was obtained when 4-bromoaniline was used as the
started material (entry 6). Almost a full conversion was gotten
when benzylamine was coupled with benzyl alcohol (entry 7).
solutions (entry 1), ensuring that the reaction was not catalyzed
by PAAS and LiOH. When using Ag/PAAS, Au/PAAS and
AuÀ Ag/PAAS as catalysts, the only product was N-Benzylide-
neaniline. The result indicated that the PAAS stabilized Au
monometallic, Ag monometallic and AuÀ Ag bimetallic nano-
particles had a high selectivity towards imines in the oxidative
coupling of alcohols with amines in aqueous phase, which is
different from the results reported by other groups.[3,12] It was
also found that the activity changed remarkably along with
varying the composition of AuÀ Ag nanocatalysts. For mono-
metallic silver and silver-rich alloy catalysts(Ag/Au^1, entries 6
and 7), the catalyst did not perform well with a conversion less
than 20%. On the other hand, for monometallic gold and gold-
rich alloy catalysts (Au/Ag^4, entrie2-5), pretty better con-
version was obtained, and the best result with a 90%
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indicating that the catalyst was still highly stabilized by the
PAAS polymer. The 5 times recycled Au6Ag1/PAAS catalyst was
characterized by TEM and the result was exhibited in Figure 5b.
As TEM image illustrated, an increasement of particles sizes and
the slight aggregation should be responsible for the little
decline of activity in the last few recycles.
Table 3. Synthesis of imines from different alcohols and amines[a]
1
2
3
4
5
6
7
8
9
Entry
Amine
Alcohol
Yield %[b]
1
2
3
90
91
94
To manifest the superiority of our catalytic system, a
contrastive list was shown in Table 4 to compare with other
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Table 4. Comparison of catalytic activity of the AuÀ Ag/PAAS catalyst in the
imination with previously reported systems
4
95
5
6
7
87
67
99
°
Catalysts
Temp.( C) Solvent
Time
(h)
Yield
(%)
Ref.
Pd/AlO(OH)
PtÀ Sn/g-
Al2O3
Ru(OH)x/TiO2 100
Au/HAP 60
Au/Mg2Al-HT 60
90
138
Heptane
Ethyl
24
30
91
99
[8]
[9]
benzene
Toluene
Toluene
Toluene
H2O
8
92
92
94
84
89
98
99
2
2.5
6
12
24
12
91
99
97
65
63
94
[10]
[11a]
[11b]
[3]
[12]
This
work
9
AuÀ Pd/resin
40
40
60
10
11
12
13
14
Au/HT
H2O
H2O
Au6Ag1/
PAAS
analogous reaction system. Apparently, the shortcomings of
high temperature and organic solvent that goes against green
chemistry were firstly spurned. Besides, that the stabilizer of
nanoparticles is more accessible, and the yield is higher could
be more adaptive to rapid and economic industry. To sum up,
the gold and silver alloy nanoparticles supported on PAAS are
a decent system deserved to develop further.
[a] alcohol (0.5 mmol), amine (0.25 mmol), catalyst (2 mol%), LiOH
(0.275 mmol), H2O (2 mL). [b] The yield was detected by GC-FID according
to the peak area.
Further, the reactions of anilines with different benzyl alcohols
were also studied and surprising performances (entries 8–11)
were shown. Excellent yields of 84–94% were recorded in the
case of methyl-, methoxy-, chloro-, and bromo-substituted
benzyl alcohols. The reaction between aniline and heterocyclic
alcohol like 2-thiopheneethanol (entry 12) also gained good
result. In addition, two kinds of aliphatic amine reacted with
benzyl alcohol successfully (entries 13–14), which might
provide a feasible approach for further development of imines
with aliphatic groups.
Because the pH-induced precipitation-redispersion process
of PAAS is highly reversible, the recycle of the AuÀ Ag/PAAS can
be easily investigated. After the product was extracted by ethyl
acetate, the optimal Au6Ag1/PAAS catalyst was separated by
adjusting the pH of solution to ∼2. The precipitate was
collected and redissolved in 2 mL of water by increasing the pH
to ∼9.0 with NaOH. The catalytic activity of the recycled
catalysts was examined for the imidization of benzylamine and
benzyl alcohol which has earned the best yield as listed in
Table 3. As shown in Figure 5a, the Au6Ag1/PAAS catalyst could
be reused for five times with no significant loss of activity,
Conclusions
In conclusion, PAAS stabilized AuÀ Ag bimetallic nanocatalysts
were developed successfully. The catalysts demonstrated high
and tunable activities, a wide substrate scope and good
reusability for oxidative coupling of alcohols and amines to
synthesize imines in water phase. The Au6Ag1/PAAS catalyst
showed the best catalytic performance. Moreover, the pH
sensitivity of PAAS afforded a reversible precipitation–redis-
persion switch, allowing efficient recovery and recycling of the
nanoparticles. The catalyst could be reused for five runs
without significant loss of catalytic activity. The synergistic
interplay between Au and Ag revealed in this work may offer a
new guide in the green synthesis of fine chemicals.
Supporting Information Summary
The experimental details, TEM images and XPS survey scan of
all the prepared AuÀ Ag nanoparticles, GC-MS spectra for the
imines products.
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Figure 5. (a) Reuse of the Au6Ag1/PAAS catalyst for the condensation of benzylamine and benzyl alcohol, (b) TEM image of Au6Ag1/PAAS catalyst after 5 times
recycling. Reaction conditions were identical to those indicated in Table 3 (12 h reaction time in each cycle).
[9] W. He, L. D. Wang, C. L. Sun, K. K. Wu, S. B. He, J. P. Chen, P. Wu, Z. K. Yu,
Chem-Eur J 2011, 17, 13308–13317.
25 Acknowledgements
26
27
28
[10] J. W. Kim, J. He, K. Yamaguchi, N. Mizuno, Chem Lett 2009, 38, 920–921.
[11] a) H. Sun, F. Z. Su, J. Ni, Y. Cao, H. Y. He, K. N. Fan, Angew Chem Int Edit
2009, 48, 4390–4393; b) P. Liu, C. Li, E. J. M. Hensen, Chem-Eur J 2012,
18, 12122–12129; c) S. Kegnaes, J. Mielby, U. V. Mentzel, C. H. Christen-
sen, A. Riisager, Green Chem 2010, 12, 1437–1441; d) W. J. Cui, H. Y. Zhu,
M. L. Jia, W. L. Ao, Y. L. Zhang, B. Zhaorigetu, React Kinet Mech Cat 2013,
109, 551–562.
The authors gratefully acknowledge supports from the National
Natural Science Foundation of China (No. 51573209).
29
30 Conflict of Interest
31
32
33
[12] Q. Q. Wang, Y. Q. Deng, F. Shi, Catal Sci Technol 2014, 4, 1710–1715.
[13] a) A. Shah, Latif-ur-Rahman, R. Qureshi, Zia-ur-Rehman, Rev Adv Mater
Sci 2012, 30, 133–149; b) B. Lim, M. J. Jiang, P. H. C. Camargo, E. C. Cho,
J. Tao, X. M. Lu, Y. M. Zhu, Y. N. Xia, Science 2009, 324, 1302–1305; c) F.
Tao, M. E. Grass, Y. W. Zhang, D. R. Butcher, J. R. Renzas, Z. Liu, J. Y.
Chung, B. S. Mun, M. Salmeron, G. A. Somorjai, Science 2008, 322, 932–
934.
The authors declare no conflict of interest.
Keywords: alloy · imines · nanoparticles · poly(amic acid) salt ·
quasi-homogenous
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[14] a) S. E. Hunyadi, C. J. Murphy, J Mater Chem 2006, 16, 3929–3935; b) H. J.
Zhang, M. Haba, M. Okumura, T. Akita, S. Hashimoto, N. Toshima,
Langmuir 2013, 29, 10330–10339; c) J. C. S. Costa, P. Corio, L. M. Rossi,
Nanoscale 2015, 7, 8536–8543; d) G. Nagy, T. Benko, L. Borko, T. Csay, A.
Horvath, K. Frey, A. Beck, React Kinet Mech Cat 2015, 115, 45–65; e) I.
Sobczak, E. Dembowiak, J Mol Catal A-Chem 2015, 409, 137–148; f) A. Q.
Wang, C. M. Chang, C. Y. Mou, J Phys Chem B 2005, 109, 18860–18867;
g) J. H. Liu, A. Q. Wang, Y. S. Chi, H. P. Lin, C. Y. Mou, J Phys Chem B 2005,
109, 40–43.
[15] X. M. Huang, X. G. Wang, M. W. Tan, X. J. Zou, W. Z. Ding, X. G. Lu, Appl
Catal a-Gen 2013, 467, 407–413.
[16] J. Li, G. N. Tang, Y. C. Wang, Y. Wang, Z. X. Li, H. F. Li, New J Chem 2016,
40, 358–364.
[17] a) W. J. Kim, S. Kim, A. R. Kim, D. J. Yoo, Ind Eng Chem Res 2013, 52,
7282–7288; b) D. P. Tang, R. Yuan, Y. Q. Chai, Biotechnol Bioeng 2006, 94,
996–1004; c) K. K. Haldar, S. Kundu, A. Patra, Acs Appl Mater Inter 2014, 6,
21946–21953; d) M.-X. Zhang, R. Cui, J.-Y. Zhao, Z.-L. Zhang, D.-W. Pang,
J Mater Chem 2011, 21, 17080–17082.
[18] X. L. Ren, X. M. Meng, F. Q. Tang, Sensor Actuat B-Chem 2005, 110, 358–
363.
[19] X. Cao, A. Mirjalili, J. Wheeler, W. Xie, B. W. L. Jang, Front Chem Sci Eng
2015, 9, 442–449.
[1] a) R. D. Patil, S. Adimurthy, Asian J Org Chem 2013, 2, 726–744; b) K. N.
Tayade, M. Mishra, J Mol Catal A-Chem 2014, 382, 114–125.
[2] a) R. S. Varma, R. Dahiya, S. Kumar, Tetrahedron Lett 1997, 38, 2039–
2042; b) G. C. Liu, D. A. Cogan, T. D. Owens, T. P. Tang, J. A. Ellman, J Org
Chem 1999, 64, 1278–1284; c) H. Naeimi, F. Salimi, K. Rabiei, J Mol Catal
A-Chem 2006, 260, 100–104.
[3] L. L. Zhang, W. T. Wang, A. Q. Wang, Y. T. Cui, X. F. Yang, Y. Q. Huang,
X. Y. Liu, W. G. Liu, J. Y. Son, H. S. Oji, T. Zhang, Green Chem 2013, 15,
2680–2684.
[4] B. Chen, L. Y. Wang, S. Gao, ACS Catal 2015, 5, 5851–5876.
[5] a) R. R. Donthiri, R. D. Patil, S. Adimurthy, Eur J Org Chem 2012, 24, 4457–
4460; b) Y. Shiraishi, M. Ikeda, D. Tsukamoto, S. Tanaka, T. Hirai, Chem
Commun 2011, 47, 4811–4813; c) M. Bala, P. K. Verma, N. Kumar, U.
Sharma, B. Singh, Can J Chem 2013, 91, 732–737.
[6] J. F. Soule, H. Miyamura, S. Kobayashi, Chem Commun 2013, 49, 355–
357.
[7] a) B. Gnanaprakasam, J. Zhang, D. Milstein, Angew Chem Int Edit 2010,
49, 1468–1471; b) L. Jiang, L. L. Jin, H. W. Tian, X. Q. Yuan, X. C. Yu, Q. Xu,
Chem Commun 2011, 47, 10833–10835; c) H. X. Li, X. T. Wang, M. W.
Wen, Z. X. Wang, Eur J Inorg Chem 2012, 5011–5020; d) A. Maggi, R.
Madsen, Organometallics 2012, 31, 451–455; e) E. L. Zhang, H. W. Tian,
S. D. Xu, X. C. Yu, Q. Xu, Org Lett 2013, 15, 2704–2707; f) M. Y. Guan, C.
Wang, J. Y. Zhang, Y. S. Zhao, RSC Adv. 2014, 4, 48777–48782.
[8] M. S. Kwon, S. Kim, S. Park, W. Bosco, R. K. Chidrala, J. Park, J Org Chem
2009, 74, 2877–2879.
[20] a) J. C. Hernández-Garrido, M. S. Moreno, C. Ducati, L. A. Pérez, P. A.
Midgley, E. A. Coronado, Nanoscale 2014, 6, 12696–12702; b) C.
Bhattacharya, B. R. Jagirdar, J Phys Chem C 2018, 122, 10559–10574.
ChemistrySelect 2019, 4, 10401–10407
10406
© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Papers
[21] E. Goudeli, S. E. Pratsinis, Acs Nano 2017, 11, 11653–11660.
[22] a) D. H. Chen, C. J. Chen, J Mater Chem 2002, 12, 1557–1562; b) S. S.
Shankar, A. Rai, A. Ahmad, M. Sastry, J Colloid Interf Sci 2004, 275, 496–
502.
[23] S. Malathi, T. Ezhilarasu, T. Abiraman, S. Balasubramanian, Carbohyd
Polym 2014, 111, 734–743.
[24] L. Zhang, C. Wang, Y. Zhang, Appl Surf Sci 2012, 258, 5312–5318.
[25] a) N. N. Kariuki, J. Luo, M. M. Maye, S. A. Hassan, T. Menard, H. R.
Naslund, Y. H. Lin, C. M. Wang, M. H. Engelhard, C. J. Zhong, Langmuir
2004, 20, 11240–11246; b) M. S. Rubina, E. E. Kamitov, Y. V. Zubavichus,
G. S. Peters, A. V. Naumkin, S. Suzer, A. Y. Vasil’kov, Appl Surf Sci 2016,
366, 365–371.
[26] X. M. Huang, X. G. Wang, X. S. Wang, X. X. Wang, M. W. Tan, W. Z. Ding,
X. G. Lu, J Catal 2013, 301, 217–226.
[27] X. Y. Liu, A. Q. Wang, L. Li, T. Zhang, C. Y. Mou, J. F. Lee, Prog Nat Sci-
Mater 2013, 23, 317–325.
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