A facile synthesis of copper nanoparticles supported on an ordered mesoporous polymer as an efficient and stable catalyst for solvent-free sonogashira coupling Reactions

Article abstract of DOI:10.1039/c7gc00219j

A novel mesoporous phenol-formaldehyde resin-supported copper nanoparticles catalyst was prepared using a two-step protocol involving the melt infiltration of copper nitrate hydrates and the subsequent template pyrolysis-induced in situ reduction of Cu(ii

Full text of DOI:10.1039/c7gc00219j

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A Facile Synthesis of Copper Nanoparticles Supported on Ordered
Mesoporous Polymer as an Efficient and Stable Catalyst for
Solvent-Free Sonogashira Coupling Reactions
a
a
Kaixuan Wang,‡ Liping Yang,‡ Weiliang Zhao,a Linqing Cao,a Zhenliang Sun*b
and Fang Zhang*a
a The Education Ministry Key Lab of Resource Chemistry and Shanghai Key
Laboratory of Rare Earth Functional Materials, Shanghai Normal University,
Shanghai 200234, P. R. China
b Shanghai Jiaotong University Affiliated Sixth People’s Hospital, South
Campus, Shanghai 201499, P. R. China
‡ These authors contributed equally to this work.
* Corresponding author: sunzl6@126.com; zhangfang@shnu.edu.cn

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Abstract
A novel mesoporous phenol-formaldehyde resin supported copper nanoparticles
was prepared by using a two-step protocol involved the melt infiltration of
copper nitrate hydrates and the subsequent template pyrolysis-induced in-situ
reduction of Cu(II) ions. Notably, this synthetic process effectively saved time
and reduced wastes since it didn’t use any solvents, capping and reducing
reagents. The obtained Cu NPs@MP catalysts had the large surface areas and
narrow pore size distributions. In addition, most of the Cu nanoparticles with the
sizes around 3-5 nm were highly dispersed in the pore channels of mesoporous
polymers. In the solvent-free Sonogashira reactions for the synthesis of ynones
from acyl chlorides and terminal alkynes, it exhibited much higher catalytic
reactivity than those of the commercial Cu powder and mesoporous silica
SBA-15 supported Cu nanoparticles. The excellent catalytic performance could
be attributed to the synergistic advantages of mesoporous structure,
monodispersed Cu nanoparticles and the surface hydrophobicity, which
stabilized and concentrated the reactants and increased the accessibility of active
sites as well as decreased the mass transfer resistance. Meanwhile, it could be
easily recycled and reused for at least ten times, showing a good stability under
solvent-free reaction conditions.

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Introduction
Driven by economic consideration and environmental concern, the
replacement of expensive precious metals by cheap and earth-abundant base
metals as the novel catalytic materials is one of major goals of s chemistry.1 In
this context, base-metal nanoparticles are among the very important catalytic
components because of the high accessible surface area and unique quantum
effect.2 Among various base-metal nanopaticles, copper nanoparticles (Cu NPs)
display the unique catalytic reactivity in a wide range of chemical synthesis and
energy related fields such as azide-alkyne cycloaddition,3 hydrogenation,4
reduction,5 oxidation6 and cross-coupling reactions7. Generally, Cu NPs with
small sizes are preferred since the particle size that less than 10 nm with a
narrow size distribution is believed to be most beneficial for their catalytic
efficiencies.8 However, the increased surface energy with the decreased particle
size inevitably causes the serious aggregation, thereby leading to the inferior
performances in the practical applications.9 A straightforward strategy to solve
this problem is using the support materials to disperse and fix the Cu NPs.10
Accordingly, the catalytic properties of the supported Cu NPs catalysts strongly
depend on the preparation method.11 To date, the impregnation, drying and the
subsequent reduction procedures with Cu metal salts as the precursors is the
most widely applied protocol for the preparation of supported Cu NPs
catalysts.12 Unfortunately, these composites were often obtained with
inhomogeneous nanoparticle size and dispersion after different reduction

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13
DOI: 10.1039/C7GC00219J
processes. For this reason, the additional capping agents were frequently used
to overcome this drawback.14 Obviously, this traditional multi-step operation
with the certain amounts of capping and reducing agents and massive solvents is
not a green and convenient process, which usually generates useless byproducts
and wastes time. Therefore, there is a critical need to develop a simple,
economical and environmentally friendly strategy for the preparation of the
efficient and stable solid-supported Cu NPs catalyst.
Recently, melt infiltration is considered as the novel promising technique for
the fabrication of nanoporous materials supported catalysts.15 It allows metal
salts to permeate into a porous support via capillary force without the addition of
any solvents and capping agents. This unique feature is of particular interest for
the fabrication of metal nanoparticles-incorporated mesoporous materials with
the high surface area and uniform pore size distribution. Specifically, this simple
preparation procedure avoids the redistribution of the precursor phase during
solvent removal.16 Moreover, the confined nanoscale channels of mesoporous
materials inhibit the tendency of metal nanoparticles to grow into the larger
crystallites through migration and coalescence of particles.17 The synergistic
effects from both the preparation method and the supports are expected to
provide excellent activity and selectivity superior to what can be obtained from
the traditional solid supported metal nanoparticles. Up to now, the utilization of
melt infiltration strategy for the preparation of mesoporous materials-support
metal nanoparticles is very rare. Moreover, in these previously reported

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examples, a necessary post-treatment to reduce the metal salts to metal particles
in the high temperature is an important cause for unwanted sintering of the
supported metal active species.18
Mesoporous polymers have attracted enormous interest for the design of
novel heterogeneous catalysts owing to their combined advantages of
mesoporous materials and organic polymers including large surface area, tunable
pore structure, high hydrophobicity and excellent stability in acid or base
media.19 Due to these distinctive properties, several different mesoporous
polymer supported metal nanoparticles have shown the enhanced catalytic
performances in comparison to mesoporous silica-based catalysts.20 However, to
our knowledge, the use of melt infiltration strategy for the green synthesis of
mesoporous polymer supported Cu NPs catalyst has not been reported so far.
Herein, for the first time, we demonstrated a facile capping and reducing
agents-free and solvent-free strategy for dispersing copper nanoparticles in the
channels of mesoporous phenol-formaldehyde polymer by a convenient two-step
protocol involved the melt infiltration of copper nitrate hydrates and the
subsequent template pyrolysis-induced in-situ reduction. The obtained composite
possessed high surface area, ordered mesoporous structure and monodispersed
Cu nanoparticles in the mesoporous channels with the size of about 3-5 nm.
Notably, this heterogeneous Cu catalyst exhibited excellent catalytic activity and
selectivity towards solvent-free synthesis of a variety of ynones from acyl
chlorides and terminal alkynes. Meanwhile, it could be easily reused and

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recycled for at least 10 times without the loss of the activity, shDoOwI: 1i0n.1g039a/C7gGCo0o02d19J
potential in the future industrial application.
Experimental Section
1. Sample Preparation
1.1 Synthesis of phenol-formaldehyde polymer with F127 template composite
(PF). Firstly, phenol-formaldehyde polymer with F127 template composite was
synthesized via evaporation-driven self-assembly method. In a typical procedure,
1.0 g phenol and 0.21 g aqueous NaOH solution (20 wt.%) were mixed and
stirred at 40oC for 0.5 h. Then, 1.72 g aqueous formaldehyde solution (37 wt.%)
was added dropwise into the mixture and continued to stir at 70oC for 2.0 h.
After the mixture was cooled down to room temperature, the pH value was
adjusted to 7.0 by adding a certain amount of aqueous HCl solution (2.0 mol/L).
Next, the phenol-formaldehyde resol oligomers were obtained after removing
water by rotary evaporation. The oligomers were then dissolved in ethanol to
remove NaCl precipitate. Subsequently, 5.0 g the as-prepared oligomers ethanol
solution (20 wt.%) was added into 20 g ethanol solution containing 1.0 g triblock
copolymer Pluronic F127 template (EO106PO70EO106). After stirring for 10 min,
the mixture was transferred into the dishes for evaporation at 25oC for 12 h and
further thermopolymerized at 100oC for 24 h. The final powder sample was
scratched from the dishes and vacuum dried at 80oC for 10 h.
1.2 Preparation of ordered mesoporous polymer supported copper nanoparticles

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catalyst (Cu NPs@MP). This novel catalyst was prepared by two-step solid-state
ball milling and in-situ pyrolyzed reduction procedures. Typically, a certain
amount of Cu(NO3)2·3H2O was mixed with 1.0 g as-synthesized
phenol-formaldehyde polymer with F127 template composite powder by the ball
milling for 12 h at 25oC. Then, this composite was transferred into quartz boat
and then pyrolyzed in N2 atmosphere at 350oC for 6.0 h with a heating rate of 2.0
oC/min. The obtained samples were denoted by the mass loadings of
Cu(NO3)2·3H2O in the initial mixture. Specifically, Cu NPs@MP-1, Cu
NPs@MP-2, Cu NPs@MP-3 and Cu NPs@MP-4 samples were prepared
according to the use of 50 mg, 75 mg, 100 mg and 125 mg Cu(NO3)2·3H2O,
respectively.
1.3 Synthesis of ordered mesoporous silica supported copper nanoparticles (Cu
NPs@SBA-15). Mesoporous silica SBA-15 was synthesized according to the
method reported by Zhao group.21a Then, 100 mg Cu(NO3)2·3H2O was mixed
with 1.0 g as-synthesized silica with P123 template by the ball milling for 12 h at
25oC. Then, this sample was transferred into quartz boat and then pyrolyzed in
o
N2 atmosphere at 350oC for 6.0 h with a heating rate of 2.0 C/min, resulting in
the final Cu NPs@SBA-15 sample.
1.4 Synthesis of hydrophobic ordered mesoporous silica supported copper
nanoparticles (Cu NPs@TMS-SBA-15). 1.0 g as-prepared Cu NPs@SBA-15 was
firstly dispersed in 50 ml toluene under N2 atmosphere.21b Then, 3.0 ml
ethoxytrimethylsilane (TMS-silane) was added dropwise into the above solution

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and allowed to stir for 12 h under reflux condition. The powdeDrOpI: 1r0o.1d03u9/cCt7GCw00a2s19J
filtered and washed thoroughly with absolute toluene to eliminate un-reacted
TMS-silane, followed by vacuum drying at 80oC for 12 h.
2. Characterization.
The copper loadings were determined on an inductively coupled plasma
optical emission spectrometer (ICP-OES, Varian VISTAMPX). The copper
electronic states were analyzed by X-ray photoelectron spectroscopy (XPS,
Perkin-Elmer PHI 5000C ESCA). All the binding energy values were calibrated
by using C1s = 284.6 eV as a reference. Fourier transform infrared (FTIR)
spectra were obtained using Thermo Nicolet Magna 550 spectrometer.
UV-visible spectroscopy (UV-vis) was obtained on Shimadzu MC-2530
spectrometer. Thermogravimetric-mass spectrometric (TG-MS) data was
o
received on a Setaram TGA92 analyzer at a 2.0 C/min heating rate in an inert
helium atmosphere. X-ray diffraction (XRD) patterns were obtained on a Rigaku
D/maxr B diffractometer with Cu Kα radiation. N2 adsorption-desorption
isotherms were measured at 77 K with a Micromeritics TriStar II 3020 analyzer.
Transmission electron microscope images were acquired on a JEOL JEM2011
microscope. Toluene and Water vapour absorption tests were carried out on an
intelligent gravimetric analyse (Hiden Isochema IGA-002/3) by adding a dosed
amount of high-purity vapor directly into the sample chamber and recording the
weight change after stable equilibrium pressure was reached.

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3. Activity test
In a typical run of solvent-free Sonogashira coupling reaction, 0.50 mmol
phenylacetylene, 1.5 mmol benzoyl chloride, 1.5 mmol triethylamine and 1.0
mol% Cu NPs@MP catalyst were mixed in a 25 ml oven-dried reaction tube.
After reacting in nitrogen atmosphere at 40oC for 8.0 h, the reaction mixture was
filtrated and then extracted with toluene, followed by analyzing on a
high-performance liquid chromatography with mass spectrometry (HPLC/MS,
Agilent 6410B). The reproducibility was checked by repeating experiments at
least three times and was found to be within acceptable limits (±5%).
In order to determine the recyclability of Cu NPs@MP-3 catalyst, it was
allowed to settle down after each run of reactions and the clear supernatant liquid
was decanted slowly. The residual solid catalyst was washed thoroughly by
toluene and re-used with a fresh charge of the reactants for subsequent recycling
under the same reaction conditions. The content of copper leached off from the
heterogeneous catalyst was also calculated by ICP analysis.
Results and discussion
The preparation protocol of the series of Cu NPs@MP samples was
illustrated in Scheme 1. Phenol-formaldehyde polymer with F127 template
composite (PF) was firstly synthesized according to the previously reported
approach. Next, a certain amount of copper nitrate hydrate was infiltrated into
the confined place between polymer wall and F127 template via a simple ball

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milling treatment. The obtained copper salt containing polymer composite
(Cu(II)@PF) was further pyrolyzed in N2 atmosphere to remove F127 template
and simultaneously the pyrolysis-generated reducing gas in-situ reduced Cu(II)
species to metallic Cu(0) in the pore channels of ordered mesoporous polymer,
resulting in ordered mesoporous phenol-formaldehyde polymer supported copper
nanoparticles materials (Cu NPs@MP).
Scheme 1 Schematic illustration of the synthesis of ordered mesoporous polymer
supported Cu NPs catalyst (Cu NPs@MP).
Inductively coupled plasma (ICP) analysis revealed that the copper content in
the series of Cu NPs@MP samples was varied from 2.95 to 6.87 wt.%,
confirming the existence of copper species (Table 1). Furthermore, X-ray
photoelectron spectroscopy (XPS) spectra of the representative Cu NPs@MP-3
sample (Figure 1) indicated that the peaks at 932.9 and 952.7 eV correspond to
2p3/2 and 2p1/2 binding energies of zero-valent copper.22 Meanwhile, UV-Vis
spectrum of Cu NPs@MP-3 (Figure 2) exhibited the remarkable broad
absorption in the visible region (400-700 nm) in comparison with

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Table 1 Cu loadings and textural parameters of different Cu-containing catalysts.
Sample
Cu NPs@MP-1
Cu (wt %) SBET (m2/g) Dp (nm) Vp (cm3/g)
2.95
4.37
5.66
6.87
5.43
5.64
5.65
464
426
391
367
565
370
306
4.6
4.4
4.3
4.1
5.2
4.2
3.1
0.41
0.38
0.35
0.33
0.60
0.41
0.22
Cu NPs@MP-2
Cu NPs@MP-3
Cu NPs@MP-4
Cu NPs@SBA-15
Cu NPs@TMS-SBA-15
Cu NPs@MP-3a
a after ten repetitions.
Cu(NO3)2·3H2O precursor, which could be ascribed to the plasmon resonance
bands of Cu nanoparticles.23 These results clearly demonstrated the successful
incorporation of metallic Cu(0) species in the phenol-formaldehyde polymer. To
explore the unique redox reaction in our preparation process, we firstly analyzed
the electric state of Cu species in Cu(II)@PF-3 by XPS analysis (Figure 1). The
results showed that the measured binding energies of Cu 2p3/2 and Cu 2p1/2 in
Cu(II)@PF-3 were 935.3 and 955.2 eV, respectively, which indicated that Cu

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Figure 1 Cu 2p XPS spectra of Cu(II)@PF-3 and Cu NPs@MP samples.
Figure 2 UV-Vis spectra of Cu(NO3)2·3H2O, Cu(II)@PF-3 and Cu NPs@MP
samples.

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Figure 3 TG-MS spectra of Cu(II)@PF-3 sample.
species were present in divalent state. Furthermore, two shake-up lines located at
944.1 and 963.0 eV were observed, which was indicative of the paramagnetic
chemical state of Cu2+.22 Also, UV-Vis spectrum of Cu(II)@PF-3 only showed
the existence of absorption peak from 250-450 nm, which was derived from the
aromatic framework of the polymer. On basis of these data, we suggested that
the ball-milling treatment didn’t reduce Cu(II) salt to Cu nanoparticles and the
thermal pyrolysis caused Cu(II) ions to Cu nanoparticles. Next, we used TG-MS
analysis to confirm this valence state transformation.24a As shown in Figure 3,
the thermogravimetric plot of Cu(II)@PF-3 sample presented one major weight
loss from 280 to 380 °C. The coupled TG-MS analysis reveals that the very rich
spectrum that contained several mass fragments was observed. The species with
m/z = 16, 28, 42 and 56 could be probably assigned to methane, carbon
monoxide, propene from the hydrophobic part of the polyalkeneoxide and the
oligomer fragments, respectively.24b These results confirmed that the reduction

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from Cu(II) ions to Cu nanoparticle was due to the existence of these reducing
species in the pyrolysis treatment. Meanwhile, this process also generated a large
amounts pore due to the removal of F127 template.
Figure 4 N2 adsorption-desorption isotherms (a) and pore size distribution (b) of
different Cu NPs@MP catalysts.
N2 sorption‐desorption isotherms (Figure 4a) of all the Cu NPs@MP samples
displayed the representative type IV curves with pronounced H2 hysteresis loops
and large uptakes at the relative pressure at p/p0=0.45-0.70, which demonstrated
that these samples had a mesoporous structure.25 Their pore size distribution
curves from the adsorption branches by using BJH model (Figure 4b) confirmed
the presence of relatively uniform mesopores in these materials. According to the
N2 isotherms, the textural parameters were summarized in Table 1. These
mesoporous Cu NPs-containing polymers had high surface areas (367-464 m2/g)
and large pore volumes (0.33-0.41 cm3/g). The mean mesopore sizes of the

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samples ranged from 4.1-4.6 nm, slightly declining with the increDaOsIe: 10l.1o03a9d/Ci7nGgC00o2f19J
Cu NPs, which was due to the occupation of the pore channels by the Cu NPs.26
Figure 5 Small-angle XRD patterns (a) and wide-angle XRD patterns (b) of
different Cu NPs@MP catalysts.
Small-angle XRD pattern (Figure 5a) of the pristine mesoporous
phenol-formaldehyde resin (MP) exhibited one intense peak indicative of (100)
reflection and two weak peaks assigned to (110) and (200) reflections in the
enlarged inset picture, confirming the ordered 2-dimensional hexagonal
mesostructure (p6mm). After the immobilization of Cu NPs, these Cu NPs@MP
samples also displayed one peak indexed to the (100) diffraction, which
confirmed the mesoporous structures were preserved.27 The disappearance of
(110) and (200) diffractions in these samples indicated the decreased order
degree in comparison with the pristine mesoporous phenol-formaldehyde resin.
Meanwhile, the peak intensities of (100) diffraction peak were gradually

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decreased with the increase amounts of Cu(II) salt in a series ofDCOI:u10.N103P9/sC@7GCM002P19J
samples, which implied that the introduction of Cu NPs might slightly disturb
the ordered structure of mesoporous polymer. The (100) peak shifted to the
higher 2θ values with the increase amounts of Cu NPs, which was maybe due to
the increase in the pore thickness.28
Figure 6 TEM images and particle size distributions (inset) of Cu NPs@MP-1
(a), Cu NPs@MP-2 (b), Cu NPs@MP-3 (c), Cu NPs@MP-4 (d) samples.
Furthermore, the Cu nanoparticles diameter and size distribution of these
four Cu NPs@MP materials were analyzed by TEM images (Figure 6). The
results revealed that the typical two-dimensional hexagonal arrangements of
one-dimensional channels with uniform sizes were observed in large domains for

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all the samples. Meanwhile, TEM images showed that theDOsI:m10.a10l3l9/C7mGCe0t0a21l9J
nanoparticles were well-dispersed inside the channels without the obvious
aggregation, even for Cu NPs@MP-3 with 5.6 wt.% loading. Next, the
respective particle size distributions of these Cu NPs@MP samples were
obtained by counting the sizes of a certain amounts of Cu NPs. The result
revealed that the dispersions of Cu NPs were related to their particle loadings.
With the increasing Cu NP loadings, the particle sizes increased accordingly and
meanwhile the particle dispersion was becoming broader. Accordingly, the
particle size distribution of Cu NPs@MP-1 was in the range of 3.5-4.5 nm while
the particle size distribution of Cu NPs@MP-4 was around 4.0-5.5 nm. But, the
particle sizes of most of the Cu NPs were smaller than the pore sizes of the Cu
NPs@MP samples, indicating that most of the nanoparticles were existed in the
mesopore channels. Moreover, wide-angle XRD patterns (Figure 5b) exhibited
that no obvious characteristic peaks of Cu NPs were obtained in the Cu
NPs@MP-1 and Cu NPs@MP-2, which was maybe due to the Cu nanoparticles
with the relative low loadings were highly dispersed in the mesoporous polymer.
But, the peak around 2θ=43.3o corresponding to (111) crystal plane was observed
in Cu NPs@MP-3. Also, Cu NPs@MP-4 showed two pattern peaks at 43.3o and
50.3o, which could be assigned to the crystal planes of (111) and (200),
respectively.29 This phenomenon was related to the large particle size and the
slight particle aggregation in Cu NPs@MP-4, in accordance with TEM result.

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a
DOI: 10.1039/C7GC00219J
Table 2 Catalytic performances of different Cu NPs-containing catalysts
Entry
Sample
Blank
Cu loading (wt.%) Yield (%)
TONd
1b
2
/
0
0
Cu-P
/
26
74
55
63
69
64
96
87
13.0
37.0
27.5
31.5
34.5
32.0
48.0
43.5
3
Cu NPs@MP-3
Cu NPs@SBA-15
Cu NPs@MP-1
Cu NPs@MP-2
Cu NPs@MP-4
Cu NPs@MP-3
Cu NPs@TMS-SBA-15
5.66
5.43
2.95
4.37
6.87
5.66
5.64
4
5
6
7
8c
9
a Reaction conditions: phenylacetylene (0.50 mmol), benzoyl chloride (0.75 mmol), 1.0 mol% catalyst, Et3N
b
c
d
(1.5 mmol), 40oC, 6.0 h, N2 atmosphere. no catalyst reaction time = 8.0 h TON = nprod./ncat., which is
defined as the total moles of product formed (nprod.) divided by total moles of catalyst employed in the
reaction (ncat.).
Ynones are a class of alkynyl carbonyl compounds of considerable interest
because they are important structural motifs in natural products. Meanwhile, they
are usually employed as the precursors to prepare various valuable heterocyclic
derivatives such as pyrroles, furans, furanones, pyrazoles, isoxazoles,
indolizidinones, pyrimidines and pyridinones.30 Recently, the catalytic coupling
of acyl chlorides and terminal alkynes to ynones by using copper catalysts,
known as the Sonogashira-type reaction, attracted much attention since this
process avoids the use of a large amount of sensitive metal acetylides.31 To

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investigate the utility of our novel Cu NPs@MP catalysts, we firsDtlOyI: 1f0o.10c3u9/sCe7GdC0o02n19J
the preparation of 1,3-diphenyl-2-propyn-1-one from benzoyl chloride and
phenylacetylene. As shown in Table 2, the control test revealed that the blank
experiment without the Cu-based catalyst didn’t give any products (entry 1).
Next, a series of Cu NPs@MP catalysts with different loadings were screened
and the results showed that Cu NPs@MP-3 displayed the good conversion (74%)
and excellent selectivity (100%) after 6.0 h. The inferior catalytic performances
of Cu NPs@MP-1 and Cu NPs@MP-2 were probably attributed to the lower Cu
NPs contents, which resulted in the decreased interaction between the reactants
and the active sites. Meanwhile, the reduced catalytic efficiency of Cu
NPs@MP-4 was maybe assigned to the smallest surface area and pore size,
which increased the mass transfer resistance. Moreover, the bigger particle size
and the broader particle dispersion decreased the accessibility of active species.
Furthermore, the effect of the reaction parameters including catalyst amounts,
reaction temperature and reaction time, different bases and solvents in the Cu
NPs@MP-3 catalyzed model reaction was investigated (Table S1-S4).
Satisfactorily, Cu NPs@MP-3 achieved the excellent conversion (96%) and
selectivity (100%) by using triethylamine as the base at 40oC for 8.0 h under
solvent-free condition.

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Figure 7 Water and toluene absorption tests of Cu NPs@MP-3 sample.
To explain this excellent catalytic performance of Cu NPs@MP-3, three
control catalysts including the commercial Cu powder (Cu-P), mesoporous silica
SBA-15
supported
Cu
nanoparticle
(Cu
NPs@SBA-15)
and
trimethylsilyl-functionalized mesoporous silica SBA-15 supported Cu
nanoparticle (Cu NPs@TMS-SBA-15) were studied. In the same reaction
conditions, the yields of Cu-P and Cu NPs@SBA-15 were 26% and 55%,
respectively (Table 2). TEM image of Cu-P revealed that the Cu particles size
was about 1-2 µm (Figure S1). It represented the decreased surface active sites in
comparison with Cu NPs@MP-3, resulting in the remarkable decrease in the
activity. Furthermore, ICP tests (Table 1) confirmed the similar Cu loadings
between Cu NPs@MP-3 and Cu NPs@SBA-15. Also, XRD pattern (Figure S2)

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and TEM picture (Figure S3) of Cu NPs@SBA-15 showed that it had the
two-dimensional hexagonal ordered mesoporous structure and meanwhile Cu
NPs with a size around 4.0 nm were highly dispersed in the mesoporous
channels. Also, based on the N2 sorption isotherm (Figure S4) of Cu
NPs@SBA-15, the surface area, pore volume and pore size were determined as
565 m2/g, 5.2 nm and 0.60 cm3/g, respectively. Owing to their similar pore
structures, we supposed the pore surface hydrophobicity played an important in
their different reactivity. In order to prove this hypothesis, water and toluene
vapor adsorption tests of Cu NPs@MP-3 were investigated. As shown in Figure
7, it exhibited the higher adsorption capacity (24.8%) for toluene and the lower
adsorption capacity (10.9%) for water. These results clearly confirmed the pore
surface of Cu NPs@MP-3 was hydrophobic, which can effectively stabilize and
concentrate the reactants, especially for solvent-free reaction condition.32 To
further confirm this phenomenon, Cu NPs@TMS-SBA-15 with hydrophobic
groups was also prepared by using post-grafting approach. In comparison with
Cu NPs@SBA-15, FT-IR spectrum (Figure S5) of Cu NPs@TMS-SBA-15
showed that the remarkable decrease intensity of the broad band around 3420
cm-1 indicative of Si-OH groups and the new vibration peaks around 2964 and
2906 cm-1 assigned to the stretching vibration of methyl groups clearly indicated
the successful modification of TMS groups on the SBA-15 support. Accordingly,
we tested the catalytic performance of Cu NPs@TMS-SBA-15 in the
solvent-free Sonogashira reaction between phenylacetylene and benzoyl chloride.

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As expected, the yield was increased to 87%, which result furtherDOdIe: 1m0.10o3n9/sCt7rGaC0te02d19J
the merit of hydrophobic pore surface. However, the inferior catalytic efficiency
of Cu NPs@TMS-SBA-15 compared to Cu NPs@MP-3 was maybe due to the
decreased surface area and pore size since the post-grafting treatment usually
partially blocked the pore mouth or the pore channel.21b
Table 3 Reaction scope of Cu NPs@MP-3 catalyzed Sonogashira reactionsa
Entry
Acyl chlorides
Alkynes
Product
Yield (%)
TON b
O
1
99
49.5
O
O
2
3
4
85
96
71
42.5
48.0
35.5
Cl
Br
Br
O
O
Cl
Cl
Cl
O
O
O2N
Cl
NO2
5
6
99
83
49.5
41.5
O
7
71
35.5
Cl
a Reaction conditions: alkyne (0.5 mmol), acyl chloride (0.75 mmol), Et3N (1.5 mmol), 1.0 mol% Cu
o
b
NPs@MP-3, 40 C, 8.0 h. TON is defined as the total moles of product formed (nprod) divided by total
moles of catalyst employed in the reaction (ncat). TON = nprod/ncat.

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Encouraged by the above results, we extended the scope of thDisOI:s1o0.1l0v3e9/nC7tG-Cf0r0e2e19J
Sonogashira reaction by using various derivatives of acyl chlorides and terminal
alkynes. As shown in Table 3, the reaction with various derivatives of
phenylacetylene with substituents such as methyl, bromo, chloro, and nitro also
gave good yields of the corresponding products (entry 1-4). Also, aliphatic
chloride reacted smoothly with terminal alkyne (entry 5). Furthermore, benzoyl
chloride substituted with methoxy group still gave the the corresponding ynones
in excellent yield (entry 6). Under the same conditions, cyclic alkyne derivatives
afforded the desired product with the moderate yield (entry 7).
An important advantage of Cu NPs@MP-3 catalyst was its easy recycle and
reuse.33 Figure 8 showed the recyclability of the Cu NPs@MP-3 catalyst during
solvent-free Sonogashira reaction between benzoyl chloride and phenylacetylene.
No significant reduce was found in the yields after being used repetitively ten
times, which exceeded the best results previously reported in the literature. ICP
analysis revealed that the copper content was 5.65 wt.% in the recycled Cu
NPs@MP-3 catalyst, which indicated that only about 0.17% of the Cu species
leached off after ten cycles. This result confirmed that the mesoporous structure
could inhibit the Cu NPs leaching. Moreover, low-angle XRD pattern (Figure S6)
demonstrated that ordered 2-D mesostructure was preserved after the recycle test.
N2 sorption isotherm showed the typical type IV isotherm with the capillary
condensation step (Figure S7). However, the surface area and pore size were 206
m2/g and 3.1 nm, respectively (Table 1). Also, TEM image (Figure S8) revealed

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that the partial particle aggregation existed, which probably causeDdOIt:h10e.10d39e/Cc7rGeCa00s2e19J
of catalytic activity of Cu NPs@MP-3 after ten repetitions. Thus, these results
was maybe responsible for the slight decrease reactivity of the recycled Cu
NPs@MP-3 catalyst after ten repetitions.34
Figure 8 Recycling tests of Cu NPs@MP-3 catalyst in solvent-free Sonogashira
reaction between benzoyl chloride and phenylacetylene. Reaction conditions
were in Table 3.
Conclusion
In summary, we have developed a facile approach to prepare highly active
mesoporous polymer supported copper nanoparticles (Cu NPs@MP) through the
incorporation of copper nitrate hydrates into the support by melt infiltration and

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DOI: 10.1039/C7GC00219J
the subsequent in-situ reduction of Cu(II) ions by template pyrolysis. Notably, it
displayed the remarkable increase in the catalytic activity in solvent-free
Sonogashira reactions between acyl chlorides and terminal alkynes compared to
the commercial Cu powder. In comparison with mesoporous silica SBA-15
supported Cu nanoparticles, it also exhibited the higher catalytic reactivity. The
systematic analysis demonstrated that the mesoporous structure, the
monodispersed Cu nanoparticles and the surface hydrophobicity could enrich the
reactants and increase the accessibility of active sites as well as reduce the
diffusion limitation. Moreover, it could be easily recycled reused at least ten
times without the significant loss of catalytic activity. This work provides a
general approach towards the facile and green preparation of a large variety of
supported base metals nanoparticles for more environmental friendly chemical
transformations.
Acknowledgements
This work was supported by the Natural Science Foundation of China
(21677098), the Program for Professor of Special Appointment (Eastern Scholar)
at Shanghai Institutions of Higher Learning (TP2016034) and PCSIRT
(IRT-16R49).
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