Stainless steel mesh-GO/Pd NPs: Catalytic applications of Suzuki-Miyaura and Stille coupling reactions in eco-friendly media

Article abstract of DOI:10.1039/c9gc00889f

The immobilization of palladium nanoparticles (Pd NPs) on stainless-steel mesh is described in two short steps via deposition of graphene oxide (GO) on the stainless-steel mesh (mesh-GO) by electrophoretic deposition (EPD), preparation of Pd NPs using laser ablation in liquids (LAL) and finally the immobilization of Pd NPs on the mesh-GO by immersion in a Pd NP colloidal solution. The novel, efficient and reusable mesh-GO/Pd catalyst was characterized by various techniques such as SEM, EDS, UV-Vis and FT-IR spectroscopy and its catalytic activity was investigated for the Suzuki-Miyaura and Stille coupling reactions in ethanolic water.

Full text of DOI:10.1039/c9gc00889f

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Stainless steel mesh-GO/Pd NPs: catalytic application for Suzuki-
Miyaura and Stille coupling reactions in eco-friendly media†
Bahareh Feizi Mohazzab,a Babak Jaleha,*, Zahra Issaabadi,b Mahmoud Nasrollahzadehb,* and Rajender
5
S. Varmac,*
aDepartment of Physics, Faculty of Science, Bu-Ali Sina University, Postal Code 65174 Hamedan, Iran. E-mail: jaleh@basu.ac.ir
bDepartment of Chemistry, Faculty of Science, University of Qom, Qom 3716146611, Iran. E-mail: mahmoudnasr81@gmail.com; Fax: +98 25
32103595; Tel: +98 25 32850953
cRegional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University, Šlechtitelů 27, 783
10 71 Olomouc, Czech Republic. E-mails: rajvarma@hotmail.com; Varma.Rajender@epa.gov; Fax: +1 (513)-569-7677; Tel.: +1 (513)-487-2701
† Electronic supplementary information (ESI) available: Additional characterization studies supporting the results which include NMR spectra.
The immobilization of the palladium nanoparticles (Pd NPs) on
expensive, sensitive to air and moisture, get easily poisoned, and
the stainless-steel mesh is described in the two short steps via 65 require the addition of an organic ligand which pollutes the
15 deposition of graphene oxide (GO) on the stainless-steel mesh
(mesh-GO) by electrophoretic deposition (EPD), preparation of
Pd NPs using laser ablation in liquids (LAL) and finally the
immobilization of Pd NPs on the mesh-GO by immersion in Pd
environment, and causes product separation issues.29-30
Heterogeneous catalysts can possibly be the way forward to solve
this problem.31-33
As a part of our ongoing catalysis program of depositing metal
NPs colloidal solution. The novel, efficient and reusable mesh- 70 nanoparticle (MNPs) on the GO surface and their application in
20 GO/Pd catalyst was characterized by various techniques such as
SEM, EDS, UV-Vis and FT-IR spectroscopy and its catalytic
activity was investigated for the Suzuki-Miyaura and Stille
coupling reactions in ethanolic water.
the reduction and cross-coupling reactions,34,35 herein, we have
investigated the preparation of separable Pd NPs on the
GO/stainless steel mesh using LAL process and EPD technique
and explored its application as a recoverable and reusable catalyst
75 for the Suzuki-Miyaura and Stille coupling reactions.
25 1. Introduction
Carbon nanostructures like carbon nanotubes, graphene and
Experimental
graphene oxide (GO) attain
opportunities to create
Reagents and instruments
Chemical materials were obtained from the Sigma-Aldrich,
nanocomposites with unique properties.1-7 GO has attracted
tremendous attention due to its exceptional properties in various 80 Merck KGaA Company and used without further expurgation.
30 fields, namely catalysis and nanocomposites;8-10 they are related
to its unique structure that comprise sp2-bonded carbon network
with strong Van der Waal interactions rendering them
conductive.9 Additionally, a large theoretical specific surface area
Stainless steel mesh (200 mesh, 1 cm2) was used as a substrate
for deposition. To reassure the fabrication Pd NPs owing to laser
ablation optical transmittance spectrum was recorded with UV-
Vis spectrophotometer (PG instruments Ltd, T80) for the
and high inherent mobility make it a better candidate for 85 obtained Pd NPs colloid. The functional group information for
35 application as a coating layer. Several types of deposition
methods for GO coating are known, like for instance chemical
vapor deposition (CVD)11, evaporation-Assisted Deposition
(EAD)12, electrophoretic deposition (EPD);13-15 the last one has
samples was attained by Fourier transform infrared (FT-IR,
Thermo Nicolet, USA). FESEM analysis was applied to evaluate
the morphology of the obtained samples using Cam scan
Mv2300. Energy-dispersive X-ray spectrometry microprobe
garnered a lot of attention because of it cost-effectiveness and 90 (EDX) analysis was used to determine the elemental composition
40 easy way of deposition,16,17 in a two-electrode cell filled by a
suspension.18 To gain effectual deposition, it is essential to have a
stable suspension involving charge-free particles wherein an
applied electric field move the charge particles toward the
of the specimens. The loading and the leaching of Pd were
analyzed by ICP-MS (Inductively Coupled Plasma Mass
Spectrometry) analysis (ELAN DRC-e model). 1H NMR spectra
were recorded on a Bruker Avance DRX spectrometer at 500
opposite electrode and assemble at the deposition electrode;18 95 MHz (CDCl3 with TMS as the standard). Melting points were
45 such deposition of graphene oxide on different substrates with the
EPD and a uniform suspension of GO has been explored.13-15
These deposited electrodes can be used as a substrate for
nanoparticles deposition because of GO's porosity and its large
measured on a BUCHI 510 melting point apparatus and are
uncorrected.
Synthesis of graphene oxide (GO)
specific surface area. Some of the deployed methods to attach 100 The used method for the synthesis GO is the modified Hummer’s
50 nanoparticles on GO’s surface include the laser ablation and
chemical reduction methods. In recent years, laser ablation of
solid sample in liquids is one of the accepted methods19-21 and it
has appeared as an adaptable method to fabricate nanoparticles.20-
method through oxidation of graphite.36 Graphite flakes (2.0 g)
and NaNO3 (2.0 g) were to be confected in 50 mL of H2SO4
(98%) and it was placed under continuous stirring in ice bath (0-
5° C) for 2 h. Then, KMnO4 (6.0 g) was added gradually to
22 There are some studies describing the fabrication of Pd NPs by 105 suspension with constant stirring, to kept reaction temperature
55 LAL with and without surfactant for diverse applications such as
under 15 °C. The mixture was stirred at 35 °C until its color
changed to brownish. Next, this solution was diluted by 200 mL
deionized water and subsequently, H2O2 (10 mL) was slowly
added; a brilliant yellow solution ensued. For purification, the
catalyst and hydrogen storage.22-24
Suzuki-Miyaura and Stille coupling reactions is one of the
main innovative pathway for the synthesis of biphenyls as
versatile organic intermediate.25,26 During the past decades, Pd- 110 mixture was filtered and the residue centrifuged with 1:10 HCl
60 catalyzed C-N and C-C coupling reactions have become
widespread because of their good selectivity, fast reaction rates,
high production yield, and high turnover frequency in various
synthetic protocols.27,28 However, Pd-based catalysts are
and finally with deionized water to remove acid. GO powder was
thus obtained by drying in vacuum oven at 100 °C.
Optimization conditions of electrodeposited GO coating
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The deposition quality depended on several experimental
factors, for instance the concentration of the GO suspension, the
separation of 10 mm and were connected to a DC power supply.
After preparing the GO solution (3.0 mg/mL) the EPD process
applied direct current (DC) voltage and the deposition’s time. 40 was conducted under a DC voltage of 25 V and the deposition
With regard to importance of these factors in EPD process, we
first optimized the main factors. To investigate the effects of GO
density on deposition behaviour, GO on stainless steel mesh, the
constant application potential and application time were selected
for five concentrations of the synthesized GO suspensions. To
attain different concentration of the GO suspension, varying
time of 10 min. To deposit adequate thickness of GO on
substrate, EPD was repeated twice. Then, the specimens were
heated at 100 °C for 2 h in a vacuum oven and termed mesh-GO.
(Figure 2a).
5
45
Pd NPs deposition on mesh-GO
10 amount of GO was dispersed in 40 mL distilled water; the five
such solutions were labelled, s1-s5 (1.0, 2.0, 3.0, 4.0 and 5.0
mg/mL). Before and after EPD process, specimens’ mass was
The Pd NPs were deposited on mesh-GO using the LAL and was
carried out as follows: The mesh-GO was immersed in cell filled
with deionized water to hang the specimens. At the same time,
weighed, the area of substrate was about 1 cm2. The weight 50 the palladium target (99.9%, Aldrich) is placed at the bottom of
difference for samples before and after deposition confirmed the
15 deposited mass of GO on substrate. With regard to difference
between samples’ mass, the s3 was chosen as optimum
concentration because the GO on s4 and s5 samples were
cell and to reduce the absorption of laser wavelength, about 2 mm
of water covers the whole target surface. For ablation process a
fiber laser (RFL-P30Q) is exploited at 1064 nm with 100 ns
duration, 1.5 mJ pulse energy, about 59.68 J cm2 laser pulse
deposited as bulk, so these samples did not serve our defined 55 fluence and 20 KHz repetition rate. Then, irradiation beam was
purpose. To survey the influence of DC voltage on deposition
20 process and deposition time, EPD was performed under various
conditions at constant concentration (3 mg/ml) while the applied
voltage was being optimized, the deposition time was stabilized
and vice versa.
Deposited mass was drawn as a function of concentrations,
25 applied voltages and deposition time (Figure 1). According to the
obtained results, the optimum value of GO’s concentration, DC
voltage and deposition’s time are selected 3.0 mg/mL, 25 V and
10 min, respectively.
focused through a quartz lens to 40 µm spot size. LAL process
was performed on palladium target over a rectangular area of 7
mm×7 mm horizontally with step of 10 μm in y-direction. The
cell was kept under constant stirring using a stir plate, in a way
60 that the magnet did not collide with the specimens and palladium
target. As LAL process was being performed, formation of Pd
NPs in DI water and deposition of Pd NPs on mesh-GO was
observed, simultaneously. In typical LAL as the ablation time
increases the ablation rate decreases due to the absorption of laser
65 beam by colloidal NPs.
Consequently, the preparation Pd NPs and their deposition on the
surface of samples in one-step is advantageous; during laser
ablation a portion of ensuing Pd NPs deposited on mesh-GO
surface. LAL was applied for about 3 min when the laser ablation
30 Preparation of mesh-GO composite coating
Suspension of the dispersed graphene oxide was prepared by
adding 0.12 g GO powder to 40 mL distilled water which was
diffused for 1 h by ultrasonic probe at room temperature. The 70 process was finished, stirring was continued for 5 min. LAL was
stainless-steel mesh was washed with distilled water and acetone,
35 respectively. Due to the negative charge of the GO the stainless-
steel mesh serves as the anode, while a piece of copper plate acts
as a cathode, for the EPD. These plates vertically faced with a
done for 15 min, just to prevent increasing the colloidal solution’s
temperature. Figure 2b illustrates the experimental setup for Pd
NPs deposition on mesh-GO.
75
Figure 1. Deposited GO’s mass on stainless steel mesh as a function of concentration (a), applied voltage (b) and deposition time(c).
2| Green Chem., [2019], [vol], 00–00
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Figure 2. A schematic of samples preparation. EPD process to prepare mesh-GO samples (a) and deposition Pd NPs on mesh-GO (b)
Investigation of catalytic activity using mesh-GO/Pd
5
Aryl halide (1.0 mmol) was dissolved in 8 mL H2O:EtOH (1:1)
and placed in a 50 mL round bottom flask. 1.1 mmol of
phenylboronic acid (or tributylphenylstannane) and 2.0 mmol of
K2CO3 were added to this mixture. The mesh-GO/Pd (0.07 g) was
then added, the flask was stirred under thermal conditions at 90
10 °C for the appropriate time and monitored by TLC. After the
consumption of the aryl halide, the reaction mixture was cooled
and the mesh-GO/Pd was filtered out. The H2O:EtOH in the
filtrate was removed to yield a solid product which was further
purified by flash chromatography on silica gel to afford pure
15 biaryls. All the synthesized products described herein are known
and their melting points were found to be consistent with
previously reported values in the literature.
3. Results and discussion
20 Characterization of catalyst
35
Figure 3. UV-Vis spectrum of the Pd NPs in water medium.
In contrast to earlier GO/Pd nanocomposite,35 the present
nanocatalyst could be easily separated from the reaction mixture
without centrifugation, which is a clear advantage compared to
the aforementioned nanocomposite. The catalyst was
25 characterized using UV-Vis, FT-IR, SEM, and EDS.
During the laser ablation, changing color of DI water’s to dark
brown indicated the formation of Pd NPs. However, to confirm
fabrication of Pd NPs in DI water, UV-Vis spectroscopy was
used in the range of 200-800 nm. The absorption spectrum of Pd
30 NPs colloid is shown in Figure 3. The impulse of surface
Plasmon vibrations in the Pd NPs are around 250 nm. The UV-
Vis results are in acceptable agreement with other available
results.25,35,36
FT-IR spectroscopy affords a clear image of functional groups
of the materials. In order to investigate functional groups of
mesh-GO and mesh-GO/Pd, the FT-IR analysis is used. For this
40 analysis, the surface of samples (both mesh-GO and mesh-
GO/Pd) are excoriated by stainless steel spatula several times in
the same direction until the small value of material is collected,
the obtained results are shown in Figure 4. Compared with
spectra of typical GO powder in Figure 4a and other literatures,38-
45 41 spectra of mesh-GO (Figure 4b) shows a significant decrease in
the intensity of oxygen functional groups. It is worth mentioning
here that during EPD process GO slightly gets reduced.42 In
addition, the FT-IR analysis of the mesh-GO and mesh-GO/Pd
(Figure 4c) confirmed that loading Pd NPs on mesh-GO did not
50 affect GO’s functional groups. The mesh-GO/Pd spectrum shows
a shift in wavenumber of functional groups, but it is not
significant; probably owing to the immobilization of Pd NPs.40
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