Pd supported on clicked cellulose-modified magnetite-graphene oxide nanocomposite for C-C coupling reactions in deep eutectic solvent

Article abstract of DOI:10.1016/j.carbpol.2020.117109

Cellulose-modified magnetite-graphene oxide nanocomposite was prepared via click reaction and utilized for immobilization of palladium (Pd) nanoparticles without using additional reducing agent. The abundant OH groups of cellulose provided the uniform dispersion and high stability of Pd nanoparticles, while magnetite-graphene oxide as a supporting material offered high specific surface area and easy magnetic separation. The as-prepared nanocomposite served as a heterogeneous catalyst for the Heck and Sonogashira coupling reactions in various hydrophilic and hydrophobic deep eutectic solvents (DESs) as sustainable and environmentally benign reaction media. Among the fifteen DESs evaluated for coupling reactions, the hydrophilic DES composed of dimethyl ammonium chloride and glycerol exhibited the best results. Due to the low miscibility of catalyst and DES in organic solvents, the separated aqueous phase containing both of the catalyst and DES can be readily recovered by evaporating water and retrieved eight times with negligible loss of catalytic performance.

Full text of DOI:10.1016/j.carbpol.2020.117109

Carbohydrate Polymers 251 (2021) 117109
Contents lists available at ScienceDirect
Carbohydrate Polymers
journal homepage: www.elsevier.com/locate/carbpol
Pd supported on clicked cellulose-modified magnetite-graphene oxide
nanocomposite for C-C coupling reactions in deep eutectic solvent
a,
b
a,
b,
c
c
Mahsa Niakan , Majid Masteri-Farahani
*, Hemayat Shekaari , Sabah Karimi
a
Faculty of Chemistry, Kharazmi University, Tehran, Iran
b
Research Institute of Green Chemistry, Kharazmi University, Tehran, Iran
c
Department of Physical Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz, Iran
A R T I C L E I N F O
A B S T R A C T
Keywords:
Cellulose-modified magnetite-graphene oxide nanocomposite was prepared via click reaction and utilized for
immobilization of palladium (Pd) nanoparticles without using additional reducing agent. The abundant OH
groups of cellulose provided the uniform dispersion and high stability of Pd nanoparticles, while magnetite-
graphene oxide as a supporting material offered high specific surface area and easy magnetic separation. The
as-prepared nanocomposite served as a heterogeneous catalyst for the Heck and Sonogashira coupling reactions
in various hydrophilic and hydrophobic deep eutectic solvents (DESs) as sustainable and environmentally benign
reaction media. Among the fifteen DESs evaluated for coupling reactions, the hydrophilic DES composed of
dimethyl ammonium chloride and glycerol exhibited the best results. Due to the low miscibility of catalyst and
DES in organic solvents, the separated aqueous phase containing both of the catalyst and DES can be readily
recovered by evaporating water and retrieved eight times with negligible loss of catalytic performance.
Pd catalyst
Cellulose
Magnetite-graphene oxide nanocomposite
Coupling reaction
Deep eutectic solvent
1
. Introduction
organic polymers in nature, has been widely utilized as catalyst support.
Cellulose is inexpensive, non-toxic, renewable, biodegradable, and
Palladium-catalyzed
C
–
C
cross-coupling transformations have
environmental friendly, all of which make it an excellent candidate for
being used as support in catalytic systems (Dong, Wu, Chen, & Wei,
2017; Kandathil, Kempasiddaiah, Sasidhar, & Patil, 2019). Moreover,
cellulose with its large surface area and free hydroxyl groups can act
both as ligand and reducing agent for the formation and stabilization of
metal nanoparticles and provides straightforward diffusion of the re-
agents to nanoparticles. It also helps in the well dispersion of metal
nanoparticles and prevents them from aggregation (Goswami & Das,
2018). Compared with other biopolymers, cellulose can easily be func-
tionalized with a multitude of functions owing to the presence of
abundant hydroxyl groups on its backbone and form either soluble or
insoluble catalyst supports via chemical modification (Wang, Hu, Xue, &
Wei, 2014). Different noble metal nanoparticles supported on cellulose
have been demonstrated to be effective catalysts for various reactions
(Jebali et al., 2018).
attracted considerable research attention as a mean toward industrially
beneficial chemicals (Biffis, Centomo, Zotto, & Zecca, 2018; Zhang,
Mao, Wang, Phan, & Zhang, 2020; Zhu & Lindsay, 2019). The most
–
explored examples of C C coupling processes catalyzed by Pd com-
pounds are Heck and Sonogashira, which involve coupling of aryl or
alkyl halides with terminal alkenes and alkynes, respectively (Cao et al.,
2
020; Li, Feng, & Li, 2019; Sardarian, Eslahi, & Esmaeilpour, 2019). The
resulting products of both reactions are of substantial importance as
major building blocks and key intermediates in material science, natural
products, pharmaceuticals, and conducting polymers (Cheng et al.,
2
020; Zheng, Zhao, Xu, & Zeng, 2020). During the last decades, het-
erogeneously Pd-catalyzed C C coupling reactions have received much
–
interest owing to their several advantages over homogeneous catalytic
systems, such as easy work up procedures and facile catalyst recycling
(
Nuri et al., 2020; Tashrifi et al., 2019).
One of the challenges of using cellulose as support is that its stable
dispersion hinders facile separation for recycling purposes. Conjugation
of cellulose with solid supports which can facilitate its separation and
recycling, provides a very promising solution to this challenge (Saba-
qian, Nemati, Heravi, & Nahzomi, 2017). To date, various covalent and
Nowadays, biopolymers such as chitosan, cellulose, and cyclodex-
trins are being utilized as supports for manufacturing heterogeneous Pd
catalysts (Tukhani, Panahi, & Khalafi-Nezhad, 2018; Wang et al., 2019).
Among the various biopolymers, cellulose, one of the most abundant
*
Corresponding author at: Faculty of Chemistry, Kharazmi University, Tehran, Iran.
E-mail address: mfarahani@khu.ac.ir (M. Masteri-Farahani).
https://doi.org/10.1016/j.carbpol.2020.117109
Received 29 June 2020; Received in revised form 11 September 2020; Accepted 12 September 2020
Available online 20 September 2020
0
144-8617/© 2020 Elsevier Ltd. All rights reserved.

M. Niakan et al.
Carbohydrate Polymers 251 (2021) 117109
3 4
Scheme 1. Schematic preparation method of GO-Fe O -Cellulose-Pd.
non-covalent strategies have been successfully developed for conjuga-
tion of cellulose with solid supports (Freudenberg et al., 2005; Kabiri &
Namazi, 2014; Sabaqian et al., 2017; Wang et al., 2018; Yin, Chen,
Zhang, Zhang, & Zhang, 2019). Among them, the copper-catalyzed
azide-alkyne cycloaddition (CuAAC) may be preferable due to its sim-
ple and mild reaction procedure, high efficiency and selectivity, and lack
of side reactions (Sharma, Rathod, Singh, Kumar, & Sasson, 2018;
Zhang, Li, Li, Wang, & Wang, 2019).
promising alternatives to volatile organic solvents for utilization in
organic transformations. Despite these interesting properties of DESs,
there are only a few reports on the utilization of DESs as media in the
Heck and Sonogashira coupling reactions (Grabner, Schweiger, Gavric,
Kourist, & Gruber-Woelfler, 2020; Ilgen & Konig, 2009; Marset et al.,
2017, 2019; Messa et al., 2020; Saavedra et al., 2019).
Conjugation of high surface area graphene oxide (GO) with magnetic
3 4
nanoparticles, specifically Fe O nanoparticles, produces the useful
In addition to recyclability of catalyst, the solvents have a key effect
on the environmental impact of organic transformations. Thus, many
attempts have been directed toward the replacement of hazardous vol-
atile organic solvents by greener media. In this regard, deep eutectic
solvents (DESs) as a new family of green reaction media have become
the focus of several researches due to their outstanding physicochemical
magnetic graphene oxide nanocomposite with facile separation effi-
ciency which is a promising candidate for use as catalyst support
combining the advantages of both GO and magnetic nanoparticles
(Sharma, Sharma, Sharma, Paul, & Clark, 2019; Xing et al., 2020).
Accordingly, we decided to employ cellulose-modified magnet-
ite-graphene oxide nanocomposite for immobilization of Pd nano-
particles for designing a heterogeneous Pd catalyst. As far as we know,
modification of magnetite-graphene oxide nanocomposite using cellu-
lose containing abundant OH groups, which have strong ability to sta-
bilize metal nanoparticles, has never been applied for stabilization of Pd
nanoparticles. The catalytic performance of the prepared catalyst in the
Heck and Sonogashira coupling reactions in different DESs as green and
´
properties (Marset et al., 2017; Quir o´ s-Montes, Carriedo, García-Al-
varez, & Soto, 2019). DESs possess favorable characteristics such as
non-toxicity, facile synthesis methods, biodegradability, easy recycla-
bility, low vapor pressure, and low melting point, which fully corre-
spond with green chemistry principles (Liu et al., 2020; Saavedra,
Gonz a´ lez-Gallardo, Meli, & Ram o´ n, 2019). Consequently, they are
2

M. Niakan et al.
Carbohydrate Polymers 251 (2021) 117109
recyclable reaction media is reported.
Table 1
The effect of various reaction conditions on the Heck reaction in the presence of
a
GO-Fe
3
O
4
-Cellulose-Pd.
2
. Experimental
Entry
Catalyst
(mol%)
DES (molar
ratio)
Base
T
Time
(h)
Yield
◦
b
2
.1. Catalyst preparation
( C)
(%)
1
1
ChCl:Urea
(1:2)
K
K
K
2
2
2
CO
CO
CO
3
3
3
100
5
73
45
78
91
86
58
85
81
43
89
98
26
37
28
41
98
98
92
0
3 4
The preparation method of GO-Fe O -Cellulose-Pd was illustrated in
2
1
ChCl:CA
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
80
5
Scheme 1. Briefly, GO was modified with magnetite nanoparticles to
obtain GO-Fe . Then, the hydroxyl groups on the surface of GO-Fe
were reacted with 3-CPTES, followed by the substitution reaction of
chloro groups with azide ions to achieve GO-Fe -N . Subsequently,
the click reaction of azide groups in GO-Fe -N with pre-synthesized
alkyne-functionalized cellulose afforded GO-Fe -Cellulose. Finally,
GO-Fe -Cellulose-Pd heterogeneous catalyst was synthesized by
treatment of GO-Fe -Cellulose with palladium acetate in absolute
(
1:1)
ChCl:MA
1:1)
3
O
4
3 4
O
3
1
5
(
3
O
4
3
4
1
ChCl:Gly
(1:2)
K2CO3
5
3
O
4
3
5
1
ChCl:EG
K
K
K
K
K
K
K
K
K
K
2
CO
2
CO
2
CO
2
CO
2
CO
2
CO
2
CO
2
CO
2
CO
2
CO
3
3
3
3
3
3
3
3
3
3
5
3 4
O
(
1:2)
ChCl:OX
1:1)
ChCl:BA
1:1.5)
DMAC:Urea
1:2)
DMAC:CA
1:2)
DMAC:MA
1:2)
DMAC:Gly
1:2)
3 4
O
6
1
5
3 4
O
(
ethanol. According to the inductively coupled plasma optical emission
spectroscopy (ICP-OES) analysis, the total loading of Pd in the prepared
7
1
5
(
ꢀ 1
8
1
5
catalyst was found to be 0.41 mmol.g . Full details about the prepa-
ration method of GO-Fe -Cellulose-Pd are provided below.
(
3 4
O
9
1
5
(
2
.1.1. Preparation of magnetite-graphene oxide nanocomposite (GO-
10
1
5
(
Fe
3 4
O )
1
1
1
1
1
2
3
4
1
5
GO was synthesized according to modified Hummers procedure as
described elsewhere (Marcano et al., 2010). Magnetite-graphene oxide
nanocomposite (GO-Fe ) was obtained according to literature pro-
(
1
TBAB:OA
(1:2)
5
3 4
O
1
TBAB:DA
5
cedure (See supporting information) (Amiri, Shabani, Dadfarnia, &
(
1:2)
TOMAC:OA
1:2)
Sadjadi, 2019).
1
5
(
2
.1.2. Preparation of azide-functionalized GO-Fe
3
O
4
(GO-Fe
3
O
4
-N
3
)
15
1
TOMAC:DA
(1:2)
K2CO3
CO
CO
5
GO-Fe (1 g) was suspended in 40 mL of dry toluene under soni-
3 4
O
1
6
1.25
0.75
0.5
none
0.75
0.75
0.75
0.75
0.75
0.75
0.75
DMAC:Gly
K
2
3
5
cation for 30 min. After addition of 3-chloropropyltriethoxysilane (3-
CPTES, 3 mL), the mixture was refluxed for 24 h under nitrogen atmo-
(
1:2)
DMAC:Gly
1:2)
1
7
K
2
3
5
6.5
24
5
3 4
sphere. The obtained solid (GO-Fe O -Cl) was magnetically collected,
(
washed with ethanol to remove the unreacted silylating agent, and dried
18
DMAC:Gly
(1:2)
K
K
K
K
2
CO
2
CO
2
CO
2
CO
3
3
3
3
◦
at 80 C under vacuum. The GO-Fe
3
O
4
-Cl (1 g) was sonicated in dime-
1
2
9
0
DMAC:Gly
thylformamide (DMF, 50 mL) for 30 min and after addition of NaN
3
(
1:2)
◦
(
2 mmol, 0.13 g), the suspension was stirred at 80 C for 10 h. Final
DMAC:Gly
(1:2)
61
98
34
23
74
57
82
product was isolated with a permanent magnet, washed with DMF
◦
several times, and dried at 80 C under vacuum to afford GO-Fe
3
O
4
-N
3
.
21
DMAC:Gly
120
100
100
100
100
100
5
(
1:2)
DMAC:Gly
1:2)
2
2
3
Et
NaOH
Na CO
3
N
8
2
.1.3. Preparation of clicked cellulose-modified GO-Fe
3 4 3 4
O (GO-Fe O -
(
Cellulose)
2
DMAC:Gly
(1:2)
10
7
Alkyne-functionalized cellulose was prepared according to the
earlier report (Mangiante et al., 2013) and characterized by FT-IR
24
DMAC:Gly
2
3
(
1:2)
DMAC:Gly
1:2)
3 4 3
spectroscopy (Figure S1). On the other hand, GO-Fe O -N (1 g) was
2
5
KOH
6
uniformly dispersed in 60 mL of dry DMF under ultrasonic condition.
After that, alkyne-functionalized cellulose (2 g), copper (II) sulfate
(
26
DMAC:Gly
(1:2)
K3PO4
5
(
0.1 g), and sodium ascorbate (2 g) were added to the above mixture and
◦
stirred at 50 C for 24 h. The mixture was cooled down to room tem-
perature and the product was isolated by magnetic separation, washed
a
Reaction conditions: iodobenzene (1 mmol), n-butyl acrylate (1.2 mmol),
base (2 mmol), and DES (3 mL).
◦
b
with DMF and water repeatedly, and dried at 80 C under vacuum.
Isolated yields.
2
.1.4. Immobilization of Pd nanoparticles on GO-Fe
3 4
O -Cellulose
tetrabutylammonium bromide (TBAB), or trioctylmethylammonium
chloride (TOMAC) as hydrogen bond acceptor and urea, citric acid (CA),
malonic acid (MA), glycerol (Gly), ethylene glycol (EG), oxalic acid
GO-Fe -Cellulose (1 g) was ultrasonically dispersed in absolute
3 4
O
ethanol (50 mL). After addition of palladium acetate (0.5 mmol, 0.11 g),
the mixture was stirred for 24 h at room temperature. The resultant
(
OX), boric acid (BA), octanoic acid (OA), or decanoic acid (DA) as
3 4
black solid (GO-Fe O -Cellulose-Pd) was collected with utilizing a
hydrogen bond donor with the molar ratio given in Table 1. The mix-
tures were stirred vigorously in an oil bath in a temperature range be-
magnet, washed thoroughly with large volume of hot ethanol until
◦
washing were colorless, and dried at 80 C under vacuum.
◦
tween 70 and 90 C for 2ꢀ 3 h until clear and homogeneous liquids were
obtained.
2
.2. Preparation of DESs
DESs were synthesized according to previous works (Jiang et al.,
019; Mako ´s , Słupek, & Gębicki, 2020; Shekaari, Ahadzadeh, & Karimi,
019; Zhang, Vigier, Royer, & J ´e r oˆ me, 2012). They were prepared by
2.3. Typical method for the Heck coupling reaction
2
2
To a mixture of aryl halide (1 mmol), alkene (1.2 mmol), and K
2 3
CO
mixing choline chloride (ChCl), dimethyl ammonium chloride (DMAC),
(2 mmol) in DES (DMAC:Gly, 3 mL), 0.018 g of GO-Fe -Cellulose-Pd
3 4
O
3

M. Niakan et al.
Carbohydrate Polymers 251 (2021) 117109
3 4 3 4 3 3 4 3 4 3 4 3 4
Fig. 1. (a) FT-IR spectra of GO, GO-Fe O , GO-Fe O -N , GO-Fe O -Cellulose, and GO-Fe O -Cellulose-Pd, (b) XRD patterns of GO, GO-Fe O , and GO-Fe O -Cel-
lulose-Pd, (c) XPS survey spectrum of GO-Fe
3
O
4
-Cellulose-Pd, and (d) high-resolution XPS spectrum of Pd 3d.
◦
ꢀ 1
(
0.75 mol%) was added. The mixture was stirred at 100 C and the
Shemirani, 2016). For GO-Fe
appeared due to the stretching vibration of azide (-N
revealed their attachment on the surface of GO-Fe
bands corresponding to the C–H stretching vibrations of the propyl chain
3
O
4
-N
3
, a sharp peak at 2175 cm was
) groups, which
. Moreover, the
progress of reaction was checked by thin layer chromatography (TLC).
The mixture was quenched with water (15 mL) after completing the
reaction, and extracted with ethyl acetate (3 × 10 mL). The organic
3
3 4
O
ꢀ 1
extract was dried over Na
SO
2 4
and concentrated under vacuum. Puri-
in silylating agent were observed at about 2800ꢀ 3000 cm (Sharma
et al., 2018). After click reaction of GO-Fe -N with
alkyne-functionalized cellulose, the characteristic peak of azide group at
fication of the obtained crude product was performed by column chro-
matography on silica gel. The aqueous phase, which contained both of
the catalyst and DES, was used for another run after evaporation of
water.
3
O
4
3
ꢀ
1
2000ꢀ 2200 cm
groups to triazole rings and the successful attachment of cellulose to
GO-Fe (Sharma et al., 2018). Furthermore, the intensity of O
stretching vibrations at 3420 cm increased dramatically owing to the
existence of abundant O H groups on the surface of supported cellu-
lose. The spectrum of GO-Fe -Cellulose-Pd showed almost no change
after loading of Pd nanoparticles on the surface of GO-Fe -Cellulose.
was vanished indicating the conversion of azide
3
O
4
–
H
ꢀ 1
2
.4. Typical method for the Sonogashira coupling reaction
–
3 4
O
A mixture of phenylacetylene (1.2 mmol), aryl halide (1 mmol),
3 4
O
K
2
CO
3
(2 mmol), and GO-Fe
3
O
4
-Cellulose-Pd (1 mol%, 0.024 g) in 3 mL
The phase composition of the samples were explored by X-ray
diffraction (XRD) analysis (Fig. 1b). The XRD pattern of GO revealed an
◦
of DES (DMAC:Gly) was left under stirring at 120 C. After completing
the reaction (monitored by TLC), the mixture was quenched with water
◦
intense peak at 2θ = 11.3 , corresponding to (001) plane (Master-
(
10 mL) and extracted with ethyl acetate (3 × 10 mL). The work-up
3 4
i-Farahani et al., 2020). For GO-Fe O , the observed diffraction peaks
procedure was performed similar to the Heck coupling reaction.
can be attributed to crystal planes of Fe
structure (JCPDS Card no. 19-0629). Meanwhile, the (001) reflection
peak of GO was not appeared in GO-Fe due to the incorporation of
magnetite nanoparticles between the nanosheets of GO (Moztahida
et al., 2019). The characteristic diffraction peaks of Fe crystal
structure were detected in the XRD pattern of GO-Fe -Cellulose-Pd,
implying that the structure of GO-Fe was not destroyed during the
catalyst preparation. Moreover, the XRD pattern of catalyst also
3 4
O with face centered cubic
3
. Results and discussion
3 4
O
3
.1. Characterization of GO-Fe O -Cellulose-Pd
3 4
3 4
O
3 4
O
In order to approve the successful modification in each step, the FT-
IR spectra of the resulted samples were obtained and depicted in Fig. 1a.
3 4
O
ꢀ
1
In the spectrum of primary GO, the peaks at 1000ꢀ 1300 cm were
assigned to the C OH vibrations of phenolic groups and C C vi-
brations of epoxy groups. Also, the peaks located at 1607 and 1715 cm
◦
◦
◦
demonstrated three new weak peaks at 40 , 46 , and 67 which can be
indexed to (111), (200), and (220) crystal planes of Pd (0), respectively
–
O
– –
-
1
(
Tukhani et al., 2018). The weakness of the peaks is due to small size of
Pd nanoparticles and their well-dispersion on the surface of
GO-Fe -Cellulose.
–
–
were due to the C
C stretching vibrations of aromatic skeletal network
O stretching vibrations, respectively (Masteri-Farahani,
Hosseini, & Forouzeshfar, 2020). After introducing magnetite nano-
–
–
and the C
3 4
O
X-ray photoelectron spectroscopy (XPS) was utilized to clarify the
surface chemical composition of the catalyst. Fig. 1c depicts the XPS
ꢀ 1
particles, two peaks emerged at 510 and 630 cm corresponding to the
Fe-O stretching vibrations in Fe nanoparticles (Aliyari, Alvand, &
3 4
O
4

M. Niakan et al.
Carbohydrate Polymers 251 (2021) 117109
3 4
Fig. 2. SEM image, EDX spectrum, and elemental mapping images of GO-Fe O -Cellulose-Pd.
survey spectrum of GO-Fe
3
O
4
-Cellulose-Pd demonstrating the signals of
3 4
observed in the SEM image of GO-Fe O -Cellulose-Pd (Fig. 3c), the
C 1s, N 1s, O 1s, Si 2s, Si 2p, Fe 2p, and Pd 3d, confirming the overall
chemical composition of the catalyst. In the high-resolution XPS spec-
trum of Pd (Fig. 1d), the Pd 3d5/2 and Pd 3d3/2 peaks were clearly
observed at 335.67 and 341.18 eV, respectively, consistent with the
morphology of the catalyst was the same as GO-Fe O .
3 4
The TEM image of GO in Fig. 3d shows a layered and sheet-like
structure characteristic of GO structure. After incorporation of magne-
tite, well-dispersed spherical Fe
about 10 nm can be seen on the surface of GO nanosheets without any
aggregation (Fig. 3e). From the TEM image of GO-Fe -Cellulose-Pd
(Fig. 3f), it can be found that the preparation process of the catalyst had
no influence on the microstructure of GO-Fe nanocomposite and
Fe nanoparticles remained well-dispersed on the GO surface.
The magnetic behavior of GO-Fe and GO-Fe -Cellulose-Pd
3 4
O nanoparticles with diameters of
◦
existence of Pd in the oxidation state of zero i.e. Pd (Stadler et al.,
2
+
2
019). Meanwhile, no peaks assignable to the Pd oxidation state were
3 4
O
2
+
detected, implying that all of the Pd ions in the catalyst structure were
◦
completely reduced to Pd . The results further inferred that cellulose
3 4
O
component acted as reducing agent as well as stabilizer for Pd nano-
particles and prevented from their oxidation.
3 4
O
3
O
4
3 4
O
The chemical composition of prepared catalyst was further examined
by energy dispersive X-ray (EDX) spectroscopy. As shown in Fig. 2,
significant peaks corresponding to C, N, O, Si, Fe, and Pd elements can
were explored with vibrating sample magnetometry (VSM) and the
magnetization curves were presented in Fig. 4a. Both samples exhibited
almost zero coercivity and remanence in their magnetization curves,
demonstrating their superparamagnetic features. The saturation
be seen in the EDX spectrum of GO-Fe
elemental mapping images of GO-Fe
the elements were uniformly distributed on the surface of catalyst.
The microstructure and morphology of GO, GO-Fe , and GO-
-Cellulose-Pd were monitored by scanning electron microscopy
SEM) and transition electron microscopy (TEM) techniques. Fig. 3a
demonstrates the SEM image of GO with the lamellar morphology. In
comparison with the bare GO, GO-Fe (Fig. 3b) revealed the existence
of Fe nanoparticles on the surface of GO nanosheets. Also, as
3
O
4
-Cellulose-Pd. Moreover, EDX
3
O
4
-Cellulose-Pd revealed that all of
magnetization value of GO-Fe
3
O
4
-Cellulose-Pd was decreased to
ꢀ
1
ꢀ 1
19.8 emu g
compared with GO-Fe
3
O
4
(37.1 emu g ) due to the
3
O
4
3 4
presence of cellulose and Pd nanoparticles within the GO-Fe O nano-
Fe
3
O
4
composite. Despite the reduction in saturation magnetization, the
catalyst was easily isolated magnetically by setting an external magnet
near the wall of the vial as shown in the inset of Fig. 4a.
(
3
O
4
To examine the thermal stability of the synthesized catalyst, ther-
mogravimetric analysis (TGA) was carried out. The TGA curve of GO-
3 4
O
5

M. Niakan et al.
Carbohydrate Polymers 251 (2021) 117109
3 4 3 4 3 4 3 4
Fig. 3. SEM images of (a) GO, (b) GO-Fe O , and (c) GO-Fe O -Cellulose-Pd, and TEM images of (d) GO, (e) GO-Fe O , and (f) GO-Fe O -Cellulose-Pd.
Fig. 4. (a) Magnetization curves of GO-Fe
O
3 4
and GO-Fe
3
O
4
-Cellulose-Pd, and (b) TGA curve of GO-Fe
3
O
4
-Cellulose-Pd.
Fe
3
O
4
-Cellulose-Pd in Fig. 4b exhibited two weight losses. The first
various hydrophilic DESs investigated, DMAC:Gly was the most effective
solvent for this reaction. Therefore, DMAC:Gly was identified as the
solvent of choice for further investigations.
◦
negligible weight loss (2%) occurred below 150 C owing to desorption
◦
of moisture and volatile species. The next weight loss after 150 C was
attributed to the decomposition of organic parts and cellulose in the
catalyst structure.
Next, the catalyst amount was varied from 0.5 mol% to 1.25 mol%
(Table 1, entries 16–18). It was found that employing 0.75 mol% of
catalyst was appropriate for this reaction. On the other hand, to clarify
the effect of catalyst, a blank reaction was conducted without catalyst, in
which no product was obtained even after 24 h (Table 1, entry 19). The
temperature effect on the reaction was also explored and it was found
3
3 4
.2. Catalytic activity of GO-Fe O -Cellulose-Pd
After characterizing the catalyst structure, its catalytic performance
◦
that with decreasing the temperature to 80 C, a significant decrease in
was firstly evaluated in the Heck coupling reaction. The coupling of n-
butyl acrylate with iodobenzene was chosen as model reaction to
determine the optimum reaction conditions. The effect of reaction pa-
rameters was investigated in this reaction and the details were provided
in Table 1. As seen in Table 1, the use of hydrophilic DESs resulted in
higher product yields (Table 1, entries 1–11) compared to hydrophobic
DESs (Table 1, entries 12–15). The plausible reason might be the hy-
drophilic nature of the catalyst that provides more dispersion in hy-
drophilic DESs and thus enhances its catalytic activity. Among the
the product yield was observed (Table 1, entry 20). However, the in-
◦
crease of reaction temperature to 120 C did not show any substantial
increment in the product formation (Table 1, entry 21). Finally, different
bases were screened (Table 1, entries 22–26), among which K
2 3
CO was
found to be most suitable. According to the data acquired, entry 17 in
Table 1 was chosen as the optimized reaction conditions for the Heck
reaction.
To demonstrate the scope and generality of the methodology, the
6

M. Niakan et al.
Carbohydrate Polymers 251 (2021) 117109
Scheme 2. Heck reaction of various aryl halides and alkenes in the presence of GO-Fe
3
O
4
-Cellulose-Pd. Reaction conditions: aryl halide (1 mmol), alkene
(
2 3
1.2 mmol), K CO (2 mmol), and DMAC:Gly (3 mL). Yields were isolated.
Heck coupling reaction of different aryl halides and alkenes was
explored under the optimized reaction conditions (Scheme 2). Different
alkyl acrylates as well as styrene were reacted with iodo-, bromo-, and
chlorobenzene and desired coupling products were formed with excel-
lent yields. Moreover, the reaction of n-butyl acrylate and styrene with a
wide range of aryl halides achieved remarkable yields irrespective of the
existence of any electron-donating or electron-withdrawing substituents
in the aryl halides. As expected, aryl iodides reacted at a faster rate than
aryl bromides and chlorides. Overallw, styrene exhibited higher reac-
tivity than n-butyl acrylate towards the Heck reaction under the opti-
iodobenzene and phenylacetylene as model coupling reaction under
diverse conditions and the results were summarized in Table S2. Among
the different experimental conditions investigated, the optimum reac-
tion conditions for the Sonogashira reaction were 1 mol% of catalyst,
◦
K
2
CO
3
as base, and DMAC:Gly as solvent at 120 C (Table S2, entry 20).
After optimizing the reaction conditions, the scope of methodology
was explored with diverse aryl halides (Scheme 3). As can be seen in
Scheme 3, aryl iodides, bromides, and chlorides with both electron-
donating and electron-withdrawing substituents were coupled with
phenylacetylene to form the desired products with high yields. It is
noteworthy that no product associated with the homo-coupling reaction
of phenylacetylene was detected in all of the examined reactions. The
3 4
mized conditions. It can be concluded that GO-Fe O -Cellulose-Pd has
excellent catalytic activity in the Heck coupling reaction.
The impressive results of the Heck reaction encouraged us to
examine the catalytic activity of the prepared catalyst in the Sonogashira
reaction. The optimized reaction conditions were determined using
results indicated the high efficiency of GO-Fe
lyzing the Sonogashira coupling reaction.
3 4
O -Cellulose-Pd in cata-
In order to show the superiority of the present work, the catalytic
7

M. Niakan et al.
Carbohydrate Polymers 251 (2021) 117109
Scheme 3. Sonogashira reaction of various aryl halides and phenylacetylene in the presence of GO-Fe
3
O
4
-Cellulose-Pd. Reaction conditions: aryl halide (1 mmol),
2 3
phenylacetylene (1.2 mmol), K CO (2 mmol), and DMAC:Gly (3 mL). Yields were isolated.
Table 2
3 4
Comparison of the catalytic activity of GO-Fe O -Cellulose-Pd with other reported Pd-catalysts in the Heck and Sonogashira reactions.
Entry
1
Catalyst (mol%)
Reaction
Reaction conditions
Time
h)
Yield
(%)
Ref
(
◦
Fe
3
O
4
/GO-Cellulose-Pd
Heck
DMAC:Gly, K
2
CO
3
, 100
C
3.5
95
(This work)
(
0.75)
◦
2
3
4
5
6
7
8
9
PTFE-PdNPs (1.0)
Pd-MPMO (1.9)
Heck
Heck
Heck
Heck
Heck
Heck
Heck
H
2
O, KOH, 90
DMF, Et
DMSO, K
DMA, Et
DMF, K
DMF, NaOAc, 110
C
15
4
91
58
90
95
86
100
95
91
(Ohtaka et al., 2018)
◦
3
N, 100
C
(Elavarasan, Kala, Muhammad, Bhaumik, & Sasidharan, 2019)
(Lakshminarayana et al., 2018)
(Du et al., 2020)
◦
Pd/CuFe
2
O
4
(4.0)
2
CO
3
, 120
C
12
5
◦
Pd@CS/PAAS (5.0)
PdNPs/Wood (2.6)
3
N, 110
CO
C
◦
◦
◦
2
3
, 100
C
6
(Chao et al., 2019)
KjPdC (1.0)
C
24
15
8
(Santos et al., 2014)
Me
Pd(N,O-L
Fe
1.0)
)
2
(0.3)
DMF, K
2
CO
3
, 100
C
(Ardizzoia, Ghiotti, Therrien, & Brenna, 2018)
(This work)
◦
3
O
4
/GO-Cellulose-Pd
Sonogashira
Sonogashira
Sonogashira
DMAC:Gly, K
2
CO , 120 C
3
(
i
1
0
1
Bipyridine-Palladium (3.0)
PdNPs/DNA (0.5)
Ph
3
◦
PMeBr:Gly, Pr
2
NH,
16
24
84
85
(Saavedra et al., 2019)
6
0 C
◦
1
MeOH, Cs
2
CO
3
, 65
C
(Camacho, Martín-Garcí, Contreras-Celed o´ n, Chac o´ n-García, &
Alonso, 2017)
◦
12
13
14
15
MNP-PdNPs (1.5)
Sonogashira
Sonogashira
Sonogashira
Sonogashira
THF, Et
EtOH, K
EtOH/ H
i-PrOH, K
3
N, 65
CO , 65
O, K CO
CO , RT
C
24
16
1.5
7
85
97
90
98
(Wang et al., 2015)
◦
MMT@Pd/Cu (1.0)
Pd@HNTs-T-CD (6.0)
palladium salen complex
2
3
C
(Xu et al., 2014)
◦
2
2
3
, 60
C
(Sadjadi, 2018)
2
3
(Gogoi, Dewan, Borah, & Bora, 2015)
(
2.0)
NHC-palladium complex
1.0)
◦
1
6
Sonogashira
DMSO, K
2
CO
3
, 100
C
1
61
(Yang et al., 2012)
(
activity of GO-Fe
3
O
4
-Cellulose-Pd was compared with earlier reported
systems.
Pd-based catalysts in the Heck reaction of iodobenzene and styrene and
Sonogashira reaction of iodobenzene and phenylacetylene. From
Table 2, it is visible that the current catalyst reveals a comparable cat-
alytic efficiency in coupling reactions. More importantly, the use of
natural cellulose as both reducing and stabilizing agents for Pd, the
utilization of DES as solvent, and the recovery of the catalyst and DES in
fast and easy manner make this system greener than most of the listed
3.3. Recyclability and stability of GO-Fe
3
O
4
-Cellulose-Pd and DES
The recycling experiments of GO-Fe
3 4
O -Cellulose-Pd and DES were
performed in the mentioned Heck and Sonogashira model coupling re-
actions under the optimized reaction conditions. The hydrophilic char-
acter of the catalyst and DES provided an easy strategy for their
8

M. Niakan et al.
Carbohydrate Polymers 251 (2021) 117109
CRediT authorship contribution statement
Mahsa Niakan: Investigation, Data curation, Writing - original draft.
Majid Masteri-Farahani: Project administration, Supervision, Writing -
review & editing. Hemayat Shekaari: Investigation, Data curation.
Sabah Karimi: Investigation, Writing - original draft.
Acknowledgements
The authors gratefully acknowledge financial support (Grant Num-
ber H/4/361) from Kharazmi University.
Appendix A. Supplementary data
Supplementary material related to this article can be found, in the
online version, at doi:https://doi.org/10.1016/j.carbpol.2020.117109.
Fig. 5. Recyclability of the catalyst and DES for the Heck (red diagram) and
Sonogashira (green diagram) model reactions under the optimized reaction
conditions. (For interpretation of the references to colour in this figure legend,
the reader is referred to the web version of this article).
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