DFNS/PEI/Cu Nanocatalyst for Reduction of Nitro-aromatic Compounds

Article abstract of DOI:10.1007/s10562-020-03422-6

Abstract: Nitro-aromatic pollution in industrial waste streams threat wellbeing of water resources. This study investigates the performance of a copper-based nano catalyst to reduce nitro-aromatic compounds in aqueous solution. Anchoring Cu NPs within the nano spaces of a fibrous silicate with high surface area, and simple accessibility of active sites were successfully established by a facile approach to produce a novel nanocatalyst (DFNS/PEI/Cu). DFNS displayed different properties such as dandelion-like shape, high surface area, and simple availability of active sites. Immobilization of the Cu NPs on DFNS nanospheres not only prevented their aggregation, but also considerably improved the availability of the catalytic active sites. The DFNS/PEI/Cu nanocatalyst demonstrated great catalytic activities for the reduction of nitro compounds under green conditions. Our findings show fibrous DFNS and Cu NPs as a helpful platform for the fabrication of noble metal-based affordable nanocatalyst for many catalytic applications. Graphic Abstract: DFNS/PEI/Cu nanocatalyst as a new adsorbents for the reduction of nitro compounds[Figure not available: see fulltext.]

Full text of DOI:10.1007/s10562-020-03422-6

Catalysis Letters
https://doi.org/10.1007/s10562-020-03422-6
DFNS/PEI/Cu Nanocatalyst for Reduction of Nitro‑aromatic
Compounds
Marjan Moradi1 · Nahid Rastakhiz1 · Mehrorang Ghaedi2 · Rahele Zhiani3
Received: 4 July 2020 / Accepted: 5 October 2020
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
Nitro-aromatic pollution in industrial waste streams threat wellbeing of water resources. This study investigates the per-
formance of a copper-based nano catalyst to reduce nitro-aromatic compounds in aqueous solution. Anchoring Cu NPs
within the nano spaces of a fbrous silicate with high surface area, and simple accessibility of active sites were successfully
established by a facile approach to produce a novel nanocatalyst (DFNS/PEI/Cu). DFNS displayed diferent properties such
as dandelion-like shape, high surface area, and simple availability of active sites. Immobilization of the Cu NPs on DFNS
nanospheres not only prevented their aggregation, but also considerably improved the availability of the catalytic active
sites. The DFNS/PEI/Cu nanocatalyst demonstrated great catalytic activities for the reduction of nitro compounds under
green conditions. Our fndings show fbrous DFNS and Cu NPs as a helpful platform for the fabrication of noble metal-based
afordable nanocatalyst for many catalytic applications.
Graphic Abstract
DFNS/PEI/Cu nanocatalyst as a new adsorbents for the reduction of nitro compounds
NO2
NH2
NH2
NH2
OOO
Si
OOO
Si
OOO OOO
Si
Si
O
O
O
O
HO
HN
OH
OH
NH
OH
NH
NH
N
N
NH2
HN
HN
N
Cu
N
Cu
N
NH2
N
N
Cu NH2
N
NH
Cu
NH
HN
H2
N
N
HN
NH2
HN
HN
OH
OH
O
O
Si
Si
O
O
O
OOO
DFNS
Keywords Nanocatalyst · DFNS/PEI/Cu · Nitro-aromatic compounds · Water pollution
* Nahid Rastakhiz
1 Introduction
nahid.rastakhiz@yahoo.com
Marjan Moradi
Catalysts play chief roles in the hydrogenation of nitroaro-
matics to aminoaromatics [1–3]. The development of highly
active catalysts has attracted notable consideration for the
next-generation of green, afordable and efcient reduction
operations. In specifc, the engineered metal nanoparticles
(NPs) and nanocomposites have substantially elevated the
efciency of catalytic systems. In consequence, diferent
marjanmoradi86@yahoo.com
1
2
3
Department of Chemistry, Kerman Branch, Islamic Azad
University, Kerman, Iran
Chemistry Department, Yasouj University,
75918-74831 Yasouj, Iran
Department of Chemistry, Nyshabur Branch, Islamic Azad
University, Nyshabur, Iran
Vol.:(0123456789)
1 3

M. Moradi et al.
procedures have been used to manufacture the low cost
nanostructured catalysts [4–6]. A precis of nanocatalysts
applied for the eco-friendly reduction of nitroaromatics has
also been investigated by Zhang and colleagues, emphasiz-
ing the benefts of the presented heterogeneous catalysts [7].
However, a few disadvantages of the present catalysts need
to be circumvented namely increasing the specifc surface
area, long-term stability, production cost diminution, and
ecological concerns relating to their industrial applications
[8]. To manufacture such catalysts with desired capabili-
ties, varied nanostructured catalysts have been designed
and synthesized [9, 10]; metal NPs have been stabilized on
variable robust nanostructures to fabricate active nanocom-
posite catalysts for reduction of nitroaromatics [11]. These
heterogeneous catalysts usually contain valuable metal
nanocatalysts e.g. Pd, Pt, Rh, Ru etc. to accomplish efec-
tive hydrogenation of nitroaromatics. However, they are not
widely adopted in the chemical industries because of their
signifcant expenses which are important problem from the
economical sight [12–17]. In comparison, elements such as
Cu, Co, Fe, Mn, and Ni which are abundant in the earth are
inexpensive and may be used as suitable catalysts for sev-
eral catalytic transformations, but with low catalytic activ-
ity [18–20]. The Cu NPs provide interesting electronic con-
fguration, structural diversity, coordination geometry, and
catalysis activity. Moreover, Cu NP surface can be readily
modifed with various bridging ligands to create multinu-
clear homo- and hetero-metallic structures with improved
physicochemical, magnetic, catalytic, and optical activities
[21–25].
perform hydrogenation of nitroarenes under more favora-
ble conditions [36–38]. The catalytic activity of metal NPs
are mainly because of their high surface to volume ration
that accentuates the efect of surface chemistry [39]. Hence,
smaller metal NPs demonstrated higher catalytic activity
[40, 41]. However, high surface energy of the small metal
NPs increases inter-particle accumulation, which will reduce
the catalytic performance [42]. An approach to address this
issue is to immobilize nanoparticles in a scafold. Many
supporting materials, like Al2O3 [43, 44], carbon [45, 46],
core–shell magnetic mesopores [47], and mesoporous silica
[48] are utilized to immobilize metal NPs because of their
outstanding features, high surface areas, and robust surface
chemistry as well as stability. An ideal scafold provides
large specifc surface areas causing high dispersion of the
NPs, thus, barricading the NPs accumulation and enhancing
the activity of the catalyst system. Among all, silica supports
are highly favorable due to high accessible surface areas, and
ease of synthesis in various morphologies. Dendritic silica
fbers structures (DFNS) ofer an enhanced external radial
surface and thermal stability that make them a superb candi-
date for metal NP immobilization. The production of DFNS
needs microemulsion system, which includes surfactant,
water, and oil. In addition, the particle size and morphol-
ogy of DFNS are tunable using co‐surfactants and diferent
co-solvents [49–55]. DFNS has been vastly used to stabilize
copper (Cu) nanoparticles.
In this study, we frst synthesized DFNS nanostructure,
then activated it with glycidyloxypropyl and functional-
ized by polyethyleneimine. We further used this scafold to
immobilize Cu nanoparticles (Scheme 1). The structure of
fnal construct was characterized using SEM/TEM imaging,
FTIR, XRD, and thermogravimetric analysis. We demon-
strated application of DFNS/PEI/Cu NPs in reducing sev-
eral nitroarenes to amines. Our fndings prove DFNS/PEI/
Cu NPs as a potential catalysis in removing amino-aromatics
pollutants.
Water pollution has become a serious global concern that
threatens the entire biosphere and infuences the lives of
many individuals around the globe. Diferent kinds of ill-
nesses are caused by this pollution and many people die
every year due to the diseases caused by polluted water.
Aromatic amines are one of the growing industrial pollut-
ants. The amine group is an essential mediator for manu-
facturing of various drugs, organic chemicals, rubber mate-
rials, photographic, polymers and dyes [26]. However, the
remaining amine-containing aromatic by products in these
processes poses environmental and health risks. As a result,
many strategies have been developed for reducing the nitro
substrates including metal/acid reduction [27–29], catalytic
hydrogenation [30], hydrogenation at homogeneous catalytic
transition [31], and hydrogenation at heterogeneous catalytic
transfer [32, 33]. Nonetheless, these processes have some
signifcant disadvantages; for instance, metal/acid system
has shown poor selectivity and it is ecologically hazard-
ous; besides, catalytic hydrogenation is not favored duo to
applying H2 gas at high temperature, and it is not feasible to
retrieve the homogeneous or heterogeneous catalysis after
the reaction [34, 35]. Several studies used the noble metal
nanoparticle (NMNPs)-based heterogeneous catalysts to
2 Experiment: Materials and Methods
2.1 Chemicals and Instruments
High-purity chemicals were obtained from Fluka and Merck.
Electrothermal 9100 device was used to determine uncor-
rected melting points in open capillaries. The VERTEC 70
spectrometer (broker) was utilized in the transmission mode
to determine the FTIR spectrum. Spectroscopic grade KBr
was used to pulverize and pelletize the samples. Transmis-
sion electron microscope (TEM) was set up at 100 kV to
determine size and structure of nanoparticles. Powder X-ray
difraction (Bruker D8 Advance model) with Cu Ka radia-
tion was used to identify crystallographic structures of nano
1 3

DFNS/PEI/Cu Nanocatalyst for Reduction of Nitro-aromatic Compounds
Scheme 1 Preparation of
DFNS/PEI/Cu nanocatalyst
O
O
Si
O
EtO
EtO Si
EtO
O
+
O
O
O
DFNS
OO
O
OO
O
OO
O
OO
O
OO
O
OO
O
OOO
Si
OO
O
Si
Si
Si
Si
Si
Si
Si
O
O
O
O
O
O
O
O
OH
NH
HO
OH
NH
OH
NH
OH
NH
HO
HN
OH
OH
NH
HN
NH
N
N
NH2
HN
N
N
N
NH2
HN
HN
N
N
Cu
Cu
N
NH2
NH2
N
N
CuSO4.5H2O
N
N
N
N
N
NH2
Cu
NH2
NH
NH
HN
Cu
NH
H2N
HN
N
H2N
N
N
N
HN
HN
NH
NH2
NH2
HN
HN
HN
HN
OH
OH
OH
OH
O
O
O
O
Si
Si
Si
OOO
Si
OOO
OOO
OOO
DFNS
DFNS
particles. Thermal gravimetry analysis (TGA) was used
under nitrogen atmosphere with a heating rate of 10 °C/min.
Elemental analyses for carbon, hydrogen and nitrogen was
performed on Heraeus CHN–O-Rapid analyzer. Thin later
chromatography (TLC) done on colloid SILG/UV 254 plates
was applied to determine the production purity and moni-
tor reaction. The mass spectra was recorded on Shimadzu
GCMS-QP5050 Mass Spectrometer.
2.3 Activation of DFNS with Glycidyloxypropyl
(GMSI)
200 mg of prepared DFNS was mixed into 20 ml of THF
and then 20 mmol of NaH was added while mixing with
ultra-sonication. Then, 22 mmol of (3-glycidyloxypropyl)
trimethoxysilane was added, followed by stirring at 50 °C
for 16 h. The mixture was purifed and eluted with ethanol
and deionized water. The obtained solid particles were then
dried in vacuum condition at 50 °C for 3 h [56].
2.2 Preparation of DFNS
30 ml of cyclohexane and 1.5 ml of pentanol were mixed
and then 2.5 g of tetraethyl orthosilicate was added to the
mixture. 0.6 g of urea and 1 g of cetylpyridinium bromide
were dissolved in 30 ml of water. The mixture was continu-
ously stirred at room temperature for 45 min, then put in a
Tefon-sealed hydrothermal reactor and heated at 120 °C for
5 h. The formed silica was isolated by centrifugation. Pellets
were washed with deionized water and acetone, and dried in
oven. This dried powder was calcined at 500 °C for 6 h in air.
2.4 Functionalization of GMSI Activated DFNS
with Polyethylene Imine
Approximately 100 mg of DFNS activated by glycidyloxy-
propyl was poured in 10 ml of acetate bufer (0.1 M and pH
4.5) that contains 50 mg of polyethylenimine (PEI). The
suspension was agitated under speed of 120 rpm for some
hours for achieving nanoparticles with PEI. The fnal nano-
particles were eluted several times, and stored at 4 °C [56].
1 3

M. Moradi et al.
2.5 Preparation of DFNS/PEI/Cu NPs
3 Results and Discussion
DFNS/PEI (50 mg), CuSO4·5H2O (0.01 M) and ascorbic
acid (0.11 M) were dissolved at 85 °C continued with stir-
ring for 30 min. The chemical reduction process occurs at
pH 6.5 adjusted with aqueous NaOH.
In this paper, DFNS was synthesized following the reported
methods. DNFS was then activated by (3-glycidyloxypro-
pyl)trimethoxysilane, and subsequently functionalized by
polyethylenimine. Copper nanoparticles were then immo-
bilized on PEI activated DFNS in presence of ascorbic acid
(Scheme 1).
2.6 General Procedure for Reducing Nitro
Compounds
The fbers of DFNS contains Si–OH bonds that readily
reacts with PEI to construct DFNS/PEI. The PEI groups then
act as loading docks for Cu nanoparticles. Figure 1 shows
TEM and SEM images of synthesized DFNS, and DFNS/
PEI/Cu catalysts, which the anchored Cu nanoparticles are
visibly diferentiable because of their contrast. Based on
Fig. 1a, c the DFNS NPs have an average size of 300 nm.
The Cu nanoparticles are spherical without significant
aggregation, and average diameter of 15–25 nm.
A typical experiment contains NaBH4 (2 mmol), DFNS/
PEI/Cu (25 mg), and the nitro compound (1 mmol) in
H2O (final volume of 2 ml). The reaction was continu-
ously stirred at 60°. Reaction progress was monitored
with TLC. Upon reaction completion, the catalyst was
removed, and eluted with ethanol. The reaction mixture
was extracted with ethyl acetate, and dried with Na2SO4.
The product was purified by column chromatography
using hexane–ethyl acetate in various concentrations.
Figure 2 shows X-ray difraction (XRD) analysis of the
synthesized catalysts. The main peak in 15°–35° range
belongs to amorphous silica as Cu NPs are too small. Nev-
ertheless, for commercial DFNS supported Cu NPs and free
Cu NPs, the difraction peaks (2θ) at 43.34°, 50.47°, and
Fig. 1 TEM photos of DFNS
(a), DFNS/PEI/Cu (b), SEM
images of DFNS (c), and
DFNS/PEI/Cu (d)
1 3

DFNS/PEI/Cu Nanocatalyst for Reduction of Nitro-aromatic Compounds
74.17° belongs to Cu (111), (200), and (220) which indicat-
ing cubic Cu (JCPDS No. 04-0836).
Thermal constancy of the DFNS/PEI/Cu NPs was
assessed in room temperature to 800 °C range by thermo-
gravimetric analysis (Fig. 3). The load loss below 250 °C
was because of the removal of the physisorbed and chem-
isorbed solvent from the silica material surface. The
observed organic weight losses for DFNS/PEI/Cu were
12.7% indicating excellent grafting yields of the organic
combinations on the NPs.
FTIR pattern shows presence of surface phosphate,
hydroxyl, and silanols groups, organic groups in (a) DFNS
and (b) amino-functional DFNS (Fig. 4). The larger absorb-
ing bands in 1084 cm−1 and 3651 cm−1 belongs to Si–O–Si
asymmetric stretching with OH. Two peaks at 801 cm−1 and
462 cm−1 are for Si–O–Si symmetric stretching, and bending
(Fig. 4a). These FTIR spectrums confrms successful graft-
ing of DFNS with GMSI. The DFNS/PEI composite dis-
plays linkages at 1094, 796 and 463 cm−1. A large absorbing
band about 3000–3550 cm−1 is associated with the –OH and
–NH stretching vibrations. Peak emerged around 2971 cm−1
is attributed to the stretching of the aliphatic group C–H
(Fig. 4b).
Fig. 2 XRD analysis of DFNS/PEI/Cu NPs
Table 1 shows that it can be ascribed to the fbrous struc-
ture. For DFNS, the N2 adsorption–desorption isotherms
of the nanostructure of DFNS displayed the specifc sort IV
curve. The BJH pore diameter, total pore volume, and BET
surface area, were determined to be 11 nm, 3.4 cm3/g, and
659 m2/g, respectively for DFNS, whereas these numbers
reduced to 8 nm, 2.1 cm3/g, and 438 m2/g for DFNS/PEI.
However, presence of the Cu NPs decreases porosity and
pore volume more signifcantly indicating Cu NPs formation
inside DFNS/PEI pores.
Fig. 3 TGA curve of (a) DFNS, and (b) DFNS/PEI/Cu NPs
The catalytic performance of the DFNS/PEI/Cu nano-
structures was tested in reducing nitro aromatic compounds
Fig. 4 FTIR spectra of (a)
DFNS MNPs, and (b) DFNS/
PEI/Cu MNPs
1 3

M. Moradi et al.
100
90
80
70
60
50
40
30
20
10
0
Table 1 Structural factors of DFNS, DFNS/PEI, and DFNS/PEI/Cu
materials calculated from studies on nitrogen sorption
Catalysts
SBET (m2/g)
Vt (cm3/g)
DBJH (nm)
DFNS
DFNS/PEI
DFNS/PEI/Cu
659
438
269
3.4
2.1
1.2
11
8
3
Table 2 Reduction of para-nitrophenol in the attendance of various
values of NaBH4 in diferent solvents by DFNS/PEI/Cu NPs
0
5
10
15
20
25
30
35
Catalyst (mg)
Entry Source of hydrogen Solvent
Time (min) Yield (%)
Fig. 5 Yield% dependence on the amount of DFNS/PEI/Cu NPs
1
2
3
4
5
6
7
8
NaBH4 (0.5 mmol) H2O
NaBH4 (1.0 mmol) H2O
NaBH4 (1.5 mmol) H2O
NaBH4 (2.0 mmol) H2O
NaBH4 (2.5 mmol) H2O
NaBH4 (2.0 mmol) H2O
NaBH4 (2.0 mmol) H2O
NaBH4 (2.0 mmol) H2O
NaBH4 (2.0 mmol) CH3OH
NaBH4 (2.0 mmol) EtOH
NaBH4 (2.0 mmol) CH3CN
NaBH4 (2.0 mmol) CH2Cl2
NaBH4 (2.0 mmol) DMSO
NaBH4 (2.0 mmol) n-Hexane
6
6
6
6
6
4
3
2
3
3
3
3
3
3
23
61
90
98
98
98
98
54
92
89
31
28
24
19
9
10
11
12
13
14
in presence of NaBH4 as the hydrogen source. First, the
impact of solvent type and molar ratio of hydrogen sources
on the model reaction were studied (Table 2, entries 1–14).
We found the highest reaction yield (98%) occurs in water
with 2.0 mmol NaBH4 (Table 2, entry 4). Increasing NaBH4
concentration from 0.5 to 2.0 mmol improves the rate of
paranitrophenol reduction in water (Table 2, entries 1–5).
Reduction process was very slow in aprotic solvents like
CH3CN, CH2Cl2, DMSO (Table 2, entries 11–13) and non-
polar solvent like n-hexane (Table 2, entry 14). Whereas,
protic solvents like H2O, CH3OH, EtOH enhance catalytic
kinetics (Table 2, entries 9–10). We chose water as the sol-
vent, due to its biological and environmental relevance, and
fxed 2 mmol NaBH4 for rest of this study.
We then studied efect of catalyst content on the model
reaction. There was no reduction activity in the absence
of neither catalyst nor DFNS/PEI/Cu NPs. Increasing the
amount of catalyst from 1 to 25 mg/mmol of substrate
improves reaction efciency, potentially due to increase in
the number of active sites (Fig. 5).
Fig. 6 UV–vis spectra of a 4-NP before and after adding NaBH4
solution, and b the consecutive reduction of 4-NP to 4-AP
DFNS/PEI/Cu NPs and 2 mm NaBH4 prompted decline in
the intensity of maximum peak of 4-NP (in 400 nm) with
the simultaneous increase in intensity of the 4-AP maximum
peak at 300 nm. The reaction was completed with the 98%
conversion in 180 s (Fig. 6b).
Reduction of 4-NP to 4-AP causes a red shift from 400 to
300 nm which we used as a probe to study reaction kinetic
of DFNS/PEI/Cu NPs in presence of NaBH4. Using 25 mg
1 3

DFNS/PEI/Cu Nanocatalyst for Reduction of Nitro-aromatic Compounds
0.4
0.35
0.3
Table 3 Reduction of various nitro-aromatic compounds over DFNS/
PEI/Cu NPs
Entry
1
Reactant
Product
Yield (%)a
87
Mp (°C)
Liquid
0.25
0.2
Reactant
NH2
NO2
0.15
0.1
0.05
0
0
30
60
90
120
150
180
2
3
98
99–102
NO2
NH2
NH2
Reacꢀon Time (s)
NH2
NH2
Fig. 7 The scheme of Ct/C0against reaction time for the reduction of
4-NP over DFNS/PEI/Cu NPs
99
138–140
NO2
The reaction conversion is quantifed with Ct/C0 using the
relative strength of UV–vis absorbance (At/A0) (at 400 nm).
Ct shows the concentration of 4-NP at time t whereas C0
indicates the initial concentration. Figure 7 shows the mean
value of the reaction conversions over reaction period. Fig-
ure 8 illustrates the linear correlation between ln(Ct/C0) vs.
time indicating that 4-NP reduction is a frst-order reaction
that can be formulized as ln(Ct/C0)= −kt. k, reaction rate
constant, was 0.981 s−1 for 4-NP reduction by DFNS/PEI/Cu
NPs. The activity factor, k′=k/M, where M is the catalyst
mass, was calculated to be 9.81/s/g.
NO2
NO2
NH2
NH2
4
96
62–64
NO2
NH2
We tested reduction of diferent nitro-aromatic com-
pounds using the optimized condition (Table 3). The out-
comes (Table 3) demonstrate, electron with drawing/donat-
ing substituents do not have a major infuence on the reaction
times and yields (Table 3, entries 6–12). Dinitro compounds
were also successfully converted to their diamines reduced
states. Dinitro compounds are important precursors in vari-
ous heterocyclic combinations in engineering polymers and
composites (Table 3, entries 3–5).
5
6
98
101–104
58–61
NO2
NH2
NO2
NH2
94
NO2
NH2
OCH3
NO2
OCH3
6
5
4
3
7
92
39–41
NH2
2
1
0
R² = 0.9813
CH3
CH3
0
20
40
60
80
100
120
140
160
180
Reacꢀon Time (s)
Fig. 8 The scheme of ln(Ct/C0) against reaction time for the reduction
of 4-NP over DFNS/PEI/Cu NPs
1 3

M. Moradi et al.
Table 3 (continued)
cleavage of B–H bond is the rate‐determining stage in
nitroarenes reduction by NaBH4 catalyzed by Cu nanoparti-
cles. In the metal–hydrogen structure, the negatively charged
hydrogen may attack the positively charged nitrogen in the
nitrophenols. As a result, the nitro group is decreased to
the nitro with the reductive addition of two hydrogen atoms
forming hydroxylamine. Fianlly, the hydroxylamine is fur-
ther reduced to the aniline derivative.
Entry
8
Reactant
Product
Yield (%)a
97
Mp (°C)
182–185
NO2
NH2
To measure reusability of developed catalysis, we recov-
ered the DFNS/PEI/Cu NPs by fltration after the reaction.
The particles were then washed by methanol, dried, and
reused in a new reaction. We repeated this process for 10
cycles with no notable loss in catalytic activity (Fig. 9). This
observation adds another economic beneft for application
of DFNS/PEI/Cu NPs in removing pollutants.
OH
OH
9
93
97
99
105–108
184–187
NO2
NH2
The loading amounts of Cu NPs in the DFNS/PEI/Cu and
DFNS/Cu NPs were determined by ICP-MS to be 1.6, and 1.8
wt%, respectively. Equal metal loading amounts were almost
obtained in both nanocomposites. In addition, Cu NPs leaching
was monitored for 10 reaction cycles. The loading amount of
Cu NPs was seen to be 1.5 wt%, which showed insignifcant
Cu NPs leaching for at least 10 cycles. However, the amount
of Cu NPs in the DFNS/Cu NPs dropped to 1.1 wt%. This
fnding emphasizes the role of α-CD in preventing Cu NPs
aggregation and releasing and recovering Cu NPs during the
reaction process (Table 4).
O
O
O
10
NO2
NH2
OH
O
OH
11
12
204–207
65–68
NO2
NH2
4 Conclusions
NH2
NH2
In this study, we synthesised and suggested a new nano-
catalyst that named DFNS/PEI/Cu NPs. This nanocatalyst
along with nanoparticles of Cu as the active sites may not
just decrease Cu NPs usage without decreasing catalytic
activity. In addition, this may confer heterogeneous char-
acteristics to the nanocatalyst, causing the catalyst simple
to retrieve for reuse. The DFNS/PEI/Cu NPs displayed
proper catalytic activity in term of 4-NP and 2-NA reduc-
tion. It can be due to the high availability of the DFNS/
PEI/Cu NPs support material as well as the low value of
the Cu NPs aggregation on the DFNS/PEI support. In
addition, one can reuse DFNS/PEI/Cu NPs at least 10
times that can be because of the prevention of leaching of
Cu NPs from the DFNS/PEI/Cu NPs (without occurring
any reduction in catalytic activity).
CN
CN
97
NO2
NH2
NH2
NH2
Cl
Cl
aIsolated yield
Scheme 2 display a illustration of the reaction along with
the hydrides activation on the catalyst surface and their
transfer to the nitro group. According to previous studies,
1 3

DFNS/PEI/Cu Nanocatalyst for Reduction of Nitro-aromatic Compounds
Scheme 2 A proposed
OH
OH
N
OH
N+
OH
N
mechanism for the reduction of
p-nitrophenol catalyzed by the
DFNS/PEI/Cu NPs catalyst in
the presence of NaBH4
N
O
-O
H
H
H
O
OH
H
H
H
H
H
H
Adsorption
Desorption
Reduction
Reduction
Cu
Cu
Cu
Cu
Hydrides
BH4
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14. Motevalizadeh SF, Alipour M, Ashori F, Samzadeh-Kermani A,
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Entry
Catalyst
wt %
1
2
3
4
DFNS/PEI/Cu
DFNS/Cu
DFNS/PEI/Cu after 10 reuses
DFNS/Cu after 10 reuses
1.6
1.8
1.5
1.1
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