Immobilized some of vanadium compounds on modified graphene oxide as nanofiber network for epoxidation of allyl alcohols

Article abstract of DOI:10.1002/aoc.6151

VO(acac)₂ and the in situ generated VO(Salen) complex were immobilized on the covalently modified graphene oxide (GO) with ethylenediamine (en) and designated as VO(acac)₂@en-GO and VO@Salen@en-GO, respectively. Characterization of the prepared compounds was carried out with FT-IR, XRD, ICP, CHN, Raman, SEM, TEM, and BET techniques. The SEM results confirmed the formation a nanofiber network and nanointerconnected needles. The prepared immobilized complexes were then used as heterogeneous catalysts for epoxidation of some allyl alcohols such as geraniol, trans-2-hexene-1-ol, and 1-octen-3-ol. Based on the results obtained by GC and GC–mass analyses, epoxidation of geraniol with 97% conversion and 100% selectivity seemed promising. Readily recycling of the catalyst and reusing for four successive catalytic runs without significant loss of activity revealed that this catalysis system deserves nomination for practical application.

Full text of DOI:10.1002/aoc.6151

Received: 30 August 2020
DOI: 10.1002/aoc.6151
Revised: 3 December 2020
Accepted: 14 December 2020
F U L L P A P E R
Immobilized some of vanadium compounds on modified
graphene oxide as nanofiber network for epoxidation of
allyl alcohols
Faezeh Farzaneh
| Zahra Ahmadi
| Zahra Azarkamanzad
|
Maryam Ghahremani
Department of Chemistry, Faculty of
Physics & Chemistry, Alzahra University,
Tehran, Iran
VO(acac) and the in situ generated VO(Salen) complex were immobilized on
2
the covalently modified graphene oxide (GO) with ethylenediamine (en) and
designated as VO(acac) @en-GO and VO@Salen@en-GO, respectively. Char-
2
Correspondence
Faezeh Farzaneh, Department of
Chemistry, Faculty of Physics &
Chemistry, Alzahra University, P.O. Box:
acterization of the prepared compounds was carried out with FT-IR, XRD,
ICP, CHN, Raman, SEM, TEM, and BET techniques. The SEM results con-
firmed the formation a nanofiber network and nanointerconnected needles.
The prepared immobilized complexes were then used as heterogeneous cata-
lysts for epoxidation of some allyl alcohols such as geraniol, trans-2-hexene-
1993891176, Vanak, Tehran, Iran.
Email: farzaneh@alzahra.ac.ir;
faezeh_farzaneh@yahoo.com
1-ol, and 1-octen-3-ol. Based on the results obtained by GC and GC–mass
analyses, epoxidation of geraniol with 97% conversion and 100% selectivity
seemed promising. Readily recycling of the catalyst and reusing for four suc-
cessive catalytic runs without significant loss of activity revealed that this catal-
ysis system deserves nomination for practical application.
K E Y W O R D S
allyl alcohols, epoxidation, modified graphene oxide, Schiff base complex,
vanadylacetylacetonate
1
| INTRODUCTION
Reactive species can readily access the active sites with
limited mass transfer resistance. Therefore, remarkable
To date, the application of heterogenized homogeneous
catalysts is interested due to economical and environ-
mental reasons. In fact, immobilization of metal com-
plexes with covalent binding on different supports
catalytic performance of graphene oxide (GO) as
supported catalysts has been observed owing to the pres-
ence of plenty of hydroxyl, epoxy, carboxyl, and carbonyl
groups. Oxygen functionality modifications can establish
[1–3]
[18–22]
through ligand spacer is a common method.
A wide
as active site for anchoring ions and complexes.
range of matrixes has been developed for covalent attach-
Therefore, it has been recognized as an ideal candidate
for supporting various transition metal complexes.
[4,5]
[2]
ments such as inorganic mesoporous,
or microporous
and modified
[6]
[7,8]
materials, metal–organic frameworks,
Modification of GO by some reagents such as three met-
hoxysilane (TMS) and ethylenediamine has been exten-
[9,10]
magnetic nanoparticles.
Recently, two-dimensional
[
23–26]
supports such as graphite and graphite oxide with unique
sively investigated.
In recent years, remarkable
[
11–13]
properties
have emerged as ideal supports for a vari-
catalytic reactions have been carried out using GO or
[
14–17]
ety of catalytic species.
Besides the availability of
modified GO as supports for reactions such as Suzuki–
[
14]
surface functionalization, their two-dimensional struc-
tures allow excellent dispersion of the catalytic species.
Miyaura coupling reaction,
decomposition of
immobilization of
[
16]
[27]
phenol,
photodegradation,
Appl Organomet Chem. 2021;35:e6151.
wileyonlinelibrary.com/journal/aoc
© 2021 John Wiley & Sons, Ltd.
1 of 11
https://doi.org/10.1002/aoc.6151

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FARZANEH ET AL.
[
19]
enzymes as catalyst for many organic reactions,
epoxidation of some alkenes.
and
He. Chemical analyses were performed with Varian
150AX inductively coupled plasma optical emission spec-
trometer (ICPOES). Elemental analyses were performed
on a Heraeus CHN Rapid elemental analyzer.
[23,28,29]
Epoxides are
starting materials for the synthesis of commercial prod-
ucts. Some transition metal compounds with their redox
properties such as Ti, Fe, Co, Mn, Mo, Cr, and V are
known as active catalysts for epoxidation-type reactions.
Among these metals, vanadium compounds have
attracted increasing attention due to the redox activity
and biological properties. Also, vanadium with multiple
oxidation state acts as a Lewis acid in oxovanadium(IV)
compounds due to low radius to charge ratio and with
high affinity for oxygen transformation reactions. The
biomimetic roles of vanadium compounds in biochemical
process such as phosphorylation, insulin mimicking,
nitrogen fixation, and Haloperoxidation are interesting
2.2 | Synthesis of GO
[34]
GO was prepared by the modified Hummers' method.
Briefly, graphite powder (2 g) and sodium nitrate (1 g)
were dissolved in sulfuric acid (45 mL) and stirred vigor-
ously for half an hour in an ice bath. Then, potassium
permanganate (5 g) was added to the mixture below
ꢀ
20 C. The mixture which turned from dark black to
green was kept stirring for half an hour. The ice bath was
[30–33]
ꢀ
subject for studying.
then removed, and stirring continued at 35–40 C for
In this study, the vanadium compounds were
immobilized on the modified GO and used as heteroge-
neous catalyst for epoxidation of some allyl alcohols.
another 1 h. Water (45 mL) was then slowly added, and
ꢀ
the temperature raised to 98 C and allowed to stand for
40 min with vigorous agitation. Finally, water (200 mL)
and H O (30%, 6 mL) were added, and the mixture cen-
2
2
trifuged and washed with distilled water for 10 times and
[
35,36]
2
2
| EXPRIMENTAL
then dialyzed to obtain the pure GO powder.
C 52.32, %H 2.2%.
Found
%
.1 | Materials and instrumentation
All chemicals were purchased from Merck Chemical
Company and used without further purification. XRD
patterns of powdered samples were carried out on STOE-
2.3 | Reduction and surface modification
of GO: Synthesis of modified GO
STADI diffractometer using Cu Kα radiation
In a typical experiment and based on the previously
ꢀ
[37]
(
k = 1.5406 Å) in the 2θ range of 10–60 with accelerating
reported
procedure,
ethylenediamine
voltage and current of 40 kV and 40 mA, respectively.
Scanning electron microscopy (SEM) images were
obtained on a Philips XL-30ESEM equipped with an X-
ray energy dispersive detector. Transmission electron
microscopy (TEM) images were also obtained on Zeiss
EM10C-100 KV model. N2 adsorption–desorption iso-
therms were measured with a MicrotracBEL BELSORP
(NH (CH ) NH ) (en) (600 mg) was dissolved in ethanol
2 2 2 2
(35 mL) and added dropwise to a suspension of GO
(200 mg) in water (33 mL) under vigorous stirring. The
reaction continued for 24 h at room temperature. The
resulting mixture was isolated by centrifugation and thor-
oughly washed with a 1:1 ethanol/water mixture
ꢀ
followed by drying in a vacuum oven at 80 C for 12 h
mini system at liquid N temperature. Before measure-
ments, the sample was outgassed at 120 C for 6 h. The
prior to characterization. Found %C 57.53, %N 5.95,
%H 2.8.
2
ꢀ
surface area was calculated using the Barrett–Emmett–
Teller (BET) method. FT-IR spectra were recorded on a
Bruker instrument using KBr pellet technique in the
2.4 | Preparation [VO(acac)2]
−
1
range of 4000–400 cm . Raman spectra were obtained
using a microspectrometer (Takram P50C0R10) at the
laser wavenumber of 631 nm between 400 and 1800 cm−
The oxovanadium complex [VO(acac) ] was prepared
2
1
[38]
based on the previously reported procedure.
A mixture
(dry powder samples). The products were analyzed by gas
of V O (5 g), distilled water (15 mL), concentrated sulfu-
2 5
chromatography (GC) (Agilent Technologies, 6890 Series
GC System, HP-5 Phenyl Methyl Siloxane Capillary,
ric acid (9 mL), and ethanol (25 mL) was boiled with stir-
ring for 30 min. After filtration, freshly distilled
acetylacetone (13 mL) was added to the filtrate followed
by slow addition of sodium carbonate (20 g of Na CO in
3
0 m × 530 μm × 1.5 μm Nominal, Carrier Gas; He). GC–
MS analyses were performed using an 5973 Network
Mass Selective Detector, 6890 Network, GC System,
Column; HP Phenyl Methyl Siloxane Capillary,
2
3
125 mL of water). Recrystallization of the obtained solid
from chloroform finally afforded the [VO(acac) ] as blue
2
3
0 m × 530 μm × 1.5 μm Nominal, Carrier Gas;
crystals.

FARZANEH ET AL.
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ꢀ
2
.5 | Immobilization of VO(acac) on
with ethanol for three times and dried in an oven at 70 C
for 24 h.
2
modified GO: Synthesis of VO(acac) @en-
2
GO
Modified GO (0.2 g in 15-mL ethanol) was stirred for
2.7 | Preparation of VO@Sal@en-GO
1
0 min (Solution 1). Subsequently, VO(acac) (0.2 g) in
2
distilled water (10 mL) (Solution 2) was slowly added to
Solution 1 while stirring, and the mixture heated at reflux
for 24 h. After filtering the mixture, the obtained solid
Sal@en-GO (0.2 g) in ethanol (15 mL) (Solution 1) was
added to VOSO (0.2 g) in water (10 mL) (Solution 2) and
4
stirred for 24 h. The obtained solid was washed with eth-
ꢀ
ꢀ
was washed with ethanol and dried at 70 C in an oven.
anol for three times and then dried in an oven at 70 C for
Vanadium content was found to be 14.82%.
24 h. Vanadium content was found to be 15.76%.
2.6 | Preparation of Sal@en-GO
2.8 | General procedure for epoxidation
of some allyl alcohols
Salicylaldehyde (10 mmol, 1.22 g) in ethanol (35 mL) was
slowly added to a suspension of en-GO (0.2 g) in water
The catalytic activity of VO(acac) @en-GO was investi-
2
(
33 mL), and the mixture was heated at reflux for 24 h.
gated in the epoxidation of geraniol (or other allyl alco-
hols) in acetonitrile. Typically, the desired amount of
The obtained solid product was separated and washed
FIGURE 1 Immobilized vanadium compounds on en-GO

4
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FARZANEH ET AL.
catalyst, substrate (10 mmol), and TBHP (12 mmol) in
acetonitrile (5 mL) was heated at reflux for the desired
time. Upon completion, the catalyst was separated by
ꢀ
centrifugation, washed with ethanol, and dried at 100 C.
The filtrate was then subjected to GC and GC–mass anal-
ysis for identification of products.
3
| RESULTS AND DISCUSSION
As presented in Figure 1, GO was initially prepared by
[
34]
Hummers' method
ylenediamine (en).
and modified with eth-
[
37]
VO(acac) and the in situ gener-
2
ated VO(Salen) were subsequently immobilized onto the
modified GO and designated as VO(acac) @ en-GO and
2
VO@Sal@en-GO, respectively.
3
.1 | Characterization of VO(acac) @en-
2
GO and VO@Sal@en-GO by FT-IR
The FT-IR spectra of GO, en-GO, and VO(acac) @en-
2
GO, Sal@en-GO, and VO@Sal@en-GO are shown in
Figure 2a–e, respectively. Observation of a peak at
1
3
(
2
419 cm− is due to the O–H stretching vibration of GO
Figure 2a). Additional peaks observed at 2922 and
853 cm− are attributed to the C–H stretching vibra-
1
−
1
tions. Observation of peaks at 1704, 1625, and 1384 cm
are due to the carboxyl C=O, aromatic C=C, and car-
[
39]
boxyl O–H groups, respectively.
Whereas the peak
−
1
FIGURE 2 FT-IR spectra of (a) GO, (b) en-GO,
c) VO(acac) @en-GO, (d) Sal@en-GO, and (e) VO@Sal@en-GO
displayed at 1222 cm
is attributed to the C–OH
[40]
−1
(
2
stretching vibrations,
is due to the epoxide C–O group.
with en (Figure 2b) results in the appearance of two
the other observed at 1052 cm
[
39]
Modification of GO
−
1
new peaks centered at 3446 and 1560 cm due to N–H
3.2 | XRD of VO(acac) @en-GOand
2
[37]
and C–N stretchings
together with a decrease in the
VO@Sal@en-GO
intensities of the peaks at 1222 cm−1 and 1052 due to
the epoxy and alkoxy groups perhaps due to the nucleo-
The XRD patterns of GO, en-GO, VO(acac) @en-GO,
2
philic substitution of −NH to the epoxide carbon and
Sal@en-GO, and VO@Sal@en-GO are shown in
2
the β-carbon of −OH groups. Therefore, the removal of
oxygen functionalities from the surface of GO as well as
the formation of amine-functionalized graphene is con-
Figure 3a–e, respectively. The XRD pattern of GO
ꢀ
(Figure 3a) shows a peak at 2θ = 11.1 due to the oxy-
genic functional groups and trapped water molecules
[37]
−1
[43]
cluded.
seen in Figure 2c
Finally, the presence of a peak at 970 cm as
between the graphite layers.
Compared with the pure
[41,42]
due to the V=O vibration con-
GO (Figure 3b), the 001 reflection peak shifted in en-GO
perhaps due to the grafting of ethylenediamine into the
firms the immobilization of vanadium salt onto the
modified GO.
[
37]
GO layers.
FT-IR spectra of Sal@en-GO and VO@Sal@en-GO
are shown in Figure 2d,e, respectively. The vibration of
After immobilization of VO(acac) complex onto the
2
ꢀ
en-GO surface, the diffraction peak observed at 11.1 is
−
1
ꢀ
C=N in Sal@en-GO appearing at 1645 cm (Figure 2d)
shifted to a lower frequency after coordination to the
shifted to 10 , consistent with those reported previ-
[
43]
ously.
Moreover, the XRD pattern of VO(acac) @en-
2
2
+
[28]
ꢀ
VO
ions (Figure 2e).
Moreover, observation of
GO shows a broad peak at 2θ = 26.09 (Figure 3c),
−
1
another peak at 976 cm was attributed to the V=O
stretching vibrations (Figure 2e).
confirming that the major oxygen-containing groups
[41,42]
[23]
of GO have been successfully functionalized.
The

FARZANEH ET AL.
5 of 11
2
FIGURE 4 Raman spectra of (a) en-GO, (b) VO(acac) @en-
GO, (c) Sal@en-GO, and (d) VO@Sal@en-GO
these two peaks reduced and shifted to 1560 and
−1
1
300 cm , respectively. The shifting in GO occurs due to
the functionalization of GO with en (Figure 4a). The
obtained results are consistent with those reported
[
37,44,45]
before.
Particularly significant is observation of a
peak at 970 cm− after immobilization of VO(acac) due
1
FIGURE 3 The XRD patterns of (a) GO, (b) en-GO,
2
(
c) VO(acac)
2
@en-GO, (d) Sal@en-GO, and (e) VO@Sal@en-GO
to the VO stretching vibration (Figure 4b). The other
notable point is the decrease in I /I of GO from 0.97 to
D
G
[
37]
0
.94, due to functionalization of GO with en.
On the
other hand, formation of Sal@en-GO and the position of
two peaks due to the en-GO did not changed (Figure 4c).
XRD patterns of Sal@en-GO and VO@Sal@en-GO
shown in Figure 3d–e indicate their similar XRD pat-
terns. After formation of VO@Sal@en-GO, the peak
After immobilization of VOSO on Sal@en-GO due to the
4
formation of VO@Sal@en-GO, very small peak due to
the VO is observed in which its intensity is very low
(Figure 4d).
ꢀ
observed nearly at 2θ = 11.1 is shifted and appears as
ꢀ
a broader peak at 2θ = 10 , consistent with those
[43]
reported before.
The SEM images of GO, VO(acac) @en-GO, and
2
VO@Sal@en-GO are shown in Figure 5a–c, respectively.
Based on the SEM images, the formation of nanofiber
network and nanointerconnected needles after immobili-
zation of vanadium compounds onto the en-GO is
confirmed.
3
.3 | Raman spectra of VO(acac) @en-
2
GO and VO@Sal@en-GO
Recall that the Raman spectroscopy is very sensitive to
the electronic structure of carbon-based materials. The
The TEM images of VO(acac) @en-GO and
2
VO@Sal@en-GO are also shown in Figure 6a–c with two
magnifications, respectively. Nanofiber network and
nanointerconnected needles are observed.
Raman spectra of en-GO, VO(acac) @en-GO, Sal@en-
2
GO, and VO@Sal@en-GO are shown in Figure 4a–d.
Raman spectra of GO are characterized by two main
The nitrogen adsorption–desorption isotherms of GO,
−
1
peaks generally observed at 1575 and 1349 cm which
en-GO, VO(acac) @en-GO, and VO@Sal@en-GO are
2
2
3
are due to the sp - and sp -hybridized carbon atoms in
shown in Figure 7 and Table S2. As seen in this figure,
the abovementioned materials indicate the Type IV
[37]
GO.
After functionalization with en, the intensity of

6
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FARZANEH ET AL.
FIGURE 5 SEM images of (a) GO,
b) VO(acac) @en-GO, and (c) VO@Sal@en-
GO
(
2
FIGURE 6 TEM images of
a) VO(acac) @en-GO and (b) VO@Sal@en-
(
2
GO with two magnifications
isotherms with hysteresis loop at a relative pressure of
.4 < p/p0 < 1. The surface areas of GO, en-GO,
VO(acac) @en-GO, and VO@Sal@en-GO are 5.6392,
vanadium complex on the GO surface is probably due to
the new morphology formation on the surface of GO
based on the SEM and TEM results (Figures 5 and 6).
The obtained results are consistent with some reported
0
2
2
6
.5234, 16.916, and 12.715 m /g, respectively. This
[
46,47]
increase of the surface area after complexation of
articles.

FARZANEH ET AL.
7 of 11
occurred by using 50 mg of the catalyst during the similar
reaction times (entries 4–6, Table 1). Therefore, 10 mg of
the catalyst was used within 2 h for other experiments.
The effect of solvent on the geraniol epoxidation is
given in Table 2. As seen in this table, whereas oxidation
reactions proceed effectively in acetonitrile, chloroform,
and dichloromethane (entries 1–3, Table 2), they are
rather sluggish in ethanol and methanol (entries 4–5,
Table 2).
Having established the optimal reaction conditions,
we examined the generality of this epoxidation on sub-
strates such as geraniol, trans-2-hexen-1-ol, and 1-octen-
3-ol in refluxing acetonitrile using 10 mg of catalyst (VO
(
acac) @en-GO and VO@Sal@en-GO) (Table 3). To
2
avoid any overestimation of the catalytic activity of the
systems under investigation, the catalytic activity (TON
and TOF) of VO(acac) @en-GO and VO@Sal@en-GO
2
FIGURE 7
2
N adsorption–desorption isotherms of GO, en-GO,
has been calculated and included in Table 3. We have
included the effect of the modified en-GO on the epoxida-
tion (entry 7, Table 3) in order to make comparison with
2
VO(acac) @en-GO, and VO@Sal@en-GO
4
| CATALYTIC STUDIES
both (VO(acac) @en-GO and VO@Sal@en-GO) more
convenient. Compared with the effect of en-GO which is
totally ineffective as epoxidation catalyst for geraniol
2
VO(acac) @en-GO and geraniol were used as models in
2
order to find the optimum reaction conditions. For this
purpose, various parameters such as the effect of catalyst
amount, reaction time, and solvent were evaluated. It
was found that whereas utilization of 10 mg of catalyst
within 1, 1.5, and 2 h partially improved geraniol conver-
sion (entries 1–3, Table 1), no increase in the conversion
(entry 7, Table 3), the other two VO(acac) @en-GO and
2
VO@Sal@en-GO exhibit catalytic activity for the conver-
sion of geraniol to the corresponding epoxide with 97%
and 88% yields, respectively (entries 1 and 4, Table 3). On
the other hand, trans-2-hexen-1-ol and 1-octen-3-ol
undergo epoxidation under the catalytic effect of (VO
a
TABLE 1 Conversion and selectivity of geraniol with different amounts of the VO(acac)
2
@en-GO as catalyst at different reaction times
1
Entry
Amounts of catalyst (mg)
Time (h)
Conversion (selectivity)%
94 (100)
TON
323
330
334
61
TOF (h−
323
220
167
61
)
1
2
3
4
5
6
1
10
1.5
2
96 (100)
97 (100)
1
89 (100)
50
1.5
2
94 (100)
65
43
94 (100)
65
32
a
Reaction conditions: 10 and 50 mg catalyst, 10 mmol geraniol, 12 mmol TBHP, 5 mL CH CN. Entries 1–3 using 10 mg and entries 4–6 using 50 mg catalysts.
3
TABLE 2 Conversion and
TOF (h−1
)
Entry
Solvents
Conversion (selectivity)%
TON
selectivity of geraniol with
1
2
3
4
5
Acetonitrile
Chloroform
Dichloromethane
Ethanol
97 (100)
96 (100)
96 (100)
91 (100)
87 (98)
334
330
330
313
299
167
165
165
156
150
VO(acac)
2
@en-GO as catalyst in
a
different solvents
Methanol
a
Reaction conditions: 10 mg catalyst, 10 mmol geraniol, 12 mmol TBHP, 5 mL solvent.

8
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FARZANEH ET AL.
TABLE 3 Results obtained for catalyzed epoxidation of some allyl alcohols
1
Entry
Catalysts (mg)
VO(acac) @en-GO
Substrate
Conversion (selectivity)%
TON
334
51
TOF (h−
)
a
1
2
3
4
5
6
7
2
Geraniol
97 (100)
74 (100)
36 (100)
88 (100)
71 (100)
43 (75)
0
167
17
2
b
b
trans-2-Hexen-1-ol
c
1-Octen-3-ol
25
a
VO@Sal@en-GO
en-GO
Geraniol
293
46
147
15
2
trans-2-Hexen-1-ol
c
1-Octen-3-ol
28
a
Geraniol
-
-
a
Reaction conditions:10 mg catalyst, 10 mmol geraniol, 12 mmol TBHP, 5 ml CH
3
CN, reflux for 2 h.
b
Reaction conditions: 50 mg catalyst, 10 mmol trans-2-hexen-1-ol, 12 mmol TBHP, 5 ml CH
3
CN, reflux for 3 h.
c
Reaction conditions: 50 mg catalyst, 10 mmol 1-octen-3-ol, 12 mmol TBHP, 5 ml CH
3
CN, reflux for 12 h.
(
acac) @en-GO and VO@Sal@en-GO) although in a
To explore the reusability of the catalysts, it was sepa-
2
lesser extent than geraniol (entries 2–3 and 5–6, Table 3).
To make insight into the reaction mechanism, epoxi-
dation of geraniol was carried out in the presence of
rated at the end of reaction and reused in another reac-
tion after washing several times with acetonitrile and
drying. It was found that the conversion of geraniol epox-
idation slightly dropped from 97% to 91% and 88 to 85%
[48–50]
diphenylamine as a radical scavenger.
Observation
of no conversion inhibition indicated that reaction does
not proceed through a radical mechanism. Therefore, it
can be concluded that oxygen transfer from TBHP to allyl
alcohols has proceeded via a concerted mechanism
after using VO(acac) @en-GO and VO@Sal@en-GO in
four runs, respectively (Figures 8 and 9).
2
(Scheme 1). After the formation of Intermediates I and II
via interaction of vanadium heterogeneous catalyst with
TBHP and allyl alcohol, Intermediate III is generated
through nucleophilic attack of the double bond to the
electrophilic oxygen atom of the coordinated TBHP
(Scheme 1). Subsequently, the epoxide resulted with
elimination of t-BuOH and regeneration of catalyst. The
decrease in conversion rates from geraniol to trans-
2
-hexen-1-ol and 1-octen-3-ol is an evidence in
supporting the suggested mechanism because the forma-
tion rate of III depends on the number of alkyl substitu-
tions present on the double bonds which in turn increase
[57]
their nucleophilic character accordingly.
Recall that
geraniol, trans-2-hexen-1-ol, and 1-octen-3-ol contain tri-,
2
FIGURE 8 Effect of recycling of VO(acac) @en-GO on
di-, and monosubstituted olefins, respectively.
geraniol epoxidation
SCHEME 1 Suggested mechanism for the
epoxidation of allyl alcohols catalyzed by
2
VO(acac) @en-GO

FARZANEH ET AL.
9 of 11
activity toward epoxidation of geraniol, the obtained
results confirmed the heterogeneous character of the cat-
alyst. The vanadium percent for VO(acac) @en-GO
2
before reaction was 14.82% and after reaction was
14.35%. The ICP determination for VO@Sal@en-GO
before and after reaction was 15.76% and 14.95%,
respectively.
4.1 | Comparison with other reported
systems
The catalytic activity of geraniol epoxidation with
FIGURE 9 Effect of recycling of VO@Sal@en-GO on geraniol
VO(acac) @en-GO and VO@Sal@en-GO was compared
2
epoxidation
with other reported catalysis systems (Table 4). It was
found that the VO(acac) @en-GO with 97% conversion
2
and 100% selectivity shows the most activity (TON and
TOF) relative to the other catalysts.
To further explore the stability of catalysts, the FT-IR
spectra (Figures S1a,b and S3a,b) and XRD patterns
(
Figures S2a,b and S4a,b) of VO(acac) @en-GO and
2
VO@Sal@en-GO) before and after using as catalyst on
geraniol epoxidation were found to be similar (see
Supporting Information). Such observations clearly indi-
cate the stability and heterogeneity character of these cat-
alysts. Moreover, because the filtrate did not show any
5 | CONCLUSION
In conclusion, GO was initially modified with eth-
ylenediamine (en) and designated as en-GO. Subse-
quently, VO(acac) and the in situ generated VO@Salen
2
2
TABLE 4 Comparison of figure of merit of the present work (catalyst VO(acac) @en-GO and VO@Sal@en-GO) with other studies in
the literature
Reaction conditions: amount
of catalysts, solvent,
temperature, time
Conversion
TON/TOF
Entry Catalysts (mg)
(selectivity)% (h−
1
)
Ref.
a
1
2
3
4
5
6
7
8
9
1
VO(acac)
VO@Sal@en-GO
CMK-3@[VO(acac)
CMK-3@APTES@[VO(acac)
[VO(acac) ]APTES@SiO
Fe @SiO –NH –VO(acac)
2
@en-GO
10 mg, CH
10 mg, CH
3
3
CN, reflux, 2 h
CN, reflux, 2 h
97 (100)
88 (100)
100 (97)
98 (98)
334/167
293/147
100/91
74/68
34/17
60/2
This work
This work
[51]
2
]
100 mg, CH
100 mg, CH
100 mg, CH
2
2
2
Cl
Cl
Cl
2
2
2
, RT, 2.5 h
, RT, 2.5 h
, RT, 2 h
b
[51]
2
2
] with amine
[
[
[
[
52]
53]
54]
54]
2
2
100 (99)
100 (96)
100 (97)
100 (98)
98 (98)
2
O
3
2
2
2 2
50 mg, CH Cl , RT, 30 h
[VO(acac)
[VO(acac)
[VO(acac)
2
2
2
]@APTES@laponite
]@APTES@K10
100 mg, CH
100 mg, CH
100 mg, CH
2
2
2
Cl
Cl
Cl
2
2
2
, RT, 48 h
, RT, 48 h
96/2
96/2
c
[55]
[56]
]@HMS
, RT, 48 h
96/2
ꢀ
0
8-Quinolinol oxovanadium(IV)
complex@graphene oxide
10 mg, CH
3
CN, 70 C, 8 h
83.7 (80)
199/25
d
[57]
[58]
1
1
1
1
2
3
Fe
3
O
4
@SiO
2
@APTMS@[VO
2
(bpca)]
50 mg, CH
3
CN, reflux, 1 h
100 (100)
42 (81)
155/155
e
[VO(acac)
[VO(acac)
2
2
]APTES@PCH
100 mg, CH
2
2
Cl
Cl
2
2
, RT, 48 h
, RT, 48 h
-
-
[58]
]APTES@SBA-15
100 mg, CH
34 (88)
a
3
Reaction conditions:10 mg catalyst, 10 mmol geraniol, 12 mmol TBHP, 5 ml CH CN, reflux for 2 h.
b
c
APTES, 3-aminopropyltriethoxysilane.
HMS, hexagonal mesoporous silica.
d
APTMS, 3-aminopropyltrimethoxysilane.
PCH, porous clay heterostructure.
e

10 of 11
FARZANEH ET AL.
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network and nanointerconnected needles have been
formed after immobilization of vanadium compounds
onto the modified en-GO. The prepared complex
compounds were used as heterogeneous catalysts for
epoxidation of some allyl alcohols such as geraniol,
trans-2-hexene-1-ol, and 1-octen-3-ol. The epoxidation of
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AUTHOR CONTRIBUTIONS
Faezeh Farzaneh: Conceptualization; supervision.
zahra ahmadi: Formal analysis; investigation; method-
ology. zahra azarkamanzad: Software. Maryam
Ghahremani: Formal analysis.
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Ind. Eng. Chem. Res. 2014, 53, 4232.
CONFLICT OF INTEREST
There are no conflicts to declare.
[
[
DATA AVAILABILITY STATEMENT
Research data are not shared.
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Faezeh Farzaneh https://orcid.org/0000-0001-5651-
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SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of this
article.
How to cite this article: Farzaneh F, Ahmadi Z,
Azarkamanzad Z, Ghahremani M. Immobilized
some of vanadium compounds on modified
graphene oxide as nanofiber network for
epoxidation of allyl alcohols. Appl Organomet
Chem. 2021;35:e6151. https://doi.org/10.1002/aoc.
6151
[
[
[