Molybdenum (VI)-functionalized UiO-66 provides an efficient heterogeneous nanocatalyst in oxidation reactions

Article abstract of DOI:10.1002/aoc.5225

A novel heterogeneous nanocatalyst was established by supporting molybdenum (VI) on Zr₆ nodes in the structure of the well-known UiO-66 metal–organic framework (MOF). The structure of the UiO-66 before and after Mo (VI) immobilization was confirmed with XRD, DR-FTIR and UV–vis spectroscopy, and the presence and amount of Mo (VI) was identified by X-ray photoelectron spectroscopy and inductively coupled plasma atomic emission spectroscopy. TEM imaging confirmed the absence of Mo clusters on the MOF surface, while SEM confirmed that the appearance of the MOF has not changed upon immobilizing the Mo (VI) catalyst. BET adsorption measurements were used to confirm the porosity of the catalyst. The catalytic activity of this heterogeneous catalyst was investigated in oxidation of sulfides with H₂O₂ in acetonitrile and oxidative desulfurization of dibenzothiophene. Easy work up, convenient and steady reuse and high activity and selectivity are prominent properties of this new hybrid material.

Full text of DOI:10.1002/aoc.5225

Received: 5 February 2019
DOI: 10.1002/aoc.5225
Revised: 12 August 2019
Accepted: 12 August 2019
F U L L P A P E R
Molybdenum (VI)‐functionalized UiO‐66 provides an
efficient heterogeneous nanocatalyst in oxidation reactions
1
1
1,2
Niloufar Afzali | Reihaneh Kardanpour | Farnaz Zadehahmadi
|
1
1
1
Shahram Tangestaninejad
| Majid Moghadam
| Valiollah Mirkhani |
2
1
1
Adam Mechler | Iraj Mohammadpoor‐Baltork
| Mehrnaz Bahadori
1
Department of Chemistry, Catalysis
A novel heterogeneous nanocatalyst was established by supporting molybde-
Division, University of Isfahan, Isfahan
8
2
1746‐73441, Iran
num (VI) on Zr nodes in the structure of the well‐known UiO‐66 metal–
6
La Trobe Institute for Molecular
organic framework (MOF). The structure of the UiO‐66 before and after Mo
Sciences, La Trobe University, Bundoora,
VIC 3086, Australia
(VI) immobilization was confirmed with XRD, DR‐FTIR and UV–vis spectros-
copy, and the presence and amount of Mo (VI) was identified by X‐ray photo-
electron spectroscopy and inductively coupled plasma atomic emission
spectroscopy. TEM imaging confirmed the absence of Mo clusters on the
MOF surface, while SEM confirmed that the appearance of the MOF has not
changed upon immobilizing the Mo (VI) catalyst. BET adsorption measure-
ments were used to confirm the porosity of the catalyst. The catalytic activity
of this heterogeneous catalyst was investigated in oxidation of sulfides with
H O in acetonitrile and oxidative desulfurization of dibenzothiophene. Easy
Correspondence
Shahram Tangestaninejad, Majid
Moghadam and Valiollah Mirkhani,
Department of Chemistry, Catalysis
Division, University of Isfahan, Isfahan
81746‐73441, Iran.
Email: stanges@sci.ui.ac.ir;
moghadamm@sci.ui.ac.ir; mirkhani@sci.
ui.ac.ir
2
2
work up, convenient and steady reuse and high activity and selectivity are
prominent properties of this new hybrid material.
KEYWORDS
Dibenzothiophene, heterogeneous catalyst, metal–organic frameworks, oxidation reaction, UiO‐66
1
| INTRODUCTION
Approximately nine out of ten industrial chemical pro-
cesses use heterogeneous catalysts, prompting an ongoing
Metal–organic frameworks (MOFs) are open porous
three‐dimensional architectures composed of inorganic
building blocks and organic ligands that provide a new
world of possibilities for the synthesis of a great variety
of materials with specific chemical composition, structure
interest in the synthesis of new supported catalysts with a
[29]
potential for direct impact on the global economy.
recent years the catalytic activity of early transition metal
complexes, especially molybdenum complexes
In
(oxomolybdenum species) attracted intense attention
[1–9]
[30–32]
and geometrical properties.
Due to their high effective
due to their high catalytic activity and selectivity.
surface area and tuneability together with thermal and
These complexes were also immobilized in different
[10,11]
chemical stability,
they are well suited for a broad
organic and inorganic materials to solve the problems of
[12]
[33,34]
range of applications including ion‐exchange,
non‐
gas separation or stor-
and as support platform for heterogenization
catalyst separation and reusability.
Improvements
[
13–15]
[16]
linear optics,
sensors,
in the efficiency of such heterogenized catalysts requires
large surface areas, turning the focus of development
toward nano‐supports such as MOFs due to their high
[
17–23]
age
of homogeneous catalysts.
[
24–28]
Appl Organometal Chem. 2019;e5225.
wileyonlinelibrary.com/journal/aoc
© 2019 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.5225

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AFZALI ET AL.
surface area and uniform pores with molecular dimen-
node modification pathway (Scheme 1). In this manner,
the UiO‐66 was first synthesized by ultrasonic method
reported by Hupp et al., which allows us to form the frame-
[35–39]
sions.
Thus, novel MOF‐based heterogenized cata-
[
40]
lysts are actively sought for industrial applications.
[
49]
The Zr‐based UiO‐66 (UiO = University of Oslo), first
reported by Lillerud et al., is composed of 12‐coordinate
Zr(O) (OH) nodes, each linked to 12 carboxylates of tere-
work in large scale.
Then the molybdenum acetyl
acetonate complex was reacted with the node of UiO‐66
and the resulting heterogeneous nanomaterial was fully
characterized. The catalytic activity of the prepared hetero-
geneous catalyst was investigated in oxidation of sulfides
and oxidative desulfurization of dibenzothiophene
(Scheme 2).
4
4
phthalate ligands to form super tetrahedral and super
octahedral cages with apertures of approximately
[41]
6
Å.
This MOF is known to have an exceptional ther-
mal (up to ∼540 °C) and mechanical stability and is sta-
ble to water and many organic solvents with uniform
pores that in turn make it an excellent candidate for use
as a support for catalytic complexes. Additionally, this
MOF is attractive for oxidation reactions due to its stabil-
2 | EXPERIMENTAL
2.1 | Characterization
[
42]
ity in the presence of hydrogen peroxide oxidant.
There is a common route for the immobilization of
metal complexes onto UiO‐66 by post‐synthetic modifica-
tion of the organic linker; as we reported previously, the
immobilization of molybdenyl acetylacetonate onto UiO‐
All reagents were purchased at ACS reagent grade. Dif-
fuse reflectance spectra of the samples were recorded
with a solid UV–vis JASCO V‐670 spectrophotometer.
DR‐FTIR spectra of the materials in potassium bromide
6
6‐NH yielded an efficient catalyst for the epoxidation of
2
[43]
alkenes with TBHP.
Other authors reported molybde-
−
1
num complex immobilized on amino‐functionalized
UiO‐66 and ‐67 post‐synthetically modified with
pellets were obtained in the range 400–4000 cm by a
JASCO 6300D instrument. The surface area, pore volume
and pore size distribution of the support and the catalyst
[44]
salicylaldehyde. However, there is another route, which
involves the –OH groups on the Zr node of UiO‐66 frame-
work. Laribi et al. have reported the immobilization of
Au(I) phosphine species onto the cornerstone of UiO‐67,
were determined by adsorption–desorption of N gas at
2
77 K using ASAP 2000 Micrometrics instrument after
activation of about 70 mg sample at 120 °C for 8 h. BET
[
45]
an isostructural analogue of UiO‐66 and UiO‐68.
II) and Al (III) were supported into the −OH groups on
the nodes of the Zr‐based clusters in the NU‐ 1000 MOF
Zn
surface area was determined at the range P/P = 0.005–
0
(
0.05 and the pore size distribution curves were calculated
by the BJH equation.
X‐ray diffraction (XRD) patterns were recorded with a
D Advanced Bruker instrument using Cu Kα radiation
8
[
46]
platform by atomic layer deposition.
More recently, Zr
v.[47]
nodes of UiO‐66 were metallated with V
UiO‐66 (and
NU‐1000) were also used as supports for Ir (CO) and
source (λ = 1.5406 Å). The ICP measurements were car-
ried out using a Perkin‐Elmer Optima 7300 DV spectrom-
eter. Conversions and yields of the products were
measured by GC‐FID on a Shimadzu GC‐16A instrument
using a 2 m column packed with silicon DC‐200 or
Carbowax 20 m column using toluene as the internal
standard. The particle size and microscopic morphologi-
cal features of the samples were obtained on a Hitachi
S‐4700 field emission scanning electron microscope (FE‐
SEM). X‐ray photo‐electron spectroscopy (XPS) measure-
ments were performed using a Gammadata‐Scienta
ESCA200 hemispherical analyser equipped with an Al
2
[48]
Ir(C H ) complexes.
Given that Zr nodes of UiO‐66
2
4 2
6
are ideal for supporting metal complexes, and that previ-
ous reports identified molybdenum oxides as a highly effi-
cient catalyst for oxidation reactions, we attempted to
synthesis molybdenum‐functionalized UiO‐66 via the
(
K α = 1486.6 eV) X‐ray source. Transmission electron
microscopy (TEM) was carried out on a Philips CM10
1
instrument operating at 100 kV. The H NMR spectra
were recorded on a Bruker Avance AQS 400 MHz NMR
1
spectrometer. H chemical shifts are reported in ppm
from TMS with the residual solvent resonances as inter-
nal standards; for the measurements ~2–5 mg of the
materials were dissolved in 1:10 v/v ratio of conc.
SCHEME 1 Molybdenum complex immobilized at the nodes of
Zr‐based MOF
6
D SO /DMSO‐d .
2
4

AFZALI ET AL.
3 of 11
SCHEME 2 Sulfide oxidation and
oxidative desulfurization of
dibenzothiophene in the presence of
H2O2 and acetic acid catalyzed by
MoUiO‐66
2.2 | Synthesis of MoUiO‐66 catalyst
and the yield of products was determined by GC analysis
using toluene as the internal standard. Finally, the cata-
The UiO‐66 metal organic framework was prepared based
lyst was filtered and thoroughly washed with Et O
2
[49]
on the procedure reported by Hupp et al..
The most
(3 × 3 mL), and the organic phase was extracted followed
by evaporation of solvent. Higher purification of products
was achieved by silica gel plates (eluent: n‐hexane/ethyl
acetate 70:30 for sulfone isolation).
important aspect of this procedure is the possibility of
large‐scale synthesis; here with 4 grams of ZrCl 7 grams
4
of UiO‐66 was produced. MoO (acac) was synthesized
2
2
[
50]
according to the published procedure.
A solution of
MoO (acac) (100 mg) in MeOH (8 ml) was prepared.
2
2
Activated UiO‐66 (400 mg) was added to this solution
and the mixture was heated at 70 °C for 48 hr in an oil
bath. The resulting white precipitate was filtrated and dis-
persed in MeOH (~ 10 ml) at 70 °C for 24 hr. After two
cycles of washing with methanol, the material was fil-
tered and dried at 50 °C for 24 hr. It was necessary to acti-
vate the catalyst before each reaction at 150 °C for 24 hr.
2.3.2 | General procedure for the oxidative
desulfurization of dibenzothiophene
All of the experiments were carried out in an Erlenmeyer
flask (50 ml) at atmospheric pressure under magnetic
stirring. The model oils were prepared by dissolution of
DBT in n‐heptane (approximately 500 ppm or 0.0156
−
3
mol dm ). Initially, 100 mg of the catalyst was added
to 5 ml MeCN and afterwards 5 mL of the model oil
was added. The biphasic system was stirred for 10 min
and DBT was transferred from the oil to the extracting
2
2
.3 | Catalytic experiments
.3.1 | General procedure for the oxida-
phase. After that, 0.1 ml H O and 1 mmol acetic acid
2 2
tion of sulfides
was added to the system to initiate catalytic oxidation of
the sulfur compounds present in the extractant. At the
end of reaction, the resulted mixtures were transferred
to a separation funnel (50 ml). The MeCN phase was sep-
arated and the catalyst was removed by filtration. The
progress of reaction was monitored by TLC, and the yield
of products was determined by GC analysis using toluene
Methyl phenyl sulfide (1 mmol), H O 30% (2 mmol), ace-
2
2
tonitrile (3 ml) and MoUiO‐66 (100 mg, 0.036 mmol
molybdenum) were mixed in a round‐bottomed flask.
The reaction mixture was stirred at room temperature.
The progress of the reaction was monitored by TLC,

4
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AFZALI ET AL.
[
49]
as the internal standard. In order to investigate the effect
of catalyst the reference reactions were performed with
DBT and it was confirmed that no oxidation occurred in
the absence of the catalyst.
1,4‐ benzenedicarboxylate (BDC).
ICP analysis
revealed that the amount of Mo in the prepared catalyst
(MoUiO‐66) was about 0.36 mmol/g. The structure of
the MoUiO‐66 catalyst was characterized by XRD analy-
sis. Sharp peaks indicated the excellent crystallinity of
the framework. After adding the Mo complex, the basic
lattice structure of UiO‐66 was well maintained
2.3.3 | Cyclic test
(
Figure 1).
The reusability of the MoUiO‐66 catalyst was investigated
in multiple sequential oxidation of methyl phenyl sulfide
as described above. In this way, at the end of the reac-
The FE‐SEM images in Figure 2 clearly show that the
morphology of the UiO‐66 was unaffected by the modifi-
cation of the framework. The diameters of the small
cubic intergrown crystals of UiO‐66 are in the range of
tions the catalyst was filtered, washed with Et O, dried
2
at 80 °C and reused. The amount of Mo leaching was
determined by ICP. The catalyst stability was followed
by XRD (Figure 1).
8
0 to 110 nm. Energy dispersive X‐ray (EDX) results
clearly show the presence of Zr and Mo (Figure 3A).
The elemental mapping analysis confirmed even distri-
bution of Mo in the UiO‐66 (Figure 3B). According to
TEM images there are not any molybdenum nano‐
particles on the surface of the UiO‐66 framework, hence
the amount of Mo (VI) content measured with ICP, and
all of the consecutively measured catalytic activity was
due to the immobilized Mo (VI) within the framework
(Figure 4).
3
3
| RESULTS AND DISCUSSION
.1 | Synthesis of MoUiO‐66
The UiO‐66 was synthesized under ultrasonic conditions
by combining HCl and equimolar amounts of ZrCl and
4
FIGURE 1 PXRD patterns of UiO‐66,
MoUiO‐66 and recovered catalyst
FIGURE 2 FE‐SEM images of (a) UiO‐66, (b) MoUiO‐66 and (c) histogram of particle distribution

AFZALI ET AL.
5 of 11
FIGURE 3 SEM–EDX mapping of the hybrid material MoUiO‐66
FIGURE 4 TEM images of (a) UiO‐66 and (b) MoUiO‐66
The effective surfaces and porosity of both the UiO‐66
and the catalyst were determined using nitrogen
physisorption measurements (Figure 5) and the textural
parameters are presented in Table 1. The similarities of
the surface areas are predictable because only the corner
hydroxyl groups of UiO‐66 were replaced by Mo (VI) moi-
[
47]
eties (Figure 5 A, B).
In addition, there is very little
decrease in pore volume compared to UiO‐66 (Table 1).
The pore size distribution curves (calculated by the BJH
equation) show that there was no observable change in
FIGURE 5 (a) Representative N2 isotherms for UiO‐66 and MoUiO‐66, and (b) Pore‐size distributions for UiO‐66 and MoUiO‐66

6
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AFZALI ET AL.
[
51]
TABLE 1 BET and ICP results of UiO‐66 and the MoUiO‐66
experimentally.
As shown in Figure 6, The replace-
catalyst
ment of the OH groups with molybdenum was apparent
−
1
in the little reduced intensity at 3651 cm
and
S
BET
2
Total pore Volume
ICP (Mo
mmol g )
−
1
−1
3
−1
−1
3700 cm
corresponding to missing‐linker OH sites.
Samples
(m g
)
(cm g
)
−
1
The intensity of sharp hydroxyl peak at 3671 cm , attrib-
utable to the bridging −OH group on the node is almost
the same for both UiO‐66 and MoUiO‐66. Therefor these
data supported the hypothesis that the −OH groups at
missing‐linker sites could form and react with the Mo
UiO‐66
1211.4
1113.9
0.41
0.42
‐
MoUiO‐66
0. 36
porosity upon modification of UiO‐66 with molybdenum
complex (Figure 4b).
(acac) reagent, although we cannot rule out the possibil-
2
ity that some bridging hydroxyl groups on the nodes of
[
47,48,52]
The vibrational spectra of UiO‐66 and MoUiO‐66 are
UiO‐66 also reacted with MoO (acac)
2
2.
−
1
1
summarized in Figure 6. The band at 1667 cm in the
H NMR analysis of the metallated MOF dissolved in
framework modes is ascribed to residual DMF. The
intense doublet at 1589 and 1395 cm is assigned to
the stretching modes of the carboxylate group.
D SO4 show that the acac ligand was not present
(Figure 7). Therefore, the Mo reagent has reacted with
2
−
1
the −OH groups that were present on.
[
46]
UiO‐66 has been reported to have terminal −OH
groups that are present at the missing‐linker sites of the
the Zr nodes.
The Raman spectrum of the MoUiO‐
−
1
66 catalyst does not show the band at 922 cm for the
terminal M = O stretch in MoO (acac) , neither does it
[49]
nodes.
These defects can arise from one or more miss-
2
2
ing linkers and other building units, and their nature and
spatial distribution are difficult to characterize
show any band that can be attributed to M = O species,
it is due to low Mo loading or the presence of adsorbed
FIGURE 6 DR‐FTIR spectra of UiO‐66
and MoUiO‐66

AFZALI ET AL.
7 of 11
peaks of other oxidation states of molybdenum were not
observed, confirming that Mo is in the VI oxidation state.
The peaks corresponding to oxygen, carbon, nitrogen, zir-
conium and molybdenum are also clearly observed in
XPS elemental maapping of the catalyst (Figure 9b).
Diffuse‐reflectance UV–vis spectra of MoUiO‐66 (red
solid line) and UiO‐66 (blue solid line) are shown in
Figure 10. An extra shoulder around 300–400 nm is
attributed to the Mo VI species in the catalyst
[
47,55]
(
Figure 9).
3
.2 | Investigation of catalytic properties
FIGURE 7 1H NMR spectra of UiO‐66 and MoUiO‐66
of MoUiO‐66
3.2.1 | Oxidation of sulfides
The catalytic potential of the MoUiO‐66 catalyst in the oxi-
dation of sulfides was investigated. To determine the best
reaction conditions, factors such as the nature of solvent,
the amount of catalyst, and the kind and amount of
FIGURE 8 Raman spectra of MoUiO‐66, MoO2 (acac)2 and 1%
MoO2(acac)2/UiO‐66 mix (physical mixture)
[47,53]
water (Figure 8).
In the X‐ray photoelectron spec-
troscopy (XPS) of MoUiO‐66, the 3d5/2 and 3d3/2 peaks
of the Mo (VI) appear at 233.05 and 235.52 eV, respec-
tively (Figure 9). Due to the interaction between the Zr
[54]
and Mo, these peaks appear at higher energy.
The
FIGURE 10 UV–vis spectra of UiO‐66 and MoUiO‐66
FIGURE 9 The XPS spectra of (a) MoUiO‐66 showing Mo 3d5/2 and Mo 3d3/2 binding energies, (b) the elemental survey scan of MoUiO‐
6
6

8
of 11
AFZALI ET AL.
oxidant in the oxidation of methyl phenyl sulfide into the
corresponding sulfone and/or sulfoxide was studied. In
our catalytic system, sulfone was the main product and
sulfoxide produced in low yields. Therefore, we concen-
trated to find the best conditions for producing the sulfone.
In the oxidation of sulfides, the selection of solvent is
crucial for achieving maximum amount of product. It
was observed that acetonitrile afforded the highest yield
produced only 17% sulfone after 1 hr suggesting that the
Zr node might have some, albeit minimal, oxidation
activity. Nevertheless, the higher TON for Mo‐UiO‐66
confirms that Mo (VI) ions are responsible for the cata-
lytic activity.
As shown in Table 2, various types of sulfides, includ-
ing diaryl, aryl benzyl, dialkyl, cyclic and unsaturated sul-
fides were converted to their corresponding sulfone with
high conversions and short reaction times in the presence
of MoUiO‐66. As shown in Table 2, by increasing the
chain length of the substrates the rate of reaction
decreased, which may be explained with steric hindrance.
The oxidation of dibezothiophene (DBT), which is a less
nucleophilic sulfide, is a very important reaction in oxida-
tive desulfurization of diesel oils. The catalyst could
effectively oxidize this sulfide to its corresponding sulfone
in the presence of the catalyst (Table 2, entry 9). There-
fore, the oxidative removal of this compound was chosen
as the model reaction in a biphasic system.
(Figure S1). The efficiency of different oxygen donors such
as TBHP, NaIO , Na SO and H O was also investigated.
4
2
5
2 2
As shown in Figure S2, H O was the best oxygen source.
2
2
Hydrogen peroxide is considered as an ideal “green” oxi-
dant because it is environmentally benign, cheap, easy to
[56]
handle and does not form toxic by‐products.
In the next step, the oxidation of methyl phenyl sulfide
in acetonitrile with different amount of H O 30% was
2
2
investigated and 2 mmol of H O 30% was found to be
2
2
the best amount for higher yields of sulfone (Figure S3).
The effect of catalyst amount on the oxidation of methyl
phenyl sulfide was investigated by using different
amounts of MoUiO‐66 in acetonitrile at room tempera-
ture (Figure S4). The best result was obtained with
3.2.2 | Oxidative desulfurization of
dibenzothiophene
1
00 mg of the catalyst. A blank experiment was also car-
ried out under the same conditions in the absence of the
catalyst, and the corresponding sulfone was produced in
ODS process is regarded as one of the most promising
5
% yield. Interestingly control experiments with UiO‐66
processes for high S‐removal from diesel oils and gasoline
a
TABLE 2 Oxidation of various sulfides to the corresponding sulfone by using 30% aqueous H
2
O
2
catalyzed by MoUiO‐66
b
c
−1 d
Entry
Alkene
Product
Time (min)
Selectivity (%)
Conversion (%)
TOF (h )
1
10
97
98
163.33
2
3
4
5
6
14
25
17
13
35
96
96
95
95
96
98
97
96
97
97
116.7
64.7
94.11
124.3
46.2
7
30
93
95
52.8
8
9
18
50
94
92
98
95
90.7
32.7
a
2 2
Reaction conditions: methyl phenyl sulfide (1 mmol), H O (2 mmol), catalyst (0.1 g, 0.036 mmol Mo) and solvent (3 ml) at room temperature.
b
c
The by‐products were sulfoxide.
GC yield based on starting sulfide.
d
TOF calculated as the amount of reactant (moles) divided by amount of catalyst (moles).

AFZALI ET AL.
9 of 11
due to its mild operating conditions, and simple, safe,
catalyst was confirmed by XRD analysis. As shown in
Figure 1, the basic lattice structure of UiO‐66 was not
altered after four cycles.
[57]
reproducible, and eco‐friendly post‐treatment.
Because
of the difficulties of the oxidation of heterocyclic sulfur‐
containing compounds such as dibenzothiophene (DBT),
oxidative removal of DBT is regularly studied as the
4
| CONCLUSION
[58]
model organic sulfur compound in petroleum.
For this
purpose, we used MoUiO‐66 catalyst, H O2 30% as
2
A novel MOF‐based catalyst was designed by using a new
type of post‐synthetic modification of UiO‐66. In this way,
the corner hydroxyl groups of the UiO‐66 framework
were used as grafting sites to form a robust MoUiO‐66
catalyst. The UiO‐66 metal–organic framework was syn-
thesized by ultrasonic method, which allows the produc-
tion of the framework in large scale. The MoUiO‐66
catalyst showed excellent activity in oxidation of sulfides
and oxidative desulfurization of dibenzothiophene. This
new catalyst afforded excellent activity in oxidation reac-
tions. Easy work up and mild reaction conditions are
other advantages of this hybrid material.
oxidant, acetic acid as promoter, a model oil of DBT in
n‐heptane and acetonitrile as an immiscible extracting
solvent (Scheme 2).
In order to investigate the effect of different factors on
the desulfurization system, the oxidation of DBT in the
model fuel was conducted. For this purpose, parameters
such as amount of aqueous H O 30% (1, 1.5, 2 and
2
2
3
2
mmol) and amount of catalyst (50, 100, 150 and
00 mg) were evaluated and the best performance was
achieved using 2 mmol aqueous H O 30% and 100 mg
2
2
catalyst (Figure S5 and S6).
Different acids such as formic acid, hydrochloric acid,
oxalic acid, acetic acid and sulfuric acid were tested as
promoters to acidify the system. From the results in
Figure S7, inorganic acids (H SO and HCl), produced
ACKNOWLEDGEMENT
2
4
We are grateful to the Iranian National Science Founda-
tion (INSF) project number 96003992 and the Research
Council of the University of Isfahan project number
lower sulfone yield compared organic ones. By increas-
ing the acetic acid amounts, sulfur removal also
increases (Figure S8). This can be explained with the
activation of H O bonds by acetic acid for producing
1023 for financial support of this work.
2
2
[59,60]
active oxygen species.
According to these results,
1
mmol acetic acid (100% conversion of DBT) was the
ORCID
optimum. Higher amounts of acetic acid could damage
the catalyst.
Shahram Tangestaninejad
https://orcid.org/0000-0001-
5263-9795
Finally in a 210‐min ODS reaction of DBT at 25 °C,
with hydrogen peroxide as the oxidant and acetic acid
as a promoter, high DBT conversion of 100% was
observed and DBT was converted to DBT sulfone. DBT
sulfone was the only product in all of the catalytic exper-
iments and no sulfoxide was observed.
Majid Moghadam https://orcid.org/0000-0001-8984-1225
Iraj Mohammadpoor‐Baltork https://orcid.org/0000-0001-
7998-5401
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[
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[
[
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