Copper phthalocyanine as an efficient and reusable heterogeneous catalyst for direct hydroxylation of benzene to phenol under mild conditions

Article abstract of DOI:10.1016/j.ica.2018.08.051

The liquid-phase oxidation of benzene to phenol over copper phthalocyanine as a heterogeneous catalyst was studied at room temperature. Acetonitrile was chosen as the preferred solvent and hydrogen peroxide as an eco-friendly oxidant. The yield and selectivity of 13.9% and 100% were obtained, respectively. The catalyst was characterized by FT-IR, UV-Vis, XRD, TGA, XPS, ¹H NMR, ¹³C NMR, CHN, BET, FE-SEM, TEM, and EDX analysis. The effects of different parameters on the catalytic performance of CuPc were also investigated. The reusability of the catalyst was studied, and the results showed that after five cycles the yield of phenol did not change noticeably, probably due to its stability in the reaction conditions.

Full text of DOI:10.1016/j.ica.2018.08.051

Accepted Manuscript
Copper phthalocyanine as an efficient and reusable heterogeneous catalyst for
direct hydroxylation of benzene to phenol under mild conditions
Shohreh Farahmand, Mehran Ghiaci, Jala.S. Razavizadeh
PII:
S0020-1693(18)30999-X
https://doi.org/10.1016/j.ica.2018.08.051
ICA 18451
DOI:
Reference:
To appear in:
Inorganica Chimica Acta
Received Date:
Revised Date:
Accepted Date:
29 June 2018
25 August 2018
27 August 2018
Please cite this article as: S. Farahmand, M. Ghiaci, Jala.S. Razavizadeh, Copper phthalocyanine as an efficient and
reusable heterogeneous catalyst for direct hydroxylation of benzene to phenol under mild conditions, Inorganica
Chimica Acta (2018), doi: https://doi.org/10.1016/j.ica.2018.08.051
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Copper phthalocyanine as an efficient and reusable heterogeneous catalyst for
direct hydroxylation of benzene to phenol under mild conditions
a
a
a
Shohreh Farahmand , Mehran Ghiaci , Jala. S. Razavizadeh
Abstract
The liquid-phase oxidation of benzene to phenol over copper phthalocyanine as a
heterogeneous catalyst was studied at room temperature. Acetonitrile was chosen as the preferred
solvent and hydrogen peroxide as an eco-friendly oxidant. The yield and selectivity of 13.9% and
1
00% were obtained, respectively. The catalyst was characterized by FT-IR, UV-Vis, XRD,
1
13
TGA, XPS, H NMR, C NMR, CHN, BET, FE-SEM, TEM and EDX analysis. The effect of
different parameters on the catalytic performance of CuPc were also investigated. The reusability
of the catalyst was studied, and the results showed that after five cycles the yield of phenol did
not change noticeably, probably due to its stability in the reaction conditions.
Keywords: Copper phthalocyanine; benzene; hydroxylation; phenol; hydrogen peroxide.
1. Introduction
Among the most important raw materials, phenol is a valuable intermediate that has many
applications and is widely used for the synthesis of bisphenol-A, phenolic and epoxy resins,
polycarbonates, agrochemicals, plastics, and pigments [1–3]. Its current production worldwide
might be around 10 million tons per year where a large fraction of it is produced by the cumene
process [4]. In this process, cumene is partially oxidized when phenol and acetone are produced
in a 1:1 molar ratio via the Hock rearrangement [5], but this process has several disadvantages
such as high energy consumption, low yield of phenol, production of by-product and
environmental problems. Therefore as a chemical industry perspective, the goal will be to
produce phenol using an eco-friendly oxidant such as molecular oxygen [6], or hydrogen
peroxide [7].
a
Department of Chemistry, Isfahan University of Technology, Isfahan, Iran
Corresponding author. Tel.: +98 311 391 3254; fax: +98 311 391 2350; P. O. Box. 8415683111
*
E-mail address: mghiaci@cc.iut.ac.ir (M. Ghiaci).
1

Moreover, the direct hydroxylation of benzene to phenol has been affected by low
benzene conversion and poor selectivity, because of activity of phenol which tolerates over-
oxidation [4]. However, from the economic point of view, it seems that energy consumption is
much lower compared to the cumene process. As a general statement, it should be mentioned
that there are two main routes for the direct production of phenol from benzene, i.e. gas-phase or
liquid phase [8,9]. The liquid phase oxidation of benzene with H
2
2
O has been extensively
investigated as an eco-friendly process but production of substantial over-oxidation by-products
such as hydroquinone, catechol, resorcinol, and benzoquinone decreases the selectivity of the
reaction [4]. The catalysts such as Ti/MCM-41 [10], TS-1 [11], modified titanium silicate [12],
VOx on different supports [13–15], CuCr
2
4
O spinal nanoparticles [16] have been used in liquid
phase oxidation of benzene in solvents like acetonitrile [17] or acetic acid [18] where the yield of
phenol reported in these works has been in the range of 10-43%. Therefore introducing new
efficient catalysts that can carry out the hydroxylation of benzene to phenol with high yield and
selectivity is a fundamental issue.
Herein we have introduced copper phthalocyanine (CuPc) as a probably cheap and
appropriate catalyst for direct hydroxylation of benzene using hydrogen peroxide at room
temperature condition. Metalphthalocyanines (MPcs) with 18-electron aromatic system are
heterocyclic molecules similar to porphyrin systems. MPcs have four isoindole (pyrrol) units
linked by aza nitrogen atoms, and can be converted into different complexes with various metals,
chiefly transition metals. These important Schiff bases have been used as an efficient and
reusable catalysts in many organic reactions [19–26]. These macrocycles have prominent
properties such as high thermal and chemical stability, poor solubility in common organic
solvents, light absorption capability and photo-catalytic reactivity [20].
Un-substituted phthalocyanines are insoluble in common solvents such as acetonitrile,
acetone and water because of interaction between their conjugated π-system [27]. Therefore we
expected that CuPc could be used as an easy-to-use heterogeneous catalyst in common organic
solvents. On the other hand, the catalytic properties of MPcs depend on the metal atom, and
different metals are used as a coordinated atom in this macrocycle where the properties of the
complex vary by changing the metal. It is worth noting that benzene hydroxylation to phenol has
been carried out by using various catalysts based on copper [17]. In this study, we attempted to
2

perform hydroxylation of benzene over the copper phthalocyanine as a heterogeneous catalyst
using hydrogen peroxide as an efficient oxidant at room temperature.
2. Experimental Section
2
.1 Materials
Urea, phthalic anhydride, copper (II) chloride, ammonium molybdate, benzene and 35 wt.
were of analytical grade. Purity of benzene was checked by using GC before of the
%
H
2
O
2
reaction.
2
.2 Characterization techniques
Fourier transform infrared spectra of the samples were recorded on a JASCO FT-IR 680
plus spectrometer using the KBr pellet and the spectra were obtained in the range of 400-4000
-1
-1
cm with a resolution of 4 cm and an average of 64 scans. The Yield of the products were
determined by BEIFEN 3420 gas chromatograph equipped with a FID detector using internal
standard (Acetophenone). The column was a 30 m HP-FFAP with 0.32 mm i.d. and 0.5-m film
thickness. The initial temperature was 50 °C for 1 min. Then ramped at 15 °C/min to 100 °C and
hold for 1min and then with a rate of 10 °C/min to 200 °C. The products of the hydroxylation of
benzene were confirmed by GC/MS (GC 7890A and mass 5975C/ Agilent-USA).
The X-ray diffraction (XRD) pattern was recorded at room temperature using Philips (X'pert,
Japan) apparatus with a nickel filtered CuKα radiation, generated at 10 mA and 40 kV and, TG
analysis was performed by using Q-600 (TA Company, USA) machine. Also Field Emission
Scanning Electron Microscopy (FE-SEM) analysis was done using MIRA3 and Energy-
dispersive X-ray spectroscopy (EDX) using SAMX (France) device. Transmission electron
TM
microscopic (TEM) analysis was made using a FEI TECNAI G2, (USA). The diffuse
reflectance UV/Vis spectra were taken on a V-670 apparatus. X-ray photoelectron spectroscopy
(
XPS) analysis was carried out using PHI 5000 Versa Prob II, FEI USA. The actual metallic
elements content were determined by inductively coupled plasma-optical emission spectroscopy
1
13
(
ICP-OES) by a Varian Vista-PRO CCD simultaneous ICP-OES. H-NMR (400 MHz) and C-
NMR (125 MHz) were performed in DMSO-d on a Bruker Avance spectrometer. Mass
6
analysis was performed using the Agilent apparatus (Mass model: 5973). Surface area and
pore size distribution were measured on a Micromeritics PHS-1020 (PHSCHINA) system
3

at 77 K using N as the adsorbate. Before the measurements, the samples were degassed at
2
1
20 °C.
.3 Preparation of the catalyst
2
CuPc was synthesized based on the reported procedure by Shaabani [28] as a following: In a 500
mL beaker, Phthalic anhydride (2.65 g), urea (95.54 g), copper chloride (0.5 g) and ammonium
molybdate (0.075 g) were ground together until a homogeneous mixture was obtained. Then it
irradiated in a microwave oven at high power. After 6 min irradiation was stopped and product
washed by using 5% caustic soda, water and 2% hydrochloric acid respectively. After drying in
oven, a blue solid was obtained which it was named as CuPc briefly (Scheme 1). Anal. Calcd
for C32
H
16CuN : C 66.4, H 2.77, N 19.4%. Found: C 66.4, H 2.75, N 19.7%. The structure
8
1
13
and the purity of the CuPc, and phthalocyanine ligand were identified by H NMR, C
NMR analysis (Figs S1-S2).
Scheme 1. Synthesis of CuPc
2
.4 Typical procedure for hydroxylation of benzene
Direct hydroxylation of benzene to phenol by using 35wt% H
2
O
2
was carried out as
follows: A mixture of benzene (1 mL), CuPc (40 mg) and 35wt% H
2
O
2
(3 mL) were stirred at
room temperature for 15 h. At the end of the reaction, the catalyst was separated using
centrifugation (10 min, 7000 rpm) and the mixture of reaction was diluted using ethanol and
injected to GC without any purification. Qualitative analysis was carried out with a HP-FFAP
GC. Quantitative analysis was carried out using an Agilent 7890A GC and Agilent 5975C MS
4

with BP20 column from SGE Company. GC of mixture of reaction and GC-MS of products are
shown in Figs. S3-S6.
3.
Result and discussion
3
.1 Characterization of the catalyst
3
.1.1. FT-IR spectrum
The FT-IR spectrum of CuPc is shown in Fig. 1. In this spectrum, the C=N and C=C
-1
-1
vibrations were appeared at the 1620 cm and 1508 cm , respectively. The C-N and C-C
-
1
-1
stretching of isoindole appeared at 1332 cm and 1119 cm , respectively. Also, the peaks in the
-1
-1
range of 1600-1470 cm were related to breathing vibrations of the aromatic rings, 1089 cm is
-
1
due to C-H in plan deformation and 728 cm is for C-H out of plane deformation of phenyl ring
29].
[
Fig. 1. FT-IR spectrum of CuPc
3
.1.2. UV-Vis spectra
In addition, UV-Vis spectra of fresh and reused CuPc catalysts are shown in Fig. 2 and
the results verify the stability of the catalyst during the reaction. In these spectra there is a strong
absorption peak around 650 nm that it refers to Q-band which is characteristic of all matallo-

phthalocyanines and it is related to the a1u(π) →e
g
(π ) transition [30]. Clearly, the position of the
5

Q band is affected by various parameters like symmetry, central metal, etc. Also, it should be
mentioned that non-metallated phthalocyanines display a split Q band, but the CuPc has shown a
single Q band [31,32].
Fig. 2. UV-Vis spectra of fresh and reused CuPc
3
.1.3. XPS studies
The XPS analysis of CuPc at whole scanning (Fig. 3a) shows four clear and strong peaks
where located at about 936.30, 533.30, 399.30 and 286.30 eV, that correspond to Cu 2p, O 1s, N
s and C 1s respectively. Fig. 3b shows the XPS result of C 1s which includes two peaks; one is
1
located at 284.9 eV and another at 286.3 eV that these refer to the aromatic carbons and carbon
atoms in C-N bonds, respectively. Fig. 3c shows the XPS spectrum at the N 1s region where in
this spectrum three peaks appear, one is located at 399.2 eV which is referred to the binding
energy of the nitrogen atom in C-N=C and the peaks appeared in the range of 401.1-405.2 eV
can be related to the binding energy of nitrogens which are coordinated to copper [33], and O 1s
binding energies at 532.6 eV and 538. eV belong to the chemisorbed water from
atmosphere [34]. Fig. 3d shows the XPS results at the copper region, where in this spectrum two
strong peaks located at 935.6 eV and 955.6 eV correspond to the electron state of Cu 2p1/2 and
Cu 2p3/2, respectively which demonstrate the existence of Cu(II) in the CuPc complex [35,36].
6

Fig. 3. XPS analysis at the whole scanning (a), C 1s (b), N 1s (c), Cu 2p (d), and O 1s (e) region
of CuPc
3
.1.5. Morphological features (FE-SEM, TEM images and EDX analysis)
The FE-SEM images of the fresh (Fig. 4a) and reused catalyst (Fig. 4b) were obtained to
demonstrate the morphology of the fresh catalyst and after five cycles. The images show uniform
aggregates of small plane crystalline particles with a porous structure. For obtaining evidence for
7

the presence of copper in the fresh and reused catalysts the energy-dispersive analysis (EDX)
was used, and the results are shown in the Fig. 4a-b. The quantitative analysis of the elements
showed that 1.07 wt% Cu exists in the fresh and reused catalysts. Also, the TEM images of the
fresh (Fig. 4c) and reused catalysts (Fig. 4d) show the nano-crystalline particles of the CuPc
which are formed through stacking of their π-systems for creating a strong and hydrophobic
crystal lattice. TEM images verify this subject that the catalyst had no significant changes during
the 5 runs of the reactions.
Fig. 4. FE-SEM, EDX and TEM of fresh (a and c) and reused (b and d) of CuPc
8

3
.1.6. N sorption study
2
Nitrogen adsorption-desorption isotherm of the CuPc catalyst is demonstrated in Fig. 5.
According to IUPAC classification the CuPc has presented a typical Type II with H3
hysteresis loop. The specific surface area, pore volume, and BJH desorption average pore
2
-1
3 -1
diameter of the catalyst were 31 m .g , 1.029 cm g , and 18.4 nm, respectively. Even by
having a relatively low surface area, oxidation activity of the CuPc was very well probably
because of having hydrophilic and hydrophobic sites for conducting the substrates to the
active sites of the catalyst.
Fig. 5. Adsorption/desorption isotherm of CuPc
3
.1.7. TGA and XRD patterns
Thermal Gravimetric Analysis (TGA and DTG) is shown in Fig. 6a. In TG curve the
main weight lost occurred around 450 °C which indicates the decomposition of the CuPc
structure.
Moreover, XRD pattern of CuPc was investigated and is shown in Fig. 6b; this pattern
presents the set of peaks at 10.62°, 12.38°, 18.19°, 18.49°, 21.53°, 23.13°, 23.78°, 26.27°,
2
8.01°. In addition, XRD pattern of reused CuPc exhibited the same pattern. This
observation confirms the stable structure of CuPc during the reaction.
9

Fig. 6. TGA-DTG plots (a) and XRD patterns (b) of CuPc
3
3
.2. Catalytic Performance
.2.1. Effect of solvent on the hydroxylation of benzene
We attempted to find the best conditions for hydroxylation of benzene to phenol. Since
solvent plays a very important role in this reaction, its effect was studied. Table 1 shows the
effect of solvent and verifies this point that the reaction had no acceptable yield in the solvent-
free conditions which could be related to participation of the solvent in the relatively polar
transition state of the reaction, and a solvent like acetonitrile with moderate polarity
(
dielectric constant=) decreases the activation energy appreciably. By decreasing the
polarity of solvent, and using acetone (dielectric constant=) or dichloromethane (dielectric
constant=) the yield of phenol in CH Cl reached to 1.2%.
2
2
Table 1. Effect of solvent on the hydroxylation of benzene
Entry
Solvent
Solvent free
Acetonitrile
Acetone
Yield (%)
Selectivity (%)
1
2
3
4
5
6
2.1
>98
13.9
>98
13.1
>98
Dichloromethane
1.2
100
H
2
O
Trace
Trace
Trace
Trace
2
H O/Ethanol
Reaction conditions: Benzene (1 mL), H
2
O (3 mL), Catalyst (40 mg), r.t., 15 h.
2
1
0

3
.2.2. Effect of the ratio of H
2
2
O /benzene on the hydroxylation of benzene
In this respect, the reaction was carried out by using different ratios of H
as seen by increasing the amount of oxidant the yield of phenol enhanced appreciably. Therefore,
the 3/1 was the best ratio of H /benzene; larger ratios decreased the selectivity of phenol
appreciably. When the ratio of H /benzene was changed to 4/1, the selectivity of phenol
2
O
2
/benzene, and
2
O
2
2
O
2
decreased to 63% and resorcinol was identified as a by-product. Therefore, as expected
because of over-oxidation reaction selectivity to the main product decreases appreciably.
As shown in Table 2, in the absence of the oxidant hydroxylation of benzene had no result.
Table 2. Effect of the ratio of H
2
2
O /benzene on the hydroxylation of benzene
Entry
Ratio of Ox/Be (mL)
Yield (%) Selectivity (%)
1
2
3
4
5
No oxidant
0
0
1/1
2/1
3/1
4/1
4.0
>98
>98
>98
63
7.9
13.9
13.8
Reaction conditions: Benzene (1 mL), Catalyst (40 mg), Acetonitrile (5 mL), r.t., 15 h.
3
.2.3. Effect of the amount of catalyst on the hydroxylation of benzene
Table 3 shows the effects of the amount of catalyst on the hydroxylation of benzene. As
can be seen, the reaction did not occur in the absence of the catalyst, but by increasing the
amount of the catalyst the yield of phenol enhanced, and 40 mg of catalyst was enough for
maximum yield of phenol. It is worth noting that CuSO as a catalyst led to an explosive
4
reaction in a very short time.
1
1

Table 3. Effect of amount of the catalyst on hydroxylation of benzene
Entry
Amount of catalyst (mg) Yield (%)
Selectivity (%)
1
2
3
4
5
Without catalyst
0
--
9.8
13.9
14.0
0
--
>98
>98
>98
a
CuSO
30
4
40
50
Reaction conditions: Benzene (1 mL), H
Explosive mixture
2
O (3 mL), Acetonitrile (5 mL), r.t., 15 h.
2
a
3
.2.4. Effect of time on the hydroxylation of benzene
As can be seen in Fig. 7 the yield of phenol was steadily increased over time of the
reaction and it reached to maximum after 15 h, but after that, selectivity of phenol was reduced
due to production of resorcinol as an over-oxidation product.
Fig. 7. Effect of time on the hydroxylation of benzene
3
.2.5. Reusability of the catalyst
One of the important tasks of green chemistry is the recovery capability of a catalyst. In
the present work copper phthalocyanine was employed as an insoluble complex in common
solvents such as acetonitrile. This is an outstanding feature of phthalocyanines which encouraged
us to use it as a heterogeneous catalyst without any immobilizing on the solid supports. For the
1
2

sake of catalyst recovery, after completing a reaction, catalyst was separated using centrifugation
10 min, 7000 rpm) and washed by acetonitrile and ethanol several times. After drying in oven, it
(
was reused in a new run under the optimized conditions, where after five runs the yield of phenol
had no considerable changes. As previously mentioned, FE-SEM, TEM and EDX results verify
that the catalyst was stable during the reactions. Also, this was confirmed by ICP results and the
lack of metal leaching from the complex structure. The reusability data are summarized in Table
4
. Perhaps talking about the E factor concept with regard to waste minimization in this
reaction would be helpful. The calculated atom utilization of 84% for the benign oxidation
of benzene to phenol is in the line of green chemistry [37].
Table 4. Recycling of the catalyst
Entry
Trials number
Yield (%)
Selectivity (%)
1
2
3
4
5
Fresh
Run. 2
Run. 3
Run. 4
Run. 5
13.9
13.8
13.8
13.2
13.2
>98
>98
>98
>98
>98
Reaction conditions: Benzene (1 mL), H
2
O
2
(3 mL), Catalyst (40 mg), Acetonitrile (5 mL), r.t.,
5 h.
1
3
.2.6. Comparison with previously reported catalysts
The data in Table 5 compare the results obtained over various heterogeneous catalysts
II
2+
such as Cu0.10Ce0.90
O
2-δ, [17] [Fe(BMPA)Cl ] [38], and [Ni (tmpa)] [39] that are much more
3
elaborated than CuPc and demonstrates that the oxidation of benzene over CuPc as a cheap
catalyst might be one of the best catalysts in respect of hydroxylation of benzene to phenol with
very high selectivity.
1
3

Table 5. Comparison with previously reported catalysts
Entry
Catalyst
Solvent
Yield of
phenol (%)
43
Selectivity
Ref.
(%)
a
1
2
3
4
5
6
7
8
9
Cu0.10Ce0.90
O
2-δ
CH
CH
CH
CH
CH
CH
CH
3
3
3
3
3
3
3
CN
CN
CN
CN
CN
CN
CN
100
[17]
[38]
[39]
[40]
[41]
[42]
[43]
[7]
b
[Fe(BMPA)Cl
3
]
29.7
21
100
II
2+ c
[Ni (tmpa)]
V/mp-C
>99
d
3
N
4
18
95.9
98
e
Metal-free Graphene-based
17.8
11.7
10
f
Fe-supported SBA-16
96.4
18.4
92.8
92.2
>98
g
Fe-CN/TS-1
h
0.2-V-C-300
CH
3
3
CO
2
2
H
H
36.3
29
i
Cu0.90–V-HMS
CH
CO
[44]
1
0
CuPc
CH
3
CN
13.9
[This work]
a
b
-1
Reaction conditions: Be: 5 mL, H
2
O
2
: 10 mL, Catalyst: 0.15 g, 70 °C, 6 h; Be: 0.77 mol L ,
-1
-1
c
H
2
O
2
: 0.77 mol L , Catalyst: 7.7 × 10-3 mol L , 25 °C, 24 h; Be: 5.0 μmol, H
Catalyst: 0.50 μmol, TEA: 5.0 μmol, 60 °C, 5 h; Be: 1.5 mL, H
C, 3 h; Be: 130 mg, H
Catalyst: 0.1 g, 65 °C, 8 h; Be: 0.8 mL, H
2
O
2
: 2.5 mmol,
d
2
O
2
: 3.0 mL, Catalyst: 60 mg, 60
: 2.4 mL, Catalyst: 130 mg, 60°C, 16 h; Be: 1 mL, H
e
f
°
2
O
2
2
O
2
: 2 mL,
g
2
O
2
: 0.51 mL, Catalyst: 50 mg, water: 4 ml, 60 °C, 4
h
i
h; Be: 0.4 mL, H
.10 g, 70 °C, 3 h.
2
O
2
: 1.4 mL, Catalyst: 20 mg, 70 °C, 3 h; Be: 2 mL, H
2
2
O : 7 mL, Catalyst:
0
4. Conclusion
As a synopsis, we successfully used the copper phthalocyanine as a heterogeneous
catalyst for direct hydroxylation of benzene to phenol by using hydrogen peroxide under mild
conditions. CuPc represented high catalytic reactivity in this oxidation and phenol was achieved
with 13.9% yield and >98% selectivity. CuPc has no solubility in acetonitrile thus it is
heterogeneous without any encapsulation process and this feature is considerable; moreover
CuPc is very stable against the hydrogen peroxide and benzene too. Also, leaching of Cu is
ignorable and reusability of this catalyst was satisfactory without any change in catalytic
reactivity.
1
4

Conflicts of interest
The authors declare no competing financial interest.
Acknowledgements
Thanks are due to the Research Council of the Isfahan University of Technology for
supporting this work.
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Figures legend
Scheme 1. Syntheis of CuPc
Fig. 1. FT-IR spectrum of CuPc
Fig. 2. UV-Vis spectra of fresh and reused CuPc
Fig. 3. XPS analysis at the whole scanning (a), C 1s (b), N 1s (c), Cu 2p (d) and O 1s (e) region
of CuPc
Fig. 4. FE-SEM, EDX and TEM of fresh (a and c) and reused (b and d) of CuPc
Fig. 5. Adsorption/desorption isotherm of CuPc
Fig. 6. TGA (a) and XRD (b) patterns of CuPc
Fig. 7. Effect of time on the hydroxylation of benzene
Scheme 1
1
7

Fig. 1
Fig. 2
1
8

Fig. 3
1
9

Fig. 4
Fig. 5
2
0

Fig. 6
Fig. 7
Tables legend
Table 1. Effect of solvent on the hydroxylation of benzene
Table 2. Effect of the ratio of H
2
2
O /benzene on the hydroxylation of benzene
Table 3. Effect of the amount of catalyst on the hydroxylation of benzene
2
1

Table 4. Recycling of the catalyst
Table 5. Comparison with previously reported catalysts
Table 1
Entry
Solvent
Solvent free
Acetonitrile
Acetone
Yield (%)
Selectivity (%)
>98
1
2
3
4
5
6
2.1
13.9
>98
13.1
>98
Dichloromethane
1.2
100
H
2
O
Trace
Trace
Trace
Trace
2
H O/Ethanol
Reaction conditions: Benzene (1 mL), H
2
O (3 mL), Catalyst (40 mg), r.t., 15 h.
2
Table 2
Ratio of Ox/Be (mL) Yield (%) Selectivity (%)
Entry
1
2
3
4
5
No oxidant
0
0
1/1
2/1
3/1
4/1
4.0
>98
>98
>98
63
7.9
13.9
13.8
Reaction
conditions:
Benzene (1 mL), Catalyst (40 mg), Acetonitrile (5 mL), r.t., 15 h.
Table 3
Amount of catalyst (mg) Yield (%)
Entry
1
Selectivity (%)
0
Without catalyst
0
2
2

a
2
3
4
5
CuSO
30
4
--
9.8
13.9
14.0
--
>98
>98
>98
40
50
Reaction conditions: Benzene (1 mL), H
Explosive mixture
2
2
O (3 mL), Acetonitrile (5 mL), r.t., 15 h.
a
Table 4
Yield (%)
Entry
Trials number
Selectivity (%)
1
2
3
4
5
Fresh
Run. 2
Run. 3
Run. 4
Run. 5
13.9
13.8
13.8
13.2
13.2
>98
>98
>98
>98
>98
Reaction conditions: Benzene (1 mL), H
2
O
2
(3 mL), Catalyst (40 mg), Acetonitrile (5 mL), r.t.,
5 h.
1
Table 5
2
3

Entry
Catalyst
Solvent
Yield of
phenol (%)
43
Selectivity
(%)
Ref.
a
1
2
3
4
5
6
7
8
9
Cu0.10Ce0.90
O
2-δ
CH
CH
CH
CH
CH
CH
CH
3
3
3
3
3
3
3
CN
CN
CN
CN
CN
CN
CN
100
[17]
[38]
[39]
[40]
[41]
[42]
[43]
[7]
b
[Fe(BMPA)Cl
3
]
29.7
21
100
II
2+ c
[Ni (tmpa)]
V/mp-C
>99
d
3
N
4
18
95.9
98
e
Metal-free Graphene-based
17.8
11.7
10
f
Fe-supported SBA-16
96.4
18.4
92.8
92.2
>98
g
Fe-CN/TS-1
h
0.2-V-C-300
CH
3
3
CO
2
2
H
H
36.3
29
i
Cu0.90–V-HMS
CH
CO
[44]
1
0
CuPc
CH
3
CN
13.9
[This work]
a
b
-1
Reaction conditions: Be: 5 mL, H
2
O
2
: 10 mL, Catalyst: 0.15 g, 70 °C, 6 h; Be: 0.77 mol L ,
-1
-1
c
H
2
O
2
: 0.77 mol L , Catalyst: 7.7 × 10-3 mol L , 25 °C, 24 h; Be: 5.0 μmol, H
Catalyst: 0.50 μmol, TEA: 5.0 μmol, 60 °C, 5 h; Be: 1.5 mL, H
C, 3 h; Be: 130 mg, H
Catalyst: 0.1 g, 65 °C, 8 h; Be: 0.8 mL, H
2
O
2
: 2.5 mmol,
d
2
O
2
: 3.0 mL, Catalyst: 60 mg, 60
: 2.4 mL, Catalyst: 130 mg, 60°C, 16 h; Be: 1 mL, H
e
f
°
2
O
2
2
O
2
: 2 mL,
g
2
O
2
: 0.51 mL, Catalyst: 50 mg, water: 4 ml, 60 °C, 4
h
i
h; Be: 0.4 mL, H
.10 g, 70 °C, 3 h.
2
O
2
: 1.4 mL, Catalyst: 20 mg, 70 °C, 3 h; Be: 2 mL, H
2
2
O : 7 mL, Catalyst:
0
Highlights
2
4


Copper phthalocyanine has no solubility in common solvents without any
immobilizing.


Hydroxylation of benzene was performed and phenol was achieved with high yield.
High stable structure of copper phthalocyanine prevents from leaching the metal.
2
5