A photocatalytic green system for chemoselective reduction of nitroarenes

Article abstract of DOI:10.1007/s11696-016-0106-3

A highly efficient photocatalytic reduction of nitroarenes using TiO₂/polyethylene glycol 400-water (TiO₂/PEG-H₂O) is reported. This system at deoxygenated and illuminated (sunlight or violet LED) conditions efficiently reduced nitroarenes using oxalic acid or ammonium formate as a sacrificial electron donor. Reducible functional groups such as chloro, hydroxy, flouro, bromo and carbonyl were intact under the optimized reaction conditions. The 0.1 and 0.5-1 mmol amount of nitroarenes was used under sunlight and violet LED (400 nm) irradiation, respectively. Reusability of the nanotitania was successfully carried out four times. The analyses of the recovered catalyst after five runs including TEM, XRD, TGA and CHN were done and results showed that PEG is located on TiO₂; no change in morphology, crystallinity and particle sizes was observed.

Full text of DOI:10.1007/s11696-016-0106-3

Chem. Pap.
DOI 10.1007/s11696-016-0106-3
ORIGINAL PAPER
A photocatalytic green system for chemoselective reduction
of nitroarenes
Moosa Ramdar1 Foad Kazemi1,2 Babak Kaboudin1
•
•
Received: 15 June 2016 / Accepted: 9 November 2016
Ó Institute of Chemistry, Slovak Academy of Sciences 2016
Abstract A highly efficient photocatalytic reduction of
nitroarenes using TiO2/polyethylene glycol 400-water
(TiO2/PEG–H2O) is reported. This system at deoxygenated
and illuminated (sunlight or violet LED) conditions effi-
ciently reduced nitroarenes using oxalic acid or ammonium
formate as a sacrificial electron donor. Reducible func-
tional groups such as chloro, hydroxy, flouro, bromo and
carbonyl were intact under the optimized reaction condi-
tions. The 0.1 and 0.5–1 mmol amount of nitroarenes was
used under sunlight and violet LED (400 nm) irradiation,
respectively. Reusability of the nanotitania was success-
fully carried out four times. The analyses of the recovered
catalyst after five runs including TEM, XRD, TGA and
CHN were done and results showed that PEG is located on
TiO2; no change in morphology, crystallinity and particle
sizes was observed.
Introduction
Energy consumption is a future challenge. Therefore,
renewable and natural energy sources, such as sunlight, can
be employed as a green source of energy (Zhou and Hu
2010). To this aim, nanochemistry allows the use of
inexpensive materials and inexpensive processing tech-
nologies to harvest sunlight and open up new views to
attain higher solar energy conversion performance at lower
costs (Atwater and Polman 2010; Scholes et al. 2011;
Schuller et al. 2010; Schwede et al. 2010). In addition,
recently, light-emitting diodes (LED) have been applied as
a marvelous instrument to initiate photocatalytic reactions.
LEDs can emit light of different wavelength (infrared,
visible, or near-ultraviolet).
Since the 1970s, photocatalytic processes have attracted
substantial attention and are still very active and evolving
research areas (Chen and Mao 2007). Heterogeneous
photocatalysis by semiconductor materials has been gain-
ing increasing interest in photocatalytic water cleavage
(Brimblecombe et al. 2008; Esswein and Nocera 2007;
Kanan and Nocera 2008; Tang et al. 2008), photodegra-
dation of dyes (Shan et al. 2008) and phenols (Lea and
Adesina, 2001) and in organic synthesis (Di Paola et al.
2008; Mahdavi et al. 1993; Rios-Berny et al. 2010; Gao
et al. 2015; Flores et al. 2007; Ramdar et al. 2016; Fried-
mann et al. 2016) due to its likely potential for solar energy
conversion. TiO2, because of its unique chemical and
physical properties, such as high efficiency, low cost,
physical and chemical stability, widespread availability,
and noncorrosive property is broadly used in the fields of
solar energy conversion and photocatalysis (Di Paola et al.
2008). TiO2-P25 as an active and available catalyst is used
widely in photodegradation and organic synthesis. Li et al.
first reported a photoinduced reduction of nitro compounds
Keywords Violet LED Á Sunlight Á PEG-TiO2 Á
Photocatalytic Á Chemoselective Á Green synthesis
Electronic supplementary material The online version of this
article (doi:10.1007/s11696-016-0106-3) contains supplementary
material, which is available to authorized users.
& Foad Kazemi
kazemi_f@iasbs.ac.ir
1
Department of Chemistry, Institute for Advanced Studies in
Basic Sciences (IASBS), GavaZang, Zanjan 49195-1159,
Iran
2
Center for Climate and Global Warming (CCGW), Institute
for Advanced Studies in Basic Sciences (IASBS), GavaZang,
Zanjan 45137-66731, Iran
123

Chem. Pap.
to the corresponding amines using TiO2-P25 as a catalyst
under UV light; they used 2 ml of a 0.01 M solution of
nitrobenzene in the reaction (Mahdavi et al. 1993).
images were obtained with Philips CM120, VEGA\-
TESCAN-XMU. Thermogravimetric analysis was con-
ducted from room temperature to 700 °C in a nitrogen flow
using a NETZSCH STA 409 PC/PG instrument. Nitrogen
sorption analysis (Belsorp, BELMAX, Japan) was used for
further analysis of the catalyst. FTIR spectra were recorded
on Bruker-vector 22.
Gray and Thurnauer reported that TiO2-P25 can also be
active in visible light. They reported the presence of small
rutile crystallites causes rapid electron transfer from rutile
to lower energy anatase lattice trapping sites under visible
illumination leading to a more stable charge separation and
the photoactivity of TiO2-P25 in visible light. It was con-
cluded that extension of the photoactivity into visible
wavelengths is due to antenna effect of the rutile phase
(Hurum et al. 2003). The selective reduction of nitroarenes
with sunlight and blue LED irradiation using TiO2-P25 in
ethanol as solvent was reported by us (Zand et al. 2014). In
addition, we reported (Abdollahi et al. 2014b) aqueous-
phase chemoselective reduction of a wide range of aro-
matic nitro substrates (0.1 mmol scale) in the presence of
b-cyclodextrin-TiO2 (b-CD-TiO2) under sunlight irradia-
tion. The b-CD was introduced as a green nest for reduc-
tion of nitroarenes. Through this method, overcome of
some semiconductor limitations in water, associated with
the low solubility of substrates and overoxidation of
organic compounds which are a result of the oxidant spe-
Nitro compounds (0.1 mmol under sunlight and
0.5 mmol under UV LED irradiation) were dissolved in
PEG-400 (1.5 ml) and then 10 ml of water was added to
the solution; commercial TiO2 (P25) (40 mg) and oxalic
acid (1.5 equimolar) were added into a round bottom Pyrex
flask (25 ml).The reaction mixture was degassed by Argon
gas (20 min) and sealed with a septum. Afterwards, the
flask was irradiated under stirring with sunlight or violet
LED (see the data in Table 2). After the completion of the
reaction according to GC monitoring, NaHCO3 was added
to increase pH = 7 and the mixture was stirred at room
temperature. The aqueous layer was extracted with EtOAc
(2 9 10 ml). The organic layer was dried with sodium
sulfate, filtered and evaporated in vacuum.
Á
cies produced (such as OH and O-2 Á/HO2Á ) in a photocat-
Results and discussion
alytic process, was achieved.
PEGs as green inexpensive phase transfer catalysts have
other properties such as low toxicity, water solubility, ease
of recoverability, thermal stability, low volatility and
biodegradability. Among PEGs, liquid PEG-400 can be
used as solvent with or without water addition (Harris et al.
1982; Ido et al. 1997; Mates and Ring 1987; Hasan Nia
et al. 2015; Sheftel and Victor 2000).
One problem of heterogeneous photocatalytic reactions is
low amount of substrate (Eskandari et al. 2014; Hakki et al.
2013; Mahdavi et al. 1993; Shiraishi et al. 2012; Wang et al.
1997; Zand et al. 2014). In our previous report (Abdollahi
et al. 2014b), we used b-CD-TiO2 for the reduction of
nitroarenes (1:1 b-CD:nitroarene, 0.1 mmol scale) in water
under sunlight irradiation. The guest–host nitroarenes-b-CD
solubilized in water and also the dispersity and aggregation
prevention of TiO2 were demonstrated to have been
improved. Today, the LED irradiation has many advantages;
LEDs are inexpensive and available in different forms, but
unfortunately, the b-CD-TiO2 photocatalysis was unsuc-
cessful under blue LED irradiation. PEGs are known as
available, nanoparticle stabilizer, nonexpensive and water
dispersive agents (Hasan Nia et al. 2015). Also PEG was used
for preparation of TiO2 (Bu et al. 2004) and combination of
PEG-TiO2reduces TiO2 cytotoxicity (Mano et al. 2012).
Herein we report a new method for nitro aromatic reduction
in water under sunlight and violet LED and in the presence of
PEG-400-modified TiO2 as catalyst.
Now, based on our experience of working with semi-
conductor photocatalysts such as TiO2 and CdS in nitro
reduction in aqueous and organic phases (Abedi et al. 2013;
Eskandari et al. 2013, 2014; Abdollahiet al. 2014a, b; Zand
et al. 2014; Safari and Kazemi 2016), we report here a
protocol for selective photocatalytic reduction of nitroare-
nes in water using TiO2/PEG–H2O photocatalytic condi-
tion under sunlight and violet LED irradiation. We
introduce a method that would increase the amount of
substrate to 0.5–1 mmol of nitroarenes.
Experimental
Nitrobenzene was chosen as a model compound for the
study of optimized reaction conditions. Oxalic acid was
chosen as a sacrificial reagent as in our previous work
(Abdollahi et al. 2014b). The reduction reaction was car-
ried out under sunlight irradiation. 0.1 mmol of nitroben-
zene dissolved in 1.5 ml of different water dispersive
agents: diethylene glycol, triethylene glycol, PEG-400 and
diglyme (Table 1, entries 4,6–8). These solutions were
Nitro compounds, polyethylene glycol-400 (PEG-400) and
oxalic acid were purchased from Merck Co. Ammonium
formate (HCO2NH4) and titanium dioxide (TiO2-P25) were
supplied by Fluka and Degussa Co., respectively. All
chemicals were used as received without further purifica-
tion. Deionized water was used in all experiments. CHNS
analysis was recorded with ElementarVario EL III. TEM
123

Chem. Pap.
added to 10 ml of water including 40 mg of TiO2-P25. The
reaction progress was monitored with GC (Table 1).
Excellent results were obtained for triethylene glycol,
PEG-400 and diglyme. The PEG-400 was selected for its
availability and low cost. The optimization of PEG
amounts was carried out and 1.5 ml of PEG-400 was
chosen (Table 1, entries 2–5).
The photocatalytic behavior of the reaction was con-
firmed through reactions in the absence of photocatalyst
and light at separate experiments (Table 1, entries 13, 14).
The effect of nitrobenzene amounts (0.05, 0.1 and
0.2 mmol) was optimized. The best conversion was
obtained for 0.1 mmol of nitrobenzene after sunlight irra-
diation for 3.5 h (Table 1, entries 15,16).
TiO2
Dispersive agent
Light
NH2
NO2
Table 1 The optimization on photocatalytic reduction of nitrobenzene in the presence of TiO2-P25
Hole Scavenger
H
2O
Entry
Dispersive agent (ml)
Hole scavenger
Light source
TiO2 amount (mg)
Yield (%)a
1
–
Oxalic acid
Oxalic acid
Oxalic acid
Oxalic acid
Oxalic acid
Oxalic acid
Oxalic acid
Oxalic acid
–
Sun
40
40
40
40
40
40
40
40
40
40
40
40
–
38
2
PEG 400 (0.5)
PEG 400 (1)
Sun
44
3
Sun
91
4
PEG 400 (1.5)
PEG 400 (2)
Sun
96
5
Sun
98
6
Diethylene glycol (1.5)
Triethylene glycol (1.5)
Diglyme (1.5)
PEG 400 (1.5)
PEG 400 (1.5)
PEG 400 (1.5)
PEG 400 (1.5)
PEG 400 (1.5)
PEG 400 (1.5)
PEG 400 (1.5)
PEG 400 (1.5)
PEG 400 (1.5)
PEG 400 (1.5)
PEG 400 (1.5)
PEG 400 (1.5)
PEG 400 (1.5)
PEG 400 (1.5)
PEG 400 (1.5)
PEG 400 (1.5)
b-cyclodextrin
Sun
41
7
Sun
97
8
Sun
100
43
9
Sun
10
11
12
13b
14c
15d
16e
17
18
19
20
21
22f
EtOH
Sun
70
Ammonium formate
Sodium sulphite
Oxalic acid
Oxalic acid
Oxalic acid
Oxalic acid
Oxalic acid
Oxalic acid
Oxalic acid
Oxalic acid
Oxalic acid
Oxalic acid
Oxalic acid
Oxalic acid
Oxalic acid
Sun
95
Sun
61
Sun
0
–
40
40
40
30
35
50
60
80
40
40
40
40
0
Sun
100
76
Sun
Sun
50
Sun
86
Sun
97
Sun
96
Blue LED
Violet LED
Violet LED
violet LED
violet LED
0
100
100
100(92i)
2(8k)
g
23
h
24
25j
a
Sunlight intensity between (870 and 1070 Lux)
Without TiO2
b
c
d
e
f
In dark
0.05 mmol nitrobenzene was used
0.2 mmol nitrobenzene was used
Nitrobenzene (0.1 mmol) oxalic acid (0.15 mmol), 3 h
Nitrobenzene (0.5 mmol) oxalic acid (0.75 mmol), 7 h
Nitrobenzene (1 mmol) oxalic acid (1.5 mmol), 13 h
Isolated yield
g
h
i
j
b-CD (1 mmol), nitrobenzene (1 mmol), oxalic acid (1.5 mmol), 13 h
0.1 mmol b-CD was used
k
123

Chem. Pap.
100
90
80
70
60
50
400–water mixture at excitation wavelength of 400 showed
emissions at 524.2 and 470.89 nm. This fact confirmed the
activity of the catalyst under violet LED irradiation. The
TiO2/polyethylene glycol 400–water mixture did not show
any emission at 440 nm, and this evidence also confirmed
inactivity of the photocatalyst under blue LED irradiation
(see Figure S1, S2 in Supporting Information). For com-
parison, the use of violet LED was also checked by b-CD-
TiO2 method. Using TiO2 40 mg, 1:1 and 1:10 b-CD:ni-
trobenzene (1 mmol scale of nitrobenzene) in water under
violet LED (2 9 3 W), only 2 and 8% conversion was
shown, respectively, after 13 h (Table 1, entry 25).
Series1
65
25
35
45
55
TiO2 (mg)
Fig. 1 The optimization of TiO2 amount used in the reduction of
nitrobenzene under sunlight irradiation
After optimizing the reaction conditions, to consider the
scope of the developed method, the reduction of various
nitro compounds containing different functional groups
was performed. As shown in Table 2, the photocatalytic
reduction of diverse aromatic nitro compounds including
electron-rich and electron-deficient functional groups pro-
ceeded readily at experimental conditions and afford well
to excellent yields of the corresponding aromatic amines
(Table 2). For example m-chloronitrobenzene and m-ni-
trotoluene both converted to the m-chloroaniline and m-
toluidine after 3 h with excellent yields (Table 2, entries 2,
5). It seems that solubility of nitroarenes and their corre-
sponding products has major role in the reactivity. It was
observed that p-nitrophenol with appropriate solubility but
with an electron donating group was completely converted
to the p-aminophenol (Table 2, entry 7). In contrast, p-
nitrobromobenzene, the low water solubility including
electron-withdrawing group, only converted to the p-bro-
moaniline with 36% (Table 2, entry 8). Then with
increasing the amount of PEG from 1.5 to 2 ml, increased
solubility condition of substrate, the conversion enhanced
to 100% (Table 2, entry 8). Under LED irradiation, due to
higher concentration of nitroarenes (0.5 mmol) compared
to sunlight irradiation, the importance of solubility and also
adsorption and desorption of material (nitro and its amine)
on titania, increased, e.g., no products were found for 1,2-
dinitrobenzene and o-nitroaniline (Table 2 entries 10, 11)
and conversion yield of nitronaphthalene decreased to 34%
(Table 2 entry 9).
To exploit the optimal light absorption (Kisch 2010), we
investigated the effect of TiO2-P25 amounts on the con-
version of nitrobenzene under the above conditions. The
best result was found when 40 mg of TiO2 was used for
0.1 mmol of nitrobenzene, 1.5 ml of PEG-400, 10 ml of
water and 0.15 mmol of oxalic acid under sunlight irradi-
ation (Table 1, entries 17–20; Fig. 1).
The effect of the sacrificial additives on the reduction of
nitrobenzene as a model reaction has been checked out by
comparing preliminary yields in the presence and absence
of additives. In the absence of any additive in the reaction
conditions just 43% conversion was observed due to
reducing ability of PEG (Table 1, entry 9). Among the used
additives, oxalic acid and ammonium formate were found
as excellent reducing agents (Table 1, entries 10–12).
In addition, it is well known that a primary alcohol (such
as methanol or ethanol) can be used as both a hole scav-
enger and solvent in the photocatalytic reduction of
nitroaromatics, generating corresponding aldehydes as the
oxidation product. Since these aldehydes are toxic, a
‘‘greener’’ sacrificial reagent converting to a nontoxic
compound is preferable. Oxalic acid and ammonium for-
mate are green sacrificial hole scavengers because they are
easily oxidized to carbon dioxide (CO2) (Imamura et al.
2011).
Similar to our previous report (Zand et al. 2014), we
tried to use blue LED as a light source. We found even in
much lower concentration of nitrobenzene (0.01 mmol),
TiO2-P25(80 mg), oxalic acid (0.015 mmol), PEG (1.5 ml)
and water (10 ml) under blue LED (4 9 3 W); after 24 h
no reduction occurred (Table 1, entry 21). Because of LED
importance, we were encouraged to use more powerful
LEDs; the reaction was repeated with violet LED
(395–405 nm) (2 9 3 W). Very interestingly, the reaction
was completed after 3 h (Table 1, entry 22). This fantastic
result led to testing the reaction for the practical reduction
of nitrobenzene (1 mmol) (Table 1, entries 22–24). Again
the reaction was completed after 13 h with a 92% isolated
yield. Fluorescence spectrum of TiO2/polyethylene glycol
There is an enormous interest in developing efficient,
active and environmentally sustainable systems that would
perform the selective reduction of nitro compounds in the
presence of other reducible functional groups, such as
ketones, aldehydes or halides (Tafesh and Weiguny 1996).
In our present method, any dehalogenation was not
occurred when we used 1-chloro-3-nitrobenzene and
1-bromo-4-nitrobenzene as nitro compound, which has
been observed in some previously reported methods
(Table 2, entries 2, 8). Under the present reaction condi-
tions, high chemoselectivity with an excellent yield was
observed when 3-nitroacetophenone was used and no
123

Chem. Pap.
Table 2 Reduction of nitro
compounds using TiO2/PEG–
H2O under sunlight and violet
LED irradiation
Entry
1
Nitro
Time (h)
In sun
Yield (%)
In sunb
Yield (%)
In LEDc
Time(h)in
LED
Amine
3.5
3
96
100a
100
100
16
2
22
26
95
3
4
3.5
100
4.5
3
28
22
18
88
92
5
6
100
100
100
98
3
7
8
4
44
100
100
3
22
22
36(100)d
80
100
34
9
4.5
10
11
12
5
6
24
24
73
0
0
32(41)d
3.5
3.5
12
-
100
100
100
-
13e
123

Chem. Pap.
Table 2 continued
Entry
14e
Nitro
Time (h)
In sun
Yield (%)
In sunb
Yield (%)
In LEDc
Time(h)in
LED
Amine
3
3
-
-
98
99
-
-
15e
a
1 mmol Of nitrobenzene is used
b
Reaction conditions: nitro compound (0.1 mmol), TiO2 (0.04 g), H2O (10 ml), oxalic
acid (0.15 mmol, PEG-400 (1.5 ml) and sunlight intensity between 870 and 1070 Lux
c
Reaction conditions: nitro compound (0.5 mmol), TiO2 (0.04 g), H2O (10 ml), oxalic
acid (0.75 mmol, PEG 400 (1.5 ml) and with two 400-nm LEDs irradiation (2 9 3 W)
d
Reaction was carried out in the presence of 2 ml of PEG-400
e
Reduction was carried out in the presence of 40 mg of separated PEG-TiO2 under
sunlight irradiation
100
80
100
80
60
40
20
0
60
40
20
0
1
2
3
4
5
1
2
3
4
5
6
Run
Run
Fig. 2 Reusability of the catalyst in nitrobenzene reduction under
sunlight
Fig. 3 Reusability of the catalytic mixture through stepwise addition
of reactants under sunlight
unwanted reduction of the carbonyl group was observed
(Table 2, entry 6). A good regioselectivity was observed in
the reduction of 1,2-dinitrobenzene (Table 2, entry 10).
To consider reusability of the TiO2/PEG–H2O catalytic
system, the reduction of nitrobenzene at optimum condition
was monitored for five runs and the catalyst showed good
activity. The little decrease after the fifth run can be due to
removing PEG and TiO2 under washing step (Fig. 2), see
also Supporting Information). In addition, to better study
the catalyst photoactivity, prevention of removing PEG and
TiO2, and scalability of the reaction, we examined the
stepwise increasing of nitrobenzene to the optimized
reaction. In each step in the presence of 40 mg of TiO2,
0.1 mmol of nitro benzene and 0.15 mmol of oxalic acid
were added stepwise to the reaction mixture. The excellent
results were achieved even after five runs in only 40 mg
starting TiO2. This fact shows scalability of the reaction in
addition to high activity and stability of the catalyst in this
method (Fig. 3).
Table 3 CHN analysis data for recycled PEG-TiO2 catalyst and
PEG-TiO2 before reaction
Catalyst
%N
%C
7.297
%H
PEG-TiO2
0.0
1.151
0.2
Washed TiO2-PEG
Reused separated PEG-TiO2-P25
0.0
1.04
0.716
11.53
2.136
can be useful. For this purpose, the TiO2 was added to
PEG/water (1.5 ml/10 ml) and TiO2 was separated after
3 h. The separated TiO2 was used for reduction of some
nitroarenes without the addition of PEG. Very interest-
ingly, the excellent results were obtained for nitrobenzene,
3-chloronitrobenzene and 3-nitrotoluene without any PEG
400 addition (Table 2, entries 13–15). CHN analysis of the
separated TiO2 showed 7.3% weight carbon (Table 3) and
TGA analysis showed 12.96% weight loss can be refer to
polyethylene glycol located on the titania (see Figure S3 in
Supporting Information). In addition, the FTIR of separated
TiO2-P25 (PEG-TiO2) confirmed the organic moiety (see
Figure S5 in Supporting Information). To show that how
The main question about nature of catalyst is: what is
the role of PEG? Then, study of adsorption of PEG on TiO2
123

Chem. Pap.
Fig. 4 TEM images of: a PEG-
TiO2 and b reused separated
PEG-TiO2-P25
absorption of PEG-400 takes place on TiO2, several
experiments were carried out; first, PEG-TiO2 was washed
in 60 °C and CHN analysis showed a decrease on PEG, so
this can be due to physical adsorption on TiO2 surface
(physisorption) (Table 3). The pH change of TiO2/PEG–
H2O was measured under sunlight irradiation and no
change was observed, this also confirms the physisorption
of PEG on TiO2 surface. Astruc et al. also show H-bonding
interaction between triethylene glycol and surface OH
bonds of metal oxides (Deraedt et al. 2015). These results
can be explained through adsorption of PEG on the surface
of titania and organic moieties mounted during reduction of
nitrobenzene. CHN analyses of the PEG-TiO2, washed
PEG-TiO2 and reused separated PEG-TiO2 catalysts
showed 7.29, 1.04 and 11.53% w/w of carbon (Table 3). In
addition, TGA analyses showed 12.96 and 13.1% weight
loss for PEG-TiO2 and reused separated PEG-TiO2,
respectively (see Figure S3, S4 in Supporting Information).
XRD pattern of reused separated PEG-TiO2 catalyst did
not show any change in the TiO2 crystalline phase (Fig-
ure S6 in Supporting Information).
NH2
H
O
R
N
O2
e
R
H
O
T
iO2
h
O
H
O
H
O
CO2
H
O
O
Scheme 1 Reduction of nitrobenzene using TiO2/PEG–H2O under
sunlight and violet LED irradiation
this method a promising one for practical reduction of
nitroarenes. In addition, the physisorbed PEG-TiO2 catalyst
was separated from TiO2/PEG–H2O mixture and interest-
ingly showed highly efficient activity in aqueous photo-
catalytic reduction of nitroarenes.
TEMs of PEG-TiO2 and reused separated PEG-TiO2
catalysts show no change in the particle size (Fig. 4,
Scheme 1).
Acknowledgements We thank the Institute for Advanced Studies in
Basic Sciences (IASBS) for financial support in this work. We also
thank Dr. Hamed Zandi for editing the manuscript.
In summary, we have reported a highly efficient pho-
tocatalytic reduction of nitro aromatic compounds
employing TiO2/PEG–H2O. In this method, nitroarene,
with electron-donating and electron-withdrawing groups,
has been employed successfully. The relatively high scale
of 0.1 and 0.5–1 mmol nitro compounds was used under
violet LED (400 nm) and sunlight irradiation, respectively.
The study of the catalytic system showed that PEG
attached physically on the surface of nanotitania. PEG-
TiO2 is a very efficient photocatalyst. PEG caused better
water dispersity and stability of the catalyst against
agglomeration. Excellent reusability, environmentally
benign and high-scale amount of starting materials make
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