Facile synthesis of 2-methylquinolines from anilines on mesoporous N-doped TiO2 under UV and visible light

Article abstract of DOI:10.1080/15533174.2012.740755

Nitrogen-doped TiO₂ was synthesized by a simple wet method using a nitrogen precursor hydrazine hydrate and nano TiO₂. This photocatalyst was characterized by X-ray diffraction, highresolution transmission electron microscopy, diffused reflectance spectra, photoluminescence, and X-ray photoelectron spectroscopy. XPS analysis indicates the incorporation of anionic nitrogen in TiO₂ lattice as O-Ti-N linkage. N₂ adsorption-desorpion isotherm indicates the mesoporous nature of N-TiO₂ with the surface area 130.0 m²/g. Sizes of N-TiO₂ particles are found to be in the range of 5-30 nm by HRTEM images. DRS spectra reveal the extended absorption to the visible range. N-TiO₂ is found to be more efficient than Ag-TiO₂, Au-TiO₂, and Pt-TiO₂ in quinaldine synthesis under visible light. Copyright Taylor & Francis Group, LLC.

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Facile Synthesis of 2-Methylquinolines From Anilines on
Mesoporous N-Doped TiO Under UV and Visible Light
2
a
a
K. Selvam & M. Swaminathan
a
Department of Chemistry , Annamalai University , Annamalainagar , India
Accepted author version posted online: 10 Dec 2012.Published online: 26 Feb 2013.
To cite this article: K. Selvam & M. Swaminathan (2013) Facile Synthesis of 2-Methylquinolines From Anilines on Mesoporous
N-Doped TiO Under UV and Visible Light, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry,
2
43:4, 500-508, DOI: 10.1080/15533174.2012.740755
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:500–508, 2013
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2012.740755
Facile Synthesis of 2-Methylquinolines From Anilines
on Mesoporous N-Doped TiO Under UV and Visible Light
2
K. Selvam and M. Swaminathan
Department of Chemistry, Annamalai University, Annamalainagar, India
fore, nitrogen doping of CS-TiO2 using hydrazine hydrate by a
was synthesized by a simple wet method simple wet method is expected to form an efficient photocatalyst
2
Nitrogen-doped TiO
using a nitrogen precursor hydrazine hydrate and nano TiO
This photocatalyst was characterized by X-ray diffraction, high-
resolution transmission electron microscopy, diffused reflectance
spectra, photoluminescence, and X-ray photoelectron spec-
troscopy. XPS analysis indicates the incorporation of anionic ni-
2
.
in UV and visible light. This method is very simple and does
not need calcination at very high temperature.
Quinaldines are pharmaceutically important as they have
been used as antimalarial, anti-inflammatory, antiasthmatic,
adsorption–desorpion antibacterial, and antihypertensive agents.[ Several methods
13]
trogen in TiO lattice as O-Ti-N linkage. N
2
2
with the sur- have been reported for the synthesis of quinaldines,[
14–17]
isotherm indicates the mesoporous nature of N-TiO
2
but
these methods have some disadvantages with regard to opera-
tional simplicity, cost of the reagent, and isolated yield.
2
face area 130.0 m /g. Sizes of N-TiO
the range of 5–30 nm by HRTEM images. DRS spectra reveal the
extended absorption to the visible range. N-TiO is found to be
more efficient than Ag-TiO , Au-TiO , and Pt-TiO in quinaldine
synthesis under visible light.
2
particles are found to be in
2
We have reported photocatalytic synthesis of 2-methyl-
quinolines with metal-doped TiO2 using UV light under am-
bient conditions and the yield was good.[ This prompted us to
2
2
2
18]
Keywords 2-methylquinoline, combustion synthesis, mesoporous prepare a visible light responsive photocatalyst N–TiO2 for the
N-TiO
2
, nano particles, visible light
synthesis of 2-methylquinolines. In the present study, we report
the preparation of N-doped TiO2 from CS-TiO2 by a simple wet
method using hydrazine hydrate and its efficiency on the photo-
INTRODUCTION
The development of visible light active semiconductors for catalytic synthesis of quinaldines from anilines under UV and
organic transformations has been a field of growing interest dur- visible light. Earlier studies on N-TiO2 were focused mainly
ing the last few years. A smart approach is the modification of the on its application in the photodegradation of organic pollu-
overwhelmingly used photocatalyst, titanium dioxide (TiO2), to tants.[
19–21]
To our knowledge, there is only one report on the ap-
enhance its activity in both UV and visible light. Different modi- plication of N-TiO2 as photocatalyst for synthetic purposes.[22]
fication methods such as coupling of TiO2 with a photosensitizer
or with another narrow band-gap semiconductor or doping TiO2 EXPERIMENTAL
[
1]
with metal and nonmetals have been used.
Materials and Methods
Titanyl nitrate was obtained from titanium tetra-isopropoxide
by the hydrolysis and subsequent nitration. Nanosized combus-
It was reported that doping nitrogen into TiO2 could effi-
ciently shift the optical response to the visible spectral range.[
2–5]
But most of the N-doping methods require high temperature and
usage of expensive precursors or costly instruments.[6–9] There-
fore, it is promising to develop a simple method for the prepa-
ration of nitrogen-doped TiO2 photocatalyst. Solution combus-
tion technique has been used for the synthesis of nano-titania
tion titania (CS-TiO ) was prepared by the solution combustion
2
synthesis method, which involves the combustion of stoichio-
metric amounts of aqueous titanyl nitrate and fuel as well as
◦
glycine at 400 C in a muffle furnace. A detailed description of
the synthesis protocol is available elsewhere.[
11]
10–12]
(
8–12 nm) (combustion Solution TiO2-CS-TiO2).[
There-
CS-TiO2 was dipped in hydrazine hydrate (80%) for 12 h,
then filtered and dried at 110 C for 3 h in air. Finally, the yellow
◦
nitrogen-doped TiO2 powder was formed. In the drying process,
a glow was detected on the surface of the powder for a moment
and then the catalyst turned to yellow.
Received 7 April 2012; accepted 13 October 2012.
The author (M. S.) thanks Council of Scientific and Industrial Re-
search (CSIR), New Delhi, for the financial support through research
grant No. 21 (0799)/10/EMR-II. Authors thank Prof. P. V. Satyam, IOP,
Bhubaneswar, India for HRTEM measurements.
Address correspondence to M. Swaminathan, Department of Chem-
istry, Annamalai University, Annamalainagar 608 002, India. E-mail:
chemres50@gmail.com
Apparatus
X-Ray diffraction (XRD) patterns of TiO2 and N-TiO2
powder samples were obtained using a Model D/Max 2550V
(Rigaku Co., Tokyo, Japan) with Cu anticathode radiation. The
500

PHOTOCATALYTIC SYNTHESIS OF QUINALDINE IN N-TIO2
501
◦
◦
diffractograms were recorded in 2θ range between 10 and 80
◦
in steps of 0.02 with a count time of 20 s at each point. Average
crystallite size was determined according to the Debye-Scherrer
equation.
D = Kλ/β Cos θ
Where D is the crystal size of the catalyst, λ is the X-ray wave-
length (0.154 nm), β is the full width half maximum (FWHM)
of the peak, K = 0.89, and θ is the diffraction angle.
The samples for HRTEM analysis were prepared by de-
positing N-TiO2 on copper grids with holey carbon film. High-
resolution TEM (HR-TEM) images were taken using a JEOL-
JEM-2010 UHR instrument (JEOL Ltd., Japan) operated at an
acceleration voltage of 200 kV with a lattice image resolution
of 0.14 nm. X-Ray photoelectron spectra (XPS) of the catalysts
were recorded in an ESCA-3 Mark II spectrometer (VG Scien-
tific Ltd., England) using Al Kα (1486.6 eV) radiation as the
source. The spectra were referenced to the binding energy of
C(1s) (285 eV).
FIG. 2. Diffuse reflectance spectra of (a) CS-TiO2, (b) N-TiO2 (color figure
available online).
The DRS of the catalysts were recorded in Shimadzu UV
2450 model UV-visible spectrophotometer (Shimadzu Scientific
Instruments, Kyoto, Japan) in the range of 800–190 nm equipped ysis was performed at 77 K with N2 gas as the adsorbate.
with an integrating sphere and using powdered BaSO4 as a The Brunauer-Emmett-Teller (BET) multipoint method least-
reference.
The specific surface areas of the catalysts were determined
squares fit provided the specific surface area.
Photoluminescence (PL) spectrum at room temperature was
using a Micromeritics ASAP 2020 sorption analyzer (Japan, recorded using a Perkin-Elmer LS 55 fluorescence spectrometer
G.K.). The samples were degassed at 423 K for 12 h and anal- (USA). The nanoparticles were dispersed in carbon tetrachloride
and excited using light of wavelength 300 nm.
Photocatalytic Synthesis of Quinaldines
In a typical experimental run, 50 mg N-TiO2 was suspended
in 25 mL of an absolute ethanolic solution containing 25 mM
of the aniline and irradiated by a 365 nm medium-pressure
FIG. 1. XRD pattern from (a) CS-TiO2, (b) N-TiO2 (color figure available
online).
FIG. 3. Photoluminescence spectra of (a) CS-TiO2, (b) N-TiO2 (color figure
available online).

502
K. SELVAM AND M. SWAMINATHAN
FIG. 4. HR-TEM analysis: (a,b) images at two different regions of N-TiO2 with their surface plots (c and d) (e) SAED pattern of N-TiO2 and (f) particle size
distribution of N-TiO2 (color figure available online).
◦
◦
mercury lamp (Sankyo Denki, Japan; intensity I = 1.381 × umn range from 50−280 C (10 C/min) and injector tempera-
− −1 −1 ◦
6
10
einstein L s ) after purging with N2 for 30 min. N2 ture 250 C, attached with mass spectrometer model SSQ 7000
−1
bubbling (flow rate = 6.1 mL s ) and magnetic stirring of the (Agilent Technologies, USA). The isolation was performed by
suspension were continued throughout the reaction while the column chromatography on a silica gel column by eluting with
◦
temperature was maintained at 30 ± 1 C. Progress of the re- a mixture of hexane and ethyl acetate (volume ratio: 8:2).
action was monitored by TLC. Product analysis was performed
by Perkin-Elmer GC-9000 (USA) with a capillary column of
DB-5 and flame ionization detector. GC/MS analysis was car-
RESULTS AND DISCUSSION
ried out using a Varian 2000 Thermo (Agilent Technologies, XRD Analysis
USA) with the following features: capillary column VF5MS
5% phenyl–95% methyl polysiloxane), 30 m length, 0.25 mm dard pattern of anatase (JCPDS 01–078-2486 C), and the rutile
internal diameter, 0.25 μm film thickness, temperature of col- lines (01-089-0553 C) are absent. This clearly reveals that the
2
The XRD pattern of CS-TiO is identical with the stan-
(

PHOTOCATALYTIC SYNTHESIS OF QUINALDINE IN N-TIO2
503
FIG. 5. X-ray photoelectron spectroscopy of N-TiO2 (a) survey spectrum, (b) Ti 2p peak, and (c) O 1s peak (d) N1s peak and (e) C peak (color figure available
online).
CS-TiO2 is of anatase phase. The X-ray diffraction patterns of Photoluminescence Spectra of N-TiO2
the prepared N-TiO2 sample match that of the undoped TiO2
Photoluminescence (PL) spectra of prepared TiO2 and
and are identical with the JCPDS pattern of anatase (Figure 1). N-TiO are displayed in Figure 3. Both spectra are similar
2
There is no diffraction peak of Ti–N compound, which can be and show near band gap emission (NBE) and blue or deep
attributed to the small amount of the doped nitrogen.
level emission (DLE). But PL intensity of N–TiO is lower
2
than prepared TiO2. The NBE of N–TiO2 and TiO2 at 420 nm
correspond to the direct band gap of the oxides and this
UV-Visible Diffuse Reflectance Spectra
Diffuse reflectance spectra of N-TiO2 and TiO2 are shown emission is due to the recombination of electron hole. The DLE
in Figure 2. N-TiO2 sample has increased absorption in the of both oxides at 485 nm may be due to the oxygen vacancies in
range of 400–800 nm compared to TiO2.. This increases its the lattice.[ Lower PL intensity of N-TiO at 420 nm indicates
photocatalytic activity in the visible region.
23]
2
[
23,24].
a lower recombination rate of excited electrons and holes.

504
K. SELVAM AND M. SWAMINATHAN
FIG. 6. (a) N2 adsorption-desorption isotherm of N-TiO2 and (b) their pore
size distribution (color figure available online).
HR-TEM Analysis
FIG. 7. Time-dependent change in the concentrations of substrate and products
during photoirradiation of aniline in neat EtOH with (a) prepared TiO2 and (b)
N-TiO2 catalyst. Reaction conditions: 25 mM of aniline in ethanol, catalyst =
HR-TEM images at two different regions are shown in
Figure 4. The intergrowth of small primary particles results
in aggregates indicating mesoporous structure of catalyst.
Figure 4 also shows surface plots of corresponding regions.
−
1
−6
−1 −1
s .
5
0 mg, N2 flow rate = 6.1 mL s , IUV = 1.381 × 10 einstein L
Aggregates are seen as void space in these surface plots. The se- TiO2 is highly desirable for photocatalysis. Figure 4 shows the
lected area electron diffraction (SAED) pattern taken from these particle size distribution for N-TiO2. It can be seen that the sizes
nanocrystalline particles (Figure 4) clearly reveals the presence of N-TiO2 particles are in the range from 5 to 35 nm. The dis-
of (101) plane concentric diffraction rings of anatase TiO2 phase. tribution could be fitted well by a Gaussian function. The size
The high intense (101) feature shows that the TiO2 is preferen- distribution of N-TiO2 particles is found to be a narrow one with
tially oriented along the (101) plane. The high-resolution lat- an average particle size of 15.6 nm.
tice image shown in inset of Figure 4 confirms that the sample
is composed of aggregates of crystalline titania nanoparticles XPS Analysis
with a d-spacing (interplanar spacing) of 0.35 nm, which corre-
The chemical state of nitrogen in the catalyst has been an-
sponds to the (101) plane of anatase TiO2 (strongest intensity in alyzed through X-ray photoelectron spectra. The XPS survey
SAED).[
25,26]
Such high anatase crystallinity in the mesoporous spectrum of N-TiO2 sample in Figure 5 shows the presence

PHOTOCATALYTIC SYNTHESIS OF QUINALDINE IN N-TIO2
505
FIG. 8. GC-MS chromatograms at different reaction times for the photocatalytic conversion of aniline.
of the elements Ti, N, and O for Ti2p, N1s, and O1s core spectively. But with pure TiO2, binding energy peaks of Ti 2p3/2
levels.
and Ti 2p1/2 were reported at 459.3 eV and 465.0 eV, respec-
N-TiO2 shows a single peak at 398.1 eV (Figure 5) for nitro- tively.[ This reveals that nitrogen doping decreases binding
gen N1s core level. Nitrogen from simple chemisorbed nitrogen energies of Ti 2p3/2 and Ti 2p1/2 peaks. Lower binding of Ti2p
or TiN should appear at ≤397.5 eV and nitrogen in NO or NO2 in N-TiO2 indicates the electronic interaction between Ti and
30]
[
27–29]
type species appears above 400 eV.
Hence this N1s peak at N anions, which can cause partial electron transformation from
398.1 eV can be attributed to the anionic N in O-Ti-N linkages. N to Ti. Electron density on Ti increases due to the lower elec-
Further the direct interaction between N and O with in the tronegativity of nitrogen compared to oxygen. Earlier Miao et al.
lattice is ruled out as this interaction will increase the binding also assigned lower binding energy peaks to TiO2-xNx.[ This
energy (BE) of the N1s level. It is further supported by the further confirms the substitution of nitrogen in place of oxygen.
31]
low BE of Ti 2p at 458.01 eV compared with that of pure TiO2
O1s spectra of the N-TiO2 consisted of two peaks (Figure 5):
(459.3 eV). From the previous observations it can be concluded one centered at 529.7 eV and the other centered at 531.6 eV.
that the peak observed in the present study at 398. 1eV is due This indicates the presence of two types of oxygen with covalent
−
to the N anion incorporated in the TiO2 as O-Ti-N structural nature in N-TiO2. This might be due to the presence of oxygen
feature.
and nitrogen from the same lattice units in TiO2. The carbon
Figure 5 shows that the high intense peaks of Ti 2p3/2 and Ti peak is attributed to the residual carbon from the sample and
p1/2 core levels of N-TiO2 appear at 458.1 and 463.1 eV, re- adventitious hydrocarbon from XPS instrument itself (Figure 5).
2

506
K. SELVAM AND M. SWAMINATHAN
BET Surface Area Analysis
N2 adsorption and desorption isotherms of prepared N-TiO2
are shown in Figure 6. It can be seen from Figure 6 that the
hysteresis loop in this material is of type IV pattern and can
be attributed to the mesoporous nature of the N-TiO2. The pore
size distribution obtained using the B. J. H. method is shown in
Figure 6. The specific surface area and pore volume of N-TiO2
2
3
sample are 130.0 m /g and 0.99–0.13 cm /g, respectively. CS-
2
TiO2 has a specific surface area of 74 m /g. It can be stated that
the maximum pore volume is contributed by the pores with an
average size of 210 nm.
Photocatalytic Synthesis of Quinaldine From Aniline
With N-TiO2
Initial experiments were carried out with ethanolic solution
of aniline using CS-TiO2 under different conditions. Either the
irradiation of ethanolic solution of aniline alone or the solution
of aniline and the catalyst without light did not give any product. FIG. 9. Percentage of quinaldine formed under different catalyst dosage [Ani-
−
1
−6
−1
line] = 25 mM, N2 flow rate = 6.1 mL s , IUV = 1.381 × 10 einstein L
Irradiation of aniline and CS-TiO2 in ethanol with 365 nm UV
light produced cyclized product of quinaldine. This indicates
that both light and CS-TiO2 are essential for the formation of
quinaldine. The catalytic activity of N-TiO2 for the synthesis of
quinaldine from aniline and ethanol was investigated. With CS-
TiO2, 6 h photoirradiation was required to form 50% quinaldine
and 15% 2,3-dimethylindole in addition to small amounts of
other reduction products (5%; Figure 7). In contrast, N-TiO2
produced 70% quinaldine and 17% 2,3-dimethylindole in 4 h
irradiation (Figure 7). This indicates that N-TiO2 promotes rapid
and selective quinaldine production.
−
1
s
, irradiation time = 4 h.
Influence of the Amount of Catalyst
We investigated the influence of the amount of N-TiO2 on
the photocatalytic cyclization of quinaldine. For the same con-
centration of aniline, the amount of N-TiO2 was varied from 25
to 150 mg in 25 mL. Percentage of product formation increased
with increasing amount of N-TiO2 up to 50 mg/25 mL and satu-
ration was attained with 50mg of N-TiO2 (Figure 9). Exceeding
0 mg, all incident photons might be scattered by catalyst par-
ticles. Therefore, in all experiments the optimum concentration
of N-TiO2 for the photocatalytic oxidation has been fixed as
GC-MS chromatograms recorded at different irradiation
times (Figure 8) reveal the formation of 1-phenyl-2-
5
(phenylamino)-propan-1-ol, 1-phenyl-2-(phenylamino)propan-
1-one, N,N-dimethylaniline, N-hydroxyaniline, N-(propan-2-
50 mg in 25 mL.
yl)aniline, 2-methyl-1,2,3,4-tetrahydroquinolin- 4-yl(phenyl)
amine as intermediates during the quinaldine formation. The
formation of by-products 2,3-dimethylindole and 2-methyl- Effect of Substituents
1,2,3,4-tetrahydroquinoline is also indicated by GC-MS chro-
Weexamined this reaction with substituted anilines inethanol
matogram obtained after 5 h. Since the intermediates formed using N-TiO2 catalyst under UV light to find out the scope of this
are the same as reported for this reaction with Au-TiO2, the method and the results are summarized in Table 1. Photoirra-
mechanism proposed for Au-TiO2 holds good for N-TiO2.[
17]
diation of alcohol solutions of different anilines with N-TiO2
According to this mechanism, initially alcohol is oxidized to the catalyst successfully afforded the corresponding quinaldines
corresponding aldehyde consuming the photogenerated valence (Table 1). In the case of p-toluidine, the main product was
band holes on TiO2. The oxidized product of ethanol condensed 2,6-dimethylquinoline (70%). m-Toluidine and o-toluidine pro-
with aniline produce an imine (Schiff base), which on further duced 2,7-dimethylquinoline (76%) and 2,8-dimethylquinoline
condensation and cyclization yields corresponding quinaldine. (69%), respectively. Irradiation of 3,5-dimethylaniline and 2,5-
The initial steps of oxidation and reduction are more facilitated dimethylaniline led to the formation of 2,5,7-trimethylquinoline
with N–TiO2 when compared to pure TiO2.
and 2,5,8-trimethylquinoline, respectively. When p-anisidine
In order to create inert atmosphere on the reaction medium was used, 6-methoxyquinaldine was formed. Except halo ani-
and to avoid the over oxidation for more selectivity, continues lines there is no significant effect of other substitutents on the
purging of nitrogen in the reaction mixture becomes essential. product yield. In the case of 4-chloro- and 4-fluoroanilines,
To find out the optimum conditions for maximum efficiency of the yield of halo-substituted quinaldines was very low. This is
this photocatalytic reaction, various experiments under different attributed to photoinduced dehalogenation before the reaction.
conditions were carried out.
Dehalogenated anilines have been identified in GC-MS analysis.

PHOTOCATALYTIC SYNTHESIS OF QUINALDINE IN N-TIO2
507
TABLE 1
Photocatalytic synthesis of 2-methylquinolines from substituted anilines using N-TiO2
Run
Reactant
Aniline
o-Toludine
m-Toluidine
p-Toluidine
o-Anisidine
m-Anisidine
p-Anisidine
3,5-Dimethylaniline
2,5-Dimethylaniline
3,5-Dimethoxyaniline
p-Phenatidine
p-Chloroaniline
p-Fluoroaniline
Product yield (%)
Quinaldine (70)
2,8-Dimethylquinoline (69)
2,7-Dimethylquinoline (76)
Byproduct (%)
Conversion (%)
1
2
3
4
5
6
7
8
9
21
18
12
17
8
11
7
3
12
5
8
72
80
91
87
88
87
81
83
81
72
82
79
98
99
97
2,6-Dimethylquinoline (70)
9-Methoxy-2-methylquinoline (73)
7-Methoxy-2-methylquinoline (72)
6-Methoxy-2-methylquinoline (74)
2,5,7-Trimethylquinoline (69)
2,5,8-Trimethylquinoline (70)
5,7-Dimethoxy-2-methylquinoline (74)
6-Ethoxyquinaldine (90)
10
11
12
13
6-Chloro-2-methylquinoline (27)
6-Fluoro-2-methylquinoline (17)
All reactions were performed with a 25 mM alcoholic solution of reactant, 50 mg of catalyst, N
2
flow rate = 6.1 mL s−1, IUV = 1.381 × 10−6
−
1
−1
s
einstein L
, irradiation time = 4 h.
Photoredox Cyclization in Visible Light
visible light. But Pt-TiO2 has the higher activity than other
Since the synthesized N-TiO2 photocatalyst has the higher catalysts in UV light. High visible light activity of N-TiO2 is
absorption in visible region, we have investigated the photo- due to its highest visible light absorption when compared to
catalytic activity of this catalyst under visible light using 300W other doped catalysts.
tungsten lamp and the results are given in Table 2. Photocatalytic
performance of this catalyst is compared with other metal-doped
CONCLUSIONS
photocatalysts such as Ag-TiO2, Pt-TiO2 and Au-TiO2 in UV
N–TiO2, prepared using CS–TiO2 has mesoporous structure
and visible light under the same experimental conditions. All
with an average size of 15.6 nm.Nitrogen in this catalyst is
doped catalysts are more efficient than prepared TiO2 both in
present as anion. N–TiO2 has higher absorption than TiO2 in the
UV and visible light.
visible region. Mesoporous N–TiO2 enables efficient quinal-
The yield of quinaldine was 33% with prepared TiO2 in 4 h
dine production from anilines both in UV and Visible light.
but it increased to 69% with N-TiO2 in visible light. Order of
N-TiO2 is more efficient than metal-doped catalysts in solar
activity of the catalysts for the synthesis of quinaldine from
light. This process has significant advantages when compared
to other methods due to (a) the use of a cheap, nontoxic catalyst
and (b) mild reaction conditions. The combination of photocat-
alytic oxidation, condensation, and cyclization in this reaction
may help to develop a new strategy toward the development of
photocatalysis-based organic synthesis in UV and visible light.
aniline using visible light is N-TiO2 > Pt-TiO2 > Au-TiO2
>
Ag-TiO2 > prepared TiO2. The results reveal that N-TiO2
has maximum catalytic activity among the five catalysts under
TABLE 2
Photocatalytic synthesis of quinaldine from aniline using
doped photocatalysts in UV and visible light
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