Enhancement of Suzuki–Miyaura coupling reaction by photocatalytic palladium nanoparticles anchored to TiO2 under visible light irradiation

Article abstract of DOI:10.1016/j.catcom.2018.03.026

Plasmonic property and catalytic performance of Pd anchored to TiO₂ for Suzuki?Miyaura coupling (SMC) reactions are reported. Different from previous reports, this semiconductor with band gap ≥3 eV can afford C–C bond formation for SMC. Nano Pd/TiO₂ was successfully synthesized through a photodeposition method under sunlight. The size of Pd nanoparticles onto the surface of TiO₂ led to enhancement of localized surface plasmon resonance. This visible-light-harvesting heterogeneous photocatalyst sufficiently promoted substrates toward coupling reaction products at ambient temperature in aqueous media. Photo-generated electron-hole pairs under visible light irradiation, are the key components of activation of the substrates.

Full text of DOI:10.1016/j.catcom.2018.03.026

Accepted Manuscript
Enhancement of Suzuki–Miyaura coupling reaction by
photocatalytic palladium nanoparticles anchored to TiO2 under
visible light irradiation
Mehdi Koohgard, Mona Hosseini-Sarvari
PII:
S1566-7367(18)30118-3
doi:10.1016/j.catcom.2018.03.026
CATCOM 5367
DOI:
Reference:
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
3 December 2017
26 February 2018
21 March 2018
Please cite this article as: Mehdi Koohgard, Mona Hosseini-Sarvari , Enhancement of
Suzuki–Miyaura coupling reaction by photocatalytic palladium nanoparticles anchored to
TiO2 under visible light irradiation. The address for the corresponding author was captured
as affiliation for all authors. Please check if appropriate. Catcom(2018), doi:10.1016/
j.catcom.2018.03.026
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ACCEPTED MANUSCRIPT
Enhancement of Suzuki–Miyaura coupling reaction by
photocatalytic palladium nanoparticles anchored to TiO
under visible light irradiation
2
Mehdi Koohgard , Mona Hosseini-Sarvaria,*
a
aDepartment of Chemistry, Shiraz University, Shiraz7194684795, I.R.Iran
*Correspondence to: Prof. Mona Hosseini-Sarvari, E-mail: Hossaini@shirazu.ac.ir, Fax:
98 713 6460788; Tel: +98 713 6137169
+

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Abstract
Plasmonic property and catalytic performance of Pd anchored to TiO
coupling (SMC) reactions are reported. Different from previous reports, this
semiconductor with band gap ≥ 3 eV can afford C-C bond formation for SMC. Nano Pd/TiO
was successfully synthesized through a photodeposition method under sunlight. The size
of Pd nanoparticles onto the surface of TiO led to enhancement of localized surface
2
for Suzuki−Miyaura
2
2
plasmon resonance. This visible-light-harvesting heterogeneous photocatalyst
sufficiently promoted substrates toward coupling reaction products at ambient
temperature in aqueous media. Photo-generated electron-hole pairs under visible light
irradiation, are the key components of activation of the substrates.
Keywords: Photocatalysis, nano Pd/TiO , Suzuki−Miyaura
2
coupling reaction, heterogeneous catalyst

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1. Introduction
In the current decade, photoinduced reactions have been typically used as alternative in
the synthetic route of building blocks of complex molecules [1, 2].
TiO is a competent candidate for photocatalytic performance due to its high activity,
2
non-toxicity, stability and low cost . Its holes are strongly oxidizing and redox selective for
several substrates. Hence, several heterogeneous photocatalytic reactions have been
reported by TiO photocatalyst [3, 4]. Nevertheless, this photocatalyst suffer from low
2
capacity to absorb visible light and rapid recombination electron and hole pairs provided
by due irridation. For leaving behind these drawbacks, some modifications consist of
structural dimensions and electronic structures such as doping, dye sensitization, capping
and coupling have been applied widely [5, 6]. Modifying semiconductors, TiO , with noble
2
metals such as Pd, Ag, Pt and Au as co-catalysts are effective methods in absorbing visible
light [7-9]. The optical properties of noble metal particles originate from localized surface
plasmon resonance (LSPR) [9]. In addition this co-catalysts are operant in suppressing
electron–hole pair recombination [10, 11]. These adapted titanium dioxides not only
utilize visible light as abundant energy source but also accelerate organic reaction to
obtain higher product selectivity in a milder condition [3, 4].
Since its discovery in 1979, Palladium-catalyzed SMC reaction has provided very
powerful tool for the synthesis of natural compounds as well as medicinal, biological, and
supramolecular blocks through C-C bond formations [12, 13]. Some benefits of this
reaction rather than other coupling reactions include: (1) Boron compounds benefit form
only low toxicities (2) By-products can be easily isolated from the reaction (3) Mild
reaction conditions (4) Organoboron reagents are stable and tolerant toward thermal and
aqueous condition [14, 15]. The increasing attempt of modern chemical trend for green
and sustainable reactions condition are challenged to modify the SMC conditions. Low

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catalyst loading, lower the reaction temperatures, separating and reusing the expensive
catalysts and ligand-free catalytic systems are some of important goals because of
fastidiously ecological and economical demands. To overcome aforementioned challenges
the use of Pd heterogeneous catalysts (Pd metal immobilized onto a support including
organic, polymeric and inorganic support materials) in this reaction has been the aim of
several recent researches [16, 17]. These heterogeneous catalysts enjoy the following
advantages compared to other homogenous catalysts: (1) Separation and recovery of the
catalyst (2) To take advantage of ligand free catalytic systems.
Owning to the high level activation encumbrance of the reagents along with the rate-
limiting elementary steps, SMC reactions, particularly those which utilize heterogeneous
Pd catalysts, need relatively high temperatures and protracted reaction time [16, 18].
As there are a few reports on applying heterogeneous photocatalys on C-C SMC
reactions [18-28], hence it is important to change the susceptibility of this heterogeneous
photocatalyst, TiO , from organic transformation such as reduction and oxidation
2
reactions [3, 4] to C-C coupling reactions to benefit from low temperature reaction
condition.
We envision to build a bridge between our ongoing endeavors aimed at developing
heterogonous nano catalysts [29, 30] and photo-induced organic reaction hoping that this
methodology will advance the scientific standards of our research scope to make these
organic reactions more environmentally benign. In the present study, we surveyed nano
Pd/TiO as light-harvesting catalytic system in SMC reaction through the simultaneous
2
utilization of photo-generated electron-hole pair on semiconductor and Pd nanoparticles,
this catalytic system absorb light in the visible region acquired through LSPR. In fact, Pd
nanoparticles of special size anchored on TiO
2
give the characteristic for this
photocatalyst system to enhance surface plasmon resonance.

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2. Experimental section
2
.1. Photocatalyst preparation
Pd nanoparticles anchored to TiO
laboratory by a modified reported procedure which involved an in situ photodeposition
method [10]. Briefly, in a round-bottomed flask, a mixture of TiO p25 (0.5 g) and a chosen
amount of Pd(NO (1.0, 3.0 and 5.0 wt% of Pd loading) were added to 12 mL of ethylene
2
P25 were carried out under solar light in our
2
)
3 2
glycol. Then the flask was fixed on a magnetic stirrer and was exposed to sunlight on the
balcony at Shiraz University campus (Oct. 15, 2016, 29°59′ north latitude and 52°58′ east
longitude, 1500 m above the sea level). The solid product was centrifuged and washed
with deionized water and then ethanol four times and dried at 80 °C for 5 h on a vacuum
oven.
2
.2. A typical procedure for the photocatalytic reactions
Aryl iodide (1 mmol), aryl boronic acid (1.2 mmol), nano Pd/TiO
mL, volume ratio of 1:1), NaOC(CH (3 mmol) were placed in a 10 mL Pyrex round
2
(15 mg), H O-PEG (5
2
)
3 3
bottom flask. The flask was covered with a rubber stopper. The reaction vessel was stirred
at ambient temperature (28 °C) under visible light obtained by irradiation of 15 W flexible
white LED strips placed on the walls inside the box spirally and the reaction flask was
placed in the center of the box (see SM, S1). The temperature of the reaction system was
kept at ambient temperature with an air conditioner and a mechanical fan mounted on
the box. After completion of the reaction (monitoring by GC), the catalyst was removed by
centrifuging and the resulting mixture was extracted with AcOEt (2 × 10 mL). The organic
layers were combined and dried over anhydrous sodium sulfate (Na
2
SO ) and further
4

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concentrated under reduced pressure. The desired product was purified by column
chromatography (CC) on silica gel using n-hexane/ethyl acetate (40:1, 20:1).
To run the reaction in dark, the above reaction conditions maintained except that the flask
was wrapped with aluminum foil to impede ingress of light. Moreover, in the control
experiments the reaction conversion was monitored using a shimadzu GC 14B gas
chromatograph.
3. Results and Discussion
3
.1. Synthesis and characterization of nano Pd/TiO photocatalyst
2
A general method for reining agglomeration pd nanoparticles (Pd NPs), a phenomenon
known as Ostwald ripening, is embedding the pd nanoparticles in the surface of a metal
oxide such as TiO
.0, 3.0 and 5.0 wt% of Pd loading were carried out under solar light. Nano Pd/TiO
synthesized by the solar-assisted photodeposition of Pd NPs.
2
. At first, easily-prepared method of nano Pd/TiO
2
photocatalysts with
1
2
was
The different Pd ratios were determined by inductively coupled plasma (ICP) and
atomic absorption spectroscopy which 5.0 wt% of Pd loading was shown the highest yield
in SMC reaction according the Table S3 entry 3. This nanocatalyst (5.0 wt% nano Pd/TiO )
2
was fully characterized and explicated by transmission electron microscope (TEM),
scanning electron microscope (SEM), X-Ray diffraction energy (XRD), dispersive X-ray
spectroscopy (EDX), Brunauer–Emmett–Teller (BET), Barrett-Joyner-Halenda (BJH) and
UV–Vis analysis (see Supplementary Material (SM), S2).
3.2. Photocatalytic activity of nano Pd/TiO
2
To optimize SMC reaction in aqueous condition, 4-methoxyiodobenzene and
phenylboronic acid were surveyed at ambient temperature (28 °C) as a model reaction
and the results are summarized in Table 1. To screen the reaction under visible light and

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ligand-free conditions, firstly, we employed several solvents and bases to obtain the best
possible conversion and selectivity. In pure H
was not effective (entry 1) even after addition of tetra-n-butylammonium bromide
TBAB) as surfactant with addition time (entry 2). Whereas the polar aprotic solvents
2
O, the results exhibited that this solvent
(
mixed with water such as N,N-dimethylformamide (DMF) and acetonitrile exhibited low
yields of the coupling product (entries 3,4). Fortunately, a mixed of organic polar protic
solvents and water such as H
than pure water considering higher coupling product (3a) within 4 h (entries 5,6). So, a
mixed solvent of H O and PEG was chosen as green and environmentally media.
2
O-PEG and H O-EtOH were proved to be the better solvents
2
2
Afterward, we investigated various bases in the model reaction (entries 7-10), and
excellent yield and selectivity was achieved by using sodium tert-butoxide (entry 6).
Other strong bases such as k
respectively (entries 7,10). As known, polyethylene glycol can have both solvent
surfactant roles. Next, we surveyed different volume ratios of H O with PEG or EtOH.
According to entries 10-13, it can be found the best solvent is equal volume ratio of H
2
CO
3
and Cs
2
CO
3
exhibited good to excellent yields,
2
2
O
and PEG. After treating different molar ratio of phenylboronic acid and 4-
methoxyiodobenzene, the highest yield was obtained when 1.2 equivalent of
phenylboronic acid was treated with 4-methoxyiodobenzene (entries 6, 14, 15).

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Table 1 Optimization of base and solvent for photocatalytic SMC reactions [a]
Sel.
[%]
Conv.
Entry
Base
Solvent
[
b]
[%]
[
c]
1
NaOC(CH
3
3
)
)
3
3
H
2
O
31
98
97
2[d]
NaOC(CH
H
H
O
41
2
2
O-
3
4
5
6
7
8
9
NaOC(CH
NaOC(CH
NaOC(CH
NaOC(CH
3
3
3
3
)
)
)
)
3
3
3
3
DMF
1:1)
O-
CH CN
1:1)
O-
EtOH
1:1)
O-
PEG
1:1)
O-
PEG
1:1)
O-
PEG
1:1)
O-
PEG
1:1)
O-
PEG
1:1)
O-
EtOH
1:2)
O-
PEG
2:1)
O-
PEG
1:2)
O-
PEG
1:1)
O-
PEG
1:1)
17
19
81
88
86
56
67
85
77
75
89
93
87
67
76
95
98
97
73
79
82
91
98
95
98
98
(
H
2
3
(
H
2
(
H
2
(
H
2
Cs
2
CO
3
(
H
2
KOH
(
H
2
K
3
2
PO
CO
4
(
H
2
1
1
1
1
0
1
2
3
K
3
(
H
2
NaOC(CH
NaOC(CH
NaOC(CH
3
3
3
)
)
)
3
3
3
(
H
2
(
H
2
(
H
2
1
4[e]
NaOC(CH
)
3 3
(
H
2
1
5[f]
NaOC(CH
3 3
)
(
[
a]
Reaction conditions: 4-methoxyiodobenzene (1 mmol), phenylboronic acid (1 mmol), 5 wt% nano
(15 mg containing 7.04×10 -3 mmol of Pd), solvent (5 mL, volume ratios are mentioned after
Pd/TiO
2
solvents name), base (3 mmol), reaction time 4 h, ambient temperature (28 °C), and 15 W white LED. [b] GC
conversion: (aryliodide converted)/(initial amount of aryl iodide) × 100. [c] Selectivity: (target product
formed)/(total amount of product formed) × 100, [d] With addition of TBAB (1.0 mmol) after 6 h. [e] 4-

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methoxyiodobenzene (1 mmol), phenylboronic acid (1.2 mmol). [f] 4-methoxyiodobenzene (1.2 mmol),
phenylboronic acid (1 mmol). PEG: Polyethylene glycol 400.
Afterward, we screened different light, atmosphere condition and the amount of nano
Pd/TiO and Pd loading in this reaction (see SM, S4).
2
With this optimized condition in hand, to expand the scope of the catalytic protocol, we
performed reactions using various aryl halides with arylboronic acids under visible light,
NaOC(CH
)
3 3
as the base and H O-PEG (1:1) as aqueous media at 28 °C. As illustrated in
2
Table 2, at first several aryl iodides and aryl boronic acids were studied. The turnover
number (TON) and turnover frequency (TOF) values were achieved considering the yield
of formation of target product and based on the total amount of Pd metal. This
photocatalyst exhibited relatively high turnover frequency (TOF) and good to excellent
yields in SMC reaction(see SM, S7). This reaction condition depicts good diversity in the
presence of both electron donating and electron withdrawing groups in aryl iodides. It
was found that reaction time for most of aryl iodides is 4h except 4-iodophenol (entry 7).
Moreover, due to steric hindrance ortho-substituents on the aryl iodides affected the
reaction proceeding. Thus, the reaction time for 1-iodo-2-nitrobenzene was higher than
for 4-substitued iodobenzene (entries 4 and 5). Notably, steric hindrance ortho-
substituents on the phenylboronic acid derivatives have exhibited more impact than
ortho-substituented aryl iodides on the reaction efficiency (entries 14-16) this in
accordance with previous reports [18-28].

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Table 2 Substrate scope of SMC reactions with different substituents [a]
1
2
[b]
-1
Entry
R
R
Yield [%]
94
TON
133
136
126
139
133
136
88
TOF [h ]
1
2
3
4
H
H
33
34
31
34
22
34
14
32
33
27
32
32
43
20
18
4-COCH
3
H
96
4-OMe
H
89
4-NO
2
2
H
98
[c]
5
2-NO
H
94
6
4-CH
2
OH
H
H
96
[c]
7
4-OH
4-F
62
8
9
H
91
129
134
110
130
129
137
120
108
-
4-CF
3
H
95
1
0
4-CN
H
78
1
1
1
1
2
3
CH
3
H
92
H
4-Et
3,4,5-F
H
91
H
97
[
c]
1
4
5
2-MeO
85
[c]
1
H
H
2-MeO
2,5- Me
76
1
6
trace
-
[a] Reaction conditions: aryl iodide (1 mmol), aryl boronic acid (1.2 mmol), nano Pd/TiO
2
(15 mg containing
7
1
.04 ×10 -3 mmol of Pd), H
2
O-PEG (5 mL, volume ratio of 1:1), NaOC(CH
3
3
) (3 mmol), reaction time 4 h and
5 W white LED. [b] Yield of isolated product. [c] 6 h.
Driven by the results of the SMC reaction by aryl iodides, we then tried to extend the
catalytic scope towards various aryl bromides and chlorides at the same reaction
conditions. As illustrated in Table 3, six different aryl bromides were treated with phenyl
boronic acid. As shown, the coupling reaction could be efficiently carried out using aryl
bromides while the time of the reaction slightly increased, from 4 to 6 hours, and afforded
the products in high yields (entry 1-6). For aryl chlorides, low yields of 21% and 32%
were obtained after 20 h (entry 7, 8), respectively.

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Table 3 SMC reaction of aryl bromides and chloride with phenyl boronic acid [a]
Entry
R1
X
Yield [%][b]
TON
130
134
120
136
132
72
TOF[h-1]
1
H
Br
Br
Br
Br
Br
Br
Cl
92
95
85
96
93
51
21
32
21
22
20
22
22
12
1
2
4-COCH
3
3
4-OMe
4
4-NO
2
5
4-CH
4-OH
H
2
OH
6
7 [c]
8 [c]
29
4-NO
2
Cl
45
2
[
a]
Reaction conditions: aryl halide (1 mmol), phenyl boronic acid (1.2 mmol), nano Pd/TiO
2
(15 mg), H
2
O-
PEG (5 mL, volume ratio of 1:1), NaOC(CH
isolated product. [c] 20 h.
)
3 3
(3 mmol), reaction time 6 h and 15 W white LED. [b] Yield of
Photocatalytic recovery and reusability of the 5.0 wt % nano Pd/TiO was also studied
2
using 4-methoxyiodobenzene and phenyl boronic acid as substrates under visible light
irradiation and reaction was conducted within 4h (Figure 1). Similarly, the next
performances of the reaction were carried out. After given time, the mixture was
centrifuged to separate the catalyst. Thereafter, it was washed with H
2
O and ethyl acetate
(
AcOEt) and dried in vacuo for the next cycle. Photocatalyst maintained a high level of
efficiency after five runs, additionally; an efficiency of 87% was achieved after the 5th run.
The ICP result showed that only 0.01 wt% Pd were leached out from the catalyst surface
after five cycles.

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Run 5
Run 4
Run 3
Run 2
Run 1
0
10 20 30 40 50 60 70 80 90 100
Yield %
Fig. 1. Recyclability of recovered nano Pd/TiO
acid (1.2 mmol), nano Pd/TiO (15 mg), H O-PEG (5 mL, volume ratio of 1:1), NaOC(CH
time 4 h, 15 W white LED and reaction conducted at ambient temperature (28°C). Yield of isolated product.
2
, reaction conditions: phenyl iodide (1 mmol), phenyl boronic
2
2
)
3 3
(3 mmol), reaction
3.3. The relationship between photocatalyst activity and light intensity and
wavelength
To investigate the correlation of the photocatalytic performance of the nano Pd/TiO with
2
light irradiation, the correspondence between the reactions proceeding, light intensity
and wavelength were carried out (Figure 2 and 3). In this study, the yield of the
photocatalytic SMC reaction using nano Pd/TiO at 28 °C under light irradiation with
2
different wavelength ranges were assigned. Several 15 w LED lamps with different
wavelengths were used to afford the wavelength ranges of 400-750 ± 5 nm, 490-540 ± 5
nm, 550-600 ± 5 nm and 610-750 ± 5 and if needed, optical filter blocks were applied,
meanwhile, other parameters for the light irradiation and dark reaction conditions were
the same. As illustrated in Figure 2, whereas yields (GC yield) of the reaction under dark
conditions maintained at 22%, expanding the range of wavelengths significantly
increased reaction yields to 91%. These results are in line with UV-vis spectra of nano
Pd/TiO
2
2
(see SM, S2). In a similar manner, the dependence of the catalytic activity of nano
on the intensity of the light irradiation was investigated. Three bulb-shaped LED
Pd/TiO

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lamps, 5 W, 10 W, and 15 W, were used at identical distance to the reaction flask,
respectively. Then, the environmental temperature in the chamber was maintained at
28°C with constantly air circulation. As illustrated in Figure 3, increasing the light
intensity caused clearly proceed in the yield (GC yield) of the reaction.
9
1
1
00
90
80
70
60
50
40
30
20
10
0
78
57
3
9
22
22
22
22
6
10-750
550-750
490-750
400-750
Wavelength range (nm)
photo-induced reaction
Dark (30 °C )
Fig. 2. The dependence of the catalytic activity of nano Pd/TiO for the SMC reaction on the wavelength of
2
the light irradiation. Phenyl iodide was treated with phenyl boronic acid under given visible light irradiation
at 28 °C, GC yield.

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91
1
00
77
8
6
4
2
0
0
0
0
0
65
22
22
22
5
W
10 W
15 W
Watt
photo-induced reaction
Dark (30 °C )
Fig. 3. The dependence of the catalytic activity of nano Pd/TiO for SMC reaction on the intensity of the
2
light irradiation. Phenyl iodide was treated with phenyl boronic acid under given visible light irradiation
at 28 °C, GC yield.
3.4. Control experiments
Some control experiments were accomplished to depict the role of the charge carriers,
electron-hole pairs, presenting of radical species, the effect of CB (conduction band) and
VB (valance band) in proceeding the SMC reaction by using hole and electron scavenger
and black TiO
Redox potential for conversion of iodobenzene to iodobenzene radical anion in some
organic solvents are -2.53 (E0PhI/PhI•– vs. Ag/Ag/KCl, n-Bu
NBF
Ag/Ag/KCl, n-Bu NBF ) in dimethylsulfoxide [31] and acetonitrile [31], respectively. So
2
(see SM, S6, S8).
) and -1.86 V (E0PhI/PhI•– vs.
4
4
4
4
iodobenzene is probably a good electron acceptor versus CB of TiO (Ecb = – 0.5 V vs. NHE
2
or – 0.75 vs. SCE in acetonitrile) [32, 33].
3.5. Mechanism

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According to literature review on the heterogeneous photocatalytic SMC reactions [10,
1
8-26, 28] and the observations during the screening and control experiments, we
suggest a proposed reaction mechanism as exhibited in Figure 4.
Interaction between pd NPs and TiO forms a Schottky barrier whereby an internal
2
electric field close to the interface is procreated. Accordingly, it conducts the electrons
and holes to move in contrary directions, electrons are transferred from Pd NPs to the CB
of TiO
0, 34]. In addition, owning to the Schottky barrier, the lifetime of the charge carriers is
increased [35]. As a result, charge carrier separation results in a better photocatalytic
performance by nano Pd/TiO photocatalyst [36]. After absorbing visible light by nano
Pd/TiO , the plasmon resonance excites the electrons of the VB to be transferred into the
CB of the Pd NPs. The CB of TiO is an electron acceptor, hence, it readily accepts the
electrons from the Pd NPs to generate positive charges (h+) in the Pd. This high charge
carrier separation efficiency facilitate SMC reaction. Overall, the CB of TiO probably
2
due to photon energies resulted from electrons excited upon LSPR excitation [4,
1
2
2
2
2
serves as the active site, the C−I bond of phenyl iodide is attacked by the photogenerated
electrons and results in phenyl iodide anion radical and transferred to adjacent Pd NPs.
According to density functional theory (DFT) calculation, this anion radical has longer C−I
bond than neutral phenyl iodide (0.300 nm to 0.214 nm) [20] therefore, the cleavage of
the C−I bond in the oxidative addition step, which is the rate-determining step in the
SMC reaction, will be facilitated. At the same time, the generated-holes, on Pd, are applied
to activate the C−B bond of phenylboronic acid, electronically negative B(OH) −
species by
3
−
obtaining an OH from the basic reaction medium. Hence, simultaneously, phenyl iodide
anion radical is transferred to adjacent Pd nano catalysts and meets activated
phenylboronic acid. As a result, reduced transition energy presumably take places by
perching phenyl iodide anion and phenylboronic acid as two activated reagents on the

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surface of the Pd. Then, the reaction proceed through the transmetalation and reductive
elimination. However, the reaction mechanism is currently under study in our laboratory.
Fig. 4. The proposed reaction mechanism for the SMC reaction.
4. Conclusions
In conclusion, in contrast to prior methods, TiO semiconductor with nearly large band
2
gap (outside the visible light region absorption), using Pd anchoring to it can afford SMC
reaction. After light aborting and generating energetic electrons through LSPR, promotion
of electrons occur by Schottky heterojunctions between Pd nanoparticles and TiO
interface. Activation of substrate may proceed through single electron transfer from CB
of TiO to phenyl halides and transferred to adjacent Pd NPs. Besides, arylboronic acids
2
2
adsorbed on the positively holes of Pd NPs. This heterogeneous photocatalytic as
sufficient light-harvesting catalytic system drives substrate to biaryl compounds in green
solvent under sustainable and mild process condition. So the reaction can proceed at 28
°
C under the irradiation of visible light (> 400 nm). These results can inspire more studies

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of semiconductor with large band gap outside the visible light region that supported
transition metal nanoparticles to apply as photocatalysts for organic synthesis under
visible light.
Acknowledgements
We gratefully thank the support of this work by the Shiraz University Research Council.
This work was financially supported by the Iran National Science Foundation (Grant No.
93046238).

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Graphical abstract

ACCEPTED MANUSCRIPT
Highlights


Plasmatic property and catalytic performance of Pd/TiO
Sustainable condition e.g., using visible light as renewable energy,
2
aqueous media


heterogeneous recycle photocatalyst and ambient temperature were
applied
The first report of the semiconductor with band gap ≥ 3.0 eV for Suzuki
reaction