Redox-selective generation of aldehydes and H2 from alcohols under visible light

Article abstract of DOI:10.1002/chem.201301347

Photosynthetic dehydrogenation: Potential usefulness of visible-light-induced dehydrogenation of alcohols in organic synthesis was demonstrated, in which aldehydes and H₂ were afforded by using Ru/SrTiO₃:Rh and water (see scheme). Water was essential for the reaction. High efficiency (TON: up to 15 400 based on Rh; H₂ and aldehyde evenly generated) and high selectivity were achieved. Copyright

Full text of DOI:10.1002/chem.201301347

DOI: 10.1002/chem.201301347
Redox-Selective Generation of Aldehydes and H2 from Alcohols under
Visible Light
Zijun Liu,[a] Joaquim Caner,[a] Akihiko Kudo,[b] Hiroshi Naka,[a] and Susumu Saito*[c]
Aldehydes and molecular hydrogen (H2) are valuable
chemical substances both in laboratory and industrial syn-
thetic chemistry.[1] Dehydrogenation of primary (18) alcohols
is an ideal, straightforward transformation that affords alde-
hydes and H2 without requiring any external oxidants.
Whereas various methods are available for the dehydrogen-
ation of secondary (28) alcohols to ketones,[2] dehydrogena-
tion of 18 alcohols to aldehydes has remained elusive, pri-
marily due to the instability of aldehydes under the reaction
conditions.[3] For example, homogeneous ruthenium- or iridi-
um-catalyzed acceptorless dehydrogenation frequently
transforms 18 alcohols to carboxylic acid esters.[2f,g,3a–e] Re-
cently, selective thermal (70–1308C) conversions of 18 alco-
hols to aldehydes were achieved,[2b–e,4] yet certain functional
groups, typically, unsaturated carbon–carbon bonds, seem
not to be well tolerated under these reaction conditions.
This nature hampers wide applicability of these methods in
organic synthesis. Importantly, since nonoxidative dehydro-
genation is endergonic and endothermic (DG, DH>0), these
methods require thermal energy input and the removal of
H2 gas from the reaction system to shift the equilibrium to
the right.[4] For instance, conversion of methanol (l) to hy-
drogen (g) and formaldehyde (g) is endergonic (DG8= +
63.7 kJmolÀ1) and endothermic (DH8= +130.1 kJmolÀ1).[5]
The light-mediated photosynthetic catalysis of the selec-
tive transformation of alcohols into aldehydes and H2, may
be a promising approach, in which the thermodynamic cost
of the alcohol dehydrogenation is paid by the energy of sun-
light and thus the dehydrogenation is more spontaneous.[6]
Use of visible light is more desirable for this purpose than
UV light, because the former leaves functional groups in or-
ganic compounds intact, and it accounts for as much as 50%
of the solar energy. Numerous methods for visible-light-pro-
moted oxidation of alcohols by using oxidants, including O2,
have been developed.[7] However, allylic alcohols are de-
composed into smaller carbon pieces, such as acetone or
CO2,[7i] and more importantly, aerobic oxidation of alcohols
to carbonyls is exothermic. Conversion of methanol (l) and
dioxygen (g) to water (l) and formaldehyde (g) is exergonic
(DG8=À173.4 kJmolÀ1)
and
exothermic
(DH8=
À155.7 kJmolÀ1).[5a] Only very recently, visible-light-induced
dehydrogenation of benzyl alcohols to benzaldehydes has
been reported by using Pt/TiO2,[8] CdS,[9] or modified CdS[10]
photocatalysts. Unfortunately, in addition to the moderate
redox- and chemoselectivity in these systems, substrate
scope and scalability are not satisfactory and thus their po-
tential usefulness in organic synthesis remains unclear.
To summarize, a catalytic system able to generate alde-
hydes and H2 from alcohols under mild or ambient condi-
tions without loss of redox-sensitive functional groups
(Figure 1) is lacking.
Figure 1. The dehydrogenation of alcohols promoted by Ru/SrTiO3:Rh
under visible light irradiation, depicted with a schematic representation
of energy changes.
[a] Dr. Z. Liu, Dr. J. Caner, Prof. Dr. H. Naka
Research Center for Materials Science
Nagoya University
Chikusa, Nagoya 464-8602 (Japan)
One of the authors has recently developed a powdered
photocatalyst, SrTiO3:Rh (1% rhodium-doped strontium ti-
tanate), that generates hydrogen under visible-light irradia-
tion in the presence of methanol.[11] Analogously with O2-
evolving photocatalysts for solar irradiation-induced water
splitting,[11d,12] the H2-evolving activity of SrTiO3:Rh in-
creased when ruthenium was added as a cocatalyst (Ru/
SrTiO3:Rh). Herein we demonstrate that Ru/SrTiO3:Rh pro-
motes selective dehydrogenation of alcohols into aldehydes
bearing various functional groups in a closed vessel filled
[b] Prof. Dr. A. Kudo
Department of Applied Chemistry, Faculty of Science
Tokyo University of Science
1-3 Kagurazaka, Shinjyuku, Tokyo 162-8601 (Japan)
[c] Prof. Dr. S. Saito
Graduate School of Science and Institute for Advanced Research
Nagoya University
Chikusa, Nagoya 464-8602 (Japan)
E-mail: saito.susumu@f.mbox.nagoya-u.ac.jp
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201301347.
9452
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 9452 – 9456

COMMUNICATION
Table 1. Conversion of alcohol 1a to aldehyde 2a and dihydrogen under
water (entry 7). Under standard conditions (entry 1), the
powdered photocatalyst was efficiently dispersed in the in-
terface of toluene/H3PO4 aq. biphasic layers (see Supporting
Information, Figure S1). The reaction also proceeded with-
out toluene (entry 8) or with less polar hexane solvent in-
stead of toluene (entry 9). However, polar solvents, such as
dichloromethane and acetonitrile, gave lower yields of 2a
and lower H2 evolution (entries 10–11). The reaction also
proceeded at 58C (entry 12). Preliminary kinetic investiga-
tions suggest that the reaction rate is 0th order with respect
to the concentration of 1a (see the Supporting Information,
Figure S2). As shown in entry 13, reaction without a cut-off
filter produced 108% yield of hydrogen and resulted in a
poor yield of 2a (5%); further, significant amounts of other
products, such as 1,2-di(4-methoxyphenyl)ethanediol (40%),
1-(4-methoxyphenyl)-2-phenylethanol (46%), and 4-me-
thoxybenzoic acid (7%) were formed, presumably due to
UV light emitted from the Xe light source (see the Support-
ing Information, Figure S3). This result clearly indicates the
importance of using visible light rather than UV light for se-
lective chemical transformations.
visible light irradiation.[a]
Yield [%][b]
Entry
Changes from standard conditions
2aH2
92 (89)
<1
2
3
59
56
2
1
2
3
4
5
6
7
none
99
<1
<1
<1
56
without Ru/SrTiO3:Rh
SrTiO3:Rh instead of Ru/SrTiO3:Rh
Pt/SrTiO3:Rh instead of Ru/SrTiO3:Rh
H2O (pH 7.0) instead of H3PO4 aq.
K2CO3 aq. (pH 9.2) instead of H3PO4 aq.
without H3PO4 aq.
55
2
8
9
without toluene
77
68
26
2
60
5
80
67
21
hexane instead of toluene
CH2Cl2 instead of toluene
CH3CN instead of toluene
at 58C
without L42 cutoff filter
without 1a
10
11
12
13
14
<1
55
108[c]
6
–
[a] Reaction conditions: 1a (0.5 mmol), Ru/SrTiO3:Rh (5.3 mg), toluene
(10.0 mL), and H3PO4 aq.(5.0 mL). [b] Yields of aldehyde were deter-
AHCTUNGTRENNUNG
mined by 1H NMR spectroscopic measurements by using 1,1,2,2-tetra-
chloroethane as an internal standard. Yields of H2 were determined by
GC analysis (Agilent 490, MS5A column, argon carrier gas, TCD detec-
tor). Isolated yields are shown in parentheses. [c] Benzoic acid and 1,2-di-
phenylethane were also obtained in an appreciable amount.
With the active and selective photocatalyst in hand, we
next tested the catalytic dehydrogenation of various alcohols
(Table 2). All of these reactions were estimated to be ender-
gonic (DGo (g)= +9–40 kJmolÀ1), based on DFT calcula-
tions at the M06-2X/6-311+ +G** level. All the reactions
were carried out under visible light (l>420 nm) irradiation
in the presence of Ru/SrTiO3:Rh in a toluene/aqueous
H3PO4 system.
with an atmospheric pressure of nitrogen at room tempera-
ture under visible-light irradiation (l>420 nm, Figure 1).
We first tested dehydrogenation of (4-methoxyphenyl)-
The photocatalytic dehydrogenation of benzyl alcohol oc-
curred smoothly to give benzaldehydes 2a–n with high yield
and selectivity, together with evolution of H2 (Table 2, en-
tries 1–14). The Ru/SrTiO3:Rh-catalyzed dehydrogenation
proceeded not only with simple benzyl alcohols 1a and 1b,
but also with benzyl alcohols bearing functional groups, such
as aryl silyl ether (1c), ester (1d), bromo (1e), and trifluoro-
methyl (1 f) groups (entries 1–6). The electron-deficient 4-ni-
trobenzyl alcohol (1g) was less reactive (entry 7). Interest-
ingly, the ketone, olefin, and alkyne moieties in 1h–j were
inert to H2 generated under the reaction conditions in the
closed system, and the dehydrogenation of 1h–j selectively
yielded 4-acetylbenzaldehyde (2h), 4-vinylbenzaldehyde
(2i), and 4-ethynylbenzaldehyde (2j) (entries 8–10). Substi-
tuted benzyl alcohols 1k–m could also be converted to the
corresponding aldehydes 2k–m and H2, and 1m did not un-
dergo oxidation at the electron rich aromatic ring (en-
tries 11–13). Diol 1n was doubly dehydrogenated to give di-
aldehyde 2n with 92% yield and two equivalents of H2
(entry 14). 18 aliphatic alcohol 1o was less reactive than
benzyl alcohols, and aldehyde 2o was obtained in 51% yield
together with carboxylic acid 3o (15%) and H2 (82%,
entry 15).
ACHTUNGTRENNUNGmethACHTUNGTRENNUNGanol (1a) because it and the corresponding product (4-
methoxybenzaldehyde, 2a) can be easily analyzed (Table 1).
To our delight, we found that Ru/SrTiO3:Rh is an excellent
photocatalyst for the selective conversion of 1a to 2a and
H2 under visible-light irradiation in a biphasic system (tol-
uene/H3PO4 aq. v/v=2:1, Table 1, entry 1). 1H NMR spec-
troscopic analysis indicated the formation of 2a with 92%
yield (89% isolated yield). H2 was formed quantitatively
(99% yield with respect to the initial amount of 1a, as de-
termined by a thermal conductivity detector coupled with
gas chromatography (TCD-GC)). The turnover number
(TON) of the photocatalysis based on the amount of Rh
and Ru reached 3,100 and 2,400, respectively (efficient elec-
trons/Rh or Ru). The DG8 (g) of the reaction[4b] was estimat-
ed to be +18.9 kJmolÀ1 by using DFT calculations at the
M06-2X/6-311+ +G** level, which indicates photon energy
transformation to chemical energy during the reaction. The
dehydrogenation is highly selective. Formation of carboxylic
acid through oxidation or disproportionation of 2a, or oxi-
dative condensation of 1a and 2a to an ester was marginal
(<2%, see the Supporting Information, Table S1).
The use of Ru/SrTiO3:Rh was essential, as the reaction
did not proceed in its absence (Table 1, entry 2). SrTiO3:Rh
and Pt/SrTiO3:Rh were ineffective (entries 3 and 4). Water
is required for the reaction. The dehydrogenation proceeded
at both neutral and basic pH values (7.0 and 9.2, entries 5
and 6, respectively) but did not occur in the absence of
The allylic olefins were also preserved under the photoca-
talytic conditions; dehydrogenation of allylic alcohols 1p–r
occurred smoothly, providing enals 2p–r selectively with
moderate to excellent yield (Scheme 1). The achieved che-
moselectivity was significantly higher than that in thermal,
Chem. Eur. J. 2013, 19, 9452 – 9456
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9453

S. Saito et al.
Table 2. Catalytic conversion of benzyl alcohols to benzaldehydes and H2 under visible light irradiation.[a]
acceptorless
dehydrogena-
tion,[2–4] in which olefin func-
tionality is reduced by the co-
AHCTUNGTRENNUNG
Yield [%][b]
Aldehyde
alcohols, 2-decanol (1s), 2-(4-
methoxyphenyl)ethanol (1t), 2-
(2-naphthyl)ethanol (1u), and
cyclooctanol (1v) ( DGo = +
Entry
Alcohol
DGo [kJmolÀ1
]
H2
1[c]
2[d]
3
1a (R=OCH3)
1b (R=H)
1c (R=OSiiPr3)
1d (R=OAc)
1e (R=Br)
1 f (R=CF3)
1g (R=NO2)
1h (R=Ac)
2a (R=OCH3)
2b (R=H)
2c (R=OSiiPr3)
2d (R=OAc)
2e (R=Br)
2 f (R=CF3)
2g (R=NO2)
2h (R=Ac)
>95 (89)
>95
91 (80)
84
>95 (84)
86
42
>95 (86)
63
90
95
88
78
+18.9
+26.9
+17.6
+25.0
+29.0
+34.7
+39.6
+32.3
+23.9
+31.3
23.6,
+8.0,
+30.2,
respectively)
and
+13.8 kJmolÀ1,
took place as well to give 2-dec-
anone (2s), 4’-methoxyaceto-
phenone (2t), 2-acetonaph-
thone (2u), and cyclooctanone
(2v) with 65, 89, 91, and >95%
NMR spectroscopic yields, re-
spectively (H2 evolution: 68, 99,
93, and 90%, respectively).
Overall, the TONs based on the
Rh of the reactions ranged
from 450 to 1,400 under the
above conditions, and these re-
sults indicate wide potential ap-
plicability of the present
method to dehydrogenation of
alcohols without loss of various
functional groups.
The yields of 2a and H2 were
comparable throughout the re-
action, and remained un-
changed when the reaction mix-
ture was left in the dark
(Figure 2). This result clearly
indicates that the formation of
2a and H2 was due to photoca-
talytic dehydrogenation of 1a.
4
77
5[c]
6[c]
7[d]
8
>99
>99
57
98
74
9
10
1i (R=CH=CH2)
1j (R=C CH)
2i (R=CH=CH2)
ꢀ
ꢀ
2j (R=C CH)
98
11
12
13
>95
>95
>95
93
90
97
+35.5
+27.6
+16.4
14[e]
15
>95 (87)
>99
+25.2
51[f]
82
–
[a] Reaction conditions: 1 (0.2 mmol), Ru/SrTiO3:Rh (5.3 mg). [b] Yields of aldehyde were determined by
1H NMR spectroscopic measurements by using 1,1,2,2-tetrachloroethane as an internal standard. Yields of H2
were determined by GC analysis (Agilent 490, MS5A column, argon carrier gas, TCD detector). Isolated
yields are shown in parentheses. [c] Reaction time: 15 h. [d] Reaction time: 18 h. [e] 1n: 0.1 mmol. [f] Deter-
mined by GC analysis. CH3ACHTNUGTRNE(GNU CH2)8CO2H (3o, 15%) was coproduced.
Scheme 1. Ru/SrTiO3:Rh-catalyzed dehydrogenation of allylic alcohols
under visible light. The reaction conditions used for 1p were also applied
for 1q,r. The E/Z ratio was obtained by 1H NMR spectroscopy or GC
analysis.
Figure 2. Yields of 2a (*) and H2 (*) with respect to the initial amount
of 1a in the visible-light-promoted dehydrogenation of 2a by using Ru/
SrTiO3:Rh. The reaction mixture was left in the dark for 4–6 h and 10–
12 h under standard conditions.
9454
www.chemeurj.org
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 9452 – 9456

Redox-Selective Generation of Aldehydes and H2 from Alcohols
COMMUNICATION
Dehydrogenation of 1a was also performed under irradia-
tion with a longer wavelength (Figure 3). The reaction oc-
curred even at a wavelength of around 500 nm, which corre-
sponds to electronic transitions from an Rh3+ electron
donor level to a conduction band of SrTiO3,[11–12] but the
yields of 2a and H2 decreased with increasing wavelength.
The incident-photon-to-dehydrogenation efficiency of Ru/
Experimental Section
Typical procedure for photocatalytic dehydrogenation of alcohols: 4-Me-
thoxybenzylalcohol (1a, 27.6 mg, 0.20 mmol), Ru/SrTiO3: Rh (5.3 mg),
H3PO4 aq. (pH 3.4, 5.0 mL), and toluene (10.0 mL) were added succes-
sively to a cylindrical Pyrex glass reaction vessel (diameter: 50 mm,
height: 130 mm with a top window made of Pyrex) connected to a bal-
loon. Then the vessel was sealed and covered with aluminum foil except
for the top window. After the atmosphere was replaced with nitrogen,
the vessel was immersed in a water bath (kept at 258C by using a cooling
circulator) and was irradiated with a 300 W Xe lamp (Ushio: BA-x300/
ES1 Technology; CERMAX PE300BF) equipped with cold mirror and
cut-off filters (HOYA L42) for 24 h.
Sunlight irradiation: The suspension (1a, 0.05 mmol) was exposed to sun-
light on the roof of the building without stirring from 10:00 am to
6:00 pm on July 18th, 2012, at Nagoya, Japan.
Measurement of quantum yield: Reaction was carried out in a 5.0 mL-
Pyrex glass reaction tube with a top window made of Pyrex (diameter:
10 mm), by using a 300 W Xe lamp (Ushio Technology; CERMAX LX-
300F) equipped with a cut-off filter (HOYA), a band-pass filter (Asahi
Spectra Co. 420 nm), and fiber optics. The number of incident photons
was measured by a photodiode (OPHIR; PD300-UV-ROHS head and
Nova power monitor).)
Figure 3. a) Diffuse reflectance spectrum of SrTiO3:Rh; b,c) Yields of
2a (*) and H2 (*). Conditions: 1a (0.2 mmol), Ru/SrTiO3:Rh (5.3 mg),
toluene/H3PO4 aq. (pH 3.4) v/v=2:1, 258C, 6 h. Light source: 300 W Xe
lamp with cutoff filters at the indicated wavelength.
Acknowledgements
This work was supported by funds from Asahi Glass, Asahi Kasei Chemi-
cals, Kuraray, Mitsubishi Chemical, Mitsui Chemicals, Nissan Chemical
Ind., and Sumitomo Chemical. The authors wish to thank Prof. R.
Noyori (NU & RIKEN) for fruitful discussions and Prof. P. Butko for
technical advice. We are also grateful to T. Noda, H. Natsume, and H.
Okamoto for their support in the production of reaction vessels at NU.
SrTiO3:Rh photocatalyst was around 0.20% at 420 nm with
1a as a substrate, based on the yield of aldehyde 2a (see the
Supporting Information, Figure S4). This value is broadly in
line with those of photocatalytic reactions for H2 evolution
in water/methanol mixtures (5.2%), Z-Scheme water split-
ting (1.7%), and cathodic photocurrent (0.17%).[11–12]
The catalytic activity of Ru/SrTiO3:Rh lasted more than
one week, affording 2a in 43% yield with 92% selectivity
(5 mmol scale), and the Rh-based TON was up to 15,400
(see the Supporting Information, Figure S5). Moreover, the
dehydrogenation of 1a proceeded under sunlight irradiation
for 8 h, affording the aldehyde 2a in 54% yield and H2 in
62% yield (see the Supporting Information, Figure S6). This
result indicates that the Ru/SrTiO3:Rh photocatalyst is a
promising candidate for organic synthesis coupled with hy-
drogen production by using sunlight as a direct energy
source.
In summary, we have discovered a visible-light-mediated
dehydrogenation of alcohols to produce aldehydes and H2 in
a selective fashion by using Ru/SrTiO3:Rh. The dehydrogen-
ation potentially useful for organic synthesis took place at
room temperature in a closed reaction vessel filled with
an atmospheric pressure of nitrogen, while light energy is
transformed into chemical energy. This process is clearly dis-
tinct from typical thermal dehydrogenation of alcohols and
from oxidant-mediated oxidation of alcohols. We believe the
present discovery represents an important step in develop-
ing photosynthetic organic syntheses that utilize sunlight
energy.[13]
Keywords: alcohols
·
aldehydes
·
dehydrogenation
·
heterogeneous photosynthesis · visible light
[1] a) G. Tojo, M. Fernꢁndez, Oxidation of Alcohols to Aldehydes and
Ketones. Basic Reactions in Organic Synthesis Springer, New York,
2010; b) J. D. Holladay, J. Hu, D. L. King, Y. Wang, Catal. Today
2009, 139, 244–260.
[2] a) G. E. Dobereiner, R. H. Crabtree, Chem. Rev. 2010, 110, 681–
703; b) R. Kawahara, K. Fujita, R. Yamaguchi, J. Am. Chem. Soc.
2012, 134, 3643–3646; c) K. Fujita, T. Yoshida, Y. Imori, R. Yama-
guchi, Org. Lett. 2011, 13, 2278–2281; d) R. Kawahara, K. Fujita, R.
Yamaguchi, Angew. Chem. 2012, 124, 12962–12966; Angew. Chem.
Int. Ed. 2012, 51, 12790–12794; e) A. Prades, E. Peris, M. Albrecht,
Organometallics 2011, 30, 1162–1167; f) S. Musa, I. Shaposhnikov, S.
Cohen, D. Gelman, Angew. Chem. 2011, 123, 3595–3599; Angew.
Chem. Int. Ed. 2011, 50, 3533–3537; g) K. Oded, S. Musa, D.
Gelman, J. Blum, Catal. Commun. 2012, 20, 68–70.
[3] a) F. H. A. Bolder, Ind. Eng. Chem. Res. 2008, 47, 7496–7500; b) J.
Zhao, J. F. Hartwig, Organometallics 2005, 24, 2441–2446; c) J.
Zhang, G. Leitus, Y. Ben-David, D. Milstein, J. Am. Chem. Soc.
2005, 127, 10840–10841; d) J. Zhang, E. Balaraman, G. Leitus, D.
Milstein, Organometallics 2011, 30, 5716–5724; e) A. Sølvhøj, R.
Madsen, Organometallics 2011, 30, 6044–6048; f) C. Gunanathan,
L. J. W. Shimon, D. Milstein, J. Am. Chem. Soc. 2009, 131, 3146–
3147.
[4] W. Fang, J. Chen, Q. Zhang, W. Deng, Y. Wang, Chem. Eur. J. 2011,
17, 1247–1256.
[5] a) J. B. Pedley, R. D. Naylor, S. P. Kirby, Thermochemical Data of
Organic Compounds Ed. 2, Chapman & Hall, London, 1986; b) Z.
Chem. Eur. J. 2013, 19, 9452 – 9456
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9455

S. Saito et al.
Jin, Q. Li, X. Zheng, C. Xi, C. Wang, H. Zhang, L. Feng, H. Wang,
Z. Chen, Z. Jiang, J. Photochem. Photobiol. A 1993, 71, 85–96.
[6] a) D. Ravelli, D. Dondi, M. Fagnoni, A. Albini, Chem. Soc. Rev.
2009, 38, 1999–2011; b) R. Noyori, Nat. Chem. 2009, 1, 5–6; c) R.
Noyori, Tetrahedron 2010, 66, 1028; d) T. Kawai, T. Sakata, Nature
1980, 286, 474–476; e) K. Imamura, H. Tsukahara, K. Hamamichi,
N. Seto, K. Hashimoto, H. Kominami, Appl. Catal. A 2013, 450, 28–
33.
[7] a) G. Palmisano, E. Garcꢂa-Lꢃpez, G. Marcꢄ, V. Loddo, S. Yurdakal,
V. Augugliaro, L. Palmisano, Chem. Commun. 2010, 46, 7074–7089;
b) M. Zhang, C. Chen, W. Ma, J. Zhao, Angew. Chem. 2008, 120,
9876–9879; Angew. Chem. Int. Ed. 2008, 47, 9730–9733; c) F. Su,
S. C. Smitha, G. Lipner, X. Fu, M. Antonietti, S. Blechert, X. Wang,
J. Am. Chem. Soc. 2010, 132, 16299–16301; d) S. Higashimoto, K.
Okada, T. Morisugi, M. Azuma, H. Ohue, T. H. Kim, M. Matsuoka,
M. Anpo, Top. Catal. 2010, 53, 578–583; e) N. Zhang, Y. Zhang, X.
Pan, X. Fu, S. Liu, Y. Xu, J. Phys. Chem. C 2011, 115, 23501–23511;
f) D. Tsukamoto, Y. Shiraishi, Y. Sugano, S. Ichikawa, S. Tanaka, T.
Hirai, J. Am. Chem. Soc. 2012, 134, 6309–6315; g) S. Higashimoto,
K. Okada, M. Azuma, H. Ohue, T. Terai, Y. Sakata, RSC Adv. 2012,
2, 669–676; h) A. Tanaka, K. Hashimoto, H. Kominami, J. Am.
Chem. Soc. 2012, 134, 14526–14533; i) N. Zhang, S. Liu, X. Fu, Y.
Xu, J. Mater. Chem. 2012, 22, 5042–5052; j) H. Schmaderer, P. Hilg-
ers, R. Lechner, B. Kçnig, Adv. Synth. Catal. 2009, 351, 163–174;
k) Y. Shiraishi, T. Hirai, J. Photochem. Photobiol. C 2008, 9, 157–
170.
[8] W. Zhai, S. Xue, A. Zhu, Y. Luo, Y. Tian, ChemCatChem 2011, 3,
127–130.
[9] T. Mitkina, C. Stanglmair, W. Setzer, M. Gruber, H. Kisch, B.
Kçnig, Org. Biomol. Chem. 2012, 10, 3556–3561.
[10] T. P. A. Ruberu, N. C. Nelson, I. I. Slowing, J. Vela, J. Phys. Chem.
Lett. 2012, 3, 2798–2802.
[11] a) A. Kudo, Y. Miseki, Chem. Soc. Rev. 2009, 38, 253–278; b) R.
Konta, T. Ishii, H. Kato, A. Kudo, J. Phys. Chem. B 2004, 108, 8992–
8995; c) K. Iwashina, A. Kudo, J. Am. Chem. Soc. 2011, 133, 13272–
13275; d) Y. Sasaki, A. Iwase, H. Kato, A. Kudo, J. Catal. 2008, 259,
133–137; e) S. Kawasaki, K. Akagi, K. Nakatsuji, S. Yamamoto, I.
Matsuda, Y. Harada, J. Yoshinobu, F. Komori, R. Takahashi, M.
Lippmaa, C. Sakai, H. Niwa, M. Oshima, K. Iwashina, A. Kudo, J.
Phys. Chem. C. 2012, 116, 24445–24448; f) S. Kawasaki, K. Nakatsu-
ji, J. Yoshinobu, F. Komori, R. Takahashi, M. Lippmaa, K. Mase, A.
Kudo, Appl. Phys. Lett. 2012, 101, 033910; morphology and DRS
images of Ru/SrTiO3:Rh before and after its usage, and its energy
band gap between valence and conduction bands are shown in
refs. [11b, d, and e].
[12] a) Y. Sasaki, H. Nemoto, K. Saito, A. Kudo, J. Phys. Chem. C 2009,
113, 17536–17542; b) A. Kudo, MRS Bull. 2011, 36, 32–38.
[13] Primary results of this report were used in application for a patent:
R. Noyori, S. Saito, H. Naka, Z. Liu, J. Caner, A. Kudo, JP patent,
Appl. #2012–181888, Filed: Aug 20, 2012.
Received: April 10, 2013
Published online: June 5, 2013
9456
www.chemeurj.org
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 9452 – 9456