Yin and Yang Dual Characters of CuOx Clusters for C-C Bond Oxidation Driven by Visible Light

Article abstract of DOI:10.1021/acscatal.7b00629

Selective cleavage of C-C bonds is pursued as a useful chemical transformation method in biomass utilization. Herein, we report a hybrid CuO_x/ceria/anatase nanotube catalyst in the selective oxidation of C-C bonds under visible light irradiation. Using the lignin β-1 model as a substrate offers 96% yields of benzaldehydes. Characterization results by high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray spectroscopy element (EDX) mapping reveal that CuO_x clusters are highly dispersed on the exposed anatase surface as well as on the nanosized ceria domains. In-depth investigations by Raman and ultraviolet visible diffuse reflectance spectra (UV-vis DRS), together with density functional theory (DFT) calculations, further verify that the CuO_x clusters present on the ceria domains increase the concentration of surface defects (Ce³⁺ ions and oxygen vacancies) and accordingly improve the photocatalytic activity (Yang character); the CuO_x clusters decorating on anatase suppress the side reaction (oxy-dehydrogenation without C-C bond cleavage) because of an upward shift in the valence band (VB) edge of anatase (Yin character). Mechanism investigation indicates hydrogen abstraction from β-carbon by photogenerated holes is a vital step in the conversion.

Full text of DOI:10.1021/acscatal.7b00629

Subscriber access provided by HACETTEPE UNIVERSITESI KUTUPHANESI
Article
Yin and Yang Dual Characters of CuOx Clusters
for C–C Bond Oxidation Driven by Visible Light
Tingting Hou, Nengchao Luo, Hongji Li, Marc Heggen, Jianmin Lu, Yehong Wang, and Feng Wang
ACS Catal., Just Accepted Manuscript • Publication Date (Web): 24 Apr 2017
Downloaded from http://pubs.acs.org on April 24, 2017
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
ACS Catalysis is published by the American Chemical Society. 1155 Sixteenth Street
N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 28
ACS Catalysis
1
2
3
4
5
6
Yin and Yang Dual Characters of CuOx Clusters for C–C Bond
Oxidation Driven by Visible Light
7
8
9
Tingting Hou,a,b Nengchao Luo,a,b Hongji Li,a,b Marc Heggen,c Jianmin Lu,a Yehong Wang,a and
Feng Wang*a
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
a State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, Dalian Institute
of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, P. R. China
b University of Chinese Academy of Sciences, Beijing 100049, P. R. China
c Ernst Ruska Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg
Institute, Forschungszentrum Juelich GmbH, Juelich 52425, Germany
*Corresponding author: Feng Wang
Tel: +86ꢀ411ꢀ84379762; Fax: +86ꢀ411ꢀ84379798
Eꢀmail: wangfeng@dicp.ac.cn
1
ACS Paragon Plus Environment

ACS Catalysis
Page 2 of 28
1
2
3
4
ABSTRACT
5
6
7
8
9
Selective cleavage of C–C bond is pursued as a useful chemical transformation
method in biomass utilization. Herein, we report a hybrid CuOx/ceria/anatase
nanotubes catalyst in the selective oxidation of C–C bond under visible light
irradiation. Using lignin βꢀ1 model as substrate offers 96% yields of benzaldehydes.
Characterized results by high angle annular dark fieldꢀscanning transmission electron
microscopy (HAADFꢀSTEM) and energyꢀdispersive Xꢀray spectroscopyꢀelement
(EDX) mapping reveal that CuOx clusters are highly dispersed on the exposed anatase
surface as well as on the nanosized ceria domains. Inꢀdepth investigations by Raman,
and ultravioletꢀvisible (UVꢀvis) spectroscopy, together with density functional theory
(DFT) calculation further verify the CuOx clusters present on the ceria domains
increase the concentration of surface defects (Ce3+ ions and oxygen vacancies) and
accordingly improve the photocatalytic activity (Yang character); the CuOx clusters
decorating on anatase suppress the side reaction (oxyꢀdehydrogenation without C–C
bond cleavage) because of upward shifting the valence band (VB) edge of anatase
(Yin character). A hydrogenꢀabstraction from βꢀcarbon by photogenerated holes is a
vital step in the conversion.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
KEYWORDS: heterogeneous catalysis, visible light, ceria, copper, titania, C–
C bond, benzaldehyde
2
ACS Paragon Plus Environment

Page 3 of 28
ACS Catalysis
1
2
3
4
INTRODUCTION
5
6
7
8
Selective oxidation of C–C bond is a significant process to produce oxygenates.1
As an alternative and sustainable feedstock, lignin accounts for around 30% weight of
lignocellulosic biomass.2 The presence of C–C bond is one of the reasons for lignin’s
recalcitrance to be converted into monomers. As a typical C–C bond, the βꢀ1 linkage
connects two phenyl groups by replacement of the Oꢀbound phenoxy unit with a
Cꢀbound aryl group (Scheme 1). Baker and Hanson et al. have reported the cleavage
of βꢀ1 bond over a copper (I) trifluoromethanesulfonate catalyst assisted by 10 mol %
of 2,2,6,6ꢀtetramethylꢀ1ꢀpiperidinyloxy (TEMPO) and 10 equivalent of 2,6ꢀlutidine.3
Shi’s group has developed a protocol to fragment lignin βꢀ1 models using sodium
persulfate as oxidant at 100 °C.4 Very recently, our group has reported a
Cu(OAc)2/BF3·OEt2 catalytic system for C–C bond cleavage in βꢀ1 ketones.5
However, a facile and efficient catalytic system that can achieve the lignin βꢀ1 C–C
bond cleavage is desired but far less developed.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Photocatalytic process holds great promise to reduce the energy consumption in
organic reactions6 and has attracted broad interests.7 It will be of significance to
realize the photolysis of lignin into monomers under mild conditions.8 When C–C
bond is a targeted linkage to be cleaved, the activation of the Cβ–H bond is a requisite
(Scheme 1).9 But once the C–OH bond is converted to a ketone via
oxyꢀdehydrogenation, the Cα–Cβ bond dissociation energy (BDE) increases from
294.7 to 354.2 kJ/mol, and consequently the formed ketone is more difficult to be
converted. This is different with the cleavage of βꢀOꢀ4 bond that is easier to be
3
ACS Paragon Plus Environment

ACS Catalysis
Page 4 of 28
1
2
3
4
5
6
7
8
9
cleaved once the C–OH bond is preꢀoxidized to ketone.8a, 10 Thus, a highly selective
catalyst to oxidize βꢀ1 C–C bond should selectively activate Cβ–H bond but suppress
the formation of ketone. This has been rarely achieved in heterogeneous
photocatalysis.11
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 1. Oxyꢀdehydrogenation reaction competes with C–C cleavage reaction in the
oxidation of βꢀ1 model.
We herein report the bifunctionality of CuOx clusters in the photolysis of C–C
bond, especially in lignin βꢀ1 model. Catalytic results show that decoration of CuOx
clusters on ceria/anatase significantly promotes the C–C bond cleavage with 98%
selectivity of benzaldehyde under visible light. The reaction mechanism involves a
hydrogen abstraction from a benzylic carbon (βꢀC) process by the photogenerated
holes, which is supported by control experiments and kinetic isotope effects (KIE)
investigations. Detailed studies, including Xꢀray diffraction (XRD), HAADFꢀSTEM,
EDXꢀmapping, physical absorption, Raman, and UVꢀvis spectroscopy as well as DFT
calculation reveal that the highly dispersed CuOx clusters have dual characters on both
4
ACS Paragon Plus Environment

Page 5 of 28
ACS Catalysis
1
2
3
4
5
6
7
8
9
ceria domains and exposed anatase nanotubes, i.e. promoting the C–C bond cleavage
(Yang character), and inhibiting unwanted oxyꢀdehydrogenation reaction (Yin
character).12 This study attains selective C–C bond oxidation to benzaldehydes,
particularly in the presence of competitive ketone formation reaction, using
photoenergy by controlling the decoration location of CuOx clusters. Although copper
catalysts have been known in activating C–C bonds,9b such dual characters of CuOx
clusters in heterogeneous catalysis are very rare.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
EXPERIMENTAL SECTION
Chemicals and materials
All chemicals were of analytical grade, purchased from Aladdin Chemicals Co.
Ltd. (Shanghai, China), and used without further purification.
Catalysts preparation
TiO2 nanotubes were synthesized by a hydrothermal approach, which has been
described in detail elsewhere.13 Briefly, 5 g of TiO2 (anatase) powder was dispersed in
70 mL of 10 M NaOH under stirring. The mixture was then transferred into a 150 mL
Teflonꢀlined autoclave. The autoclave was then sealed and placed at a preheated oven
at 140 °C for 20 h. The precipitated powder was filtered and washed with 0.1 M
HNO3 and deionized water for several times until the filtrate solution became neutral.
Then it was airꢀdried at 105 °C overnight. The resulting product was denoted as
AꢀNTs. The rutile nanotubes (RꢀNTs) and P25 nanotubes (PꢀNTs) were prepared by
the same procedure.
5
ACS Paragon Plus Environment

ACS Catalysis
Page 6 of 28
1
2
3
4
5
6
7
8
9
The ceria sample was prepared by a conventional precipitation method reported
by our group.14 Briefly, 5.0 g of Ce(NO3)3·6H2O was dissolved in 100 mL of
Milliporeꢀpurified water (18 mꢁ·cm), and the solution was adjusted to pH = 10.0 by
the addition of NH3·H2O under magnetic stirring at room temperature. The resulting
gel mixture was washed with pure water, dried in an oven at 120 °C overnight, and
calcined at 400 °C in air for 6 h.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For ceria/AꢀNTs, CuOx/AꢀNTs and CuOx/ceria/AꢀNTs nanocomposites, a
wetꢀchemical deposition precipitation (DP) method was employed. The preparation
procedure was as follows: 0.87 g of Ce(NO3)3·6H2O was dissolved in 100 mL of
Milliporeꢀpurified water, and mixed with 1.6 g of the asꢀprepared anatase nanotubes.
Sufficient NH3·H2O (wt %: 25%−28%) was then added under vigorous stirring to
adjust the pH to 10. After that, this mixture was stirred again for 5 h and then aged for
4 h without stirring at room temperature. The resulting product was filtered, dried at
105 °C overnight and calcined at 400 °C for 2 h to generate ceria/AꢀNTs. Other TiO2
supported catalysts, such as CuOx/AꢀNTs, CuOx/ceria/AꢀNTs, ceria/RꢀNTs and
ceria/PꢀNTs were prepared by the same wetꢀchemical DP method. Note that, for all of
the catalysts, the molar ratios of Ce/Ti, Cu/Ce and Cu/Ti were 1:10, 1:4 and 1:40,
respectively.
Catalyst characterizations
Powder Xꢀray diffraction patterns were conducted on a PANalytical XꢀPert PRO
diffractometer, using CuꢀKα radiation at 40 kV and 20 mA. Continuous scans were
collected in the 2θ range of 10ꢀ80°.
6
ACS Paragon Plus Environment

Page 7 of 28
ACS Catalysis
1
2
3
4
5
6
7
8
9
Scanning transmission electron microscopy (STEM) was performed using a FEI
Titan 80ꢀ200 (ChemiSTEM) electron microscope operated at 200 kV, equipped with a
sphericalꢀaberration (Cs) probe corrector (CEOS GmbH), and a highꢀangle annular
dark field (HAADF) detector. A probe semiꢀangle of 25 mrad and an inner collection
semiꢀangle of the detector of 88 mrad were used. Compositional maps were obtained
with energyꢀdispersive Xꢀray spectroscopy (EDX) using four largeꢀsolidꢀangle
symmetrical Si drift detectors. For EDX analysis, Cu K, Ti K, and Ce L peaks were
used. High resolution transmission electron microscopy (HRTEM) investigations
were performed using an FEIꢀTitan 80ꢀ300 electron microscope equipped with a Cs
corrector for the objective lens. The microscope was operated at a voltage of 300 kV
using the negativeꢀCs imaging technique (NCSI, with Cs set at around ~13 ꢂm and
defocus around +6 nm).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
The BrunauerꢀEmmetꢀTeller (BET) surface area, total pore volume, and average
pore sizes of sample were measured by N2 adsorption and desorption on a Quadrasorb
SI instrument (Quantachrome, USA) at liquid nitrogen temperature (77.3 K). Before
measurement, the sample was degassed under vacuum condition at 300 °C for 5 h.
The BET specific surface area was calculated from the adsorption data in the relative
pressure range between 0.05 and 0.30.
Raman spectra were recorded on a confocal microscopic Raman spectrometer
(Bruker Optics Senterra) using a laser with the wavelength of 532 nm.
UVꢀVis diffuse reflectance spectra were recorded on JASCO Vꢀ550 UVꢀVis
spectrophotometer.
7
ACS Paragon Plus Environment

ACS Catalysis
Page 8 of 28
1
2
3
4
Photocatalytic activity tests
5
6
7
8
Photocatalytic aerobic oxidation reaction was carried out in a homemade LED
photoreactor. Typically, 0.05 mmol of 1,2ꢀdiphenylethanol (substrate 1) and 10 mg of
photocatalyst were added to 1 mL of solvent in a 4 mL quartz tube. The system was
replaced with O2 for 1 min before it was sealed with a ground glass stopper and
Parafilm. The quartz tube was then irradiated with 455 nm LED light. The conversion
of 1,2ꢀdiphenylethanol and yield of benzaldehyde (1a) were determined by gas
chromatography (GC) with nꢀdodecane as the internal standard. CAUTIOUS! Specific
protection by wearing eye goggle of shielding 455 nm light is mandatory to avoid
injuring eyes.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Computational method of PEDOS
All the firstꢀprinciples electronic structure calculations were carried out using the
Vienna ab initio simulation package (VASP),15 one density functional theory
implementation. The exchange correlation potential was described by the
PerdewꢀBurkeꢀErnzerhof (PBE)16 formulation of the generalized gradient
approximation (GGA). The ionꢀelectron interactions were represented by the projector
augmentedꢀwave (PAW)17 method, while the valence electrons (2s22p4 of O,
3s23p63d24s2 of Ti, and 3d104s of Cu) were expanded by a plane wave basis set with
an energy cutoff of 400 eV. The kꢀpoint sampling was performed using the Monkhorst
Pack scheme.18 The electronic selfꢀconsistent minimization was converged to 10−5 eV
and the geometry optimization was converged to 10–4 eV. The selfꢀinteraction error
(SIE) was mitigated using the DFT+U method by Dudarev and his colleagues.19
A
8
ACS Paragon Plus Environment

Page 9 of 28
ACS Catalysis
1
2
3
4
typical U value of 4.5 eV was used for Ti.
5
6
7
8
9
The lattice constants of anatase TiO2 were optimized to be a=3.855 Å and
c=9.661 Å, in good agreement with the experimental one, a=3.782 Å and c=9.502
Å.20 We used it to build a p(2×4) TiO2(101) slab with 12 atomic layers and a vacuum
of 15 Å. Atoms in the bottom 6 atomic layers were fixed to their bulk positions while
the rest were allowed to fully relax. A 4×3×1 kꢀpoint mesh was used.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Computational method of BDE
The Vienna Ab Initio Package (VASP)21 was employed to perform spinꢀpolarized
DFT calculations within the generalized gradient approximation (GGA) using the
PBE22 functional formulation. The ionic cores were described by the projected
augmented wave (PAW) pseudopotentials.23 1s of H, 2s22p2 of C, and 2s22p4 of O
electrons were explicitly taken into account using a plane wave basis set with an
energy cutoff of 400 eV. Partial occupancies of the Kohn−Sham orbitals were allowed
using the Gaussian smearing method and a width of 0.05 eV. All the molecules and
radicals after bond cleavage are put separately and relaxed fully in a cubic box with a
side length of 20 Å. Brillouin zone integration was performed using a 2×2×2
MonkhorstꢀPack grid. The electronic energy was considered selfꢀconsistent when the
energy change was 10−7 eV. A geometry optimization was considered convergent
when the energy change was 10ꢀ6 eV.
RESULTS AND DISCUSSION
Photocatalytic oxidation of lignin βꢀ1 model
9
ACS Paragon Plus Environment

ACS Catalysis
Page 10 of 28
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 1. The photocatalytic activity of different photocatalysts for oxidation of substrate 1.
Reaction conditions: substrate 1 (0.05 mmol), catalyst (10 mg), CH3CN (1.0 mL), O2 (1 atm), 9.6
a
b
W LED (centered at 455 nm), room temperature, 5 h. With 1b as substrate. The reaction time
c
was 10 h. The reaction was conducted in the dark. The conversion and the yields were
determined by GC with nꢀdodecane as the internal standard.
We firstly explored the oxidation of 1,2ꢀdiphenylethanol under 455 nm visible
light irradiation (Figure 1). The reaction did not proceed in the absence of catalyst.
Pristine ceria exhibited moderate activity towards C–C bond cleavage of βꢀ1 lignin
model under visible light and gave 35% conversion of substrate 1 with 98%
selectivity of C–C bond cleavage. Photocatalytic activity of ceria depends on the
concentration of surface defect sites (Ce3+ ions and O vacancies).24 Tuning the surface
defects could tailor the photoꢀreactivity of ceria catalysts.25 Aiming at achieving
defected ceria, we dispersed ceria on anatase nanotubes (AꢀNTs) by
10
ACS Paragon Plus Environment

Page 11 of 28
ACS Catalysis
1
2
3
4
5
6
7
8
9
depositionꢀprecipitation (DP) method with a Ce:Ti molar ratio of 1:10. The
asꢀprepared ceria contained abundant Ce3+ and oxygen vacancy at the exposed
interface of ceria and anatase.13b Expectedly, the conversion of 1 over ceria/AꢀNTs
reached 57%. Benzaldehyde was the major product. But such a catalyst showed 37%
selectivity of oxyꢀdehydrogenation to diphenylethanone (1b), indicating the
ceria/AꢀNTs catalyst has oxyꢀdehydrogenation ability. Employing diphenylethanone
(1b) as substrate gave no benzaldehyde, inferring the oxyꢀdehydrogenation reaction to
ketone is parallel to the C–C cleavage reaction to benzaldehyde. Replacing anatase
nanotubes support by rutile and P25 nanotubes slightly decreased conversion but
could not increase selectivity.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
In order to increase benzaldehyde selectivity, the parallel oxyꢀdehydrogenation
reaction should be suppressed. Previous studies have shown the modification with
copper oxides could alter the photocatalytic activity of TiO2.26 On the other hand, the
copperꢀbased catalysts are favorable for thermal oxidative cleavage of C–C bond
reported by other groups and ours.1d, 9b, 27 So we prepared a catalyst by mixing copper
and cerium salt precursors and precipitating them on AꢀNTs by the DP method, named
as CuOx/ceria/AꢀNTs (2 wt% CuO loading relative to ceria/AꢀNTs) for this reaction.
The conversion of substrate 1 increased to 75% and surprisingly with 98% selectivity
of benzaldehyde. Extension of the reaction time to 10 h realized complete conversion
of substrate 1 with > 99% selectivity of benzaldehyde. The oxyꢀdehydrogenation
reaction was almost completely suppressed. Control reactions using AꢀNTs and
CuOx/AꢀNTs as catalysts under the same conditions gave no product,28 indicating
11
ACS Paragon Plus Environment

ACS Catalysis
Page 12 of 28
1
2
3
4
5
6
ceria plays a key role in this photocatalytic system. Moreover, it is a photocatalytic
reaction and didn’t occur in the dark.
7
8
9
We then investigated the photoꢀoxidation of a more complex βꢀ1 model
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1ꢀ(3,4ꢀdimethoxyphenyl)ꢀ2ꢀ(4ꢀmethoxyphenyl)ꢀpropaneꢀ1,3ꢀdiol (substrate 2) with
γ
ꢀhydroxyl and methoxyl substituents (Scheme 2). The cleavage of C–C bond offered
96% yield of veratraldehyde and >99% yield of anisic aldehyde even in the presence
of –hydroxyl and methoxyl groups. The Cu/substrate ratio and temperature of
γ
reaction are lower and the yields of aromatic aldehydes are higher than using
homogeneous copper catalyst.3
Scheme 2. Photocatalytic C–C bond cleavage of nonphenolic lignin model substrate 2 to
aromatic aldehydes over CuOx/ceria/AꢀNTs
Reaction conditions: substrate 2 (0.05 mmol), CuOx/ceria/AꢀNTs (10 mg), CH3CN (1.0 mL), O2 (1
atm), 9.6 W LED (centered at 455 nm), room temperature, 24 h. The yields of aldehydes were
determined by GC with nꢀdodecane as the internal standard.
XRD and TEM characterization of the photocatalysts
Such unexpected results motivated us to investigate the structure of the catalysts.
XRD diffraction patterns of the asꢀprepared ceria and AꢀNTs are dominated by the
12
ACS Paragon Plus Environment

Page 13 of 28
ACS Catalysis
1
2
3
4
5
6
7
8
9
expected lines for fcc fluorite CeO2 (JCPDS: 34ꢀ0394) and anatase (JCPDS: 21ꢀ1272),
respectively (Figure 2). The characteristic peaks of crystalline ceria are not observed
except for a weak and broad peak at 28.6° for ceria/AꢀNTs and CuOx/ceria/AꢀNTs. It
is well accepted that if the size of crystalline particles is smaller than 4 nm, their
diffraction peaks will be significantly broadened or even absent.29 Therefore, the
disappearance of ceria diffraction peaks is due to the high dispersion of ceria. After
CuOx was decorated onto ceria/AꢀNTs or AꢀNTs (2 wt% respective to ceria/AꢀNTs),
no extra diffraction lines attributed to CuOx were observed, indicating the high
dispersion of CuOx.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ceria
A-NTs
ceria/A-NTs
CuOX/ceria/A-NTs
CuOx/A-NTs
Cu2O-JCPDS: 35-1091
CuO-JCPDS: 44-0706
ceria-JCPDS: 34-0394
anatase-JCPDS: 21-1272
10
20
30
40
50
60
70
80
2 theta (degree)
Figure 2. XRD patterns of ceria, AꢀNTs, ceria/AꢀNTs, CuOx/ceria/AꢀNTs, and CuOx/AꢀNTs
photocatalysts, respectively.
To investigate the microstructure of the photocatalysts, HRTEM, HAADFꢀSTEM,
EDXꢀmapping, and fast Fourier transform (FFT) characterizations were then carried
13
ACS Paragon Plus Environment

ACS Catalysis
Page 14 of 28
1
2
3
4
5
6
7
8
9
out (Figure 3 and Figure S1). The asꢀprepared anatase sample has a nanotube structure
with outer and inner diameters of about 10 nm and 6.5 nm, respectively (Figure S1a).
The CuOx/ceria/AꢀNTs consists of uniform and wellꢀdispersed nanoparticles on the
ridged surface of the anatase nanotubes. A comparison between the highꢀresolution
STEM image (Figure 3 d) and the EDX maps confirms that the bright dots are ceria
nanoparticles. The size of the ceria ranged from 2 to 8 nm with an average diameter of
4.3 nm (Figure S1 and Figure 3). The FFT image in Figure 3b displays the interplanar
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
d
ꢀspacings for CeO2 (d111 = 0.31 nm), TiO2 (d101 = 0.35 nm), Cu2O (d200 = 0.21 nm),
and CuO (d200 = 0.23 nm and d110 = 0.28 nm) (Figure 3c), respectively. The STEM
images and EDX mappings (Figure 3 and Figure S1d) confirm that Ce and Cu are
highly dispersed on the CuOx/ceria/AꢀNTs substrate. Furthermore, the EDX maps
(Figure 3eꢀi) show that the CuOx clusters are very finely dispersed and associated to
both ceria nanoparticles and the naked anatase nanotubes. The BET surface areas and
pore volume measurements by nitrogen adsorption and desorption are also conducted
(Table S1). Both BET surface areas and pore volume only have a slight decline for
ceria/AꢀNTs and CuOx/ceria/AꢀNTs compared with AꢀNTs, indicating that most of
ceria and CuOx are present on the exterior surface of the nanotubes.
14
ACS Paragon Plus Environment

Page 15 of 28
ACS Catalysis
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 3. Lowꢀ (a) and highꢀresolution (b) HAADFꢀSTEM images (c) Fast Fourier transform of
image (b), (d) Highꢀresolution HAADFꢀSTEM image and corresponding (eꢀi) EDX maps of
CuOx/ceria/AꢀNTs.
Investigation of the reaction mechanism
Next, we turned our attention to elucidate the reaction mechanism. Effects of
reaction atmosphere and trapping agents were explored to discover the key active
species that oriented the reaction path (Figure 4). When the reaction was conducted in
air, the yield of benzaldehyde slightly declined to 60% (Figure 4b). Moreover, the
yield decreased to 9% under Ar (Figure 4c), indicating oxygen is necessary.
According to previous studies, molecular oxygen could be activated to a superoxide
anion radical after acquiring an excited electron from the conduction band of a
15
ACS Paragon Plus Environment

ACS Catalysis
Page 16 of 28
1
2
3
4
5
6
7
8
9
photocatalyst.30 Adding one equivalent amount of superoxide anion radical scavenger
pꢀbenzoquinone (BQ)30a decreased the benzaldehyde yield to < 1% (Figure 4d),
inferring this is a possible radical reaction.30 Adding ammonium oxalate (AO)30a to
capture photogenerated holes could reduce benzaldehyde yield to 1% (Figure 4e).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
30a
Adding K2S2O8 to capture photogenerated electrons also led to the low yield of
benzaldehyde (6%) (Figure 4f). The above results suggest that photoexcited electrons,
holes and superoxide anion radical are essential species for the reaction.
Figure 4. Influence of the reaction atmosphere and scavenger. Reaction conditions: substrate 1
(0.05 mmol), CuOx/ceria/AꢀNTs (10 mg), CH3CN (1.0 mL), reaction pressure (1 atm), additive
(0.05 mmol), 9.6 W LED (centered at 455 nm), room temperature, 5 h. The yield of 1a was
determined by GC with nꢀdodecane as the internal standard. (a and dꢀf) Reaction under O2. (b)
Reaction under Air. (c) Reaction under Ar. (d) Reaction with pꢀbenzoquinone as scavenger for
superoxide radical. (e) Reaction with (NH4)2C2O4 as the scavenger for photogenerated holes. (f)
Reaction with K2S2O8 as the scavenger for photogenerated electrons.
16
ACS Paragon Plus Environment

Page 17 of 28
ACS Catalysis
1
2
3
4
5
6
7
8
9
Diphenylethanone (1b) could be oxidized to ester via C–C bond cleavage using
Cu(OAc)2/BF3·OEt2 catalyst.5 In this study, diphenylethanone could not be converted
into benzaldehyde using the CuOx/ceria/AꢀNTs catalyst (Scheme 3, Eq. 1). The results
show the oxyꢀdehydrogenation of 1 to 1b competes with the C–C cleavage reaction.
Furthermore, we investigated the H/D KIE of the reaction (Scheme 3). When 1ꢀD or
1'ꢀD was used as substrate, the secondary kinetic isotope effect with kH/kD values of
1.44 and 1.23, respectively, was observed, indicating that the cleavage of O–H bond
or Cα−H is not a rateꢀdetermining step (Scheme 3, Eq. 2ꢀ3). Notably, when using 1'ꢀD
as substrate, nearly half of benzaldehyde was deuterated (Scheme 3, Eq. 3). Further
experiments showed benzaldehyde could not undergo H/D exchange with 0.5
equivalent deuterated water under reaction conditions (Scheme 3, Eq. 4). These
results demonstrate that Cα–H bond connecting with the hydroxyl group was retained
during the C–C bond cleavage. Additionally, a firstꢀorder KIE with a value of 6.53
was observed for 1''ꢀD (Scheme 3, Eq. 5), implying the Hꢀabstraction from βꢀC is
involved in the C–C bond cleavage of substrate 1. Oxidation of 1 to 1a and 1b is
distinguished based on an initial hydrogen abstraction reaction at one of two positions
(αꢀC and βꢀC). A benzylic radical is generated at αꢀC or βꢀC, which is
resonanceꢀstabilized by aromatic ring.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
17
ACS Paragon Plus Environment

ACS Catalysis
Page 18 of 28
1
2
3
4
Scheme 3. Control experiment and kinetic isotope effects (KIE)
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Based on the above results, we propose a tentative reaction mechanism involving
hydrogen abstraction at α or β position as depicted in Scheme 4. Photogenerated
electron is transferred to O2, producing a superoxide anion radical. The hole abstracts
a hydrogen from βꢀC to generate Cβꢀcentered radical. The superoxide anion radical
then adds to Cβꢀcentered radical forming an unstable peroxide intermediate. The latter
will undergo Cα–Cβ cleavage with the elimination of H2O to form benzaldehyde
through the sixꢀmembered ring transition state (white and upper cycle). Alternatively,
a radical generated at αꢀC will produce the diphenylethanone 1b (dark and lower
cycle).
18
ACS Paragon Plus Environment

Page 19 of 28
ACS Catalysis
1
2
3
4
5
6
Scheme 4. Possible mechanism.
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
The role of the CuOx clusters on the reaction
Furthermore, we studied the role of the CuOx clusters on the reaction. Previous
theoretical calculations and experimental studies have suggested that the
photocatalytic performance of ceria is associated with the surface oxygen vacancies
and Ce3+ ions.25b, 31 Copper oxides could increase surface oxygen vacancies and Ce3+
ions of ceria in the case of CuOx/CeO2.32 Ce3+ ions are generated by reducing Ce4+
ions when the oxygen vacancy is created.33 The concentration of surface oxygen
vacancies can be semiꢀquantified by Raman spectroscopy.14, 34 We adopted a method35
by using the Raman peak centered at 462 cm−1 to estimate the oxygen vacancy
concentration of ceria. The results were presented in Figure 5b. The oxygen vacancy
concentration of pristine ceria is 3.58 × 1021 cm−3. A higher value of 5.88 × 1021 cm−3
19
ACS Paragon Plus Environment

ACS Catalysis
Page 20 of 28
1
2
3
4
5
6
7
8
9
is obtained when ceria is highly dispersed in nanosized domains on anatase nanotubes.
More oxygen vacancy (6.04 × 1021 cm−3) is generated after mixing copper oxide with
ceria.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 5. Raman spectra (a) and the oxygen vacancy concentration (b) of the photocatalysts.
Next we measured the UVꢀvis spectra to study the optical properties of
photocatalysts (Figure 6). AꢀNTs have no significant absorption of visible light owing
to its large energy gap. However, the addition of ceria extends the absorption of the
resulting catalysts to visible light, which was also observed by other studies.31a, 31b
This visible absorption enhancement could be attributed to the existence of oxygen
vacancies and Ce3+ ions. The positive correlation between absorption at 455 nm and
the concentration of oxygen vacancies and Ce3+ ions for ceriaꢀbased photocatalysts
further confirms this point (Figure 6a). The calculated band gaps of the asꢀprepared
samples using the transformed KubelkaꢀMunk plot are shown in Figure 6b.36 The
optical band energies of ceria/AꢀNTs and CuOx/ceria/AꢀNTs are calculated to be 2.72
eV and 2.62 eV, respectively, which are lower than that of pristine ceria (2.86 eV).
The presence of Ce3+ leads to the narrowing of the band gap of ceria. The CuOx
20
ACS Paragon Plus Environment

Page 21 of 28
ACS Catalysis
1
2
3
4
5
6
7
8
9
clusters present on the ceria domains increase the concentration of surface defects
(Ce3+ ions and oxygen vacancies), which we term its Yang character. For CuOx/AꢀNTs,
the band gap is 2.58 eV, lower than that of AꢀNTs. This result suggests copper oxide
electronically modifies anatase nanotubes, which agrees with XRD, STEM and
Raman spectroscopy results.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 6. (a) UV–vis diffuse reflectance spectra and (b) the optical adsorption edges of the ceria,
AꢀNTs, ceria/AꢀNTs, CuOx/AꢀNTs and CuOx/ceria/AꢀNTs photocatalysts, respectively.
CuOx/AꢀNTs showed no photocatalytic activity towards the C–C bond cleavage.
We then conducted a photocatalytic reaction under 365 nm UV light (Figure 7), under
which electronꢀhole pairs of AꢀNTs can be excited. Consequently, the 50% yield of 1b
is obtained, together with 30% yield of 1a, indicating both C–C bond cleavage and
oxyꢀdehydrogenation reactions occur on anatase. Because ceria has no photocatalytic
ability of oxyꢀdehydrogenation, it is very likely that the oxyꢀdehydrogenation reaction
mainly occurs on AꢀNTs. The decoration of copper oxides on AꢀNTs can remarkably
suppress the side reaction, decreasing yield of 1b to 4%, which we term Yin character
21
ACS Paragon Plus Environment

ACS Catalysis
Page 22 of 28
1
2
3
4
5
6
7
8
9
of CuOx clusters. We further compare the activities of the ceria/AꢀNTs and
CuOx/ceria/AꢀNTs under 365 nm UV light. The yield of 1a increases from 32% to 43%
and the yield of 1b declines from 20% to 5%, which further confirms the Yin (inhibit
the side oxyꢀdehydrogenation reaction) and Yang (enhance the C–C cleavage activity)
dual characters of the CuOx. Tada’s group has observed that with the increasing
loading amount of NiOx or CuOx nanoclusters on TiO2, the activity of
photodegradation of organics decreased.26a, 37 In this work, we find the photocatalytic
oxyꢀdehydrogenation reaction on anatase fades away with increasing the amount of
CuOx to 2 wt% (Table S2).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 7. Photocatalytic reaction under UV light. Reaction conditions: substrate (0.05 mmol),
catalyst (10 mg), CH3CN (1.0 mL), O2 (1 atm), 6 W LED (centered at 365 nm), room temperature,
5 h. The yields were determined by GC with nꢀdodecane as the internal standard.
To further understand the Yin character of CuOx nanoclusters, we calculated the
22
ACS Paragon Plus Environment

Page 23 of 28
ACS Catalysis
1
2
3
4
5
6
7
8
9
partial electronic density of states (PEDOS) of CuOx/anatase using Cu3O3/anatase
(101) as model by DFT, in which Cu3d, O2p, and Ti3d PEDOS are displayed (Figure
8). New states are present above the valence band edge of the anatase (101) surface
(Figure 8d), which arise from the presence of CuOxꢀderived occupied states that lie at
higher energy than the VB edge of the anatase. The upward shift in the VB edge
results in a narrowing of the band gap compared to unmodified TiO2, which is
consistent with the result of UVꢀvis. Moreover, the rise in the VB edge will lead to the
decrease of the activity of holes. As a result, the oxyꢀdehydrogenation reaction
occurring on anatase is suppressed (Figure 7). This result is in consistency with the
case of NiOx or CuOx nanoclusters supported on TiO2 reported by Nolan and Tada’s
group.26a, 37ꢀ38
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 8. Atomic structure and calculated partial electronic density of states (PEDOS) for anatase
(101), and Cu3O3/anatase (101), respectively.
CONCLUSIONS
23
ACS Paragon Plus Environment

ACS Catalysis
Page 24 of 28
1
2
3
4
5
6
7
8
9
In conclusion, we report a strategy of controlling CuOx clusters’ distribution on
ceria/anatase nanotube and the catalytic consequence in the model lignin CꢀC bond
cleavage reaction. CuOx/ceria/AꢀNTs photocatalyst shows high activity in the C–C
bond cleavage to benzaldehydes under visible light irradiation. Highly dispersed
CuOx clusters on ceria domains enhance the Ce3+ concentration in ceria, and thus
increase the catalytic activity (Yang character); the decoration of CuOx on the exposed
anatase surface suppresses the unwanted oxyꢀdehydrogenation reaction by shifting the
valence band edge of TiO2 to higher energy (Yin character). Thus, the high
photocatalytic performance is achieved under visible light. A hydrogenꢀabstraction by
photogenerated hole is involved in the reaction mechanism. We believe this work is
instructive for designing active photocatalysts for oxidation of C–C bond and
valorization of lignin, as well as can be used in broad organic reactions.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
AUTHOR INFORMATION
*Corresponding author:
Feng Wang
Tel: +86ꢀ411ꢀ84379762; Fax: +86ꢀ411ꢀ84379798;
Eꢀmail: wangfeng@dicp.ac.cn
Notes
The authors declare no competing financial interest.
ACKNOWLEDGEMENTS
This work was supported by the National Natural Science Foundation of China
24
ACS Paragon Plus Environment

Page 25 of 28
ACS Catalysis
1
2
3
4
5
6
7
8
9
(21422308, 21690082, 21690084), and the Strategic Priority Research Program of
Chinese Academy of Sciences (XDB17020300). Computing resources from the
National Supercomputing Center in Shenzhen (China) and National Supercomputing
Center in Tianjin (China) were gratefully acknowledged.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
SUPPORTING INFORMATION AVAILABLE
This material is available free of charge via the Internet at http://pubs.acs.org.
Catalyst characterization, including TEM images and physical absorption, the effect
of the copper amount on photocatalytic C–C bond cleavage and the procedure for
synthesis of model compounds (NMR characterization was also involved).
REFERENCES
(1) (a) Zhang, L.; Bi, X.; Guan, X.; Li, X.; Liu, Q.; Barry, B. D.; Liao, P. Angew. Chem., Int. Ed.
2013, 125, 11513-11517; (b) Souillart, L.; Cramer, N. Chem. Rev. 2015, 115, 9410-9464; (c)
Huang, X.; Li, X.; Zou, M.; Song, S.; Tang, C.; Yuan, Y.; Jiao, N. J. Am. Chem. Soc. 2014, 136,
14858-14865; (d) Wang, M.; Lu, J.; Zhang, X.; Li, L.; Li, H.; Luo, N.; Wang, F. ACS Catal. 2016,
6, 6086-6090.
(2) Bharathi, K.; Ravindra, P. Electron. J. Environ., Agric. Food Chem. 2006, 5, 1253-1264.
(3) Sedai, B.; Díaz-Urrutia, C.; Baker, R. T.; Wu, R.; Silks, L. A. P.; Hanson, S. K. ACS Catal.
2013, 3, 3111-3122.
(4) Luo, F. X.; Zhou, T. G.; Li, X.; Luo, Y. L.; Shi, Z. J. Org. Chem. Front. 2015, 2, 1066-1070.
(5) Wang, M.; Li, L. H.; Lu, J. M.; Li, H. J.; Zhang, X. C.; Liu, H. F.; Luo, N. C.; Wang, F. Green
Chem. 2016, 19, 702-706.
(6) (a) Tomita, O.; Otsubo, T.; Higashi, M.; Ohtani, B.; Abe, R. ACS Catal. 2016, 6, 1134-1144;
(b) Higashi, M.; Domen, K.; Abe, R. J. Am. Chem. Soc. 2013, 135, 10238-10241; (c) Abe, R.;
Shinmei, K.; Koumura, N.; Hara, K.; Ohtani, B. J. Am. Chem. Soc. 2013, 135, 16872-16884; (d)
Barreca, D.; Fornasiero, P.; Gasparotto, A.; Gombac, V.; Maccato, C.; Montini, T.; Tondello, E.
ChemSusChem 2009, 2, 230-233.
(7) (a) Gombac, V.; Sordelli, L.; Montini, T.; Delgado, J. J.; Adamski, A.; Adami, G.; Cargnello,
M.; Bernal, S.; Fornasiero, P. J. Phys. Chem. A 2010, 114, 3916-3925; (b) Okunaka, S.;
Tokudome, H.; Hitomi, Y.; Abe, R. J. Mater. Chem. A 2015, 3, 1688-1695; (c) Yamauchi, M.;
Abe, R.; Tsukuda, T.; Kato, K.; Takata, M. J. Am. Chem. Soc. 2011, 133, 1150-1152; (d) Abe,
R.; Takami, H.; Murakami, N.; Ohtani, B. J. Am. Chem. Soc. 2008, 130, 7780–7781; (e)
Yurdakal, S.; Palmisano, G.; Loddo, V.; Augugliaro, V.; Palmisano, L. J. Am. Chem. Soc. 2008,
25
ACS Paragon Plus Environment

ACS Catalysis
Page 26 of 28
1
2
3
130, 1568-1569.
4
5
6
7
(8) (a) Nguyen, J. D.; Matsuura, B. S.; Stephenson, C. R. J. Am. Chem. Soc. 2014, 136,
1218-1221; (b) Karkas, M. D.; Bosque, I.; Matsuura, B. S.; Stephenson, C. R. Org. Lett. 2016,
18, 5166-5169; (c) Gazi, S.; Hung Ng, W. K.; Ganguly, R.; Putra Moeljadi, A. M.; Hirao, H.; Soo,
H. S. Chem. Sci. 2015, 6, 7130-7142.
8
9
(9) (a) Reddy, G. V. B.; Sridhar, M.; Gold, M. H. Eur. J. Biochem. 2003, 270, 284-292; (b) Wang,
M.; Lu, J.; Ma, J.; Zhang, Z.; Wang, F. Angew. Chem., Int. Ed. 2015, 54, 14061-14065; (c) Cho,
S. H.; Kim, J. Y.; Kwak, J.; Chang, S. Chem. Soc. Rev. 2011, 40, 5068-83.
(10) (a) Zhang, C.; Lu, J.; Zhang, X.; MacArthur, K.; Heggen, M.; Li, H.; Wang, F. Green Chem.
2016, 18, 6545-6555; (b) Kim, S.; Chmely, S. C.; Nimlos, M. R.; Bomble, Y. J.; Foust, T. D.;
Paton, R. S.; Beckham, G. T. J. Phys. Chem. Lett. 2011, 2, 2846-2852.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(11) (a) Lim, S. H.; Lee, W. S.; Kim, Y.-I.; Sohn, Y.; Cho, D. W.; Kim, C.; Kim, E.; Latham, J. A.;
Dunaway-Mariano, D.; Mariano, P. S. Tetrahedron 2015, 71, 4236-4247; (b) Cho, D. W.;
Parthasarathi, R.; Pimentel, A. S.; Maestas, G. D.; Park, H. J.; Yoon, U. C.; Dunaway-Mariano,
D.; Gnanakaran, S.; Langan, P.; Mariano, P. S. J. Org. Chem. 2010, 75, 6549-62.
(12) In Chinese philosophy, Yin means the negative principle (characterized by dark) and Yang
means the positive principle (characterized by light) of the two opposing cosmic forces. Yin
and yang describe how seemingly opposite or contrary forces may actually be complementary,
interconnected, and interdependent in the natural world, and how they may give rise to each
other as they interrelate to one another. In this work, the decorated of CuOx clusters could
suppress the oxy-dehydrogenation reaction, which we termed it Yin character and promoted
the C–C bond cleavage, which we termed it Yang character.
(13) (a) Tsai, C.; Teng, H. Chem. Mater. 2004, 16, 4352-4358; (b) Zhao, H.; Dong, Y.; Jiang, P.;
Wang, G.; Zhang, J. ACS Appl. Mater. Interfaces 2015, 7, 6451-6461.
(14) Wang, Y.; Wang, F.; Song, Q.; Xin, Q.; Xu, S.; Xu, J. J. Am. Chem. Soc. 2013, 135,
1506-1515.
(15) Kresse, G.; Furthmuller, J. Comput. Mater. Sci. 1996, 6, 15-50.
(16) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 1996, 77, 3865.
(17) Kresse, G.; Joubert, D. Phys. Rev. B 1999, 59, 1758-1775.
(18) Monkhorst, H. J.; Pack, J. D. Phys. Rev. B 1976, 13, 5188-5192.
(19) Dudarev, S. L.; Botton, G. A.; Savrasov, S. Y.; Humphreys, C. J.; Sutton, A. P. Phys. Rev.
B 1998, 57, 1505-1509.
(20) Burdett, J. K.; Hughbanks, T.; Miller, G. J.; Richardson, J. W.; Smith, J. V. J. Am. Chem.
Soc. 1987, 109, 3639-3646.
(21) (a) Kresse, G.; Furthmuller, J. Phys. Rev. B 1996, 54, 11169-11186; (b) Kresse, G.;
Furthmuller, J. Comput. Mater. Sci. 1996, 6, 15-50.
(22) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 1996, 77, 3865-3868.
(23) (a) Kresse, G.; Joubert, D. Phys. Rev. B 1999, 59, 1758-1775; (b) Blochl, P. E. Phys. Rev.
B 1994, 50, 17953-17979.
(24) (a) Jiang, D.; Wang, W.; Zhang, L.; Zheng, Y.; Wang, Z. ACS Catal. 2015, 5, 4851-4858;
(b) Khan, M. M.; Ansari, S. A.; Pradhan, D.; Han, D. H.; Lee, J.; Cho, M. H. Ind. Eng. Chem.
Res. 2014, 53, 9754-9763.
(25) (a) Younis, A.; Chu, D.; Kaneti, Y. V.; Li, S. Nanoscale 2016, 8, 378-387; (b) Zhao, K.; Qi,
J.; Yin, H.; Wang, Z.; Zhao, S.; Ma, X.; Wan, J.; Chang, L.; Gao, Y.; Yu, R.; Tang, Z. J. Mater.
26
ACS Paragon Plus Environment

Page 27 of 28
ACS Catalysis
1
2
3
4
5
6
7
8
9
Chem. A 2015, 3, 20465-20470; (c) Andersson, D. A.; Simak, S. I.; Johansson, B.; Abrikosov, I.
A.; Skorodumova, N. V. Phys. Rev. B 2007, 75, 035109; (d) Montini, T.; Melchionna, M.; Monai,
M.; Fornasiero, P. Chem. Rev. 2016, 116, 5987-6041.
(26) (a) Jin, Q.; Fujishima, M.; Iwaszuk, A.; Nolan, M.; Tada, H. J. Phys. Chem. C 2013, 117,
23848-23857; (b) Assadi, M. H. N.; Hanaor, D. A. H. Appl. Surf. Sci. 2016, 387, 682-689.
(27) Tang, C.; Jiao, N. Angew. Chem., Int. Ed. 2014, 53, 6528-6532.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(28) If the reaction was conducted under 365 nm light illumination, the substrate 1a was
dehydrogenated to 1b as major product over A-NTs, as shown in Figure 8.
(29) Zhao, J.; Chen, H.; Tian, X.; Zang, H.; Fu, Y.; Shen, J. J. Catal. 2013, 298, 161-169.
(30) (a) Raza, F.; Park, J. H.; Lee, H.; Kim, H.; Jeon, S.; Kim, J. ACS Catal. 2016, 6,
2754-2759; (b) Lang, X.; Ji, H.; Chen, C.; Ma, W.; Zhao, J. Angew. Chem., Int. Ed. 2011, 50,
3934-3937; (c) Su, F.; Mathew, S. C.; Mohlmann, L.; Antonietti, M.; Wang, X.; Blechert, S.
Angew. Chem., Int. Ed. 2011, 50, 657-660.
(31) (a) Luo, S.; Nguyen-Phan, T.-D.; Johnston-Peck, A. C.; Barrio, L.; Sallis, S.; Arena, D. A.;
Kundu, S.; Xu, W.; Piper, L. F. J.; Stach, E. A.; Polyanskiy, D. E.; Fujita, E.; Rodriguez, J. A.;
Senanayake, S. D. J. Phys. Chem. C 2015, 119, 2669-2679; (b) Wang, Y.; Zhao, J.; Wang, T.;
Li, Y.; Li, X.; Yin, J.; Wang, C. J. Catal. 2016, 337, 293-302; (c) Kundu, S.; Ciston, J.;
Senanayake, S. D.; Arena, D. A.; Fujita, E.; Stacchiola, D.; Barrio, L.; Navarro, R. M.; Fierro, J.
L. G.; Rodriguez, J. A. J. Phys. Chem. C 2012, 116, 14062-14070; (d) Catlow, C. R.; Guo, Z. X.;
Miskufova, M.; Shevlin, S. A.; Smith, A. G.; Sokol, A. A.; Walsh, A.; Wilson, D. J.; Woodley, S.
M. Philos. Trans. R. Soc. A 2010, 368, 3379-456.
(32) Knauth, P.; Saltsburg, H.; Engel, J.; Tuller, H. L. J. Mater. Chem. A 2015, 3, 8369-8379.
(33) (a) Lee, Y.; He, G.; Akey, A. J.; Si, R.; Flytzani-Stephanopoulos, M.; Herman, I. P. J. Am.
Chem. Soc. 2011, 133, 12952-12955; (b) Esch, F.; Fabris, S.; Zhou, L.; Montini, T.; Africh, C.;
Fornasiero, P.; Comelli, G.; Rosei, R. Science 2005, 309, 752-755.
(34) (a) Wu, Z.; Li, M.; Howe, J.; Meyer III, H. M.; Overbury, S. H. Langmuir 2010, 26,
16595-16606; (b) Li, M.; Tumuluri, U.; Wu, Z.; Dai, S. ChemSusChem 2015, 8, 3651-3660; (c)
Wu, Z.; Li, M.; Overbury, S. H. ChemCatChem 2012, 4, 1653-1661; (d) Zhang, L.; Wu, Z.;
Nelson, N. C.; Sadow, A. D.; Slowing, I. I.; Overbury, S. H. ACS Catal. 2015, 5, 6426-6435; (e)
Zhang, Z.; Wang, Y.; Wang, M.; Lu, J.; Li, L.; Zhang, Z.; Li, M.; Jiang, J.; Wang, F. Chin. J.
Catal. 2015, 36, 1623-1630; (f) Zhang, Z.; Wang, Y.; Wang, M.; Lu, J.; Zhang, C.; Li, L.; Jiang,
J.; Wang, F. Catal. Sci. Technol. 2016, 6, 1693-1700.
(35) (a) Deori, K.; Gupta, D.; Saha, B.; Deka, S. ACS Catal. 2014, 4, 3169-3179; (b) Trogadas,
P.; Parrondo, J.; Ramani, V. ACS Appl. Mater. Interfaces 2012, 4, 5098-5102.
(36) Saavedra, J.; Doan, H. A.; Pursell, C. J.; Grabow, L. C.; Chandler, B. D. Science 2014,
345, 1599-1602.
(37) Iwaszuk, A.; Nolan, M.; Jin, Q.; Fujishima, M.; Tada, H. J. Phys. Chem. C 2013, 117,
2709-2718.
(38) (a) Fronzi, M.; Iwaszuk, A.; Lucid, A.; Nolan, M. J. Phys.: Condens. Matter 2016, 28,
074006; (b) Nolan, M.; Iwaszuk, A.; Lucid, A. K.; Carey, J. J.; Fronzi, M. Adv. Mater. 2016, 28,
5425-5446.
27
ACS Paragon Plus Environment

ACS Catalysis
Page 28 of 28
1
2
3
4
TOC
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
28
ACS Paragon Plus Environment