Synthesis and characterization of an A2BC type phthalocyanine and its visible-light-responsive photocatalytic H2 production performance on graphitic carbon nitride

Article abstract of DOI:10.1039/c6dt01248e

A highly asymmetric A₂BC type zinc phthalocyanine (Zn-di-PcNcTh) has been designed and synthesized. The Zn-di-PcNcTh used a π electron rich thiophene ring in place of the benzenoid rings of phthalocyanine which acted as an electron donor, diphenylphenoxy substituents to retard aggregation and a carboxyl-naphthalene unit as an electron acceptor. The asymmetric phthalocyanine shows a strongly split Q-band and wide spectral absorption in the visible/near-IR light region, which can extend the spectral response region of graphitic carbon nitride (g-C₃N₄) from ～450 nm to more than 800 nm. By using it as a sensitizer of 1.0 wt% Pt-loaded graphitic carbon nitride (g-C₃N₄), the experimental results indicate that Zn-di-PcNcTh-Pt/g-C₃N₄ shows a H₂ production efficiency of 249 μmol h^-1 with an impressive turnover number (TON) of 9960.8 h^-1 under visible light (λ ≥ 420 nm) irradiation, much higher than that of pristine Pt/g-C₃N₄. Owing to the introduction of a highly bathochromic shift of 3,4-dicyanothiophene and the valuable "push-pull" effect from the thiophene (electron donor) to the carboxyl-naphthalene (electron acceptor) unit, Zn-di-PcNcTh/g-C₃N₄ gives an extremely high apparent quantum yield (AQY) of 2.44%, 3.05%, and 1.53% under 700, 730, and 800 nm monochromatic light irradiation, respectively, under optimized photocatalytic conditions.

Full text of DOI:10.1039/c6dt01248e

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DOI: 10.1039/C6DT01248E
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essential requirements such as broad light response, appropriate
redox potential for electron-injection and regeneration
following light excitation, stability under long-term light
Lꢃꢑꢂꢀꢔꢁꢍꢑꢓꢀꢃ
During the past decades, increasing attention has been paid to
the photocatalytic procedure for clean hydrogen energy
production over semiconductor, due to the increasingly serious
energy and environment crises.1-4 Besides the commonly used
semiconductors such as TiO2 and CdS, graphitic carbon nitrides
(g-C3N4) as a novel polymer semiconductor have attracted
numerous attentions due to its specific planar structure,
physicochemical property and appropriate energy band
positions for photosplitting water.5-7 The utilization of g-C3N4,
opens up a new prospect to construct highly efficient and
economical photocatalysis systems. However, the bandgap of
g-C3N4 is 2.7 eV with an absorption edge just at ~ 450 nm,
which largely restricts the utilization efficiency of visible-
light.8-10 To extend its visible light absorption and improve its
photocatalytic activity, several strategies, such as doping with
metal or nonmetallic elements,11 copolymerization of two or
more precursors,12 surface modification13,14 and dye
sensitization15,16 have been developed. Among various
strategies for visible-light harvesting, dye sensitization is one of
the efficient approaches to expand the spectral response region
of semiconductors.
irradiation and inexpensive. Typically, organic dyes (such as
Eosin Y,17 Rhodamine B18 and coumarin dyes19,20) and metal
complexes (such as Ru-complexs3,21 and metal porphyrin22) are
the most commonly used sensitizers in dye-sensitized
semiconductors for H2 production. However, ruthenium is a
rare metal, and the embarrassing thing is that most common
used dyes hardly extend the spectral response to longer than
600 nm. Phthalocyanines (Pcs) are planar 18 π-electron
conjugated system, which generates intense absorption in the
UV/blue (Soret B band) and the red/near-IR (Q-band) spectral
regions. In addition, the excellent photochemical/thermal
stabilities and appropriate redox properties of Pcs also render
them attractive dye for the sensitization of wide-band-gap
semiconductors such as TiO2.23,24 Dye sensitization of g-C3N4
is also an efficient way to use the visible light of solar radiation.
Until now, poly(3-hexylthiophene) (P3HT), Erythrosin B (ErB)
and Eosin Y (EY) are used as sensitizers for g-C3N4 to enhance
the photocatalytic H2 production activity with considerable
visible-light utilization efficiency and maximal responsive
wavelength at ~ 600 nm.17,25,26 However, there was rare study
of the utilization of huge visible/near-IR light with wavelength
longer than 600 nm, Pc-sensitized g-C3N4 showed
photocatalytic H2 production activity. Domen et al. exploited
MgPc-sensitized g-C3N4 for H2 evolution, which showed
photocatalytic H2 production activity at 600-800 nm but with
rather low apparent quantum yield (AQY) of 0.07% at ~ 660
nm.15 Lu et al. reported that a MnPc covalently functionalized
As the light harvesting center, the dye must possess certain
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DOI: 10.1039/C6DT01248E
!wÇL/[9
Wꢀꢁꢂꢃꢄꢅ bꢄꢆꢇ
graphene nanohybrid (MnPc-G) photocatalyst showed diphenylphenoxy to retard the aggregation. Owing to the low
photocatalytic hydrogen evolution at 600-800 nm and apparent reactivity and highly bathochromic shift of 3,4-dicyanothiophe-
quantum efficiency (0.06%) at 670 nm.27 Therefore, the ne, π electron rich thiophene ring has been in place of the
development of an efficient near-IR responsive catalyst still benzenoid ring of phthalocyanine which was acting as an
have a broad prospect.
electron donor. By using this highly asymmetric A2BC type
Recently, highly conjugated mononaphthalo-triphthalocya- phthalocyanine derivative as a sensitizer of g-C3N4, Zn-di
-
nine derivatives (Zn-tri-PcNc) have been designed and PcNcTh/g-C3N4 without CDCA coadsorbent exhibits a H2
synthesized by our group, which showed a Q-band redshift to production efficiency of 249 µmol h-1 with an impressive
the near-IR region stemmed from the expanded π-conjugated turnover number (TON) of 9960.8 under visible light (λ ≥ 420
macrocycle by introducing an additional benzo group to the nm) irradiation. Owing to the introduction of highly
benzopyrrole groups of the ZnPc framework. Zn-tri-PcNc was bathochromic shift of 3,4-dicyanothiophene, Zn-di-PcNcTh/g-
used to sensitize TiO2 for H2 production, which showed a C3N4 gives an extremely high apparent quantum yield (AQY)
considerable photoactivity and 0.2% AQY at 700 nm mono- of 2.44%, 3.05%, 1.53% at 700, 730, 800 nm monochromatic
chromatic light.24 When Zn-tri-PcNc was utilized as a sensitizer light irradiation. The above results show the promising
to extend the spectral response region of g-C3N4 from 450 nm application of thiophene phthalocyanines in photocatalytic H2
to more than 800 nm. After optimizing the photocatalytic production system for more efficiently untilizing the solar
condition and adding chenodeoxycholic acid (CDCA) as radiation with wavelength from 600 nm to 800 nm.
coadsorbent, Zn-tri-PcNc sensitized g-C3N4 photocatalyst
showed a H2 production efficiency of 125.2 µmol h-1 under
9* ꢇꢂꢓꢆꢇꢃꢑꢄꢅ
visible-light irradiation and 1.85% apparent quantum yield
(AQY) at 700 nm monochromatic light irradiation, improved
by 50.5% compared with the photoreaction system without
Dye synthesis
All chemicals were used as received unless otherwise stated.
Butanol was freshly distilled from sodium, N,N-
dimethylformamide (DMF) and dichloromethane (DCM) were
distilled from CaH2 under N2. Thin layer chromatography (TLC)
was performed on glass plates (20 cm
silica gel, and column chromatography was carried out on silica
gel columns (Merk, Kieselgel60, 70-230mesh) with the
CDCA.4 It indicated that the steric hindrance of the three tert
-
butyl groups in Zn-tri-PcNc is too small to effectively retard
phthalocyanine π-π stacking, while the aggregation tendency of
ZnPc is considered to enhance the self-quenching of the dye
excited singlet state, thus resulting in decreased efficiency. To
enhance the steric hindrance, Zn-tri-PcNc-8 has been
synthesized with six diphenylphenoxy to suppress the
molecular aggregation. Zn-tri-PcNc-8 sensitized TiO2-based
solar cell exhibited a maximum incident photo-to-current
conversion efficiency (3.01%) in the red/near-IR light range
(650-750 nm) without CDCA, which was much higher than that
(1.96%) for a solar cell sensitized by Zn-tri-PcNc.28-30
In 2000, Cook et al. synthesized tribenzo[b,g,l]thiopheno-
[3,4-q]porphyrazine and tribenzo[b,g,l] thiopheno[2,3-q]porph-
yrazine ring systems by cross cyclotetramerisation reactions of
3,6-dialkylphthalonitriles with 3,4-dicyanothiophene and 2,3-
dicyanothiophene respectively, and tribenzo[b,g,l]thiopheno-
[3,4-q]porphyrazine shows a strongly split Q-band absorption
in the far red region of the spectrum and highly bathochromic
shift relative to the corresponding band in symmetric
phthalocyanine. On the other hand, their studies have indicated
that 3,4-dicyanothiophene compared to phthalonitriles and 2,3-
dicyanothiophene has lower reactivity in cross cyclotetrameris-
ation reactions.31 Subsequently Kimura and coworkers have
synthesized bis(4-methylpyridine)-[1,3,5,7,9,11,13,15-octaphe-
nyltetra(3,4-thieno)tetraazaporphy-rinato]ruthenium(II),32 and
Dubinina et al.33 have investigated the characterization of
binuclear thienoporphyrazines. Although the thiophene
derivatives have been widely used in organic field-effect
transistor (OFET) and organic photovoltaic (OPV) devices, the
thiophene porphyrazines have not been noticed and applied in
photocatalysis.
ꢀ 20 cm) with GF-254
1
appointed eluents. H NMR (300 MHz) spectra were recorded
on
a Bruker DPX 300 spectrometer using solutions in
deuterated solvents and tetramethylsilane (TMS) is the internal
standard in NMR measurements. UV-vis spectra were obtained
on a Hitachi U-4100 spectrophotometer. Fluorescence spectra
were recorded with K2 ISIS spectrometer. IR spectra were
recorded on a BIORAD FTS-165 spectrometer using KBr
pellets. Matrix-assisted laser desorption/ionization time-of-
flight mass spectrometry (MALDI-TOF-MS) was carried on a
Bruker BIFLEX III ultrahigh resolution Fourier transform ion
cyclotron resonance (FTICR) mass spectrometer using a-cyano-
4-hydroxycinnamic acid as matrix. Elemental analyses were
performed on a Vavio El III Elementar. The synthetic routes of
4,5-bis(2',6'-diphenylphenoxy)-phthalonitrile (ligand A), 3,4-
dicyanothiophene (ligand B) and 6-Carboxymethyl-2,3-
dicyanonaphthalene (ligand C) were shown in Supporting
Information. 6-Carboxymethyl-2,3-dicyanonaphthalene were
Herein we have synthesized a highly asymmetric and A2BC
type phthalocyanine derivatives (Zn-di-PhNcTh) using
carboxyl-naphthalene unit as electron acceptor and
a
a
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DOI: 10.1039/C6DT01248E
Wꢀꢁꢂꢃꢄꢅ bꢄꢆꢇ
!wÇL/[9
prepared according to the previous methods.28-30 The route to 4,5- Materials Preparation
bis(2',6'-diphenylphenoxy)-phthalonitrile has been described in
Graphitic carbon nitride (g-C3N4) was synthesized by a simple
thermolysis process of urea according to our previous report.38
Typically, 5 g urea was placed in a closed crucible and
calcinated at 580 °
C for 3 h with a heating rate of 5 °C mim-1,
earlier papers.34,35 3,4-Dicyanothiophene was prepared from
commercially available 3,4-dibromothiophene by the Rosenmund
von Braun reaction with copper(I) cyanide.36, 37
and then the yellow-colored product was washed by nitric acid
(0.1 M) and distilled water, and then dried at 70 °C overnight to
obtain the product (g-C3N4). Co-catalyst Pt nanoparticles were
loaded on g-C3N4 by a photodeposition procedure. Typically,
0.2 g of g-C3N4 was suspended into 40 mL of water, 10 mL of
methanol and 0.134 mL of H2PtCl6 (0.077 M) mixed solution,
and then the suspension was irradiated using a 500 W high
pressure Hg lamp for 3 h under stirring after dispersion in an
ultrasonic bath for 10 min. The product was separated by
centrifugation, washed with water, and then dried at 70 °C
overnight to obtain 1.0 wt % Pt/g-C3N4.
Synthesis of 8,9,24,25-tetra(2',6'-diphenylphenoxy)-16(or 17)-
carboxyl zinc dibenzo naphthothiophenoporphyrazine (Zn-di-
PhNcTh). A solution of 3,4-dicyanothiophene (136.1 mg, 1.02
mmol ), 4,5-bis(2',6'-diphenylphenoxy)phthalonitrile (209.5
mg, 0.34 mmol ) and 6-carboxymethyl-2,3-dicyanonaphthalene
(120.4 mg, 0.51 mmol) in dry n-butanol (10 mL) was heated to
100 °C with stirring for 3 h. To the reactant mixture was added
slowly lithium metal (0.2 g) under stirring (Scheme 1). The
solution immediately turned an intense green color and was
heated to reflux for 6 h. When the mixture was allowed to cool
to room temperature, glacial acetic acid (10 mL) was added and
Dye-sensitized g-C3N4 was prepared by an impregnation
stirring was continued at 70 °C for 30 min. The mixture was
method. 0.1 g of Pt/g-C3N4 was dissolved with 3 mL of Zn-di
-
cooled to room temperature and methanol (100 mL) was added.
Then the mixture was filtered and the precipitation was washed
with methanol. The residue was separated by silica gel column
chromatography with DCM as a solvent and monitored by UV-
vis spectra. The component and properties of by-products were
shown in Supporting Information.
PcNcTh CHCl3 solution (0.17 mM) under stirring for 12 h at
60 °C and then the product was filtered through a 0.45 µm
nylon filter and dried at room temperature overnight. There was
no signal of Zn-di-PcNcTh existence in the filtrate of the
suspension after sensitization procedure, therefore the Zn-di
-
PcNcTh adsorbed amount on the calculated to be 5 µmol g-1.
The target product, 8,9,24,25-tetra(2',6'-diphenylphenoxy)-
16(or 17)-carboxyl-30H,32H-dibenzonaphthothiophenoporp-
hyrazine (H2-di(opp)-PcNcTh) was separated by using DCM-
MeOH (95:5) as eluent and recrystallized from DCM-MeOH to
obtain a green solid. Yield: 10 mg, 3%. UV-vis λmax (DCM)/nm
Electrochemical Measurement and Computational Details
Electrochemical measurements such as cyclic voltammetry (CV)
were measured with a BAS CV-50W voltammetric analyzer,
using a three-electrode cell with a glassy carbon disk working
electrode, a silver-wire counter electrode, and a Ag/Ag+ (0.01
M AgNO3 in acetonitrile) reference electrode. The results were
corrected for junction potentials using saturated calomel
electrode (SCE) as typical units which have been referenced
internally to the ferrocenium/ferrocene (Fc+/Fc) couple
[E1/2(Fc+/Fc) = 0.50 V vs. SCE]. Typically, a 0.1 M solution of
[Bu4N][ClO4] in DCM containing 0.5 mM ZnPc dye was
purged with N2 for 10 min, and the voltammogram was
recorded at ambient temperature with a scan rate of 20 mV s-1.
The primal input structures of Zn-di-PhNcTh were obtained
by adding a benzene ring onto one of the benzene rings of
phthalocyanine and then attaching six 2,6-diphenylphenoxy
groups and one carboxyl group onto the peripheral positions.
Moreover, a benzene ring of phthalocyanine was replaced by a
π electron rich thiophene ring. The ground state geometries
were optimized by using the B3LYP (BeckeLee-Young-Parr
composite of exchange-correlation functional) method with the
6-31G(d) basis set, which has been proved to be suitable for
calculating the molecular orbitals (MOs) of ZnPc derivatives.
According to our previous reported method,28-30 the hybrid
density functional Becke-Lee-Young-Parr composite of
exchange-correlation functional method was used for both
geometry optimizations and property calculations. The Berny
algorithm using redundant internal coordinates was employed
in energy minimization and default cutoffs were used
throughout. Electronic absorption spectroscopic calculations of
H2-di(adj)-PcNcTh and H2-di(opp)-PcNcTh were made by TD-
1
(logε): 746 (4.74); 723 (4.90); 427 (4.32); 343 (4.71). H NMR
(CDCl3, 300MHz): δ=8.14 (s, 2H
ÈThH), 7.89-7.74 (br, 48H,
ArH), 6.98-6.89 ppm(br, 36H, ArH). FT-IR (KBr): ν (cm-1) =
3292 (w, COOH), 3057 (w, ArCH), 3029 (w, ArCH), 1719 (w,
C=O), 1617 (w, C=N), 1600, 1498, 1474, 1454, 1413, 1270,
1196, 1091, 1030, 880, 791, 751, 699 (Fig. S15†). TOF-MS
(m/z): calcd for C107H66N8O6S [M+1]+ 1591.78; found 1591.27
(Fig.
S21†);
Elemental
analysis
calcd
for
C107H66N8O6S·CH3OH·CH2Cl2: C 76.62, H 4.25, N 6.56;
Found: C 76.07, H 4.69, N 6.22.
In a typical procedure, zinc acetate (68.0 mg, 0.314 mmol)
was added to a stirred solution of H2-di(opp)-PcNcTh (50 mg,
0.031 mmol) in DMF (20 mL) and heated to 100 °C for 8 h.
The solvent was removed under reduced pressure and the
residue was purified using column chromatography over silica
gel and then recrystallized from DCM-MeOH to afford
8,9,24,25-tetra(2',6'-diphenylphenoxy)-16(or 17)-carboxyl-zinc-
dibenzo-naphthothiophenoporphyrazine (Zn-di-PhNcTh) Yield:
48 mg, 92%. UV-vis λmax (DCM)/nm (logε): 732 (5.13); 697
(4.96); 357 (4.81) (Fig. S1†). 1H NMR (CDCl3, 300MHz):
δ=8.15 (s, 2H, ThH), 7.90-7.81 (br, 48H, ArH), 7.01-6.88
ppm(br, 36H, ArH) (Fig. S22†). FT-IR (KBr): ν (cm-1) = 3292
(w, COOH), 3057 (w, ArCH), 3028 (w, ArCH), 1728 (w,
C=O), 1612, 1500, 1454, 1413, 1268, 1197, 1092, 1028, 880,
750, 700 (Fig. S7†). TOF-MS (m/z) calcd for ZnC107H64N8O6S
[M+1]+ 1653.40, found 1653.34 (Fig. S6†); Elemental analysis
calcd for ZnC107H64N8O6S·CH3OH: C 79.98, H 4.23, N 6.91;
Found: C 79.45, H 4.45, N 6.68.
Ç ꢀꢁ ꢂꢃꢄꢅꢆꢇꢈ ꢀꢁ ꢉ Ç ꢊ wꢃꢋꢇꢈ {ꢃꢌꢀꢊꢍꢋ ꢃꢎ / ꢊꢏꢀꢁꢍꢅꢋ ꢐꢑꢒꢒ
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tꢈꢊꢇꢁꢊ %ꢃ ꢆꢃꢍ ꢇ%ꢂꢄꢁꢍ ꢏꢇꢅ&ꢀꢆꢁ
Dalton Transactions
Page 4 of 8
View Article Online
DOI: 10.1039/C6DT01248E
!wÇL/[9
Wꢀꢁꢂꢃꢄꢅ bꢄꢆꢇ
DFT method on the basis of the optimized structures due to the 1). Owing to the lower reactivity of 3,4-dicyanothiophene compared
large complex computation of Zinc phthalocyanine.39 All to phthalonitriles, multitudinous 3,4-dicyanothiophene was added to
calculations were carried out using the Gaussian 03 program in limit the varieties of by-products.31 A standard work-up included
the IBM P690 system in High Performance Computing treatment with acetic acid to convert the initially formed lithium Pc
Center.40
derivatives into their corresponding metal-free products. The
carboxymethyl ester was simultaneously hydrolyzed to carboxylic
acid by lithium alkoxide base. It is noteworthy that purification of
Materials Characterization
general phthalocyanine compounds has been
a challenge for
UV-vis diffuse reflectance spectra (DRS) were obtained with a
Shimadzu UV-3600 UV-vis-NIR spectrophotometer equipped
with an integrating sphere. Photoluminescence (PL) spectra
were determined by Hitachi F-4500 fluorescence spectrophoto-
meter. Transient photocurrent was investigated on CHI 618C
electrochemical analyzer with three-electrode system, where Pt
wire, Pt plate and Ag/AgCl as work, counter and reference
electrode, respectively. And the electrodes are immersed into a
suspension containing 10 mg g-C3N4, Zn-di-PcNcTh-Pt/g-C3N4,
1.0 M NaOH and 5 mg methyl viologen (MV) as electron
media, which was continuously purged by N2 to remove O2
before light irradiation.
chemists, not to mention the separation of a series of closely related
and isomeric phthalocyanines. Fortunately, the mixture could be
separated into different fractions through silica gel column
chromatography. There are tremendous discrepancy of the solubility
and polarity of these phthalocyanine derivatives due to the difference
of their molecule structure and symmetry. All of the five fractions
1
give satisfactory C, H and N data, H NMR spectra, MALDI-TOF-
MS and IR spectra and the results are shown in the ESI†.
The highly asymmetric Zn-di-PcNcTh dye was characterized by
elemental analysis, 1H NMR, MALDI-TOF-MS, IR, UV-vis and
fluorescence spectroscopy. The UV-vis absorption spectra (Fig. 1†)
show that Zn-di-PcNcTh in DCM solution exhibits a strongly split Q
absorption with a maximum absorption at 732 nm (ε = 1.35 × 105 M-
Photocatalytic Property Tests
1
cm-1) and submaximal absorption at 697 nm (ε = 9.08 × 104 M-1
The H2 production reaction was carried out in an outer irradiation-
type photoreactor (Pyrex glass) connected to a closed gas-circulation
system. A 300 W Xe-lamp (PLS-SXE300, Beijing Trusttech Co.
Ltd., China) with an emission spectrum covering the whole UV-
vis/IR region from 200 to > 1100 nm was used as the light source,
and a cutoff filter (λ ≥ 420 nm) was employed to obtain the visible-
light irradiation. The H2 evolution rate was analyzed with a gas
chromatograph (GC, SP6890, TCD detector, 5 Å molecular sieve
columns and Ar carrier). The photoreaction system contains 10 mg
of Zn-di-PcNcTh /g-C3N4 as a photocatalyst, 10 mL of water, and 88
mg of ascorbic acid (AA, 50 mM) as an electron donor. The turnover
number (TON) is usually defined by the number of reacted
molecules and the number of active sites. In the present work, we
assumed that H2 production takes place when two electrons injected
from the excited dye molecules react with two protons. One dye
molecule can produce only one photogenerated electron which can
be injected into the conduction band (CB) of g-C3N4, therefore two
dye molecules are needed to react with two H+ and produce one H2
molecule. Apparent quantum yield (AQY) was measured under the
same photoreaction condition but with monochromatic light
irradiation obtained from band pass filter (for example, λ = 700 ± 10
nm). The turnover number (TON) and apparent quantum yield
(AQY) were calculated according to the following equations: 4,41
cm-1), which was commonly in free metal phthalocyanines and
asymmetric metal phthalocyanines.31 Actually the reason of the
splitting is the division of the LUMO due to the highly
unsymmetrical of the molecular which can be proved in the
computational section. The above data indicated Zn-di-PcNcTh
which utilized a π electron rich thiophene ring in place of the
benzenoid rings of phthalocyanine possesses a wilder and stronger
optical absorption property and obvious red-shift of Q band than
other phthalocyanine derivatives, which is favorable and significant
for the visible/near-IR-light induced photocatalytic H2 production.
The fluorescence spectrum (Fig. S2*) of the asymmetric Zn-di-
PcNcTh dye shows a maximum emission at 739 nm, and its optical
energy gap (E0–0) can be estimated to be 1.69 eV on the basis of the
intersection point of the UV-vis absorption and fluorescence
emission spectra as show in Fig. S2 in the ESI†.21,41,42
2× number of evolved H2 molecules
Number of dye molecules adsorbed
(1)
(2)
TON=
2× number of evolved H2 molecules
AQY(%)=
×100%
Number of incident photons
wꢇꢌꢁꢅꢑꢌ ꢄꢃꢔ ꢔꢓꢌꢍꢁꢌꢌꢓꢀꢃ
Dye syntheses and spectroscopic analyses
The target metal free phthalocyanine was prepared via cross
cyclotetramerisation by using 6:2:3 of 3,4-dicyanothiophene, 4,5-
bis(2',6'-diphenylphenoxy)-phthalonitrile and 6-carboxymethyl-2,3-
dicyanonaphthalene with lithium n-butyloxide in n-butanol (Scheme
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tꢈꢊꢇꢁꢊ %ꢃ ꢆꢃꢍ ꢇ%ꢂꢄꢁꢍ ꢏꢇꢅ&ꢀꢆꢁ

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Dalton Transactions
Page 5 of 8
View Article Online
DOI: 10.1039/C6DT01248E
Wꢀꢁꢂꢃꢄꢅ bꢄꢆꢇ
!wÇL/[9
E1/2 (
Fc+/Fc vs SCE).43,44 As can be seen, the highest occupied
molecular orbital (HOMO, Eox) of dye can be obtained by curves and
the lowest unoccupied molecular orbital (LUMO) can be calculated
The IR spectrum (Fig. S7†) of Zn-di-PcNcTh shows obvious
featured IR absorption bands of the central aromatic Pc macrocycle,
such as the bands at 750-1750 cm-1 ascribable to the characteristic
absorptions of Pc cores, the bands at 3057-3028 cm-1 ascribable to
the aromatic C-H stretching vibrations, the bands at 1612 and 1500
cm-1 ascribable to the aromatic C=C stretching vibrations, the band
at ~ 1000 cm-1 due to the aromatic in-plane C-H vibrations, and the
bands at 1439-1454 cm-1 and 1312-1323 cm-1 ascribable to the
stretching vibrations of isoindole and pyrrole rings, respectively.
Moreover, the intense absorptions at 1728 cm-1 can be attributed to
the stretching vibrations of -COOH in the asymmetric Zn-di-
PcNcTh. As can be seen from the FTIR spectra in Fig. S8 in the
ESI†, the pristine g-C3N4 exhibits characteristic IR absorption peaks
similar to that in the previous literature.4,41 The four strong peaks at
1238, 1317, 1407, and 1573 cm-1 can be ascribed to the CN
heterocycle stretching of g-C3N4, while the absorption band 1640
cm-1 can be ascribed to the C-N stretching vibration, and a shoulder
broad band near 3166 cm-1 corresponds to the stretching mode of
terminal –NH groups at the defect sites of the aromatic ring.4 The
FTIR spectra of the Zn-di-PcNcTh/g-C3N4 (either with 2.5 or even
10 µmol g-1 dye-adsorbed amount) are similar to the IR absorption
peak positions as that of the pristine g-C3N4, due to the weak IR
absorption peak positions of Zn-di-PcNcTh are covered in the FTIR
spectra of the pristine g-C3N4. UV-vis diffuse reflectance absorption
spectra of g-C3N4, Zn-di-PcNcTh/g-C3N4 are also listed in Fig. 1.
After adsorbing on Pt/g-C3N4, intense red/near-IR adsorption band
similar to the corresponding dye solution can also be observed.
Moreover, Zn-di-Pc-NcTh/g-C3N4 show much broader red/near-IR
light absorption from 550 to 850 nm than the pristine g-C3N4, which
just absorbs light with wavelength shorter than 450 nm due to the
rather large bandgap (~ 2.70 eV).8 Simultaneously, the maximal
absorption wavelengths of Zn-di-PcNcTh/g-C3N4 exhibit about ~ 11
nm red-shift as compared to Zn-di-PcNcTh solution, which may be
caused by the efficient interaction between Zn-di-PcNcTh and g-
C3N4. The other characterization results such as elemental analyses,
1H NMR and MS spectra were also obtained for Zn-di-PcNcTh as
shown in the ESI.†
by E* = Eox
̶ E0-0, where E0-0 (= 1240/λintersection ) is obtained by the
intersection point of the normalized absorption and emission spectra
as shown in Fig. S2,† and therefore E* (ELUMO) of Zn-di-PcNcTh
can be estimated to be -1.39 eV (vs. SCE) as shown in Table 1. The
LUMO levels is sufficiently negative than the CB level (-1.12 eV)7,45
of g-C3N4, indicating that the photogenerated electrons of the excited
dye can availably inject into the conduction band (CB) of g-C3N4 on
aspect of thermodynamics
Density functional theory calculations
The UV-vis absorption spectra of H2-di(adj)-PcNcTh and H2-
di(opp)-PcNcTh were calculated using the TD-DFT method based
on the optimized structures. The calculated electronic absorption
spectra of self-assembled donor-acceptor dyads H2-di(adj)-PcNcTh
and H2-di(opp)-PcNcTh are shown in Fig. S3.† The H2-di(opp)-
PcNcTh have two split Q absorption bands which are 696 nm and
652 nm and H2-di(adj)-PcNcTh have more split Q absorption bands
at 721, 615, 611 and 607 nm. The calculated energy splitting
between the Q bands for H2-di(adj)-PcNcTh is significantly larger
than that for H2-di(opp)-PcNcTh, which is corresponding with UV-
vis absorption spectra feature in Fig. S4.† As can be seen, the
maxium absorption peak of the Q band of H2-di(adj)-PcNcTh is at
757 nm and 722 nm for H2-di(opp)-PcNcTh. It is evident that the Q
absorption bands of H2-di(adj)-PcNcTh are red-shifted compared
with H2-di(opp)-PcNcTh, which corresponds well with its smaller
HOMO-LUMO gap (Fig. S5†). On the other hand, the Q band of H2-
di(adj)-PcNcTh spilts at 757 nm and 671 nm and the spilt of the Q
band of H2-di(opp)-PcNcTh is not obvious, which is in accordance
with their calculated electronic absorption spectra. The UV-vis
absorption spectra of substituted H2-di(adj)-PcNcTh and H2-di(opp)-
PcNcTh complexes have many differences, indicating that the two
4,5-bis(2',6'-diphenylphenoxy)phthalonitrile are adjacent and
opposite which affect the molecular orbitals of the ring to different
extents. So we can distinguish H2-di(adj)-PcNcTh and H2-di(opp)-
PcNcTh through their different UV-vis absorption spectra. In
addition, the major product is H2-di(opp)-PcNcTh, owing to the big
steric hindrance of 4,5-bis(2',6'-diphenylphenoxy)phthalonitrile, H2-
di(opp)-PcNcTh is more stable than H2-di(adj)-PcNcTh.
Dye electrochemical analyses
The electrochemical behavior of Zn-di-PcNcTh was investigated by
cyclic voltammetry (CV) in DCM solution (Fig. S9†).The first half-
wave redox potential values (vs. SCE) are summarized in Table 1.
Eox (vs SCE) = Eox (vs Ag/AgNO3) – E1/2 (
Fc+/Fc vs Ag/AgNO3) +
Density functional theory (DFT) calculations were performed on
Zn-di-PcNcTh at the B3LYP/6-31G(d) level, which has been proved
to be suitable for calculating the MOs of ZnPc derivatives. As shown
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Dye
Zn-di-PcNcTh
λmax / nm
732
ε /×104 M-1 cm-1
13.5
Eox / V vs. SCE
0.30(Oxd1)
Ered / V vs. SCE
-0.98(Red1)
E0-0 /eV
1.69
E*a/ eV
-1.39
aCalculated with the formula E*=Eox - E0-0
.
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Dalton Transactions
Page 6 of 8
View Article Online
DOI: 10.1039/C6DT01248E
!wÇL/[9
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in Fig. 2, the electron density of Zn-di-PcNcTh for HOMO-1 and
HOMO-2 are shared by the 2,6-diphenylphenoxy donor moiety. The
HOMO of Zn-di-PcNcTh is delocalized over the entire molecule.
The LUMO+1 and LUMO are π* orbitals delocalized across the Pc
ring moving to the carboxyl group, while the LUMO+2 is mainly
localized over the naphthalene ring and the carboxyl group. This
indicates that the photoexcited electrons can effectively transfer from
the Pc skeleton to the carboxyl group, which is beneficial for the
injection of the photoexcited electrons to the g-C3N4 CB during
photocatalytic H2 producton operation.
(3)


















t
t
t
Fit = A+ B exp
-
+ B exp
-
+ B exp
-
1
2
3
τ1
τ2
τ3
where A, B1, B2 and B3 are constants and obtained after fitted every
decay curves. As can be seen from Table 2, the fluorescence lifetime
(τ) of Zn-di-PcNcTh is delayed from 2.29 ns to 2.44 ns, the lifetime
enhancement is 70% when Pt/g-C3N4 is added, indicating that the
photogenerated carrier recombination of Zn-di-PcNcTh is strongly
restrained due to the efficient electron transfer from the excited Zn-
di-PcNcTh to g-C3N4.
Fluorescence spectra analyses
The photoluminescence (PL) spectrum is an effective method to
investigate the electron transfer behavior between dye and
semiconductor.16,46,47 As the results in Fig. S10† show, Zn-di-
PcNcTh solution exhibits intense emission bands centered at around
739 nm with excitation wavelength of 666 nm. It indicates that the
strong recombination process of the photogenerated electron-hole
pair of the excited dye. However, obvious quenching effect can be
observed when g-C3N4 is added into the dye solutions, implying the
rapid electron transfer from the excited dye molecules to CB of g-
C3N4 since there is no overlap between the absorption spectra of g-
Photocatalytic activity analyses of Zn-di-PcNcTh/g-C3N4
Photocatalytic H2 production reaction of a dye-sensitized Pt/g- C3N4
photocatalytic system is usually affected by series of conditions such
as electron donors, co-catalyst Pt, irradiation wavelength and time,
dye-adsorbed amount and so on.23 The prsent system adopts the
photoreaction condition similar to our previous report by considering
the similarity in the photocatalytic system.4,38, 41,45
C3N4 and emission spectra of Zn-di-PcNcTh.47
Time-resolved fluorescence spectra (TRPS) is an efficient
method to investigate the recombination rate of the photogenerated
electron-hole pairs, and the corresponding fluorescence lifetime (t)
represents the average existence time of excited dye molecules. The
effects of Pt/g-C3N4 on the fluorescence lifetime of the excited Zn-
di-PcNcTh are shown in Fig. 3 and Table 2. The fluorescence
lifetimes of the systems are obtained by fitting the time-resolved
fluorescence decay curves with the following exponential fitting
equation.
Çꢄ"ꢅꢇ ꢗꢓ Çꢀꢏꢊ"ꢅꢊꢁꢃꢈ'ꢊ% ꢎꢈꢄꢃꢅꢊꢁꢌꢊꢆꢌꢊ %ꢊꢌꢇꢋ %ꢇꢍꢇ ꢃꢎ ùꢆ" ꢅ"tꢌbꢌÇ ꢇꢆ%
ùꢆ" ꢅ"tꢌbꢌÇ .&"/!b< ꢎꢀꢈꢏꢁ %ꢊꢅꢀ'ꢊ% ꢎꢅꢃꢏ Cꢀ&ꢓ !
System
Zn-di-PcNcTh
Zn-di-PcNcTh/g-C3N4
τ1 / ns
2.29
2.44
χ2
0.977
0.983
λdetet /nm
740
740
Cꢓꢎꢋ . [ꢃꢆ&"ꢍꢊꢅꢏ ꢁꢍꢇ8ꢀꢈꢀꢍꢋ ꢎꢃꢅ Iꢐ )ꢅꢃ%ꢄꢌꢍꢀꢃꢆ ꢃꢎ ùꢆ" ꢅ"tꢌbꢌÇ .&"/!b< :ꢀꢍ ꢃꢄꢍ
ꢇ%%ꢀꢆ& ꢌꢃꢇ%ꢁꢃꢅ8ꢊꢆꢍ /5/! ꢄꢆ%ꢊꢅ C D <ꢐꢑ ꢆꢏ ꢈꢀ& ꢍ ꢀꢅꢅꢇ%ꢀꢇꢍꢀꢃꢆꢓ
/ # Wꢀ bꢁꢂꢃꢓꢔ ꢐꢑ ꢐꢔ ꢈꢈꢔ "!
Ç ꢀꢁ ꢂꢃꢄꢅꢆꢇꢈ ꢀꢁ ꢉ Ç ꢊ wꢃꢋꢇꢈ {ꢃꢌꢀꢊꢍꢋ ꢃꢎ / ꢊꢏꢀꢁꢍꢅꢋ ꢐꢑꢒꢒ
tꢈꢊꢇꢁꢊ %ꢃ ꢆꢃꢍ ꢇ%ꢂꢄꢁꢍ ꢏꢇꢅ&ꢀꢆꢁ

tꢈꢊꢇꢁꢊ %ꢃ ꢆꢃꢍ ꢇ%ꢂꢄꢁꢍ ꢏꢇꢅ&ꢀꢆꢁ
Dalton Transactions
Page 7 of 8
View Article Online
DOI: 10.1039/C6DT01248E
Wꢀꢁꢂꢃꢄꢅ bꢄꢆꢇ
!wÇL/[9
concluded that the present Zn-di-PcNcTh/g-C3N4 leads to efficient
utilization of near-IR light. Zn-di-PcNcTh after 10 h of light
irradiation shows an absorption property and peak position very
similar to that without irradiation, and there is no absorption signal
of Zn-di-PcNcTh in the filtrate of Zn-di-PcNcTh/g-C3N4 suspension
after 10 h of light irradiation, as shown in Fig. S12a.† The above
results indicate that the Zn-di-PcNcTh molecule stay the same after
prolonged use and no Zn-di-PcNcTh molecule desorbed from g-
C3N4. Those desorbed Zn-di-PcNcTh with/without 10
h of
irradiation, which are obtained by a desorption procedure (namely,
catalyst was dispersed in 0.2 M KOH in ethanol/THF/water (2:2:1)
solution several times, and the liquid supernatant and precipitate
were collected), also show DRS spectra very similar to the original
one, as can be seen from Fig. S12b.†
The photocatalytic H2 production amount over photocatalyst is
also measured under various monochromatic light irradiation with λ
Cꢓꢎꢋ / /ꢃꢏ)ꢇꢅꢀꢁꢃꢆ ꢃꢎ 5w{ ꢁ)ꢊꢌꢍꢅꢇ ꢇꢆ% !vò 'ꢇꢈꢄꢊꢁ ꢃꢎ ùꢆ" ꢅ"tꢌbꢌÇ .&"/!b< ꢄꢆ%ꢊꢅ
=
420, 450, 550, 600, 685, 700, 735 and 800 nm, using
ꢃ)ꢍꢀꢏꢇꢈ ) ꢃꢍꢃꢅꢊꢇꢌꢍꢀꢃꢆ ꢌꢃꢆ%ꢀꢍꢀꢃꢆꢁ ꢇꢆ% %ꢀꢎꢎꢊꢅꢊꢆꢍ ꢏꢃꢆꢃꢌ ꢅꢃꢏꢇꢍꢀꢌ ꢈꢀ& ꢍ ꢀꢅꢅꢇ%ꢀꢇꢍꢀꢃꢆꢓ
corresponding narrow band-pass filters, and then the wavelength-
dependent AQY values are calculated based on the H2 production
rate and corresponding incident monochromatic light intensity
according to equation 2 which has been shown in experimental
section. The results in Fig. 6 show the comparison of the DRS
spectra and AQY values as a function of the incident monochromatic
light wavelength of g-C3N4 and Zn-di-PcNcTh/g-C3N4 without
coadsorption of CDCA. It is evident that AQY values of Zn-di-
PcNcTh/g-C3N4 correspond with its DRS spectrum. It is worthy of
mention that Zn-di-PcNcTh/g-C3N4 shows considerably good AQY
values of 2.44%, 3.02% under 700 and 735 nm monochromatic light
irradiation, respectively. This result indicates that Zn-di-PcNcTh is
an efficient dye for g-C3N4 photoactivity H2 production.
Ascorbic acid (AA) as sacrificial reagent and λ ≥ 420 nm light
irradiation are used to further optimize the photoreaction condition
of Zn-di-PcNcTh/g-C3N4 and the corresponding results are shown in
Fig. 4. The H2 production efficiency of Zn-di-PcNcTh/g-C3N4 at λ ≥
420 nm light irradiation are similar to that under λ ≥ 500 nm light
irradiation with AA as sacrificial reagent.4 As can be seen, optimal
photoreaction conditions would be: 10 mg 1.0 wt % Pt-loaded g-
C3N4 sensitized with Zn-di-PcNcTh dye, dispersed in 50 mM AA
water solution (10 mL). In addition to the above conditions, the dye
absorbed amount have been studied. As light harvester and
photoelectron generator, Zn-di-PcNcTh plays the major role in a dye
sensitized photocatalytic system. As Fig. 4 shown, the photocatalytic
H2 production rate is improved dramatically by increasing adsorbed
amount of Zn-di-PcNcTh. However, the photoactivity remained
stable when the adsorbed amount of Zn-di-PcNcTh exceeded 5.0
µmol g-1. This phenomenon should be reasonable in terms of the
competitive relation between light harvesting and active sites for H2
production. On the other hand, CDCA as a coadsorbent which
reduces the dye aggregation, is commonly used in ZnPc-sensitized
solar cells to improve cell performance. However, some ZnPc
derivatives with large steric hindrance by introducing bulky
diphenylphenoxy substitutions can effectively retard ZnPc molecular
/ꢀꢃꢍꢅꢁꢌꢓꢀꢃꢌ
A novel highly asymmetric zinc phthalocyanine derivative (Zn-
di-PcNcTh) containing a π electron rich thiophene ring acting
as electron donor, a carboxyl-naphthalene unit as electron
acceptor and diphenylphenoxy to retard the aggregation has
been successfully synthesized for developing red/near-IR
responsive dyes of Pt-loaded graphitic carbon nitride for
photocatalytic H2 production. Ultraviolet-visible light (UV-vis),
aggregates. Zn-di-PcNcTh with four diphenylphenoxy substitutions diffuse
reflectance
absorption
spectra
(DRS),
also can effectively suppress molecular aggregates, then an photoluminescence (PL) spectra, time-resolved photoluminesc-
impressive photocatalytic H2 production rate was obtained without ence spectra (TRPS), and energy band structure analyses are
adding CDCA.
adopted to investigate the photogenerated electron transfer
The transient photocurrent behavior of Zn-di-PcNcTh-sensitized process between Zn-di-PcNcTh and g-C3N4. After optimizing
g-C3N4 suspension under λ ≥ 420 nm light irradiation are shown in
Fig. S11.† It is evident that the dye-sensitized g-C3N4 exhibits higher
photocurrent than g-C3N4, illustrating the effective and fast electron
transfer from Zn-di-PcNcTh to g-C3N4. Fig. 5 depicts the long-term
photostability for H2 production of Zn-di-PcNcTh/g-C3N4 system
without adding CDCA under the above-mentioned conditions. As
can be seen, Zn-di-PcNcTh/g-C3N4 shows excellent photoactivity
and rather good stability for H2 production under λ ≥ 420 nm light
irradiation. The average H2 production efficiency is 208.8 µmol h-1
in the first 10 h and 195.5 µmol h-1 in the second 10 h. Although the
photoactivity have decreased to some extent during a second 10 h
irradiation after remaining in darkness overnight, it still can be
the photocatalytic condition Zn-di-PcNcTh sensitized g-C3N4
photocatalyst shows a H2 production efficiency of 249 µmol h-1
under visible/near-IR-light irradiation without adding CDCA,
corresponding to a TON of 9960.8 h-1. Zn-di-PcNcTh/g-C3N4
gives an extremely high apparent quantum yield (AQY) of
2.44%, 3.05%, 1.53% at 700, 730, 800 nm monochromatic light
irradiation.
!ꢍ1ꢃꢀꢊꢅꢇꢔꢎꢇꢆꢇꢃꢑꢌ
This work is supported by the Natural Science Foundation of
China (21573166, 21271146, 21271144, and 20973128), the
Ç ꢀꢁ ꢂꢃꢄꢅꢆꢇꢈ ꢀꢁ ꢉ Ç ꢊ wꢃꢋꢇꢈ {ꢃꢌꢀꢊꢍꢋ ꢃꢎ / ꢊꢏꢀꢁꢍꢅꢋ ꢐꢑꢒꢒ
Wꢀ bꢁꢂꢃꢓꢔ ꢐꢑ !ꢔ ꢈꢈꢔ "! # 0
tꢈꢊꢇꢁꢊ %ꢃ ꢆꢃꢍ ꢇ%ꢂꢄꢁꢍ ꢏꢇꢅ&ꢀꢆꢁ

tꢈꢊꢇꢁꢊ %ꢃ ꢆꢃꢍ ꢇ%ꢂꢄꢁꢍ ꢏꢇꢅ&ꢀꢆꢁ
Dalton Transactions
Page 8 of 8
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DOI: 10.1039/C6DT01248E
!wÇL/[9
Wꢀꢁꢂꢃꢄꢅ bꢄꢆꢇ
30 L. Yu, X. Zhou, Y. Yin, Y. Liu, R. Li and T. Peng,
ChemPlusChem, 2012, 77, 1022-1027.
31 M. J. Cook and A. Jafari-Fini, Tetrahedron, 2000, 56, 4085-
4094.
Funds for Creative Research Groups of Hubei Province
(2014CFA007) and Natural Science Foundation of Jiangsu
Province (SBK2015020824).
32 T. Kimura, T. Iwama, T. Namauo, E. Suzuki, T. Fukuda, N.
Kobayashi, T. Sasamori and N. Tokitoh, Eur. J. Inorg.
Chem., 2011, 2011, 888-894.
bꢀꢑꢇꢌ ꢄꢃꢔ ꢂꢇꢖꢇꢂꢇꢃꢍꢇꢌ
33 T. V. Dubinina, N. E. Borisova, M. V. Sedova, L. G.
Tomilova, T. Furuyama and N. Kobayashi, Dyes and
Pigments, 2015, 117, 1-6.
34 S. Mori, M. Nagata, Y. Nakahata, K. Yasuta, R. Goto, M.
Kimura and M. Taya, J. Am. Chem. Soc., 2010, 132, 4054-
4055.
35 M. E. Ragoussi, J. J. Cid, J. H. Yum, G. de la Torre, D. Di
Censo, M. Gratzel, M. K. Nazeeruddin and T. Torres, Angew.
Chem. Int. Ed., 2012, 51, 4375-4378.
36 C. B. Nielsen and T. Bjørnholm, Org. Lett., 2004, 6, 3381-
3384.
1
A. Kubacka, M. Fernandez-Garcia and G. Colon, Chem. Rev.
2012, 112, 1555-1614.
Y. Qu and X. Duan, Chem. Soc. Rev., 2013, 42, 2568-2580.
K. S. Joya, Y. F. Joya, K. Ocakoglu and R. van de Krol,
Angew. Chem. Int. Ed., 2013, 52, 10426-10437.
X. Zhang, L. Yu, C. Zhuang, T. Peng, R. Li and X. Li, ACS
Catal., 2014, 4, 162-170.
J. Zhu, P. Xiao, H. Li and S. A. C. Carabineiro, ACS Appl.
Mater. Interfaces, 2014, 6, 16449-16465.
X. Wang, S. Blechert and M. Antonietti, ACS Catal., 2012, 2,
1596-1606.
H. Yan and Y. Huang, Chem. Commun., 2011, 47, 4168-
4170.
X. Zhang, B. Peng, S. Zhang and T. Peng, ACS Sustainable
Chem. Eng., 2015, 3, 1501-1509.
,
2
3
4
5
6
7
8
9
37 A. Saeki, S. Yoshikawa, M. Tsuji, Y. Koizumi, M. Ide, C.
Vijayakumar and S. Seki, J. Am. Chem. Soc., 2012, 134,
19035-19042.
38 X. Zhang, T. Peng, L. Yu, R. Li, Q. Li and Z. Li, ACS Catal.
,
2015, 5, 504-510.
39 L. Yu, L. Lin, Y. Liu and R. Li, J. Mol. Graph. Model., 2015,
59, 100-106.
40 R. Li, D. Qi, J. Jiang and Y. Bian, J. Porphyrins
Phthalocyanines, 2010, 14, 421-437.
41 L. Yu, X. Zhang, C. Zhuang, L. Lin, R. Li and T. Peng, Phys.
X. Fan, L. Zhang, R. Cheng, M. Wang, M. Li, Y. Zhou and J.
Shi, ACS Catal., 2015, 5, 5008-5015.
10 S. Cao and J. Yu, J. Phys. Chem. Lett., 2014, 5, 2101-2107.
11 Y. Ye, N. D. Ball, J. W. Kampf and M. S. Sanford, J. Am.
Chem. Soc., 2010, 132, 14682-14687.
12 J. Zhang, X. Chen, K. Takanabe, K. Maeda, K. Domen, J. D.
Epping, X. Fu, M. Antonietti and X. Wang, Angew. Chem. Int.
Ed., 2010, 49, 441-444..
13 Y. Di, X. Wang, A. Thomas and M. Antonietti,
ChemCatChem, 2010, 2, 834-838.
14 J. Liu, Y. Zhang, L. Lu, G. Wu and W. Chen, Chem.
Commun., 2012, 48, 8826-8828.
Chem. Chem. Phys., 2014, 16, 4106-4114.
42 K. Kilså, E. I. Mayo, B. S. Brunschwig, H. B. Gray, N. S.
Lewis and J. R. Winkler, J. Phys. Chem. B, 2004, 108, 15640-
15651.
43 Y. Zhang, P. Ma, P. Zhu, X. Zhang, Y. Gao, D. Qi, Y. Bian,
N. Kobayashi and J. Jiang, J. Mater. Chem., 2011, 21, 6515-
6524.
44 J. He, G. Benkö, F. Korodi, T. Polívka, R. Lomoth, B.
Åkermark, L. Sun, A. Hagfeldt and V. Sundström, J. Am.
Chem. Soc., 2002, 124, 4922-4932.
45 X. Zhang, L. Yu, R. Li, T. Peng and X. Li, Catal. Sci.
Technol., 2014, 4, 3251-3260.
15 K. Takanabe, K. Kamata, X. Wang, M. Antonietti, J. Kubota
and K. Domen, Phys. Chem. Chem. Phys., 2010, 12, 13020-
13025.
16 S. Min and G. Lu, J. Phys. Chem. C, 2012, 116, 19644-
19652.
17 J. Xu, Y. Li, S. Peng, G. Lu and S. Li, Phys. Chem. Chem.
Phys., 2013, 15, 7657-7665.
18 T. T. Le, M. S. Akhtar, D. M. Park, J. C. Lee and O. B. Yang,
Appl. Catal., B 2012, 111-112, 397-401.
46 M. Zhu, Z. Li, B. Xiao, Y. Lu, Y. Du, P. Yang and X. Wang,
ACS Appl. Mater. Interfaces, 2013, 5, 1732-1740.
47 Y. Liu, C.-Y. Liu and Y. Liu, Applied Surface Science, 2011,
257, 5513-5518.
19 R. Abe, K. Shinmei, K. Hara and B. Ohtani, Chem. Commun.
,
2009, 3577-3579.
20 R. Abe, K. Shinmei, N. Koumura, K. Hara and B. Ohtani, J.
Am. Chem. Soc., 2013, 135, 16872-16884.
21 X. Zhang, U. Veikko, J. Mao, P. Cai and T. Peng, Chemistry
2012, 18, 12103-12111.
,
22 S. A. Berhe, Z. B. Molinets, M. N. Frodeman, B. Miller, V.
N. Nesterov, K. M. Haynes, C. M. Perry, M. T. Rodriguez, R.
N. McDougald and W. J. Youngblood, J. Porphyrins
Phthalocyanines, 2015, 19, 1021-1031.
23 X. Chen, S. Shen, L. Guo and S. S. Mao, Chem. Rev., 2010,
110, 6503-6570.
24 X. Zhang, L. Yu, C. Zhuang, T. Peng, R. Li and X. Li, RSC
Adv., 2013, 3, 14363.
25 Y. Zhang, F. Mao, H. Yan, K. Liu, H. Cao, J. Wu and D.
Xiao, J. Mater. Chem. A, 2015, 3, 109-115.
26 Y. Wang, J. Hong, W. Zhang and R. Xu, Catal. Sci. Technol.
,
2013, 3, 1703-1711.
27 D. Wang, J. Huang, X. Li, P. Yang, Y. Du, C. M. Goh and C.
Lu, J. Mater. Chem. A, 2015, 3, 4195-4202.
28 L. Yu, W. Shi, L. Lin, Y. Guo, R. Li and T. Peng, Dyes and
Pigments, 2015, 114, 231-238.
29 L. Lin, B. Peng, W. Shi, Y. Guo and R. Li, Dalton Trans.
2015, 44, 5867-5874.
,
2 # Wꢀ bꢁꢂꢃꢓꢔ ꢐꢑ ꢐꢔ ꢈꢈꢔ "!
Ç ꢀꢁ ꢂꢃꢄꢅꢆꢇꢈ ꢀꢁ ꢉ Ç ꢊ wꢃꢋꢇꢈ {ꢃꢌꢀꢊꢍꢋ ꢃꢎ / ꢊꢏꢀꢁꢍꢅꢋ ꢐꢑꢒꢒ
tꢈꢊꢇꢁꢊ %ꢃ ꢆꢃꢍ ꢇ%ꢂꢄꢁꢍ ꢏꢇꢅ&ꢀꢆꢁ