Hierarchical integration of photosensitizing metal-organic frameworks and nickel-containing polyoxometalates for efficient visible-light-driven hydrogen evolution

Article abstract of DOI:10.1002/anie.201600431

Metal-organic frameworks (MOFs) provide a tunable platform for hierarchically integrating multiple components to effect synergistic functions that cannot be achieved in solution. Here we report the encapsulation of a Ni-containing polyoxometalate (POM) [Ni₄(H₂O)₂(PW₉O₃₄)₂]^10- (Ni₄P₂) into two highly stable and porous phosphorescent MOFs. The proximity of Ni₄P₂ to multiple photosensitizers in Ni₄P₂@MOF allows for facile multi-electron transfer to enable efficient visible-light-driven hydrogen evolution reaction (HER) with turnover numbers as high as 1476. Photophysical and electrochemical studies established the oxidative quenching of the excited photosensitizer by Ni₄P₂ as the initiating step of HER and explained the drastic catalytic activity difference of the two POM@MOFs. Our work shows that POM@MOF assemblies not only provide a tunable platform for designing highly effective photocatalytic HER catalysts but also facilitate detailed mechanistic understanding of HER processes. POM & MOF work hand in hand: A tetra-nickel-containing polyoxometalate (POM) was encapsulated into the pores of phosphorescent metal-organic frameworks (MOFs). The hierarchical POM@MOF assemblies effect highly efficient photocatalytic hydrogen evolution reactions through facile multielectron transfer processes.

Full text of DOI:10.1002/anie.201600431

Angewandte
Communications
Chemie
International Edition: DOI: 10.1002/anie.201600431
German Edition: DOI: 10.1002/ange.201600431
Hydrogen Evolution
Hierarchical Integration of Photosensitizing Metal–Organic
Frameworks and Nickel-Containing Polyoxometalates for Efficient
Visible-Light-Driven Hydrogen Evolution
Xiang-Jian Kong, Zekai Lin, Zhi-Ming Zhang, Teng Zhang, and Wenbin Lin*
Abstract: Metal–organic frameworks (MOFs) provide a tuna-
ble platform for hierarchically integrating multiple compo-
nents to effect synergistic functions that cannot be achieved in
solution. Here we report the encapsulation of a Ni-containing
polyoxometalate (POM) [Ni4(H2O)2(PW9O34)2]10À (Ni4P2)
into two highly stable and porous phosphorescent MOFs.
The proximity of Ni4P2 to multiple photosensitizers in
Ni4P2@MOF allows for facile multi-electron transfer to
enable efficient visible-light-driven hydrogen evolution reac-
tion (HER) with turnover numbers as high as 1476. Photo-
physical and electrochemical studies established the oxidative
quenching of the excited photosensitizer by Ni4P2 as the
initiating step of HER and explained the drastic catalytic
activity difference of the two POM@MOFs. Our work shows
that POM@MOF assemblies not only provide a tunable
platform for designing highly effective photocatalytic HER
catalysts but also facilitate detailed mechanistic understanding
of HER processes.
pairs) is followed by facile transfer of the electrons to HER
centers to reduce proton to hydrogen.[10] Recent studies have
shown the feasibility of integrating the two essential compo-
nents—the photosensitizer and the HER catalyst—into
MOFs to enable light-driven proton reduction.[11–13] For
example, by loading noble metal Pt nanoparticles into the
cavities of a photosensitizing MOF, we showed that the
Pt@MOF system facilitated electron injection from the MOF
framework to the encapsulated Pt nanoparticles to enable
photocatalytic proton reduction with a high turnover number
of ca. 7000.[13]
As a large family of nano-sized inorganic clusters with
oxygen-rich surfaces, polyoxometalates (POMs) can readily
undergo multi-electron reduction and oxidation processes,
thus representing excellent candidates as HER and water
oxidation catalysts.[14,15] In order to transition to HER
catalysts based on earth-abundant elements, we recently
used the noble-metal-free Wells-Dawson POM [P2W18O62]6À
as the electron acceptor to construct the POM@MOF
molecular catalytic system for photocatalytic HER.[15] The
[P2W18O62]@MOF system enabled visible-light-driven HER
as a result of fast six-electron injection from multiple [Ru-
(bpy)3]2+ ligands to each encapsulated [P2W18O62]6À cluster,
but at a modest TON of 79. In this system, methanol functions
as a sacrificial donor, which is interesting with few literature
precedents.[16] Transition-metal-substituted POMs have
recently been shown to possess higher visible-light photo-
catalytic activity, because of their extensive tunability, rich
redox chemistry, and synergism between the heterometallic
ions.[17,18] Herein we report the design of a highly effective
photocatalytic HER system by encapsulating Ni-containing
POM [Ni4(H2O)2(PW9O34)2]10À (Ni4P2) into [Ir(ppy)2(bpy)]+-
derived UiO-MOF (ppy is 2-phenylpyridine and bpy is 2,2’-
bipyridine). We also carried out detailed photophysical and
electrochemical studies to establish the HER mechanism and
to account for the catalytic activity difference between two
different Ni4P2@MOFs.
M
etal–organic frameworks (MOFs) have attracted consid-
erable attention for their unprecedentedly high surface areas
and well-defined pore structures that can be readily tuned via
judicious selection of bridging ligands and metal-connecting
nodes.[1,2] In particular, potential applications of MOFs in gas
storage and separations have been extensively studied in the
past decade.[2,3] By introducing catalytically competent moi-
eties via either the bridging ligands or the metal-connecting
nodes, MOFs have also emerged as a new class of recyclable
and reusable single-site solid catalysts for a broad range of
organic transformations.[4,5] Encapsulation of metal and
metal-oxide (such as Au, Pd, Pt, ZnO) nanoparticles in
MOF cavities has recently been demonstrated to be another
effective strategy for preparing heterogeneous catalysts with
high activities.[6,7]
Photocatalytic hydrogen evolution reaction (HER) is an
essential half reaction of water splitting,[8,9] in which effective
generation of charge-separated excited states (electron-hole
The [Ir(ppy)2(bpy)]+-derived dicarboxylic acid (H2L1) or
[Ru(bpy)3]2+-derived dicarboxylic acid (H2L2) was synthe-
sized as reported previously.[12,15] MOF-1, formulated as
[Zr6(m3-O)4(m3-OH)4(L1)6]·(CF3CO2)6, and MOF-2, formu-
lated as [Zr6(m3-O)4(m3-OH)4(L2)6]·(CF3CO2)12, were obtained
by treating ZrCl4 and H2L1/H2L2 in DMF at 1008C for 72 h.
Ni4P2@MOF-1 (1a–1 f) and Ni4P2@MOF-2 (2a–2 f) were
prepared via in situ assembly by heating a mixture of ZrCl4,
H2L1/H2L2 and Ni4P2 at different molar ratios. Powder X-ray
diffraction (PXRD) studies show that both MOF-1 and MOF-
2 adopt UiO structures with large tetrahedral and octahedral
cavities (Figure 1).[19] Based on charge balance, six and twelve
[*] Dr. X. J. Kong, Z. Lin, Dr. Z. M. Zhang, T. Zhang, Prof. W. Lin
Department of Chemistry, University of Chicago
929 E. 57th Street, Chicago, IL 60637 (USA)
E-mail: wenbinlin@uchicago.edu
Dr. X. J. Kong, Dr. Z. M. Zhang, Prof. W. Lin
Collaborative Innovation Center of Chemistry for Energy Materials,
Department of Chemistry, College of Chemistry and Chemical
Engineering, Xiamen University
Xiamen 361005 (P.R. China)
Supporting information for this article can be found under:
http://dx.doi.org/10.1002/anie.201600431.
Angew. Chem. Int. Ed. 2016, 55, 6411 –6416
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
6411

Angewandte
Communications
Chemie
methanol as the sacrificial electron donor. The amounts of H2
generated were quantified by gas chromatography analysis of
the headspace gas in the reactor. H2 production increased
linearly with time at a rate of 4.4 mmolhÀ1 gÀ1 with respect to
[Ni4(H2O)2(PW9O34)2]10À for 1a (Figure 2c). The turnover
number (TON) [defined as n(1/2H2)] reached 1476 in 72 h
irradiation. The HER TON of 1a–1d inversely depended on
the Ni4P2 loading in the POM@MOF, which is consistent with
the need of injecting multiple electrons in the HER process
(Figure S8).
The Ni4P2@MOF-1 catalyst was recovered and used for
photocatalytic HER for three times with only a slight
decrease of TON (346 Æ 53, 329 Æ 77, 297 Æ 65; Figure S9).
ICP-MS studies showed that only 0.2% Ir leached into the
solution after 20 h photocatalytic HER. Transmission elec-
tron microscope (TEM) images of Ni4P2@MOF-1 remained
unchanged before and after photocatalysis (Figure S10),
whereas PXRD patterns of the solid recovered after 20 h
reactions were similar to those of the pristine Ni4P2@MOF-
1 catalyst (Figure 2d). We also performed elemental mapping
and EDX studies of POM elements of Ni4P2@MOF before
and after photocatalytic experiments. As shown in Fig-
ure S11–S13, the W, Ni, P elements are uniformly distributed
throughout the microcrystals, suggesting the stability of Ni4P2
during the POMOF synthesis and the photocatalytic HER
reaction. Ni4P2@MOFs before and after photocatalytic
experiments were digested and analysed with ESI-MS to
confirm the stability of Ni4P2 (Table S4–S5, Figure S4–S5).
Control experiments using MOF-1 without encapsulated
Ni4P2 and homogeneous mixtures of [Ni4(H2O)2(PW9O34)2]10À
and Me2L1 produced only trace amounts of H2 (with TONs
< 13 and 2) after 20 h of visible-light irradiations. These
results indicate that the Ni4P2@MOF-1 catalyst is stable and
the hierarchical organization of the photosensitizing frame-
work and the Ni4P2 POM in Ni4P2@MOF-1 is responsible for
the high photocatalytic HER. The actinometric measurement
with 460 nm light irradiation showed that 1a has a modest
quantum efficiency (QE) of 2 ” 10À5.
Figure 1. a) Chemical structures of H2L1 and H2L2. b) Polyhedral view
of the structure of [Ni4(H2O)2(PW9O34)2]10À (Ni4P2). c) Structural model
of Ni4P2@MOF as viewed along the [1,1,1] direction. d) Structural
model showing unoccupied tetrahedral cavities and the central Ni4P2-
loaded octahedral cavity.
À
CF3CO2 anions per molecular formula are present in the
cavities of MOF-1 and MOF-2, respectively. The large
cationic polyhedral cavities in the UiO structures are ideally
suited for the encapsulation of the anionic Ni4P2 POM. As the
Ni4P2 loading increased, the strong diffraction peaks at 2q =
3.96 and 7.928 became weaker while the weak diffraction
peaks at 2q = 4.56, 6.56 and 7.568 became stronger in 1a–1 f
(Figure 2). A similar trend was also observed for 2a–2 f. Since
the tetrahedral cage of 1.4 nm is smaller than the large
dimension of the Ni4P2 POM (1.6 nm), only octahedral cages
(2.2 nm) can encapsulate Ni4P2 POMs (Figure S3 in the
Supporting Information). The selective encapsulation in
octahedral cages is supported by the similarity between the
observed and simulated PXRDs of the POM@MOF (Fig-
ure 2a).
The loadings of Ni4P2 in Ni4P2@MOF-1 and Ni4P2@MOF-
2 were quantified by inductively coupled plasma-mass
spectrometry (ICP-MS). The Ni4P2 loadings were in the
range of 0.005–0.34 for 1a–1 f and 0.008–0.53 for 2a–2 f per
molecular formula (calculated based on the ratio of W18/Zr6,
Table S3). Thermogravimetric analysis results for 1a–1 f and
2a–2 f (Figures S6 and S7) were consistent with these load-
ings. The stability of Ni4P2 during the POM@MOF synthesis
was supported by electrospray ionization-mass spectrometry
(ESI-MS) (Figure S4). The observed peaks are consistent
with the calculated mass for POM-related species (Table S4),
suggesting the chemical stability of Ni4P2 during Ni4P2@MOF
synthesis.
The [Ru(bpy)3]2+-derived Ni4P2@MOF 2a–2d were also
used in photocatalytic H2 production experiments. To our
surprise, 2a–2e only gave trace amounts of H2 after 20 h
visible-light irradiations under the same photocatalytic con-
ditions as 1a (Table S6). The HER TONs are ꢀ 3 for 2a and
ꢀ 1 for 2b–2e. This background-level TON values indicates
that the [Ru(bpy)3]2+-derived Ni4P2@MOF-2 are inactive for
photocatalytic HER.
To investigate the HER mechanism, we studied electron
transfer processes by luminescence quenching and lifetime
measurements. The photosensitizer excited state can be
quenched either reductively (by the methanol electron
donor) or oxidatively (by the Ni4P2 electron acceptor),
which can be ascertained by measuring the luminescence of
Me2L1 and Me2L2 with added methanol or Ni4P2. As shown in
Figure 3c and 3d, the luminescence of Me2L1 was efficiently
quenched by Ni4P2 but was not affected much by the added
methanol, suggesting that the first step of photocatalytic HER
mainly occurs via electron transfer from the photosensitizer
excited state to Ni4P2 (i.e., oxidative quenching) but not via
electron transfer from methanol to the photo-generated
The integration of the photosensitizing MOF framework
and the POM catalyst allows for facile electron transfer to
enable photocatalytic proton reduction. The visible-light-
driven (l > 400 nm) HER catalytic activities of Ni4P2@MOFs
were studied in an acidic aqueous solution (pH 1.2) with
6412
www.angewandte.org
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2016, 55, 6411 –6416

Angewandte
Communications
Chemie
Figure 2. a) Predicted and experimental PXRD patterns of MOF-1 and Ni4P2@MOF-1 (1a–1 f). b) Predicted and experimental PXRD patterns of
MOF-2 and Ni4P2@MOF-2 (2a–2 f). c) Time-dependent TONs of 1a with methanol as the sacrificial electron donor in aqueous solution (pH 1.2)
under visible-light (l>400 nm) irradiations. d) PXRD of 1a before and after photocatalytic reaction.
electron-hole pair of the photosensitizer (i.e., reductive
quenching). This oxidative quenching mechanism is further
supported by time-resolved photoluminescence measure-
ments of MOF-1, 1a–1 f, MOF-2, and 2a–2 f. As shown in
Table S8, MOF-1 exhibited a lifetime of 201 ns upon excita-
tion at 405 nm, consistent with the long-lived 3MLCT
phosphorescence emission. The lifetimes are 154, 166, 166,
142,133, and 74.8 ns for 1a–1 f. Lifetimes of the ligand Me2L1
and homogeneous solutions of Me2L1 and Ni4P2 are 77.9, 77.8,
77.6, 76.9, 75.4, 68.9 and 59.4 ns, respectively. Comparisons of
lifetime decreases of Ni4P2@MOFs and corresponding homo-
geneous solutions caused by the quencher indicate that
Ni4P2@MOF exhibited enhanced quenching, which can be
attribute to the facile electron transfer from the excited
photosensitizer to the POM due to their proximity to each
other.
injection of three electrons. This is supported by differential
pulse voltammetry which showed a proton reduction peak at
À0.66 eV for Ni4P2 (Figure 4b). Based on these experimental
data, we propose the photocatalytic HER mechanism in
Scheme 1 for Ni4P2@MOF-1. Under the visible-light irradi-
ation, the ligand [Ir(ppy)2(bpy)]+ will be excited to the
[Ir(ppy)2(bpy)]+* excited state, which can transfer one
Cyclic voltammograms (CVs) of the photosensitizer and
Ni4P2 were studied to provide additional insights into the H2
production mechanism. Ni4P2 shows two reversible reduction
peaks at À0.37 and À0.55 V vs. NHE and an irreversible
catalytic peak with an onset potential of À0.65 V (Figure 4),
suggesting that the H2 production commences upon the
Scheme 1. Proposed catalytic cycle for visible-light-driven hydrogen
evolution catalyzed by Ni4P2@MOF-1.
Angew. Chem. Int. Ed. 2016, 55, 6411 –6416
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
6413

Angewandte
Communications
Chemie
Figure 3. a) Schematic showing the injection of three electrons to the same Ni4P2 upon photoexcitation of the MOF framework to enable proton
reduction. b) Normalized luminescence decay trace of Ni4P2@MOF-1a and MOF-1 measured at the 625 nm emission wavelength (with 405 nm
excitation) in CH3CN; the emission decays were fit to exponential expression A=A0 +A1eÀt/t1. The fitted curve is marked in red. c,d) Emission
spectra of Me2L1 (0.05 mm) after the addition of different amounts of Ni4P2 (c) and 300 mL MeOH (d) in CH3CN with 405 nm excitation.
electron to the Ni4P2 POM to generate [Ir(ppy)2(bpy)]2+.
After each POM has accepted three electrons, the [POM]3À
can drive the proton reduction to generate H2. The [Ir(ppy)-
(bpy)]2+ can be reduced back to the [Ir(ppy)(bpy)]+ by the
MeOH sacrificial donor to complete the catalytic cycle. We
quantified the amount of formaldehyde formed from the
oxidation of methanol by gas chromatography-mass spec-
trometry (GC-MS).[20] After 20 hours of visible-light irradi-
ation, the POM@MOF-1a produced 0.27 umol of formalde-
hyde, which is consistent with the expected value of 0.24 umol.
CV scans showed that Me2L1 and Me2L2 displayed
oxidation peaks at 1.38 and 1.34 eV, respectively (Figure 4c).
As shown in Figure 4d, Me2L1 and Me2L2 exhibits lumines-
cence emission peaks at 598 nm and 633 nm, respectively.
These correspond to energy gaps between the photosensitizer
excited state and ground state of 2.08 and 1.96 eV for Me2L1
and Me2L2, respectively. Based on the energy loop as shown in
Scheme 1, the energy difference DE’ between [Ir(ppy)2-
(bpy’)]+* and [Ir(ppy)2(bpy)]2+ is 1.38–2.08 = À0.70 eV,
which is negative enough (compared to À0.65 eV for proton
reduction by Ni4P2) to drive the H2 production. In contrast,
the energy gap DE’ between [Ru(bpy)2(bpy’)]2+* and [Ru-
(bpy)2(bpy’)]3+ is 1.34–1.96 = À0.62 eV, which is not negative
enough to drive H2 production by Ni4P2. This analysis thus
explains why 2a–2 f are inactive for photocatalytic HER with
methanol as the sacrificial electron donor.
In summary, we have successfully encapsulated tetra-
nickel-containing Ni4P2 POMs into the pores of phosphor-
escent MOFs built from [Ir(ppy)2(bpy)]+ and [Ru(bpy)3]2+-
derived dicarboxylate ligands. Visible-light-driven hydrogen
evolution experiments show that the proximity of Ni4P2 to
multiple photosensitizers in Ni4P2@MOF is key to facile
multi-electron transfer and efficient HER. Photophysical and
electrochemical studies established the oxidative quenching
of the photosensitizer excited state by Ni4P2 as the initiating
step of HER and explained the drastic catalytic activity
difference between the two POM@MOF systems. Hierarchi-
cally organized POM@MOF assemblies thus not only provide
6414
www.angewandte.org
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2016, 55, 6411 –6416

Angewandte
Communications
Chemie
Figure 4. a) Cyclic voltammograms (CVs) of 0.2 mm Ni4P2 in a 2m NaCl aqueous solution (pH 1.2). b,c) Differential pulse voltammetry (DPV) of
0.2 mm Ni4P2 (b) and 0.2 mm Me2L1 and Me2L2 (c) in a 2m NaCl aqueous solution (pH 1.2) with a scan rate of 100 mVsÀ1. d) Emission spectra of
Me2L1 and Me2L2 in aqueous solution (pH 1.2) with 360 nm excitation for Me2L1 and 400 nm excitation for Me2L2.
Chem. Rev. 2012, 112, 782 – 835; c) J. P. Zhang, Y. B. Zhang, J. B.
a tunable platform for achieving synergistic functions from
Lin, X. M. Chen, Chem. Rev. 2012, 112, 1001 – 1033; d) B. Chen,
C. Liang, J. Yang, D. S. Contreras, Y. L. Clancy, E. B. Lobkovsky,
O. M. Yaghi, S. Dai, Angew. Chem. Int. Ed. 2006, 45, 1390 – 1393;
multiple components but also facilitate mechanistic studies of
these processes.
Angew. Chem. 2006, 118, 1418 – 1421.
˘
[3] a) L. J. Murray, M. Dinca, J. R. Long, Chem. Soc. Rev. 2009, 38,
1294 – 1314; b) Z. Guo, H. Wu, G. Srinivas, Y. Zhou, S. Xiang, Z.
Chen, Y. Yang, W. Zhou, M. OKeeffe, B. Chen, Angew. Chem.
Int. Ed. 2011, 50, 3178 – 3181; Angew. Chem. 2011, 123, 3236 –
3239.
Acknowledgements
We acknowledge funding from the U.S. National Science
Foundation (DMR-1308229) and the National Natural Sci-
ence Foundation of China (21471126 and 21422106). X.J.K.
acknowledges the State Scholarship Fund from the China
Scholarship Council (CSC). We thank K. Lu, X. Zhou, Y. Fu
and C. Poon for experimental help and discussions.
[4] a) A. Dhakshinamoorthy, H. Garcia, Chem. Soc. Rev. 2014, 43,
5750 – 5765; b) M. Yoon, R. Srirambalaji, K. Kim, Chem. Rev.
2012, 112, 1196 – 1231; c) M. Zhao, S. Ou, C. D. Wu, Acc. Chem.
Res. 2014, 47, 1199 – 1207; d) G. Q. Kong, S. Ou, C. Zou, C. D.
Wu, J. Am. Chem. Soc. 2012, 134, 19851 – 19857.
[5] a) L. Ma, C. Abney, W. Lin, Chem. Soc. Rev. 2009, 38, 1248 –
1256; b) C. Wang, D. Liu, W. Lin, J. Am. Chem. Soc. 2013, 135,
13222 – 13234; c) C. Y. Lee, O. K. Farha, B. J. Hong, A. A.
Sarjeant, S. T. Nguyen, J. T. Hupp, J. Am. Chem. Soc. 2011,
133, 15858 – 15861.
[6] a) A. Aijaz, A. Karkamkar, Y. J. Choi, N. Tsumori, E. Rçnnebro,
T. Autrey, H. Shioyama, Q. Xu, J. Am. Chem. Soc. 2012, 134,
13926 – 13929; b) G. Lu, S. Li, Z. Guo, O. K. Farha, B. G. Hauser,
X. Qi, Y. Wang, X. Wang, S. Han, X. Liu, J. S. DuChene, H.
Zhang, Q. Zhang, X. Chen, J. Ma, S. C. J. Loo, W. D. Wei, Y.
Yang, J. T. Hupp, F. Huo, Nat. Chem. 2012, 4, 310 – 316.
[7] a) A. Dhakshinamoorthy, H. Garcia, Chem. Soc. Rev. 2012, 41,
5262 – 5284; b) W. W. Zhan, Q. Kuang, J. Z. Zhou, X. J. Kong,
Z. X. Xie, L. S. Zheng, J. Am. Chem. Soc. 2013, 135, 1926 – 1933.
Keywords: hydrogen evolution reaction · metal–
organic frameworks · photocatalysis · polyoxometalate
How to cite: Angew. Chem. Int. Ed. 2016, 55, 6411–6416
Angew. Chem. 2016, 128, 6521–6526
[1] a) H. C. Zhou, J. R. Long, O. M. Yaghi, Chem. Rev. 2012, 112,
673 – 674; b) M. OꢀKeeffe, O. M. Yaghi, Chem. Rev. 2012, 112,
675 – 702; c) H. Wu, Q. Gong, D. H. Olson, J. Li, Chem. Rev.
2012, 112, 836 – 868; d) C. Wang, T. Zhang, W. Lin, Chem. Rev.
2012, 112, 1084 – 1104.
[2] a) J. Della Rocca, D. M. Liu, W. B. Lin, Acc. Chem. Res. 2011, 44,
957 – 968; b) M. P. Suh, H. J. Park, T. K. Prasad, D.-W. Lim,
Angew. Chem. Int. Ed. 2016, 55, 6411 –6416
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
6415

Angewandte
Communications
Chemie
[8] a) X. Chen, S. Shen, L. Guo, S. S. Mao, Chem. Rev. 2010, 110,
6503 – 6570; b) X. Wang, K. Maeda, A. Thomas, K. Takanable,
G. Xin, J. M. Carlsson, K. Domen, M. Antonietti, Nat. Mater.
2009, 8, 76 – 80; c) Z. Yu, F. Li, L. C. Sun, Energy Environ. Sci.
2015, 8, 760 – 775; d) M. Wang, K. Han, S. Zhang, L. C. Sun,
Coord. Chem. Rev. 2015, 287, 1 – 14.
Moll, L. M. R. Albelo, P. Mialane, J. Marrot, C. Mellot-
Draznieks, M. OꢀKeeffe, R. N. Biboum, J. Lemaire, B. Keita,
L. Nadjo, A. Dolbecq, J. Am. Chem. Soc. 2011, 133, 13363 –
13374.
[15] Z. M. Zhang, T. Zhang, C. Wang, Z. Lin, L. S. Long, W. Lin, J.
Am. Chem. Soc. 2015, 137, 3197 – 3200.
[9] a) W. M. Singh, T. Baine, S. Kudo, S. Tian, X. A. N. Ma, H. Zhou,
N. J. DeYonker, T. C. Pham, J. C. Bollinger, D. L. Baker, B. Yan,
C. E. Webster, X. Zhao, Angew. Chem. Int. Ed. 2012, 51, 5941 –
5944; Angew. Chem. 2012, 124, 6043 – 6046; b) F. Lakadamyali,
M. Kato, N. M. Muresan, E. Reisner, Angew. Chem. Int. Ed.
2012, 51, 9381 – 9384; Angew. Chem. 2012, 124, 9515 – 9518;
c) B. F. DiSalle, S. Bernhard, J. Am. Chem. Soc. 2011, 133,
11819 – 11821; d) S. Metz, S. Bernhard, Chem. Commun. 2010,
46, 7551 – 7553.
[10] a) H. Kind, H. Yan, B. Messer, M. Law, P. Yang, Adv. Mater.
2002, 14, 158 – 160; b) W. Hou, S. B. Cronin, Adv. Funct. Mater.
2013, 23, 1612 – 1619.
[11] a) T. Zhang, W. Lin, Chem. Soc. Rev. 2014, 43, 5982 – 5993;
b) J. H. Cavka, S. Jakobsen, U. Olsbye, N. Guillou, C. Lamberti,
S. Bordiga, K. P. Lillerud, J. Am. Chem. Soc. 2008, 130, 13850 –
13851; c) Y. Kataoka, K. Sato, Y. Miyazaki, K. Masuda, H.
Tanaka, S. Naito, W. Mori, Energy Environ. Sci. 2009, 2, 397 –
400.
[16] a) R. Irie, X. Li, Y. Saito, J. Mol. Catal. 1983, 18, 263 – 265; b) I.
Mena, M. A. Casado, V. Polo, P. García-OrduÇa, F. J. Lahoz,
L. A. Oro, Angew. Chem. Int. Ed. 2012, 51, 8259 – 8263; Angew.
Chem. 2012, 124, 8384 – 8388; c) H. N. Kagalwala, A. B. Maurer,
I. N. Mills, S. Bernhard, ChemCatChem 2014, 6, 3018 – 3026; d) F.
Guzman, S. S. C. Chuang, C. Yang, Ind. Eng. Chem. Res. 2013,
52, 61 – 65.
[17] a) H. Lv, W. Guo, K. Wu, Z. Chen, J. Bacsa, D. G. Musaev, Y. V.
Geletii, S. M. Lauinger, T. Lian, C. L. Hill, J. Am. Chem. Soc.
2014, 136, 14015 – 14018; b) J. Song, Z. Luo, D. K. Britt, H.
Furukawa, O. M. Yaghi, K. I. Hardcastle, C. L. Hill, J. Am.
Chem. Soc. 2011, 133, 16839 – 16846; c) K. von Allmen, R. MorØ,
R. Müller, J. Soriano-López, A. Linden, G. R. Patzke, Chem-
PlusChem 2015, 80, 1389 – 1398.
[18] a) X. B. Han, Y. G. Li, Z. M. Zhang, H. Q. Tan, Y. Lu, E. B.
Wang, J. Am. Chem. Soc. 2015, 137, 5486 – 5493; b) J. J. Stracke,
R. G. Finke, ACS Catal. 2014, 4, 79 – 89; c) H. Lv, Y. V. Geletii, C.
Zhao, J. W. Vickers, G. Zhu, Z. Luo, J. Song, T. Lian, D. G.
Musaev, C. L. Hill, Chem. Soc. Rev. 2012, 41, 7572 – 7589.
[19] J. H. Cavka, S. Jakobsen, U. Olsbye, N. Guillou, C. Lamberti, S.
Bordiga, K. P. Lillerud, J. Am. Chem. Soc. 2008, 130, 13850 –
13851.
[12] a) S. Pullen, H. Fei, A. Orthaber, S. M. Cohen, S. Ott, J. Am.
Chem. Soc. 2013, 135, 16997 – 17003; b) A. Fateeva, P. A. Chater,
C. P. Ireland, A. A. Tahir, Y. Z. Khimyak, P. V. Wiper, J. R.
Darwent, M. J. Rosseinsky, Angew. Chem. Int. Ed. 2012, 51,
7440 – 7444; Angew. Chem. 2012, 124, 7558 – 7562.
´
[20] W. Wardencki, J. Orlita, J. Namiesnik, Fresenius J. Anal. Chem.
[13] C. Wang, K. E. deKrafft, W. Lin, J. Am. Chem. Soc. 2012, 134,
7211 – 7214.
2001, 369, 661 – 665.
[14] a) B. Rausch, M. D. Symes, G. Chisholm, L. Cronin, Science
2014, 345, 1326 – 1330; b) J. S. Qin, D. Y. Du, W. Guan, X. J. Bo,
Y. F. Li, L. P. Guo, Z. M. Su, Y. Y. Wang, Y. Q. Lan, H. C. Zhou,
J. Am. Chem. Soc. 2015, 137, 7169 – 7177; c) B. Nohra, H. E.
Received: January 14, 2016
Published online: April 20, 2016
6416 www.angewandte.org
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2016, 55, 6411 –6416