Stable Heterometallic Cluster-Based Organic Framework Catalysts for Artificial Photosynthesis

Article abstract of DOI:10.1002/anie.201913284

A series of stable heterometallic Fe₂M cluster-based MOFs (NNU-31-M, M=Co, Ni, Zn) photocatalysts are presented. They can achieve the overall conversion of CO₂ and H₂O into HCOOH and O₂ without the assistance of additional sacrificial agent and photosensitizer. The heterometallic cluster units and photosensitive ligands excited by visible light generate separated electrons and holes. Then, low-valent metal M accepts electrons to reduce CO₂, and high-valent Fe uses holes to oxidize H₂O. This is the first MOF photocatalyst system to finish artificial photosynthetic full reaction. It is noted that NNU-31-Zn exhibits the highest HCOOH yield of 26.3 μmol g^?1 h^?1 (selectivity of ca. 100 %). Furthermore, the DFT calculations based on crystal structures demonstrate the photocatalytic reaction mechanism. This work proposes a new strategy for how to design crystalline photocatalyst to realize artificial photosynthetic overall reaction.

Full text of DOI:10.1002/anie.201913284

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
International Edition Chemie
www.angewandte.org
Accepted Article
Title: Stable Heterometallic Cluster-Based Organic Frameworks
Catalysts for Artificial Photosynthesis
Authors: Ya-Qian Lan, Long-Zhang Dong, Lei Zhang, Qing Huang,
Meng Lu, Wen-Xin Ji, and Jiang Liu
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201913284
Angew. Chem. 10.1002/ange.201913284
Link to VoR: http://dx.doi.org/10.1002/anie.201913284
http://dx.doi.org/10.1002/ange.201913284

Angewandte Chemie International Edition
10.1002/anie.201913284
COMMUNICATION
Stable Heterometallic Cluster-Based Organic Frameworks
Catalysts for Artificial Photosynthesis
Long-Zhang Dong, Lei Zhang, Jiang Liu*, Qing Huang, Meng Lu, Wen-Xin Ji and Ya-Qian Lan*
Abstract: Coupling CO
one photocatalyst has always been a challenging task in artificial
photosynthesis. Herein, we first report series of stable
heterometallic Fe M cluster-based MOFs (NNU-31-M, M = Co, Ni,
Zn) photocatalysts, which can achieve the overall conversion of CO
and H O to HCOOH and O without the assistance of additional
2
reduction with H
2
O oxidation reactions on
perform artificial photosynthetic overall reaction, because of their
two advantages. On the one hand, the heterometallic cluster can
a
simultaneously bear the active catalytic sites of CO
2
reduction
2
and oxidation half-reactions and possess accurate
2
H O
2
structural information. On the other hand, the heterometallic
cluster can gather and provide multi-electron transfer[7] for
photocatalytic reactions, and increase the synergistic effect of
2
2
sacrificial agent and photosensitizer. The heterometallic cluster units
and photosensitive ligands excited by visible light generate
separated electrons and holes. Then, low-valent metal M accepts
[
8]
oxidative and reductive active sites . However, heterometallic
cluster serving as photocatalyst still faces many problems such
electrons to reduce CO
O. This is the first MOF photocatalyst system to finish artificial
photosynthetic full reaction. It is noted that NNU-31-Zn exhibits the
2
, and high-valent Fe uses holes to oxidize
as poor water stability, low specific surface area and CO
2
H
2
adsorption ability. In particular, the molecular cluster catalysts
are hard to separate from reaction solution due to their
homogeneous nature.[9] In this regard, a lot of metal-organic
framework (MOF) photocatalysts have recently been explored to
solve above problems, and some of them have excellent
-
1
-1
highest HCOOH yield of 26.3 μmol g
h (selectivity of ca. 100%).
Furthermore, the DFT calculations based on crystal structures
demonstrate the photocatalytic reaction mechanism. This work
proposes a new strategy for how to design crystalline photocatalyst
to realize artificial photosynthetic overall reaction.
performance on CO
2
photoreduction.[10] But all these works, the
use of additional sacrificial agents in the reaction has not been
solved yet. Thus, if the heterometallic cluster molecules can be
assembled with photosensitive organic linkers to construct
stable heterometallic cluster-based MOFs that will further extend
their photocatalytic advantages such as i) improving the visible
light absorption and structural stability; ii) facilitating the
utilization of photogenerated electrons and holes (due to the
2
In recent years, increasing anthropogenic CO emissions have
[
1]
caused severe energy and environmental issues . In response
to these problems, a large number of research works had
concentrated on exploring effective ways to achieve the artificial
conversion of CO [
uses solar energy to convert CO
and O , it is hoped that CO can be reduced in H
value-added chemicals or fuels by artificial photosynthesis.
2]. Inspired by plant photosynthesis, which
and H O into carbohydrates
O to high
2
near electron-hole transport distance); iii) increasing CO
adsorption by porosity and exposing more active sites to activate
CO and H O molecules; iv) studying photocatalytic reaction
2
2
2
2
2
2
2
2
[
3]
mechanism by their well-defined structures to provide more
insights into structure-property correlations. Based on these
advantages, we believe that the construction of stable
heterogeneous heterometallic cluster-based MOF photocatalysts
However, considering the inherent chemical inertness of CO
and slow reaction kinetics, effective combination of CO
2
2
2
reduction and H O oxidation half-reactions (i.e. overall reaction)
in one photocatalytic system is still a daunting work. At present,
the overall reaction could be achieved by a few nanostructured
photocatalysts such as Z-scheme heterojunctions (e.g.,
is
a
promising strategy for the realization of artificial
photosynthetic overall reaction.
2 3
With this thought in mind, we chose the stable Fe M(μ -
4]
[5]
Cu
2
O/WO [
3
2 3 2
and α-Fe O /Cu O ). However, because of the
O)(OAc)
6
(H
2
O)
3
(Fe
2
M, M= Co, Ni, Zn) clusters[11] and
influences of defects, impure phases and complicated structural
components, there is still lack of sufficient and clear structural
information to identify the specific catalytic sites in these
catalysts. Thus, exploring crystalline photocatalytic system with
well-defined structure is considered as one of the most
promising choices to address these issues.[6]
photosensitive 4,4',4''-tricarboxytriphenylamine (TCA) ligand to
construct three stable heterometallic cluster-based MOFs,
[
2 3 2 2 3
Fe M(μ -O)(TCA) (H O) ] (NNU-31-M, M = Co, Ni, Zn), which
are expected to display above-mentioned advantages. Within
3+
2+
these structures, high-valent Fe and low-valent M ions are
considered to play the roles of oxidation and reduction active
sites, respectively, while the TCA ligand and heterometallic
cluster itself are used for visible-light absorption. As expected,
The crystalline heterometallic cluster has the potential to
NNU-31-M successfully achieve the CO
2
reduction coupled with
☆
]
H O oxidation without adding additional photosensitizers and
sacrificial agents. Among them, NNU-31-Zn showed the highest
HCOOH yield rate of 26.3 μmol g-1 h-1 and high selectivity
2
[
L.-Z. Dong, L. Zhang, Dr. J. Liu*, Q. Huang, M. Lu and Prof. Y.-Q.
Lan*
Jiangsu Collaborative Innovation Centre of Biomedical Functional
Materials, Jiangsu Key Laboratory of New Power Batteries, School
of Chemistry and Materials Science
Nanjing Normal University
No. 1, Wenyuan Road, Nanjing, 210023 (China)
E-mail: liuj@njnu.edu.cn
yqlan@njnu.edu.cn
Dr. W.-X Ji
(
~100%). The DFT calculation results indicate that the CO
reduction reaction (CO RR) is more likely to occur on Zn, and
the Fe is more susceptible to the H O oxidation reaction.
2
2
2
Significantly, this is the first report of MOF system as
photocatalysts to finish artificial photosynthetic overall reaction,
thus it brings more opportunities for designing crystalline
State Key Laboratory of High-efficiency Coal Utilization and Green
Chemical Engineering
2 2
photocatalysts to reduce CO with H O.
Ningxia University
Yinchuan, 750021 (China)
This article is protected by copyright. All rights reserved.

Angewandte Chemie International Edition
10.1002/anie.201913284
COMMUNICATION
patterns affirmed that NNU-31-M MOFs possess good water
stability (Figure S4). According to both energy dispersive
spectrometer (EDS) (Figure S5, Table S2) and inductively
coupled plasma atomic emission spectroscopy (ICP-AES)
results (Table S3), the stoichiometric ratios of Fe/M in NNU-31-
M are 2:1. The thermogravimetric analysis (TGA) indicated that
NNU-31-M MOFs have high thermal stability (Figure S6). The N
adsorption–desorption isotherms displayed in Figure S7 were
typical type-I isotherm with a sharp N uptake at low relative
pressure, and the corresponding pore-size distributions were
showed in Figure S8. Meanwhile, the CO adsorption isotherms
2
2
2
Sheme 1. Functions of the heterometallic cluster-based organic framework as
photocatalyst
of NNU-31-M were measured at 298 K and under 1 atm and
estimated to be 24.01 (Co), 29.66 (Ni) and 36.97 (Zn) cm3
g
-1
NNU-31-M were synthesized by the TCA ligands and
prefabricated Fe
2
M clusters under solvothermal condition.[11a]
(
Figures S9-S10), respectively.
The NNU-31-Zn is black elongated square bipyramid single
crystal. X-ray single-crystal diffraction indicated that NNU-31-Zn
crystallizes in the orthorhombic system with a Pca2 space
1
group (Table S1). Moreover, the powder X-ray diffraction (PXRD)
patterns of NNU-31-Co and NNU-31-Ni are identical to NNU-31-
Zn, demonstrating that NNU-31-M MOFs are isostructural. There
3
+
2+
are two Fe ions, one M , one μ
O molecules in Fe M cluster (Figure S1). The asymmetric unit
of NNU-31-Zn contains four TCA ligands, four Fe ions, two
Zn2+ ions, two µ -O2− and six H
O molecules (Figure S2). The six
OAc‾ of the cluster were completely replaced by the carboxyl
groups from the TCA, and each TCA ligand links to three Fe
3
-O, six OAc‾ groups and three
H
2
2
3+
3
2
2
M
clusters (Figure S3). By these connection modes, the three-
dimensional (3D) framework and channels of NNU-31-M are
shown as Figure 1a and 1b. In addition, topological analysis by
TOPOS[12] shows NNU-31-Zn is a 3,6-c net topology (Schläfli
2
9
5
3
symbol as {4·6 }{4·6 ·8 }{6 }). The tilling of NNU-31-Zn is shown
in Figure 1c, and its free volume is calculated to be 68.5% by
PLATON[ software.
13]
Figure 2. (a) PXRD patterns of NNU-31-M. (b) UV-Vis-NIR DRS spectra of
NNU-31-M and tauc plot for bandgap calculation of NNU-31-M as inset picture.
(c) UPS spectra of NNU-31-Zn. (d) Band structure for NNU-31-M.
As suggested by the UV-Vis-NIR diffuse reflectance
spectroscopy (UV-Vis-NIR DRS) results, the strong visible light
absorption of NNU-31-Co and NNU-31-Ni only extends to ~570
nm and ~590 nm (Figure 2b). By contrast, NNU-31-Zn shows a
much broader light absorption range (across the entire UV-
visible region) than NNU-31-Co, NNU-31-Ni and free TCA ligand
(
Figure 2b). It also means that electrons of NNU-31-Zn are more
easily excited under visible light irradiation than free TCA, NNU-
1-Co and NNU-31-Ni. The bandgaps (E ) of NNU-31-M are
determined to be 1.85 (Co), 1.82 (Ni), 1.53 (Zn) eV by their tauc
plots (Figure 2b inset)[14]
indicating that they have the
characteristics of the semiconductor. The ionization potential
equivalent to valence band maximum, VBM) of NNU-31-M was
3
g
,
(
determined by ultraviolet photoelectron spectroscopy (UPS),
from which the VBM of NNU-31-Zn was estimated to be -5.71
eV (vs. vacuum level, Ev) by subtracting the excitation energy of
1.22 eV from the width of the He I UPS spectrum (Figure 2c).[
15]
2
Likewise, the VBMs of NNU-31-Co and NNU-31-Ni were
determined to be -5.93 and -5.94 eV (vs. Ev), respectively
(Figures S11-S12). By performing UV-Vis-NIR DRS associated
with UPS, the conduction band minimums (CBMs) of NNU-31-M
MOFs were estimated to be -4.08 (Co), -4.12 (Ni) and -4.18 eV
Figure 1. (a) 3D framework of NNU-31-M constructed by the Fe
TCA. (b) 3D channel simulated diagram of NNU-31-Zn. (c) The tilling of NNU-
1-Zn.
2
M cluster and
3
The PXRD patterns of the synthesized NNU-31-M were in
good agreement with the simulated pattern from single-crystal X-
ray diffraction (Figure 2a), indicating that they have fine
crystallinity and high purity. To evaluate the water stability of
NNU-31-M, 20 mg crystals were immersed into 100 mL water at
room temperature for several days. The consistent PXRD
(
Zn) (vs. Ev), respectively. And the calculated energy-band
alignment results are presented in Figure 2d. To verify the
accuracy of these results, Mott-Schottky electrochemical
measurements were further performed to determine the energy
band positions of the semiconductor-like NNU-31-M MOFs.
This article is protected by copyright. All rights reserved.

Angewandte Chemie International Edition
10.1002/anie.201913284
COMMUNICATION
Since the gap between flat band potential and CBM is negligible
performed to confirm the source of Carbon. As shown in Figure
for n-type semiconductors, the CBM positions of the NNU-31-M
were determined to be -0.75 (Co), -0.74 (Ni) and -0.67 (Zn) V (vs. peak appeared at 166.4 ppm in the 13C NMR spectrum
NHE, pH = 7), respectively (Figures S13-S15). And the VBM
positions of the NNU-31-M were determined to be 1.10 (Co),
3c, when 13CO
2
was employed in the reaction system, a clear
1
3
[10b]
corresponding to H COOH , which strongly indicates that the
12
2 2
produced HCOOH originates from CO . When CO was
1.08 (Ni) and 0.96 (Zn) V (vs. NHE, pH = 7) associated with UV-
employed in the reaction system, the 13C NMR spectrum has no
signal, as shown in Figure S20. At the same time, the production
Vis-NIR DRS (Figures 2c). These results also agree with the
values obtained from UPS. Obviously, the CBMs of NNU-31-M
are more negative than the redox potentials of most
photocatalytic reductive products such as HCOOH, CO, etc.,[16]
while their VBMs are more positive than the redox potential of
of O
effect of air leakage caused by manual injections (Figure 3ꢀd and
Figures S21-22). As expected, the detected HCOOH/O ratio is
2
was detected by the online test, which was to eliminate the
2
close to 2:1. Moreover, we also conducted a series of control
experiments with NNU-31-Zn as an example (Figure S23 and
O
2
/H
2
O (0.82 V vs. NHE, pH = 7 and -5.67 eV vs. Ev)[15]
.
Therefore, theoretically these MOFs may serve as efficient
photocatalysts to performing artificial photosynthetic overall
reaction due to the matched band structures. From the
photoluminescence (PL) spectra of NNU-31-M (Figure S16), the
TCA ligand shows an obvious fluorescence emission spectrum
centered at 440 nm when excited at 340 nm. However, NNU-31-
M shows very weak PL signals near 440 nm close to the
fluorescence quenching, suggesting the electron transfer
between the excited TCA ligand and the cluster unit. To further
investigate the differences on photocatalytic activity of these
potential MOF photocatalysts, the photocurrent response test
was conducted to evaluate photoinduced electron transfer
efficiency. Photocurrent response results showed that the
photocurrent response of NNU-31-Zn is stronger than that of
NNU-31-Co and NNU-31-Ni (Figure S17). Thus, the
photogenerated electron-hole pairs in NNU-31-Zn can be more
efficiently separated by the ligand-metal charge transfer effect.
Table S4) to confirm the photocatalytic CO
31-M. The effects of sacrificial donors and hole scavenger on
the CO reduction and H O oxidation half-reactions of NNU-31-
2
RR activity of NNU-
2
2
Zn were also performed, respectively (Table S5-S6). After
photocatalytic reaction, only HCOOH as liquid reduction product
1
could be detected by IC (Figure S18) and H NMR (Figure S24),
2
and O as oxidation product (except trace gaseous reductive
products) was detected by GC (Figure S21 and S25), indicating
high HCOOH selectivity (~100%) of these MOF-based
2
photocatalysts. The oxygen source of oxidation product (O ) was
also checked by isotopic labelling experiment, in which 18O
2
(m/z=36) and 18O O (m/z=34) were detected by GC-MS after
16
1
8
the reaction using H
2
O as the reaction solvent (Figure S26),
confirming that the generated O
oxidation.
2 2
was derived from the H O
Additionally, this photocatalytic experiment can be recycled
for at least three times (Figure S27), and the solution after
reaction was detected by inductively coupled plasma mass
spectrometry (ICP-MS). It shows that only less than 0.8% of the
catalyst is dissolved (Table S7). PXRD, FTIR and XPS
characterizations after reaction also proved that NNU-31-Zn has
good structural stability (Figure S28-30). As shown in Figure S31,
the SEM images of these MOFs indicated that the morphologies
of the grinded catalysts powders before and after long-term (72
h) photocatalytic reaction are very similar. All the experimental
results indicate that NNU-31-Zn is an effective and selective
2
heterogeneous photocatalyst to integrate CO reduction and
H
2
O oxidation half-reactions. Based on the above experiments
and analysis,
a
possible mechanism for explaining CO
2
reduction and H
2
O oxidation processes is proposed (Figure 4a).
The heterometallic clusters and ligands are excited by visible-
light to generated electron-hole pairs. Then electrons are
transferred to a low-valent metal to undergo CO
2
reduction,
while holes move to high-valent Fe to perform H O oxidation.
2
Density functional theory (DFT) and time-dependent DFT
TDDFT) computational ways were used to explain the
(
Figure 3. (a) The yield of HCOOH produced with NNU-31-M after 24 hours
photoexcitation process and the catalytic reaction mechanism.
The model structures established in the calculation were shown
in Figure S32. Since the photo-absorption efficiency plays a key
role in the photocatalytic process, we first compare the photo-
absorptions of NNU-31-Zn and NNU-31-Ni, which are shown in
Figure 4b. The simulated light absorption of the two systems
agrees well with the experiments, a broad spectrum in the range
of 550 to 650 nm is clearly identified for NNU-31-Zn, while the
NNU-31-Ni shows very poor absorption in the area. The
(catalyst weight of 10 or 20 mg). (b) The amount (blue) and production rate
(
orange) of HCOOH as a function of the time of of visible light irradiation over
13
13
NNU-31-Zn. (c)
atmosphere. (d) The production rates of HCOOH and O
C
NMR spectra for reaction solution from with CO
in NNU-31-Zn.
2
2
The visible-light photocatalytic CO
2
RR was conducted under
pure CO atmosphere in aqueous solution, without the presence
2
of additional photosensitizer and sacrificial agents. As shown in
Figure 3a, NNU-31-Zn shows the highest HCOOH yield of 12.51
μmol under visible light irradiation after 24 h, which is higher
than that of NNU-31-Co (7.17 μmol) and NNU-31-Ni (8.22 μmol). prominent photo-absorption efficiency of Zn-containing MOFs in
The amount of HCOOH is determined by ion chromatography
IC) (Figures S18-19). The HCOOH yield increases almost
linearly with the irradiation time of the NNU-31-Zn catalyst
the visible light range is attributed to the effective charge transfer
from the TCA ligands to the transition metal centers, thus
promoting further photocatalytic reactions. In the following, the
(
1
3
(
Figure 3ꢀb). Furthermore,
CO
2
isotope experiment was
2
catalytic reaction mechanisms of CO RR and water oxidation on
This article is protected by copyright. All rights reserved.

Angewandte Chemie International Edition
10.1002/anie.201913284
COMMUNICATION
NNU-31-Zn are investigated by free energy calculations. The
Science Research of Jiangsu Higher Education Institutions of
China (No. 17KJB150025 and 19KJB150011) and Project
funded by China Postdoctoral Science Foundation (No.
conversion from CO
processes, from *CO
2
to HCOOH requires two hydrogenation
to *OCOH and from *OCOH to *HCOOH,
2
2
018M630572 and 2019M651873); The East-West Cooperation
where the first one serves as rate-determining step (RDS). As
shown in Figure 4c, the energy barrier of the RDS on the Zn site
is slightly preferred over the Fe site, establishing another
advantage of NNU-31-Zn for photocatalyst. As for water
oxidation process, the Fe sites are identified and the dissociation
of *OH into O group (*O) with an energy barrier of 2.06 eV is
proved to be the potential-determining step for the whole four
steps (Figure 4d). The energy barrier of other three steps, the
adsorption of an OH group (*OH) that dissociated from a water
molecule, the formation of an OOH group (*OOH) by the
Project of Ningxia Key R & D Plan (2019BFH02014); Priority
Academic Program Development of Jiangsu Higher Education
Institutions and the Foundation of Jiangsu Collaborative
Innovation Center of Biomedical Functional Materials.
Keywords: heterometallic photocatalyst
• carbon dioxide reduce
reaction • water oxide • metal-organic framework
[
[
1] a) S. J. Davis, K. Caldeira, H. D. Matthews, Science 2010, 329,
330-1333; b) M. Mikkelsen, M. Jørgensen, F. C. Krebs, Energy
1
reaction between *O and anther H
2
O, and the generation of O
2
,
Environ. Sci. 2010, 3, 43-81; c) J. Ran, M. Jaroniec, S.-Z. Qiao,
Adv Mater 2018, 30, 1704649.
are calculated to be, respectively. Therefore, the overpotential of
OER can be obtained by analyzing the reaction free energy of
each elementary step, and the calculated η is 0.83 V.
2] a) X. Liu, S. Inagaki, J. Gong, Angew. Chem. Int. Ed. 2016, 55,
14924-14950; b) A. Vasileff, X. Zhi, C. Xu, L. Ge, Y. Jiao, Y.
Zheng, S.-Z. Qiao, ACS Catal. 2019, 9, 9411-9417; c) J. Ran, J.
Qu, H. Zhang, T. Wen, H. Wang, S. Chen, L. Song, X. Zhang, L.
Jing, R. Zheng, S.-Z. Qiao, Advanced Energy Materials 2019, 9,
1
803402.
3] a) W. Kim, B. A. McClure, E. Edri, H. Frei, Chem. Soc. Rev.
016, 45, 3221-3243; b) M. Lu, J. Liu, Q. Li, M. Zhang, M. Liu,
J.-L. Wang, D.-Q. Yuan, Y.-Q. Lan, Angew. Chem. Int. Ed. 2019,
8, 12392-12397.
[
2
5
[
[
[
4] W. Shi, X. Guo, C. Cui, K. Jiang, Z. Li, L. Qu, J.-C. Wang, Appl.
Catal. B-Environ. 2019, 243, 236-242.
5] J.-C. Wang, L. Zhang, W.-X. Fang, J. Ren, Y.-Y. Li, H.-C. Yao,
J.-S. Wang, Z.-J. Li, ACS Appl. Mater. Inter. 2015, 7, 8631-8639.
6] M. Ding, R. W. Flaig, H.-L. Jiang, O. M. Yaghi, Chem. Soc. Rev.
2019, 48, 2783-2828.
[
[
7] N. A. Vante, H. Tributsch, Nature 1986, 323, 431-432.
8] P. Buchwalter, J. Rosé, P. Braunstein, Chem. Rev. 2015, 115,
2
8-126.
9] a) N. Pinault, D. W. Bruce, Coordin. Chem. Rev. 2003, 241, 1-
5; b) S. Berardi, S. Drouet, L. Francàs, C. Gimbert-Suriñach, M.
Guttentag, C. Richmond, T. Stoll, A. Llobet, Chem. Soc. Rev.
014, 43, 7501-7519.
[
2
2
[
10] a) H.-Q. Xu, J. Hu, D. Wang, Z. Li, Q. Zhang, Y. Luo, S.-H. Yu,
H.-L. Jiang, J. Am. Chem. Soc. 2015, 137, 13440-13443; b) D.
Wang, R. Huang, W. Liu, D. Sun, Z. Li, ACS Catal. 2014, 4,
Figure 4. (a) Schematic of the mechanism of NNU-31-M CO
oxidation. (b) Theoretical simulation light absorption of NNU-31-Zn and NNU-
1-Ni. The free energy profile for the CO RR pathway and (c) OER pathway
d).
2 2
RR with H O
4
254-4260; c) K. M. Choi, D. Kim, B. Rungtaweevoranit, C. A.
Trickett, J. T. D. Barmanbek, A. S. Alshammari, P. Yang, O. M.
Yaghi, J. Am. Chem. Soc. 2017, 139, 356-362; d) Q. Huang, J.
Liu, L. Feng, Q. Wang, W. Guan, L.-Z. Dong, L. Zhang, L.-K.
Yan, Y.-Q. Lan, H.-C. Zhou, Natl. Sci. Rev. 2019; e) N. Li, J. Liu,
J.-J. Liu, L.-Z. Dong, Z.-F. Xin, Y.-L. Teng, Y.-Q. Lan, Angew.
Chem. Int. Ed. 2019, 58, 5226-5231.
3
(
2
2
In summary, a series of stable heterometallic Fe M cluster-
based MOFs are for the first time used as effective
photocatalysts to achieve artificial photosynthetic overall
reaction (coupling CO reduction with H O oxidation) in the
2 2
absence of additional sacrificial agent and photosensitizer.
[11] a) D. Feng, K. Wang, Z. Wei, Y.-P. Chen, C. M. Simon, R. K.
Arvapally, R. L. Martin, M. Bosch, T.-F. Liu, S. Fordham, D.
Yuan, M. A. Omary, M. Haranczyk, B. Smit, H.-C. Zhou, Nat.
Commun. 2014, 5, 5723; b) X.-L. Wang, L.-Z. Dong, M. Qiao,
Y.-J. Tang, J. Liu, Y. Li, S.-L. Li, J.-X. Su, Y.-Q. Lan, Angew.
Chem. Int. Ed. 2018, 57, 9660-9664.
[12]E. V. Alexandrov, V. A. Blatov, A. V. Kochetkov, D. M. Proserpio,
CrystEngComm 2011, 13, 3947-3958.
13] A. Spek, ACTA Crystallogr. D 2009, 65, 148-155.
14] P. Sippel, D. Denysenko, A. Loidl, P. Lunkenheimer, G. Sastre,
D. Volkmer, Adv. Funct. Mater. 2014, 24, 3885-3896.
Among these photocatalysts, NNU-31-Zn shows the highest
efficiency for CO
selectivity of ca. 100%. The corresponding DFT calculation
results indicate that CO RR is more likely to occur on metal Zn,
and H O oxidation reaction occurs on metal Fe. By constructing
2
-to-HCOOH conversion (26.3 μmol g-1 h-1) and
2
[
[
2
these stable crystalline heterometallic cluster-based MOF
photocatalysts for artificial photosynthesis, more direct and clear
evidence on the structure-function relationship of the
photocatalyst is displayed. Significantly, this work can serve as
an important case study for designing crystalline photocatalyst to
realize artificial photosynthetic overall reaction.
[15] J. Liu, Y. Liu, N. Liu, Y. Han, X. Zhang, H. Huang, Y. Lifshitz, S.-
T. Lee, J. Zhong, Z. Kang, Science 2015, 347, 970-974.
[
16] X. Chang, T. Wang, J. Gong, Energy Environ. Sci. 2016, 9,
177-2196.
2
Acknowledgements
This work was financially supported by NSFC (No. 21622104,
21701085, 21871141, 21871142 and 21901122); the NSF of
Jiangsu Province of China (No. BK20171032); the Natural
This article is protected by copyright. All rights reserved.

Angewandte Chemie International Edition
10.1002/anie.201913284
COMMUNICATION
Entry for the Table of Contents (Please choose one layout)
COMMUNICATION
A series of stable heterometallic Fe
cluster-based MOFs achieve the
2
M
L.-Z. Dong, L. Zhang, J. Liu*, Q. Huang,
M. Lu, W.-X. Ji and Y.-Q. Lan*
overall conversion of CO
2
and H
2
O to
the
HCOOH and without
O
2
Page No. – Page No.
assistance of additional sacrificial
agent and photosensitizer. This work
proposes a new strategy for how to
design crystalline photocatalyst to
realize artificial photosynthetic overall
reaction.
Stable Heterometallic Cluster-Based
Organic Frameworks Catalysts for
Artificial Photosynthesis
This article is protected by copyright. All rights reserved.