A highly active and robust iron quinquepyridine complex for photocatalytic CO2reduction in aqueous acetonitrile solution

Article abstract of DOI:10.1039/d0cc01930e

The iron(ii) complex bearing the 2,2′:6′,2′′:6′′,2′′′:6′′′,2′′′′-quinquepyridine (qnpy) ligand, [Fe(qnpy)(H₂O)₂]²⁺, is a highly efficient and robust catalyst for photocatalytic reduction of CO₂to CO in aqueous acetonitrile solution. A turnover number (TON) for CO of up to 14 095 with 98% selectivity can be achieved using Ru(phen)₃Cl₂(phen = 1,10-phenanthroline) as the photosensitizer and BIH (1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole) as the sacrificial reductant in a CO₂-saturated MeCN/H₂O (1 : 1, v/v) solution under visible light irradiation. This Fe complex is state-of-the-art for CO₂visible-light-driven catalysis.

Full text of DOI:10.1039/d0cc01930e

View Article Online
View Journal
ChemComm
Chemical Communications
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: Y. Qin, L. Chen, G.
Chen, Z. Guo, L. Wang, H. Fan, M. Robert and T. Lau, Chem. Commun., 2020, DOI:
10.1039/D0CC01930E.
Volume 54
This is an Accepted Manuscript, which has been through the
Number
January 2018
Pages 1-112
1
4
Royal Society of Chemistry peer review process and has been
accepted for publication.
ChemComm
Chemical Communications
rsc.li/chemcomm
Accepted Manuscripts are published online shortly after acceptance,
before technical editing, formatting and proof reading. Using this free
service, authors can make their results available to the community, in
citable form, before we publish the edited article. We will replace this
Accepted Manuscript with the edited and formatted Advance Article as
soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes to the
text and/or graphics, which may alter content. The journal’s standard
Terms & Conditions and the Ethical guidelines still apply. In no event
shall the Royal Society of Chemistry be held responsible for any errors
or omissions in this Accepted Manuscript or any consequences arising
from the use of any information it contains.
ISSN 1359-7345
COMMUNICATION
S. J. Connon, M. O. Senge et al.
Conformational control of nonplanar free base porphyrins:
towards bifunctional catalysts of tunable basicity
rsc.li/chemcomm

Please do not adjust margins
Page 1 of 5
ChemComm
View Article Online
DOI: 10.1039/D0CC01930E
Journal Name
COMMUNICATION
Highly active and robust iron quinquepyridine complex for
photocatalytic CO2 reduction in aqueous acetonitrile solution
Received 00th January 20xx,
Accepted 00th January 20xx
Yanfei Qin,‡[a, b] Lingjing Chen,‡[b] Gui Chen,*[b] Zhenguo Guo,[c] Lei Wang,[a] Hongbo Fan,[b] Marc
Robert*[d,e] and Tai-Chu Lau*[c]
DOI: 10.1039/x0xx00000x
www.rsc.org/.
aqueous solution is highly desirable, as water is abundant and non-
toxic. Moreover, the coupling of CO2 reduction with water
oxidation, which can produce protons and electrons for the reduction
of CO2, requires that the CO2 reduction system is water compatible.
However, due to stability and solubility problems, as well as
competitive hydrogen evolution, the design of highly efficient and
selective molecular catalysts for CO2 reduction in aqueous solution
The iron(II) complex bearing the 2,2':6',2'':6'',2''':6''',2''''-
quinquepyridine (qnpy) ligand, [Fe(qnpy)(H2O)2]2+, is a highly
efficient and robust catalyst for photocatalytic reduction of CO2 to
CO in aqueous acetonitrile. A turnover number (TON) for CO of up
to 14095 with 98% selectivity can be achieved using Ru(phen)3Cl2
(phen = 1,10-phenanthroline) as photosensitizer and BIH (1,3-
dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole)
as
34-38
is still a challenge.5 So far only a few Fe,32 Co33 and Ni29,
sacrificial reductant in a CO2-saturated MeCN/H2O (1:1, v/v)
solution under visible light irradiation. This Fe complex is state-of-
the art for CO2 visible-light-driven catalysis.
molecular CO2 reduction catalysts have been demonstrated to be
compatible with aqueous medium, but the efficiencies of these
catalysts are generally low.
We have recently reported that iron(II), cobalt(II) and copper(II)
complexes bearing the 2,2′:6′,2″:6″,2′′′-quaterpyridine (qpy) ligand,
[M(qpy)(H2O)2]2+, are highly efficient and selective catalysts for the
photocatalytic reduction of CO2.15, 16, 30, 39, 40 Our results demonstrate
that qpy, being a tetradentate and good π-acceptor ligand, is able to
stabilize low-valent metal active intermediates for CO2 reduction. In
this work, we have investigated photocatalytic CO2 reduction by an
iron(II) complex bearing the 2,2':6',2'':6'',2''':6''',2''''-quinquepyridine
(qnpy) ligand, [FeII(qnpy)(H2O)2]2+ (1); this complex was reported
by Che as an anti-tumor agent.41 1 should be a more robust catalyst
than [Fe(qpy)(H2O)2]2+, since qnpy is a pentadentate ligand while
qpy is a quadridentate ligand. Hence, we anticipate that 1 would be
more stable with respect to ligand dissociation, especially in aqueous
solution. Indeed, we found that 1 is a highly stable and active
catalyst for visible-light induced CO2-to-CO conversion even in 50%
aqueous acetonitrile solution, with TON of up to 14095 and
selectivity of 98%, using Ru(phen)3Cl2 as photosensitizer and BIH
as electron donor (Scheme 1).
The continuous increase of carbon dioxide amount in the biosphere
caused by the burning of fossil fuels has led to serious global
environmental problems. Fossil fuels are also non-renewable energy
sources that will be eventually used up.1, 2 Hence, the use of solar
energy to drive the conversion of CO2 to high value-added chemicals
or liquid fuels is one of the most promising ways to effectively
contribute solving the current global environmental and energy
problems.3-6 In the past few years, a variety of molecular catalysts
based on inexpensive metals such as Mn,7-10 Fe,11-17 Co,16, 18-24 Ni,25-
29
and Cu30, 31 have been studied for the photocatalytic reduction of
CO2 to products such as CO, HCO2H and in rare case CH4. Most of
the photocatalytic CO2 reduction reactions were carried out in pure
organic solvents, such as acetonitrile or N,N-dimethylformamide
(DMF). To be environmentally friendly, reduction of CO2 in
a Shenzhen Key Laboratory of Polymer Science and Technology College of Materials
Science and Engineering, Shenzhen University Xueyuan Avenue 1066, Nanshan,
Shenzhen, 518055, China.
2+
b
H2O
School of Environment and Civil Engineering, Dongguan Cleaner Production
N
N
N
H
N
N
Technology Center, Dongguan University of Technology, Guangdong 523808, P. R.
China.
N
N
N
N
Ru
Fe
N
N
N
N
Email: chengui@dgut.edu.cn
H2O
c Department of Chemistry, City University of Hong Kong, Tat Chee Avenue, Hong
[Fe(qnpy)(H2O)2]2+
Kong, China.
2+
Ru(phen)3
BIH
Email: bhtclau@cityu.edu.hk
Université de Paris, Laboratoire d’Electrochimie Moléculaire, CNRS, F-75013
Scheme 1 Structures of catalyst 1 ([Fe(qnpy)(H2O)2]2+), photosensitizer
d
(Ru(phen)32+) and sacrificial reductant (BIH).
Paris, France.
e Institut Universitaire de France (IUF), F-75005 Paris, France.
Email: robert@u-paris.fr
‡ Both authors contributed equally
The cyclic voltammetry of 1 in CH3CN under Ar shows a
reversible wave at -1.56 V vs. Fc+/Fc, which is assigned to the
FeII/FeI couple (Fig. 1a). When the CV was carried out in CO2-
†Electronic Supplementary Information (ESI) available: details of experiments,
additional tables and figures. See DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 2 of 5
COMMUNICATION
Journal Name
saturated CH3CN, the FeII/FeI reduction wave is enhanced and there distorted structure,42 hence ligand dissociation probably occurs
View Article Online
2+
is a large catalytic current appearing at -2.18 V vs. Fc+/Fc, consistent readily in water. Hence, although [Fe(dqtpy)(H2O)2] shows good
DOI: 10.1039/D0CC01930E
with catalytic reduction of CO2. Photocatalytic CO2 reduction by 1 photocatalytic activity using an organic photosensitizer in the
was initially investigated using Ru(phen)32+ as photosensitizer, BIH absence of water, it is virtually inactive under the present conditions.
as sacrificial reductant and triethanolamine (TEOA) as proton The catalyst [Fe(phen)3]2+ recently reported by Fu with an
acceptor.16 In a typical experiment, a CO2-saturated MeCN/TEOA unexpected TON of 33167 (albeit using only 0.15 μM of catalyst,
2+
(4:1, v/v) solution containing 1 (0.05 mM), Ru(phen)3 (0.2 mM) which makes the performance artificially high with only a small
and BIH (0.11 M) was irradiated by visible light (LED, centred at absolute quantity of product formed),43 also shows poor catalytic
460 nm) for 68 h, resulting in the production of CO and H2 with activity in the presence of water. These results demonstrate the
TON of 208 and 14, respectively. Trace amount of formate was also superior performance of 1 among various iron catalysts.
detected. We then attempted to use water as base to replace TEOA,
250
200
150
100
50
2500
2000
1500
1000
500
250
200
150
100
50
(a)
CO
H2
(b) 0.05 mM 1
and it was found that the photocatalytic efficiency was greatly
enhanced (Fig. 1b). The beneficial effect of water was also
demonstrated by CV, which shows enhancement of catalytic current
for CO2 reduction upon adding water (Fig. 1a). When photocatalysis
was carried out in the presence of 20% of H2O, the TON for CO was
found to be 1751. Small amounts of H2 and formate were also
detected, with TON of 32 and 18, respectively (Table S1, ESI†). The
amount of product was found to increase with increasing water
content, reaching a maximum TON of 2190 for CO when the water
content was 50%, H2 was produced with TON of 27, but only a trace
amount of formate was detected, hence the selectivity for CO
production is 99% (Fig. 1b). When the concentration of 1 was
decreased from 0.05 mM to 0.005 mM, the TON for CO became
14095, with 98% selectivity (Fig. 2 and entry 1 and 2 in Table 1).
Such TON and selectivity values are among the highest for
photocatalytic CO2 reduction in solvents with high water content
(Table S2, ESI†). However, further increasing the water content
resulted in decrease in TON, and the catalytic activity stopped when
the water content reached 80%. This is mainly due to the insolubility
of BIH in water.
CO
H2
0
0
0
0
20
40
60
80
0.01
0.05
0
0.0025
0.005
Irradiation time (h)
Concentration of catalyst 1 (mM)
Fig. 2 (a) Concentration dependence of 1 on CO (blue) and H2 (red) production. (b)
Photocatalytic activity of 1 as a function of time for CO (blue) and H2 (red)
production. Conditions: 0 to 0.05 mM 1, 0.2 mM Ru(phen)3 and 0.11 M BIH
upon visible light irradiation of a CO2-saturated MeCN/H2O (1:1, v/v) solution (2
mL) at 293 K.
2+
120
90
60
30
0
2500
2000
1500
1000
500
(a)
(b)
Fig. 3 TON (blue) and selectivity (brown) for photocatalytic CO2-to-CO conversion
0.5 mM catalyst 1 + 0.5 M H2O under CO2
0.5 mM catalyst 1 under CO2
by various iron catalysts in aqueous CH3CN. Conditions: 0.05 mM catalyst, 0.2
0.5 mM catalyst 1 under Ar
2+
CO
H2
mM Ru(phen)3 and 0.11 M BIH in CO2-saturated MeCN/H2O (1:1, v/v) solution
(2 mL) at 293 K upon visible light irradiation.
Formate
0
-0.4
-0.8
-1.2
-1.6
-2.0
-2.4
10 20 30 40 50 60 70 80
H2O (%, v/v)
Potential vs. Fc+/Fc in MeCN (V)
Fig. 1 (a) Cyclic voltammograms of 0.5 mM 1 in 0.1 M nBu4NPF6 in MeCN
under Ar and CO2 atmosphere (1 atm), and in the presence of 0.5 M H2O.
(b) Effects of H2O content on photocatalytic reduction of CO2. Conditions:
2+
0.05 mM 1 , 0.2 mM Ru(phen)3 and 0.11 M BIH in 2 mL CO2-saturated
MeCN solution under visible-light irradiation (blue LED centered at 460 nm)
for 68 h at 293 K. Turnover number (TON) = mol number of product/mol
number of catalyst.
As a comparison, the photocatalytic activity of various iron
complexes bearing other polypyridyl ligands towards CO2 reduction
in 50% aqueous CH3CN were also investigated in the same
conditions, for comparison to be meaningful. As shown in Fig. 3 and
Table 1, the efficiency of the catalysts follows the order of 1 >
[Fe(qpy)(H2O)2]2+ > [Fe(tpy)2]2+ > [Fe(bpy)2Cl2]+ > [Fe(phen)3]2+
>
[Fe(dqtpy)(H2O)2]2+ (seen Scheme S1 for structures, ESI†), with
TON of 2190, 1689, 615, 245, 88 and 13, respectively (see entry 1, 3
to 7 in Table 1). This can be attributed to the increasing chelating
ability of the ligands on going from the bidentate phen and bpy to
the pentadentate qnpy ligand, which would result in increased
stability of the complexes, especially in aqueous solutions. Although
dqtpy is also a pentadentate ligand, [Fe(dqtpy)(H2O)2]2+ has a rather
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 5
ChemComm
Please do not adjust margins
Journal Name
COMMUNICATION
Table 1 Visible-light-driven catalytic reduction of CO2 by iron complexes.
the yield of CO (Fig. S7, ESI†). However, inVicerweAarstiicnlegOntlihnee
DOI: 10.1039/D0CC01930E
concentration of Ru(phen)3 from 0.05 mM to 0.5 mM had little
2+
TON (Selectivity %)
Product (μmol)
Entry
Catalyst
effect on the yield of the products, which is significantly different
from some reported catalysts with high TON of CO, such as
[Fe(phen)2]2+, [Cu(qpy)]2+ and [Cu(pyN2Me2)(HCO2)]-.30,31,43 Even
when the ratio of 1 to [Ru(phen)3]2+ (0.05 mM each) was 1:1, 213
μmol CO and 2.6 μmol H2 were detected, giving an impressive TON
of 2130 and a selectivity of 99%.
The quantum yield Φ for CO production by the photocatalytic
system in 50% aqueous CH3CN was determined to be 0.8% by
ferrioxalate actinometry, after irradiation for 24 h at 460 nm (see
ESI† for details). ΦCO was increased to 2.3% by reducing the water
content from 50% to 30%, this value being comparable with reported
homogeneous earth-abundant metal catalysts.
CO
2190(99)
14095(98)
13(72)
1689(98)
615(85)
245(72)
88(73)
13(68)
0(0)
H2
CO
219.0
141.0
1.3
H2
2.7
3.6
0.5
3.8
10.8
9.3
3.3
0.6
0
1
2a
3
1
27(1)
360(2)
5(28)
38(2)
108(15)
93(28)
33(27)
6(32)
0(0)
1
[Fe(dqtpy)(H2O)2]2+
[Fe(qpy)(H2O)2]2+
[Fe(tpy)2]2+
[Fe(bpy)2Cl2]+
4
168.9
61.5
24.5
8.8
5
6
7
[Fe(phen)3]2+
8b
9c
10d
11e
12
13f
14g
none
1.3
1
0
1
0(0)
0(0)
0
0
1
0(0)
6(100)
3(11)
15(15)
171(4)
0
0.6
0.3
0.15
17.1
Luminescence quenching experiments of the excited state of
Ru(phen)32+ were investigated to obtain insights into the mechanism.
The bimolecular quenching rate constant of Ru(phen)32+ by BIH and
1, obtained from Stern-Volmer plots, are equal to 5.5 × 109 and 1.7
Fe(ClO4)2
Fe(ClO4)2
1
16(89)
82(85)
4481 (96)
1.6
0.82
448.1
2+
Reaction conditions: 0.05 mM catalyst, 0.2 mM Ru(phen)3 and 0.11 M BIH in
× 108 M− 1·s− 1, respectively (Fig. 4a and Fig. S5 in ESI†). These
CO2-saturated MeCN/H2O (1:1, v/v) solution, irradiation for 68 h. a 0.005 mM 1; b
2+*
2+
f
Without catalyst; c Without Ru(phen)3
;
d Without BIH; e Under Ar atmosphere;
values indicate that the excited photosensitizer Ru(phen)3
is
0.005 mM Fe(ClO4)2 as catalyst. g Second batch of BIH and Ru(phen)32+ was added,
irradiation for 130 h. The errors are around 10%. dqtpy =6,6''-di(quinolin-8-yl)-
2,2':6',2''-terpyridine, tpy =2,2’:6’,2”-terpyridine, bpy = 2,2'-bipyridine, phen =
1,10-phenanthroline.
reductively quenched by BIH, due to its higher quenching rate and
concentration than 1. The fluorescence lifetime of Ru(phen)3 is
somewhat dependent on the water content; in the absence of water,
the lifetime was found to be 546 ns and it gradually increased with
the addition of water, reaching 680 ns at 70% water content (Fig.
4b).
2+*
Control experiments showed that all components are required for
photocatalytic CO2-to-CO conversion. In the absence of 1, only a
small amount of CO (TON = 13) and H2 (TON = 6) were recorded
(entry 8 in Table 1). Without photosensitizer or BIH, no CO or H2
was produced (entries 9 and 10 in Table 1). If CO2 was replaced by
argon, only a trace amount of H2 was detected (entry 11 in Table 1).
Using 0.05 mM or 0.005 mM Fe(ClO4)2 as catalyst, the yield of CO
is less than one percent of that by 1 (entry 12 and 13 in Table 1).
13C-labeling experiments under a 13CO2 atmosphere produced 13CO
(Fig. S1, ESI†). All these results indicate that CO is derived from
CO2 by catalyst 1 in the photocatalytic system.
700
650
600
550
500
3.0
2.5
2.0
1.5
1.0
50 % H2O
lifetime
y = 3.401x + 1
R2 = 0.9994
Kq = 5.5 X 109 M-1s-1
·

0%
20%
H2O (%, v/v)
40%
60%
80%
0.0 0.1 0.2 0.3 0.4 0.5 0.6
[BIH] (mM)
Fig. 4 (a) Stern-Volmer plot for luminescence lifetime quenching of excited
Ru(phen)32+ (0.05 mM) by BIH in MeCN/H2O (1:1 v/v) solution. (b) Effect of water
Molecular catalysts may decompose during catalysis to generate
metal nanoparticles as the real catalysts.44, 45 In order to explore this content on luminescence lifetime of excited Ru(phen)32+ in MeCN.
possibility we have conducted dynamic light scattering (DLS) and
mercury poisoning tests. No particles in the solution were detected
by DLS even after photoirradiation for 68 h (Fig. S2, ESI†).
Experiments conducted in the presence of Hg (0.2 mL) led only to a
slight decrease of TON from 2190 to 1918 (Fig. S3, ESI†), this
suggests that the active catalyst is not Fe nanoparticles, which would
be deactivated by forming an amalgam with Hg. These results
indicate that 1 is predominantly a homogeneous molecular catalyst.
The lack of catalysis by Fe(ClO4)2 further supports the notion that
catalytic activity does not arise from the demetalation of the iron
catalyst.
Based on our results as well as our previous studies on catalytic
CO2 reduction by [Fe(qpy)(H2O)2]2+.16, 39 a proposed mechanism for
photocatalytic CO2-to-CO conversion by 1 is shown in Scheme 2.
Upon visible light irradiation, excitation of Ru(phen)32+ followed by
+
reductively quenching by BIH produces Ru(phen)3 . It then
undergoes one electron transfer to 1 to give 1-, this process is
+
thermodynamically feasible; (Ru(phen)32+/Ru(phen)3 , E0 = -1.78 V
vs. Fc+/Fc;46 1/1-, E0 = -1.56V vs. Fc+/Fc (see Fig. 1a). Binding of
•−
CO2 to the active species 1- generates the 1-CO2 intermediate. In
•−
As shown in Fig. 2, CO2 evolution stops after 68 h of irradiation.
the presence of protons, 1-CO2 undergoes further two-electrons
2+
+
Addition of a second batch of 1 or Ru(phen)3 failed to reactivate
reduction by Ru(phen)3 , leading to C−O bond cleavage to generate
1--CO. Release of CO regenerates the active species 1-, this process
the catalytic system (Fig. S4, ESI†). However, 88% or 100% of the
catalytic activity was reinstated by adding a second batch of BIH or
BIH and Ru(phen)32+, respectively, leading to a total TON of 4481
for CO (96% selectivity) in 130 h irradiation (Table 1, entry 14).
These results indicate that the factors that cause the deactivation of
being probably assisted by visible light irradiation.39
the photocatalytic system are the complete consumption of BIH and
2+
the partial decomposition of Ru(phen)3
, while 1 remains stable
throughout the catalysis. Investigation of the concentration
dependence of BIH (0 to 0.11 M) shows a linear relationship with
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 4 of 5
COMMUNICATION
Journal Name
O
O
12. H. Takeda, K. Ohashi, A. Sekine and O. Ishitani, J. Am. Chem. Soc.,
C
View Article Online
[FeII(qnpy)]+
CO2
2016, 138, 4354-4357.
+
H+
DOI: 10.1039/D0CC01930E
2Ru(phen)3
1
13. A. Rosas-Hernandez, C. Steinlechner, H. Junge and M. Beller, Green
Chem., 2017, 19, 2356-2360.
CO2
H+
BI+
+
14. H. Rao, L. C. Schmidt, J. Bonin and M. Robert, Nature, 2017, 548, 74-
77.
15. C. Cometto, R. Kuriki, L. Chen, K. Maeda, T. C. Lau, O. Ishitani and M.
Robert, J. Am. Chem. Soc., 2018, 140, 7437-7440.
e-
[FeI(qnpy)]+
1-
[FeII(qnpy)]2+
1
2e-
16. Z. Guo, S. Cheng, C. Cometto, E. Anxolabéhère-Mallart, S.-M. Ng, C.-
C. Ko, G. Liu, L. Chen, M. Robert and T.-C. Lau, J. Am. Chem. Soc.,
2016, 138, 9413-9416.
17. H. Rao, J. Bonin and M. Robert, Chem. Commun., 2017, 53, 2830-2833.
18. D. Behar, T. Dhanasekaran, P. Neta, C. M. Hosten, D. Ejeh, P.
Hambright and E. Fujita, J. Phys. Chem. A, 1998, 102, 2870-2877.
19. S. L.-F. Chan, T. L. Lam, C. Yang, S.-C. Yan and N. M. Cheng, Chem.
Commun., 2015, 51, 7799-7801.
h

BIH
CO
CO
h

[FeI(qnpy)]+
1- CO
2+
2Ru(phen)3
OH
Scheme 2 Proposed mechanism for the photocatalytic CO2 reduction with 1.
In conclusion, [FeII(qnpy)(H2O)2]2+ is a highly efficient, selective
and robust catalyst for the photocatalytic CO2-to-CO conversion in
aqueous MeCN using Ru(phen)3 as photosensitizer and BIH as
20. L. Chen, Z. Guo, X.-G. Wei, C. Gallenkamp, J. Bonin, E. Anxolabéhère-
Mallart, K.-C. Lau, T.-C. Lau and M. Robert, J. Am. Chem. Soc., 2015,
137, 10918-10921.
2+
sacrificial donor. The addition of water results in significant
enhancement of the yield of CO; 1 is highly active even in the
presence of 50% of water, with an impressive TON of up to 14095
and a high selectivity of 98% for CO. 1 remains stable throughout
the catalysis. The decrease in catalytic activity at higher water
content is due to the insolubility of BIH in water. Our results
indicate that 1 is potentially suitable for the construction of
practical catalytic system for artificial photosynthesis. Further
electrocatalytic CO2 reduction in water by 1 as well as DFT
calculations are in progress.
21. G. Zhao, H. Pang, G. Liu, P. Li, H. Liu, H. Zhang, L. Shi and J. Ye,
Appl. Catal. B: Environ., 2017, 200, 141-149.
22. J.-W. Wang, H.-H. Huang, J.-K. Sun, T. Ouyang, D.-C. Zhong and T.-B.
Lu, ChemSusChem, 2018, 11, 1025-1031.
23. T. Ouyang, H. J. Wang, H. H. Huang, J. W. Wang, S. Guo, W. J. Liu, D.
C. Zhong and T. B. Lu, Angew. Chem. Int. Ed., 2018, 57, 16480-16485.
24. Q.-Q. Bi, J.-W. Wang, J.-X. Lv, J. Wang, W. Zhang and T.-B. Lu, ACS
Catal., 2018, 8, 11815-11821.
25. A. H. A. Tinnemans, T. P. M. Koster, D. H. M. W. Thewissen and A.
Mackor, Recl. Trav. Chim. Pays-Bas, 1984, 103, 288-295.
26. V. S. Thoi, N. Kornienko, C. G. Margarit, P. Yang and C. J. Chang, J.
Am. Chem. Soc., 2013, 135, 14413-14424.
27. D. Hong, Y. Tsukakoshi, H. Kotani, T. Ishizuka and T. Kojima, J. Am.
Chem. Soc., 2017, 139, 6538-6541.
28. M. F. Kuehnel, C. D. Sahm, G. Neri, J. R. Lee, Katherine L. Orchard, A.
J. Cowan and E. Reisner, Chem. Sci., 2018, 9, 2501-2509.
29. M. F. Kuehnel, K. L. Orchard, K. E. Dalle and E. Reisner, J. Am. Chem.
Soc., 2017, 139, 7217-7223.
30. Z. Guo, F. Yu, Y. Yang, C.-F. Leung, S.-M. Ng, C.-C. Ko, C. Cometto,
T.-C. Lau and M. Robert, ChemSusChem, 2017, 10, 4009-4013.
31. W.-J. Liu, H.-H. Huang, T. Ouyang, L. Jiang, D.-C. Zhong, W. Zhang
and T.-B. Lu, Chem. Eur. J., 2018, 24, 4503-4508.
The work described in this project was supported by the National
Natural Science Foundation of China (21975043, 21703034),
NSFC/RGC joint research scheme (N_CityU115/18) and
Guangdong Provincial Key Platforms and Major Scientific Research
Projects for Colleges and Universities (2018KTSCX227). Partial
financial support from Institut Universitaire de France (IUF) is also
gratefully acknowledged.
32. H. Rao, J. Bonin and M. Robert, ChemSusChem, 2017, 10, 4447-4450.
33. X. Zhang, M. Cibian, A. Call, K. Yamauchi and K. Sakai, ACS Catal.,
2019, 9, 11263-11273.
34. M. A. Méndez, P. Voyame and H. H. Girault, Angew. Chem. Int. Ed.,
2011, 50, 7391-7394.
35. G. Neri, M. Forster, J. J. Walsh, C. M. Robertson, T. J. Whittles, P.
Farràs and A. J. Cowan, Chem. Commun., 2016, 52, 14200-14203.
36. K. Mochizuki, S. Manaka, I. Takeda and T. Kondo, Inorg. Chem., 1996,
35, 5132-5136.
37. C. A. Craig, L. O. Spreer, J. W. Otvos and M. Calvin, J. Phys. Chem.,
1990, 94, 7957-7960.
38. J. L. Grant, K. Goswami, L. O. Spreer, J. W. Otvos and M. Calvin, J.
Chem. Soc., Dalton Trans., 1987, 2105-2109.
39. C. Cometto, L. Chen, P.-K. Lo, Z. Guo, K.-C. Lau, E. Anxolabéhère-
Mallart, C. Fave, T.-C. Lau and M. Robert, ACS Catal., 2018, 8, 3411-
3417.
40. Z. Guo, G. Chen, C. Cometto, B. Ma, H. Zhao, T. Groizard, L. Chen, H.
Fan, W.-L. Man, S.-M. Yiu, K.-C. Lau, T.-C. Lau and M. Robert, Nature
Catalysis, 2019, 2, 801-808.
41. E. L.-M. Wong, G.-S. Fang, C.-M. Che and N. Zhu, Chem. Commun.,
2005, 4578-4580.
Conflicts of interest
There are no conflicts to declare.
Notes and references
1. E. S. Sanz-Pérez, C. R. Murdock, S. A. Didas and C. W. Jones, Chem.
Rev., 2016, 116, 11840-11876.
2. Q. Schiermeier, Nature, 2011, 470, 316-316.
3. H. Takeda, C. Cometto, O. Ishitani and M. Robert, ACS Catal., 2017, 7,
70-88.
4. K. A. Grice, Coord. Chem. Rev., 2017, 336, 78-95.
5. J. Bonin, A. Maurin and M. Robert, Coord. Chem. Rev., 2017, 334, 184-
198.
6. K. E. Dalle, J. Warnan, J. J. Leung, B. Reuillard, I. S. Karmel and E.
Reisner, Chem. Rev., 2019, 119, 2752-2875.
7. H. Takeda, H. Koizumi, K. Okamoto and O. Ishitani, Chem. Commun.,
2014, 50, 1491-1493.
8. H. Fei, M. D. Sampson, Y. Lee, C. P. Kubiak and S. M. Cohen, Inorg.
Chem., 2015, 54, 6821-6828.
9. P. L. Cheung, C. W. Machan, A. Y. S. Malkhasian, J. Agarwal and C. P.
Kubiak, Inorg. Chem., 2016, 55, 3192-3198.
10. H. Takeda, H. Kamiyama, K. Okamoto, M. Irimajiri, T. Mizutani, K.
Koike, A. Sekine and O. Ishitani, J. Am. Chem. Soc., 2018, 140, 17241-
17254.
42. L. Chen, Y. Qin, G. Chen, M. Li, L. Cai, Y. Qiu, H. Fan, M. Robert and
T. C. Lau, Dalton Trans., 2019, 48, 9596-9602.
43. Z.-C. Fu, C. Mi, Y. Sun, Z. Yang, Q.-Q. Xu and W.-F. Fu, Molecules,
2019, 24, 1878.
44. C. Cometto, L. Chen, D. Mendoza, B. Lassalle-Kaiser, T. C. Lau and M.
Robert, ChemSusChem, 2019, 12, 4500-4505.
45. S. Fukuzumi, J. Jung, Y. Yamada, T. Kojima and W. Nam, Chem. Asian
J., 2016, 11, 1138-1150.
46. T. Ouyang, H.-H. Huang, J.-W. Wang, D.-C. Zhong and T.-B. Lu,
Angew. Chem. Int. Ed., 2017, 56, 738-743.
11. J. Bonin, M. Robert and M. Routier, J. Am. Chem. Soc., 2014, 136,
16768-16771.
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 5
ChemComm
View Article Online
DOI: 10.1039/D0CC01930E
Table of Content Graphic
Highly active and robust iron quinquepyridine complex for
photocatalytic CO2 reduction in aqueous acetonitrile solution
Yanfei Qin,‡[a, b] Lingjing Chen,‡[b] Gui Chen,*[b] Zhenguo Guo,[c] Lei Wang,[a] Hongbo Fan,[b] Marc Robert*[d,e] and Tai-
Chu Lau*[c]
[Fe(qnpy)(OH2)2]2+ is a highly efficient and robust catalyst for photocatalytic reduction of CO2 to
CO, with a TON for CO of up to 14095 and selectivity of 98% using Ru(phen)3Cl2 as
photosensitizer and BIH as sacrificial reductant in MeCN/H2O (1:1, v/v) under visible light
irradiation.