Hydrogenation of CO2 to Formate with H2: Transition Metal Free Catalyst Based on a Lewis Pair

Article abstract of DOI:10.1002/anie.201809634

Hydrogenation of CO₂ to formate with H₂ in the absence of transition metal is a long-standing challenge in catalysis. The reactions between tris(pentafluorophenyl)borane (BCF) and K₂CO₃ (or KHCO₃) are found to form a Lewis pair (K₂[(BCF)₂?CO₃]) which can react with both H₂ and CO₂ to produce formate. Based on these stoichiometric reactions, the first catalytic hydrogenation process of CO₂ to formate using transition metal free catalyst (BCF/M₂CO₃, M=Na, K, and Cs) is reported. The highest TON value of this catalytic process is up to 3941. Further research revealed the reaction mechanism in which the Lewis pair enables the splitting of H₂ and the insertion of CO₂ into the B?H bond.

Full text of DOI:10.1002/anie.201809634

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Accepted Article
Title: Hydrogenation of CO2 to Formate with H2 Catalyzed by
Transition Metal Free Catalyst Based on Lewis Pair
Authors: Xingbang Hu, Tianxiang Zhao, Youting Wu, and Zhibing
Zhang
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201809634
Angew. Chem. 10.1002/ange.201809634
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10.1002/anie.201809634
Angewandte Chemie International Edition
COMMUNICATION
Hydrogenation of CO2 to Formate with H2: Transition Metal Free
Catalyst Based on a Lewis Pair
Tianxiang Zhao, Xingbang Hu*, Youting Wu* and Zhibing Zhang
Abstract: Hydrogenation of CO2 to formate with H2 in the absence for the purpose of hydrogenation of CO2 with H2 in the presence
of transition metal is a long-standing great challenge in catalysis. of FLPs, only stoichiometric reactions were achieved.[19] For
The reactions between tris(pentafluorophenyl)borane (BCF) and examples, the stoichiometric hydrogenation of CO2 was
K2CO3 (or KHCO3) are found to form a Lewis pair (K2[(BCF)2-CO3])
observed after 6 days at 160 oC in the presence of BCF/TMP
that can react with both H2 and CO2 to produce formate. Based on (TMP=2,2,6,6-tetramethylpiperidine).[19a] Theoretical calculation
these stoichiometric reactions, the first catalytic hydrogenation revealed that the BCF/TMP system showed good reactivity for
process of CO2 to formate using transition metal free catalyst H2 split, but the barrier of CO2 activation was too high (163.7
(BCF/M2CO3, M=Na, K, and Cs) is reported. The highest TON value kJ/mol).[20] In the presence of intramolecular B/N FLP, up to 1.2
of this catalytic process is up to 3941. Further researches revealed equivalents of the hydrogenation products of CO2 can be
o
the reaction mechanism that the Lewis pair enables the splitting of obtained after 9 days at 80 C.[19b] In addition to the high barrier
[20]
H2 and the insertion of CO2 into the B-H bond.
of the reaction,
previous research also found that the
unstability of the reported FLP may hinder the hydrogenation of
CO2 in the catalytic processes. [19a]
Carbon dioxide (CO2), as a primary greenhouse gas, has
attracted world wide focus. On the other hand, CO2 is also a
prospective C1 resource being used in the synthesis of many
important chemicals, such as formic acid, methanol, urea,
carbonates, and so on.[1] Among them, the hydrogenation of CO2
to formic acid or formate is particularly attractive, owing to that
most of the formic acid in industry are produced by the
hydrolysis of methyl formate or formamide.[1c] In addition, the
hydrogenation of CO2 to formic acid is also thought as a
valuable method for H2 storage.[2]
The hydrogenation of CO2 requires the activation of both H2
and CO2 at the same time. It makes this reaction full of
challenges because both H2 and CO2 are extremely stable.[3]
Some noble metal based compounds are reported to be
effective catalysts for the hydrogenation of CO2, such as Ru,[4]
Rh,[5] Ir,[6] Pd,[7] Pt,[8] Re,[9] and Au [10]. The formation of metal
hydride (M-H) through the interaction between the noble metal
and H2 is vital for these catalytic processes, so that, CO2 can be
inserted into the M-H bond.[4-10] In contrast, the use of abundant
and inexpensive first-row transition metals has been seldom
reported. There are only several examples of using Fe,[11] Co,[12]
Ni,[13] Cu,[14] and Mn[15] based catalysts and the catalytic
activities of these non noble metal compounds are far lower than
those of the noble metals.
The activation of H2 by transition metal free catalysts is quite
attractive in both industry and academia.[16a] Interestingly, the
frustrated Lewis pairs (FLPs)[16] has been proved to be a
powerful new concept in small molecule activation,[17] especially
for H2.[18] Usually, sterical inhibition is vital for a system to be
FLP, since it can prevent from the formation of classical Lewis
acid-base adducts.[16-18] Though many efforts have been made
Figure 1. (a) Reactions to produce K2[(BCF)2-CO3]. BCF=B(C6F5)3; (b) X-ray
structure of K2[(BCF)2-CO3]. C: gray. O: red. B: pink. F: green. K: purple.
Solvent is omitted for clarity. See SI for structure detail.
A new strategy is to use Rhenium hydride (Re-H) as the Lewis
base part of FLPs to activate CO2 and H2. [9] Recently, based on
the finding of
a stable carbene Copper hydride (Cu-H)
[a]
Dr.T. X. Zhao, Assoc. Prof. X. B. Hu, Prof. Y. T. Wu, Prof. Z. B.
Zhang
Separation Engineering Research Center, School of Chemistry and
Chemical Engineering
Nanjing University
Nanjing 210093 (P. R. China)
analogues, [21a] Bertrand’s and our group reported a tandem Cu-
H Lewis pair system for the hydrogenation of CO2 to formate [21b]
In this system, the Cu-H activates CO2 and BCF/DBU
(DBU=1,8-diazabicyclo[5.4.0]-undec-7-ene) splits H2. However,
.
noble- or first-row transition-metals are still required in these
methods [9, 21b]
Herein, we reported an unexpected finding that, being
E-mail: huxb@nju.edu.cn; ytwu@nju.edu.cn
Supporting information for this article is available on the WWW
under http://www.angewandte.org or from the author.
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10.1002/anie.201809634
Angewandte Chemie International Edition
COMMUNICATION
different from these classical FLPs [16-19], or BCF/Re-H and Cu-H
systems
(M=Na, K, and Cs) can serve as effective catalysts for the
hydrogenation of CO2 to formate with H2.
(Figure 2b) [22]. However, under the reaction condition, it is not
able to isolate the H2 splitting intermediate K[BCF-H].
Theoretical calculations showed that the energy of H2 splitting
product was 6.3 kcal/mol higher than that of the starting material.
Hence, it is reasoned that K[BCF-H] and K2[(BCF)2-CO3] should
be in equilibrium under the reaction conditions [18c]. To our
delight, the formation of formate in the presence of H2 and CO2
unequivocally supports the validity of our hypothesis that a
reversible splitting of hydrogen must exist in the reaction
process. It was also confirmed by another evidence that when
CO2 was introduced into the solution of BCF and KH, the same
[9,
21b], a Lewis pair forming from BCF and M2CO3
The reaction between BCF and K2CO3 (2:1 mole ratio) in THF
at room temperature can generate a Lewis pair (K2[(BCF)2-CO3])
(Figure 1a). After work up, K2[(BCF)2-CO3] was isolated as a
white, air- and moisture-stable solid in 94% yield, and its
structure was confirmed by single-crystal X-ray diffraction
(Figure 1b) [22], NMR and MS analysis. The 11B-NMR spectrum
(25 oC) showed an obvious shift from 2.6 to -4.1 ppm when the
product was formed (BCF vs. K2[(BCF)2-CO3]). The structure of
product of BCF-HCO2K exactly was detected, considering that
the interesting K2[(BCF)2-CO3] includes two BCF and one K2CO3. [BCF-H]- can react with CO2
.
[17c, 17d]
Even when the reaction was performed between BCF and
K2CO3 with the mole ratio 1:1, the K2[(BCF)2-CO3] was still
obtained rather than 1:1 BCF-K2CO3 adduct. Being different
from the well-known FLPs in which sterical inhibition plays vital
Table 1 Hydrogenation of CO2 to formate with H2.[a]
Entry
Lewis acid
Base
CO2:H2
(bar)
TON[c]
(mmol)[b]
1
2
3
4
5
6
7
8
BCF(0.01)
BCF (0.01)
None
K2CO3
None
K2CO3
TMP
20 : 40
20 : 40
20 : 40
20 : 40
20 : 40
20 : 40
20 : 40
20 : 40
20 : 40
20 : 40
0 : 40
35
0
0
0
23
92
54
16
27
role and it is difficult to form the classical Lewis acid-base
[16-18]
adducts,
the base in K2[(BCF)2-CO3] is too small to show
BCF(0.01)
BCF(0.01)
BCF(0.01)
3,5-BArF2(0.01)
BPh3(0.01)
BCF(0.01)
BCF(0.01)
BCF(0.01)
BCF(0.01)
BCF(0.001)
BCF(0.01)
BCF(0.001)
BCF(0.001)
BCF(0.001)
BPh3(0.01)
steric hindrance effect. Thus, K2[(BCF)2-CO3] should not be
frustrated Lewis pair. Theoretical calculations using B3LYP-
D3(BJ)/6-311+G* method showed that the [(BCF)2-CO3] part
carries exactly two negative charges ([(BCF)2-CO3]2-), indicating
that K2[(BCF)2-CO3] is in fact an ionic compound. There are two
B-O bonds in K2[(BCF)2-CO3] with a length of 1.537Å, being
obviously shorter than the distance for a Lewis pair to be
frustrated (e.g. 1.65 Å in BCF/pyridines [18e]) and longer than that
of the B-O single bond in pure organic system (e. g. 1.36 Å in
pyridonate borane complex[18t]).
Na2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
KHCO3
KHCO3
KHCO3
Cs2CO3
Cs2CO3
K2CO3
Cs2CO3
KHCO3
K2CO3
9[d]
10
11
12[e,f]
13[e,f]
14
15[f]
16
17[e,f]
18[e,f]
22
0
20 : 40
20 : 40
10 : 20
20 : 40
20 : 40
20 : 40
20 : 40
504
3941
35
272
653
3386
320
[a] Standard conditions: base (10 mmol), solvent (THF, 10 ml), reaction time
(48 h), temperature (160 oC). [b] 3,5-BArF2: tris(3,5-difluorophenyl)borane.
BPh3: triphenylborane. [c] The amount of formate was determined by 1H NMR
with DMF as the internal standard. TON=(mole of formate)/(mole of Lewis
acid). [d] 100 oC instead of 160 oC. [e] 10 mmol K was added. [f] Base (5
mmol).
The interesting stoichiometric reactions described in Figures 1
and 2 encourage us to explore the possibility of catalytic
hydrogenation of CO2. It is exciting to find that a TON of 35 was
obtained for the hydrogenation of CO2 to formate in the
presence of both BCF and K2CO3 (Entry 1, Table 1). As
comparison, no reaction happens using BCF or K2CO3
separately (Entries 2 and 3). As expected, the results show that
BCF/TMP cannot serve as catalyst under the standard condition
(Entry 4), due to the unstability of the BCF/TMP system, though
[19a]
they worked well for the stoichiometric hydrogenation of CO2
In addition, both the Lewis acids and bases show important
effect on the catalytic reactivity. The experiments displayed that
replacing K2CO3 by Na2CO3 led to a lower TON (Entry 5),
whereas use of Cs2CO3 gave a higher TON (Entries 6 and 16).
Excess base is necessary because it can move the
unfavourable equilibrium of CO2 reduction towards the producing
of formate.[4b] Replacing BCF by 3,5-BArF2 or BPh3 resulted in
poor catalytic reactivity (Entries 7 and 8). It is worth noticing that
a TON of 27 can be obtained at 100 oC in the presence of
BCF/Cs2CO3 (Entry 9), being much higher than that using
BCF/Re-H as catalyst (TON=6 at 120oC and CO2:H2=20:40 bar)
.
Figure 2. (a) Reactions to produce BCF-HCO2K by the hydrogenation of CO2.
BCF=B(C6F5)3; (b) X-ray structure of BCF-HCO2K dimer. C: gray. O: red. H:
white. B: pink. F: green. K: purple. Solvent is omitted for clarity. See SI for
structure detail.
It is interesting to find that K2[(BCF)2-CO3] can react with H2
and then reacts with CO2 in the obtained solution to form BCF-
formate (BCF-HCO2K) (Figure 2a). BCF-HCO2K was fully
characterized, including single-crystal X-ray diffraction analysis
[9]
.
BCF/KHCO3 can also be used as catalyst (Entry 10, Table 1).
The corresponding TON is slightly lower than that of BCF/K2CO3.
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10.1002/anie.201809634
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In the absence of CO2, no reaction happens (Entry 11), which
excludes the possibility of hydrogenation of bicarbonates to
formate using the catalytic system reported here [11b]. Our many
efforts to synthesize the BCF-KHCO3 Lewis pair failed (K[BCF-
optimized transition states (Bond length are shown in Å). More details about
the calculations and optimized structures can be found in SI.
Based on the results obtained above, a possible mechanism
HCO3] in Figure 1a). Instead, K2[(BCF)2-CO3] was unexpectedly of CO2 hydrogenation in the presence of BCF/K2CO3 is
generated in the reaction between BCF and KHCO3. H2CO3 is proposed (Scheme 1). The reaction process consists of two
not stable in anhydrous solvent. The free CO2 produced by cycles. Cycle 1 (solid line) represents the main catalytic reaction,
decomposition of H2CO3 was detected by 13C NMR (Figure S6), including the formation of Lewis pair K2[(BCF)2-CO3] from BCF
which also supports the formation of K2[(BCF)2-CO3] via reaction and K2CO3, the splitting of H2 by K2[(BCF)2-CO3], and the
between KHCO3 and BCF.To the best of our knowledge, insertion of CO2 into K[BCF-H] to produce HCO2K. Cycle 2 (dash
carbonate reacting with H2CO3 to produce bicarbonates is line) demonstrates the role of K as an additive. The reaction
spontaneous in thermodynamics. The formation of stable between K2[(BCF)2-CO3] and H2 can generate K[BCF-H] and
K2[(BCF)2-CO3] via the reaction between BCF and KHCO3 is K[BCF-HCO3]. K[BCF-HCO3] is unstable and converts into
unusual. It seems to make the well-known process reversed. K2[(BCF)2-CO3] fast. Meanwhile, H2CO3 is formed. The addition
Theoretical calculations demonstrate that the reaction between of K can eliminate H2CO3 and regenerate K2CO3. Therefore,
BCF and KHCO3 to produce K2[(BCF)2-CO3] is highly exothermic higher TON can be obtained in the presence of K, even though
(-93.9 kcal/mol). Because there are H2CO3 forming in the the hydrogenation of CO2 performs well without K.
BCF/KHCO3 system, we reasoned that the removal of H2CO3
Theoretical calculations were further performed to explore the
should benefit the hydrogenation of CO2. For this purpose, catalytic hydrogenation process (Figure 3). A simplified model of
potassium (K) was added into the reaction system and the TON K2[(BCF)2-CO3] was used, which contains both BCF and CO3
value was greatly enhanced from 22 to 504 (Entry 12). Lowering group. The theoretical method adopted here is accurate enough
the concentration of BCF by one order of magnitude allows us to to reproduce the X-ray structure of the catalytic system (Figure
[23]
achieve TON up to 3941(Entry 13).
S11). H2 can be inserted into the B-O bond
and splitted
heterolytically with a barrier of 31.8 kcal/mol for TS1 (37.2
kcal/mol for TS1THF). The H-H bond length in TS1THF is 0.787 Å,
being quite close to the data of H2 activated by well-defined FLP
(e.g. 0.75 Å in ansa-aminoborane[18q], 0.78 Å in carbene-borane
system[18m]
) or metal based catalysts (e.g. 0.78 in cis-
RuH2(PH3)4[4a]). Following TS1THF, K[BCF-H] can be generated
as the intermediate. Then, the hydride can be transferred to CO2
via TS2THF with a barrier of 17.7 kcal/mol. The total free energy
change from the reactant to the product is -9.2 kcal/mol.
In summary, we have disclosed the first catalytic process of
CO2 hydrogenation to formate in the presence of transition metal
free catalyst (BCF/M2CO3, M=Na, K, and Cs). Stoichiometric
reactions reveal that the Lewis pair K2[(BCF)2-CO3] formed from
BCF and K2CO3 can activate both H2 and CO2 effectively to
produce formate. Further catalytic experiments using
BCF/Cs2CO3 as catalyst result in formate with TON up to 3941.
It is believed that this new catalytic system based on Lewis pair
but not transition metals is of great benefit for the methodology
and technology in the simultaneous conversion of CO2 and H2.
Scheme 1. Proposed catalytic process for the hydrogenation of CO2 with H2.
Cycle 1: solid line; cycle 2: dash line.
Acknowledgements
This work was supported by National Natural Science
Foundation of China (No.21878141, 21676134, and 21576129).
Conflict of interest
The authors declare no conflict of interest.
Keywords: carbon dioxide • hydrogenation • formate • Lewis
Figure 3. (a) The energy profile (in kcal/mol) for the hydrogenation of CO2
obtained by PCM calculation using B3LYP-D3(BJ)/6-311++G** method.
Energies in parenthesis were results without explicit THF. (b) The structures of
pair • homogeneous catalysis
[1]
a) W. Wang, Y. Himeda, J. T. Muckerman, G. F. Manbeck, E. Fujita,
Chem. Rev. 2015, 115, 12936-12973; b) J. Klankermayer, S.
This article is protected by copyright. All rights reserved.

10.1002/anie.201809634
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Wesselbaum, K. Beydoun, W. Leitner, Angew. Chem. Int. Ed. 2016, 55,
7296-7343; Angew. Chem. 2016, 128, 7416-7467; c) A. Alvarez, A.
Bansode, A. Urakawa, A. V. Bavykina, T. A. Wezendonk, M. Makkee, J.
Gascon, F. Kapteijn, Chem. Rev. 2017, 117, 9804-9838.
Baumann, R. Jackstell, M. Beller, Angew. Chem. Int. Ed. 2017, 56,
1890-1893; Angew. Chem. 2017, 129, 1916-1919.
[13] a) R. C. Cammarota, M. V. Vollmer, J. Xie, J. Ye, J. C. Linehan, B. A.
Burgess, A. M. Appel, L. Gagliardi, C. C. Lu, J. Am. Chem. Soc. 2017,
139, 14244-14250; b) S. A. Burgess, A. J. Kendall, D. R. Tyler, J. C.
Linehan, A. M. Appel, ACS Catal. 2017, 7, 3089-3096.
[2]
a) T. C. Johnson, D. J. Morris, M. Wills, Chem. Soc. Rev. 2010, 39, 81-
88; b) J. F. Hull, Y. Himeda, W. H. Wang, B. Hashiguchi, R. Periana, D.
J. Szalda, J. T. Muckerman, E. Fujita, Nature Chem. 2012, 4, 383-388;
c) Q. Y. Bi, X. L. Du, Y. M. Liu, Y. Cao, H. Y. He, K. N. Fan, J. Am.
Chem. Soc. 2012, 134, 8926-8933; d) Z. L, Wang, J. M. Yan, Y. Ping, H.
L. Wang, W. T. Zheng, Q. Jiang,Angew. Chem. Int. Ed. 2013, 52, 4406-
4409; Angew. Chem. 2013, 125, 4502-4505; e) D. Mellmann, P.
Sponholz, H. Junge, M. Beller, Chem. Soc. Rev. 2016, 45, 3954-3988.
a) J. Graciani, K. Mudiyanselage, F. Xu, A. E. Baber, J. Evans, S. D.
Senanayake, D. J. Stacchiola, P. Liu, J. Hrbek, J. F. Sanz, J. A.
Rodriguez, Science 2014, 345, 546-550; b) S. Kattel, P. J. Ramirez, J.
G. Chen, J. A. Rodriguez, P. Liu, Science 2017, 355, 1296-1299.
a) Y. Musashi, S. Sakaki, J. Am. Chem. Soc. 2000, 122, 3867-3877; b)
T. Schaub, R. A. Paciello, Angew. Chem. Int. Ed. 2011, 50, 7278-7282;
Angew. Chem. 2011, 123, 7416-7420; c) S. Bontemps, L. Vendier, S.
Sabo-Etienne, Angew. Chem. Int. Ed. 2012, 51, 1671-1674; Angew.
Chem. 2012, 124, 1703-1706; d) S. Moret, P. J. Dyson, G. Laurenczy,
Nature Commun. 2014, 5, 4017; e) N. M. Rezayee, C. A. Huff, M. S.
Sanford, J. Am. Chem. Soc. 2015, 137, 1028-1031; f) R. Kuriki, K.
Sekizawa, O. Ishitani, K. Maeda, Angew. Chem. Int. Ed. 2015, 54,
2406-2409; Angew. Chem. 2015, 127, 2436-2439; g) J.
Kothandaraman, A. Goeppert, M. Czaun, G. A. Olah, G. K. S. Prakash,
J. Am. Chem. Soc. 2016, 138, 778-781; h) K. Rohmann, J. Kothe, M. W.
Haenel, U. Englert, M. Holscher, W. Leitner, Angew. Chem. Int. Ed.
2016, 55, 8966-8969; Angew. Chem. 2016, 128, 9112-9115; i) Z. Li, T.
M. Rayder, L. Luo, J. A. Byers, C. Tsung, J. Am. Chem. Soc. 2018, 140,
8082− 8085; j) C. A. Huff, M. S. Sanford, ACS Catal. 2013, 3, 2412-
2416; k) A. Weilhard, M. I. Qadir, V. Sans, J. Dupont, ACS Catal. 2018,
8, 1628-1634.
[14] a) C. M. Zall, J. C. Linehan, A. M. Appel, ACS Catal. 2015, 5, 5301-
5305; b) C. M. Zall, J. C. Linehan, A. M. Appel, J. Am. Chem. Soc.
2016, 138, 9968-9977.
[15] a) F. Bertini, M.Glatz, N. Gorgas, B.Stoeger, M.Peruzzini, L. F.Veiros, K.
Kirchner, L.Gonsalvi, Chem. Sci. 2017, 8, 5024-5029; b) S. Kar, A.
Goeppert, J. Kothandaraman, G. K. S. Prakash, ACS Catal. 2017, 7,
6347-6351; c) A. Dubey, L. Nencini, R. R. Fayzullin, C. Nervi, J. R.
Khusnutdinova, ACS Catal. 2017, 7, 3864-3868.
[3]
[4]
[16] a) G. C. Welch, R. R. S. Juan, J. D. Masuda, D. W. Stephan, Science
2006, 314, 1124-1126; b) D. W. Stephan, G. Erker, Angew. Chem. Int.
Ed. 2010, 49, 46-76; Angew. Chem. 2010, 122, 50-81; c) D. W.
Stephan, Science 2016, 354, aaf7229.
[17] a) E. Otten, R. C. Neu, D. W. Stephan, J. Am. Chem. Soc. 2009, 131,
9918-9919; b) C. M. Momming, E. Otten, G. Kehr, R. Frohlich, S.
Grimme, D. W. Stephan, G. Erker, Angew. Chem. Int. Ed. 2009, 48,
6643-6646; Angew. Chem. 2009, 121, 6770-6773; c) A. Berkefeld, W.
E. Piers, M. Parvez, J. Am. Chem. Soc. 2010, 132, 10660-10661; d) A.
Berkefeld, W. E. Piers, M. Parvez, L. Castro, L. Maron, O. Eisenstein.
Chem. Sci. 2013, 4, 2152-2162; e) X. Xu, G. Kehr, C. G. Daniliuc, G.
Erker, Angew. Chem. Int. Ed. 2013, 52, 13629-13632; Angew.
Chem. 2013, 125, 13874-13877; f) M. Sajid, A. Lawzer, W. Dong, C.
Rosorius, W. Sander, B. Schirmer, S. Grimme, C. G. Daniliuc, G. Kehr,
G. Erker, J. Am. Chem. Soc. 2013, 135, 18567-18574; g) R. Liedtke, F.
Scheidt, J. Ren, B. Schirmer, A. J. Cardenas, C. G. Daniliuc, H. Eckert,
T. H. Warren, S. Grimme, G. Kehr, G. Erker, J. Am. Chem. Soc. 2014,
136, 9014-9027; h) J. C. M. Pereira, M. Sajid, G. Kehr, A. W. Wright, B.
Schirmer, Z. Qu, S. Grimme, G. Erker, P. C. Ford, J. Am. Chem. Soc.
2014, 136, 513-519; i) M. Courtemanche, M. Legare, L. Maron, F.
Fontaine, J. Am. Chem. Soc. 2014, 136, 10708-10717; j) L. E.
Longobardi, V. Wolter, D. W. Stephan, Angew. Chem. Int. Ed. 2015, 54,
809-812; Angew. Chem. 2015, 127, 823-826; k) K. Ye, G. Kehr, C. G.
Daniliuc, L. Liu, S. Grimme, G. Erker, Angew. Chem. Int. Ed. 2016, 55,
9216-9219; Angew. Chem. 2016, 128, 9362-9365; l) A. Simonneau, R.
Turrel, L. Vendier, M. Etienne, Angew. Chem. Int. Ed. 2017, 56, 12268-
12272; Angew. Chem. 2017, 129, 12436-12440; m) R. L. Melen,
Angew. Chem. Int. Ed. 2018, 57, 880-882; Angew. Chem. 2018, 130,
890-892.
[5]
[6]
a) F. Hutschka, A. Dedieu, M. Eichberger, R. Fornika, W. Leitner, J. Am.
Chem. Soc.1997, 119, 4432-4443; b) A. Anaby, M. Feller, Y. Ben-David,
G. Leitus, Y. Diskin-Posner, L. J. Shimon, D. Milstein, J. Am. Chem.
Soc. 2016, 138, 9941-9950; c) Q. Qian, J. Zhang, M. Cui, B. X. Han,
Nature Commun. 2016, 7, 11481.
a) R. Tanaka, M. Yamashita, K. Nozaki, J. Am. Chem. Soc. 2009, 131,
14168-14169; b) T. J. Schmeier, G. E. Dobereiner, R. H. Crabtree, N.
Hazari, J. Am. Chem. Soc. 2011, 133, 9274-9277; c) J. F. Hull, Y.
Himeda, W. Wang, B. Hashiguchi, R. Periana, D. J. Szalda, J. T.
Muckerman, E. Fujita, Nature Chem. 2012, 4, 383-388; d) C. Liu, J. Xie,
G. Tian, W. Li, Q. L. Zhou,Chem. Sci. 2015, 6, 2928-2931; e)B. An, L.
Zeng, M. Jia, Z. Li, Z. Lin, Y. Song, Y. Zhou, J. Cheng, C. Wang, W. B.
Lin, J. Am. Chem. Soc. 2017, 139, 17747-17750; f) R. Kanega, N.
Onishi, D. J. Szalda, M. Z. Ertem, J. T. Muckerman, E. Fujita, Y.
Himeda, ACS Catal. 2017, 7, 6426-6429.
[18] a) P. A. Chase, D. W. Stephan, Angew. Chem. Int. Ed. 2008, 47, 7433-
7437; Angew. Chem. 2008, 120, 7543-7547; b) D. Holschumacher, T.
Bannenberg, C. G. Hrib, P. G. Jones, M. Tamm, Angew. Chem. Int. Ed.
2008, 47, 7428-7432; Angew. Chem. 2008, 120, 7538-7542; c) T. A.
Rokob, A. Hamza, I. Papai,J. Am. Chem. Soc. 2009, 131, 10701-10710;
d) C. M. Momming, S. Fromel, G. Kehr, R. Frohlich, S. Grimme, G.
Erker, J. Am. Chem. Soc. 2009, 131, 12280-12289; e)S. J. Geier, A. L.
Gille, T. M. Gilbert, D. W. Stephan, Inorg. Chem. 2009, 48, 10466-
10474; f) G. Eros, H. Mehdi, I. Papai, T. A. Rokob, P. Kiraly, G.
Tarkanyi, T. Soos, Angew. Chem. Int. Ed. 2010, 49, 6559-6563; Angew.
Chem. 2010, 122, 6709-6713; g) S. Grimme, H. Kruse, L. Goerigk, G.
Erker, Angew. Chem. Int. Ed. 2010, 49, 1402-1405; Angew.
Chem. 2010, 122, 1444-1447; h) D. Chen, Y. Wang, J. Klankermayer,
[7]
[8]
K. Mori, T. Sano, H. Kobayashi, H. Yamashita, J. Am. Chem. Soc. 2018,
140, 8902-8909.
X. Zhang, G. Liu, K. Meiwes-Broer, G. Gantefor, K. Bowen, Angew.
Chem. Int. Ed. 2016, 55, 9644-9647; Angew. Chem. 2016, 128, 9796-
9799.
[9]
Y. Jiang, O. Blacque, T. Fox, H. Berke, J. Am. Chem. Soc. 2013, 135,
7751-7760.
[10] Q. Liu, X. Yang, L. Li, S. Miao, Y. Li, Y. Q. Li, X. Wang, Y. Huang, T.
Zhang, Nature Commun. 2017, 8, 1407.
Angew.
Chem.
Int.
Ed.
2010,
49,
9475-9478;
Angew.
[11] a) R. Langer, Y. Diskin-Posner, G. Leitus, L. J. Shimon, Y. Ben-David,
D. Milstein, Angew. Chem. Int. Ed. 2011, 50, 9948-9952; Angew. Chem.
2011, 123, 10122-10126; b) C. Ziebart, C. Federsel, P. Anbarasan, R.
Jackstell, W. Baumann, A. Spannenberg, M. Beller, J. Am. Chem. Soc.
2012, 134, 20701-20704; c) Y. Zhang, A. D. Maclntosh, J. L. Wong, E.
A. Bielinski, P. G. Williard, B. Q. Mercado, N. Hazari, W. H.
Bernskoetter, Chem. Sci. 2015, 6, 4291-4299.
Chem. 2010, 122, 9665-9668; i) Z. Lu, Z. Cheng, Z. Chen, L. Weng, Z.
H. Li, H. Wang, Angew. Chem. Int. Ed. 2011, 50, 12227-12231; Angew.
Chem. 2011, 123, 12435-12439; j) A. M. Chapman, M. F. Haddow, D. F.
Wass, J. Am. Chem. Soc. 2011, 133, 18463-18478; k) F. Bertini, V.
Lyaskovskyy, B. J. Timmer, F. J. de Kanter, M. Lutz, A. W. Ehlers, J. C.
Slootweg, K. Lammertsma, J. Am. Chem. Soc. 2012, 134, 201-204; l) L.
Greb, P. Ona-Burgos, B. Schirmer, S. Grimme, D. W. Stephan, J.
Paradies, Angew. Chem. Int. Ed. 2012, 51, 10164-10168; Angew.
Chem. 2012, 124, 10311-10315; m)T. A. Rokob, I. Bako, A. Stirling, A.
[12] a) M. S. Jeletic, M. T. Mock, A. M. Appel, J. C. Linehan, J. Am. Chem.
Soc. 2013, 135, 11533-11536; b) J. Schneidewind, R. Adam, W.
This article is protected by copyright. All rights reserved.

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COMMUNICATION
Hamza, I. Papai, J. Am. Chem. Soc. 2013, 135, 4425-4437; n) S. Wei,
H. F. Du, J. Am. Chem. Soc. 2014, 136, 12261-12264; o) E. R. Clark, M.
J. Ingleson, Angew. Chem. Int. Ed. 2014, 53, 11306-11309; Angew.
Chem. 2014, 126, 11488-11491;p) S. Li, G. Li, W. Meng, H. F. Du, J.
E. Otten, R. Frohlich, G. Kehr, D. W. Stephan, G. Erker,
Organometallics 2012, 31, 2367-2378; d) S. D. Tran, T. A. Tronic, W.
Kaminsky, D. M. Heinekey, J. M. Mayer, Inorg. Chim. Acta 2011, 369,
126-132.
Am. Chem. Soc. 2016, 138, 12956-12962; q) K. Chernichenko, B. Kotai, [20] L. Liu, N. Vankova, T. Heine, Phys. Chem. Chem. Phys. 2016, 18,
I. Papai, V. Zhivonitko, M. Nieger, M. Leskela, T. Repo, Angew. Chem.
Int. Ed. 2015, 54, 1749-1753; Angew. Chem. 2015, 127, 1769-1773;r)
O. J. Metter, S. J. Forrest, H. A. Sparkes, I. Manners, D. F. Wass, J.
Am. Chem. Soc. 2016, 138, 1994-2003; s) S. Mummadi, D. K. Unruh, J.
Zhao, S. H. Li, C. Krempner, J. Am. Chem. Soc. 2016, 138, 3286-3289;
t) U. Gellrich, Angew. Chem. Int. Ed. 2018, 57, 4779-4782; Angew.
Chem. 2018, 130, 4869-4872; u) Y. Ding, X. Huang, X. Yi, Y. X. Qiao, X.
Y. Sun, Z. Zheng, D. S. Su, Angew. Chem. Int. Ed. 2018, 57, DOI:
10.1002/anie.201803977; Angew. Chem. 2018, 130, DOI: 10.1002/
anie.201803977.
3567-3574.
[21] a) X. B. Hu, M. Soleilhavoup, M. Melaimi, J. Chu, G. Bertrand, Angew.
Chem. Int. Ed.2015, 54, 6008-6011; Angew. Chem. 2015, 127, 6106-
6109; b) E. A. Romero, T. X. Zhao, R. Nakano, X. B. Hu, Y. T. Wu, R.
Jazzar, G. Bertrand, Nature Catal. 2018, 1, 743-747.
[22] CCDC 1856668 (K2[(BCF)2-CO3]) and 1856669 (BCF-HCO2K) contain
the supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
[23] a) D. J. Scott, M. J. Fuchter, A. E. Ashley, Angew. Chem. Int. Ed.2014,
53, 10218-10222; Angew. Chem. 2014, 126, 10382-10386; b) T. Mahdi,
D. W. Stephan, J. Am. Chem. Soc. 2014, 136, 15809-15812; c) D. J.
Scott, M. J. Fuchter, A. E. Ashley, J. Am. Chem. Soc. 2014, 136,
15813-15816.
[19] a) A. E. Ashley, A. L. Thompson, D. O'Hare, Angew. Chem. Int. Ed.
2009, 48, 9839-9843; Angew. Chem. 2009, 121, 10023-10027; b) M.
Courtemanche, A. P. Pulis, E. Rochette, M. Legare, D. W. Stephan, F.
Fontaine, Chem. Commun. 2015, 51, 9797-9800; c) T. Voss, T. Mahdi,
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Entry for the Table of Contents (Please choose one layout)
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No transition metal for both. The
first example of transition metal free
Tianxiang Zhao, Xingbang Hu*, Youting
Wu* and Zhibing Zhang
CO2
hydrogenation
to
formate
catalyzed by BCF/M2CO3 (M=Na, K,
and Cs) was reported with TON up to
Hydrogenation of CO2 to Formate
with H2: Transition Metal Free
3941.
Mechanism
researches
revealed that BCF reacted with K2CO3
to afford a Lewis pair K2[(BCF)2-CO3]
which can react with H2 and CO2 to
produce formate.
H2
Catalyst Based on a Lewis Pair
+
CO2
K2CO3
HCO2K
Transition Metal Free
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