CO2-Selective Absorbents in Air: Reverse Lipid Bilayer Structure Forming Neutral Carbamic Acid in Water without Hydration

Article abstract of DOI:10.1021/jacs.7b01049

Emission gas and air contain not only CO₂ but also plentiful moisture, making it difficult to achieve selective CO₂ absorption without hydration. To generate absorbed CO₂ (wet CO₂) under heating, the need for external energy to release the absorbed water has been among the most serious problems in the fields of carbon dioxide capture and storage (CCS) and direct air capture (DAC). We found that the introduction of the hydrophobic phenyl group into alkylamines of CO₂ absorbents improved the absorption selectivity between CO₂ and water. Furthermore, ortho-, meta-, and para-xylylenediamines (OXDA, MXDA, PXDA, respectively) absorbed only CO₂ in air without any hydration. Notably, MXDA·CO₂ was formed as an anhydrous carbamic acid even in water, presumably because it was covered with hydrophobic phenyl groups, which induces a reverse lipid bilayer structure. Dry CO₂ was obtained from heating MXDA·CO₂ at 103-120 °C, which was revealed to involve chemically the Grignard reaction to form the resulting carboxylic acids in high yields.

Full text of DOI:10.1021/jacs.7b01049

Subscriber access provided by UNIV OF CALIFORNIA SAN DIEGO LIBRARIES
Communication
CO2-selective absorbents in air: Reverse lipid bilayer structure
forming neutral carbamic acid in water without hydration
Fuyuhiko Inagaki, Chiaki Matsumoto, Takashi Iwata, and Chisato Mukai
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.7b01049 • Publication Date (Web): 17 Mar 2017
Downloaded from http://pubs.acs.org on March 17, 2017
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Journal of the American Chemical Society is published by the American Chemical
Society. 1155 Sixteenth Street N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 7
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
CO2-selective absorbents in air: Reverse lipid bilayer structure form-
ing neutral carbamic acid in water without hydration
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Fuyuhiko Inagaki*, Chiaki Matsumoto, Takashi Iwata and Chisato Mukai
Division of Pharmaceutical Sciences, Graduate School of Medical Sciences, Kanazawa University, Kakumaꢀmachi, Kanazaꢀ
wa 920ꢀ1192 (Japan)
Supporting Information Placeholder
gents using low molecular weight compounds, and we
found that the absorption of CO2 in air using MEA
formed (CO2)·3(MEA)·3(H2O) (1) in 85~95% yields,
ABSTRACT: Emission gas and air contain not only CO2
but also plentiful moisture, making it difficult to achieve
selective CO2 absorption without hydration. To generate
absorbed CO2 (wet CO2) under heating, the need for exꢀ
ternal energy to release the absorbed water has been
among the most serious problems in the fields of carbon
dioxide capture and storage (CCS) and direct air capture
(DAC). We found that the introduction of the hydrophoꢀ
bic phenyl group into alkylamines of CO2 absorbents
improved the absorption selectivity between CO2 and
water. Furthermore, orthoꢀ, metaꢀ, and paraꢀ
xylylenediamines (OXDA, MXDA, PXDA, respectiveꢀ
ly) absorbed only CO2 in air without any hydration. Noꢀ
tably, MXDA·CO2 was formed as an anhydrous carbamꢀ
ic acid even in water, presumably because it was covꢀ
ered with hydrophobic phenyl groups, which induces a
reverse lipid bilayer structure. Dry CO2 was obtained
from heating MXDA·CO2 at 103~120 °C, which was
revealed to chemically involve the Grignard reaction to
form the resulting carboxylic acids in high yields.
2ꢀ
suggesting the generation of carbonate ions (CO3 or
ꢀ
HCO3 ) (Figure 1c).15 The absorption ratio of
(CO2)·3(MEA)·3(H2O) (1) revealed that MEA functions
as both a hygroscopic material and a CO2 sorbent. Simiꢀ
lar contamination must be caused in the CCS systems
using MEA because exhaust gas also contains water deꢀ
rived from burned fossil fuels. On these grounds, our
current aim is to explore CO2 absorbents with no hygroꢀ
scopic properties.
Plausible mechanisms for the absorption of CO2 and
water using amines are shown in Figure 1a. Acidic CO2
is captured by basic amines to form the corresponding
carbamic acid A (RR’NCO2H). Then, the hydration of A
yields
ammonium
hydrogencarbonate
B
+
ꢀ
(RR’NH2 HCO3 ). In parallel, carbamic acid A would
also be neutralized with another amine to provide the
+
ꢀ
neutral carbamic acid C (RR’NH2 RR’NCO2 ). Both the
neutralization of B with another amine and the hydration
of C yield the common bisammonium carbonate D
+
2ꢀ
([RR’NH2 ]2CO3 ). We hypothesize that if the hydroꢀ
phobic moiety is introduced at the substitution group of
the amine (R), the hydration of the neutral carbamic acid
2 might be inhibited owing to the hydrophobicity (Figꢀ
ure 1b). To pursue the above goal, we selected amines
bearing benzene moieties, such as benzylamine (BZA,
4a), phenethylamine (PEA, 4b), Nꢀmethylbenzylamine
(NMBZA, 4c), pꢀmethoxybenzylamine (PMBZA, 4d),
mꢀxylylenediamine (MXDA, 4e), pꢀxylylenediamine
(PXDA, 4f), and oꢀxylylenediamine (OXDA, 4g) (Figꢀ
ure 1c).
Carbon dioxide capture and storage (CCS)1ꢀ3 is curꢀ
rently one of the most effective methods for reducing
4ꢀ7
CO2 in emission gas. Direct air capture (DAC)8ꢀ15 is
another technology for reducing CO2 gas. From the perꢀ
spective of the installation location, DAC systems could
be more valuable than CCS because a DAC system capꢀ
tures CO2 (ca. 400 ppm = 0.04 vol%) from the air, which
is abundant everywhere on earth. The adsorꢀ
bents/absorbents for CCS and DAC are mainly classified
into three types: amines (e.g., monoethanolamine
[MEA], polymeric amine), inorganic salts, and metalꢀ
organic frameworks (MOFs)16ꢀ21. Emission gas and air
contain not only CO2 but also plentiful moisture, and
water contamination requires additional external energy
at the step of CO2 generation under heating condition.
However, as far as we know, no CO2 absorbent without
water contamination has been reported. Recent efforts in
our laboratory have focused on investigating DAC reaꢀ
Firstly, CO2 absorption from the ambient air was exꢀ
amined in an enclosed space (35.7 L). The results are
shown in Figure 2a. The initial CO2 concentration (502ꢀ
582 ppm, 0.84ꢀ0.97 mmol CO2) was highly dependent
on uncontrollable variables in the experimental room.
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 2 of 7
a
sis of 4b,d containing half the amount of CO2, amine,
and a small amount of water seemed an equilibrium beꢀ
O
H2O
R
R
O
R
1
2
3
4
5
6
7
8
O
NH2
N
+
CO2
NH
+
ꢀ
OH
R'
OH
R'
R'
B
tween ammonium carbamate C (RR’NH2 RR’NCO2 )
A
+
2ꢀ
R NH
R'
R NH
R'
and bisammonium carbonate D ([RR’NH2 ]2CO3 ). Furꢀ
thermore, similar examinations using several alkyl
amines (Nꢀmethylaminoethanol, ethylenediamine, N,N’ꢀ
dimethylethylenediamine, diethylenetriamine) were also
conducted for comparison (details are shown in supportꢀ
ing information). The alkylamines absorbed approxiꢀ
mately 5.5~16 times more H2O than CO2. Nevertheless,
while PEA 4b and PMBZA 4d allowed some hydration,
we could trust that the hydrophobicity from introducing
the phenyl moiety was effective for selective absorption.
Furthermore, we found that the xylylenediamines 4e-g
selectively absorbed CO2 without any water contaminaꢀ
tion. As the resulting MXDA·CO2, PXDA·CO222, and
OXDA·CO2 were insoluble or have very low solubility
in most solvents, solid 13CꢀNMR was used for the analyꢀ
sis (Figure 2d). All complexes showed one peak near
163~165 ppm (carbonyl moiety).23,24 Judging from the
results of elemental analysis and solid 13CꢀNMR,
MXDA·CO2, PXDA·CO222, and OXDA·CO2 would
indicate the intermediate of neutral carbamic acid C
O
N
R
H2O
O
R
R
O
NH2
NH
H2N
H3N
2 O
O
O
R
R'
R'
R'
C
D
O
3
R'
X
H2O
b
c
O
hydrophobic
group
9
R
NH
R
3 O
R
NH3
O
N
H
R
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
2
?
NH2
Me
NH2
NH2
N
H
MeO
Benzylamine Phenetylamine NꢀMethylbenzylamine pꢀMethoxybenzylamine
(BZA, 4a)
(PEA, 4b)
(NMBZA, 4c)
(PMBZA, 4d)
NH2
NH2
NH2
NH2
NH2
NH2
mꢀxylylenediamine pꢀxylylenediamine oꢀxylylenediamine
(MXDA, 4e) (PXDA, 4f)
(OXDA, 4g)
Figure 1. CO2 absorption/generation systems sideꢀbyꢀside
with hydration/dehydration. a. Plausible mechanism for the
reaction of amines, CO2, and water. b. Our hypothesis reꢀ
garding hydration blocking for the hydrophobic groups on
the amines. c. Candidates for the amines bearing hydroꢀ
phobic moieties.
+
ꢀ
(RR’NH2 RR’NCO2 : Figure 1a). Based on these invesꢀ
tigations, we finally judged that MXDA 4e was an optiꢀ
mum CO2 absorbent without hydration.
When 0.33 mL (5.0 mmol) of BZA 4a was incubated in
the sealed box, the CO2 concentration immediately deꢀ
creased from 551 ppm to less than 50 ppm within 14 h,
which is quite similar to the previously reported result
for MEA. The absorption ability of PEA 4b, PMBZA
4d, MXDA 4e, and OXDA 4g were also similar to that
of BZA 4a. Furthermore, the CO2 absorption rate of
PXDA 4f was slightly slower than that of MEA 1. The
absorption ability of NMBZA 4c was obviously inferior
to those of the other amines. Next, we investigated the
ratio of CO2 absorption in air using several amines (4b,
4d-f). We omitted the highly volatile BZA 4a, NMBZA
4c, which exhibits low absorbency, and OXDA 4g,
which is too expensive (ca. 1850 times the price of
MXDA 4e). For this experiment, 75 mmol of the amines
(4b, 4d-f) was placed on a scale exposed to air (i.e., not
enclosed, CO2 ca. 300~600 ppm), and it was weighed
over time. The average mass increases over time from
three replicates are shown in Figure 2b. Although PEA
4b acted as a CO2 absorbent in the enclosed space, the
total amount decreased owing to its volatility. PXDA 4f
gradually increased in weight. The initial rate of increase
using PMBZA 4d was faster than that of PXDA 4f. Both
the increment and rate of MXDA 4e represented the best
results. To determine the composition of the mixture
between amines (4b-g) and air, elemental analyses were
then conducted (Figure 2c). Samples collected after 2
weeks were compared and analysed, revealing that the
mixture x(CO2)·y(PEA 4b)·z(H2O) contained CO2, PEA
4b, and H2O at a ratio of approximately 9 : 4 : 1. The
ratio among CO2, PMBZA 4d, and H2O was the same as
the ratio for 4b. Based on the results of elemental analyꢀ
a
b 3.5
3
2.5
2
1.5
1
PEA 4b
PMBZA 4d
MXDA 4e
PXDA 4f
0.5
0
0
1
2
3
4
5
6
7
-0.5
-1
Absorp; on ; me/day →
air
ca. CO2
300~600 ppm
c
MXDA·CO2
d
DA
amines
x(CO2)—y(amine)—z(H2O)
rt, 2 weeks
OXDA·CO2
CO2 amine H2O
CO2 : H2O
DA
x
1
y
3
9
9
1
1
1
z
3
1
1
0
0
0
amine
MEA
PEA 4b
1 : 3
4
4
1
1
1
1 : 0.25
1 : 0.25
1 : 0
1 : 0
1 : 0
PXDA·CO2
PMBZA 4d
MXDA 4e
PXDA 4f
OXDA 4g
DA
200
150
100
50
0
Chemical Shift (ppm)
Figure 2. Alkylamines bearing phenyl moieties selectively
absorb CO2 rather than water. a. The ability of alkylamine
derivatives 4 (5 mmol) to absorb atmospheric CO2 in sealed
box (35.7 L). b. The average increment of the reaction with
alkylamines 4b,d-f (75 mmol) and open air. c. The results
of elemental analysis (within ±0.4% error) using products
derived from alkylamines 4b,d-g and air for 2 weeks at
room temperature. d. The spectra of solid 13CꢀNMR for the
insoluble
CO2ꢀabsorbed
complexes
MXDA·CO2,
OXDA·CO2, and PXDA·CO2.
Our next experiments focused on clarifying water reꢀ
sistance using MXDA 4e. The reaction of MXDA 4e
under abundant air yielded the MXDA·CO2 complex 5e
in quantitative yields (Figure 3a). The generating solid
ACS Paragon Plus Environment

Page 3 of 7
Journal of the American Chemical Society
MXDA·CO2 stayed in solution as precipitations or susꢀ between the phenyl moiety and hydrogen bond is shown
1
2
3
4
5
6
7
8
pension under mixing condition. Although the liquid
MXDA 4e was highly soluble in water, the resulting
solid MXDA·CO2 5e showed very low solubility in waꢀ
ter (ca. 0.463 × 10ꢀ3 mol/L). Exposing the solution of
MXDA 4e to CO2 gas in water also provided the same
solid. More recently, Zhu and coꢀworkers25 reported that
the reaction of MXDA and 1 atm of dry CO2 formed
MXDA·1.1(CO2). However, the product was speculaꢀ
tively identified based on the amount of released CO2,
and no structural evidence of MXDA·1.1(CO2) was reꢀ
ported. In our examination, MXDA fully reacted with
CO2 at a 1:1 ratio. To elucidate the composition and
structure of the product, Xꢀray crystallography was perꢀ
formed. Despite the very low solubility of MXDA·CO2
5e, a crystal was obtained from a water solution for the
Xꢀray analysis. The ORTEP result (Figure 3b) clearly
proved that 1) the structure contains no water, 2) the
ratio of MXDA:CO2 was 1 : 1, and 3) MXDA·CO2 5e
contains a carbamic acid, which is neutralized with anꢀ
other amine. Thus, the formed MXDA·CO2 5e must be
selfꢀassembled without hydration, even in water.
in Figure 4. The network of hydrogen bonds is covered
on both surfaces with hydrophobic phenyl groups.
ORTEP drawings from the xyꢀ and yzꢀface are also indiꢀ
cated in Figure 4b,c. There are two types of layers, the
hydrophobic layer of phenyl groups and the hydrophilic
layer of hydrogen bonds. The hydrophilic layer is sandꢀ
wiched between two hydrophobic layers (Figure 4a).
The assembled complex seems to form the reverse strucꢀ
ture a lipid bilayer. Both faces consisting of hydrophobic
layers could prevent water from penetrating into the hyꢀ
drophilic layer.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
xyꢀface
b
a
yzꢀface
hydrophobic layer
hydrophilic layer
hydrophobic layer
xyꢀface
yzꢀface
c
ball color
gray: carbon
blue: nitrogen
red: oxygen
Figure 4. MXDA·CO2 5e forming reverse structure of lipid
bilayer. a. Pattern diagram of MXDA·CO2 5e. b. ORTEP
drawing of 5e from xyꢀface showing the composition of the
hydrogen network between the carbonyl oxygen lone pair
and the amine proton (blue dotted lines). c. ORTEP drawꢀ
ing of 5e from yzꢀface showing the composition of the hyꢀ
drogen network between the hydroxyl proton and the amine
lone pair (red dotted lines).
a
b
air
NH2
NH
C
rt
>99% yield
NH2
NH2
MXDA 4e
liquid
water soluble
O
OH
MXDA—CO2 5e
solid
very low water solublity
(<0.463 x 10ꢀ3 mol/L in H2O)
c
d
NH
H
NH
H
H
O
O
O
2.776 Å
Encouragingly, the MXDA·CO2 5e produced under
heating conditions generates dry CO2 (without water).
The generation of CO2 from 5e was detected under heatꢀ
ing at 103ꢀ120 °C. The generated dry CO2 should be
useful for the CO2 fixation reaction26ꢀ30 without dehydraꢀ
tion system. Thus, moistureꢀsensitive CO2 fixation using
the Grignard reaction30 was examined. When we used
H
O
H
N
N
N
O
H
H
H
H
O
H
H
O
H
O
H
H
H
H
N
N
O
N
N
H
H
y
O
O
H
O
H
O
z
2.762 Å
2.819 Å
H
N
x
H
H
Figure 3. The formation of MXDA·CO2 5e from MXDA
4e and CO2 in air. a. The reaction of MXDA 4e and air to
form MXDA·CO2 5e. b. ORTEP drawing of MXDA·CO2
5e. c. Hydrogen bonds in 5e showing the interaction beꢀ
tween 1) the carbonyl oxygen lone pair/amine proton (blue
dotted lines), and 2) the hydroxyl proton/amine lone pair
(red dotted lines). d. The hydrogen bond network in 5e
forming along both the Xꢀaxis (blue dotted lines) and the
Zꢀaxis (red dotted lines).
wet
CO2,
which
was
generated
from
(CO2)·3(MEA)·3(H2O) (1) at 120 °C (Figure 5a), the
reaction with PhMgBr (6a) or CyMgBr (6b) in THF at 0
°C gave the resulting carboxylic acids 7a,b in only 18%
and 4% yields, respectively (Figure 5b). The contained
moisture must be reacted with Grignard reagents, which
prevents the desired CO2 fixation. By contrast, the heatꢀ
ing of MXDA·CO2 5e was conducted in toluene reflux
(ca. 111 °C) because toluene is a strongly azeotropic
agent of water (Figure 5c). Despite the severe condiꢀ
tions, the carboxylic acids 7a,b were observed in very
high yields (7a: 98%, 7b: 99%: Figure 5d).
The network of hydrogen bonds was also revealed by
Xꢀray analysis (Figure 3c). The proton donor sp3 OH is
connected with the lone pair of the amine nitrogen (N:),
and NH2 proton donors are bonded with the sp2 lone
pairs of carbonyl oxygen (:O:). Figure 3d also shows the
intermolecular hydrogen bonds. Hydrogen bonds beꢀ
tween NH2 and carbonyl oxygen (:O:) form lines (Nꢀ
H···:O:···HꢀN, blue dotted lines) along the direction of
the Xꢀaxis. In addition, hydrogen bonds between OH
and amine nitrogens (OꢀH···:N, red dotted lines) act as
bridges in the direction of the Zꢀaxis. Thus, the forꢀ
mation of the elaborate hydrogen bond network might
prompt a powerful organization. Next, the relationship
In summary, the introduction of hydrophobic aryl
moieties into alkylamines enhanced the selectivity of
CO2 absorbents without hygroscopic properties from the
air. This property should be useful for the further design
of CO2 absorbents not only for DAC but also for CCS.
Moreover, we succeeded in discovering unprecedented
CO2 absorbents without hydration, MXDA 4e, OXDA
4f, and PXDA 4g. Notably, MXDA 4e had a superior
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 4 of 7
finagaki@p.kanazawaꢀu.ac.jp.
CO2 absorption ability, and the robust MXDA·CO2 5e
1
2
3
4
5
6
7
8
selfꢀassembled into a structure similar to a reverse lipid
bilayer even in water. A normal lipid bilayer31 exposes
both hydrophilic faces to the water, while the hydrophoꢀ
bic alkyl chains are gathered in the middle. This behavꢀ
iour is reasonable in terms of the affinity between the
hydrophilic sites and water. In contrast, the hydrophobic
phenyl group of selfꢀassembled MXDA·CO2 5e faces
the water or moisture. The reason remains uncertain.
However, the two hydrophobic layers clearly protect the
middle carbamic acid from hydration. Furthermore, the
generation of dry CO2 from MXDA·CO2 5e was accomꢀ
plished under heating, which enabled us to use atmosꢀ
pheric CO2 in moistureꢀsensitive CO2ꢀfixation by the
Grignard reaction without any dewatering processes. As
various types of CO2 fixation methods26ꢀ30 under 1 atm
of CO2 have been reported, the dry CO2 collected from
MXDA·CO2 5e has great potential for use as a C1ꢀunit
of chemical synthesis. Hydrated CO2 absorbents such as
(CO2)·3(MEA)·3(H2O) (1) require extra thermal energy
to liberate H2O as moisture, whereas anhydrous
MXDA·CO2 5e can avoid the water evaporation step,
which should lead to lower energy consumption. In othꢀ
er words, waterproof CO2 absorbents should be a highly
valuable candidate for CO2ꢀcapture and release projects.
Planning for the construction of an effective CO2 capꢀ
ture/emission system on a larger scale is currently onꢀ
going.
Funding Sources
No competing financial interests have been declared.
ACKNOWLEDGMENT
We are grateful for the support of a GrantꢀinꢀAid for Scienꢀ
tific Research from the Ministry of Education, Culture,
Sports, Science, and Technology (Japan). We thank Prof.
Dr. Motohiro Mizuno of Kanazawa University for solid
13CꢀNMR analysis of MXDA·CO2, OXDA·CO2, and
PXDA·CO2.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
REFERENCES
(1) Reiner, D. M. Nat. Energy. 2016, 1, 1ꢀ7.
(2) Scott, V.; Gilfillan, S.; Markusson, N.; Chalmers, H.; Haszeldꢀ
ine, R. S. Nat. Clim. Change, 2013, 3, 105ꢀ111.
(3) Haszeldine, R. S. Science 2009, 25, 1647ꢀ1652.
(4) IPCC 2014. Climate Change 2014: Synthesis Report. Contribu-
tion of Working Groups I, II and III to the Fifth Assessment Report of
the Intergovernmental Panel on Climate Change; The Core Writing
Team; Pachauri, R. K.; Meyer, L. A., Eds.; IPCC: Geneva, Switzerꢀ
land, 2014; pp 151.
(5) IPCC, 2014. Climate Change 2014: Mitigation of Climate
Change. Contribution of Working Group III to the Fifth Assessment
Report of the Intergovernmental Panel on Climate Change; Edenhoꢀ
fer, O.; PichsꢀMadruga, R.; Sokona, Y.; Farahani, E.; Kadner, S.;
Seyboth, K.; Adler, A.; Baum, I.; Brunner, S.; Eickemeier, P.;
Kriemann, B.; Savolainen, J.; Schlömer, S.; von Stechow, C.; Zwickꢀ
el, T.; Minx, J. C., Eds.; Cambridge University Press: Cambridge,
United Kingdom and New York, USA, 2014.
(6) IPCC, 2013: Climate Change 2013: The Physical Science Ba-
sis. Contribution of Working Group I to the Fifth Assessment Report
of the Intergovernmental Panel on Climate Change; Stocker, T. F.;
Qin, D.; Plattner, G.ꢀK.; Tignor, M.; Allen, S. K.; Boschung, J.;
Nauels, A.; Xia, Y.; Bex, V.; Midgley, P. M. Eds.; Cambridge Uniꢀ
versity Press: Cambridge, United Kingdom and New York, USA,
2013; pp 1535.
(7) Boden, T. A.; Marland, G.; Andres, R. J. National CO2 Emis-
sions from Fossil-Fuel Burning, Cement Manufacture, and Gas Flar-
ing: 1751-2011 [On line]; Carbon Dioxide Information Analysis Cenꢀ
ter, Oak Ridge National Laboratory, U.S. Department of Energy, Oak
Ridge, Tenn., USA. doi 10.3334/CDIAC/00001_V2015 (accessed
Mar 1, 2017).
(8) SanzꢀPérez, E. S.; Murdock, C. R.; Didas, S A.; Jones, C. W.
Chem. Rev. 2016, 116, 11840–11876 .
(9) Goeppert, A.; Czaun, M.; Surya Prakash, G. K.; Olah, G. A.
Energy Environ. Sci. 2012, 5, 7833– 7853.
(10) Socolow, R.; Desmond, M.; Aines, R.; Blackstock, J.; Bolꢀ
land, O.; Kaarsberg, T.; Lewis, N.; Mazzotti, M.; Peffer, A.; Sawayer,
K.; Siirola, J. Smit, B.; Wilcox, J. Direct Air Caputure of CO2 with
Chemicals; A Technology Assessment for the APS Panel on Public
Affairs. American Physical Society: Maryland, USA, 2011.
(11) Chichilnisky, G.; Eisenberger, P. M. Nature 2009, 459, 1053.
(12) Keith, D. W. Science 2009, 325, 1654–1655.
Figure 5. Comparison of CO2 collection/fixation systems
between MEA and MXDA using the Grignard reaction. a.
CO2 absorption/generation system using MEA under air. b.
Grignard reaction with wet CO2 derived from
(CO2)·3(MEA)·3(H2O) (1). c. CO2 absorption/generation
system using MXDA 4e in air. d. Grignard reaction with
dry CO2 derived from MXDA·CO2 5e (toluene, reflux).
(13) Pielke, R., Jr. Nat. Geosci. 2009, 2, 811.
(14) Dessler, A. Nat. Geosci. 2009, 2, 811.
ASSOCIATED CONTENT
(15) Inagaki, F.; Okada, Y.; Matsumoto, C.; Yamada, M.; Nakazaꢀ
wa, K.; Mukai, C. Chem. Pharm. Bull. 2016, 64, 8ꢀ13.
(16) Kumar, A.; Madden, D. G.; Lusi, M.; Chen, K. J.; Daniels, E.
A.; Curtin, T.; Perry, J. J.; Zaworotko, M. J. Angew. Chem., Int. Ed.
2015, 54, 14372–14377.
(17) Shekhah, O.; Belmabkhout, Y.; Chen, Z.; Guillerm, V.;
Cairns, A.; Adil, K.; Eddaoudi, M. Nat. Commun. 2014, 5, 4228.
(18) Liu, J.; Thallapally, P. K.; McGrail, B. P.; Brown, D. R.; Liu,
J. Chem. Soc. Rev. 2012, 41, 2308– 2322.
The Supporting Information is available free of charge on
the ACS Publications website.
Experimental procedures and characterizations (PDF)
Data for MXDA·CO2 (CIF)
AUTHOR INFORMATION
Corresponding Author
(19) Farha, O. K.; Hupp, J. T. Acc. Chem. Res. 2010, 43, 1166–
1175.
ACS Paragon Plus Environment

Page 5 of 7
Journal of the American Chemical Society
(20) Zhao, D.; Timmons, D. J.; Yuan, D.; Zhou, H.ꢀC. Acc. Chem.
Res. 2011, 44, 123–133.
(21) Tanabe, K. K.; Cohen, S. M. Chem. Soc. Rev. 2011, 40, 498–
519.
(22) Nishi, T.; Abe, Y., J. Synth. Org. Chem. Jpn. 1969, 27, 458ꢀ
460.
(23) Pinto, M. L.; Mafra, L.; Guil, J. M.; Pires, J.; Rocha, J.
Chem. Mater. 2011, 23, 1387ꢀ1395.
(24) Moore, J. K.; SakwaꢀNovak, M. A.; Chaikittisilp, W.; Meꢀ
hta,A. K.; Conradi, M. S.; Jones, C. W.; Hayes, S. E. Environ. Sci.
Technol. 2015, 49, 13684−13691.
(26) Liu, Q.; Wu, L.; Jackstell, R.; Beller, M. Nature Commun.
2015, 6, 1ꢀ15.
1
2
3
4
5
6
7
8
(27) Cokoja, M.; Bruckmeier, C.; Rieger, B.; Herrmann, W. A.;
Kühn, F. E. Angew. Chem. Int. Ed. 2011, 50, 8510ꢀ8537.
(28) Correa, A.; Martín, R. Angew. Chem. Int. Ed. 2009, 48, 6201ꢀ
6204.
(29) Sakakura, T.; Choi, J.ꢀC.; Yasuda, H. Chem. Rev. 2007, 107,
2365ꢀ2387.
(30) Grignard, V. Ann. Chim. 1901, 24, 433–490.
(31) Mashaghi, A.; PartoviꢀAzar, P.; Jadidi, T.; Nafari, N.; Maass,
P.; Tabar, M. R. R.; Bonn, M.; Bakker, H. J. Chem. Phys. 2012, 136,
114709.
9
(25) Ren, Q.; Xu, Haijin.; Yu, Q.; Zhu, S. Ind. Eng. Chem.
Res. 2015, 54, 11056ꢀ11064.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 6 of 7
Table of contents
1
2
3
air
4
5
6
7
N2
CO2
NH2
MXDA
NH2
dry CO2
O2 H2O
etc.
(NOT wet)
rt
103~120 °C
hydrophobic
layer
8
9
O
NH
H
N
H
H
H
C
O
hydrophilic
layer
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
O
C
H
H
N
HN
O
hydrophobic
layer
MXDA—CO2
waterproof
6
ACS Paragon Plus Environment

Page 7 of 7
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
Figure 1.ꢀ
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
a
O
H2O
R
R
O
R
O
NH2
N
+ CO2
NH
OH
R'
OH
R'
R'
B
A
R NH
R'
R NH
R'
O
R
H2O
O
R
R
O
NH2
NH
H2N
2 O
O
O
N R
R'
R'
R'
C
D
O
3
R'
X
H2O
b
c
O
hydrophobic
group
R NH
H3N R
3 O
O
N
H
R NH3
R
2
?
NH2
Me
NH2
NH2
N
H
MeO
Benzylamine Phenetylamine N-Methylbenzylamine p-Methoxybenzylamine
(BZA, 4a)
(PEA, 4b)
(NMBZA, 4c)
(PMBZA, 4d)
NH2
NH2
NH2
NH2
NH2
NH2
m-xylylenediamine p-xylylenediamine o-xylylenediamine
(MXDA, 4e) (PXDA, 4f)
(OXDA, 4g)
ACS Paragon Plus Environment