Reusable amine-based structural motifs for green house gas (CO2) fixation

Article abstract of DOI:10.1021/ol301241k

A series of compounds with an amine based structural motif (ASM) have been synthesized for efficient atmospheric CO₂ fixation. The H-bonded ASM-bicarbonate complexes were formed with an in situ generated HCO ₃^- ion. The complexes have been characterized by IR, ¹³C NMR, and X-ray single-crystal structural analysis. ASM-bicarbonate salts have been converted to pure ASMs in quantitative yield under mild conditions for recycling processes.

Full text of DOI:10.1021/ol301241k

ORGANIC
LETTERS
2012
Vol. 14, No. 13
3244–3247
Reusable Amine-Based Structural Motifs
for Green House Gas (CO2) Fixation
Sasanka Dalapati,† Sankar Jana,† Rajat Saha,‡ Md. Akhtarul Alam,§ and
Nikhil Guchhait*,†
Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700 009,
India, Department of Physics, Jadavpur University, Jadavpur, Kolkata 700 032, India,
and Department of Chemistry, Aliah University, Sector-V, Saltlake, Kolkata 700 091,
India
nguchhait@yahoo.com
Received March 30, 2012
ABSTRACT
A series of compounds with an amine based structural motif (ASM) have been synthesized for efficient atmospheric CO2 fixation. The H-bonded
ASMꢀbicarbonate complexes were formed with an in situ generated HCO3ꢀ ion. The complexes have been characterized by IR, 13C NMR, and
X-ray single-crystal structural analysis. ASMꢀbicarbonate salts have been converted to pure ASMs in quantitative yield under mild conditions for
recycling processes.
Carbon dioxide is a critical green house gas that is
responsible for global warming. The last few decades have
witnessed enormous attention to minimize the excess CO2
in air, and attempts have been made to measure the
quantity of CO2 uptakes by various methods.1 Different
methods were developed for capturing aerial carbon dioxide
to combat the problem of global warming.2 Among
different methods, porous materials consisting of metalꢀ
organic frameworks (MOFs) have been reported with a
remarkable CO2 adsorption capability.3 Most MOFs uti-
lized for these applications are very expensive and moisture
sensitive. One such example is the MOFs composed of
(4) (a) Kong, L.-Y.; Zhu, H.-F.; Huang, Y.-Q.; Okamura, T.; Lu,
X. H.; Song, Y.; Liu, G.-X.; Sun, W.-Y.; Ueyama, N. Inorg. Chem. 2006,
45, 8098. (b) Kong, L. Y.; Zhang, Z. H.; Zhu, H. F.; Kawaguchi, H.;
Okamura, T.; Doi, M.; Chu, Q.; Sun, W. Y.; Ueyama, N. Angew. Chem.,
Int. Ed. 2005, 44, 4352. (c) Mukherjee, P.; Drew, M. G. B.; Estrader, M.;
Ghosh, A. Inorg. Chem. 2008, 47, 7784.
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J. Am. Chem. Soc. 2011, 133, 6650. (b) Mitra, T.; Wu, X.; Clowes, R.;
Jones, J. T. A.; Jelfs, K. E.; Adams, D. J.; Trewin, A.; Bacsa, J.; Steiner,
A.; Cooper, A. I. Chem.;Eur. J. 2011, 17, 10235. (c) Edwards, P. R.;
Hiscock, J. R.; Gale, P. A.; Light, M. E. Org. Biomol. Chem. 2010, 8, 100.
(d) Hampe, E. M.; Rudkevich, D. M. Chem. Commun. 2002, 1450.
† University of Calcutta.
‡ Jadavpur University.
§ Aliah University.
(1) Env. Sci. Technol. March 1, 2003, 91A.
(2) Perry, R.; O’Brien, M. Energy Fuels 2011, 25, 1906.
(3) (a) Gassensmith, J. J.; Furukawa, H.; Smaldone, R. A.; Forgan,
R. S.; Botros, Y. Y.; Yaghi, O. M.; Stoddart, J. F. J. Am. Chem. Soc.
~ ~
´
2011, 133, 15312. (b) Garcıa-Espana, E.; Gavina, P.; Latorre, J.;
Soriano, C.; Verdejo, B. J. Am. Chem. Soc. 2004, 126, 5082. (c) Gao,
G.; Li, F.; Xu, L.; Liu, X.; Yang, Y. J. Am. Chem. Soc. 2008, 130, 10838.
r
10.1021/ol301241k
Published on Web 06/13/2012
2012 American Chemical Society

transition-metal complexes which can absorb CO2 from the
air and then convert the gas into bicarbonate or carbonate
salts.4 At present, aminodisiloxanes,2 green- MOFs,3a neutral
organic cages,5a,b various amine solutions,5c,d aminosilicas,6
ionic liquids,7 etc. have been commonly used as efficient CO2
absorbents from the flue gases via a chemical reaction
between the amines and CO2 molecules under variable
conditions. However, high energy is needed for recovering
these amines for the recycling process.5c,d,6,7
Scheme 1. Chemical Structures of ASMs 1ꢀ3
An alternative solution to reduce the excess atmospheric
CO2 is to utilize amine-based structural motifs (ASMs)
because ASMs act as an effective reusable aerial carbon
dioxide absorbent. Only a few receptors were reported as
an efficient green house gas (CO2) fixation in the basic
medium [in the presence of TBOH (n-Bu4NþOHꢀ) or
TBAF (n-Bu4NþFꢀ)], where CO2 is converted to bicarbo-
nate/carbonate and can form a strongly H-bonded receptor-
bicarbonate/carbonate complex. For example, simple
naphthalimide-basedreceptorshaving aromaticsecondary
amine are capable for colorimetric sensing of fluoride ion,
and this has been used for aerial carbon dioxide fixation in
presence of activating reagent TBAF or TBOH in DMSO
solvent.8 The urea-based receptor is also capable for atmo-
spheric carbon dioxide fixation in the presence of TBAF in
acetonitrile solvent.9 Recently, a reusable neutral receptor
was reported for efficient fixation of atmospheric CO2 by
carbonate complex formation in the presence of TBOH in
DMSO solvent.10 Among these developments, a systema-
tic study with primary amine-based compounds suitable
for green house gas fixation has not been investigated.
In this endeavor, we have clearly outlined a systematic
study toward green house gas fixation by primary amine-
based synthetic compounds and theirreusuability. Inorder
to produce an efficient green house gas (CO2) absorbent at
room temperature and atmospheric pressure, we have
designed and synthesized simple neutral organic molecules
of low molecular mass from commercially available simple
starting materials (PNOPDA, Supporting Information).
We have also examined the indispensable role of ASMs
toward green house gas fixation processes. After the action of
activating reagent TBAF, the receptors are capable of efficient
aerial CO2 fixation and form H-bonded bicarbonate com-
plexes (like {n-Bu4Nþ[1 HCO3]ꢀ}, {n-Bu4Nþ[2 HCO3]ꢀ},
carbon dioxide as was reported in previous reports.5c,d,6,7 To
the best of our knowledge, we have synthesized amine-based
structural motifs (ASMs, Scheme 1) for efficient uptake of
atmospheric carbon dioxide without the formation of carba-
mate salts. The ASMꢀbicarbonate complexes are formed
with good quantitative yield and can be recovered at room
temperature for reusable purposes.10
Compounds 1ꢀ3 (Scheme 1) have been synthesized
according to our published procedure.11 Detailed synthetic
schemes and characterizations are provided in the Supporting
Information. Our preliminary investigation on ASMs has been
done in the presence of various anions (∼2 equiv) in acetoni-
trile solvent. These solutions were used for atmospheric carbon
dioxide fixation at room temperature. Solutions were placed
under ether diffusion systems for ∼1ꢀ2 days. Reddish sticky
materials were obtained and separated from Fꢀ, Clꢀ, and
AcOꢀ anion-containing solutions. These sticky materials were
easily separated from the binary solution system (CH3CN/
Et2O) by simply decanting the solvent mixture and evaporat-
ing under air. The sticky material was then dissolved in
acetonitrile solvent and placed under an ether diffusion system.
Unfortunately, after several trials Clꢀ and AcOꢀ anion-con-
taining systems could not produce crystals even after a
prolonged time. However, after a considerable time (∼2 days),
fluoride-containing compounds (1ꢀ3) can easily form
air-stable red crystals ({n-Bu4Nþ[1 HCO3]ꢀ}, {n-Bu4Nþ-
3
[2 HCO3]ꢀ}, and {n-Bu4Nþ[3 HCO3]ꢀ}) with high quan-
3
3
titative yields (Table S1, Supporting Information). These
crystals were suitable for single-crystal X-ray diffraction
analysis.12ꢀ14 ASMꢀbicarbonate hydrogen-bonded com-
plex formation occurs by capturing in situ generated
3ꢀ
3
and {n-Bu4Nþ[3 HCO3] }). These bicarbonate complexes
3
were characterized by X-ray single-crystal diffraction, IR, and
13C NMR analysis. We have also verified the possibilities of
carbon dioxide fixation in the presence of other anions such
as Clꢀ, Brꢀ, Iꢀ, AcOꢀ, NO3ꢀ, ClO4ꢀ, NO2ꢀ, HSO3ꢀ, and
HSO4ꢀ. It is important to note that our amine-based recep-
tors never form carbamate salts in the presence of atmospheric
ꢀ
HCO3 ions. The presence of bicarbonate in all crystals
(11) Dalapati, S.; Alam., Md. A.; Jana, S.; Saha, R.; Biswas, S.;
Guchhait, N. ChemPlusChem 2012, 77, 93.
ꢀ
(12) Crystallographic data for 1 HCO3ꢀ, 2 HCO3ꢀ, and 3 HCO3
3
3
3
have been deposited in the Cambridge Crystallographic Data Centre as
supplementary publication nos. CCDC 860075, 860076, and 860077,
respectively.
(6) Hicks, J. C.; Drese, J. H.; Fauth, D. J.; Gray, M. L.; Qi, G.; Jones,
C. W. J. Am. Chem. Soc. 2008, 130, 2902.
(7) (a) Camper, D.; Bara, J. E.; Gin, D. L.; Noble, R. D. Ind. Eng.
Chem. Res. 2008, 47, 8496. (b) Bates, E. D.; Mayton, R. D.; Ntai, I.;
Davis, J. H., Jr. J. Am. Chem. Soc. 2002, 124, 926.
(13) SAINT, version 6.02; SADABS, version 2.03; Bruker AXS, Inc.:
Madison, WI, 2002.
(14) (a) Sheldrick, G. M. SHELXS 97, Program for Structure Solu-
(8) (a) Gao, J.; He, L.-N.; Miao, C.-X.; Chanfreau, S. Tetrahedron.
2010, 66, 4063. (b) Edwards, P. R.; Hiscock, J. R.; Gale, P. A. Tetra-
hedron. Lett. 2009, 50, 4922.
€
tion, University of Gottingen, Germany, 1997. (b) Sheldrick, G. M.
SHELXL 97, Program for Crystal Structure Refinement, University of
Gottingen, Germany, 1997. (c) Spek, A. L. PLATON, Molecular Geometry
Program. J. Appl. Crystallogr. 2003, 36, 7. (d) Farrugia, L. J. J. Appl.
Crystallogr. 1997, 30, 565. (e) Farrugia, L. J. J. Appl. Crystallogr. 1999,
32, 837.
€
ꢀ
(9) Boiocchi, M.; Del Boca, L.; Gomez, D. E.; Fabbrizzi, L.; Licchelli,
M.; Monzani, E. J. Am. Chem. Soc. 2004, 126, 16507.
(10) Ravikumar, I.; Ghosh, P. Chem Commun. 2010, 46, 1082.
Org. Lett., Vol. 14, No. 13, 2012
3245

Figure 1. Bicarbonate dimer (top); 1ꢀbicarbonate adduct formed
through aerial CO2 fixation (bottom).
Figure 2. Bicarbonate dimer (top); 2ꢀbicarbonate adduct formed
during aerial CO2 fixation process (bottom).
ensures the obvious conversion of atmospheric CO2 to
HCO3ꢀ in the presence of TBAF.9
Compound 2 is structurally similar to that of compound 1.
We may expect that compound 2 could form similar type
Single-crystal X-ray diffraction data reveal that bicarbonate-
containing complexes are structurally similar due to the
presence of ASMs. The crystal structure analysis shows that
1 HCO3ꢀ, 2 HCO3ꢀ, and 3 HCO3ꢀ complexes are crystal-
of bicarbonate complex ({n-Bu4Nþ[2 HCO3]ꢀ} as that
3
of 1 {n-Bu4Nþ[1 HCO3]ꢀ}) through aerial CO2 fixation.
3
Most importantly, it was found that compound 2 also
forms similar type of bicarbonate complex as that of 1
(Figure 2, distances N1(ꢀH1B) O3 2.913, N2 O3
3
3
3
lized in the space groups P21/n, P-1, and P-1, respectively.
Moreover, in each ASMꢀbicarbonate complex one bicarbo-
nate anion is engaged to form a bifurcated hydrogen ꢀbond
with two amine hydrogens. Each ASM-bound HCO3 ion
donates as well as accepts hydrogens from another ASM-
bound HCO3ꢀ ion. This gives rise to a dimer or a polymer by
means of other interactions, which again depends on their
variable molecular backbones. The X-ray single-crystal struc-
ture descriptions (ORTEP: Figures S1ꢀS3, Supporting
Information) of the complexes are summarized in Table S2
(Supporting Information). Relevant geometrical parameters
correspond to H-bonding interactions in all crystalline com-
plex salts ({n-Bu4Nþ[1 HCO3]ꢀ}, {n-Bu4Nþ[2 HCO3]ꢀ},
3 3 3
3 3 3
2.939, O1 O2 2.582, N1(ꢀH1A) O3 3.059, and
3 3 3
3 3 3
N1(ꢀH1A) O2 3.196 A). Only hydrogen bond dis-
3 3 3
tances are different (Table S3, Supporting Information)
due to their minor structural differences. Interestingly, the
hydrogen atoms of amine are found to be suitable for
H-bonding interaction withbicarbonate anion through the
formation of strong bifurcated adduct. In the case of
compound 3, a comparatively large aromatic subunit
was attached with the basic backbone in order to examine
the indispensable role of ASMs toward atmospheric car-
bon dioxide fixation. Compound 3 similarly forms a
bicarbonate complex through aerial carbon dioxide fixa-
3
3
and {n-Bu4Nþ[3 HCO3]ꢀ}) are presented in Table S3
3
(Supporting Information).
The smallest molecular unit (compound 1) efficiently
absorbs atmospheric CO2 and forms an H-bonded bicar-
tion. In the structure of 3 HCO3ꢀ complex (Figure 3), one
3
bicarbonate anion (O3 atom) is bound with two amine
nitrogen atoms (N1 and N2 atoms) through a similar type
of bifurcated H-bond (Table S3 (Supporting Information),
distances N1(ꢀH1B) O3 2.879 and N2 O3 3.009 A).
bonate complex ({n-Bu4Nþ[1 HCO3]ꢀ}). The structure of
3
the 1 HCO3ꢀ complex shows that compound 1 is bound to
3
3 3 3
3 3 3
bicarbonate anion through strꢀong H-bonding interactions,
where the O3 atom of HCO3 anion is bound through a
bifurcated H-bond with two amine (N1 and N2) hydrogen
atoms (Figure 1, Table S3 (Supporting Information),
distances N1(ꢀH1B) O3 2.889 and N2 O3 2.971 A).
Each 3 HCO3ꢀ unit donates and accepts hydrogens from
3
ꢀ
another 3 HCO3 unit and generates a dimer (Figure 3,
distance O1 O2 2.607 A) and polymer (Figure 3, dis-
3
3 3 3
tance N1(ꢀH1A) O3 3.074 and N1(ꢀH1A) O2
3 3 3
ꢀ3 3 3
ꢀ
3.316 A). In contrast to 1 HCO3 and 2 HCO3 com-
3 3 3
3 3 3
3
3
ꢀ
Each 1-bound HCO3 ion donates and accepts hydro-
gens from another 1-bound HCO3ꢀ ion and forms a dimer
(Figure 1, distance O1 O2 2.586 A). Each dimer is then
plexes, here 1D polymer is extended to supramolecular 2D
sheet through π-interactions (Figures S4 and S5, Table S4,
Supporting Information).
3 3 3
connected with another dimer via H-bonding interactions
between the aromatic primary amine (N1 atom) and
bicarbonate anion (O3 atom). This generates a supramolecu-
The presence of bicarbonate anions in all crystalline
complexes has been further confirmed by 13C NMR
measurement (Figure S6, Supporting Information). The
appearance of a new peak (δ) at 159ꢀ160 ppm (compared
lar polymer (Figure 1, distance N1(ꢀH1A) O3 2.970 A).
3246
3 3 3
Org. Lett., Vol. 14, No. 13, 2012

Scheme 2. Aerial CO2 Fixation Cycle by ASMs
* Bicarbonate complexes are {n-Bu4Nþ[1 HCO3]ꢀ}, {n-Bu4Nþ-
3
[2 HCO3]ꢀ}, and {n-Bu4Nþ[3 .HCO3]ꢀ}.
Figure 3. Bicarbonate dimer (top); 3ꢀbicarbonate adduct formed
3
3
during aerial CO2 fixation process (bottom).
The purity of recovered ASMs has been checked by IR,
NMR, and mass spectral analysis.
with ASMs itself, δ <150 ppm) in all complexes ensures
the presence of bicarbonate anion in each complex.
Further information regarding the existence of bicarbo-
nate anions in all complexes was obtained from solid-state
IR spectral measurements (Figures S7ꢀS9, Supporting
Information). The presence of new band (compared with
ASMs itself) at ∼1680ꢀ1702 cmꢀ1 in all complexes in-
dicates the presence of H-bonded bicarbonate anion.11
Minor spectral differences (13C NMR and IR) in the
bicarbonate complexes are the reflections of their negligi-
ble X-ray single-crystal structural alternations.
In conclusion, we have established a potential chemical
route for selective atmospheric CO2 fixation (Scheme 2).
To achieve this, we have synthesized some predesigned
ASMs of very low molecular mass with high CO2 fixation
ability. The formation of ASMꢀbicarbonate compl-
exes ({n-Bu4Nþ[1 HCO3]ꢀ}, {n-Bu4Nþ[2 HCO3]ꢀ}, and
3
3
{n-Bu4Nþ[3 HCO3]ꢀ}) and regeneration of ASMs under
3
mild conditions clearly establishes the potential of rever-
sible binding. Using this fundamental concept and by
adopting proper methods it is possible to reduce the green
house gas (CO2) as well as global warming by efficient CO2
absorbent (having ASMs) on a large scale.
For the commercialization ofASMs for the CO2 fixation
cycle, we have investigated its reusuability. To reuse
the ASMs for further CO2 fixation processes, we have
Acknowledgment. This work is supported by grants
from DST, India (Project No. SR/S1/PC/26/2008), to N.G.
S.D. and S.J. acknowledge UGC for fellowships. We are
thankful to Dr. J. L. Mynar of UC, Berkeley, for editing
the manuscript.
treated the bicarbonate complexes ({n-Bu4Nþ[1 HCO3]ꢀ},
3
{n-Bu4Nþ[2 HCO3]ꢀ}, and {n-Bu4Nþ[3 HCO3]ꢀ}) with
3
3
MeOH/H2O solvent mixture (1:9 v/v). The neutral un-
complexed AꢀSMs are insoluble in water, whereas the n-
Bu4NþHCO3 salt is highly soluble in water. Therefore,
the ASMꢀbicarbonate complexes were immediately
crashed out under the binary solvent mixture (MeOH/
H2O), and the ASM residues were separated out from the
solution, filtered off, and washed with distilled water. Pure
ASMs 1ꢀ3 were obtained in almost quantitative yields
(Table S1, Supporting Information) and could be reused
for further carbon dioxide fixation processes (Scheme 2).
Supporting Information Available. Material and meth-
ods, synthesis and characterization, experimental details,
Figures S1ꢀS13, and Tables S1ꢀS4. This material is
available free of charge via the Internet at http://pubs.
acs.org.
The authors declare no competing financial interest.
Org. Lett., Vol. 14, No. 13, 2012
3247