tmp5B8E TMP
tmp5B8E TMP
tmp5B8E TMP
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DOI: 10.1039/c5ta00587f
K/1 bar. The CPP exhibited a BrunauerEmmettTeller (BET) surface area of 579 m2 g1 and high
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thermal stability up to 500 C, thus showing good potential for CO2 capture.
1. Introduction
CO2 capture is one of the important challenges that, when
solved, would enable the usage of fossil fuels with lower CO2
emissions. Highly selective CO2 adsorption on porous organic
polymers (POPs)118 is an eective alternative for CO2 capture
over conventional amine scrubbers. To ensure high CO2
capture, the building blocks for these porous polymers should
include functional groups, such as NO2, OH, COOH, SO3H,
arylamines, and heterocyclic nitrogen atoms to enhance CO2
anities through O]C]O(d)H(d+)O and H2N(d)C(d+)O2
interactions.19 Porous polymers containing CO2 binding functionalities have the advantage that they can be easily regenerated without applying heat because no chemisorption is
involved.
In the past decade, the Cu(I)-catalyzed click reaction
between alkynes and azides has been widely used in materials
science and biology.20,21 A few porous polymers were prepared
using the click reaction in part due to the advantage of high
thermal and chemical stabilities of the triazole ring, mild
reaction conditions, and the absence of by-products.2224
Recently, various porous organic materials such as hypercrosslinked polymers (HCPs), polymers of intrinsic microporosity (PIMs), conjugated microporous polymers (CMPs),
porous organic frameworks (POFs), benzimidazole-linked
polymers (BILPs), porous polymer networks (PPNs), and covalent organic polymers (COPs) have received signicant attention
due to their potential applications in gas storage and separations.118 Unlike metalorganic frameworks (MOFs)2528 and
covalent organic frameworks (COFs),2937 POPs are amorphous,
a
but have tunable pore sizes and surface areas similar to those of
MOFs and COFs. They can be prepared under easily controllable
reaction conditions, are amenable to scale-up preparation, and
exhibit high stability towards moisture, much better than the
corresponding MOFs and COFs.
To the best of our knowledge, a phthalocyanine-based
porous polymer has never been reported using click polymerization or any other method, and tested for selective CO2
adsorption studies. Here we report the synthesis of a partially
crystalline phthalocyanine porous polymer, CPP, based on a
click reaction between a phthalocyanine-tetraazide (1) and
bisamine diethynylbenzene (2), see Scheme 1. We investigated
the eect of nitrogen-rich functional groups (amine and triazole) inside the pore surfaces. The data reveal high CO2
adsorption (15.7 wt%), and also high CO2/N2 (94) and CO2/CH4
(12.8) selectivities.
2.
Experimental methods
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3.
Bruker benchtop Microex model using matrix trihydroxyanthracene. In order to determine pore textural properties
including the specic BrunauerEmmetTeller (BET) surface
area, pore volume and pore size distribution, nitrogen adsorption and desorption isotherms on CPP at 77 K, 273 K, and 298 K
were measured on an ASAP-2020 adsorption apparatus (Micromeritics). The samples were degassed in situ at 150 C with a
heating rate of 3 C min1 under vacuum (0.0001 mm Hg) for
12 h before nitrogen adsorption measurements in order to
ensure the micro-channels in the structure were guest-free. The
BrunauerEmmettTeller (BET) method was utilized to calculate the specic surface areas by using the non-local density
functional theory (NLDFT) model, and the pore volumes were
derived from the sorption curves. Thermogravimetric analyses
between 30800 C were conducted on a Mettler-Toledo thermogravimetric analyzer under a N2 atmosphere using a 5 C
min1 ramp time.
Synthesis of tetraazidophthalocyanine Co(II)
Tetraaminophthalocyanine Co(II) (200 mg, 0.3 mmol) was dissolved in a 2 N HCl (10 mL), cooled to 0 C and a solution of
NaNO2 (93 mg, 1.35 mmol) in water (2 mL) was then added
drop-wise into the cooled solution. The reaction mixture was
The CPP polymer was synthesized using the Cu(I) catalyzed 1,3dipolar azidealkyne cycloaddition (CuAAC) reaction (Scheme
1). Triazole linkages were easily formed by condensation of
acetylene and azide groups. During the reaction, the color
turned from green to colorless, indicating the formation of the
phthalocyanine porous polymer. Green powders precipitated,
which were collected by ltration. Soxhlet extraction with water,
acetone, and dichloromethane were used to remove lowmolecular weight by-products and inorganic salts, respectively.
The CPP was insoluble in water and common organic solvents
such as acetone, hexanes, ethanol, tetrahydrofuran, DMSO, and
N,N0 -dimethylformamide.
In order to verify the chemical connectivity and crystallinity
of the CPP, Fourier transform infrared spectroscopy (FT-IR),
and 13C NMR cross polarization magic angle spinning
(CP/MAS), and powder X-ray diraction analyses were performed. The formation of triazole linkages were conrmed by
the FT-IR spectra (Fig. 1A). The absorption peaks for the acetylene bonds at 3281 cm1 disappear, while new stretches are
observed at 1615 cm1 for the N]N stretch and a weak band
at 2923 cm1 for the C]CH stretch. These conrmed the
formation of the triazole bonds. The peak intensity at
2109 cm1 for the azide moieties was highly attenuated. A broad
band observed in the 33003500 cm1 region was attributed to
the presence of primary amine groups in the CPP. The 13C
CP/MAS NMR spectrum (Fig. 1B) showed the characteristic
peaks at 153 ppm which can be attributed to the carbon atom of
the triazoleacetylene linkages. The peaks in the range of
100150 ppm originate from the carbons of the phthalocyanine
units. The results obtained from FT-IR and CP/MAS NMR
conrm that the molecular building blocks are linked to each
other via the formation of triazole linkages.
Powder X-ray diraction (Cu Ka radiation) was employed to
examine the crystallinity of the CPP (Fig. 2). The diraction
pattern displays a low intensity diraction peak at 2q 9 , and
another low intensity peak at 26 , reecting the partially
Paper
Fig. 3
Table 1
Fig. 2
crystalline nature of CPP. CPP was constructed from a phthalocyanine macrocycle and a small and linear bisamine diethynylbenzene to reduce interpenetration. The porosity parameters of
CPP were studied by N2 adsorption measurements (Fig. 3). The
adsorption curves clearly indicated that CPP is microporous
and exhibits a type-I reversible adsorption isotherm and the
polymer showed selective adsorption towards CO2 over N2
and CH4 (Table 1). The BrunauerEmmettTeller (BET) surface
area was 579 m2 g1 and the total pore volume was 0.71 cm3 g1.
A relatively small hystereses in the CO2 uptake data indicates
weak interactions between the adsorbent and CO2 molecules.
These weak interactions are crucial for the regeneration of the
CPP without applying external energy (heat). The pore size
Polymer
Selectivity
CO2 (wt%)
CH4 (wt%)
CPP
94 (CO2/N2)
12.8 (CO2/CH4)
15.7 (273 K)
10 (298 K)
1.78 (273 K)
0.95 (298 K)
Paper
Fig. 6
Fig. 5
Acknowledgements
This work was generously supported by NSF grant DMR1205302 (PREM program), and the Robert A. Welch Foundation,
grant # AH-0033.
References
1 N. B. McKeown and P. M. Budd, Chem. Soc. Rev., 2006, 35,
675.
2 M. P. Tsyurupa and V. A. Davankov, React. Funct. Polym.,
2006, 66, 768.
3 J.-X. Jiang, F. Su, H. Niu, C. D. Wood, N. L. Campbell,
Y. Z. Khimyak and A. I. Cooper, Chem. Commun., 2008, 486.
4 O. K. Farha, Y.-S. Bae, B. G. Hauser, A. M. Spokoyny,
R. Q. Snurr, C. A. Mirkin and J. T. Hupp, Chem. Commun.,
2010, 46, 1056.
5 P. Pandey, A. P. Katsoulidis, I. Eryazici, Y. Wu,
M. G. Kanatzidis and S. T. Nguyen, Chem. Mater., 2010, 22,
4974.
6 W. Lu, D. Yuan, D. Zhao, C. I. Schilling, O. Plietzsch,
T. Muller, S. Br
ase, J. Guenther, J. Bl
umel, R. Krishna, Z. Li
and H.-C. Zhou, Chem. Mater., 2010, 22, 5964.
7 M. G. Rabbani and H. M. El-Kaderi, Chem. Mater., 2011, 23,
1650.
8 Y.-Q. Shi, J. Zhu, X.-Q. Liu, J.-C. Geng and L.-B. Sun, ACS Appl.
Mater. Interfaces, 2014, 6, 20340.
9 R. Dawson, A. I. Cooper and D. J. Adams, Prog. Polym. Sci.,
2012, 37, 530.
10 Z. Xiang, X. Zhou, C. Zhou, S. Zhong, X. He, C. Qin and
D. Cao, J. Mater. Chem., 2012, 22, 22663.
J. Mater. Chem. A, 2015, 3, 1028410288 | 10287
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