Tetraphenyladamantane-based microporous polyimide for adsorption of carbon dioxide, hydrogen, organic and water vapors

Article abstract of DOI:10.1039/c3cc41012a

Tetraphenyladamantane-based microporous polyimide was synthesized. It can uptake 14.6 wt% CO₂ at 273 K and 1 bar, 99.2 wt% benzene and 59.7 wt% cyclohexane at 298 K and 0.9 bar, exhibiting potential applications in gas storage and recovery of o

Full text of DOI:10.1039/c3cc41012a

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Tetraphenyladamantane-based microporous polyimide
for adsorption of carbon dioxide, hydrogen, organic
and water vapors†
Cite this: Chem. Commun., 2013,
49, 3321
Received 8th January 2013,
Accepted 5th March 2013
Changjiang Shen, Yajie Bao and Zhonggang Wang*
DOI: 10.1039/c3cc41012a
www.rsc.org/chemcomm
Tetraphenyladamantane-based microporous polyimide was synthe- and large surface area, it simultaneously contains heterocyclic,
sized. It can uptake 14.6 wt% CO2 at 273 K and 1 bar, 99.2 wt% cycloaliphatic and aromatic components. The abundant nitrogen
benzene and 59.7 wt% cyclohexane at 298 K and 0.9 bar, exhibiting and oxygen atoms in the imide ring may give rise to high carbon
potential applications in gas storage and recovery of organic pollutants. dioxide (CO2) adsorption owing to the dipole–quadrupole
interactions between the pore surface and the CO2 molecule,9
Adamantane is a cycloaliphatic hydrocarbon with diamond-like cage while the large amount of phenyls and aliphatic rings can
structure. It is attractive because its bulky molecular volume, rigidity enhance affinity for both aromatic and aliphatic vapors, which
and highly symmetrical tetrahedral shape render it an ideal building are desirable as adsorbents for removal of organic pollutants in
block for the construction of metal–organic frameworks (MOFs) and the environmental protection field.
microporous organic polymers. Adamantane contains six secondary
The syntheses of the tetraamine monomer 1,3,5,7-tetrakis-
carbons and four tertiary carbons. Relatively, the four hydrogens (4-aminophenyl)adamantane (TAPA) and the polyimide network
attached to the tertiary carbons are chemically more active, and can (PI-ADPM) are depicted in Scheme 1. The raw compound tetraphenyl-
be easily halogenated,1 carboxylated2 and nitrated.3 Moreover, after adamantane (TPA) was obtained from 1-bromoadamantane and
arylation, the four phenyls surrounding the adamantane core are benzene in the presence of AlCl3.10 Then, with reference to the
convenient for further functionalization. In these aspects, Yaghi et al. procedure11 with some modifications, the nitration of TPA and
synthesized 1,3,5,7-adamantane tetracarboxylic acid2 and 1,3,5,7- subsequent reduction by Pd/C gave 1,3,5,7-tetrakis(4-aminophenyl)-
tetrakis(4-carboxylatophenyl)adamantane4 and used them for adamantane (TAPA) in good yield. The polyimide network was pre-
MOFs. Antonietti reported a covalent triazine-based framework pared through one-pot polycondensation in m-cresol from TAPA and
obtained from 1,3,5,7-tetrakis(4-cyanophenyl)adamantane.5 Cooper pyromellitic dianhydride (PMDA), using isoquinoline as a catalyst.
et al. synthesized a conjugated microporous polymer from 1,3,5,7-
tetrakis(4-bromophenyl)adamantane6 via Yamamoto coupling
reaction. Zhou et al. prepared a microporous polymer by homo-
coupling reaction of 1,3,5,7-tetrakis(4-ethynylphenyl)adamantane.7
In the past years, some microporous polyimides have been
developed, including linear polyimides with intrinsic microporosity
and hyper-cross-linked microporous polyimide networks synthesized
via polycondensation from various dianhydrides with tetrakis-
(4-aminophenyl)methane, tris(4-aminophenyl)amine and 1,3,5-
tris(4-aminophenyl)benzene.8 Up to now, however, microporous
polyimides constructed from the tetraphenyladamantane unit
have not appeared in the literature. In fact, different from other
microporous polymers, the tetraphenyladamantane-based polyimide
network is unique since, besides the possible microporous structure
State Key Laboratory of Fine Chemicals, Department of Polymer Science and
Materials, School of Chemical Engineering, Dalian University of Technology,
Dalian, 116024, China. E-mail: zgwang@dlut.edu.cn
† Electronic supplementary information (ESI) available: Synthesis and characterization
Scheme 1 Synthesis route of the polyimide network.
data. See DOI: 10.1039/c3cc41012a
c
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Fig. 2 Adsorption isotherms of CO2 and H2 of the polyimide network.
Fig. 1 (a) Nitrogen adsorption–desorption isotherm of the polyimide network
at 77 K, and (b) pore size distribution obtained by the NLDFT method.
The resultant brown solid is insoluble in any common organic
solvents, indicative of the hyper-cross-linked structure. In the FTIR
spectrum (Fig. S1, ESI†), the bands at 1776 cmÀ1 and 1720 cmÀ1
are attributed to the asymmetric and symmetric vibrations of the
imide ring, respectively. The absorption at 1375 cmÀ1 is due to
the characteristic vibration of the C–N–C linkage. As shown in the
13C solid NMR spectrum (Fig. S2, ESI†), the resonance at around
40.9 ppm belongs to the carbons of adamantane, while that at
166.0 ppm is ascribed to the carbonyl carbon of the imide ring. The
signal at 151.2 ppm is attributed to the carbon adjacent to the
nitrogen atom. Other aromatic carbons appear at 126–139 ppm.
The microporosity of PI-ADPM was examined by the physical
sorption of nitrogen at 77 K (Fig. 1). The steep rise in nitrogen uptake
at the low relative pressure indicates its microporous structure as
evidenced by the pore size distribution derived from nonlinear
density functional theory (NLDFT), which displays two microporous
peaks at 1.06 nm and 1.34 nm, and one ultramicroporous peak
at 0.68 nm. From the sorption isotherm, the calculated BET and
Fig. 3 Variations of isosteric enthalpies with the adsorbed amount of H2 and CO2.
Langmuir surface areas are 868 m2 gÀ1 and 1154 m2 gÀ1
,
respectively. Its total pore volume calculated at P/P0 = 0.99
and micropore volume derived from the t-plot method are
0.372 cm3 gÀ1 and 0.319 cm3 gÀ1, respectively.
The CO2 sorption isotherm of PI-ADPM was measured at
273 K and 298 K (Fig. 2), which shows a 14.6 wt% CO2 uptake at
273 K and 1 bar. This value is higher than those of many porous
organic polymers under the same conditions like COF-5 (5.9 wt%,
1670 m2 gÀ1),12 COF-103 (7.6 wt%, 3530 m2 gÀ1),12 and BLP-1H
(7.4 wt%, 1360 m2 gÀ1 13 even though they have larger surface area.
)
The isosteric enthalpies of adsorption (Qst) were calculated from
the CO2 isotherms at different temperatures.14 As shown in Fig. 3,
the Qst values display an apparently decreasing trend with the
adsorbed amount of CO2, implying that the gas–material interaction
is stronger than the gas–gas interaction. The virial plots of CO2 for
the polyimide have good linear relationships at both temperatures
(Fig. 4), from which the first virial coefficients can be calculated.
Subsequently, Henry’s law constant (KH) is obtained using the
equation KH = exp(A0), whereas the limiting enthalpy of adsorption
(Q0), i.e., Qst at zero surface CO2 coverage, is derived from the plot
Fig. 4 Virial plots of CO2 and H2 for the polyimide network.
slope of lnKH vs. 1/T. As a measure of the interaction between the
pore wall and the CO2 molecule, the Q0 value of CO2 is 34.4 kJ molÀ1
(Table S1, ESI†), which is higher than those for other porous
materials such as ZTF-1 (25.4 kJ mol )
À1 15 and BILP-1 (26.5 kJ molÀ1).16
This is due to the enhanced affinity for the CO2 molecule because of
c
3322 Chem. Commun., 2013, 49, 3321--3323
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polymers, the tetraphenyladamantane simultaneously possesses
aromatic and aliphatic characteristics, which endow it with
remarkably high uptakes of both aromatic and alkyl hydrocarbon
vapors, exhibiting promising applications in environmental
protection as adsorbents to adsorb organic pollutants.
We thank the National Science Foundation of China (No.
51073030 and 51273031) for financial support of this research.
Notes and references
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At 77 K and 1 bar, PI-ADPM exhibits 1.27 wt% hydrogen (H2)
uptake. It can be seen that, in the measured pressure range, the H2
uptake has not reached saturation, implying that larger storage can
be expected at higher pressure. The high adsorption capacity may
have arisen from the ultramicropores in the polyimide network.18
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The adsorption isotherms of benzene, n-hexane, cyclohexane
and water vapors measured at 298 K are illustrated in Fig. 5. It is
interesting to observe that the presence of cycloaliphatic structure
results in PI-ADPM possessing significantly higher uptakes of
aliphatic vapors than the wholly aromatic porous polymers. For
example, the adsorbed amounts of hexane and cyclohexane for
PI-ADPM are as high as 49.8 wt% and 59.7 wt%, respectively,
whereas the values for microporous polybenzimidazoles19 and
porous aromatic frameworks (PAF-2)20 are only 1 to 8 wt%.
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vapor, surpassing the previously reported polymers with a similar
BET surface area such as CE-1 (960 m2 gÀ1, 58.5 wt%),22 PAF-2
(891 m2 gÀ1, 13.8 wt%) and PAF-11 (891 m2 gÀ1, 87.4 wt%).23 This
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network. As a consequence, its uptake of water vapor is 28.45 wt%,
lower than that of the organic vapors.
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In conclusion, we have successfully synthesized a microporous
polyimide network based on the tetraphenyladamantane unit.
The sample uptakes 14.6 wt% CO2 at 273 K and 1 bar and
1.27 wt% H2 at 77 K and 1 bar. Different from previous porous
c
This journal is The Royal Society of Chemistry 2013
Chem. Commun., 2013, 49, 3321--3323 3323