An azine-linked hexaphenylbenzene based covalent organic framework

Article abstract of DOI:10.1039/c5cc10408d

In this communication, we report an azine linked covalent organic framework based on a six-fold symmetric hexphenylbenzene (HEX) monomer functionalized with aldehyde groups. HEX-COF 1 has an average pore size of 1 nm, a surface area in excess of 1200 m

Full text of DOI:10.1039/c5cc10408d

View Article Online
View Journal
ChemComm
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: S. B. Alahakoon,
C. M. Thompson, A. X. Nguyen, G. Occhialini, G. T. McCandless and R. A. Smaldone, Chem. Commun.,
2016, DOI: 10.1039/C5CC10408D.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/chemcomm

Please do not adjust margins
ChemComm
Page 1 of 4
View Article Online
DOI: 10.1039/C5CC10408D
ChemComm
COMMUNICATION
An Azine-Linked Hexaphenylbenzene Based Covalent Organic
Framework
Received 00th January 20xx,
Accepted 00th January 20xx
Sampath B. Alahakoon,† Christina M. Thompson,† Amy X. Nguyen, Gino Occhialini, Gregory T.
McCandless and Ronald A. Smaldone*
DOI: 10.1039/x0xx00000x
www.rsc.org/
In this communication, we report an azine linked covalent organic
framework based on a six-fold symmetric hexphenylbenzene
(
HEX) monomer functionalized with aldehyde groups. HEX-COF 1
has an average pore size of 1 nm, a surface area in excess of 1200
2
m /g and shows excellent sorption capability for carbon dioxide
(
20 wt%) and methane (2.3 wt%) at 273 K and 1 atm.
1
-4
Covalent organic frameworks (COFs) are a class of porous
polymers whose structures are formed under dynamic control
in either two or three dimensions. The structure and
properties of two-dimensional COFs in particular are
controlled by the dynamic interplay between noncovalent
aromatic interactions (i.e., π-stacking) and covalent bond
formation under thermodynamic control. COFs have become a
rapidly growing part of micro and mesoporous materials
1
, 5-10
11-14
discovery for gas storage,
catalysis,
and especially as
, 15-22
2
components for electronic and conductive materials
The
wide range of these potential applications is made possible by
the modular design of COFs, enabling one to not only predict
with high certainty, but also to tune, the pore size, shape, and
symmetry of the resulting 2D COF sheets through careful
design of the starting materials. Two and three fold symmetric
monomers are commonly used to form materials with lattices
that fit into hexagonal space groups. Porous polymers
containing HEX units have been previously reported by our
2
3, 24
25-29
group
and others.
Recently, the first COFs containing
six-fold symmetric HEX-based components were reported
resulting in materials with triangular shaped micropores and
1
7
electrically conductive properties.
Figure 1. (A) Synthesis of a COF using a six fold symmetric HEX monomer containing
aldehyde groups and hydrazine. (B) HEX-based monomers are non-planar as a result of
the steric hindrance between the phenyl rings. Resultant COFs have topologically
HEX-based COFs with this type of structure are interesting
due to their high π-density and extremely small pore size. To
date, much of the gas storage behaviour (specifically CO and planar 2D structures despite the lack of planarity in the monomers. (C) Synthesis of
2
CH ) for HEX-based COFs has yet to be reported.
4
HEX and HEX-COF 1.
To accomplish this we have synthesized an aldehyde
functionalized HEX monomer (Figure 1a-b) with six-fold
symmetry. Polymerization with a two-fold symmetric co-
monomer, such as hydrazine, will result in a COF containing
7
, 8, 30-33
triangular pores. Since azine linkages
are among the
smallest linkers available for COF synthesis, these pores should
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 2 of 4
View Article Online
DOI: 10.1039/C5CC10408D
COMMUNICATION
Journal Name
be approximately 1 nm, making them interesting for a variety
of sorption applications including gas separation via sieving.
The synthesis of HEX is carried out using a cobalt-catalyzed
cyclotrimerization as shown in Figure 1c. The precursor 4,4’-
diformyltolan (1) is made through a Sonogashira coupling as
3
4
previously reported in the literature. The polymerization of
HEX-COF 1 was performed using a solvent system of 2:1
mesitylene:dioxane with 0.1 mL of 6M aqueous AcOH catalyst
for 72 h at 120 ºC. FT-IR spectra (Figure S3-4) showed the
conversion of aldehyde peaks from HEX into azines as
3
0
Figure 3. (A) The powder X-ray diffraction pattern of HEX-COF 1 (black line) and the
simulated diffraction pattern from the model (red line). (B) A view of the interlayer
spacing of the model showing the lack of face-to-face π stacking interactions. (C)
demonstrated in previous work. The surface area and pore
size distributions were analysed by nitrogen adsorption
measurements at 77 K (Figure 2a). Using the Brunauer- Molecular model of HEX-COF 1 showing the pores measuring 11 Å in diameter.
Emmett-Teller (BET) model the surface area was calclulated to
2
be 1214 m /g. The pore size distribution (Figure 2b) was
determined using a non-local density functional theory carbon
slit pore model showing that the major population of NLDFT
pore width resides at ~11 Å.
Weak, or improperly aligned interlayer interactions could
result in poor adhesion and reduced long-range crystallinity –
something that has also been observed with other COFs that
1
1, 32
utilize aromatic systems that have non-planar structures.
The narrow pore size distribution and high surface area
indicate that this is an ordered material. However, powder X-
ray diffraction (PXRD) measurements of HEX-COF 1 have low
Simulated PXRD patterns generated from a molecular model of
HEX-COF 1 in a hexagonal P6/m space group (Figure 3a,c) give
unit cell parameters of 17.8 Å x 17.8 Å x 5.5 Å. Given the low
intensity of the peaks, additional Pawley refinement of the raw
data was not possible. The model in Figure 3b-c depicts a
perfectly eclipsed structure while the real structure is likely
slightly offset, these small differences cannot be resolved by
PXRD measurements. The modelled pore diameter is in good
agreement with the data in Figure 2b.
2
peak intensity (~10 counts) regardless of the solvent
conditions or reaction time used (Figure 3b). The poor long-
range order may be related to the inherent propeller shape of
the HEX monomer. It was recently shown that increasing van
der Waals interactions between 2D COF sheets drastically
3
5
impacts their rate of formation and resulting stability. The
canonical “face to face” -stacking found in most COF
π
monomers is lacking in our system, which must instead rely on
Other gas adsorption properties with HEX-COF 1 were also
evaluated. CO adsorption studies were performed at both
2
edge-to-edge interactions for interlayer adhesion.
2
73 and 298 K (Figure 4a) up to 1 atm. These measurements
indicate a strong affinity between the HEX-COF 1 and CO gas
2
molecules with nearly 20 wt% adsorbed at 273 K and an
enthalpy of adsorption that is 42 kJ/mol (Figure 4c). This is an
excellent value that ranks among the highest observed in COF-
6
-8, 36, 37
based materials.
Figure 4. (A) CO
CH isotherms at 273 K (filled circles) and 298 K (open circles). (C)
adsorption measurements for CO (black line) and CH (red line).
2
isotherms at 273 K (filled circles) and 298 K (open circles). (B)
4
Enthalpy of
Figure 2. (A) N
2
isotherm at 77 K. The BET surface area of HEX-COF 1 was measured to
2
4
2
be 1214 m /g. (B) NLDFT pore size distribution obtained from the N isotherm.
2
2
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 4
Please dCo h ne omt aC do j um s mt margins
View Article Online
DOI: 10.1039/C5CC10408D
Journal Name
COMMUNICATION
In addition to the polar azine functional groups, which no 12.
doubt contribute to the strong adsorption, the small pore sizes
S. Lin, C. S. Diercks, Y.-B. Zhang, N. Kornienko, E. M.
Nichols, Y. Zhao, A. R. Paris, D. Kim, P. Yang, O. M. Yaghi
and C. J. Chang, Science, 2015, 349, 1208-1213.
(
~11 Å in diameter) within HEX-based materials could also be a
factor. CH adsorption measurements (Figure 4b) were also
carried out showing that HEX-COF 1 can store up to 2.3 wt% of
CH at 273 K with maximum enthalpies of adsorption around
1
1
1
1
3.
4.
5.
6.
H. Xu, J. Gao and D. Jiang, Nature Chem., 2015, 7, 905-
4
9
12.
P. Pachfule, S. Kandambeth, D. Diaz Diaz and R. Banerjee,
Chem. Commun., 2014, 50, 3169-3172.
M. Dogru and T. Bein, Chem. Commun., 2014, 50, 5531-
4
2
7 kJ/mol (Figure 4c, red line).
In conclusion, we have synthesized a novel azine linked
5
546.
COF based on a six-fold symmetrical aldehyde functionalized
hexaphenylbenezene monomer. Interestingly, these COFs
display the adsorptions properties of an ordered microporous 17.
X.-H. Liu, C.-Z. Guan, D. Wang and L.-J. Wan, Adv. Mater.,
2014, 26, 6912-6920.
S. Dalapati, M. Addicoat, S. Jin, T. Sakurai, J. Gao, H. Xu, S.
Irle, S. Seki and D. Jiang, Nat. Commun., 2015, 6, 7786.
C. R. DeBlase, K. E. Silberstein, T.-T. Truong, H. D. Abruña
and W. R. Dichtel, J. Am. Chem. Soc., 2013, 135, 16821-
material with a type I isotherm and a narrow pore size
1
1
8.
9.
distribution, but with a relatively weak PXRD pattern indicating
a low level of long range order, likely owing to the poor
interlayer interactions between the propeller-shaped HEX
units. Despite the low level of long-range order, HEX-COF 1
1
6824.
C. R. DeBlase, K. Hernández-Burgos, K. E. Silberstein, G. G.
Rodríguez-Calero, R. P. Bisbey, H. D. Abruña and W. R.
Dichtel, ACS Nano, 2015, 9, 3178-3183.
2 4
exhibits outstanding surface area, CO and CH adsorption
capability. We believe the unique triangular shape and very
small pore sizes accessible through HEX-based monomers
make them an interesting family of COFs to study for insight on
how to design new materials for gas storage and sieving.
2
2
0.
1.
S. Duhović and M. Dincă, Chem. Mater., 2015, 27, 5487-
5
490.
Z. Zha, L. Xu, Z. Wang, X. Li, Q. Pan, P. Hu and S. Lei, ACS
Appl. Mater. Interfaces., 2015, 7, 17837-17843.
Designing HEX systems with improved interlayer stacking will 22.
further improve our understanding of the structure and design
rules required to reliably stitch together complex monomers
Y. Du, H. Yang, J. M. Whiteley, S. Wan, Y. Jin, S.-H. Lee and
W. Zhang, Angew. Chem. Int. Ed., 2015, DOI:
1
0.1002/anie.201509014.
2
3.
C. M. Thompson, G. T. McCandless, S. N. Wijenayake, O.
Alfarawati, M. Jahangiri, A. Kokash, Z. Tran and R. A.
Smaldone, Macromolecules, 2014, 47, 8645-8652.
C. M. Thompson, F. Li and R. A. Smaldone, Chem.
Commun., 2014, 50, 6171-6173.
Q. Chen, M. Luo, T. Wang, J.-X. Wang, D. Zhou, Y. Han, C.-
S. Zhang, C.-G. Yan and B.-H. Han, Macromolecules, 2011,
44, 5573-5577.
into ordered COFs with designed properties.
This research was carried out with support from the
University of Texas, Dallas, and the American Chemical Society
Petroleum Research Fund (52906-DNI10). We would like to
acknowledge Sahila Perananthan, Wijayantha Perera and
Chamaal Karunaweera for assistance with thermal and spectral
analysis.
2
2
4.
5.
Notes and references
26.
C. Zhang, L.-H. Peng, B. Li, Y. Liu, P.-C. Zhu, Z. Wang, D.-H.
Zhan, B. Tan, X.-L. Yang and H.-B. Xu, Polym. Chem., 2013,
4
, 3663-3666.
1.
2.
3.
4.
A. P. Cote, A. I. Benin, N. W. Ockwig, M. O'Keeffe, A. J.
Matzger and O. M. Yaghi, Science, 2005, 310, 1166-1170.
J. W. Colson and W. R. Dichtel, Nature Chem., 2013, 5,
2
7.
R. Short, M. Carta, C. G. Bezzu, D. Fritsch, B. M. Kariuki
and N. B. McKeown, Chem. Commun., 2011, 47, 6822-
6
M. Carta, P. Bernardo, G. Clarizia, J. C. Jansen and N. B.
McKeown, Macromolecules, 2014, 47, 8320-8327.
P. T. K. Nguyen, H. T. D. Nguyen, H. Q. Pham, J. Kim, K. E.
Cordova and H. Furukawa, Inorg. Chem., 2015, 54, 10065-
824.
4
53-465.
P. J. Waller, F. Gándara and O. M. Yaghi, Acc. Chem. Rev.,
015, DOI: 10.1021/acs.accounts.5b00369.
2
2
8.
9.
2
H. M. El-Kaderi, J. R. Hunt, J. L. Mendoza-Cortés, A. P.
Côté, R. E. Taylor, M. O'Keeffe and O. M. Yaghi, Science,
1
0072.
2
007, 316, 268-272.
E. Ganz and M. Dornfeld, J. Phys. Chem. C, 2012, 116,
661-3666.
3
3
0.
1.
S. Dalapati, S. Jin, J. Gao, Y. Xu, A. Nagai and D. Jiang, J.
Am. Chem. Soc., 2013, 135, 17310-17313.
L. Stegbauer, M. W. Hahn, A. Jentys, G. Savasci, C.
Ochsenfeld, J. A. Lercher and B. V. Lotsch, Chem. Mater.,
5
.
.
3
6
M. G. Rabbani, A. K. Sekizkardes, Z. Kahveci, T. E. Reich, R.
Ding and H. M. El-Kaderi, Chem. Eur. J., 2013, 19, 3324-
2
015, DOI: 10.1021/acs.chemmater.5b02151.
J.-Y. Yue, X.-H. Liu, B. Sun and D. Wang, Chem. Commun.,
015, 51, 14318-14321.
Y. Zhu, S. Wan, Y. Jin and W. Zhang, J. Am. Chem. Soc.,
015, DOI: 10.1021/jacs.5b09487.
3328.
3
3
3
2.
3.
4.
7
8
9
1
1
.
Z. Li, X. Feng, Y. Zou, Y. Zhang, H. Xia, X. Liu and Y. Mu,
Chem. Commun., 2014, 50, 13825-13828.
Z. Li, Y. Zhi, X. Feng, X. Ding, Y. Zou, X. Liu and Y. Mu,
Chem. Eur. J., 2015, 21, 12079-12084.
L. A. Baldwin, J. W. Crowe, M. D. Shannon, C. P. Jaroniec
and P. L. McGrier, Chem. Mater., 2015, 27, 6169-6172.
Z. Xiang, D. Cao, J. Lan, W. Wang and D. P. Broom, Energ.
Environ. Sci., 2010, 3, 1469-1487.
L. Stegbauer, K. Schwinghammer and B. V. Lotsch, Chem.
Sci., 2014, 5, 2789-2793.
2
.
2
Y. B. Borozdina, E. Mostovich, V. Enkelmann, B. Wolf, P. T.
Cong, U. Tutsch, M. Lang and M. Baumgarten, J. Mater.
Chem. C, 2014, 2, 6618-6629.
B. J. Smith and W. R. Dichtel, J. Am. Chem. Soc., 2014, 136,
8
.
0.
1.
3
3
5.
6.
783-8789.
Z. Kahveci, T. Islamoglu, G. A. Shar, R. Ding and H. M. El-
Kaderi, CrystEngComm, 2013, 15, 1524-1527.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 4 of 4
View Article Online
DOI: 10.1039/C5CC10408D
COMMUNICATION
Journal Name
37.
N. Huang, X. Chen, R. Krishna and D. Jiang, Angew. Chem.
Int. Ed., 2015, 54, 2986-2990.
4
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins