A highly porous three-dimensional aluminum phosphonate with hexagonal channels: Synthesis, structure and adsorption properties

Article abstract of DOI:10.1039/c3dt53167h

A 3D porous aluminum(iii) trisphosphonate, constructed from 1D inorganic aluminum phosphate chains and tripodal organic linkers, contains large hexagonal channels (1.24 nm in diameter) and a highly accessible void (50.3%) which allow it to have a fast and relatively high uptake of H₂, N₂ and CO₂. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c3dt53167h

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A highly porous three-dimensional aluminum
phosphonate with hexagonal channels: synthesis,
structure and adsorption properties†
Cite this: Dalton Trans., 2014, 43,
5970
Received 8th November 2013,
Accepted 26th November 2013
Si-Fu Tang, Jin-Jun Cai, Liang-Jun Li, Xiao-Xia Lv, Chao Wang and Xue-Bo Zhao*
DOI: 10.1039/c3dt53167h
www.rsc.org/dalton
A 3D porous aluminum(III) trisphosphonate, constructed from 1D monoester linkers.10 However, metal phosphonates are usually
inorganic aluminum phosphate chains and tripodal organic linkers, not porous but have layered structures which are not suitable
contains large hexagonal channels (1.24 nm in diameter) and a for the application of gas storage/separation. For a long time
highly accessible void (50.3%) which allow it to have a fast and porous metal phosphonates were very rare and very few were
relatively high uptake of H2, N2 and CO2.
tested for gas storage/separation application.11–14 Al(III) has
long been the focus of research interest in the field of MOFs in
the consideration of enhancing weight gas uptake15–20 and at
the same time it is also the important component of zeolites.
Thus we decided to continue our work to explore new Al-phos-
phonates with novel structure, high porosity and good stability.
But it is a challenge to construct porous Al-phosphonates
due to poor crystallinity. Until now very few three-dimen-
sional Al-phosphonates have been reported and most of
them were structurally characterized from the powder tech-
nique.21 There is no report on porous Al-phosphonate with a
channel size larger than 1 nm. Luckily, by carefully altering
the ligand/metal (L/M) molar ratio, solvent and temperature,
one aluminum(III) trisphosphonate, Al(H3L)(H2O) (1) (H6L =
(2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene)triphosphonic
acid), was successfully obtained hydro(solvo)thermally from
H6L and Al2(SO4)3·18H2O (L/M: 0.8) in a mixed solvent of
CH3CH2OH–H2O (v/v: 9 : 1) at 140 °C (see the Experimental
section in ESI†). Here the structure and gas adsorption pro-
perties are presented and discussed.
Metal–organic frameworks (MOFs) or porous coordination
polymers (CPs) have attracted a great deal of interest in the
past two decades for their promising applications in the field
of gas storage,1 separation2 and catalysis,3 which are mainly
related to their high porosity, high specific surface area and
pore size/shape tunable character. Understanding the struc-
ture–property relationship and controlling the structures and
properties of MOFs are vital to maximize the gas storage
capacity and separation efficiency. Effective strategies, includ-
ing enlargement of surface area and pore size, proper pore
shape, high unsaturated coordination site density, and so on,
have been developed to improve the design, synthesis and gas
storage capacity.4–6 However, chemical and physical stability
must be considered to reach the requirement of application.
Currently most studied MOFs are assembled from rigid or flex-
ible carboxylic acids and N-containing neutral ligands with
first-row transition metals. Some of them really have very good
performance in terms of gas capacity and selective uptake but
suffer from poor stability, for example ZnO4 tetrahedra tend to
hydrolyse in the presence of water vapor.7,8
Compound 1 has a three-dimensional framework structure
containing regular hexagonal channels along the c-direction. It
We have special interest in the design and synthesis of
metal phosphonates for their intriguing structures, properties
and importantly their close relationship to aluminum silicate
or phosphate zeolites which are chemically and mechanically
robust.9 Shimizu and coworkers reported that the water
stability of MOFs can be greatly enhanced via phosphonate
ˉ
crystallizes in the R3 space group with 18 molecules in each
unit cell (see Table S1†). There is one crystallographic indepen-
dent aluminum ion, one triply deprotonated trisphosphonate
ligand, and one coordinated water molecule in each asym-
metric unit. The crystallographic independent aluminum(III)
ion is six-coordinated by five phosphonate oxygen atoms of
four trisphosphonate ligands and one aqua ligand, forming an
AlO6 octahedron (see Fig. 1a). The Al–O, P–O and C–P dis-
tances are found in the range of 1.841(3)–1.999(3), 1.487(3)–
1.558(3) and 1.797(4)–1.808(4) Å (see Table S2†), respectively,
which are all comparable to those of other reported alumi-
num-phosphonates.22 The three phosphonate groups in the
trisphosphonate ligand are all singly protonated and adopt a
Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of
Sciences, Qingdao 266101, China. E-mail: zhaoxb@qibebt.ac.cn;
Fax: +86 0532 80662729; Tel: +86 0532 80662728
†Electronic supplementary information (ESI) available: H bonds, PXRD, IR and
Langmuir and BET graphs for CO2 adsorption on activated 1; X-ray crystallo-
graphic files for 1 in CIF format. CCDC 969636. For ESI and crystallographic
data in CIF or other electronic format see DOI: 10.1039/c3dt53167h
5970 | Dalton Trans., 2014, 43, 5970–5973
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Fig. 1 Ligand H6L (a), a one-dimensional aluminum phosphate chain
along the c-direction (b), a three-dimensional framework structure
viewing along the c-direction (c) and
viewing along the c-direction (d) in compound 1. The AlO6 octahedra
and –CPO3 tetrahedra are shaded in cyan and blue, respectively.
a Connolly surface diagram
Fig. 2 PXRD patterns of simulated, as-synthesized, activated and
treated in water samples of 1.
cis–cis–cis conformation which is rarely observed for tripodal 3 hours. The PXRD experiments also verified the framework
ligands in 3D structural compounds.9a Two of the three –PO3 stability (see Fig. 2), suggesting its good resistance to water,
groups are bidentate whereas the third is monodentate; there- and could be ascribed to the chemical stability of metal phos-
fore, the coordination mode of the trisphosphonate ligand can phonates and the hydrophobic channel of 1.
be denoted as μ4:η0:η1:η1:η0:η1:η1:η0:η0:η1, which means each
To investigate the porosity of this Al(III) compound, nitrogen,
trisphosphonate ligand binds four aluminum ions in total carbon dioxide and hydrogen adsorptions were performed gravi-
with its five oxygen atoms. Neighboring aluminum ions are metrically using an Intelligent Gravimetric Analyzer (IGA). The
chelated by the bidentate phosphonate groups into 1D infinite sample of about 100 milligrams was loaded into the IGA and
aluminum phosphate chains along the c-direction (see Fig. 1b) degassed at 100 °C under vacuum (∼10−6 mbar) for six hours to
which are further bridged in three directions by the mono- a constant weight. The adsorption isotherms are presented in
dentate phosphonate groups into a three-dimensional framework Fig. 3a–3c; obviously activated sample 1 can reversibly and
structure leaving large regular hexagonal channels along the quickly adsorb N2, H2 and CO2 at different investigated tempera-
c-direction (see Fig. 1c). The diameter of the channel is found tures and their adsorption isotherms can be classified as typical
to be about 12.4 Å, whereas in the remaining two directions Type I adsorption curves according to the IUPAC standards.23
the parallelogram channels are much smaller (3.5 × 5.8 Å2; see
The uptake capacity of N2 at 77 K and 1 bar was determined
Fig. S1†). It is noticeable that the hexagonal channels connect to be 26% (wt) (208 ml g−1 STP), suggesting a Langmuir (BET)
with the parallelogram channels at the edges of the hexagons surface area of 901.5 (687.2) m2 g−1 (see Fig. S3 and S4†), and
and the inner surfaces of the hexagonal channels are mainly is comparable to those of CPF-124 and [Ba(HBTB)].25 The total
lined with benzene rings, suggesting a hydrophobic character pore volume obtained from the Langmuir isotherm model was
(see Fig. 1d). The accessible void is estimated by PLATON to be calculated to be 0.32 cm3 g−1 or 32.41% (v/v), lower than the
about 50.3%, in which a large amount of solvent molecules estimated solvent accessible porosity of 50.3% (v/v) from
are accommodated, forming a few O–H⋯O bonds with the PLATON. Probably it was caused by the incomplete removal of
uncoordinated phosphonate oxygen atoms (see Table S3†).
guest molecules26 and overestimation by the program.27 The
Thermal gravimetric analysis (TGA) and powder X-ray diffr- adsorption of H2 on activated 1 was also investigated. At 77 K
action (PXRD) measurements were carried out to examine the and 20 bars, the total H2 uptake was about 2.0% (wt) (226 ml
thermal and moisture stability of 1. The TGA curve of as-syn- g−1 STP). The ascending isotherm clearly indicates the unsatu-
thesized 1 shows the release of guest molecules from 21 to rated uptake of H2 under 20 bars and a weaker adsorbate–
160 °C, leading to a weight loss of 16.43% (Fig. S2, ESI†). To adsorbent interaction. The adsorption of CO2 on activated 1
facilitate the removal of guest molecules and protect the struc- was carried out at 195, 273 and 298 K, respectively. At 195 K
tural integrity, as-synthesized crystals were solvent-exchanged the uptake of CO2 was very fast and amounted to 33.5% (wt)
by soaking in acetone for three weeks and further treated (171 ml g−1 STP) at 1 bar, comparable to that of DUT-30(Zn).28
under vacuum (about 10−6 mbar) at 100 °C for 6 hours. The When the temperature was increased to 273 and 298 K, the
good agreement of the experimental and simulated XRD pat- adsorption of CO2 obviously reduced. Based on the sorption
terns of activated 1 demonstrates that the framework structure data of CO2 at 273 and 298 K, the isosteric adsorption heats
of 1 can be retained after the removal of guest molecules. To (Qst) on activated 1 were calculated from Virial analysis com-
test the stability of 1 to water, the as-synthesized crystals were bined with the Clausius–Clapeyron equation. As shown in
also soaked in cold water for 3 days and boiling water for Fig. S5,† the enthalpies lie in the range of 15.9–18.8 kJ mol−1
,
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chains and cis–cis–cis conformational tripodal organic linkers
and contains hexagonal channels of 1.24 nm in diameter. It
has good thermal stability and shows good resistance to water.
The adsorption results clearly suggest that it has a fast and
relatively high uptake of H2, N2 and CO2. To further improve
the stability, rigid phosphonate ligands will be employed for
the construction of porous MOFs in future work.
This work was supported by the National Natural Science
Foundation of China (no. 21171173 and 21173246).
Notes and references
1 Y. H. Hu and L. Zhang, Adv. Mater., 2010, 22, E117–E130.
2 K. Sumida, D. L. Rogow, J. A. Mason, T. M. McDonald,
E. D. Bloch, Z. R. Herm, T.-H. Bae and J. R. Long, Chem.
Rev., 2012, 112, 724–781.
3 C. Zou, Z. Zhang, X. Xu, Q. Gong, J. Li and C.-D. Wu, J. Am.
Chem. Soc., 2012, 134, 87–90.
4 Z. R. Herm, B. M. Wiers, J. A. Mason, J. M. van Baten,
M. R. Hudson, P. Zajdel, C. M. Brown, N. Masciocchi,
R. Krishna and J. R. Long, Science, 2013, 360, 960–964.
5 D.-X. Xue, A. J. Cairns, Y. Belmabkhout, L. Wojtas, Y. Liu,
M. H. Alkordi and M. Eddaoudi, J. Am. Chem. Soc., 2013,
135, 7660–7667.
6 H. Deng, S. Grunder, K. E. Cordova, C. Valente,
H. Furukawa, M. Hmadeh, F. Gándara, A. C. Whalley,
Z. Liu, S. Asahina, H. Kazumori, M. O’Keeffe, O. Terasaki,
J. F. Stoddart and O. M. Yaghi, Science, 2012, 336, 1018–
1023.
7 K. J. Gagnon, H. P. Perry and A. Clearfield, Chem. Rev.,
2012, 112, 1034–1054.
8 S. S. Kaye, A. Dailly, O. M. Yaghi and J. R. Long, J. Am.
Chem. Soc., 2007, 129, 14176–14177.
9 (a) S. F. Tang, X. B. Pan, X. X. Lv, S. H. Yan, X. R. Xu, L. J. Li
and X. B. Zhao, CrystEngComm, 2013, 15, 1860–1873;
(b) S. F. Tang, X. B. Pan, X. X. Lv and X. B. Zhao, J. Solid
State Chem., 2013, 197, 139–146; (c) S. F. Tang, J. L. Song,
X. L. Li and J. G. Mao, Cryst. Growth Des., 2007, 7, 360–366;
(d) S. F. Tang, J. L. Song and J. G. Mao, Eur. J. Inorg. Chem.,
2006, 2011–2019; (e) S. F. Tang, J. L. Song, X. L. Li and
J. G. Mao, Cryst. Growth Des., 2006, 6, 2322–2326.
10 J. M. Taylor, R. Vaidhyanathan, S. S. Iremonger and
G. K. H. Shimizu, J. Am. Chem. Soc., 2012, 134, 14338–
14340.
Fig. 3 Adsorption isotherms for N2 (a) and H2 (b) at 77 K, CO2 (c) at 195,
273 and 298 K on activated 1.
11 S. S. Iremonger, J. Liang, R. Vaidhyanathan, I. Martens,
G. K. H. Shimizu, T. D. Daff, M. Z. Aghaji, S. Yeganegi and
T. K. Woo, J. Am. Chem. Soc., 2011, 133, 20048–20051.
12 M. T. Wharmby, J. P. S. Mowat, S. P. Thompson and
P. A. Wright, J. Am. Chem. Soc., 2011, 133, 1266–1269.
which are lower than the common values observed for CO2
adsorption on porous MOF materials,2 suggesting a quite non- 13 J. Liang and G. K. H. Shimizu, Inorg. Chem., 2007, 46,
polar surface.
In summary, one porous aluminum(III) phosphonate has 14 M. Taddei, F. Costantino, A. Ienco, A. Comotti, P. V. Dau
been successfully synthesized from a trisphosphonate ligand.
and S. M. Cohen, Chem. Commun., 2013, 49, 1315–1317.
It has a very interesting 3D framework structure which is 15 Y. X. Tan, F. Wang, Y. Kang and J. Zhang, Chem. Commun.,
10449–10451.
constructed from 1D inorganic aluminum phosphate infinite
2011, 47, 770–772.
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16 (a) C. Volkringer, T. Loiseau, M. Haouas, F. Taulelle,
D. Popov, M. Burghammer, C. Riekel, C. Zlotea, F. Cuevas,
M. Latroche, D. Phanon, C. Knöfelv, P. L. Llewellyn and
G. Férey, Chem. Mater., 2009, 21, 5783; (b) C. Volkringer,
T. Loiseau, N. Guillou, G. Férey, M. Haouas, F. Taulelle,
N. Audebrand, I. Margiolaki, D. Popov, M. Burghammer
and C. Riekel, Cryst. Growth Des., 2009, 9, 2927;
(c) C. Volkringer, D. Popov, T. Loiseau, G. Férey,
(e) M. Mar Gómez-Alcantara, M. A. G. Aranda, P. Olivera-
Pastor, P. Beran, J. García-Muñoz and A. Cabeza, Dalton
Trans., 2006, 577–585; (f) C. Serre, J. A. Groves, P. Lightfoot,
A. M. Z. Slawin, P. A. Wright, N. Stock, T. Bein, M. Haouas,
F. Taulelle and G. Férey, Chem. Mater., 2006, 18, 1451–1457;
(g) H. G. Harvey, J. Hu and M. P. Attfield, Chem. Mater.,
2003, 15, 179–188; (h) C. A. Merrill and A. K. Cheetham,
Inorg. Chem., 2005, 44, 5273–5277.
M. Burghammer, C. Riekel, M. Haouas and F. Taulelle, 22 (a) A. A. Ayi, T. L. Kinnibrugh and A. Clearfield, Dalton
Chem. Mater., 2009, 21, 5695.
17 P. Serra-Crespo, E. V. Ramos-Fernandez, J. Gascon and
F. Kapteijn, Chem. Mater., 2011, 23, 2565.
18 T. Ahnfeldt, N. Guillou, D. Gunzelmann, I. Margiolaki,
T. Loiseau, G. Férey, J. Senker and N. Stock, Angew. Chem.,
Int. Ed., 2009, 48, 5163.
Trans., 2011, 40, 12648–12650; (b) A. F. Richards and
C. M. Beavers, Dalton Trans., 2012, 41, 11305–11310.
23 K. S. W. Sing, D. H. Everett, R. A. W. Haul, L. Moscou,
R. A. Pierotti, J. Rouquerol and T. Siemienewska, Pure Appl.
Chem., 1985, 57, 603–619.
24 Q. Lin, T. Wu, S.-T. Zheng, X. Bu and P. Feng, Chem.
Commun., 2011, 47, 11852–11854.
19 T. Ahnfeldt, D. Gunzelmann, T. Loiseau, D. Hirsemann,
J. Senker, G. Férey and N. Stock, Inorg. Chem., 2009, 48, 25 M. L. Foo, S. Horike and S. Kitagawa, Inorg. Chem., 2011,
3057. 50, 11853–11855.
20 D. Himsl, D. Wallacher and M. Hartmann, Angew. Chem., 26 (a) J. E. Mondloch, O. Karagiaridi, O. K. Farha and
Int. Ed., 2009, 48, 4639.
21 (a) K. Maeda, J. Akimoto, Y. Kiyozumi and F. Mizukami,
Angew. Chem., Int. Ed. Engl., 1995, 34, 1199–1201;
J. T. Hupp, CrystEngComm, 2013, 15, 9258–9264; (b) L. J. Li,
S. F. Tang, X. X. Lv, M. Jiang, C. Wang and X. B. Zhao, New
J. Chem., 2013, 37, 3662–3670.
(b) K. Maeda, J. Akimoto, Y. Kiyozumi and F. Mizukami, 27 S. S. Iremonger, J. Liang, R. Vaidhyanathan and
J. Chem. Soc., Chem. Commun., 1995, 1033–1034; G. K. H. Shimizu, Chem. Commun., 2011, 47, 4430–4432.
(c) H. G. Harvey, B. Slater and M. P. Attfield, Chem.–Eur. J., 28 I. M. Hauptvogel, R. Biedermann, N. Klein, I. Senkovska,
2004, 10, 3270–3278; (d) H. G. Harvey, S. J. Teat and
M. P. Attfield, J. Mater. Chem., 2000, 10, 2632–2633;
A. Cadiau, D. Wallacher, R. Feyerherm and S. Kaskel, Inorg.
Chem., 2011, 50, 8367–8374.
This journal is © The Royal Society of Chemistry 2014
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