DOI: 10.1021/cg100783w
Polyoxometalate-Based Porous Framework with Perovskite Topology Xiao-Lan Wang,#,† Yang-Guang Li,# Ying Lu,*,# Hai Fu,# Zhong-Min Su,# and En-Bo Wang*,#
2010, Vol. 10 4227–4230
# Key Laboratory of Polyoxometalate Science of Ministry of Education, Institute of Polyoxometalate Chemistry, Department of Chemistry, Northeast Normal University, Changchun, Jilin, 130024, P. R. China, and †Department of Chemistry, BaiCheng Education Normal College, Baicheng, Jilin, 137000, P. R. China
Received June 11, 2010; Revised Manuscript Received August 24, 2010
ABSTRACT: With the use of a flexible N-donor ligand 1,3-bis(4-pyridyl)propane (bpp), a new porous framework with WellsDawson clusters as nodes and Ni2þ ions as linkers, [Ni(bpp)(H2O)2]3[P2W18O62] 3 ∼24H2O (1), has been successfully obtained. Topological analysis indicates that 1 possesses a perovskite structure. As a porous framework, 1 displays adsorption behavior toward H2O and CH3OH. Porous materials with regular, bulky, accessible cages and channels have aroused great research interest in recent years due to their potential applications in gas storage, separation, ion-exchange, and heterogeneous catalysis.1 In this research field, the extensive exploration of crystalline inorganic-organic hybrid compounds has successfully created new classes of microporous compounds such as metal-organic frameworks (MOFs) and porous coordination polymers (PCP).2 One of the main synthetic strategies for these compounds is based on the diversity of secondary metal oxide clusters that can be linked with numerous organic linkers.3 Polyoxometalates (POMs), as one kind of unique metal oxide cluster, have been considered as promising secondary building units for the construction of porous frameworks because of their nanosize, adjustable compositions, and abundant topologies as well as their oxygen-rich surface with strong coordination abilities.4 Moreover, porous frameworks based on POM building blocks lead to the combination of porosity with diverse electronic, magnetic, catalytic, and photochemical properties of POMs, which makes them an attractive perspective for applications as highly selective catalysts and multifunctional materials. Although continuous efforts are being devoted to the design of POM-based porous materials owing to their promising applications, only a few of such materials have hitherto been obtained.5 Thus, rational design of these materials remains a great challenge. One main strategy used for fabricating POM-based porous frameworks is to construct open frameworks with POM clusters as nodes and transition metal (TM) ions as linkers (Scheme 1a). Following this strategy, quite a few of such frameworks have been synthesized,6 but they are usually less thermal-stable and/or easily disassembled in solution.6e-g Further, the internal cavities of these frameworks are small owing to the presence of interpenetration (Scheme 1b).6a,b,e,f Therefore, it is very important to explore new ways to avoid interpenetration so as to keep large cavities within these frameworks. Our approach is to modify partial porous windows with appropriate organic ligands via connecting two adjacent TM cations on the same plane (Scheme 1c). After modification, a part of the windows is small or even closed, which can effectively prohibit interpenetration and retain large and accessible cages and channels. Another advantage of this strategy is that such ligand-modified porous frameworks might be easily stabilized and the pore size can be readily tuned by choosing suitable organic ligands. The present work demonstrates a successful example of this approach. With the use of a flexible N-donor ligand 1,3-bis(4-pyridyl)propane (bpp), a new porous framework *Corresponding author. Tel: þ86-431-85098787; fax: þ86-431-85098787; e-mail:
[email protected] (E.-B.W.);
[email protected] (Y.L.). r 2010 American Chemical Society
Scheme 1. (a) Schematic Representation of the POM-Based Porous Framework with Polyoxoanions As Nodes and Transition Metal (TM) Cations As Linkers; (b) Two-Fold Interpenetrated Framework; (c) Ligand-Modified Framework
[Ni(bpp)(H2O)2]3[P2W18O62] 3 ∼24H2O (1 3 ∼24H2O)7 has been obtained. Compound 1 was hydrothermally synthesized by the mixture of bpp, NiCl2 3 2H2O, and K6[R-P2W18O62] 3 19H2O in pH = 6 aqueous solution at 160 °C for 5 days.8 Single crystal X-ray diffraction analysis9 reveals that 1 crystallizes in cubic Pm3n space group and displays a three-dimensional (3D) porous framework constructed from the Dawson-type polyoxoanions and Ni2þ cationic linkers. The whole neutral porous framework is modified and stabilized by the flexible bpp ligands. The polyoxoanion [R-P2W18O62]6- shows a typical Wells-Dawson configuration with approximate D3h symmetry (Figure S1, Supporting Information). Usually, a Wells-Dawson cluster possesses a large number of surface coordination oxygen atoms (18 terminal and 36 μ2 oxygen atoms) and two structurally distinct types of metal centers (6 polar and 12 equatorial metal atoms), which may offer many different coordination types with TM ions. Several coordination modes of Dawson cluster with TM ions have been reported, and the highest number of TM ions coordinating to a Dawson cluster can be 9.10 In 1, each [R-P2W18O62]6- links with six Ni2þ ions through six terminal oxygen atoms from six distinct equatorial {WO6} octahedra (Figure S2, Supporting Information). The arrangement of the six Ni2þ ions around the [R-P2W18O62]6- cluster can be regarded as an approximate octahedron mode, which has never been observed in previous Dawsonbased frameworks. On the other hand, each Ni2þ cation adopts the octahedral geometry, which is coordinated by two terminal oxygen atoms from two [R-P2W18O62]6- polyoxoanions, two water molecules, and two N atoms from two bpp ligands (Figure S1, Supporting Information). On the basis of the above-mentioned coordination modes, compound 1 displays a neutral porous framework with two types of cubic cages (labeled as cage A and cage B in Figure 1). The diameters of the inner spaces for cage A and cage B are ca. 13.3 A˚ and ca. 16.3 A˚ based on the closest Ni 3 3 3 Ni distances, respectively. In the cubic cage A (Figures 1a Published on Web 09/13/2010
pubs.acs.org/crystal
4228
Crystal Growth & Design, Vol. 10, No. 10, 2010
and S3), four windows are well closed by eight bpp ligands in a cross-like mode. Each flexible bpp ligand links to two opposite Ni2þ ions on the same plane of the cubic cage unit. Thus, the inner space of cage A is partially occupied by four bpp ligands with only a small “hole” of 5.3 8.2 A˚ viewed along the direction of two open windows (Figure S3c, Supporting Information). In the cubic cage B (Figures 1b and S4), all six windows are fully open and all the coordinated water molecules on the Ni centers extend into the cage, indicating a hydrophilic environment in the cage B. In the 3D packing arrangement, two open windows of the cage A are linked to two adjacent cage B in a face-sharing mode, while the other four close windows of the cage A are face-shared by the adjacent four cage A units. On the basis of this connection mode, it is easy to deduce that each cage B is surrouned by six cage A, while each cage A is surrouned by two cage B and four cage A (Figure 2). In the unit cell of 1, the quantity ratio of cage A to cage B is 3:1. Topological analysis indicates that 1 features a
Figure 1. View of the two types of cages in 1. The inner spaces of cage A and cage B are simulated by blue and yellow balls, respectively. ({WO6}, red octahedra; {PO4}, yellow tetrahedra; {NiN2O4}, green octahedra; bpp ligand, black ball-and-sticks).
Wang et al. perovskit architecture when [R-P2W18O62]6- clusters are considered as six-connected nodes and Ni2þ ions as linkers (Figure 2d).11 The porous framework of 1 shows a case of keeping large cavities without interpenetration by virtue of modifying partial cage windows with flexible N-donor organic ligands. The large cages and channels in 1 are occupied by the solvent water molecules. The accessible void in the desolvated structure of 1 is ca. 39.3% of the total volume estimated by PLATON/SOLV.12 Powder X-ray diffraction (PXRD) was measured to confirm the phase purity and to examine the crystallinity of bulk samples (Figure 3a). To study the adsorption property, the adsorption isotherms of water and methanol for 1 were measured at 298 K. Before the measurements, the crystalline sample of 1 was heated at 100 °C for 12 h under a vacuum to remove the guest solvent molecules. As shown in Figure 3b, the amount of water sorption increases suddenly after P/P0 > 0.4 and reaches 88.4 mg/g at saturation, indicating that the solvent water molecules can enter into the bulk material.13 The saturated sorption amount of water of 1 is equivalent to the adsorption of about 26 H2O molecules per formula unit. As for methanol, the sorption amount increases slowly with an increase in P/P0 and reaches 16.8 mg/g at saturation. The saturated sorption amount of methanol of 1 is equivalent to the adsorption of about 3 CH3OH molecules per formula unit. The X-ray powder diffraction patterns of as-synthesized, evacuated, and water or methanol exchanged solids are identical to the calculated pattern except that the intensities and the widths show some differences (Figure 3a), revealing that the host-framework of 1 is retained after the loss of the guest molecules.13 To investigate the redox property of 1, the cyclic voltammetry of 1-bulk-modified carbon paste electrode in 1 M H2SO4 aqueous solution was measured in the potential range from þ800 to -600 mV at different scan rates (Figure S6, Supporting Information). The cyclic voltammogram shows four quasi reversible redox
Figure 2. (a) View of one type of 2D layer in the unit cell of 1. (b) View of the other type of 2D layer in the unit cell of 1. (c) View of the 3D packing of two types of layers in the unit cell of 1. (d) View of the perovskite architecture of 1 (red balls represent Dawson-type polyoxoanions and blue balls represent Ni2þ ions).
Communication
Crystal Growth & Design, Vol. 10, No. 10, 2010
4229
Supporting Information Available: X-ray crystallographic file in CIF format, TG, IR spectrum, XRPD, electrochemistry and additional structural figures of 1. This material is available free of charge via the Internet at http://pubs.acs.org.
References
Figure 3. (a) The XPRD patterns of 1: (i) calculated, (ii) as-synthesized sample at room temperature, (iii) evacuated sample of 1 (heated at 100 °C for 12 h under vacuum), (iv) water exchanged sample of 1, (v) methanol exchanged sample of 1. The tiny differences in intensity are due to the preferred orientation of the powder samples. The tiny differences in widths may due to the loss of partial crystallinity when the solvent and coordinated water molecules were removed from the bulk material. (b) Water and methanol adsorption isotherms for 1 at 298 K.
peaks I-I0 , II-II0 , III-III0 , IV-IV0 at E1/2 = 460, 101, -100, and -312 mV, respectively (E1/2 = (Epa þ Epc)/2). The four redox peaks are similar to those of reported Dawson-type compounds, corresponding to sequential one-, one-, two, two-electron redox processes of W.14 Furthermore, the plot of peak III-III0 currents against scan rates (Figure S7, Supporting Information) displays that the peak currents are proportional to the scan rates, suggesting that the redox process is surface-controlled.15 In conclusion, a new POM-based porous framework with perovskite architecture has been successfully synthesized. This work suggests that the interpenetration of an independent porous framework could be prevented by modifying partial cages of the porous framework with various organic ligands. Further, the porous framework of 1 displays relatively high thermal-stability due to the introduction of organic ligands and initially exhibits absorption abilities to small solvent molecules. The successful synthesis of compound 1 may provide a new model for other porous materials based on a variety of POM units and TM ions. Acknowledgment. This work was supported by the National Natural Science Foundation of China (Nos. 20701005, 20901015), the Science and Technology Development Project Foundation of Jilin Province (No. 20080120), the Postdoctoral station Foundation of Ministry of Education (No. 20060200002), the Science and Technology Creation Foundation (NENU-STC07009), and Science Foundation for Young Teachers of Northeast Normal University (No. 20090406).
(1) (a) Seo, J. -S.; Whang, D.; Lee, H.; Jun, S. I.; Oh, J.; Jeon, Y. J.; Kim, K. Nature 2000, 404, 982. (b) Zhao, X.; Xiao, B.; Fletcher, A. J.; Thomas, K. M.; Bradshaw, D.; Rosseinsky, M. J. Science 2004, 306, 1012. (c) Kitaura, R.; Onoyama, G.; Sakamoto, H.; Matsuda, R.; Noro, S. I.; Kitagawa, S. Angew. Chem. 2004, 116, 2738. Angew. Chem., Int. Ed. 2004, 43, 2684. (d) Wu, C. D.; Hu, A.; Zhang, L.; Lin, W. J. J. Am. Chem. Soc. 2005, 127, 8940. (e) Dinca, M.; Long, J. R. J. Am. Chem. Soc. 2005, 127, 9376. (f) El-Kaderi, H. M.; Hunt, J. R.; MendozaCortes, J. L.; C^ote, A. P.; Taylor, R. E.; O'Keefe, M.; Yaghi, O. M. Science 2007, 316, 268. (g) Zhang, J.-P.; Chen, X.-M. J. Am. Chem. Soc. 2008, 131, 5516. (h) Guo, H.; Zhu, G.; Hewitt, I. J.; Qiu, S. J. Am. Chem. Soc. 2009, 131, 1646. (2) (a) Ockwig, N. W.; Delgado-Friedrichs, O.; O’Keeffe, M.; Yaghi, O. M. Acc. Chem. Res. 2005, 38, 176. (b) Ferey, G.; Mellot-Draznieks, C.; Serre, C.; Millange, F. Acc. Chem. Res. 2005, 38, 217. (c) Cheetham, A. K.; Rao, C. N. R.; Feller, R. K. Chem. Commun. 2006, 4780. (d) Perry, J. J., IV; Perman, J. A.; Zaworotko, M. J. Chem. Soc. Rev. 2009, 38, 1400. (3) (a) Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak, D.; Wachter, J.; O’Keeffe, M.; Yaghi, O. M. Science 2002, 295, 469. (b) Ferey, G.; Mellot-Draznieks, C.; Serre, C.; Millange, F.; Dutour, J.; Surble, S.; Margiolaki, I. Science 2005, 309, 2040. (c) Rosi, N. L.; Kim, J.; Eddaoudi, M.; Chen, B.; O'Keeffe, M.; Yaghi, O. M. J. Am. Chem. Soc. 2005, 127, 1504. (d) Wang, X. L.; Qin, C.; Wu, S. X.; Shao, K. Z.; Lan, Y. Q.; Wang, S.; Zhu, D. X.; Su, Z. M.; Wang, E. B. Angew, Chem. 2009, 121, 5395. Angew. Chem., Int. Ed. 2009, 48, 5291. (e) Tonigold, M.; Lu, Y.; Bredenk€otter, B.; Rieger, B.; Bahnm€uller, S.; Hitzbleck, J.; Langstein, G.; Volkmer, D. Angew, Chem. 2009, 121, 7682. Angew, Chem. Int. Ed. 2009, 48, 7546. (4) (a) Pope, M. T. Heteropoly and Isopoly Oxometalates; Springer: Berlin, 1983. (b) Hagrman, P. J.; Hagrman, D.; Zubieta, J. Angew. Chem. 1999, 111, 2798. Angew. Chem., Int. Ed. 1999, 38, 2638. (c) Hill, C. L., Ed. Special Issue on Polyoxometalates. Chem. Rev. 1998, 98, 1. (d) Long, D. L.; Burkholder, E.; Cronin, L. Chem. Soc. Rev. 2007, 36, 105. (e) Hao, J.; Xia, Y.; Wang, L.; Ruhlmann, L.; Zhu, Y.; Li, Q.; Yin, P.; Wei, Y.; Guo, H. Angew. Chem. 2008, 120, 2666. Angew. Chem., Int. Ed. 2008, 47, 2626. (f) Bassil, B. S.; Dickman, M. H.; R€omer, I.; Kammer, B.; Kortz, U. Angew. Chem. 2007, 119, 6305. Angew. Chem., Int. Ed. 2007, 46, 6192. (g) Zheng, S.-T.; Zhang, J.; Yang, G.-Y. Angew. Chem. 2008, 120, 3973. Angew. Chem., Int. Ed. 2008, 47, 3909. (5) (a) An, H. Y.; Wang, E. B.; Xiao, D. R.; Li, Y. G.; Su, Z. M.; Xu, L. Angew. Chem. 2006, 118, 918. An, H. Y.; Wang, E. B.; Xiao, D. R.; Li, Y. G.; Su, Z. M.; Xu, L. Angew. Chem., Int. Ed. 2006, 45, 904. (b) Han, J. W.; Hill, C. L. J. Am. Chem. Soc. 2007, 129, 15094. (c) Ritchie, C.; Streb, C.; Thiel, J.; Mitchell, S. G.; Miras, H. N.; Long, D.-L.; Boyd, T.; Peacock, R. D.; McGlone, T.; Cronin, L. Angew. Chem. 2008, 120, 6978. Angew. Chem., Int. Ed. 2008, 47, 6881. (d) Rodriguez-Albelo, L. M.; Ruiz-Salvador, A. R.; Sampieri, A.; Lewis, D. W.; Gomez, A.; Nohra, B.; Mialane, P.; Marrot, J.; Secheresse, F.; Mellot-Draznieks, C.; Biboum, R. N.; Keita, B.; Nadjo, L.; Dolbecq, A. J. Am. Chem. Soc. 2009, 133, 16078. (6) (a) Khan, M. I.; Yohannes, E.; Doedens, R. J. Angew. Chem. 1999, 111, 1374. Angew. Chem., Int. Ed. 1999, 38, 1292. (b) Wu, C.-D.; Lu, C.-Z.; Zhuang, H.-H.; Huang, J.-S. J. Am. Chem. Soc. 2002, 124, 3836. (c) Tripathi, A.; Hughbanks, T.; Clearfield, A. J. Am. Chem. Soc. 2003, 125, 10528. (d) Streb, C.; Ritchie, C.; Long, D.-L.; K€ogerler, P.; Cronin, L. Angew. Chem. 2007, 119, 7723. Angew. Chem., Int. Ed. 2007, 46, 7579. (e) Wang, C. L.; Liu, S. X.; Xie, L. H.; Ren, Y. H.; Liang, D. D.; Sun, C. Y.; Cheng, H. Y. Polyhedron 2007, 26, 3017. (f) Tan, H.; Li, Y.; Zhang, Z.; Qin, C.; Wang, X.; Wang, E.; Su, Z. J. Am. Chem. Soc. 2007, 129, 10066. (g) Li, Y. W.; Wang, Y. H.; Li, Y. G.; Wang, E. B.; Chen, W. L.; Wu, Q.; Shi, Q. Inorg. Chim. Acta 2009, 362, 1078. (7) The number of crystallized water molecules in the formula of 1 was established by elemental analysis and TG analysis. The elemental analysis found: C, 8.48; H, 1.94; N, 1.57% (calcd: C, 8.25; H, 1.81; N, 1.48%). The ICP analysis showed that 1 contained 58.95% W, 3.22% Ni and 1.18% P (calcd: W, 58.31; Ni, 3.10; P, 1.09%). The TG curve of 1 (Figure S8, Supporting Information) shows a total weight loss of 20.22% in the range of 46-685 °C, which agrees with
4230
Crystal Growth & Design, Vol. 10, No. 10, 2010
the calculated value of 19.99%. The weight loss of 9.64% at 46-320 °C corresponds to the loss of all crystallized water molecules and coordinated water molecules (calc. 9.52%). The weight loss of 10.58% at 340-685 °C arises from the loss of bpp ligands (calc. 10.47%). (8) A mixture of K6[R-P2W18O62] 3 19H2O (0.04 mmol), NiCl2 3 2H2O (0.25 mmol), bpp (0.2 mmol) and H2O (8 mL) was adjusted to approximate pH = 6 with the addition of 1 M NaOH. The resulting cloudy solution was stirred for 20 min in air, transferred to a 15 mL Teflon-lined autoclave and kept at 160 °C for 5 days. After slow cooling to room temperature, dark green cubic crystals of 1 were collected (yield: 65% based on W). IR (KBr pellet, ν/cm-1): 3394 (br), 1614 (s), 1558 (w), 1504 (w), 1425 (m), 1224 (w), 1081 (vs), 1025 (w), 948 (s), 881 (w), 784 (vs) and 520 (m) (Figure S9, Supporting Information). (9) Crystal data for 1: C39H102N6Ni3O92P2W18, Mr = 5674.64, cubic, Pm3n, a = b = c = 29.557(3) A˚. U = 25822(5) A˚3, Z = 8, F(000) = 18560. Fcalcd = 2.919 g cm-3, R1(wR2) = 0.0848 (0.2146) and S = 1.136 for 4049 reflections with I > 2σ(I ). The data were collected at 150(2) K on a Rigaku RAXIS RAPID IP diffractometer with monochromated Mo KR radiation (λ = 0.71073 A˚). The structure was solved by direct methods and refined using full-matrix least squares on F2. All calculations were performed using the SHELX97
Wang et al.
(10)
(11)
(12) (13) (14) (15)
program package. The hydrogen atoms attached to carbon atoms were fixed in calculated positions. CCDC 733909 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. (a) Tian, A.-X.; Ying, J.; Peng, J.; Sha, J.-Q.; Han, Z.-G.; Ma, J.-F.; Su, Z.-M.; Hu, N.-H.; Jia, H.-Q. Inorg. Chem. 2008, 47, 3274. (b) Sha, J.; Peng, J.; Lan, Y.; Su, Z.; Pang, H.; Tian, A.; Zhang, P.; Zhu, M. Inorg. Chem. 2008, 47, 5145. (c) Zhang, Z. M.; Li, Y. G.; Wang, Y. H.; Qi, Y. F.; Wang, E. B. Inorg. Chem. 2008, 47, 7615. (a) Jain, P.; Dalal, N. S.; Toby, B. H.; Kroto, H. W.; Cheetham, A. K. J. Am. Chem. Soc. 2008, 130, 10450–10451. (b) Rijnders, G.; Blank, D. H. A. Nature 2005, 433, 369. (c) Lee, H. N.; Christen, H. M.; Chisholm, M. F.; Rouleau, C. M.; Lowndes, D. H. Nature 2005, 433, 395. (a) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7. (b) Spek, A. L. PLATON, A Multipurpose Crystallographic Tool; Utrecht University: The Netherlands, 2006. (a) Kawamoto, R.; Uchida, S.; Mizuno, N. J. Am. Chem. Soc. 2005, 127, 10560. (b) Xue, M.; Zhu, G.; Ding, H.; Wu, L.; Zhao, X.; Jin, Z.; Qiu, S. Cryst. Growth Des. 2009, 9, 1481. Sadakane, M.; Steckhan, E. Chem. Rev. 1998, 98, 219. Cheng, L.; Zhang, X. M.; Xi, X. D.; Dong, S. J. J. Electroanal. Chem. 1996, 407, 97.
