7389
J. Phys. Chem. 1992,96, 7389-7393 (5) Ichikawa. M.: Sekizawa. K.: Kawai. M. J. Mol. C a r d 1982.11. 167. (6j Agnol, C; D.;Gervasini, A:; Morazzoni, F.; Pinna, F.; Strukul, G.; Zanderighi, L. J. Coral. 1985, 96, 106. (7) Mazzocchia. C.: Temuesti. E.; Gronchi, P.; Giuffre, L.; Zanderighi, - L. * J . i.aia/. 1988, iii, 345. (8) Guglielminotti, E. J. Caral. 1989, 120, 287. (9) Yashitake. H.;Iwasawa, Y., to be published.
(IO) Yashitake, H.;Iwasawa, Y., to be published.
(11) Sayers, D. A.; Stern, E. A,; Lytle, F. W. Phys. Rev. Lett. 1971, 35, 204. (12) Oyanagi, H.; Matsushita, T.; Ito, M.; Kuroda, H. KEK Rep. 1984, 83. Nomura, M. KEK Rep. 1985, 85. (13) Kasugi, N.; Kuroda, H.Program EXAFS2; Research Center for Spectrochemistry; The University of Tokyo, Tokyo; 1987.
(14) Teo, B. K. EXAFS Basic Principles and Data Analysis; Inorganic Chemistry Concepts 9; Springer-Verlag: Berlin, 1986. (15) Lytle, F. W.; Sayers, D. E.; Stern, E. A. Physica B 1989, 158, 701. (16) Tenfer, G. Acra Crysrallogr. 1962, 15, 1187. (17) Smith, D. K.; Newkirk, H. W. Acra Crystallogr. 1965, 18, 983. (18) Wyckoff, R. W. G. CrystalStructure;Wiley: New York, 1963; Vol. 1, p 240. (1 9) Bradley, D. C.; Thomton, R. In Comprehensive Inorganic Chemistry; Bailar, J. C., Emeleus, H. J., Nyholm, Sir R., Trotman-Dickenson, A. F., Eds.; Pergamon Press: New York, 1973. (20) Gravie, R. C. J. Phys. Chem. 1965,69, 1238. (21) Asakura, K.; Iwasawa, Y.; Purnell, S. K.; Watson, B. A,; Barteau, M.A.; Gates, B. C. Caral. Let?., to be submitted. (22) Waser, J. Acta Crysrallogr. 1953, 6, 661.
Intercalation of Polyoxycation Species into Conducting Layered Host Lattices of MOO, and TaS2 Anton Led: Erwin Lalik, Waclaw Kolodziejski, and Jacek Illinowski* Department of Chemistry, University of Cambridge, Lenrfield Road, Cambridge CB2 IEW, U.K. (Received: October 16, 1991; In Final Form: April 15, 1992)
Polyoxycations [A104A112(OH)24 ( H Z O ) ~ ~and ] ~ '[B&(OH)lz]6+ were introduced into highly crystalline MOO3 (space group Pnma) and 2H-TaSz (P6,lmmc) by ion exchanging the sodium forms of hydrated layered compounds. Interlayer spacing in MOO, increases from 6.97 to 18.1-18.9 A, more than would be expected from the sum of the spacing in the parent compound and the diameter of the All, polyoxycation. We suggest that the MOO, layers in the intercalated material are shifted with respect to one another, so that the terminal oxygen atoms of the MOO6 octahedra of adjacent layers point toward each other. The heat-treated material has a higher degree of stacking order, and it is clear that the Al13unit survives the heat treatment. z7AlMAS and 'H2N CP/MAS NMR spectra reveal that Merent environments for interstitial aluminum are simultaneously present in the sample. The [B~(OH)lz]6+ cation was introduced into a layered host lattice for the first time. The interlayer distance of the product is 13.8 A, in agreement with the largest oxygen-oxygen distance in the cation.
Introduction The insertion of pillaring species into the interlayer space of clay minerals has been the most promising event in intercalation chemistry in the last decade.' Because of their large internal pore systems, pillared clays are of considerable interest as molecular sieves and catalysts.' Pillared derivatives of some layered titanatesz4 and zirconium and tin phosphates1 have also been prepared. Pillaring of transition metal oxides and chalcogenides is also of interest. Mo03 is an important component of many industrial cataly~ts,~ but molybdena-based systems suffer from the disadvantage of a very low surface area. MOO,,a layered compound, is a potential host for inter~alation~.~ which may lead to new materials with the catalytic properties of bulk mixed oxides (such as bismuth molybdate) but with a high surface area. Layered dichalcogenides are catalysts8 and intercalation substrates? Pillaring of thest may lead to new preparation methods for sulfide catalysts, in addition to the usual impregnation of the oxide support. Since 2H-TaSz forms a stable hydrated sodium intercalation compound with known properties, we began by pillaring this material. Applications of semiconducting oxides as chemical sensors are still far fewer then their applications as catalysts. The common feature of a catalyst and a chemical sensor is the charge transfer process occurring during chemisorption, and pillared crystals of conducting materials such as MOO, or TaSz may combine the catalytic and conducting properties to lead to a new type of sensor. It is thus imperative to investigate the viability of pillaring large single crystals. The most widely used pillaring polyoxycation is [A104 All2(OH)24 (H20)1J7+, isostructural with the so-called Keggin unit, and preparedvia hydrolysis of AI salts.'@'' A gallium analogue,'2l3 ' O n leave from the Walther-Meiarner-Institut, 8046 arching, Germany.
0022-365419212096-7389$03.00/0
[Ga04Galz(0H)z4(Hz0)1z]7+,and a mixed [Ga04Allz(OH)24 ( H z O ) ~ ~ polyoxycation ]~' were recently reported.13J4 The intercalation of the Al13and Ga13polyoxycations into MOO, via f l d a t i o n from the colloidal solution of the bronze has recently been des~ribed.'~From among many other polyoxycations reported to exist in solution, the [ B ~ S ( O H ) ~cation16 ~ ] ~ + is interesting in connection with molybdenum trioxlde, with a view to the preparation of a pillared counterpart of bismuth molybdate. This ion has not previously been used as a pillaring agent. We report a successful insertion of [A104 Al12(OH)24 (HzO)12]7+and [Bi6(0H)1z]6+ into highly crystalline Mo03 and 2H-TaSz by ion exchange with sodium forms of hydrated layered compounds.
Experimental Section Two kinds of MOO, parent material were used for intercalation: as supplied by Koch-Light, and recrystallized by heating as-received MOO, at 500 OC for 24 h in a flow of oxygen. 2H-TaSz was prepared by the vapor transport method using iodine as the transport agent at 900 OC and by subsequent annealing. Sodium form of the molybdenum bronze was prepared by soaking MoO, in an aqueous solution of Na2Mo04and Na&O4 according to Thomas and M ~ C a r r o n . The ~ X-ray diffraction (XRD) pattern of the as-prepared material is in agreement with that given in the original report, iving the interlayer distance in the fully hydrated state of 11.5 . TaSz was intercalated with Na+ by treating the solid with 1 M aqueous NaOH for 16 h,I7 which resulted in the increase of the interlayer distance from 6.1 to 11.8 A. A solution of the All, polyoxycation (0.1 mol/dm3 in Al) was prepared by dissolving powdered aluminum chlorohydrate (ACH) (Reheis Chemical; 47% of A1203)in water and aging at 80 OC for 2 h.3 The Bi polyoxycation was made by dissolving Bi203 in an equivalent amount of concentrated HC1O4.l8 Intercalation of the polyoxycations was carried out via ion exchange of sodium ions in freshly prepared NaozS(HzO),MOO3 and Nao,33(Hz0),TaSz. The solids were treated with an excess
1
0 1992 American Chemical Society
7390 The Journal of Physical Chemistry, Vol. 96, No. 18, 1992 TABLE I: Indexing of the XRD Pattern for As-Prepared Allr-Interclll.ted MOOZeal/ ZOO, hkl Zeal/ 26,, 4.87 4.66 010 33.63 34.65 34.50 9.76 9.50 020 34.64 14.66 14.46 030 34.73 19.59 19.46 040 38.47 38.30 22.63 22.77 100 39.79 39.70 23.16 23.28 110 45.02 45.00 24.56 24.54 050 45.09 45.30 24.55 24.62 011 46.26 46.40 27.06 26.80 130 46.47 28.28 27.90 031 47.32 47.30 29.57 29.66 060 48.71 48.70 30.10 140 3 1.20 04 1 48.78 54.84 54.70 33.64 33.70 150
Lerf et al.
hkl 111 007 05 1 121 061 080 090 161 180 210 220 230 171 102
600°C
"Calculated for the unit cell with II = 3.93 A (as in Moo3),b = 18.1
A, c = 3.701 A (as in Moo3).
h
of aqueous solutions of the metal polyoxycations for 48 h at room temperature. Heat treatments were carried out for 1-2 h in a flow of helium or in vacuum at different temperatures up to 600 OC. After individual preparation steps all samples were examined by XRD using Ni-filtered Cu Ka radiation. In most cases only reflections from planes parallel to the layers (OM) for M a 3 and 001 for TaS2) could be observed. In the case of All3 ylyoxycations in MOO3of small particle size, it was possible to rrrrmrmze the effects of preferential crystal orientation in XRD patterns. Mixed reflections observed as a result allowed the patterns to be fully indexed. 27AlNMR Bloch decays were recorded on a Bruker MSL-400 spectrometer at 104.26 MHz with very short, 0.7 ps (less than 1O O ) , radiofrequency pulses and 0.5s recycle delays. Zirconia rotors 4 mm in diameter were spun in nitrogen with magic angle spinning (MAS) at 16 kHz. The magic angle was set precisely by observing the 79Brresonance of KBr.I9 1H-27AlCP/MAS spectraZowere recorded with a single contact, a contact time of 500 ps, a 'H 90° pulse of 3.4 ps, a recycle delay of 5 s, and a spinning rate of 7 kHz. The Hartmann-Hahn condition was established in one scan on a sample of pure and highly-crystalline kaolinite using similar acquisition parameters. Because only the central (-1/2 *-, +1/2) transition is observed, excitation is selective and therefore the Hartmann-Hahn condition is
.-cv) E a
F
E
e
Y
.-e> v) C
m
-C c
= rHBH where yAI and yH denote the gyromagnetic ratios of 27Aland IH and B is the radiofrequency field strength. 3YAIBAI
Molybdenum bronze intercalated
1
Results and Discussion Mo03 Intercalated with the AIl3 Polyoxycation. Parts a and b of Figure 1 show the XRD patterns of the as-prepared samples starting with different MOO, precursors. The significant increase of the interlayer spacing in comparison with that in the hydrated sodium bronze indicates the uptake of the polyoxycation. The interlayer distance, as calculated from nine O M ) reflections, decreases from 18.9 A for 010 to 18.1 A for 090, which indicates the presence of stacking faults.21 The limiting value of 18.1 A is slightly higher than that given in ref 15, although the intensity variation of reflections with increasing k in O M ) is in good agreement with that described. Also, the interlayer spacing of 18.1 A is larger than would be expected from the sum of the spacing in unpillared Moo3 (6.97 A, space roup Pnma) and the diameter of the AIl3polyoxycation of ca. 9 .2z We suggest that the M a 3 layers are shifted, so that the terminal oxygen atoms of the Moo6 octahedra of adjacent layers point toward each other (Figure 2b), while in the starting material they point toward the space between the M a s octahedra of the neighboring layers (Figure 2a).23 Thus in the case of Al13-intercalatedbronze we expect only one MOO3layer per unit cell instead of two as in M a 3 and in the sodium bronze. The indexing of the XRD patterns (Figure l b and Table I) supports this conclusion.
1
0
10
20
with AI Keggin ion as prepared
30
40
50
20 (degrees) Figure 1. X-ray diffraction patterns of molybdenum bronze intercalated with the [AIO,AI,2(OH)U (H20)12]7'Keggin-like unit: (a) as-prepared, (b) as-prepared (fmely crystalline sample); (c) after heating to 100 " C ; (d) after heating to 100 "C and then to 350 "C; (e) after heating to 400 "C; (f) after heating to 600 "C.
Figure l e f shows XRD patterns taken after step-by-step heat treatments of the samples (starting from the recrystallized MOO3) under helium flow. The intensity of the refections decreases and their width increases with increasing temperature. At 100 OC the interlayer distance changes only slightly from 18.1 to 18.05 A. However, in contrast to the as-made sample, the interlayer distance does not depend on k in O M ) , indicating a higher degree of stacking order in the heat-treated material. As many as nine OkO reflections can still be observed (Figure IC). Upon further heating the interlayer distance decreases to 17.7 A, while only
The Journal of Physical Chemistry, Vol. 96, No. 18, 1992 7391
Intercalation of Polyoxycation Species
bt
18,'l Intercalated K q p i n cations
I
Intercalated Keggin cations
I
s,
Figwe 2. (a) In the parent MoOo the terminal oxygen atoms of the MoOdoctahedra of adjacent layers point toward the space between the MoOs octahedra of the neighboring layers. (b) In the proposed stacking of the layers of octahedra in the intercalated material, the layers are shifted with respect to one another, so that the terminal oxygen atoms of the MoO, octahedra of adjacent layers point toward each other.
two OkO reflections remain (Figure Id). Prolonged drying in vacuum at room temperature has a similar effect as heating to 200 "C under helium. When the sample is heat-treated at 200 OC under vacuum, the interlayer distance decreases to 15.2 A, in agreement with ref 15. It follows that the interlayer distance is strongly dependent on temperature, duration and conditions of treatment (whether or not under vacuum). After heat treatment at 400 OC we can observe only very broad XRD peaks with no obvious relation to those from the parent compound (Figure le). Rewetting of the 400 OC sample results in the reappearance of a sharp peak corresponding to the interlayer spacing of 15.4 A, which indicates that the polyoxycation survives the heat treatment. Further heating to 600 OC (Figure If')leads to the formation of highly crystalline A12(Mo04)3.24 The pH of the pillaring solution is known to influence the pillaring process. The effect is particularly significant in molybdenum bronze, because of its relatively high solubility in water. Samples of N~.zS(HzO)yMo03 bronze must be washed upon the completion of synthesis, and contact with distiled water leads to a loss of material which could be avoided if the solution of sodium molybdate (which is used as a buffer in this synthesis in any case) were used instead. However, the solution of sodium molybdate is basic and must not be present during the addition of the All3 cation, as this would lead to the precipitation of Al(OH)3 and the consequent failure of intercalation. Distilled water might be
ultimately used in order to wash out the remains of sodium molybdate from the bronze precipitate. As an alternative, we used dilute HCl to neutralize the supernatant solution. The interlayer spacing of products from both procedures (rinsing of Mo bronze with water versus rinsing with a solution of sodium molybdate followed by neutralization with acid) is very slightly lower for the 'acidic" sample, and closer to that quoted in ref 15. XRD patterns of both samples at up to 350 "C are identical, but in the "acidic" sample the formation of crystalline aluminum molybdate occurs at a lower temperature of 400 OC. Figure 3 shows 27AlMAS NMR spectra of the 'acidic" samples taken immediately after preparation and after successive heat treatments. The 27Alspectrum of the as-prepared sample (Figures 3a and 4a shows one signal at 64 ppm corresponding to 4-coordinated A1 and a broad signal with the maximum at ca. 0 ppm, due to 6-coordinated Al. These general features are similar to those of the spectra of AlI3intercalated into clays and t i t a n a t e ~ ~ s ~ ~ and are in agreement with the spectra of All3 polyoxycations in solution at 80 O c a z 6 The presence of the shoulder at ca. -73 ppm, which is not a spinning sideband, on the low-frequency side of the signal from 6-coordinated A1 shows that this signal has a quadrupole powder pattern. Superimposed on this is a very sharp peak at -0.2 ppm (Figure 4a) which, in view of its chemical shift, we assign to Al(HzO),3+cointercalated with the AlI3units. These cations are highly mobile, and so the 'Hd7Al cross-polarization does not work in this case (Figure 4b). However, two other features are revealed in C P / M M spectra (Figure 4b): the peaks at 10.6 and 14.3 ppm, which show that the signal from 6-coordinated A1 is a composite. The corresponding A1 sites are less mobile than Al(HzO)63+, and their environment probably differs as regards the number and disposition of protons. These peaks can be also seen in the expanded version of the MAS spectrum (Figure 4a). The signal from 4-coordinated A1 gradually broadens with increasing temperature (Figure 3b-e) and at 350 OC becomes a shoulder. The signal from &coordinated Al changes its shape and shifts slightly to lower frequency, possibly as a result of redistribution of intensity among its components. At 400 OC a very sharp new signal appears at -14.7 ppm (Figure 3f), which we assign to the single 6-coordinated A1 site in A12(Md4)3. CP/ MAS spectra show that heating of the sample to 100 OC drives many protons away, and the sharp signals in Figure 4b are much less resolved (Figure 4c). The disappearance of the signal at 14.3 ppm suggests that the corresponding Al sites either are more prone to lose protons or are becoming mobile, being p u m a b l y detached from the bulk of the All3 cation. The pillaring solution may contain lower A1 oligomers apart from AlI3. The question therefore arises whether their presence affects the intercalation and the thermal stability of the product. The nature of these oligomers depends on the method of preparation (dissolved ACH) or direct hydrolysis of AlC13with NaOH or NazC03)and also on the concentration of the solution and its history. It is well-known that the ACH solution usually contains species other than the A l l 3 cation which too appears when directly hydrolyzed AlC13 is aged. Yet, the hydrolyzed AlC13 may be a source of only Al13polyoxycationswhen sufficiently dilute (0.02 mol/dm3). We applied such dilute solution (OH/Al= 2.0) and compared the resulting intercalate with that prepared from aluminum chlorohydrate. Both intercalates show remarkably similar XRD patterns, independently on the manner of preparation, and their thermal stability is also the same. We conclude that the All3 is cation involved in both cases. We measured 27AlNMR spectra of both pillaring solutions (not shown). For ACH, the All3 cation (giving a sharp signal at 63.3 ppm) and Al(HzO)63+(at 0.7 ppm) are not alone in the solution. Two broad signals at 7 1.4 ppm and 11 ppm are also observed, while only signals from AIl3and Al(HzO)63+are found in hydrolyzed AlC13. However, a broad resonance at 71.4 ppm in the spectrum of liquid ACH is not observed in the intercalate (Figwes 3 and sa). It follows that only some of the oligomers lower than All3, if any, are actually introduced into the interlayer space of M a 3 . It is likely that the high charge of All?+ enables this cation
Lerf et al.
7392 The Journal of Physical Chemistry, Vol. 96, No. 18, 1992
CP / MAS at 7.6 kH 100°C
CP I MAS at 7.2 kHz as prepared
I
100
50
0
-50
-100
ppm from AI(H,o),~+ Elgure 4. (a) 27Al MAS and (b) lHd7Al CP/MAS spectra of the
as-prepared intercalate; (c) 'HA7Al CP/MAS spectrum of the sample heated at 100 OC. c
100°C
as prepared
200
100
b
-1bo
-200
ppm from AI(H20),3+ Figure 3. 27AIMAS NMR spectra of molybdenum bronze intercalated with the Al Keggin-like unit: (a) as-preapred, (b) after heating to 100 OC; (c) after heating to 200 O C ; (d) after heating to 300 "C; (e) after heating to 350 OC; (f) after heating to 400 OC.
to win the ionexchange competition. We are at present attempting to establish the precise nature of aluminum in Mo03 intercalates using quadrupole nutation NMR. Moo3 Intercalation with the Bi Polyoxycation. Figure Sa demonstrates the first successful intercalation ofthe [B&(OH)12]6+ cation in a layered host lattice. This is indicated by the increase in the interlayer distance to 13.8 A (seven O M ) reflections), in agreement with the largest oxygen-oxygen distance in the [Bi6(OH)12]6+cation of 6.5 A.16 The crystallinity of the Bi intercalate is lower than that of Al-intercalated molybdena and only the first, very weak OM) reflection remains after heating at 100 OC for 1
h in helium. The XRD pattern of the sample calcined for 1 h at 300 OC in helium (Figure Sb) shows only one very broad peak at ca. 30° 28. Further heating at 500 O C (Figure Sc) leads to the formation of a-bumuth molybdate, Bi2(Mo04)3?4Elemental analysis of the uncalcined material shows an unexpectedly large amount of bismuth (Mo/Bi = 1). Taking into account the layer charge in molybdenum bronze (0.25 of a positive charge per Mo atom) and the charge of the interdated BkH, one would estimate the Bi content to be much lower, with Mo/Bi = 4. The discrepancy indicates that the charge of the intercalated polyoxycations is lower than 6+, presumably as a result of further hydrolysis [&(oH)12]~++ nHzO = [Bi6(0H)12+,](6-")+ nH+ (1) proceeding between the layers of the host lattice. In doing this, the Bi6 species resembles the AI13 unit, the effective charge of which is considered by some authors2' to be 4+ rather than 7+. However, in the case of Bi species, the degree of hydrolysis must be much higher, as the effective charge corresponding to Mo/Bi = 1 is 1.5+, corresponding to n = 5 in eq 1, and indicating decomposition rather than hydrolysis. This may explain the poorer crystallinity of Bi6-intercalated M o 0 3 in comparison with the Al13-intercalatedmaterial. "mal Stability of Pibred MOO3. Thermal stability of pillared layered structures may be controlled by the stability of either the layer or the pillar. In our experiments, all of the AlI3-, Al13/Ga13-,GaAIl2-,and Be-pillared molybdena systems failed to withstand temperatures higher than 400 OC. This temperature
+
Intercalation of Polyoxycation Species
The Journal of Physical Chemistry, Vol. 96, No. 18, 1992 7393
3
E
13
18
23
28
33
38
43
48
53
58
28 (degrees)
Figure 6. X-ray diffraction pattern of as-prepred 2H-TaS, intercalated with the A1 Keggin-like unit.
I
f
l
3
8
13
18
23
28
33
38
43
48
53
58
28 (degrees)
Figure 5. X-ray diffraction patterns of molybdenum bronze intercalated with [Bk(OH)12]6+ions: (a) as-prepared; (b) after heating to 300 OC; (c) after heating to 300 O C and then to 500 OC.
is particularly significant, since it is often found that the mobility of atoms in the Moo3 crystal lattice increases rapidly at about 400 OC.= Indeed, this is the temperature at which the formation of molybdates begins. Therefore, not only the stability of the pillar but also the high mobility of atoms in the oxide lattice determines the thermal behavior of pillared molybdena. This is in contrast to the behavior of pillared clays whose thermal stability is thought to be controlled by the sintering of the pillar.27 Interclhtioaof the AlI5 Polyoxyatioa into 2H-Tps2. Figure 6 shows the XRD pattern of N~.33(H20)yTaSP after treatment with the All3 unit. The interlayer distance increases to 15.8 A (ten 001 reflections), and layer stacking appears unchanged. In contrast to the molybdenum bronze, the layer separation of 9.75 A is in reasonable agreement with the diameter of the A113 polyoxycation.22 This value is higher than the layer distances observed for the intercalation of single hydrated metal cations into 2H-TaS229indicating the uptake of the AI13 unit and not of the AI(H20),’+ cation. A small amount (less than 10%) of deintercalated TaS2 present is due to partial reoxidation of the host compound. Afier drying in vacuum at room temperature the layer distance decreases to ca. 14.5 A, the reflections become broader (only two 001 reflections are clearly visible), and the amount of nonintercalated TaS2 increases. An attempt to intercalate 2HTaS2from the hydrolyzed AIC13 solutions (0.02 mol/dm3; AI/OH = 2.5 and 0.1 mol/dm3; AI/OH = 2.0), instead from the ACH, appeared to be unsuccessful. Surprisingly, there occurs the intercalation from an unhydrolyzed AIC13 solution (0.1 mol/dm3 without any addition of NaOH) resulting in two coexisting phases with interlayer distances of 11.65 and 15.8 A. Since the interlayer distance of 11.65 A is what one would expect for hydrated trivalent cations, it f d o w that the componding phase is intercalated with Al(H20)63+cations. The value of 15.8 A is identical to the interlayer distance in the material intercalated from the chlorohydrate solution. Therefore, the second phase appears to be the already known Al13 intercalated 2H-TaS2. The entire XRD pattern can be indexed (based on 2H layer stacking) which in-
dicates the complete exchange of sodium. Therefore, the total exchange of sodium with AI(H20)a3+and A l l 3 can proceed from the solution which does not contain Na’, even if the concentration of the intercalant is very low. We suggest that the 2-fold excess of Na+ cations in the solution prevents the interlayer sodium from being exchanged. Such a behavior of the sulfide is in contrast to that of the clays and the molybdenum bronze, where the exchange of sodium cations with AI1?+ is easy. In the case of clays, the metal cations already intercalated can be transformed into polyoxycations by raising the pH of the supernatant solution.’ We failed, however, to transform ‘in situ” Ai(HzO)d+ cations in the 11.65-A phase into A113cations by increasing the pH of the supernatant solution. Investigations of the sorptive and catalytic properties of the newly prepared materials are in progrras. Acknowledgment. We are grateful to Shell Research, Amsterdam, for support, Dr.J. Rocha for discussions, and to Professor K. Andres for his interest in this work. Resirtry No. A12(Mo04)3, 15123-80-5; Bi2(Mo04)3, 13595-85-2.
References and Notes (1) Mitchell, I. V. Pillared Layered Structures; Elsevier: Amsterdam, 1990. (2) Cheng, S.; Wang, T. Inorg. Chem. 1989.28, 1283. (3) Anderson. M. W.: Klinowski. J. I n o m Chem. 1990.29. 3261. (4) Landis, hi. E.;Aufdembrink,‘B. A,; Ehu, P.; Johnson, I. D.;kirker, G. W.; Rubin, M. K. J. Am. Chem. Soc. 1991,113, 3189. (5) Haber, J. J. Mol. Coral. 1989, 54, 370. (6) Schoellhorn, R.; Kuhlmann, R.; Besenhard, J. 0. Mater. Res. BUN. 1976. 11. 83. (7) Thomas, D. M.; McCarron 111, E. M. Mater. Res. Bull. 1986,21,945. (8) Grange, P. Catal. Rev.-Sei. Eng. 1980, 21, 135. (9) Whittingham, M. S.;Jacobson, A. J. Intercalation Chemistry; Academic Press: New York, 1982. (10) Pinnavaia, T.J.;Tzou, M.-S.; Landau, S. D.; Rayathatha, R. H. J . Mol. Caul. 1984, 27, 195. (1 1) Lahav, N.; Shani, U.; Shabtai, J. Clays Clay Miner. 1978,26, 107. (12) Bradley, S. M.; Kydd. R. A.: Yamdaani. R. J . Chem. Soc.. Dalton Trans..1990,4i3; 1990,2653. (13) Bradley, S. M.; Kydd, R. A. Caral. Lett. 1991,8, 185. (14) Gonzales, F.; Pquera, C.; &nito, I.; Maendioroz, S. J . Chem. Soc., Chem. Commun. 1991, 587. (15) Nazar, L. F.;Liblong, S. W.; Yin, X. T. J . Am. Chem. Soc. 1991, 113, 5889. (16) Levy, H. A.; Danford, M. D.; Agron, P. A. J. Chem. Phys. 1%9,31, 1458. (17) Biberacher, W.; Lerf, A.; Buheitl, F.; Butz, T.; Huebler, A. Mater. Res. Bull. 1982, 17, 633. (18) Holmberg, R. W.; Kraus, K. A.; Johnson, J. S. J . Am. Chem. Soc.
-
1956, 78, 5506.
(19) Frye, J. S.; Macicl, G. E. J. Magn. Reson. 1982, 125, 48. (20) (a) Blackwell, C. S.; Patton, R. L. J . Phys. Chem. 1984, 88, 6135. (b) Morris, D. H.; Ellis, P. J. Am. Chem. Soc. 1989, I l l , 6045. (c) Rocha, J.; Liu, X.; Klinowski, J. Chem. Phys. k t t . 1991, 182, 531. (21) Brindley, G. W., Brown, G., Ed. CrystalStructures of Clay Minerals and Their X-Ray Identificafion;Mineralogical Society: London, 1980. (22) Rausch, W.V.;Bale, H. D. J . Chem. Phys. 1964,40, 3391. (23) Andersson, G.; Magnbli, A. Acta Chem. S c a d . 1950.4, 793. (24) JCPDS International Centre for Diffraction Data, 1988. (25) Plet, D.; Borg, F.; Gatineau,L.; Fripiat, J. J. J. Am. Chem. Soc. 1985, 107, 2362. (26) (a) Akitt, J. W.; Mann, E. E. J . Magn. Reson. 1981, 44, 584. (b) Thompson,A. R.; Kunwar, A. C.; Gutowski, H. S.;Oldfield,E. J . Chem. Soc., Dalton Trans. 1987, 2317. (27) Figueraz. F. Card. Reu.-Sci. Eng. 1988, 30 (3), 457. (28) See for example: Gai, P. L. Philos. Mag. A 1981, 13, 841. (29) Lerf, A. Habilitationsschrvt, Munchen 1991.
