4677
J . Phys. Chem. 1994, 98, 46174682
Raman Spectra of the Unidimensional Aluminophosphate Molecular Sieves AlP04-11, A1Po4-5, AlP04-8, and VPI-5 Andrew J. Holmes,' Scott J. Kirkby, Geoffrey A. Ozin,' and David Young Advanced Zeolite Materials Science Group, Lash Millet Chemical Laboratories, University of Toronto, 80 Si. George Street, Toronto, Ontario, M5S lA1, Canada Received: January 24, 1994e
Laser Raman scattering spectra of the unidimensional molecular sieves AlP04-11, AlP04-5 (with and without Pr3N template), AlP04-8, and VPI-5 are reported. The lattice deformation region, ca. 300-500 cm-1, was observed to become increasingly complex as the contents of the Bravais cell increased and the factor group symmetry was reduced. Bands at ca. 400 and ca. 500cm-l, absent in the Raman spectrum of a-AlP04 (berlinite), were attributed to the presence of four T-atom rings in the above molecular sieve structures. Bands a t ca. 260-310 cm-l were ascribed to "pore-breathing" framework vibrational modes. The frequency (v) of these bands displayed a linear relationship of v2 a cos 8, where 8 is dependent on the average AI-0-P angle around the unidimensional channel of each of these molecular sieve materials.
Introduction Raman scattering studies of aluminosilicate molecular sieves (zeolites) have yielded a great deal of information on the framework vibrations of these materials and have provided empirical correlations between framework vibrational modes (lattice phonons) and the presence of discrete structural Understanding of the dynamical processes underpinning these correlations has advanced in recent years. Deckman and coworkers have made considerable progress modelling zeolites both as tetrahedrally bonded amorphous solids and as periodic lattices.9-ll This work has given insight into the true nature of experimentally observed Raman shifts with changing AI-0-Si, or Si-0-Si, angle. Obtaining zeolite Raman spectra displaying a good signal-to-noise ratio presents a considerable challenge, largely due to the poor cross section for the inelastic scattering process in aluminosilicates and the pesence of obscuring background fluorescence.'J2 The intensity of this background, which has been related to the zeolite acid strength, can be minimized with careful sample handling; however, each successive postsynthetic treatment leads to an increased background signa1.I3J4 Despite these problems, the increasing maturity of the field of zeolite Raman spectroscopy has been reflected in recent publications detailing the creative use of this method to quantify acidic sites via resonance techniques,l3 evaluate zeolite-sorbate interactionslsJ6 and different silica sources for faujastie synthesis,17 study clathrasil single crystals,18 and monitor the synthesis of zeolites A,19,20 Y,21 and ZSM-5.22323 With the advantages of Raman as a spectroscopic tool in zeolite chemistry now apparent, it seems appropriate that application of the technique should be extended to other molecular sieve materials. Recently, a spectrum was reported for the aluminophosphate extra-largepore material VPI-Pand we have reported Raman studies of the gallophosphate molecular sieve cloverite.25 In this paper, we present a spectroscopic study of a series of four aluminophosphate molecular sieves having unidimensional channel systems, namely AlP04-11,AlP04-5, AlP04-8, and VPI5. These materials, which are constructed primarily of six and four tetrahedral atom (T-atom) rings in particular sequences, have 10,12,14,and 18 T-atomstraight channels, with thechannel walls lined exclusively by six T-atom rings.2G29 (In the AlP04-n materials there is a strict alternation of Al"' and Pv T-atoms, each of which are separated by a bridging oxygen.) CHEM-X t Present address: Shell Research Ltd., Thornton Research Centre, P.O.
Box 1, Chester, CHI 3SH, England, UK.
* Abstract
published in Advance ACS Abstracts, March 15, 1994.
0022-3654f 94f 2O98-4611$Q4.50f 0
TABLE 1: Synthesis Parameters for the heparation of the
Studied AIPOd-BasedMolecular Sieves ~~
material VPI-5 AIP04-8 AlP04-5 AlP04-11
~
~~
gel conditions P~~NH:A~ZO~:PZO~:~OHZO 142 "C, 2 h prepared from VP1-5 125 "C, 16 h 1.SPr3N:A1203:P~O5:40HzO 150 "C, 12 h Pr2NH:A1203:P205:40H20 200 "C,24 h
representations of each of these aluminophosphate-based framework topologies, generated from literature atomic c~rdinates,2~29 are shown in Figure 1. These materials were chosen because of their high degree of structural similarity in the two dimensions perpendicular to the channel network, as well as their unidimensional channel systems.
Experimental Section AlP04-11, AlP04-5, and VPI-5 were hydrothermally synthesized according to methods outlined in the literature.30J' AlP04-8 WaspreparedbyheatingtheVPI-Sat125 OCfor 16 h. Asummary of experimental details of the crystallizations is outline in Table 1. Syntheses were conducted in 14 mL capacity stainless steel/ PTFE reactors, designed and built in-house. Products were recovered by a multiple wash/decant technique prior to filtration. The crystallinity, purity, and composition of the products were confirmed via powder X-ray diffraction (pXRD), scanning electron microscopy (SEM), and energy-dispersive X-ray microanalysis (EDX), in conjunction with SEM. Portions of the product AlPO4-11 and Alp@-5 molecular sieves were calcined in a shallow bed a t 600 OC over air; again crystallinity was confirmed by pXRD. Raman spectra were obtained under ambient conditions on a Ramanor UlOOO spectrometer (Instruments S.A.), equipped with a double monochromator (Jobin-Yvon,f= 1.0 m). An Ar+ ion laser (Coherent Innova 90, X = 514.5 nm), capable of delivering up to 400 mW a t the sample, was employed. The laser plasma lines were removed using a monochromator (Spex 1460,f= 0.14 m). The sample was loaded as a powder in a glass capillary tube and mounted on an xyz translation stage for examination. Data were collected and baseline corrected using a proprietary software package (Instruments SA., U505.85.910), then plotted using an in-house program.
Synthesis Results Prior to the Raman spectroscopic analysis of the chosen materials it was important that their high quality be confirmed, 0 1994 American Chemical Society
4618 The Journal of Physical Chemistry, Vol. 98. No. 17, 1994
Holmes e1 al.
Figure 1. CHEM-X representations of the framework topologies of (a) AIP04-II, (b) AIP04-5, (c) AIP04-8, and (d) VPI-5 .to3 1 IO
.!Dl 1 "0
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F i y n 2. Expcrimentai powder X-ray diffraction (pXRD) patterns of (a) AIPO4-I I, (b) AIPOr5, (c) AIPOa-8, and (d) VPIJ.
inorder tominimizeanyspectralerrorfromextraneousamorphous orcrystallineimpurities (for example, AlP04-tridymiteorAlPO4-
H3). Powder X-ray diffraction patterns of each of the synthesized aluminophosphatematerials are shown in Figure 2. The pXRD t r a m indicate pure crystalline phases for each product, when
compared to simulated and published pXRD data,'"' with amorphous impurities kept to a minimum. Scanning electron micrographs (see Figure 3) show AIPO,-ll as polycrystalline aggregates, AIPO4-5 as mosaical spherical crystallites, AIPO4-8 as irregular aggregates, and VPI-5 with its typical "wheatsheaf" morphology. EDX data revealed the expected AI/P ratio of 1.O
Raman Spectra Unidimensional AlP04 Sieves
The Journal of Physical Chemistry. Vol. 98, No. 17. 1994 4619
Figure 3. Scanning electron micrographs (SEMs) of (a) AIPO,-Il, (b) AIFQ-5, (c) AIP0,-8, and (d) VPI-5.
*
0.02 for each material and were calibrated against an AlP04tridymite standard. Raman Spectra of As-Synthesized and Calcined AlPOr5 Raman spectra of P q N , as-synthesized Pr,N-AIP04-5, and calcined A1P04-5 are presented in Figure 4. Under ambient conditions, we were able to obtain good quality data from these materialsdown to IOOcm-l,andoften tobelow 5Ocn-1, following lengthy exposure to the laser beam in order to ‘burn out” interfering background luminescence. This type of background is commonly encountered when dealing with aluminosilicate zeolites, for which a similar “burn out” procedure may also be used. Recently, the intensity of this luminescence has been correlated with the acidity of the zeolite framework.”J4 In the case of AIP04-5, calcination was found to significantly increase the background intensity. This parallels the behavior for zeolites, where any postsyntheticthermal treatment results in an increase in luminescent intensity. Such a treatment increases thenumber of hydroxyl defects in the framework (from insertion of water into the T-0-T linkage, giving two hydroxyls), which appear to be linked to this emission. The structure observed in the spectra shown in Figure 4 can he interpreted with reference to the Raman spectra of neat Pr3N and that of a-AIP04 (berlinite), the latter being the aluminophosphate analogue of a-q~artz.’”~ The a-AIP04 framework is composed entirely of linked six T-atom rings. The as-synthesizedPr3N-AIP04-5 material shows the definite presence of PrlN, with molecular organic modes at 1457 and 723-965 cn-’ (see Figure 4b). The template modes are clearly absent in the calcined material, thereby identifying which modes belong to the template and the framework. There is a strong framework band at ca. 1113 c n - I for hotb as-synthesized and calcined materials. This falls within the rangeof the overlapping AI and E modes of be11inite.l”~ There is a common band at 498 cm-l for the AIP04-5 sieves that is not found in berlinite. It has been reported that IR bandsin therange475-45Ocm-lcorrespond to aluminopbosphate sieves having four and six T-atom rings.” We thereforesuggest that this extra band in theRaman spectrum of AlPO4-5, absent in that of a-AIP04 (berlinite), arises from deformations of the four T-atom rings. Recent work, see later, suggeststhat the band at 259 and 267 cm-1 for the as-synthesized and calcined material, respectively, corresponds to a breathing mode of the sieve channel opening. This is in agreement with results found for aluminosilicates.” That there should he minor differences in the framework modes between the as-synthesized and calcined materials may be rationalized on the basis of the structural changes (unit cell parameters, and bond lengths and angles), observed by previous workers between as-synthesized and calcined A1P04-5.’*
Raman Spectra of Unidimensional AIPO, Moleeuhr Sieves The Raman spectra of AlP04-l 1, AIP04-S,AIP04-8,and VPI-5 each display a number of hands in the range 1 W 1 2 4 0 cm-I; see Figure 5 . The most intense vibrational modes for each of these materials are summarized in Table 2. In the Raman study of AIP04-5 outlined above, we identified distinct spectral regions within this range corresponding to framework lattice modes. In comparison with u-AIP04, bands possibly indicative of the presence of four membered T-atom rings were Observed, along with modes assignedto tripropylamineorganic template molecules. For the present study, VPI-5 and A1P04-8were synthesized with negligible amounts of occluded organic species in their frameworks, a useful aid to the identification and interpretation of their latticevibrational modes. Raman spectra weresuuxssfully collected for the as-synthesized (organic-free) VPI-5 and AIPO48, as well as for the as-synthesized and calcined AIPO4-5. However, thecalcined AIPO-I1 strongly fluoresced when it was irradiated with the AI+ ion laser, the intensity of which generally dwarfed that from the Raman scattering from the molecular sieve framework. This effect has also been observed in zeolites and, to a lesser extent, for AIP04-5, where thermal treatment results in framework damage and a concomitant increase in the luminescent intensity. The vibrational data reported here for AlP04-l1 corresponds to that recorded from the as-synthesized dipropylamine containing material. The 90M240-em’ Region. Each of the molecular sieves examined displayed a feature just above 1200 cm-I, also present in the spectrum of a-AlP04.’z-34 For AIP04-11 and AlPO4-5, this band is at 1240 and 1236 cm-’, respectively, compared to a valueof 1235 cn-l for u-A1P04. Upon increasing themaximum ring size further this hand is observed to shift to 1227 cm-I for A1P04-8(14T-atomring) and to 1217cm-l for VPI-5 (18 T-atom ring). The strongest feature in this region of the spectrum appearedat l140,1125,1115(shoulderat 1137cm-’),and1113 cm-l for AIP04-5, AIP04-11, AlPO4-8, and VPI-5, respectively. The AIP04-11 hand undoubtedly appears to be shifted to a lower wavenumber value due to the presence of a strong organic peak in this region. For the other AIP04 materials, lower frequencies areobservcdastheaverageAl-O-Pangleisdecreased (seeTahle 3). A heuristic explanation for this shift is readily available. In analogy to aluminosilicates, modes in the 1100- and 600-cm-l regions involve bending and stretching of bridging oxygens. As the AIM-P angle narrows, the bending character increases for the 1100-cm-l region causing a decrease in frequency while similarly increasingthe stretchingCharacterin the 60km-1 region for an increase in frequency. The precise functional dependence of the frequency on the A I L G P angle is expccted to depend upon the dynamical nature of the mode in question. Deckman el al. have recently shown that thesquareof the frequencyofthe intense AI mode in the stretching region of various sodalites decreases
Holmes et al.
4680 The Journal of Physical Chemistry, Vol. 98, No. 17. 1994
n
1127.53 lOm
800
600
400
200
0
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0.00
400
i!
I
200
0
50
3078.88
800
1200
c
50
w
4w
w
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imoo
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Wavenumber
Figure 5. Raman spectra of (a) PrzNH-AlPO4-11, (b) calcined AIPO45, (c) AIP04-8, and (d) VPI-5.
Wavenumber Figure 4. Raman spectra of (a) Pr3N (liquid), (b) Pr3N-AIPO4-5, and (c) calcined AlPO4-5. linearly as the cosine of the T-O-T angle increases.”ll (This assumes invariant force constants.) A similar correlation appears to hold for the molecular sieves studied here, although it must be noted that the average T-O-T angle varies over a very small range, 157So-148.4O, compared to almost 30° for the series of chlorosodalites examined by Creighton et al. The spectra of AlP04-5, AlPO4-8, and VPI-5 also clearly show additional bands in this region as lower frequency shoulders to the main peak. Zeolite framework bands in this region have previously been assigned to discrete S i 4 and A 1 4 stretches in the Raman spectra of faujasites and in the IR spectrum of NaY.39 However, recent work by Creighton et al. on sodalite indicates that the intense bands in this region are coupled symmetricstetching modes of individual SiO, and A104 tetrahedra in which adjacent tetrahedra vibrate in antiphase.lO In light of this, assignment of the AlP04 stretching modes to individual components is of questionable validity.
TABLE 2 Observed Raman Lines of Unidimensional Aluminophospbate Molecular Sieves** AlP04-11 AIPO4-5 AIP04-8 VPI-5 1240w 1236w 1227 w 1217 w 1140s 1141 s 1137 s 1167s 1113 msh 1121 ssh 1125 msh 1115 s 1066 msh 1081 wsh 1048 msh 1050 wsh 640 w 567 w 566 wsh 610 w 605 w 494 s 499 s 483 s 492 s 461 msh 462 m 485 msh 410 m 438 msh 433 s 404 msh 398 s 378 msh 361 msh 377 m 375 s 262 s 267 wsh 300 msh 305 s 247 s 281 s 255 w 213 w 221 wsh 227 w 217 w 178 w 201 m 207 w 204 w 143 w 177 w 184 w 126 w
122 w
119 w
115 w
105 w 60 w 60 w a Intensity notation: s = strong,m = medium, w = weak,sh = shoulder. b Well-resolved template modes not listed. 85 w
61 w
The 350450-cm-1Region. AlP04-5, AlP04-11, and VPI-5 all display single bands above 500 cm-1, a t 566 cm-1 for AlP04-5 (present as a weak shoulder on the 500-cm-1 resonance), at 567 cm-1 for AlPO4-11,and at 605cm-1 for VPI-5. AlP04-8 displays a weak doublet at 610 and 640 cm-l. In comparison, &Alp04 has a band a t 568 cm-1.32933 Although this band appears to be shifted to higher frequency for the sieves with larger channel systems, a simple correlation with the AI-0-P angle is not
Raman Spectra Unidimensional AlP04 Sieves
*
The Journal of Physical Chemistry, Vol. 98, No. 17, 1994 4681
TABLE 3: Average AI-0-P Angles for Each of the Studied Molecular Sieves**9
-Os’
av ~ 4 1 4 - P(deg) molecular sieve AIPO4- 1 1 AlP04-5 AlPO4-8 VPI-5
framework
channel
157.5 157.0 148.4 154.0
148.2 147.3 143.8 139.5
apparent. For each of the AlPO, sieves, a complex band system was observed between 500 and 300 cm-1. The results of a calculation of the number of anticipated vibrational modes for each of the materials in question, calculated utilizing the correlation method of Fateley et ~ l .and , ~independently verified by the method of Winston and Halford,41 is presented in Table 4. Without reference to intensities,increasingnumbers of Raman active modes are expected in the series AlP04-5, VPI-5, AlP0411, and AlP04-8. In general, this is reflected in the relative complexities of the 350-500-~m-~lattice deformation region. Given the large number of possible Raman active modes, it is improbable that many (if any) peaks in the spectra result from a single mode. Only one peak between 350 and 500 cm-I is clearly visible in the AlP04-11 system, with no structure discernable for AlP04-8. The spectrumof VPI-5 in this region, however, appears less congested than that of AlP04-5. This may arise from band shifts resulting in an increased number of accidental degeneracies in the spectrum of VPI-5, relative to AlP04-5. a-AlP04displays an intense AI mode at 456 cm-l, with weaker E features at 417 and 371 cm-1.32 The complex bands observed for the AlP04 sieves in this region occur at 500-398 cm-I (AlP04-5), 494-377 cm-l (AlP04-1l), 494-374 cm-l (AlP04-8), and 492-374 cm-I (VPI-5). We proposed above that, for AlP04-5, the additional features arise from deformations involving the four T-atommembered rings. Creighton et al. have shown that for totally symmetric T-0-T motions, where the T-atom is constrained not to move by its site symmetry, the frequency of this feature varies linearly with the cosine of the T-0-T angle.10.11 For the AlP04 molecular sieves examined here, the T-atom site symmetries are all C2 or 10wer2”~~ and hence these atoms may move as part of a symmetric bending motion. The 100-350-cm-1 Region. Zeolite Raman bands occuring in this region have largely been assigned to external vibrations, such as cation translatory motions, and ring breathing or distortion mode~.1~~-~1,42~43 There are no charge balancing cations present in the studied AlP04 structures considered here, and thus, the external modes might be expected to principally involve ring breathing and distortion modes. The primary rings for these materials contain four and six T-atoms, which are linked together to generate larger unidimensional channels of 10, 12, 14, and 18 T-atoms for AlP0,-11, AlP04-5, AlP04-8, and VPI-5, respectivelyZ”29 (Figure 1). Thus, thevibrational spectra of these materials might be expected to contain common features associated with the external modes of the smaller rings and distinct modes arising from the larger, channel-describingrings. A strong TABLE 4 material a-quartz
-0.9 I
-60000
70000
I
I
80000
90000
100000
Y2 Figure 6. Plot of cos 0 versus v2, where 0 is the average A1-O-P angle around the unidimensionalchannel of each of the AIPO,-ll(lO T-atom), AIP04-5 (12 T-atom), AIPO4-8 (14 T-atom), and VPI-5 (18 T-atom) unidimensional molecular sieves and Y (in cm-I) is the peak center for the pore breathing mode.
band is observed in the 3 10-260-cm-1 region for all of the studied AlPO, molecular sieves; this band is not present in the Raman spectrum of ~ u - A l P 0 4 .The ~ ~ frequency of this mode is observed to increase with increasing ring size in the order AlP04-11 (262 cm-I), A1P04-5 (267 cm-I), AlP04-8 (281 cm-I), and VPI-5 (305 cm-l). a-AlP04displays strong bands at 216 (broad), 116 and 105cm-1. EachoftheAlP04molecularsievesalsodisplayfeatures in these regions: AlPO4-11 (213,178,126 cm-l); AlP04-5 (201, 122 cm-I); AlPOd-8 (227,207, 177, 119 cm-1); VPI-5 (217,204, 184, 115 cm-1). The strongest candidate for an external mode associated with the large rings is therefore the 262-305-cm-l vibrational band, from AlP04-11 through to VPI-5. The average AI-0-P angle around the unidimensional channel systems of the studied materials was calculated uia CHEM-X; seeTable 3. These data are plotted as cos 0 versus vz in Figure 6. Note that the frequency of this feature displays a monotonic dependence upon the average A1-O-P angle within the largest ring size of each of the AlP04 structural polytypes. Like the sodalite materials studied by Creighton et al.,lOJ1a linear dependence of the square of this mode on the cosine of the average A1-O-P angle around the channels is clear, as is illustrated in Figure 6. The correlation factor (rz) for this dependency was determined to be 0.9979 (intercept = -1.102, slope = 3.696 = 1W). Conclusions The Raman spectra for a closely related series of AlP04 molecular sieves, with known framework topologies, have been ratonalized utilizing currently accepted approachesfor the analysis of aluminosilicate zeolites. The need for direct probes of zeolite
Factor Group Analyses for Quartz, Berlinite, AlPO4-11, AlPO& AIP04-8, and VPI-5 unit -... cell . formula (Bravais cell formula) Si306
mace Prom (fktorlgroip) P3121(152)
rtot
AI + 5.42 + 9E
ramurt A2+E
rhrma AI+ 8E
rIR
4Az
+ 8E
4682 The Journal of Physical Chemistry, Vol. 98, No. 17, I994 structures applies equally to A1PO4 sieves. The aluminophosphates display a diverse range of known topologies; investigation of these offers great potential for the development of Raman spectroscopyas an aid to solving unknown structures (for instance, by correlation of framework bands in the region of ca. 310-260 cm-1). Furthermore, two-dimensional layer structures, particularly prevalent in aluminophosphate synthesis systems, should be differentiable from three-dimensional sieves by the absence of vibrational“channelbreathing” modes in this wavenumber region. This initial work has demonstrated the usefulness of Raman spectroscopy as a tool for probing the frameworks, occluded templates, and template removal of aluminophosphate molecular sieves. Given the increasing interest in advanced applications of large single crystals and thin films of these kinds of materials grown on opaque substrates,44the importanceof Raman scattering as a diagnostic probe is expected to intensify. The addition of Alp04 spectra to the existing body of experimental data for aluminosilicates should also help to extend the scope of current efforts aimed at calculating the vibrational spectra of molecular sieves.
Acknowledgment. The authors thank Colin Flood of the Department of Physics at University of Toronto for assistance with exploratory Raman scattering measurements, Dr. Neil Coombs (Imagetek) for the SEM-EDX data, Dr. Srebri Petrov (Ontario Geological Survey) for the pXRD patterns, Dr. Alex Kuperman for constructive discussion regarding this work, and the Natural Science and Engineering Research Council of Canada (N.S.E.R.C.) for generous financial support, especially the funding of the Raman and laser instrumentation employed in thistypeofresearch. S.J.K. a1sothanksN.S.E.R.C. fora graduate scholarship. References and Notes (1) Angell, C. L. J. Phys. Chem. 1973, 77, 222. (2) Dutta, P. K.; Del Barco, B. J. Chem. Soc., Chem. Commun. 1985, 1297. (3) Dutta, P. K.; Del Barco, B. J. Phys. Chem. 1985,89, 1861. (4) Dutta, P. K.; Shieh, D. C.; h r i , M. Zeolites 1988,8, 306. (5) Dutta, P. K.; Del Barco, B. J. Phys. Chem. 1988, 92, 354. (6) Pilz, W. Z. Phys. Chem. 1990, 271, 219. (7) Dutta, P. K.;Twu, J. J . Phys. Chem. 1991, 95, 2498. (8) Dutta, P. K.; Rao, K. M.; Park, Y .P. J . Phys. Chem. 1991,95,6554. (9) Buckley, R. G.; Deckman, H. W.; Newsam, J. M.; MacHenry, J. A.; Persans, P. D.; Witzke, H. M.R.S. Symp. Ser. 1988, No. 111, 141. (10) Creighton, J. A.; Deckman, H. W.; Newsam, J. M. J. Phys. Chem. 1991, 95, 2099.
I-
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(11,
(1 1) Deckman, H. W.; Creighton, J. A.; Buckley, R. G.; Newsam, J. M. M.R.S. Symp. Ser. 1991, No. 233, 295. (12) Dutta, P. K.; Zaykoski, R. Zeolites 1988.8, 179. (13) Place, R. D.; Dutta, P. K. Anal. Chem. 1991, 63, 348. (14) Salzer, R.; Steinberg, K.-H.; Klaeboe, P.;Schrader, B. Zeolites 1991, 11, 694. (15) Hardin, A. H.; Klemes, M.; Morrow, B. A. J. Catal. 1980,62,316. (16) Buckley, R. G.; Deckman, H. W.; Witzke, H.; McHenry, J. A. J . Phys. Chem. 1990, 94, 8384. (17) Twu, J.; Dutta, P. K.; Kresge, C. T. Zeolires 1991, 11, 672. (18) Vergilov, I.; Valtchev, V. Zeolites 1991, 11, 387. (19) Dutta, P. K.; Shieh, D. C. J . Phys. Chem. 1986, 90, 2331. (20) Dutta, P. K.; Del Barco, B. J . Phys. Chem. 1988, 92, 354. (21) Dutta, P. K.; Shieh, D. C.; Puri, M. J . Phys. Chem. 1987,91,2332. (22) Baranska, H.; Czerwinska, B., Labudzinska, A. J . Mol. Struct. 1986, 143, 485. (23) Dutta, P. K.; Puri, M. J. Phys. Chem. 1987, 91, 4329. (24) Davis, R. J. Chemistry of Materials 1992, 4, 1410. (25) Bedard, R. L.; Bowes, C. L.; Coombs, N.; Holmes, A. J.; Jiang, T.; Kirkby, S. J.; Macdonald, P. M.; Malek, A. M.; Ozin, G. A.; Petrov, S.; Plavac, N.; Ramik, R. A.; Stele, M. S.;Young, D. J . Am. Chem. Soc. 1993, 1IS, 2300. (26) Bennett, J. M.; Cohen, J. P.; Flanigen, E. M.; Pluth, J. J.; Smith, J. V. ACS Symp. Ser. 1983, No. 218, 109. (27) Richardson Jr., J. W.; Pluth, J. J.; Smith, J. V. Acta Crystallogr. 1988, B44, 367. (28) Rudolf, P. R.; Crowder, C. E. Zeolites 1990, 10, 163. (29) Dessau, R. M.; Schlenker, J. L.; Higgins, J. B. Zeolites 1990, IO,522. (30) Wilson, S.T.; Lok, B. M.; Flanigen, E. M. U S . Patent 4,310,440 (1982). (31) Davis, M. E.; Young, D. Stud. Surf. Sci. Catal. 1991, 60, 53. (32) Scott. J. F. Phvs. Rev. B 1971. 4. 1360. (33) Lazarev, A. N.;Mazhenov, N. A.;Mirgorodskii, A. P. 0pt.Spektrosk. 1979, 46, 619. (34) Jayaraman, A.; Wood, D. L.; Maines Sr., R. G. Phys. Rev. B 1987, 35, 8316. (35) deMan,A. J. M.SimulationofPhysicalPropertiesofZeoliticLattices; Ph.D. Thesis, Eindhoven University of Technology, 1992. (36) de Man, A. J. M.; Jacobs, W. P. H.; Gils;, J. P.; van Santen, R. A. Zeolites 1992, 12, 826. (37) Davis, M. E.; Montes, C.; Hathaway, P. E.; Arhancet, J. P.; Hasha, D. L.; Garces, J. M. J. Am. Chem. SOC.1989, 111, 3919. (38) Richardson Jr., J. W.; Pluth, J. J.; Smith, J. V. Acta Crystallogr. 1987, C43, 1469. (39) Liu, X . ; Zhizong, Z.; Xu,Y.; Xu,R. J. Chem. Soc., Chem. Commun. 1990. 13. (4)Fateley, W. G.; Dollish, F. R.; McDevitt, N. T.;Bentley, F. F. Infrared and Raman Selection Rules for Molecular and Lattice Vibrations; Wiley: Toronto, 1972. (41) Winston, H.; Halford, R. S. J. Chem. Phys. 1949, 17, 607. (42) Flanigen, E. M. In Zeolire Chemistry and Catalysis; Rabo, J. A., Ed.; ACS Monogr. Ser. No. 171; American Chemical Society: Washington, DC, 1976; p 80. (43) Godber, J. P. IntrazeoliteChemistryandSpectroscopy;Ph.D. Thesis, University of Toronto, 1987. (44) Ozin, G. A. Ado. Mater. 1992, 4, 612.
