Structure analysis of the novel microporous aluminophosphate IST1 using synchrotron powder...

$: Structure analysis of the novel microporous aluminophosphate IST1 using synchrotron powder diffraction data and HETCOR MAS NMR$
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Microporous and Mesoporous Materials 65 (2003) 43–57

Structure analysis of the novel microporous aluminophosphateIST-1 using synchrotron powder diffraction data

and HETCOR MAS NMR

Jos�ee Luis Jord�aa a, Lynne B. McCusker a,*, Christian Baerlocher a,Cl�aaudia M. Morais b,c, Jo~aao Rocha b, Christian Fernandez c,

Cristina Borges d, Jo~aao P. Lourenc�o e, Maria F. Ribeiro d, Zelimir Gabelica f

a Laboratorium f€uur Kristallographie, ETH, CH-8092 Z€uurich, Switzerlandb Department of Chemistry, CICECO, University of Aveiro, P-3810-193 Aveiro, Portugal

c Laboratoire de Catalyse et Spectrochimie, CNRS UMR 6506, ENSICAEN, F-14050 Caen, Franced Instituto Superior T�eecnico, Dep. Engenharia Qu�ıımica, P-1049-001 Lisboa, Portugale Universidade do Algarve, Faculdade de Cieencias e Tecnologia, P-8000 Faro, Portugal

f Groupe Securit�ee et Ecologie Chimiques, ENSCMu, Universit�ee de Haute Alsace, F-68093 Mulhouse Cedex, France

Received 3 June 2003; received in revised form 21 July 2003; accepted 25 July 2003

Abstract

A combination of advanced powder diffraction and NMR techniques have allowed the structure of the novel mi-

croporous aluminophosphate IST-1 (|(CH3NH2)4(CH3NHþ3 )4(OH�)4|½½½Al12P12O48��) to be elucidated. The framework

structure was determined in the non-centrosymmetric space group Pca21 (a ¼ 9:61523ð1Þ �AA, b ¼ 8:67024ð1Þ �AA,

c ¼ 16:21957ð2Þ �AA) from high-resolution synchrotron powder diffraction data using the program FOCUS. Extra

framework species were then located on difference electron density maps. A hydroxyl group was found to bridge be-

tween two of the framework Al atoms, and one methylamine species, presumably protonated, could be located in the

channels where it H-bonds to three framework oxygens. The most unusual feature of the structure is the second

methylamine molecule, which bonds directly to a framework Al atom. The structure is entirely consistent with 31P and27Al MAS NMR studies, which showed there to be three P (all 4-coordinate) and three Al (one 4-, one 5- and one 6-

coordinate) sites, and with 13C MAS NMR, which showed there to be two different types of methylamine species in

equal amounts. Assignment of the 31P, 27Al and 13C MAS NMR signals could be deduced from the crystallographic

data,31P-27Al HETCOR spectra and ab initio calculations.

� 2003 Elsevier Inc. All rights reserved.

Keywords: Aluminophosphate; FOCUS; IST-1; MAS NMR; Powder diffraction

* Corresponding author.

E-mail address: [email protected] (L.B. McCus-

ker).

1387-1811/$ - see front matter � 2003 Elsevier Inc. All rights reserve

doi:10.1016/S1387-1811(03)00499-2

1. Introduction

Since the early work of Flanigen and co-work-ers [1] on AlPO4-n molecular sieves, extensive re-

search has resulted in the discovery of many novel

d.

mail to: [email protected]

44 J.L. Jord�aa et al. / Microporous and Mesoporous Materials 65 (2003) 43–57

topologies with a diversity of structures and

compositions. Recently, we reported the synthesis

of two new aluminophosphates (IST-1 and IST-2)

prepared in aqueous media using methylamine

(MA) as the main template, either added directly

or generated in situ from methylformamide [2,3].The structure of IST-2 subsequently proved to

have the AEN framework type and a structure

very similar to that of AlPO-53(A) reported by

Kirchner et al. in 2000 [4], but that of IST-1 ap-

peared to be novel.

Short chain amines and in particular methyl-

amine, are rarely used as the sole template in mi-

croporous aluminosilicate or aluminophosphatesyntheses [5], because such small entities, in the

absence of any other structuring agent, tend to

lead to narrow pore structures. In the case of

AlPO-EN3 [6] and its isotypes CFSAPO-1(A) [7],

JDF-2 [8], AlPO4-53(A) [4] and IST-2 [2,3], the

exact role of methylamine, which is added to the

synthesis mixture directly, is unclear. Perhaps it

plays an indirect role by generating hydroxylgroups that can bridge between neighboring Al

atoms and thereby stabilize the topology. Since

IST-1, like these AEN-type materials, does not

collapse upon calcination, but undergoes a struc-

tural transformation above 350 �C to form a dif-

ferent thermally stable microporous material, it

might be expected to have some structural features

in common with IST-2.In order to elucidate the structure of IST-1 and

thereby clarify the role of methylamine in the

synthesis, both high-resolution synchrotron pow-

der diffraction and comprehensive 27Al, and 31P

magic-angle spinning (MAS) NMR experiments

have been performed. Because 27Al is a I ¼ 5=2quadrupolar nucleus, the spectral lines are

broadened by the second-order quadrupolar in-teraction and the �conventional� MAS spectra are,

in general, poorly resolved, so the multiple-quan-

tum (MQ) MAS NMR technique [9] was also

applied.

Recently, it has been shown that the resolution

of the 31P NMR spectra of aluminophosphates can

sometimes be improved by using 27Al decoupling,

thus removing the 27Al–31P scalar coupling [10].HETCOR MAS NMR experiments between

quadrupolar (I) and spin-1/2 (S) nuclei have been

used previously [11,12]. Here we show this to be a

potentially very useful technique for studying the

Al–P connectivity in microporous aluminophos-

phates.

2. Experimental

2.1. Synthesis

A typical synthesis of IST-1 involved heating a

hydrogel having the molar composition 1Al2O3:

1P2O5:1methylamine:1TEAOH:35H2O. The alu-

minum source, pseudoboehmite (PURAL SB,Condea), was added to diluted ortho-phosphoric

acid (Merck, 85% aq. soln.), and the resulting so-

lution was stirred until a homogeneous gel was

obtained. First methylamine (Fluka, 41% aq.

soln.) and then the tetraalkylammonium salt

(TEAOH, Alfa, 35% aq. soln.) was added to the

gel. The mixture was then stirred for 2 h prior to

heating in a Teflon-lined autoclave under staticconditions at 170 �C at autogeneous pressure. The

crystallization time was typically 1 day. The re-

sulting crystalline products were recovered by

centrifugation, washed with distilled water and

dried at 80 �C overnight. The detailed synthesis

operations and variants are described and dis-

cussed elsewhere [3].

The as-synthesized material proved to be pureand highly crystalline, as checked by powder XRD

(Rigaku diffractometer using Ni-filtered CuKaradiation) and SEM (Hitachi F-2400 microscope).

The unit cell composition, derived from bulk ele-

mental analysis for Al and P (ICP, Perkin Elmer

Emission Spectrometer Plasma 400) and N and C

(E.A. 1180 CHNS-O Fisons Instruments) and

from water and methylamine contents determinedindependently by combined TG-DSC (Setaram

TGA 92 microbalance), was |(CH3NH2)7:6-

(H2O)4:4|½½½Al12P12O48��.X-ray powder diffraction and 27Al and 31P MAS

NMR data indicate that IST-1 undergoes an irre-

versible structural reorganization upon removal of

the template at 300 �C to yield a microporous

crystalline phase that is thermally stable up to ca.550 �C. Around 600 �C this phase transforms into

a tridymite-type AlPO4.

J.L. Jord�aa et al. / Microporous and Mesoporous Materials 65 (2003) 43–57 45

2.2. X-ray data collection

High-resolution X-ray powder diffraction data

were collected on the Swiss–Norwegian Beamline

(SNBL) at the European Synchrotron RadiationFacility (ESRF) in Grenoble, France. Data col-

lection parameters are given in Table 1.

The diffraction pattern was indexed on an or-

thorhombic unit cell (a ¼ 9:615 �AA, b ¼ 8:669 �AAand c ¼ 16:220 �AA) using the program N-TREOR

[13]. A careful examination of the diffraction pat-

tern indicated that the reflections 0kl, l ¼ 2nþ 1

and h0l, h ¼ 2nþ 1 were systematically absent, sothe two most probable space groups could be ex-

pected to be Pcam (standard setting Pbcm) or

Pca21.

2.3. NMR experiments

All NMR spectra were recorded on a Bruker

Avance 400 (9.4 T, wide-bore) spectrometer at100.4, 104.2 and 161.9 MHz for 13C, 27Al and 31P,

respectively. The 13C MAS NMR spectrum was

recorded with 40� pulses, a spinning rate of 10 kHz

and 120 s recycle delays. Chemical shifts are quo-

ted in ppm from TMS. The 31P MAS NMR

spectrum was recorded with 40� pulses, a spinning

rate of 10 kHz and 60 s recycle delays. Neither 27Al

nor 1H decoupling improved the resolution of the31P MAS NMR spectrum. Chemical shifts are

quoted in ppm from 85% H3PO4. The single-

quantum 27Al MAS NMR spectrum was measured

using short and powerful radio-frequency pulses

(0.6 ls, equivalent to a 9� pulse angle), spinning

Table 1

X-ray data collection

Synchrotron facility SNBL at ESRF

Wavelength 0.79977 �AA

Diffraction geometry Debye–Scherrer

Analyzer crystal Si 1 1 1

Sample Rotating 1.0 mm capillary

2h range 3–48�Step size 0.004�2hTime per step

3.0–9.9�2h 1.0 s

9.9–17.5�2h 1.7 s

17.5–48.0�2h 9.0 s

rates of 14 kHz and a recycle delay of 1 s.

Chemical shifts are quoted in ppm from

Al(H2O)3þ6 .

The triple-quantum 27Al MAS NMR spectrum

was recorded using the Z-filter three-pulse se-

quence [14]. The lengths of the first and secondhard pulses (radio-frequency magnetic field am-

plitude t1 ¼ 150 kHz) were 3.4 and 1.1 ls, re-

spectively. The length of the third soft pulse (t1 ¼10 kHz) was 11 ls. The MAS rate was tR ¼ 15

kHz. 142 points were acquired in the t1 domain in

increments of ð1=mRÞ ¼ 67 ls. The ppm scale of the

sheared spectrum was referenced to m0 frequency inthe m2 domain and to 1.42 m0 (high-resolutionspectra after shearing) in the m1 domain (reference

Al(H2O)3þ6 ). Numerical simulations of the single

and triple-quantum spectra were carried out with

the inhouse program MASAI (Fernandez).

The 27Al–31P heteronuclear correlation (HET-

COR) spectra were obtained underMAS conditions

using CP for mixing. Efficient cross-polarization

was achieved under a constant radio-frequency fieldof 30 kHz for 31P and by ramping the field between

5 and 10 kHz for 27Al. The experiment was per-

formed using three different values for the offset

frequency on the 27Al nucleus. For each offset value

three contact times values were used. The recycle

delay was 1 s and the MAS rate tR ¼ 10 kHz. 100

points were acquired in the t1 domain in increments

of ð1=mRÞ ¼ 100 ls.Ab initio calculations of 13C NMR chemical

shifts were performed using the Gaussian 98w

package. Molecular structures were optimized at

the HF/6-311G(d,p) standard level, and the mag-

netic properties (from which NMR shifts for C

atoms were obtained) were calculated at the same

level using the GIAO formulation [15] as imple-

mented in G98w.

3. NMR results

3.1. 13C MAS NMR

The 13C MAS NMR spectrum of IST-1, shown

in Fig. 1a, displays two resonances centered at 24.3and 28.0 ppm with a 1:1 intensity ratio.

10152025303540ppm from TMS

-60 -70-40-2060 40 20 0

ppm from Al(H2O)63+

-35-30-25-20-15-10-5 -40

ppm from 85% H3PO4

(a)

(b)

(c)

Fig. 1. (a) 13C, (b) 31P and (c) 27Al MAS NMR spectra of as-

prepared IST-1.

ppm

-5050 0 ppm

- 20

60

40

20

0 S1

S2

S3

-

-

ppm from Al(H2O)63+

Fig. 2. 3Q 27Al MAS NMR spectrum of as-prepared IST-1.


3.2. 31P MAS NMR

The 31P MAS NMR spectrum of IST-1, shown

in Fig. 1b, displays three 31P MAS NMR reso-

nances centered at )16.4, )18.2 and )27.9 ppm in

1:1:1 intensity ratios. 27Al (and 1H) decoupling did

not improve the spectral resolution.

3.3. 27Al MAS NMR

The 27Al MAS NMR spectrum of IST-1, shown

in Fig. 1c, displays three resonances centered at

45.7, ca. 10 and )7.9 ppm in 1:1:1 intensity ratios.

3Q MAS NMR confirms that only three lines are

present (Fig. 2). Simulations of the single- andtriple-quantum spectra (not shown) show that the

isotropic chemical shift of the second-order quad-

rupole powder pattern, S2, centered at 10 ppm isdiso ¼ 21:0 ppm and this resonance was therefore

assigned to five-coordinate Al. The quadrupole

coupling constant and asymmetry parameter are,

respectively, CQ ¼ 4:6 MHz, g ¼ 0:21. The peaks

S3 at 45.7 (diso ¼ 47:3 ppm, CQ ¼ 1:8, g ¼ 0:20)and S1 at )7.9 ppm (diso ¼ �6:3 ppm, CQ ¼ 2:0MHz, g ¼ 0:21) are attributed to four- and six-

coordinate Al, respectively.

3.4. 27Al–31P HETCOR MAS NMR

The HETCOR spectrum of IST-1, shown in

Fig. 3, exhibits connectivities between all Al and

all P sites. In order to get a deeper insight into the

Al–P connectivity in this material, a series of

HETCOR spectra at different 27Al–31P cross-polarization contact times and at different 27Al

offsets were recorded. These spectra are identical

with respect to 27Al–31P connectivities. Here only

one of these spectra is shown.

4. Structure determination

Although the NMR data indicated the presence

of 5- and 6-coordinate Al, it was hoped that the

framework could still be regarded as a 4-connected

-10 -15 -20 -25 -30

-10

50

40

30

20

10

0S1

S2

S3

I1 I3I2

ppm from 85% H3PO4

ppm from

Al(H

2 O)6 3+

ppm from 85% H3PO4

-10 -15 -20 -25 -30

Fig. 3. 27Al–31P HETCOR spectrum of as-prepared IST-1 recorded with a contact time of 2 ms. The slices given on the right cor-

respond to the 31P sites connected to each 27Al-site.


net and that these Al species had simply incor-

porated additional ligands into their coordina-

tion spheres. This would mean that the program

FOCUS, which was written specifically for deter-mining zeolite (three-dimensional 4-connected)

framework structures from powder diffraction

data [16,17], could be applied without difficulty.

Briefly, the program involves (1) generating an

electron density map from the intensities extracted

from the powder diffraction pattern (random

phases assigned initially), (2) interpreting that map

either using a specialized framework search pro-cedure or assigning atoms by peak height and al-

lowed interatomic distances, and (3) calculating

new phases based on the model obtained in step 2.

If the phases calculated in step 3 are different from

those used to generate the last electron density

map, a new map is calculated using the observed

intensities and these new phases, and the proce-

dure is repeated (Fourier recycling) until the pha-ses have converged. The whole process is then

repeated with a new set of random phases, etc.

Each time an electron density map is generated, an

exhaustive search for a three-dimensional, 4-con-

nected framework structure is performed. If one is

found, it is classified and written to a file. The

program is stopped when one of the frameworks in

this file dominates. That structure, which has been

foundmost often and from different starting points,

is most likely to be the correct one. A somewhat

more detailed description of the FOCUS algo-

rithm written for non-crystallographers, can befound in Ref. [18].

Individual reflection intensities were extracted

from the diffraction pattern of IST-1 out to a

minimum d-spacing of 1.4 �AA (ca. 33�2h) using the

program EXTRACT [19], and the intensities of

severely overlapping reflections were simply equi-

partitioned (27% of the 276 reflections were within

0.15*FWHM of a neighboring reflection). Becausethe scattering factors for Al and P are very similar,

no attempt was made to distinguish between them

at this stage. Both were just assumed to be Si.

However, only rings with an even number of

T-atoms were allowed. The centrosymmetric space

group Pbcm was tried first, but the best solution

from FOCUS was not compatible with alternating

Al and P positions. Rather than trying to reducethe symmetry of this model by hand, we decided to

see if FOCUS would generate the correct solution

directly in the non-centrosymmetric space group

Pca21. It was also reasoned that the solution in the

lower space group might be different from the one

found in Pbcm.

Within an hour, the program had generated

10 unique framework structures, and, as can be

139

2415

7 6 4 2 1 1 10

20

40

60

80

100

120

140

160

1 2 3 4 5 6 7 8 9 10unique topologies

Fig. 4. The 10 framework topologies generated by FOCUS in the space group Pca21 and their frequency of occurrence.

Table 2

FOCUS input parameters

Framework atoms

Si 24


seen in the histogram shown in Fig. 4, one of thesewas clearly favored over the others. The input

parameters for this FOCUS run are given in

Table 2.
O 48
Minimum distances

Si–Si 2.6 �AA

Si–O 1.4 �AAO–O 2.3 �AA

Rings

Minimum ring size 4

Maximum ring size 24

Even loops only

Electron density map interpretation

Maximum number in recycling loop 10

Alternate between largest fragment and

peak height procedures

Reflection data

Fobs

Minimum d-spacing 1.40 �AAscale 0.09

Overlap

Factor (FWHM) 0.15

Treatment Equal mF 2

Reflections

Number input 276

Number used (75% of total intensity) 145

5. Structure completion and Rietveld refinement

The model obtained from the FOCUS runconsisted of six Si atoms. First the Si atoms were

converted to alternating Al and P sites (three of

each), and then the positions of the 12 bridging O-

atoms were calculated using the program KRI-

BER [20]. Finally, the coordinates of all atoms

were optimized using the program DLS-76 [21].

This framework model appeared to be consistent

with the 31P and 27Al NMR data (i.e. each withthree sites of equal occupancy) and to give a rea-

sonable fit to the diffraction pattern, so it was used

as a starting point for structure completion and

Rietveld refinement using the program package

XRS-82 [22]. It was not clear at this point which

set of positions were P-atoms and which Al-atoms.

One of the two possible models was simply as-

sumed.Difference Fourier maps revealed the locations

of two methylamine species. One of these (N(1)–
C(1)) was coordinated (presumably via the N-
atom) to a T-atom, so this T-site could be assigned


as Al (Al(1)) and the Al/P ambiguity mentioned

above could be resolved. The other methylamine

species (N(2)–C(2)) was found in the channels,

within hydrogen-bonding distance of three frame-

work oxygens (O(1), O(2) and O(12)). An addi-

tional atom (O(13)) bridging between twoAl-atoms(Al(1) and Al(3)) was also found. This was assumed

to be a hydroxyl group. To maintain charge bal-

ance, the methylamine species within the channels

(N(2)–C(2)) was assumed to be protonated.

This model, with one 6-coordinate, one 5-

coordinate and one 4-coordinate Al-atom (Al(1),

Al(3) and Al(2), respectively) and with three tet-

rahedrally coordinated P-atoms, is in completeagreement with the 27Al and 31P NMR data.

Furthermore, the presence of two types of meth-

ylamine species is consistent with the observation

of two peaks of equal intensity in the 13C NMR

spectrum. The chemical composition of this model

Fig. 5. The coordinations spheres of the framework cations in

as-synthesized IST-1. Note that Al(1) is 6-coordinate, Al(2) 4-

coordinate and Al(3) 5-coordinate, and that all P-atoms are

4-coordinate.

is also consistent with the chemical analysis. The

coordination spheres of the six framework cations

are shown in Fig. 5, and the locations of the

methylamine species in Fig. 6. A simplified draw-

ing of the full framework structure with frame-

work oxygens and methylamine species omitted isgiven in Fig. 7.

Refinement of this structural model converged

with the error indices RF ¼ 0:042 and Rwp ¼ 0:125(Rexp ¼ 0:043). Geometric restraints were used on

the bond distances and angles of the framework

Fig. 6. The location of the extraframework species in as-syn-

thesized IST-1 (a) viewed down the c-axis and (b) viewed down

the b-axis. A hydroxyl group O(13) bridges between Al(1) and

Al(3). One methylamine molecule (N(1)–C(1)) is coordinated

directly to Al(1), while the other is in the channels at hydrogen-

bonding distances from three framework oxygens. This mole-

cule is probably protonated.

Fig. 7. Simplified drawings of the framework structure of IST-1, in which the bridging oxygens have been omitted for clarity, showing

(a) a building unit consisting of four fused 4-rings and two 6-rings, (b) a chain of these building units extended along the a-axis, (c)

chains in (b) related by a 21 axis linked to form a sheet perpendicular to the b-axis, and (d) sheets in (c) linked to form the IST-1

framework structure.


atoms and on the C–N distances of the methyl-amine species (see Table 3). During the course of

the refinement, the weight of these restraints was

reduced to one (i.e. each restraint was given a

weight equivalent to that of a single point on the

diffraction profile). The H-atoms of the methyl-

amine species and of the hydroxyl group weresimulated by increasing the occupancy parameters

of the associated atoms (e.g. the occupancy pa-

rameter for a C of a CH3 group was increased

from 1.0 to 1.5 to approximate the increase from 6

electrons to 9). Neutral scattering factors were

Table 3

Crystallographic data

Chemical composition |(CH3NH2)4(CH3NHþ3 )4(OH�)4|-

½½½Al12P12O48��Unit cell

a 9.61523(1) �AA

b 8.67024(1) �AA

c 16.21957(2) �AASpace group Pca21

Standard peak for peak shape function

(hkl; 2h)002, 5.65�

Peak range (number of FWHM) 20

Number of observations 10 162

Number of contributing reflections 780

Number of geometric restraintsa 82

P–O 1.52(1) �AA 12

Al(1)–O 1.74(3) �AA 4

1.85(5) �AA 1

Al(2)–O 1.74(1) �AA 4

Al(3)–O 1.74(3) �AA 4

1.85(5) �AA 1

C(1)–N(1) 1.469(1) �AA 1

C(2)–N(2) 1.488(1) �AA 1

O–P–O 109.5(1.0)� 18

O–Al(1)–O 90(8)� 8

180(8)� 1

O–Al(2)–O 109.5(1.0)� 6

O–Al(3)–O 90(8)� 6

120(8)� 3

P–O–Al 145(8)� 12

Number of profile parameters 6

Number of structural parameters 71

Rexp 0.043

Rwp 0.125

RF 0.042

a The numbers given in parentheses are the esd�s assumed for each of the restraints. Each restraint was given a weight equivalent to

the reciprocal of its esd.


used for all atoms. A final difference Fourier mapshowed no significant peaks.

Crystallographic details are given in Table 3,

final atomic parameters in Table 4 and selected

interatomic distances and angles in Table 5. The fit

of the profile calculated from the final model to the

experimental data is shown in Fig. 8.

6. Discussion

The framework structure can be viewed in terms

of the [4462] building unit shown in Fig. 7a. The

units are joined through common 4-rings to formchains parallel to the a-axis (Fig. 7b). These chainsare connected in turn to neighboring chains ori-

ented in the opposite direction (related by a 21screw axis) to form sheets parallel to the ac plane

(Fig. 7c). Finally, these sheets are connected to

identical sheets to form a three-dimensional, 4-

connected net (Fig. 7d) with a one-dimensional 10-

ring sinusoidal channel system running parallel tothe a-axis.

The Al atoms in the 4-ring common to neigh-

boring [4462] units are bridged via a hydroxyl

group (O(13)), which is indicated with a dashed

Table 4

Positional, thermal and occupancy parameters for as-synthesized IST-1a

Atom x y z Uiso (·100 �AA2) Occupancyb

Al(1) 0.1950(3) 0.8346(3) 0.3921(2) 0.55(2)c 4.0

Al(2) 0.0171(3) 0.6502(3) 0.1040(2) 0.55(2)c 4.0

Al(3) 0.1780(3) 0.4521(3) 0.3614(2) 0.55(2)c 4.0

P(1) 0.0380(3) 0.3284(3) 0.7909 0.55(2)c 4.0

P(2) 0.1877(3) 0.5844(3) 0.5345(2) 0.55(2)c 4.0

P(3) 0.0259(2) 0.1513(3) 0.4455(2) 0.55(2)c 4.0

O(1) 0.3738(5) 0.8960(6) 0.4306(4) 0.75(4)d 4.0

O(2) 0.1470(6) 0.7320(6) 0.4927(3) 0.75(4)d 4.0

O(3) 0.0188(5) 0.7988(5) 0.3478(4) 0.75(4)d 4.0

O(4) 0.1226(5) 0.0127(6) 0.4409(5) 0.75(4)d 4.0

O(5) 0.2011(5) 0.3396(6) 0.8031(3) 0.75(4)d 4.0

O(6) 0.9740(5) 0.4831(5) 0.8070(4) 0.75(4)d 4.0

O(7) 0.0198(6) 0.2780(5) 0.7014(4) 0.75(4)d 4.0

O(8) )0.0371(5) 0.7890(6) 0.0367(4) 0.75(4)d 4.0

O(9) 0.1931(5) 0.6098(6) 0.0977(4) 0.75(4)d 4.0

O(10) 0.9400(6) 0.4761(6) 0.0856(4) 0.75(4)d 4.0

O(11) 0.0676(5) 0.2760(6) 0.3868(4) 0.75(4)d 4.0

O(12) 0.2282(5) 0.4627(6) 0.4698(3) 0.75(4)d 4.0

O(13) 0.2607(4) 0.6465(5) 0.3459(3) 0.75(4)d 4.5e

C(1) 0.1528(6) 0.9036(8) 0.7281(4) 5.0 6.0e

N(1) 0.2603(7) 0.9621(7) 0.7855(4) 5.0 5.16e

C(2) 0.1442(7) 0.1472(8) 0.1047(4) 5.0 6.0e

N(2) 0.1317(6) 0.1829(7) 0.0146(3) 5.0 5.72e

aNumbers in parentheses are the esd�s in the units of the least significant digit given. Values without an esd were not refined.bOccupancy parameters are given in terms of atoms per unit cell.c Thermal parameters with the same superscript were constrained to be equal.d Thermal parameters with the same superscript were constrained to be equal.e Occupancy increased to approximate the electron density of the associated H atoms.


line in Fig. 7. One of these Al atoms (Al(3)) is 5-

coordinate (four framework oxygens and the hy-

droxyl group), while the other (Al(1)) forms anadditional bond to a methylamine molecule to

become 6-coordinate (see Fig. 5). A second methyl-

amine species is located in the channels parallel to

the c-axis within hydrogen bonding distance of

three framework oxygens (see Fig. 6). It is assumed

that the latter is protonated to balance the charge

of the hydroxyl group.

The presence of hydroxyl groups bridging be-tween Al atoms has been observed in a number of

aluminophosphate framework structures (e.g.

AlPO-21 [23], AlPO-31 [24], AlPO-40 [25], AlPO-

EN3 [6] and its isostructural analogs [4]), and

framework Al atoms have also been observed to

coordinate to water molecules in addition to the

framework oxygens (e.g. VPI-5 [26], AlPO-H2 [27]

and AlPO-H3 [28]). However, the coordination of

an organic molecule to a framework Al during

synthesis is less common.

An |Al6P6O24|-SOD material prepared in thepresence of dimethylformamide (DMF) contains

Al coordinated to the carbonyl oxygen of DMF

and to a water molecule in addition to the four

framework oxygens [29], an |Al16P16O64|-APD

material (APO-CJ3) contains Al coordinated to

the oxygens of two ethanolamine species in addi-

tion to the four framework oxygens [30], and a

layered aluminophosphate material prepared inthe presence of oxalic acid contains Al coordinated

to the two oxygens of an oxalate group in addition

to four oxygens bridging to P atoms [31]. There

appear to be no reports in the literature in which

an amine used during synthesis is coordinated to a

framework Al. However, it has been suggested

from NMR data that an amine coordinates to Al

temporarily during the synthesis of AlPO-21 [32].

Table 5

Selected interatomic distances (�AA) and angles (�) for as-synthesized IST-1

Al(1)–O(1) 1.91(1) P(1)–O(5) 1.58(1)

Al(1)–O(2) 1.92(1) P(1)–O(7) 1.53(1)

Al(1)–O(3) 1.87(1) P(1)–O(6) 1.50(1)

Al(1)–O(4) 1.87(1) P(1)–O(3) 1.54(1)

Al(1)–O(13) 1.90(1)

Al(1)–N(1) 2.10(1)

Al(2)–O(8) 1.71(1) P(2)–O(2) 1.50(1)

Al(2)–O(9) 1.73(1) P(2)–O(12) 1.54(1)

Al(2)–O(10) 1.71(1) P(2)–O(10) 1.57(1)

Al(2)–O(7) 1.73(1) P(2)–O(9) 1.55(1)

Al(3)–O(11) 1.90(1) P(3)–O(4) 1.52(1)

Al(3)–O(12) 1.83(1) P(3)–O(11) 1.50(1)

Al(3)–O(6) 1.80(1) P(3)–O(8) 1.57(1)

Al(3)–O(5) 1.79(1) P(3)–O(1) 1.54(1)

Al(3)–O(13) 1.88(1)

C(1)–N(1) 1.48(1) N(2)–O(2) 2.80(1)

C(2)–N(2) 1.50(1) N(2)–O(12) 2.87(1)

N(2)–O(1) 2.84(1)

O–Al(1)–O,N O–P(1)–O

Min 86(1) Min 104(1)

Max 94(1) Max 113(1)

Min (axial) 173(1)

Max (axial) 177(1)

O–Al(2)–O O–P(2)–O

Min 104(1) Min 106(1)

Max 114(1) Max 112(1)

O–Al(3)–O O–P(3)–O

Min (axial-equatorial) 84(1) Min 105(1)

Max (axial-equatorial) 98(1) Max 112(1)

Min (equatorial-equatorial) 111(1)

Max (equatorial-equatorial) 132(1)

Axial-axial 169(1)

Al(1)–O(1)–P(3) 147(1) Al(2)–O(7)–P(1) 142(1)

Al(1)–O(2)–P(2) 136(1) Al(2)–O(8)–P(3) 144(1

Al(1)–O(3)–P(1) 132(1) Al(2)–O(9)–P(2) 142(1)

Al(1)–O(4)–P(3) 154(1) Al(2)–O(10)–P(2) 137(1)

Al(3)–O(5)–P(1) 138(1) Al(3)–O(11)–P(3) 150(1)

Al(3)–O(6)–P(1) 134(1) Al(3)–O(12)–P(2) 129(1)

Al(1)–O(13)–Al(3) 125(1)


Guest molecules that fit the framework voidspace particularly well are generally referred to as

‘‘templates’’ [33] and they also tend to act as

structure directing agents. In other cases, when the

genesis of the porous structure is governed by

synthesis variables other than the presence of guest

molecules (e.g. hydrophobic clathrasils, zeosils,

silica-rich zeolite frameworks or some AlPO�s), the

stabilization of such (generally neutral) frame-works can be enhanced by (generally neutral) guest

molecules of small size, that only fill the channels

and cavities, where they are weakly linked to the

framework atoms through Van der Waals type

interactions [34]. Neither methylamine species in

IST-1 fills the void structure, but their participa-

tion in the nucleation and growth mechanism of

20 25 30 35 40 45

5 10 15 20 25 30 35 40 45

Fig. 8. The observed (top), calculated (middle) and difference (bottom) profiles for the Rietveld refinement of as-synthesized IST-1. To

show more detail, the scale for the second half of the pattern has been increased by a factor of 5 in the inset.


the AlPO4 framework and their structure-directing

role is readily apparent from the final structure.

Both types of methylamine species serve to stabi-

lize the final topology: one by expanding the co-

ordination sphere of one of the framework Alatoms, and the other through hydrogen bonding

with framework oxygens. A similar behavior was

observed in the case of zeolite Nu-10, where

polyamines act both electrostatically (in the prot-

onated form) and as pore fillers [35].

From the HETCOR spectrum and the crystal-

lographic data given in Table 6, the assignment of

Table 6

Al–O–P connectivities in IST-1 obtained from powder X-ray

diffraction

P(1) P(2) P(3)

Al(1) 1 1 2

Al(2) 1 2 1

Al(3) 2 1 1

27Al and 31P NMR lines is as follows. S1, S2 and

S3 correspond to 6-coordinated, 5-coordinated

and 4-coordinated aluminum, respectively and,

hence, are unambiguously attributed to crystallo-

graphic sites Al(1), Al(3) and Al(2), respectively.The assignment of the 31P NMR resonance can be

based on relative peak intensities of the 27Al–31P

HETCOR spectrum. It should be noticed here that

due to the complicated spin dynamics involved in

spin locking and polarization transfer of the

quadrupolar nuclei, the spectra generally are not

quantitative [36]. In particular, the transfer

strongly depends on the strength of the quadru-polar interaction. However, in the present assign-

ment, only the relative intensities between different

P atoms corresponding to the same Al atom, in

which case the influence of the quadrupolar cou-

pling constant is reduced, are used.

The relative intensities of S1-I cross-peaks are

1:1:1.7, for I1, I2 and I3, respectively, and thus, I3


is assigned to P(3). The remaining peak intensities

for 5-coordinated and (S2) 4-coordinated Al (S3)sites are consistent with the connectivities shown in

Table 6 (2.1:1:1 and 1:2:1.2, respectively). Clearly,

site I1 corresponds to P(1) and I2 to P(2). It should

be noted that these relative intensities did notchange significantly for the different offsets and

contact times used in the HETCOR experiments.

In order to assign the resonances in the 13C

MAS NMR spectrum to the two proposed loca-

tions of the methylamine species, ab initio calcu-

lations of the 13C NMR chemical shifts were

carried out; selected results are summarized in

Table 7. In aqueous solution, the experimentallymeasured chemical shift of methylamine is ca. 27.5

ppm. The calculated chemical shifts for an isolated

Table 7

Molecule

Methylamine+ 3H2O

Protonated methylamine+ 1H2O



Octahedral Al complex of methyl

and 1PO4 tetrahedron (capped wi

Protonated methylamine H-bonde

of 2PO4 tetrahedra (capped with

Same as above but protonated m

different position relative to frame

methylamine and for this molecule surrounded by

three water molecules are 26.6 and 25.3 ppm, re-

spectively. In aqueous solution, the experimental

chemical shift measured for protonated methyl-

amine is 26.2 ppm, very close to the value calcu-

lated for this molecule surrounded by three watermolecules (26.6 ppm). In addition, while isolated

protonated methylamine gives a calculated shift of

32.6 ppm, the addition of water molecules signifi-

cantly decreases the shift.

When methylamine is linked through the N-

atom to octahedral aluminum (see Table 7) the

calculated shift is 24.5 ppm, which is very close to

the shift of the IST-1 13C NMR resonance at 24.3ppm. When a protonated methylamine is hydro-

gen bonded to two ‘‘framework’’ oxygens of two

13C calculated shift (ppm)

25.3

29.1

26.1

26.6

amine, water, 2OH�

th OH�)

24.5

d to 2 framework O

waters)

28.6

ethylamine in a

work O

29.4


PO4 tetrahedra (see Table 7), the calculated shift is

28.6 or 29.4 ppm, depending on the orientation of

methylamine. This is close to ca. 28.0 ppm we

observe experimentally for one of the IST-1 reso-

nances, and much less than the value calculated for

isolated methylamine (32.6 ppm). In short, hy-drogen-bonding of methylamine decreases the shift

relative to protonated methylamine, but the exact

value depends somewhat on the orientation of

the molecule with respect to the framework. It is

concluded that the 13C NMR peak at 24.3 ppm

is most likely to be due to methylamine coor-

dinated to framework Al, and that at 28.0 ppm

to protonated methylamine hydrogen-bonded tothe framework. Thus, in these points, the NMR

evidence is fully consistent with the crystal struc-

ture.

7. Conclusions

A combination of advanced powder diffractionand NMR techniques have allowed the structure

of the novel aluminophosphate molecular sieve

IST-1 to be elucidated. It appears to be the first

example of a microporous material in which

methylamine molecules are linked directly through

their N atoms to framework Al atoms, probably in

the early stages of the structure hydrothermal

genesis. Additional methylammonium species areincorporated into the structure via hydrogen bonds

to framework oxygens, and the charge-balancing

hydroxyl group bridges between framework Al

atoms in the same 4-ring. All three extra-frame-

work species seem to stabilize the framework struc-

ture. The IST-1 framework, like that of IST-2 and

other AEN-type aluminophosphates, transforms

to another structure when water and methylamineare released upon heating.

Acknowledgements

Experimental assistance from the staff of the

Swiss–Norwegian Beamlines at the European

Synchrotron Radiation Facility in Grenoble isgratefully acknowledged. This work was sup-

ported in part by the Swiss National Science

Foundation. JLJ thanks the Spanish MEC for

their support in the form of a postdoctoral grant.

The Portuguese authors thank FCT, POCTI and

FEDER for financial support and Dr. P. Claro for

help with 13C NMR shifts calculations.

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Structure analysis of the novel microporous aluminophosphate IST1 using synchrotron powder...

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