LETTERS
A microdiffraction set-up for nanoporous
metal–organic-framework-type solids
CHRISTOPHE VOLKRINGER1 , DIMITRY POPOV2 , THIERRY LOISEAU1 *, NATHALIE GUILLOU1 ,
GERARD FEREY1 , MOHAMED HAOUAS1 , FRANCIS TAULELLE1 , CAROLINE MELLOT-DRAZNIEKS1,3 ,
MANFRED BURGHAMMER2 AND CHRISTIAN RIEKEL2
1
Institut Lavoisier—UMR CNRS 8180, Institut Universitaire de France, Université de Versailles Saint Quentin en Yvelines, 45, avenue des Etats-Unis,
78035 Versailles, France
2
ESRF, B.P. 220, 38043, Grenoble Cedex, France
3
Royal Institution of Great Britain, 24 Albemarle Street, London, W1S 4BS, UK
* e-mail: [email protected]
Published online: 16 September 2007; doi:10.1038/nmat1991
For the past decade, the emerging class of porous metal–organic
frameworks1–3 has been becoming one of the most promising
materials for the construction of extralarge pore networks in
view of potential applications in catalysis, separation and gas
storage. The knowledge of the atomic arrangements in these
crystalline compounds is a key point for the understanding of
the chemical and physical properties. Their crystal size limits
the use of single-crystal diffraction analysis, and synchrotron
radiation facilities4 may allow for the analysis of tiny crystals.
We present here a microdiffraction set-up for the collection
of Bragg intensities, which pushes down the limit to the
micrometre scale by using a microfocused X-ray beam of 1 µm.
We report the structure determination of a new porous metal–
organic-framework-type aluminium trimesate (MIL-110) from a
single crystal of a few micrometres length, showing very weak
scattering factors owing to the composition of the framework
(light elements) and very low density. Its structure is built up
from a honeycomb-like network with hexagonal 16 Å channels,
involving the connection of octahedrally coordinated aluminium
octameric motifs with the trimesate ligands. Solid-state NMR
(27 Al, 13 C, 1 H) and molecular modelling are finally considered for
the structural characterization.
In solid-state sciences, the development of knowledge is
strongly dependent on the determination of the crystal structure
of solids. The latter is easily accessible as soon as single crystals
of reasonable size (≥10 µm) are available. If not, ab initio
structure determination from powder diffraction data becomes
necessary, with its difficulties and its limitations, particularly in
terms of cell volume. It can therefore be anticipated that, in the
years to come, more and more new solids will be isolated in
powdered form, and beyond a certain degree of complexity their
structure, despite continuous technological improvements, will
remain unknown, and this will prevent possible applications for the
corresponding solids.
The future of the exploding domain of porous metal–organic
frameworks (MOFs)1,2 is particularly affected by the above remarks
because the new solids, more and more in powdered form, show
larger and larger cells3,5 , which can reach more than 700,000 Å3 in
MIL-101 for instance. For such volumes, without single crystals, it
becomes difficult or even impossible to reach a structural solution
5 µm
Figure 1 Scanning electron micrograph of hexagonal needle-like single
crystals of MIL-110. A crystal of 3× 3× 10 µm size was used for
synchrotron-radiation microdiffraction.
from ab initio methods. In the case of MOF compounds, it required
the development of new methods that combine targeted chemistry
and computer modelling to reach the solution6 and explain the
unprecedented properties for these solids. This applies in particular
to new aluminium-based MOF materials, rarely reported7–9 despite
their real interest for industrial applications owing to their relatively
low cost at the manufacturing scale10 .
A possibility to maintain single-crystal diffraction and its
related accuracy up to the largest cells of MOFs is to develop
synchrotron-radiation-diffraction techniques related to protein
crystallography4 , for data collection from very small microcrystals
(about 1−2 µm). This paper presents a new trend in this direction,
which is applied to the determination of a new three-dimensional
topology in the family of aluminium carboxylates, hardly accessible
from powder diffraction. The microdiffraction set-up developed at
the European Synchrotron Radiation Facility (ESRF) in Grenoble
enables for the first time single-crystal diffraction with a spot of
about 1 × 1 µm2 .
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a
b
AI(1)
b
AI(2)
a
c
d
b
c
Figure 2 Representation of the structure of MIL-110. a, View along the c axis showing the channels delimited by the discrete Al8 clusters and the trimesate group. b, View
of the Al8 cluster showing the three bioctahedral edge-shared units Al(2)–Al(2) capped by two Al(1) octahedra. The Al8 moiety is connected to nine carboxylate functions of
the trimesate molecules. In the ordered crystal structure (P63 22), only one site Al(2) is observed for the dimeric edge-shared bioctahedral units whereas the Al(2) sites are
split between two positions Al(2) and Al(3) in P-62c. c, View along the c axis showing the connection mode of the Al8 clusters with the trimesate species parallel to the walls
of the channels. d, The two types of connection of the two different aluminium octahedral units Al(1) and Al(2), Al(3) of the bioctahedral units. This shows the two possibilities
of Al(1)–Al(2,3) linkages resulting in the disordering situation. In the ordering structure (described in P63 22), only one (left) of the connection mode is observed. In the
disordered structure, the positions of the carboxylate groups are identical in the two different possibilities of connection of octahedra (orange, Al(1) octahedron; purple,
Al(2,3) octahedron).
The beam from an undulator is monochromated and focused
on the sample by a pair of mirrors, which enables us to reach a flux
density at the sample of up to 3 × 1010 photons s−1 µm−2 at about
0.97 Å wavelength. A set of micro-apertures is used for background
reduction11 . In order to reach the necessary rotational accuracy,
a new microgoniometer (see the Supplementary Information)
combining a low-wobble air-bearing spindle and a piezomicromanipulator carrying a magnetic-base sample support was
developed. The optical alignment precision was about 1 µm using
an integrated optical microscope with a low-vibration sample stage.
The crystal was rotated around a direction close to the six-fold axis
coinciding with the crystal elongation. It must be noted that our
previous attempts to collect correct Bragg-diffraction data using
other synchrotron stations were unsuccessful.
2
This new set-up enabled the study of porous aluminium
trimesates (1,3,5-benzene tricarboxylate or btc). In this system,
several phases exist, but with narrow ranges of stability, which
prevent the growth of large crystals. This study is devoted
to the solid Al8 (OH)12 {(OH)3 (H2 O)3 }[btc]3 ·nH2 O, hereafter
labelled MIL-110 (MIL standing for Materials of Institut
Lavoisier). It is obtained (see the Methods section) after a
hydrothermal treatment of a mixture of aluminium nitrate,
trimethyl 1,3,5-benzenetricarboxylate, nitric acid and water, which
leads to the formation of well-defined hexagonal rod-shaped
crystals of 5−30 µm and 0.5−3 µm section (Fig. 1). After collection
of the data using the new set-up, the structure was solved by a direct
method with SHELXS-86 (ref. 12) and refined with SHELXL-97
(ref. 13) software within the WinGX suite14 .
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a
AI1
a
AI2/AI3
δ iso = 5.1 p.p.m.
CQ = 1.81 MHz
ηQ = 0.55
Area = 26%
5.4
7.3
δ iso = 5.6 p.p.m.
CQ = 3.51 MHz
ηQ = 0.63
Area = 74%
2.3
3.1
8.2
9.3
c
b
δ iso = 4.6 p.p.m.
CQ = 1.97 MHz
ηQ = 0.51
20
10
20
δ iso = 5.4 p.p.m.
CQ = 3.69 MHz
ηQ = 0.60
0
(p.p.m.)
–10
15
10
5
(p.p.m.)
0
–5
–10
b
–20
135.3
Figure 3 Solid-state 27 Al NMR spectroscopy of MIL-110. a, 1D 27 Al{1 H} MAS
spectrum. b, 2D 27 Al MQMAS spectrum. c, Isotropic projection of 27 Al MQMAS
spectrum. The individual simulations of the two components are in purple and
green, the sum of these simulations are in blue, and the experimental spectra in red.
The three-dimensional framework of MIL-110 is built up from
the connection of inorganic aluminium octamers through btc
ligands delimiting large hexagonal channels (Fig. 2a). The real
structure determined from the XRD single-crystal analysis shows
atomic disorder in some parts of the octamer and necessitates
refining the structure using the space group P -62c and three Al
sites, two of them being occupied at half occupancy. This disorder
will be discussed later, but the crystal chemistry of MIL-110
structure is described more easily considering the ideal ordered
structure, estimated by using further computer modelling (starting
from the refined atomic coordinates found by XRD analysis) and
corresponding to space group P 63 22 with two aluminium sites
Al(1) and Al(2) in a ratio 1:3 (see the Supplementary Information
for more details). The ideal octamer (Fig. 2b) is formed of eight
octahedrally coordinated aluminium cations. The octamer contains
three edge-sharing bioctahedral dimers Al(2)–Al(2) and two
octahedra Al(1) each sharing three of their vertices with the triplet
of dimers. Nine carboxylate functions cap the octamer, linking
Al(1) to the Al(2) octahedra and the two Al(2) of the dimer. The
nature of the ligands surrounding each aluminium, oxo, hydroxo
and aquoligands with Al–O distances in the range 1.83–2.15 Å in
the real structure, is consistent with bond-valence calculations15 .
The Al(1) octahedra can be formulated as AlO3 (OH)3 . Their
oxygens originate from the carboxylates and each hydroxyl is
shared with one Al(2) octahedron. In the latter, the aluminium
atoms are AlO2 (OH)3 (H2 O) or AlO2 (OH)4 , depending on the
nature of the terminal group (hydroxo or aquo). The water or
hydroxyl group is terminal and, among the three OH groups, two
form the common edge of the dimer. In the disordered structure
(space group P -62c ), the Al(2) sites are split into two half-occupied
ones (Al(2) and Al(3)). This corresponds to two chiral orientations
of the Al8 cluster (Fig. 2d). This octamer is new and differs from
that described previously16 . We exclude twinning domains, which
could induce a disordering situation, as indicated in the Methods
section. The three-dimensional linkage between octamers and btc
is seen in Fig. 2c. To the best of our knowledge, this represents a
new structure type in the crystal chemistry of MOFs. It is worth
171.6
173.8
210
200
190
180
170.6
170
160 150
(p.p.m.)
140
130
120
110
100
Figure 4 Solid-state 1 H and 13 C NMR spectroscopy of MIL-110. a, 1 H MAS and
b, 13 C{1 H} CPMAS NMR spectra. A simulation and decomposition of the 1 H spectrum
are given.
noticing that along [001] each hexagon of the apparent honeycomb
lattice must be decomposed into two triangles (defined by three Al8
clusters) rotated away from each other by a 60◦ angle and shifted
by c/2 along [001]. The estimated free pore diameter is about
16 Å (on the basis of the ionic radius of 1.35 Å for oxygen), which
is in agreement with the quite high thermal parameters of atoms
delimiting the pores. The longest axes of thermal ellipsoids are
oriented towards the direction of the channels (see the figure in
Supplementary Information). The structure is nanoporous. From
the N2 adsorption isotherm at 77 K, a Brunauer–Emmett–Teller
(BET) specific surface of 1,400 m2 g−1 (Langmuir: 1,790 m2 g−1 ) is
deduced. These values are slightly greater than to those observed in
the MCM-41 type mesoporous materials17 with pore diameters up
to 100 Å.
The 27 Al magic-angle spinning (MAS) nuclear magnetic
resonance (NMR) spectrum of MIL-110 shows in the chemical
shift range of −15 to 10 p.p.m. a pattern of two overlapping
lines, specifying a sixfold coordination for aluminium sites.
27
Al{1 H} cross-polarized with high-power decoupling or just
straightforward 27 Al{1 H} high-power decoupled measurements
result in significantly narrowed spectra compared to 27 Al MAS.
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LETTERS
106
9
Vcryst (µm3)
104
10
8
7
4
102
6
5
3
MIL
2
1
100
1
10 –2
1010
1012
1014
1016
S
Figure 5 Irradiated crystal volume—V cryst —scaled against scattering
power—S—for a selected high-resolution single-crystal microdiffraction
experiment; adapted from refs 4,18. The scattering power has been scaled to an
average electron density S = (F000 /Vcell ) 2 l3 Vcryst (ref. 20); for experiments with a
beam size smaller than the crystal size, Vcryst corresponds to the irradiated volume
during a single exposure. Filled circle, MIL-110; open squares, inorganic structures:
1, CaF2 (ref. 21); 2, kaolinite (ref. 20); 3, birnessite (ref. 22); filled diamond, protein
crystals: 4 (ref. 23); 5 (ref. 24); 6 (refs 25,26); 7 (ref. 26); 8 (ref. 27); 9 (ref. 28);
10 (ref. 29).
This is consistent with Al sites with Al–H dipole–dipole couplings
as we would expect from Al–OH and Al−OH2 groups. A twodimensional 27 Al multiple-quantum MAS (MQMAS) spectrum
(Fig. 3a) shows two overlapping isotropic resonances with
contrasting anisotropic lineshapes owing to the difference in
quadrupolar coupling. The two aluminium sites show very close
chemical shift parameters but different quadrupolar coupling
constants CQ . After an iterative process of refinement between the
one- and two-dimensional spectra, the 27 Al{1 H} one-dimensional
spectrum (Fig. 3b) leads to two components with a relative
population ratio of 1:3 assigned to Al(1) (4f ) and Al(2 or 3)
(12i) sites, respectively. The larger quadrupolar CQ observed for
the Al(2 or 3) signals of the dimers, reflects the lower site point
symmetry for Al(2 or 3) than for Al(1). The 1 H MAS spectrum
(Fig. 4a) shows two signals at 2.3 and 3.1 p.p.m. with a 1:1 ratio
attributed to the corner- or edge-sharing bridging µ2 -OH within
the Al8 cluster. The signal at 5.4 p.p.m. corresponds to terminal
water molecules η-H2 O and/or η-OH bonded to Al. 1 H resonating
at 7–9 p.p.m. are the aromatic protons of btc. The absence of the
low field signal above 10 p.p.m. reflects the complete deprotonation
of carboxylic functions. In the 13 C{1 H} cross-polarization MAS
(CPMAS) spectrum (Fig. 4b), the signals at about 135 p.p.m. are
assigned to the aromatic carbons and the three resonances at 171,
172 and 174 p.p.m. to the three inequivalent carboxylate groups.
These three inequivalent carboxylic carbon atoms indicate that a
further ordering can be proposed, with a strict alternation of rightand left-handed Al8 units. However, as several solutions may be
given to this issue, we did not further our attempts to describe the
structure as precisely.
In conclusion, this paper describes an advanced technique in
microdiffraction using synchrotron radiation for solving from very
tiny single crystals the structure of a previously unknown phase.
Even though previous experiments with larger microbeams on the
known structures of CaF2 and kaolinite18 have shown that it is
possible to reach still smaller crystal sizes and scattering powers,
MIL-110 interestingly corresponds to the smallest crystal volumes
and scattering powers used until now for a high-resolution study4 .
4
Figure 5 shows the scattering power, S = (F000 /Vcell )2 l3 Vcryst (F000 ,
zero-order structure factor; Vcell , unit-cell volume; l, wavelength;
Vcryst , crystal volume), of the current structure compared with
other high-resolution microdiffraction studies4 . Radiation-damage
effects, which limit in particular protein microcrystallography, do
not apply here. The small beam size used in the present study, which
could be extended to nanobeams, even suggests the possibility of
studying single crystals within aggregates.
This breakthrough enabled characterization of the cationic
disorder on two possible orientations of the Al–OH–Al
bonding. Surprisingly, it affects only slightly the assembly
of trimesate moieties, because the carboxylate positions are
identical whatever the orientation of the Al–OH–Al linkage in
the Al8 building block. Such a detailed description could hardly
have been found from powder diffraction data. Single-crystal
information on micrometre-sized crystals efficiently provides, with
additional further data from modelling and NMR, very accurate
structure determinations.
METHODS
SYNTHESIS
MIL-110 was hydrothermally synthesized from a mixture containing
aluminium nitrate (Al(NO3 )3 9H2 O, Aldrich, 98%), trimethyl
1,3,5-benzenetricarboxylate (C6 H3 (CO2 CH3 )3 , 98%, Aldrich, denoted
Me3 btc), concentrated nitric acid (HNO3 ) 4 M and deionized water. The molar
composition was 1.5 Al (0.6659 g, 1.8 mmol), 1 Me3 btc (0.3025 g mg,
1.2 mmol), 3.3 HNO3 (1 ml, 4.0 mmol) and 226 H2 O (5 ml, 277.8 mmol). The
MIL-110 phase is obtained in very acidic conditions (pH ≈ 0) by adding
concentrated nitric acid. The starting mixture was placed in a Teflon cell, which
was heated in a steel Parr autoclave for 72 h at 210 ◦ C. The resulting powdered
pale yellow product was filtered off, washed with deionized water and dried in
air at room temperature. Optical microscope analysis indicated that the sample
is composed of elongated needle-like crystals 5−30 µm long. The scanning
electron micrographs show hexagonal shapes (0.5−2 µm diameter) of the
rodlike crystals.
SINGLE-CRYSTAL X-RAY DIFFRACTION
MIL-110 crystallizes with a hexagonal cell, a = b = 21.520(5) Å,
3
c = 13.021(1) Å, V = 5222.3(1) Å . The structure was solved in the space
group P -62c by direct methods, developed by successive difference Fourier
syntheses, and refined by full-matrix least squares on all F 2 data (obtained from
intensity values after correction for polarization of the X-ray beam) using
SHELXTL. Owing to the small crystal size, no absorption correction was
required. Structure solution indicated the positions of three unique aluminium
atoms (Al1, Al2 and Al3), but a disorder of two aluminium sites (Al2 and Al3)
is observed and the corresponding Al cations together with oxygen atoms
attached have been refined with an occupancy factor of 50%. The final
refinement including anisotropic thermal parameters of all non-hydrogen
atoms converged to R1 = 0.155. R1 = Fo | − |Fc /|Fo |, where Fo and Fc
are observed and calculated structure factors respectively, larger than 4σ(Fo ). A
twin refinement was done in order to check for the two possible twinning
possibilities: (1) a plane of symmetry perpendicular to the six-fold axis and (2)
a plane of symmetry perpendicular to the [110] vector. In both cases the
accepted space group of twin domains was P 31c (number 159). The twin
refinement showed, however, unreasonable anisotropic thermal parameters and
interatomic distances and Rfree values higher than 0.3 (R1 values calculated
from a ‘test’ set of reflections, which are not included in the refinement), and
was therefore discarded. All the calculations were carried out using the
SHELX-TL program on the basis of F 2 . The crystal data are given in the
Supplementary Information. The chemical formula for MIL-110 deduced
from the X-ray diffraction analysis is the following:
Al8 (OH)12 {(OH)3 ,(H2 O)3 }[btc]3 ·nH2 O. Crystallographic data and
parameters of experiments are gathered in the Supplementary Information.
SURFACE AREA STUDY
For the study of the BET surface area, the solid was activated with the following
procedure to remove the encapsulated species: 0.2 g of a MIL-110 sample was
placed in 60 ml methanol (high-performance liquid chromatography grade,
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99.9%, Aldrich) for 6 h in a Teflon-lined steel Parr autoclave heated at 100 ◦ C.
The powdered product was then filtered off, mixed with water for 5 h and
finally filtered off. The porosity of MIL-110 was estimated by a gas sorption
isotherm experiment in liquid nitrogen using the Micromeritics ASAP2010
apparatus (for surface area calculations, p/p0 range 0.01−0.2 (BET);
0.06−0.2 (Langmuir)). p is the gas vapour pressure at a given temperature T ;
p0 is the saturation vapour pressure at a given temperature T . The nitrogen
sorption experiment on the activated MIL-110 (degassed at 85 ◦ C overnight)
revealed a type I isotherm without hysteresis on desorption, which is
characteristic of a microporous solid. The measured BET surface area is
1,408(27) m2 g−1 with a micropore volume of 0.58 cm3 g−1 , and assuming a
monolayer coverage by nitrogen the Langmuir surface area is 1,792(3) m2 g−1 .
SOLID-STATE NMR
All NMR experiments were carried out on a Bruker Avance-500 spectrometer
equipped with a triple-resonance 2.5 mm probe. The Larmor frequencies for
1
H, 27 Al and 13 C are 500.13, 130.32 and 125.77 MHz, respectively. The chemical
shifts were referenced to TMS for 1 H and 13 C and to a 1 M Al(NO3 )3 solution
for 27Al. The 27Al{1 H} MAS spectrum was acquired under conditions of
high-power proton decoupling using a pulse length of 0.3 µs (π/12), a
repetition delay of 0.1 s and decoupling power of 99 kHz. The 27Al MQMAS
experiment was carried out using the standard Z-filter scheme19 with a
radio-frequency field of 127 kHz for excitation of triple-quantum (3Q)
coherences and for 3Q → 0Q conversion. For the 1 H experiment, a π/4
excitation pulse length of 3.8 µs was used with a recycle delay of 4 s. The
13
C{1 H} CPMAS experiment was run with MAS Hartmann–Hahn matching
conditions, 13 C radio-frequency fields of 70 kHz and a 1 H radio-frequency field
of 57.5 kHz. The MAS spinning speed was 30 kHz for 27 Al{1 H} and 1 H
experiments, 25 kHz for the 27 Al MQ experiment and 12.5 kHz for the 13 C{1 H}
CP experiment.
Received 29 January 2007; accepted 11 July 2007; published 16 September 2007.
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Correspondence and requests for materials should be addressed to T.L.
Supplementary Information accompanies this paper on www.nature.com/naturematerials.
Author contributions
C.V., N.G., T.L. and G.F. were involved in the synthesis and characterization of porous metal–organic
framework materials. D.P., M.B. and C.R. were involved in the development of the new
microdiffraction set-up at station ID 13 (ESRF). M.H. and F.T. were involved in the solid-state NMR
characterization. C.M.-D. was involved in computer molecular modelling.
Competing financial interests
The authors declare no competing financial interests.
Reprints and permission information is available online at http://npg.nature.com/reprintsandpermissions/
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5
A new microdiffraction set-up for nanoporous MOF-type
solids.
CHRISTOPHE VOLKRINGER1, DIMITRY POPOV2, THIERRY LOISEAU*1, NATHALIE GUILLOU1,
GERARD FEREY1, MOHAMED HAOUAS1, FRANCIS TAULELLE1, CAROLINE MELLOTDRAZNIEKS1,3, MANFRED BURGHAMMER2 AND CHRISTIAN RIEKEL2
1
Institut Lavoisier - UMR CNRS 8180, Institut Universitaire de France, Université de Versailles Saint
Quentin en Yvelines, 45, avenue des Etats-Unis, 78035 Versailles, France.
2
ESRF, B.P. 220, 38043, Grenoble Cedex, France
3
Royal Institution of Great Britain, 24 Albemarle Street, London, W1S 4BS, UK.
*
Correspondence should be addressed to E-mail: [email protected]. Phone: (33) 1 39 254 373.
Fax: (33) 1 39 254 358
Supplementary materials
Submitted to Nature Materials
Type of contribution: Letter
Version january 29, 2007
Revised version may 24, 2007
Second revised version july 12, 2007
© 2007 Nature Publishing Group
Schematic design of microgoniometer set-up with microscope in sample alignment position.
The microscope is translated out of the beam for data collection. Left image: overall view of
microgoniometer including focusing mirrors and supporting frame. A: crossed mirrors
chamber, B: sample-stage including x/y/z positioner and air bearing rotation axis, C:
microscope (Olympus), D: CCD detector (MAR 165); Right image: zoom onto sample
environment; E1: ionization chamber and guard aperture, E2: sample support (Hampton), E3:
piezo-micromanipulator (Kleindiek MM3A), E4: x/y sample stage (MICOS), E5: motorized
micro-beamstop, E6: rotating turret of microscope (Olympus)
© 2007 Nature Publishing Group
Table 1. Crystallographic data and parameters of the single-crystal XRD experiment for MIL110. Values in parentheses correspond to the outer resolution shell 1.10 – 0.93 Å.
_
P62c
21.520(5)
13.021(1)
0.93
22.08 (9.22)
86.7 (82.0)
0.109 (0.488)
21749 (7557)
1922 (692)
0.183 / 0.200
0.155 / 0.159
Space group
a, Å
c, Å
Highest resolution, Å
Mean I/V
Completeness
Rint
Reflections collected
Unique reflections
R1 / Rfree
R1 / Rfree (I > 2V(I))
Table 2. Fractional atomic coordinates and equivalent isotropic displacement parameters.
Atom
Al(1)
Al(2)
Al(3)
O(21)
O(22)
O(23)
O(31)
O(32)
O(33)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
O(1)
O(2)
O(3)
x
0.6667
0.6185(5)
0.5574(5)
0.6799(8)
0.6913(12)
0.5499(9)
0.5895(7)
0.4531(10)
0.6447(10)
0.5349(11)
0.5180(20)
0.5814(14)
0.5998(15)
0.4701(12)
0.5954(9)
0.4497(11)
0.5748(6)
0.6370(8)
y
0.3333
0.4455(4)
0.3832(5)
0.4107(6)
0.5417(8)
0.3586(9)
0.3237(8)
0.3069(14)
0.4602(8)
0.4595(11)
0.4782(18)
0.4285(15)
0.4128(13)
0.5107(12)
0.4054(8)
0.5215(10)
0.4222(6)
0.3795(8)
© 2007 Nature Publishing Group
z
0.5372(2)
0.6522(6)
0.6521(6)
0.6175(9)
0.6198(14)
0.7037(14)
0.6143(9)
0.6050(14)
0.7081(10)
0.3423(6)
0.2500
0.3409(7)
0.2500
0.2500
0.4435(6)
0.3285(5)
0.5189(4)
0.4434(5)
U(eq)
0.026(1)
0.048(2)
0.047(2)
0.034(3)
0.083(5)
0.049(3)
0.041(3)
0.110(7)
0.044(4)
0.096(4)
0.124(7)
0.106(5)
0.107(7)
0.075(6)
0.072(3)
0.164(7)
0.067(2)
0.124(4)
Table 3. Anisotropic displacement parameters.
Al1
Al2
Al3
O21
O22
O23
O31
O32
O33
C1
C2
C3
C4
C5
C6
O1
O2
O3
0.0361(15)
0.098(5)
0.077(4)
0.062(6)
0.180(13)
0.074(8)
0.055(6)
0.078(7)
0.105(9)
0.187(15)
0.25(2)
0.194(13)
0.26(2)
0.119(13)
0.145(11)
0.383(19)
0.118(6)
0.284(14)
0.0361(15)
0.063(4)
0.083(5)
0.038(6)
0.061(6)
0.073(8)
0.051(6)
0.208(17)
0.042(6)
0.163(13)
0.208(18)
0.218(16)
0.159(15)
0.125(18)
0.117(10)
0.306(14)
0.141(6)
0.231(11)
0.005(2)
0.009(4)
0.014(4)
0.012(7)
0.039(9)
0.019(9)
0.017(7)
0.041(13)
0.012(9)
0.030(6)
0.042(9)
0.016(6)
0.017(7)
0.034(9)
0.013(4)
0.011(5)
0.003(3)
0.007(4)
0.000
-0.006(3)
-0.001(3)
0.006(4)
0.024(6)
-0.003(5)
-0.021(5)
-0.046(9)
-0.001(4)
0.007(8)
0.000
0.019(8)
0.000
0.000
-0.007(7)
-0.002(6)
-0.003(4)
0.017(5)
0.000
0.001(4)
-0.008(3)
0.002(5)
0.017(8)
0.000(5)
-0.002(5)
-0.001(6)
-0.004(5)
-0.002(8)
0.000
0.015(7)
0.000
0.000
-0.010(7)
0.003(6)
-0.004(4)
0.017(6)
0.0180(8)
0.061(3)
0.066(3)
0.034(5)
0.084(5)
0.051(5)
0.026(5)
0.069(6)
0.058(4)
0.156(10)
0.211(17)
0.184(11)
0.195(16)
0.101(13)
0.111(7)
0.329(15)
0.110(4)
0.240(11)
Table 4. Bond lengths.
Bond
Al(1)-O(21)
Al(1)-O(31)
Al(1)-O(3)
Al(2)-O(23)
Al(2)-O(21)
Al(2)-O(33)#3
Al(2)-O(22)
Al(2)-O(2)
Al(2)-O(1)#4
Al(3)-O(31)
Al(3)-O(2)
Al(3)-O(33)
Length, Å
1.863(11) u 3
1.861(12) u 3
1.878(6) u 3
1.83(2)
1.872(16)
1.884(17)
1.916(19)
1.918(9)
2.149(15)
1.801(16)
1.881(9)
1.92(2)
Bond
Al(3)-O(1)#4
Al(3)-O(23)#3
Al(3)-O(32)
C(5)-O(1)
C(2)-C(5)
C(2)-C(1)
C(1)-C(3)
C(4)-C(3)
C(3)-C(6)
C(6)-O(3)
C(6)-O(2)
© 2007 Nature Publishing Group
Length, Å
1.953(11)
1.93(2)
2.10(2)
1.180(9) u 2
1.51(2)
1.371(10) u 2
1.452(14)
1.345(11) u 2
1.508(12)
1.268(11)
1.203(10)
COMPUTER MODELLING
The crystal structure of MIL-110 was determined in space group P-62c from single crystal,
with the occurrence of a disordered positioning of one of the aluminium atoms over two
crystallographic sites, Al(2) and Al(3), associated with the half occupancy of both sites. In
order to further build a fully ordered representation of this particularly complex structure,
MIL-110 was converted into P1, and the resulting Al(2)-Al(3) pairs were reduced to a single
atom, while retaining the maximum of symmetry during the elimination of Al atoms. The
space group symmetry for this new and ordered arrangement of metal centres was determined
automatically by the Find_Symmetry algorithm.a The resulting structure is fully ordered with
the symmetry P6322, and was further energy minimized at constant volume, using UFF
forcefieldb and Cerius2 suite of softwarec. The resulting coordinates are given as
supplementary information.
a.
b
c.
(a) Biosym Catalysis 2.0 Software Manuals 1993, Molecular Simulations Inc. USA.
(b) Accuracy in Powder Diffraction II (NIST Special Publication No.846) (Eds.: J. M.
Newsam, M. W. Deem, C. M. Freeman, E. Prince, J. K. Stalick), National Institute of
Standards and Technology, Bethesda, MD, USA, 1992, p 80.
Rappé, A.K., Casewit, C.J., Colwell, K.S., Goddard, W.A. & Skiff, W.M. UFF, a full
periodic table force field for molecular mechanics and molecular dynamics
simulations. J. Am. Chem. Soc. 114, 10024-10035 (1992).
Accelrys Cerius2 program suite, Materials Studio, Ms Modeling, San Diego USA &
Cambridge UK version 4.2.
Table 5. Fractional atomic coordinates of the ordered structure of MIL-110 calculated in
P6322
Atom
Al(2)
Al(1)
O(4)
O(5)
O(3)
C(8)
C(22)
C(10)
C(23)
C(21)
C(9)
O(1)
O(6)
O(7)
H(26)
H(28)
x
0.55178
0.66667
0.58937
0.45951
0.64075
0.53883
0.52033
0.57946
0.59737
0.47884
0.59567
0.43374
0.55075
0.64958
0.52215
0.62640
y
0.37504
0.33333
0.31293
0.29464
0.45418
0.45824
0.47967
0.42204
0.40263
0.52116
0.39974
0.51037
0.39052
0.39149
0.47101
0.37361
© 2007 Nature Publishing Group
z
0.66635
0.55892
0.64804
0.64962
0.68960
0.34322
0.2500
0.34633
0.2500
0.2500
0.45144
0.32005
0.52565
0.46628
0.41501
0.25000
THERMOGRAVIMETRIC ANALYSIS
Preliminary thermogravimetric and chemical analyses indicated that the as-synthesized MIL110 compound contained a significant amount of non reactive trimesate and nitrate species
which are assumed to be trapped within the channels. The solid was activated with the
following procedure in order to remove the encapsulated species: 0.2 g of a MIL-110 sample
was placed in 60 ml methanol (hplc grade 99.9% Aldrich) for 6 hours in a Teflon-lined steel
Parr autoclave heated at 100°C. The powdered product was then filtered off, mixed with water
for 5 hours and finally filtered off.
The thermogravimetric analysis (under O2, 1°C.min-1, TA Instrument 2050) was performed
with an activated MIL-110 sample washed in water for 6 hours. It shows a two-step weight
loss. The first event is assigned to the continuous removal of water. It corresponds to 44 % at
380°C and | 48 water molecules per Al8 unit (calc: 45.4 %). It includes the free molecules
trapped within the cavities and water bonded to aluminum atoms. Calculated amount of the
terminal bonded water/hydroxyl molecules is 5.7 % (6 H2O / Al8) and the removal of such
species may be attributed between 70 and 200°C (observed weight loss: 7.5 %). The second
weight loss is attributed to the departure the trimesate ligands from 380 up to 580°C (obs:
35.5 %; calc: 33.1 %). The final residue is Al2O3 with a remaining weight of 20.5 % (calc:
21.4 %). The deduced chemical formula for MIL-110 is Al8(OH)12{(OH)3,(H2O)3}[btc]3·42
H2O.
100
90
80
70
60
50
40
30
20
10
0
0
100
200
300
400
TG curve of activated MIL-110 (under O2, 1°C/min)
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500
600
Nitrogen gas sorption isotherm at 77K for MIL-110
450
400
Vol (cm3/g)
350
300
250
200
150
100
50
0
0
0.2
0.4
0.6
0.8
1
Relative pressure (p/p0)
N2 gas adsorption isotherm at 77K for the activated MIL-110. p/p0 is the ratio of gas pressure
(p) to saturation pressure (p0) with p0 = 766.4 mm (Hg).
© 2007 Nature Publishing Group
View of the structure of MIL-110 along c, showing atomic thermal ellipsoids.
© 2007 Nature Publishing Group