Rod packings and metal-organic frameworks constructed from rod-shaped secondary building units

Article abstract of DOI:10.1021/ja045123o

The principal structure possibilities for packing infinite rod-shaped building blocks are described. Some basic nets derived from linking simple rods (helices and ladders) are then enumerated. We demonstrate the usefulness of the concept of rod secondary

Full text of DOI:10.1021/ja045123o

Published on Web 01/13/2005
Rod Packings and Metal-Organic Frameworks Constructed
from Rod-Shaped Secondary Building Units
Nathaniel L. Rosi,† Jaheon Kim,†,§ Mohamed Eddaoudi,†,| Banglin Chen,†,
Michael O’Keeffe,*,‡ and Omar M. Yaghi*,†
Contribution from the Departments of Chemistry, UniVersity of Michigan,
Ann Arbor, Michigan 48109, and Arizona State UniVersity, Tempe, Arizona 85287
Received August 12, 2004; E-mail: mokeeffe@asu.edu; oyaghi@umich.edu
Abstract: The principal structure possibilities for packing infinite rod-shaped building blocks are described.
Some basic nets derived from linking simple rods (helices and ladders) are then enumerated. We
demonstrate the usefulness of the concept of rod secondary building units in the design and synthesis of
metal-organic frameworks (MOFs). Accordingly, we present the preparation, characterization, and crystal
structures of 14 new MOFs (named MOF-69A-C and MOF-70-80) of 12 different structure types, belonging
to rod packing motifs, and show how their structures are related to basic nets. The MOFs reported herein
are of polytopic carboxylates and contain one of Zn, Pb, Co, Cd, Mn, or Tb. The inclusion properties of the
most open members are presented as evidence that MOF structures with rod building blocks can indeed
be designed to have permanent porosity and rigid architectures.
Introduction
linked by benzene units to produce a primitive cubic net, b.
Simplification of MOF structures in this way has led us to fully
The design and synthesis of metal-organic frameworks
(MOFs) has yielded a large number of structures which have
been shown to have useful gas and liquid adsorption properties.1
In particular, porous structures constructed from discrete metal-
carboxylate clusters and organic links have been shown to be
amenable to systematic variation in pore size and functionality,
an aspect that has led to the synthesis of MOFs capable of
remarkable methane and hydrogen storage properties.1c-f The
permanent porosity of such MOFs is imparted by the structural
properties of the metal-carboxylate clusters, where each metal
ion is locked into position by the carboxylates to produce rigid
entities of simple geometry, referred to as secondary building
units (SBUs). In the interpretation and prediction of MOF
structures, the SBUs are considered as the “joints” and the
organic links as the “struts” of the underlying net. MOFs based
on discrete shapes (triangles, squares, tetrahedra, etc.) have been
synthesized and studied. An illustrative example is MOF-5
where the metal-carboxylate structure, a, is an octahedral SBU
enumerate and describe the principal topological possibilities
available for the assembly of various discrete SBU geometries.2
Indeed, the large majority of structural and sorption studies
have been done on MOFs of discrete SBUs, yet the analogous
chemistry involving infinite rod-shaped SBUs remains largely
unexplored. We recently found that rod-shaped metal-carboxy-
late SBUs provide means to accessing MOFs that do not
interpenetrate due to the intrinsic packing arrangement of such
(1) MOFs with porous properties: (a) Li, H.; Eddaoudi, M.; O’Keeffe, M.;
Yaghi, O. M. Nature 1999, 402, 276-279. (b) Chae, H. K.; Siberio-Perez,
D. Y.; Kim, J.; Go, Y.; Eddaoudi, M.; Matzger, A. J.; O’Keeffe, M.; Yaghi,
O. M. Nature 2004, 427, 523-527. (c) Eddaoudi, M.; Kim, J.; Rosi, N.;
Vodak, D.; Wachter, J.; O’Keeffe, M.; Yaghi, O. M. Science 2002, 295,
469-472. (d) Rosi, N. L.; Eckert, J.; Eddaoudi, M.; Vodak, D. T.; Kim,
J.; O’Keeffe, M.; Yaghi, O. M. Science 2003, 300, 1127-1129. (e) Rowsell,
J. L. C.; Millward, A. R.; Park, K. S.; Yaghi, O. M. J. Am. Chem. Soc.
2004, 126, 5666-5667. (f) Noro, S.; Kitagawa, S.; Kondo, M.; Seki, K.
Angew. Chem., Int. Ed. 2000, 39, 2081-2084. (g) Barea, E.; Navarro, J.
A. R.; Salas, J. M.; Masciocchi, N.; Galli, S.; Sironi, A. J. Am. Chem. Soc.
2004, 126, 3014-3015. (h) Serpaggi, S.; Luxbacher, T.; Cheetham, A. K.;
Ferey, G. J. Solid State Chem. 1999, 145, 580-586. Chiral MOFs: (i)
Cui, Y.; Evans, O. R.; Ngo, H. L.; White, P. S.; Lin, W. B. Angew. Chem.,
Int. Ed. 2002, 41, 1159-1162. (j) Seo, J. S.; Whang, D.; Lee, H.; Jun, S.
I.; Oh, J.; Jeon, Y. J.; Kim, K. Nature 2000, 404, 982-986. (k) Kepert, C.
J.; Prior, T. J.; Rosseinsky, M. J. J. Am. Chem. Soc. 2000, 122, 5158-
5168. Porphryin-containing MOFs: (l) Diskin-Posner, Y.; Dahal, S.;
Goldberg, I. Angew. Chem., Int. Ed. 2000, 39, 1288-1292. (m) Carlucci,
L.; Ciani, G.; Proserpio, D. M.; Porta, F. Angew. Chem., Int. Ed. 2003, 42,
317-322. (n) Kosal, M. E.; Chou, J. H.; Wilson, S. R.; Suslick, K. S. Nat.
Mater. 2002, 1, 118-121. Interpenetrated MOFs: (o) Evans, O. R.; Wang,
Z. Y.; Xiong, R. G.; Foxman, B. M.; Lin, W. B. Inorg. Chem. 1999, 38,
2969-2973. (p) Carlucci, L.; Ciani, G.; Macchi, P.; Proserpio, D. M. Chem.
Commun. 1998, 17, 1837-1838. (q) Klein, C.; Graf, E.; Hosseini, M. W.;
De Cian, A. New J. Chem. 2001, 209, 207-209. (r) Batten, S. R.; Robson,
R. Angew. Chem., Int. Ed. 1998, 37, 1461-1494. Other prominent examples
of MOFs: (s) Kiang, Y. H.; Gardner, G. B.; Lee, S.; Xu, Z.; Lobkovsky,
E. B. J. Am. Chem. Soc. 1999, 121, 8204-8215. (t) Braga, D.; Maini, L.;
Polito, M.; Mirolo, L.; Grepioni, F. Chem.-Eur. J. 2003, 9, 4362-4370.
(u) Zhao, H.; Heintz, R. A.; Ouyang, X.; Dunbar, K. R.; Campana, C. F.;
Rogers, R. D. Chem. Mater. 1999, 11, 736-746. (v) Cotton, F. A.; Lin,
C.; Murillo, C. A. Acc. Chem. Res. 2001, 34, 759-771. (w) Oh, M.;
Carpenter, G. B.; Sweigart, D. A. Acc. Chem. Res. 2004, 37, 1-11. (x)
Lu, J. J.; Mondal, A.; Moulton, B.; Zaworotko, M. J. Angew. Chem., Int.
Ed. 2001, 40, 2113-2116.
† University of Michigan.
‡ Arizona State University.
§ Present address: Department of Chemistry and CAMDRC, Soongsil
University, Seoul 156-743, Korea.
| Present address: Department of Chemistry, University of South Florida,
Tampa, FL 33620.
Present address: Department of Chemistry, University of Texas-Pan
American, Edinburg, TX 78541.
9
1504
J. AM. CHEM. SOC. 2005, 127, 1504-1518
10.1021/ja045123o CCC: $30.25 © 2005 American Chemical Society

Rod Packings and Metal−Organic Frameworks
A R T I C L E S
Table 1. Invariant Rod Packings and Their Associated Netsa
symbol
type
sp. gr.
[uvw]
x0,y0,z0
rod group
net vertices
Z
net
d/l
1
parallel
parallel
parallel
parallel
layers
layers
layers
layers
3-way
3-way
4-way
4-way
4-way
4-way
P6/mmm
P4/mmm
P6/mmm
P6/mmm
I41/amd
P42/mmc
P6222
[001]
[001]
[001]
[001]
[010]
[100]
[010]
[100]
[100]
[100]
[111]
[111]
[111]
[111]
1/3,2/3,0
0,0,0
p6hm2
1/3,2/3,0
0,0,0
5
6
6
8
3
4
3
4
3
4
3
5
3
3
bnn
pcu
free
free
free
free
free
free
free
free
1
2
p4/mmm
pmmm
p6/mmm
pmcm
pmmm
p2221
p222
3
1/2,0,0
0,0,0
1/2,0,0
kag
4
0,0,0
hex
ths-z
cds
bto-z
qzd
bmn
nbo
sgn
gan
utb-z
sgn-c
5
0,0,0
0,1/4,0
6
0,0,0
0,0,0
7
1/2,0,1/6
0,0,0
1/2,0,1/6
0,0,0
8
P6222
9∏
10∏*
11∑
12Γ
13Ω
14∑*
I4132
1/4,0,0
1/2,0,0
1/3,2/3,0
0,0,0
p4122
p42/mmc
p312
1/4,0,0
Pm3hn
1/2,0,0
1
I4132
1/8,1/24,7/24
1/8,1/8,1/8
1/4,5/12,1/12
1/8,1/24,7/24
1/x6
x(2/3)
x(2/3)
1/x6
Ia3hd
I432
Ia3hd
p3hc
1/3,2/3,0
1/3,2/3,0
p312
p312
a Z is the coordination number of the net. Under “net” is the name of the net.2f The number under “symbol” corresponds to that shown in Figure 1. The
3
rod group is the symmetry of the rod. For nets named ths-z, cds, bto-z, and qzd, c/a ) 2, 2, /2, 3, respectively, for equal links. Number 14 (∑*) is two
intergrown packings of number 11 (∑). For rod symmetries, see, for example, ref 7. For net symbols, see ref 2d,e.
rods in the crystal structure.3 In this contribution, we present
strategies for the design and construction of porous structures
from rod-shaped building blocks. Specifically, we (a) provide
an account of the geometric principles of basic rod packing and
nets based on them, (b) identify the principal topological
possibilities and the most likely structures that could form from
rods, (c) adduce a number of new MOFs with structures con-
structed according to these geometric principles, and (d) show
that, similar to MOFs of discrete SBUs, MOFs based on rod
SBUs can also have stable architectures and permanent porosity.
When there are points on the rod axes that join neighboring
rods, then we can associate nets with each one of those rod
packings. In this context, it is useful to recognize two kinds of
distance: the distance between points along the rod having
length l, and that connecting two rods having length d, d. The
ratio d/l is an important parameter in the design of MOF
structures based on rod packings, for some of which this ratio
is fixed as specified in Table 1. We note that in MOF structures
described here, the metal-carboxylate units (i.e., SBUs)
represent the rods and the organic units link the rods together.
Geometric Principles of Rod Packing
Simple Rod Geometries and Associated Nets
A rod is a 1-periodic three-dimensional structure with a linear
axis that is determined by specifying a point on the axis (x0,y0,z0)
and its direction [uVw], c.4 The special rod packings correspond
to invariant line positions (i.e., special positions) in which lines
(rod axes) lie along the directions of nonintersecting symmetry
axes.5 Thus, for packing of equivalent rods, it is sufficient to
specify just one rod and the space group. There are 14 invariant
structures, and they are so described in Table 1 and are
illustrated in Figure 1.
The simplest rods consist of points on a one-dimensional
lattice. In the rod packings shown in Figure 1, the linear parts
are rods of this kind. The next simplest rods are helices. Linking
these in the simplest manner leads to 3-coordinated nets (each
vertex is linked to two others on the helix and to one on a
different helix) as shown in Figure 2.
For linking 31 or 32 helices, there are only two nets with one
kind of vertex: one with helices of one hand and the other with
helices of both hands. Wells calls them (8,3)-a and (8,3)-b,
respectively;6 in our system of naming (using a three letter
code),2d-f they are eta and etb and they have symmetries P62-
22 and R3hm, respectively (Figure 2).
4-fold helices can be similarly linked. In its most symmetrical
form, the linkage of 41 (or 43) helices is cubic (symmetry I41-
32) and corresponds to the srs (Si in SrSi2) net [Wells’ (10,3)-
a]6 with three sets of nonintersecting 41 (or 43) axes. The
simplest mode of linking 41 and 43 helices combined in one
structure produces a tetragonal (I41/amd) structure,6 which we
label lig as the topology is the same as the Ge net in LiGe
(Figure 2).7
Next in simplicity are rods of quadrangles linked by sharing
opposite edges (ladders). There are two simple ways in which
ladders can be linked to form 4-coordinated nets: either with
the rungs parallel as in sra (Al net in SrAl2) or at an angle to
each other (irl) as shown in Figure 2.8 Note that in either case
the sides of the ladder form a double zigzag.7 If successive rungs
of a ladder are at right angles, one obtains a simple rod that
(2) (a) Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi,
M.; Kim, J. Nature 2003, 423, 705-714. (b) O’Keeffe, M.; Eddaoudi, M.;
Li, H.; Reineke, T. M.; Yaghi, O. M. J. Solid State Chem. 2000, 152, 3-20.
(c) Eddaoudi, M.; Moler, D.; Li, H.; Chen, B.; Reineke, T. M.; O’Keeffe,
M.; Yaghi, O. M. Acc. Chem. Res. 2001, 34, 319-330. (d) Delgado-
Friedrichs, O.; O’Keeffe, M.; Yaghi, O. M. Acta Crystallogr. 2003, A59,
22-27. (e) Delgado-Friedrichs, O.; O’Keeffe, M.; Yaghi, O. M. Acta
Crystallogr. 2003, A59, 515-525. (f) Crystallographic data for all structures
assigned symbols in this paper are to be found at http://okeeffe-ws1.la.asu.edu/
RCSR/home.htm.
(3) Rosi, N. L.; Eddaoudi, M.; Kim, J.; O’Keeffe, M.; Yaghi, O. M. Angew.
Chem., Int. Ed. 2002, 41, 284-287.
(4) O’Keeffe, M.; Andersson, S. Acta Crystallogr. 1977, A33, 914-923.
(5) O’Keeffe, M.; Ple´vert, J.; Watanabe, Y.; Teshima, Y.; Ogawa, T. Acta
Crystallogr. 2001, A57, 110-111.
(6) Wells, A. F. Three-dimensional nets and polyhedra; Wiley: New York,
1977.
(7) O’Keeffe, M.; Hyde, B. G. Crystal Structures I: Patterns and Symmetry;
Mineral. Soc. Am.: Washington, D.C., 1996.
(8) O’Keeffe, M. Phys. Chem. Miner. 1995, 22, 504-506.
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J. AM. CHEM. SOC. VOL. 127, NO. 5, 2005 1505

A R T I C L E S
Rosi et al.
Figure 1. Invariant rod packings. The numbers correspond to the numbers in Table 1. In 1-4, the rods are red and almost normal to the page. For 5-13,
they are colored red, green, blue, and yellow.
Figure 2. Nets formed by linking rods. Top row: linked helices. Bottom row left: linked ladders. Right: ladders linked to finite groups.
consists of tetrahedra sharing opposite edges, as exemplified
by SiS4 tetrahedra in SiS2.
structure, fry, in which the planar 4-coordinated point is replaced
by a square (Figure 2).
Rods can be combined with finite units to provide an almost
endless variety of nets. We are content here just to show two
simple examples of relevance to the next section that are
discussed further there. These are frl in which zigzag ladders
are joined to a point and the related partially augmented
We should note that, most commonly, linked rods will be
parallel because the spacing along a rod, l (translation), is
determined by the rod itself and the spacing between rods, d, is
determined by the length of the links. However, if rods are not
parallel, the spacing along rods and between rods may not be
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Rod Packings and Metal−Organic Frameworks
A R T I C L E S
Figure 3. Development of the MIL-47 structure: the inorganic SBUs are chains of corner-sharing V octahedra (red ) O, blue ) V, black ) C) (a,b) in
which the carboxylate carbon atoms can be connected to form a zigzag ladder (b). When linked with organic spacers, the SBUs form crystalline frameworks
that can be represented as ladders linked together as in the sra net (c) (Figure 2). Atomic coordinates from single-crystal data were used to produce each
diagram. (Note: MIL-47 and MOF-71 are isostructural, and the crystal data for MOF-71 were used to make this diagram. For MOF-71: red ) O, blue )
Co, black ) C.)
Experimental Section
independent and thus a critical d/l ratio must be met to obtain
the corresponding nets of bmn, nbo, sgn, gan, utb-z, and sgn-c
(cf., Table 1 and Figure 1).
Synthesis and Characterization of MOFs, Abbreviations, and
General Procedures. For easy reference, the formulas for MOF-69-
80, explanation of guest abbreviations and organic carboxylates, and
crystal unit cell parameters are listed in Table 2. Unless otherwise
indicated, chemicals were purchased from the Aldrich Chemical Co.
and used as received. HPDC and ATC organic linkers were synthesized
according to published procedures.13 HPDC was protected, dehydro-
genated, and then deprotected to yield PDC.14
Elemental microanalyses were performed by The University of
Michigan, Department of Chemistry, using a Perkin-Elmer CHN 2400
Series II thermal analysis system. Thermogravimetric analysis (TGA)
was performed in house using a TA Q500 thermal analysis system.
Fourier transform infrared (FT-IR) spectra were measured using a
Nicolet FT-IR Impact 400 system. FT-IR samples were prepared as
KBr pellets. Absorptions are described as follows: strong (s), medium
(m), weak (w), shoulder (sh), and broad (br).
X-ray powder diffraction patterns were measured using a Bruker
AXS D8 Advance powder diffractometer at 40 kV, 40 mA for Cu KR
(λ ) 1.5406 Å), with a scan speed of 0.15 s/step and a step size of
0.417°. The simulated powder patterns were calculated using single-
crystal X-ray diffraction data and were processed by the PowderCell
2.3 program.
The single-crystal structural determinations were done using a Bruker
SMART APEX CCD diffractometer. The SMART software was used
for data acquisition, SAINT for data extraction, SADABS for the
absorption corrections, and SHELXTL for the structure solution and
refinement. All structures were solved with direct methods. Data
collection, structure solutions, and refinement, including metric pa-
rameters, have been deposited as Supporting Information.
Recognition of Rod Secondary Building Units (SBUs)
The description of MOF geometry in terms of linked SBUs
is fundamental to rationalization and prediction of MOF net
topologies.2c Here, we refer to Figure 3 to illustrate how rod
SBUs are characterized. A simple example of an infinite SBU
was recently found in the structure of MIL-47 with a framework
of stoichiometry VO(BDC) (BDC ) 1,4-benzenedicarboxylate).9
According to the present approach, the SBU consists of infinite
(-O-V-)∞ rods (Figure 3a) with carboxylate O atoms com-
pleting octahedral coordination around V to result in an infinite
rod of VO6 octahedra sharing opposite corners (Figure 3b). The
carboxylate C atoms are at the vertices of a zigzag ladder SBU.
Joining the ladders through the -C6H4- links results in a three-
dimensional net of the sra topology (Figure 3c; cf., Figure 2).
The same structure is obtained with [-(OH)-V-]∞ rods (VIII
replacing VIV). Additionally, MIL-53, consisting of [-(OH)-
10
(Cr)-]∞ rods, and MOF-71 (Figure 3) (reported below),
consisting of [-O-Co-]∞ rods, are both isostructural to MIL-
47. The same rod appears in another structure, MIL-60,11 in
which [-V-O-]∞ rods are linked by 1,2,4,5-benzenetetracar-
boxylate and the topology is one of the ladder rods linked to
rectangles to form a 3,4-coordinated net that we symbolize fry
(Figure 2).12
In the sections that follow, we present the synthesis and
characterization of MOFs constructed from rod SBUs, and we
relate their underlying topologies to those of rod packing
arrangements and nets.
Gas Sorption Isotherms. Sorption isotherm measurements were
performed by monitoring the weight change as a function of relative
pressure. Data were acquired on a CAHN 1000 electrogravimetric
balance using a 1 mg scale (sensitivity 1 µg). A known weight (100-
150 mg) of the as-synthesized starting material was placed in a
cylindrical quartz bucket (height ) 30 mm, and o.d. × i.d. ) 19 × 17
mm) and was then subjected to a heating program at pressures as low
as 1 × 10-5 Torr to remove the guests and produce the evacuated
(9) Barthelet, K.; Marrot, J.; Riou, D.; Fe´rey, G. Angew. Chem., Int. Ed. 2002,
41, 281-284.
(10) Serre, C.; Millange, F.; Thouvenot, C.; Nogue`s, M.; Marsolier, G.; Loue¨r,
D.; Fe´rey, G. J. Am. Chem. Soc. 2002, 124, 13519-13526.
(11) (a) Barthelet, K.; Riou, D.; Nogues, M.; Fe´rey, G. Inorg. Chem. 2003, 42,
1739-1743. (b) For a related structure, see: Sanselme, M.; Grene`che, J.
M.; Riou-Caveliec, M.; Fe´rey, G. Chem. Commun. 2002, 2172-2173.
(12) It is somewhat arbitrary whether we consider the anionic SBU derived from
benzenetetracarboxylate as a single vertex 4-coordinated to four rods (frl)
or as a square with each vertex linked to a rod (fry). The process of
replacing a vertex with its coordination figure, as in the transformation frl
f fry, we call augmentation, and we usually consider nets and their
augmented derivatives as essentially the same topology.
(13) HPDC synthesis: (a) Connor, D. M.; Allen, S. D.; Collard, D. M.; Liotta,
C. L.; Schiraldi, D. A. J. Org. Chem. 1999, 64, 6888-6890. ATC
synthesis: (b) Newkome, G. R.; Nayak, A. R.; Moorefield, C.; Baker, G.
J. Org. Chem. 1992, 57, 358-362.
(14) PDC was prepared using the procedure described in: Musa, A.; Sridharan,
B.; Lee, H.; Mattern, D. L. J. Org. Chem. 1996, 61, 5481-5484.
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A R T I C L E S
Rosi et al.
Table 2. Explanation of Abbreviations for Organic Carboxylates
and Guest Molecules and Crystal Unit Cell Parameters
“guest-free” form. Pressures were measured with two MKS Baratron
transducers 622A with the range covering 0-10 and 0-1000 Torr
(accuracy 0.25%). The adsorbate was added incrementally. A point
isotherm was recorded at equilibrium (obtained when no further weight
change was observed and the pressure changes were less than 1 mm
Torr/min).
The N2, Ar, and CO2 adsorbates were of UHP grade. The temperature
of each sample was controlled using a refrigerated bath of liquid
nitrogen (-195 °C) for N2 and Ar sorption measurements. All organic
solvents were GC grade 99.9%, purchased from Aldrich Chemical Co.
and stored over molecular sieves. The nitrogen apparent Langmuir
surface area was estimated using the Langmuir equation and assuming
monolayer coverage of N2 using a cross-sectional area of 16.2
Å2/molecule. The pore volume was calculated by extrapolation of the
Dubinin-Radushkevich equation, assuming the sorbate is in a liquidlike
state and a pore-filling sorption process.15
Synthesis of Compounds. Zn3(OH)2(BPDC)2‚(DEF)4(H2O)2: MOF-
69A. A solid mixture of Zn(NO3)2‚6H2O (24.6 mg, 0.083 mmol) and
4,4′-biphenyldicarboxylic acid (H2BPDC) (10 mg, 0.041 mmol) was
dissolved in a 20 mL vial containing DEF (12 mL), 30% H2O2 (0.40
mL), and CH3NH2 (0.20 mL, 70.3 mM in DMF). The mixture was
allowed to stand in a capped vial for 7 d at room temperature. Colorless
crystals of MOF-69A were collected and air-dried (21 mg, 86.1% yield
based on H2BPDC). This compound is insoluble in common organic
solvents. Anal. Calcd for C48H66N4O16Zn3 ) MOF-69A: C, 50.08; H,
5.78; N, 4.87; Zn, 17.04. Found: C, 50.81; H, 5.48; N, 5.16; Zn, 16.13.
FT-IR (KBr 4000-400 cm-1): 3415 (br), 3071 (w), 2974 (w), 2935
(w), 2876 (w), 1675 (s), 1642 (s), 1596 (s), 1548 (m), 1404 (s), 1313
(w), 1263 (w), 1218 (w), 1178 (w), 1110 (w), 1005 (w), 942 (w), 845
(w), 823 (w), 801 (w), 774 (s), 702 (w), 686 (w), 645 (w), 584 (w),
468 (w).
Zn3(OH)2(NDC)2‚(DEF)4(H2O)2: MOF-69B. A solid mixture of
Zn(NO3)2‚6H2O (24.6 mg, 0.083 mmol) and 2,6-naphthalenedicarbox-
ylic acid (H2NDC) (8.9 mg, 0.041 mmol) was dissolved in a 20 mL
vial containing DEF (12 mL), 30% H2O2 (0.40 mL), and CH3NH2 (0.20
mL, 70.3 mM in DMF). The mixture was allowed to stand in a capped
vial for 7 d at room temperature. Colorless crystals of MOF-69B were
collected and air-dried (18 mg, 80.4% yield based on H2NDC). This
compound is insoluble in common organic solvents. Anal. Calcd for
C44H62N4O16Zn3 ) MOF-69B: C, 48.08; H, 5.69; N, 5.10; Zn, 17.85.
Found: C, 48.28; H, 5.13; N, 5.02; Zn, 17.76. FT-IR (KBr 4000-400
cm-1): 3440 (br), 2977 (w), 2935 (w), 2882 (w), 1645 (s), 1607 (s),
1580 (s), 1502 (w), 1408 (s), 1362 (m), 1264 (w), 1203 (w), 1104 (w),
929 (w), 790 (m), 647 (w), 482 (w).
Zn3(OH)2(1,4-BDC)2‚(DEF)2: MOF-69C. In a 20 mL vial, a solid
mixture of 1,4-benzenedicarboxylic acid (1,4-BDC) (33.0 mg, 0.199
mmol) and Zn(NO3)2‚6H2O (177 mg, 0.596 mmol) was dissolved in
DEF (4.883 mL). Deionized H2O (0.117 mL) was added to the reaction
solution, and the vial was capped and heated for 15 h in a 100 °C
isotemp oven. The vial, containing colorless rodlike crystals (67 mg,
89% yield based on H2BDC), was removed from the oven while hot.
The crystals were collected and washed with DEF (3 mL × 3). Anal.
Calcd for C26H32N2O12Zn3 ) MOF-69C: C, 41.05; H, 4.24; N, 3.68.
Found: C, 40.62; H, 4.29; N, 3.53. FT-IR (KBr 4000-400 cm-1): 3342
(br), 2984 (m), 2940 (w), 2884 (w), 1650 (s), 1584 (s), 1504 (m), 1450
(m), 1407 (s), 1298 (w), 1259 (w), 1213 (w), 1157 (w), 1109 (m), 1019
(m), 915 (w), 826 (s), 751 (s), 647 (w), 599 (m), 527 (m), 435 (m).
Pb(1,4-BDC)(C2H5OH)‚(C2H5OH): MOF-70. In a 20 mL vial,
lead(II) nitrate (60 mg, 0.181 mmol) and 1,4-benzenedicarboxylic acid
(H2BDC) (30 mg, 0.181 mmol) were dissolved in DMF (1 mL) and
then diluted with ethanol (9 mL). To this solution was added hydrogen
peroxide aqueous solution (30%) (0.1 mL) to give a clear colorless
solution. Eight vials of this solution were placed along the perimeter
a BPDC ) 4,4′-biphenyldicarboxylate; NDC ) 2,6-naphthalenedicar-
boxylate; 1,4-BDC ) 1,4-benzenedicarboxylate; 1,3-BDC ) 1,3-benzene-
dicarboxylate; DHBDC ) 2,5-dihydroxybenzenedicarboxylate; TDC ) 2,5-
thiophenedicarboxylate; BTC ) 1,3,5-benzenetricarboxylate; ATC )
1,3,5,7-adamantanetetracarboxylate; HPDC ) 2,7-tetrahydropyrenedicar-
boxylate; PDC ) 2,7-pyrenedicarboxylate. b DEF ) diethylformamide;
EtOH ) ethanol; DMF ) dimethylformamide; CHP ) 1-cyclohexyl-2-
pyrolidinone.
(15) Gregg, S. J.; Sing, K. S. W. Adsorption, Surface Area and Porosity, 2nd
ed.; Academic Press: London, U.K., 1982.
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Rod Packings and Metal−Organic Frameworks
A R T I C L E S
Figure 4. MOF-69A: ball-and-stick representation of SBU (a); SBU with Zn shown as polyhedra (b); and view of crystalline framework with inorganic
SBUs linked together via biphenyl rings of 4,4′-biphenyldicarboxylate (c) (DEF and H2O guest molecules have been omitted for clarity). All drawing
conditions are the same as in Figure 3, with Zn in blue.
of a big container. Triethylamine (0.4 mL) (TEA) was added to DMF
(5 mL) and then placed in a vial in the center of the big container. The
container was covered, and the TEA solution was allowed to diffuse
into the solutions containing Pb(NO3)2 and H2BDC. After 1 week,
colorless crystals were produced, collected, and washed with ethanol
and DMF mixed solution (90% ethanol, 10% DMF). The crystals
became opaque upon exposure to air. Anal. Calcd for C12H16O6Pb )
MOF-70: C, 31.10; H, 3.48; N, 0.00. Found: C, 27.60; H, 1.96; N,
0.38. FT-IR (KBr 4000-400 cm-1): 3407 (br), 3058 (w), 2937 (w),
1643 (m), 1525 (s), 1448 (m), 1400 (s), 1360 (s), 1176 (w), 1150 (m),
1131 (w), 1104 (w), 1051 (m), 1025 (sh), 997 (w), 900 (m), 867 (m),
834 (m), 814 (sh), 755 (sh), 708 (w), 688 (w), 558 (m), 511 (sh).
Cd3(1,3-BDC)4‚(Me2NH2)2: MOF-72. A solid mixture of 1,3-
benzenedicarboxylic acid (H2-1,3-BDC) (24 mg, 0.145 mmol) and Cd-
(NO3)2‚4H2O (22.20 mg, 0.072 mmol) was dissolved in DMF (1 mL).
The resulting solution was transferred into a Pyrex tube by pipet. To
the solution was added a CH3NH2/H2O/DMF solution (0.1 mL) prepared
by diluting 40% aqueous CH3NH2 (1 mL) with DMF (50 mL). The
tube was frozen in a N2(l) bath, evacuated (200 mTorr), flame-sealed,
and heated to 140 °C at a rate if 5 °C/min for 50 h and then cooled to
room temperature at a rate of 2 °C/min. Colorless rod-shaped crystals
of the product were formed, collected, washed with DMF (3 mL × 3),
and air-dried (24 mg, 31% based on H2-1,3-BDC). Anal. Calcd for
C36H32N2O16Cd3 ) MOF-72: C, 39.82; H, 2.97; N, 2.58. Found: C,
39.47; H, 2.94; N, 2.72. FT-IR (KBr 4000-400 cm-1): 3450 (br), 3068
(w), 2934 (w), 1659 (s), 1608 (s), 1561 (m), 1480 (w), 1445 (w), 1388
(s), 1162 (w), 1021 (w), 832 (w), 747 (m), 725 (m), 661 (w).
Co(1,4-BDC)(DMF): MOF-71. A solid mixture of Co(NO3)2‚6H2O
(40 mg, 0.137 mmol) and 1,4-benzenedicarboxylic acid (23 mg, 0.137
mmol) was dissolved in DMF (1 mL) and absolute EtOH (0.25 mL).
The resulting solution was transferred with a pipet into a Pyrex tube,
frozen in a N2(l) bath, evacuated (200 mTorr), and flame-sealed. The
sealed reaction tube was heated for 15 h in a 100 °C isotemp oven.
The tube, containing pink blocklike crystals and purple hexagonal
platelike crystals, was removed from the oven while hot. The mixture
of crystals was collected and washed with DMF (3 mL × 3). The two
crystalline phases were separated by density (CHBr3/CH2Cl2), and the
pink blocklike crystals (17 mg, 84% based on H2BDC) were character-
ized. Anal. Calcd for C11H11NO5Co ) MOF-71: C, 44.61; H, 3.74; N,
4.73. Found: C, 43.37; H, 3.45; N, 4.26. FT-IR (KBr 4000-400 cm-1):
3441 (br), 3072 (w), 2946 (w), 2814 (w), 1636 (m), 1586 (m), 1389
(s), 1118 (w), 1017 (w), 820 (w), 747 (m), 671 (w), 538 (w), 430 (w).
Mn3(BDC)3(DEF)2: MOF-73. A solid mixture of 1,4-benzenedi-
carboxylic acid (H2BDC) (17 mg, 0.102 mmol) and Mn(ClO4)2•6H2O
(108 mg, 0.298 mmol) was dissolved in DEF (2.0 mL). This solution
was decanted into a Pyrex tube which was then frozen in a N2(l) bath,
evacuated (200 mTorr), flame-sealed, and heated for 48 h in a 100 °C
isotemp oven. The tube, containing colorless rhombus-shaped block
crystals, was removed from the oven while hot. The crystals were
washed with DEF (3 mL × 3) and air-dried to yield pure product (7
mg, 21.4% based on H2BDC). Anal. Calcd for C34H34NO14Mn3 ) MOF-
73: C, 47.52; H, 3.99; N, 3.24. Found: C, 45.67; H, 3.76; N, 3.24.
FT-IR (KBr 4000-400 cm-1): 3440 (br), 3131 (w), 3091 (w), 3056
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A R T I C L E S
Rosi et al.
Figure 5. MOF-70: ball-and-stick representation of SBU (a); SBU with Pb shown as polyhedra (b); and view of crystalline framework with inorganic
SBUs linked together via the benzene ring of 1,4-benzenedicarboxylate (c) (EtOH guest molecules have been omitted for clarity). All drawing conditions
are the same as in Figure 3, with Pb in blue.
(w), 2976 (w), 2940 (w), 1652 (s), 1574 (m), 1509 (m), 1395 (s), 1265
(w), 1212 (w), 1124 (w), 1019 (w), 889 (w), 826 (m), 750 (s), 662
(w), 519 (m).
Tb(BTC)(H2O)1.5‚(DMF): MOF-76. To a solvothermal vessel were
added H3BTC (0.020 g, 0. 10 mmol), Tb(NO3)3‚5H2O (0.120 g, 0.28
mmol), DMF (4 mL), ethanol (4 mL), and H2O (3.2 mL), respectively.
The vessel was sealed and heated to 80 °C at a rate of 2 °C/min for 24
h and then cooled to room temperature at a rate of 1 °C/min. Needlelike
colorless crystals of the product were formed and collected by filtration
(35 mg, 78% yield based on H3BTC). The product is stable in air and
insoluble in water and common organic solvents such as ethanol,
acetonitrile, acetone, chloroform, and DMF. Anal. Calcd for C12H13-
NO8.5Tb ) MOF-76: C, 30.92; H, 2.81; N, 3.00. Found: C, 31.03; H,
2.74; N, 2.93. FT-IR (KBr, 4000-400 cm-1): 3434 (br), 2934 (w),
1670 (s), 1631 (s), 1618 (s), 1578 (m), 1545 (m), 1446 (s), 1387 (s),
1111 (w), 946 (w), 775 (m), 709 (m), 571 (w), 459 (w).
Zn2(DHBDC)(DMF)2‚(H2O)2: MOF-74. A solid mixture of 2,5-
dihydroxy-1,4-benzenedicarboxylic acid (H2-DHBDC) (0.019 g, 0.096
mmol) and zinc nitrate tetrahydrate, Zn(NO3)2‚4(H2O) (0.053 mg, 0.203
mmol), was dissolved in DMF (2.0 mL), 2-propanol (0.1 mL), and
water (0.1 mL) and placed in a Pyrex tube which was then frozen in a
N2(l) bath, evacuated (200 mTorr), flame-sealed, and heated to 105 °C
at a rate of 2.0 °C/min for 20 h and then cooled to room temperature
at a rate of 2.0 °C/min. Yellow needle crystals were produced which
were dried in air after washing with DMF and ethanol (26 mg, yield
51% based on H2-DHBDC). Anal. Calcd for C14H20N2O10Zn2 ) MOF-
74: C, 33.16; H, 3.98; N, 5.52. Found: C, 32.93; H, 3.59; N, 5.33.
FT-IR (KBr, 4000-400 cm-1): 3440 (br), 2931 (w), 2818 (w), 1662
(s), 1555 (s), 1459 (m), 1408 (s), 1367 (w), 1245 (m), 1204 (s), 1112
(w), 913 (w), 888 (m), 812 (s), 674 (w), 633 (w), 587 (w), 480 (w).
Zn2(ATC): MOF-77. To a solvothermal vessel were added ada-
mantane tetracarboxylic acid (H4ATC) (0.048 g, 0.15 mmol), Zn(NO3)2‚
6H2O (0.140 g, 0.47 mmol), and H2O (4 mL), respectively. The vessel
was sealed and heated to 185 °C at a rate of 5 °C/min for 40 h and
then cooled to room temperature at a rate of 2 °C/min. Tetragonal
colorless crystals of the product were formed and collected by filtration,
yielding 0.058 g (86% yield based on H4ATC). The product is stable
in air and insoluble in water and common organic solvents such as
ethanol, acetonitrile, acetone, chloroform, and DMF. Anal. Calcd for
C14H12O8Zn2 ) MOF-77: C, 38.30; H, 2.76. Found: C, 38.41; H, 2.82.
FT-IR (KBr, 4000-400 cm-1): 3441 (br), 2954 (w), 2869 (w), 1618
(s), 1532 (s), 1420 (s), 1210 (m), 723 (m), 591 (w), 486 (w).
Tb(TDC)(NO3)(DMF)2: MOF-75. A solid mixture of Tb(NO3)3‚
5H2O (109 mg, 0.251 mmol) and 2,5-thiophenedicarboxylic acid (H2-
TDC) (11.5 mg, 0.067 mmol) was dissolved in DMF (1 mL). 2-Propanol
(1.5 mL) was added to the DMF solution. The resulting solution was
transferred with a pipet into a Pyrex tube, frozen in a N2(l) bath,
evacuated (200 mTorr), and flame-sealed. The sealed reaction tube was
heated to 85 °C at a rate of 2 °C/min for 15 h and then cooled to room
temperature at a rate of 2 °C/min to yield colorless polyhedral crystals
(30.6 mg, 84% based on H2TDC). Anal. Calcd for C12H16N3O9STb )
MOF-75: C, 26.83; H, 3.00; N, 7.82. Found: C, 26.63; H, 2.87; N,
7.68. FT-IR (KBr 4000-400 cm-1): 3455 (br), 3099 (w), 2941 (w),
1692 (s), 1657 (s), 1617 (s), 1586 (s), 1525 (m), 1459 (m), 1372 (s),
1316 (m), 1112 (w), 1041 (w), 797 (w), 776 (m), 685 (m), 466 (w).
Co(HPDC)(H2O)(DMF)2: MOF-78. H2HPDC (0.018 g, 0.06
mmol) was dissolved in DMF (7.0 mL) and EtOH (2.0 mL). To
deprotonate the acid, 0.10 mL of a triethylamine/ethanol solution (5.0%
v/v) was added to the organic solution and sonicated (1 min). Co(NO3)2‚
6H2O (0.060 g, 0.21 mmol) was dissolved in water (1.0 mL), which
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Rod Packings and Metal−Organic Frameworks
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Figure 6. MOF-72: ball-and-stick representation of SBU (a); SBU with Cd shown as polyhedra (b); and view of crystalline framework with inorganic
SBUs linked together via the benzene ring of 1,3-benzenedicarboxylate (c) (Me2NH2 guest cations have been omitted for clarity). All drawing conditions are
the same as in Figure 3, with Cd in blue.
was poured into the mixed solution, and the whole solution was mixed
using a sonicator (1 min). The resulting clear pink solution was placed
in a solvothermal vessel which was sealed and heated to 85 °C for 24
h and cooled to room temperature at a rate of 1.0 °C/min. Rectangular
pink crystals were produced which were dried in air after washing with
DMF and acetone (0.024 g, 77% based on one acid). Anal. Calcd for
C24H28N2O7Co ) Co(HPDC)(H2O)(DMF)2: C, 55.93; H, 5.48; N, 5.43.
Found: C, 55.45; H, 5.54; N, 3.76. FT-IR (KBr, 4000-400 cm-1):
3434 (br), 2934 (w), 2888 (w), 2835 (w), 2079 (br), 1664 (s), 1578
(m), 1539 (s), 1466 (w), 1433 (w), 1394 (vs), 1354 (s), 1300 (w), 1242
(m), 1117 (m), 1058 (m), 1006 (w), 929 (m), 802 (m), 749 (s), 595
(br), 459 (w).
Cd2(HPDC)2(CHP)‚(H2O): MOF-79. H2HPDC (0.018 g, 0.061
mmol) and Cd(NO3)2‚4H2O (0.055 g, 0.18 mmol) were suspended in
water (2.0 mL), CH3OH (3.0 mL), and 1-cylcohexyl-2-pyrrolidinone
(CHP) (3.0 mL), and the resulting mixture was dispersed by sonication
(1 min). The heterogeneous mixture was placed in a solvothermal vessel
which was sealed and heated to 130 °C at a rate of 2.0 °C/min for 20
h and then cooled to room temperature at a rate of 2.0 °C/min.
Rectangular pale yellow crystals were produced which were dried in
air after washing with DMF and ethanol (0.026 g, yield 52% based
H2TPDC). Anal. Calcd for C46H43NO10Cd2 ) MOF-79: C, 55.55; H,
4.35; N, 1.41. Found: C, 55.62; H, 4.25; N, 1.43. FT-IR (KBr, 4000-
400 cm-1): 3408 (br), 2932 (m), 2857 (w), 2867 (w), 1634 (s), 1606
(w), 1586 (w), 1571 (w), 1503 (w), 1467 (w), 1427 (w), 1396 (vs),
1380 (vs), 1348 (vs), 1300 (w), 1241 (w), 1129 (w), 1034 (w), 907
(br), 819 (w), 795 (m), 775 (m), 764 (m), 696 (w), 577 (w), 549 (w).
Tb(PDC)1.5(H2O)2(DMF)‚(DMF): MOF-80. H2PDC (0.010 g,
0.034 mmol) and Tb(NO3)3‚5H2O (0.056 g, 0.129 mmol) were
suspended in water (2.0 mL), ethanol (4.0 mL), and DMF (4.0 mL),
and the resulting mixture was dispersed by sonication (1 min). The
heterogeneous mixture was placed in a solvothermal vessel which was
sealed and heated at a rate of 2.0 °C/min to 80 °C for 24 h and then
cooled to room temperature at a rate of 1.0 °C/min. Rectangular pale
yellow crystals were produced which were dried in air after washing
with DMF and ethanol (0.013 g, 73% based on one acid). Anal. Calcd
for C33H30N2O10Tb ) MOF-80: C, 51.24; H, 3.91; N, 3.62. Found:
C, 51.13; H, 3.78; N, 3.21. FT-IR (KBr, 4000-400 cm-1): 3480 (br),
3059 (w), 2934 (w), 1670 (s), 1651 (w), 1617 (w), 1600 (m), 1563 (s),
1558 (s), 1460 (s), 1400 (vs), 1314 (w), 1262 (s), 1111 (m), 1065 (w),
913 (s), 820 (s), 782 (m), 736 (s), 709 (m), 676 (w), 599 (br).
Porosity Measurements. Mn3(BDC)3(DEF)2: MOF-73. A sample
of MOF-73 (15.153 mg) was heated under a N2 atmosphere from 25
to 600 °C at a rate of 1 °C/min in a gravimetric analyzer. A 22.9%
weight loss was observed from 115 to 350 °C, which corresponds to
the loss of one DEF molecule per formula unit (calcd: 23.5%). The
sample begins decomposing at 400 °C. Sorption isotherms for MOF-
73 were completed for both N2 and CHCl3 by measuring the increase
in weight at equilibrium as a function of relative pressures of the sorbate.
The sample was subjected to heating (275 °C/15 h) at pressures below
1 × 10-5 Torr to remove the guests and produce the evacuated form.
The sorption isotherms for N2 and CHCl3 are discussed in the Results
and Discussion section. The apparent surface area and the pore volume
were estimated to be 181 m2/g and 0.061 cm3/g, respectively.
Zn2(DHBDC)(DMF)2‚(H2O)2: MOF-74. The as-synthesized crys-
tals (100 mg) were placed in 10 mL of water in a 20 mL vial for 30
min. The water was decanted, and an additional 10 mL of water was
added to the vial, which was then allowed to stand at room temperature
for 1 h. The water was decanted again, and the crystals were washed
with ethanol (5 × 10 mL). The crystals were finally dried in air. The
elemental microanalysis data indicated that there was essentially no
DMF in the sample with the nitrogen content less than 0.1% (Anal.
Calcd for C11H16N0O10Zn2 ) Zn2(DHBDC)(H2O)2‚(H2O)0.5(C2H5-
OH)1.5: C, 30.09; H, 3.67; N, 0.00. Found: C, 30.03; H, 4.01; N,
<0.10). FT-IR data also showed the absence of the carbonyl peak of
DMF (1662 cm-1), which was strongly observed in the as-synthesized
samples. On the other hand, the νOH peak became more intense.
However, the observed XRPD showed the same peak pattern as those
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A R T I C L E S
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Figure 7. MOF-73: ball-and-stick representation of SBU (a); SBU with Mn shown as polyhedra (b); and view of crystalline framework with inorganic
SBUs linked together via the benzene ring of 1,4-benzenedicarboxylate (c) (DEF guest molecules have been omitted for clarity). All drawing conditions are
the same as in Figure 3, with Mn in blue.
of the as-synthesized material, which indicates the maintenance of the
original frameworks. FT-IR (KBr, 4000-400 cm-1): 3409 (br), 2981
(w), 1555 (s), 1459 (m), 1408 (s), 1245 (m), 1200 (s), 1122 (w), 1087
(w), 1046 (w), 888 (m), 816 (s), 582 (w).
Results and Discussion
Metal-Organic Frameworks with Packing of [Mx(CO2)y]∞
Rods.
In this section, we present the structures of MOF-69-80 in
the context of their underlying rod packing and their nets. All
of the structures are 3-D periodic frameworks and all of the
rods are composed of M-O-C units in which the carboxylate
links are coordinated to the metal centers in at least one of the
following modes:
TGA was performed on a sample of this material (14.588 mg). When
heated from 20 to 600 °C at 2.0 °C/min, two separate weight-loss steps
were observed: (a) 21.0% near 100 °C is attributed to the removal of
1.5 ethanol and 0.5 H2O molecules per formula unit (calcd. 17.8%),
and (b) 8.1% between 125 and 300 °C due to the removal of two
coordinated H2O (calcd. 8.2%). The sample does not show additional
weight loss up to 400 °C.
The water-exchanged sample (65.95 mg) was loaded in the sorption
apparatus, evacuated to 10-4 Torr, and heated to 220 °C for 16 h.
Weight loss behavior similar to that observed by TGA was observed,
and the final weight converged to 48.94 mg. Nitrogen sorption was
performed at 78 K, which resulted in reversible nitrogen uptake and
release with a Type I isotherm behavior (see Results and Discussion
section). The Langmuir surface area was estimated to be 245 m2/g.
Parallel Packing of Ladder-like Rods: MOF-69A-C. A
preliminary account of the synthesis and structure of MOF-69A
and B has already appeared;3 however, we briefly discuss these
compounds here, along with MOF-69C, to highlight their
relevance to the principles of using rods as building units. The
MOF-69A-C compounds have the same underlying topology
(isoreticular) as shown in Figure 4. They differ in the nature of
the organic link (BPDC for MOF-69A, NDC for MOF-69B,
and BDC for MOF-69C) joining the Zn-O-C units. Within
these units, there are tetrahedral and octahedral Zn(II) centers,
respectively, bound to 4 and 2 carboxylate groups (Figure 4a,b).
These groups are coordinated to the Zn by mode A with a µ-3
After the sorption experiment, the sample was heated to 320 °C under
vacuum, and the temperature was maintained for 2 h before cooling to
room temperature. The XRPD spectrum of the sample showed the same
pattern as both the as-synthesized and the water-treated materials.
Tb(BTC)(H2O)1.5‚(DMF): MOF-76. MOF-76 (54.90 mg) was
evacuated at room temperature for 36 h, and the weight was found to
be 54.60 mg. Upon heating this sample to 120 °C for 9 h, a weight
loss of 15.85% was observed, corresponding to the loss of one DMF
molecule per formula unit. N2 and Ar sorption isotherms are fully
reversible and of Type I behavior, characteristic of microporous
materials. A similar reversible uptake behavior for organic solvents
such as methylene chloride, benzene, and cyclohexane was observed.
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A R T I C L E S
Figure 8. MOF-75: ball-and-stick representation of SBU (a); SBU with Tb shown as polyhedra (b); and view of crystalline framework with inorganic
-
SBUs linked together via the thiophene ring of 2,5-thiophenedicarboxylate (c) (DMF guest molecules and NO3 ions have been omitted for clarity). All
drawing conditions are the same as in Figure 3, with Tb in blue.
hydroxide ion bridging three Zn centers. The infinite Zn-O-C
rods are stacked in parallel and connected in the [110] directions
by the respective organic links to give 1-D rhombic channels
of 12.2 Å along an edge and 16.6 Å along the diagonal (MOF-
69A) into which four DEF and two water molecules per formula
unit reside as guests (for MOF-69A and B; two DEF molecules
in MOF-69C) (Figure 4c). For MOF-69A-C, two DEF mol-
ecules were found hydrogen bonded to the µ-3 hydroxyl groups
(O‚‚‚H‚‚‚OC ) 2.81 Å for MOF-69A), while the remaining 2
DEF and 2 water guests are disordered in the pores (MOF69A
and B only).
Connecting the carboxylate C atoms gives a tetrahedral net that
is again that of sra (Figure 2).
MOF-71. The structure of the Co-O-C rods are composed
of 6-coordinated Co(II) centers having four bridging carboxyl
groups using mode A in addition to a doubly bridging oxygen
bound DMF ligand. This connectivity pattern is repeated
infinitely in the b direction, generating linear Co-O-C rods
that are zigzag ladders of corner-linked CoO6 octahedra. Each
rod is linked to four neighboring rods by the benzene ring of
the BDC units, generating 13.4 × 4.3 Å2 channels in the b
direction. The structure is identical to that of MIL-47 and is
illustrated in Figure 3a-c; the net of the structure is sra (Figure
2).
MOF-72. This structure is constructed from Cd-O-C rods
composed of a series of alternating six-coordinated Cd(II)
centers (Figure 6). The first is coordinated to six different
carboxyl groups in mode A. The second is coordinated to five
different carboxyl groups: three in mode A, one in mode B,
and one in mode B′. This leads to infinite Cd-O-C rods that
run along [10-1]. The rods consist of pairs of edge-sharing CdO6
polyhedra alternating with isolated CdO6 polyhedra and are
connected to six neighboring rods by the benzene rings of the
1,3-BDC links, resulting in parallel packing of hex type (Figure
1 and Table 1). This arrangement leaves open space in the
framework for dimethylammonium guests.
To derive the net of this structure, it is instructive to connect
all carboxylate C atoms in the same way as shown in Figure
3c. This gives a tetrahedral net with the C atoms at the vertices.
The Zn-O-C rods are ladders, to which the organic links
represent the lines that connect the rods together to give the
sra net topology (Figure 2).
MOF-70. The Pb-O-C rods in this structure are constructed
from 8-coordinated Pb(II) centers, where each is bonded to
carboxyl groups of four BDC linkers (Figure 5). All carboxyl
groups bind in modes B and B′. This connectivity pattern is
repeated infinitely to create Pb-O-C rods along the a direction
and to give edge shared PbO8 bisdisphenoids. The rods are
linked by the benzene rings of BDC, which connect each rod
to four neighboring rods in the c and b directions, generating
13.1 × 5.4 Å2 1-D rhombic channels in the a direction.
MOF-73. The Mn-O-C rods in this compound are con-
structed from a pair of linked 6-coordinated Mn(II) centers
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A R T I C L E S
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Figure 9. MOF-79: ball-and-stick representation of SBU (a); SBU with Cd shown as polyhedra (b); and view of crystalline framework with inorganic
SBUs linked together via the tetrahydropyrene ring of tetrahydropyrenedicarboxylate (c) (CHP guest molecules have been omitted for clarity). All drawing
conditions are the same as in Figure 3, with Cd in blue.
(Figure 7). Here, one of the Mn centers has four carboxyl group
with two of these bound as in mode A, and one as in mode B,
while the remaining one as mode B′. A terminal DEF ligand is
also bound to each of these Mn centers. The adjacent Mn center
has six carboxyl groups with four bound as in mode A, and
two as in mode B′. Each rod is corner-linked and edge-linked
MnO6 polyhedra. The benzene units of the BDC units connect
each rod to four neighboring rods, resulting in a pcu (Table 1,
Figure 1) arrangement with rhombic channels having 11.2 ×
5.9 Å2 dimensions in which DEF molecules reside as coordi-
nated guests.
other rods of this paper. The HPDC link each rod in the a and
b directions to four neighboring rods, resulting in rhombic
channels measuring 23.8 × 6.7 Å2 running along the c direction.
The structure can be simplified by connecting the carboxylate
carbon atoms to give a tetrahedral net with the carboxylate
carbon atoms at the vertices in the same way as for MOF-71
(cf., Figure 3), thus resulting in the same net (sra).
MOF-79. The Cd-O-C rods are built from 6- and 7-coor-
dinated Cd(II) centers and are rather more complex than the
other rods described here (Figure 9). Four carboxyl groups and
a terminal CHP ligand are bound to the first with two carboxyl
groups coordinating as in mode B, one as in A′′, and the
remaining one as in B′. The other metal center is coordinated
by five carboxyl groups with two as in B′, one as A′, one as
A′′, and the remaining one as in B. These rods are linked by
the HPDC link to four other rods to give pcu type rod packing
(Table 1, Figure 1).
MOF-80. The rods here are composed of chains of 8-coor-
dinated Tb(III) forming square antiprisms (Figure 10). Each Tb
is bound by five carboxyl groups, one terminal DMF, and two
terminal water ligands. Four of the carboxyl groups are bound
according to mode A, and one is bound according to mode C.
The rods are linked together along the [011] plane by the PDC
connectors to give rod packing of pcu type (Table 1, Figure 1)
and channels of 19.3 × 5.8 Å2 channels running in the c
direction.
Helical Rods: MOF-74. This structure (Figure 11) is based
on coordinated carboxyl and hydroxy groups. Helical Zn-O-C
rods of composition [O2Zn2](CO2)2 are constructed from
6-coordinated Zn(II) centers, where each Zn has three carboxyl
MOF-75. In this structure, Tb-O-C rods are composed of
8-coordinated Tb(III) that are bound by four carboxyl groups,
one bidentate nitrate ligand, and two DEF terminal ligands
(Figure 8). The carboxyl groups are all coordinated according
to mode A. This connectivity pattern is repeated infinitely to
produce Tb-O-C rods in the a crystallographic direction. The
rods are linked TbO8 bisdisphenoids with the carboxyl carbon
atoms forming a twisted ladder that are linked in the b and c
directions by the thiophene units of the TDC links, generating
pcu type rod packing (Table 1, Figure 1) and rhombic channels
in the a direction measuring 9.7 × 6.7 Å2. The net of the
structure is irl, the simplest net for linking twisted ladders
(Figure 2).
MOF-78. In this structure, the Co-O-C rods are built from
6-coordinated Co(II) centers, to each of which two carboxyl
groups, two terminal DMF ligands, and two doubly bridging
water ligands are bound. The carboxyl groups are bound in a
monodentate fashion according to mode C so they do not fit
into our scheme of counting O atoms in the same way as the
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Rod Packings and Metal−Organic Frameworks
A R T I C L E S
Figure 10. MOF-80: ball-and-stick representation of SBU (a); SBU with Tb shown as polyhedra (b); and view of crystalline framework with inorganic
SBUs linked together via the pyrene ring of pyrenedicarboxylate (c) (DMF guest molecules have been omitted for clarity). All drawing conditions are the
same as in Figure 3, with Tb in blue.
Figure 11. MOF-74: ball-and-stick representation of SBU (a); SBU with Zn shown as polyhedra (b); and view of crystalline framework with inorganic
SBUs linked together via the benzene ring of 2,5-dihydroxybenzene-1,4-dicarboxylate (c) (DMF and H2O guest molecules have been omitted for clarity).
All drawing conditions are the same as in Figure 3, with Zn in blue.
groups: one bound as in mode A and the remaining two as in
A′. In addition, two hydroxy groups are bound as doubly
bridging. The remaining coordination site has a terminal DMF
ligand. The rods consist of edge-sharing ZnO6 octahedra
alternately opposite and next-neighbor to form either a 31 or a
32 helix. The rods are linked by the benzene units of the DHBDC
to produce bnn parallel rod packing (Table 1, Figure 1) and
one-dimensional channels of dimensions 10.3 × 5.5 Å2 in which
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A R T I C L E S
Rosi et al.
Figure 12. MOF-76: ball-and-stick representation of SBU (a); SBU with Tb shown as polyhedra (b); and view of crystalline framework with inorganic
SBUs linked together via the benzene ring of 1,3,5-benzenetricarboxylate (c) (DMF and H2O guest molecules have been omitted for clarity). All drawing
conditions are the same as in Figure 3, with Tb in blue.
terminal DMF molecules protrude and water guests reside.
Considering just the carboxylate C atoms as points of extension,
they form 31 and 32 helices that are linked as in net etb (Figure
2).
SBUs of MOFs can generally be formulated [O0 O1-bO2-
a c
Mn+d] (RCO2-)e. Here, O0 refers to O fully bonded as in H2O
and O1- refers to species such as OH-. The condition for
neutrality is b + 2c + e ) nd. A key parameter is the O/M
ratio r ) (a + b + c + 2e)/d because it is primarily what
controls the dimensionality of the SBU. For example, in an
octahedral SBU [M3+](RCO2-)3, we have a neutral unit with r
) 6. For octahedral coordination, this must correspond to an
isolated (finite) unit. For an infinite SBU consisting of condensed
MO6 octahedra (corner, edge, or face sharing), r must be e5.
MOF-76. The Tb-O-C units are constructed from 7-coor-
dinated Tb(III) centers (Figure 12). Six carboxyl groups as in
mode A and a terminal water ligand bind each Tb. Each rod is
connected to four neighboring rods through the benzene ring
of the BTC link. The rods pack in a tetragonal fashion, resulting
in 6.6 × 6.6 Å2 square channels in the c direction, which are
filled with DMF molecules. Note, however, that the rods them-
selves are on 41 helices, but, because of the tritopic nature of
the organic SBU, result in a rather complicated overall topology.
Tetragonal Layer Rod Packing: MOF-77. In this structure
(Figure 13), Zn-O-C rods are composed of tetrahedral Zn(II)
centers. Four carboxyl groups that are bound in mode A bind
each Zn. This connectivity pattern results in infinite Zn-O-C
rods, which are cross-linked by the tetrahedral ATC link to give
an arrangement where the rods propagate along a and b,
resulting in a tetragonal layer packing of rods of the ths-z type
(Table 1, Figure 1). It is worth noting that the carboxylate C
atoms lie on a rod of opposite-edge-sharing tetrahedra (SiS2
rod).
We can reduce r to 5 by either (a) replacing RCO2 by OH-
-
making a basic salt as in MIL-53 described above,10 or (b) by
replacing RCO2- + M3+ by O2- + M4+ again making a basic
salt (MIL-47),8 or (c) by replacing RCO2 + M3+ by O0 +
-
M
2+ using a neutral species to complete the coordination shell
as in MOF-71.
For the MOF-5 SBU OZn4(RCO2)6, a ) b ) 0, c ) 1, d )
4, e ) 6, and n ) 2.1a The parameter r ) 13/4 (3.25). If the Zn
atoms are in tetrahedral coordination, then for an infinite SBU
consisting of ZnO4 condensed (corner, edge, or face sharing)
tetrahedra r must be e3. Accordingly, to convert from this finite
SBU to an infinite SBU with tetrahedra coordination, one must
again decrease the value of r. This can be accomplished by
-
-
Strategies for the Logical Synthesis of Rod SBUs. Here,
we discuss some points that should be considered when
attempting to produce structures with rod SBUs. The M-O-C
replacing one RCO2 by O- (e.g., OH-) or 2 RCO2 by O2-
,
that is, by making a more basic salt. However, when this is
attempted by adding small amounts of base and water to
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Rod Packings and Metal−Organic Frameworks
A R T I C L E S
Figure 13. MOF-77: ball-and-stick representation of SBU (a); SBU with Zn shown as polyhedra (b); view of crystalline framework with inorganic SBUs
linked together via tetrahedron of adamantanetetracarboxylate (c). All drawing conditions are the same as in Figure 3, with Zn in blue.
reactions known to produce the MOF-5 SBU, we obtain the
infinite SBU found in MOF-69 with mixed octahedral and
tetrahedral coordination.3 This new SBU can formally be derived
from that of MOF-5 by the following process:
3OZn4(RCO2)6 + 2OH- + 3H2O f
-
4(OH)2Zn3(RCO2)4 + 2RCO2
Here, r has increased from 13/4 (3.25) to 10/3 (3.33) as a
consequence of the higher average coordination number of Zn2+
(i.e., 4 ZnO4 in MOF-5 to 2 ZnO4 and 1 ZnO6 in MOF-69).
These conditions will not produce an infinite condensed SBU
with only tetrahedral Zn, but it turns out that 1/3 of the Zn atoms
are in octahedral coordination and part of an infinite SBU.
Indeed, this indicates that infinite SBUs will be favored for
higher coordination (see, e.g., MOF-70).
It is worth mentioning that we do not claim at this stage to
Figure 14. Gas sorption isotherms for MOF-73, MOF-74, and MOF-76.
For the nitrogen isotherms, the open circles represent desorption.
be able to design the M-O-C SBU a priori; instead, we are
claiming that we can identify variables and strategies for
producing a particular kind of SBU. Once we know the
conditions under which a given SBU can be prepared, we can
then combine it with a variety of organic linkers to produce a
wide range of structures as we have done for literally dozens
of compounds with, for example, the copper paddle-wheel16 and
the basic zinc acetate SBU.1a-c,17 The isoreticular series of MOF-
69A, MOF-69B, and MOF-69C reported here is another
example of a successful implementation of this strategy applied
now to an infinite SBU.
Porosity and Architectural Stability of 3-D Rod-Contain-
ing Frameworks. To determine whether the MOFs constructed
from rod SBUs can maintain their structural integrity in the
absence of guests, we examined the gas sorption behavior of
the most open members of this series: MOF-73, -74, and -76.
These materials were evacuated by either heating to remove
terminal DEF ligands pointing into the pores (MOF-73) and
DMF guests (MOF-76), or exchanging terminal DMF ligands
with water and ethanol, followed by heating to remove the
ethanol and the water guests (MOF-74). In all three cases, the
(16) For a systematic account of linking Cu carboxylate paddle wheels, see:
(a) Eddaoudi, M.; Kim, J.; Vodak, D.; Sudik, A.; Wachter, J.; O’Keeffe,
M.; Yaghi, O. M. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 4900-4904.
Other MOF examples are: (b) Chui, S. S.-Y.; Lo, S. M.-F.; Charmant, J.
P. H.; Orpen, A. G.; Williams, I. D. Science 1999, 283, 1148-1150. (c)
Chen, B.; Eddadoudi, M.; Reineke, T. M.; Kampf, J. W.; O’Keeffe, M.;
Yaghi, O. M. J. Am. Chem. Soc. 2000, 122, 11559-11560. (d) Chen, B.;
Eddaoudi, M.; Hyde, S. T.; O’Keeffe, M.; Yaghi, O. M. Science 2001,
292, 1021-1023.
(17) Chae, H. K.; Kim, J.; Delgado-Friedrichs, O.; O’Keeffe, M.; Yaghi, O.
M.. Angew. Chem., Int. Ed. 2003, 42, 3907-3909.
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A R T I C L E S
Rosi et al.
Table 3. Sorption and Molecular Sieving Data for MOF-76a
sponding radii of the adsorbates (cyclohexane, 6.20 Å; meth-
ylene chloride, 4.00 Å; and benzene, 5.85 Å).
amount
sorbed
(mg/g)
pore
Langmuir
surface area
(m2/g)
evacuation
volume
(cm3/g)
temperature (
°
C)
sorbate
Summary and Conclusions
120
120
200
200
200
200
N2
Ar
N2
CH2Cl2
C6H6
C6H12
76.01
126.9
98.00
243.59
144.85
95.1
0.094
0.094
0.121
0.184
0.165
0.130
264
334
This contribution outlined the principles for constructing
structures from rodlike building blocks and identified the most
likely nets that should result from the combination of metal-
carboxylate rods with organic linkers. We demonstrated the
success of this approach by linking rods with organic units to
produce 14 new MOF structures with rigid and porous archi-
tectures that are based on four different rod packing nets. It
was shown that most MOF structures are based on parallel rod
packings; however, the rod and link metrics required to make
new MOFs adopting more complex rod packing have also been
presented. They point toward a strategy for preparing structures
based on 3- and 4-way rod packings; such structures are
expected to have greatly enhanced stability due to the three-
dimensional nature of the packing. Finally, we recall this is the
first extensive effort to prepare such structures, and as experience
is gained with controlling the formation of rods of certain types,
attention can be directed toward controlling the type of rod
packing.
a Sieving is with organic solvents after activation at 200 °C.
evacuated materials reversibly sorb N2(g) and all isotherms are
of Type I class (Figure 14), indicative of permanent microporos-
ity and architectural stability of their evacuated frameworks.
Similar behavior was observed for Ar(g) uptake into MOF-76
and organic vapors into MOF-73 and MOF-76.
Molecular Sieving by MOF-76. It is worth noting that
because the pores in MOF-76 are one-dimensional and sorption
at low temperature is mostly controlled by diffusion, the N2
(kinetic diameter: 3.65 Å) and argon (3.4 Å) sorption reveals
a lower sorption uptake as compared to a favored sorption of
CH2Cl2 at room temperature. Similar findings were documented
for zeolite sorption studies and are attributed to possible
obstruction within the channels that are amplified at lower
temperatures.18 In this case, the sorption is sensitive to the
applied activation temperature of evacuation because an uptake
increase was observed upon activation at 200 °C as compared
to the prior activation at 120 °C. The evacuated TbBTC
framework showed molecular sieving, and the data are sum-
marized in Table 3. These data are in agreement with the
expected trend based on radii of adsorbate, given the corre-
Acknowledgment. We thank Mr. Adam Goldberg for as-
sistance in the preliminary synthesis and characterization of
some compounds. We thank the NSF (DMR 0242630, O.M.Y.
and DMR 0103036, M.O’K.) and DOE (O.M.Y.) for funding.
Supporting Information Available: Data collection, structure
solutions, refinement parameters, and ORTEP diagrams for
MOF-69-80 and CIF files for MOF-69-80. This material is
available free of charge via the Internet at http://pubs.acs.org.
(18) Breck, D. W. Zeolite Molecular SieVes; John Wiley & Sons: New York,
1974.
JA045123O
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1518 J. AM. CHEM. SOC. VOL. 127, NO. 5, 2005