Structural, magnetic, and gas adsorption study of a series of partially fluorinated metal-organic frameworks (H F -MOFs)

Article abstract of DOI:10.1021/ic1017246

Four new partially fluorinated metal organic frameworks (HF-MOFs) have been synthesized under different solvothermal conditions (H₂O or dimethylformamide (DMF)) from transition metal cations [Co²⁺ and Mn²⁺], 3-methyl pyridine (3-mepy) and 4,4′- (hexafluoroisopropylidene) bis(benzoic acid) (C₁₇H₁₀F ₆O₄, H₂hfbba), to determine the influence of reaction conditions on the formation of MOFs. This family of materials displays a striking degree of structural similarity depending on the solvent of synthesis. HF-MOFs synthesized from H₂O [Co-HFMOF-W, Co(hfbba)(3-mepy)(H₂O) and Mn-HFMOF-W, Mn(hfbba)(3-mepy)(H ₂O)] contain three-dimensional connectivity whereas HF-MOFs synthesized from DMF Co-HFMOF-D, [Co₂(hfbba)₂(3-mepy) ₂].(DMF)₃ and Mn-HFMOF-D, [Mn₂(hfbba) ₂(3-mepy)]·(H₂O) are two-dimensional in nature. Co-HFMOF-W and Mn-HFMOF-W are iso-structural polymeric materials. Thermal gravimetric analysis performed on as-synthesized HF-MOFs revealed that these compounds have high thermal stability (～350 °C). The continuous decrease of the χT product with decreasing T for Co-HFMOF-D and Co-HFMOF-W respectively indicates the presence of antiferromagnetic exchange interaction between two Co²⁺ (S = 3/2) metal centers within a cluster.

Full text of DOI:10.1021/ic1017246

ARTICLE
pubs.acs.org/IC
Structural, Magnetic, and Gas Adsorption Study of a Series of Partially
Fluorinated MetalꢀOrganic Frameworks (HF-MOFs)
Pradip Pachfule, Raja Das, Pankaj Poddar, and Rahul Banerjee*
Physical/Materials Chemistry Division, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune, 411008, India
S Supporting Information
b
ABSTRACT: Four new partially fluorinated metal organic frame-
works (HF-MOFs) have been synthesized under different sol-
vothermal conditions (H2O or dimethylformamide (DMF)) from
transition metal cations [Co2þ and Mn2þ], 3-methyl pyridine
(3-mepy) and 4,40-(hexafluoroisopropylidene) bis(benzoic acid)
(C17H10F6O4, H2hfbba), to determine the influence of reaction
conditions on the formation of MOFs. This family of materials
displays a striking degree of structural similarity depending on the
solvent of synthesis. HF-MOFs synthesized from H2O [Co-
HFMOF-W, Co(hfbba)(3-mepy)(H2O) and Mn-HFMOF-W, Mn(hfbba)(3-mepy)(H2O)] contain three-dimensional connectivity
whereas HF-MOFs synthesized from DMF Co-HFMOF-D, [Co2(hfbba)2(3-mepy)2] (DMF)3 and Mn-HFMOF-D, [Mn2(hfbba)2(3-
3
mepy)] (H2O) are two-dimensional in nature. Co-HFMOF-W and Mn-HFMOF-W are iso-structural polymeric materials. Thermal
3
gravimetric analysis performed on as-synthesized HF-MOFs revealed that these compounds have high thermal stability (∼350 °C). The
continuous decrease of the χT product with decreasing T for Co-HFMOF-D and Co-HFMOF-W respectively indicates the presence of
antiferromagnetic exchange interaction between two Co2þ (S = 3/2) metal centers within a cluster.
’ INTRODUCTION
these coligands, results in the precipitation of unreacted starting
materials. It is noteworthy that MOF synthesis, in general, occurs
in solvothermal media (water, organic solvents, ionic liquids), yet
none of the synthetic details described in the literature explains
the cause behind the solvent choice, despite it being an important
parameter in the phase-pure synthesis of a desired phase.13 As a
result, it is still a challenge to predict the resulting structure of a
MOF beforehand as its formation not only is influenced by the
geometrical and electronic factors of metal ions and the organic
links but also is dependent on other factors such as the rigidity or
flexibility of the ligands, choice of solvent and solvent polarity,
temperature, metal/ligand ratio, and pH.14
As a part of our ongoing investigation on the synthesis of
different HF-MOFs, we studied the hydrothermal chemistry of
4,40-(hexafluoroisopropylidene) bis(benzoic acid) (H2hfbba) as
a fluorinated ligand by incorporating it into the hybrid materials
along with coligand 3-methyl pyridine (3-picoline) and Co2þ or
Mn2þ as metal center.15 To study the effect of solvent variation
on the resulting HF-MOF framework, we used either DMF or
H2O as solvent of synthesis. These HF-MOFs formulated as
Metalꢀorganic frameworks (MOFs)1 represent a new class of
network solids that have great potential in specific applications
like separation,2 storage,3 heterogeneous catalysis,4 and con-
trolled drug delivery.5 Extensive research has been done on
MOFs as these materials are good for storing hydrogen6 and
carbon dioxide.7 The hydrogen and carbon dioxide storage
capacity in MOFs can be enhanced in various ways, such as
introducing open metal sites, increasing surface area and pore
volume, functionalizing organic linkers, and utilizing catenation.8
Yang et al.,9 in this regard, have explored for the first time the
possibility of synthesizing Fluorinated Metal Organic Frame-
works (FMOFs) using perfluorinated polycarboxylate ligands
with porous surfaces and exposed fluorine atoms for interesting
H2 storage properties. They have reported hysteretic 2-step, and
one of the highest volumetric capacities for H2 adsorption which
later has been independently reviewed by Fischer and W€oll.10
Later, Cheetham and co-workers11a,b and others11cꢀf also ex-
plored the interesting H2 and CO2 storage properties in partially
fluorinated MOFs or mixed perfluorinated and nonfluorinated
ligands. In all these reports researchers have agreed that MOFs
with fluoro-lined or fluoro-coated channels are expected to
possess enhanced affinity and selectivity toward gas adsorption
compared to their nonfluorous counterparts.
[Co2(hfbba)2(3-mepy)2] (DMF)3 (Co-HFMOF-D), [Co(hfb-
3
ba)(3-mepy)(H2O)] (Co-HFMOF-W), [Mn2(hfbba)2(3-me-
py)] (H2O) (Mn-HFMOF-D), [Mn(hfbba)(3-mepy)(H2O)]
3
(Mn-HFMOF-W) display interesting two-dimensional (2-D, in
DMF) and three-dimensional (3-D, in H2O) structural features
based on the solvent of synthesis (Scheme 1). Structures of these
Recently, we have synthesized several HF-MOFs with partially
fluorinated dicarboxylic acids and transition metals in the pre-
sence of nitrogen containing coligands.12 In the reaction of these
fluorinated dicarboxylates, insertion of a coligand is required as
often reaction of metal with these perfluorinated ligands, without
Received: August 25, 2010
Published: March 25, 2011
r
2011 American Chemical Society
3855
dx.doi.org/10.1021/ic1017246 Inorg. Chem. 2011, 50, 3855–3865
|

Inorganic Chemistry
ARTICLE
Scheme 1. Synthetic Details of All the HF-MOFs Reported in This Paper
HF-MOFs have been determined by X-ray crystallography and
further identified by IR spectroscopy, powder X-ray diffraction
(PXRD), and thermogravimetric analysis (TGA). These HF-
MOFs also show interesting H2 and CO2 uptake and magnetic
properties based on their structural variation.
H2hfbba stock solution (0.20 M) were mixed in a 5 mL vial. To this
solution was added 0.5 mL of Mn(NO3)2 xH2O stock solution (0.20 M).
3
The vial was capped and heated to 85 °C for 96 h. The mother liquor was
decanted, and the products were washed with DMF (15 mL) three times.
Colorless crystals of Mn-HFMOF-D were collected by filtration and dried
in air (10 min). [Yield: 47%, 0.0134 g depending on Mn(NO3)2 xH2O].
3
FT-IR: (KBr 4000ꢀ450 cmꢀ1): 3225(m, br), 1965(m), 1624(m),
’ EXPERIMENTAL SECTION
1550(s), 1390(s), 1242(s), 1171(m), 957(s), 784(s), 555 (w) cmꢀ1
Synthesis of [Mn(hfbba)(3-mepy)(H2O)] (Mn-HFMOF-W).
.
General Procedures. All reagents and solvents for synthesis and
analysis were commercially available and used as received. The Fourier
transform (FT) IR spectra (KBr pellet) were taken on a Perkin Elmer
FT-IR Spectrum (Nicolet) spectrometer. PXRD patterns were recorded
on a Phillips PANalytical diffractometer for Cu KR1 radiation (λ =
1.5406 Å), with a scan speed of 2° minꢀ1 and a step size of 0.02° in 2θ.
TGA was carried out in the temperature range of 15ꢀ900 °C on a SDT
Q600 TG-DTA analyzer under N2 atmosphere at a heating rate of 10 °C
minꢀ1. All low pressure gas adsorption experiments (up to 1 bar) were
performed on a Quantachrome Quadrasorb automatic volumetric instru-
ment. Direct current (DC) magnetization versus T curves were taken at a
500 Oe field in field cooled (FC) and zero field cooled (ZFC) modes with
heating/cooling rate of 2 K per minute. Magnetizations versus field loops
were taken in a field sweep from ꢀ50 kOe to þ50 kOe at a rate of 75 Oe/sec.
All the measurements were done using a Physical Property Measurement
System (PPMS) from Quantum Design Inc., San Diego, U.S.A., equipped
with a 7 T superconducting magnet and a vibrating sample magnetometer.
The magnetic signal from the sample holder was negligible and did not affect
our data accuracy.
Hydrothermal reaction of Mn(NO3)2 xH2O (0.035, 0.12 mmol) with
3
0.5 mL of 3-methyl pyridine and excess H2hfbba (0.196 g, 0.50 mmol) in
a 25 mL acid-digestion bomb using deionized water (7 mL) at 85 °C for
96 h produced colorless crystals of Mn-HFMOF-D. Crystals were
collected by filtration, washed with ethanol, and dried in air (10 min).
[Yield: 61%, 0.0213 g depending on Mn(NO3)2 xH2O]. FT-IR: (KBr
3
4000ꢀ450 cmꢀ1): 3207 (m, br), 3090(w), 2528(w), 1697(m), 1610(s),
1547(m), 1390(s), 1292(m), 1248(s), 1171(m), 933(w), 785(m),
730(m), 514(w) cmꢀ1
.
X-ray Crystallography. All single crystal data were collected on a
Bruker SMART APEX three circle diffractometer equipped with a CCD
area detector (Bruker Systems Inc., 1999a)16 and operated at 1500 W
power (50 kV, 30 mA) to generate Mo KR radiation (λ = 0.71073 Å).
The incident X-ray beam was focused and monochromated using Bruker
Excalibur Gobel mirror optics. Crystals of the HF-MOFs reported in the
paper were mounted on nylon CryoLoops (Hampton Research) with
Paraton-N (Hampton Research). Data were integrated using Bruker
SAINT software.17 Data were subsequently corrected for absorption by
the program SADABS.18 The space group determinations and tests for
merohedral twinning were carried out using XPREP.19 In all cases, the
highest possible space group was chosen. All structures were solved by
direct methods and refined using the SHELXTL 97 software suite.20
Atoms were located from iterative examination of difference F-maps
following least-squares refinements of the earlier models. Hydrogen
atoms were placed in calculated positions and included as riding atoms
with isotropic displacement parameters 1.2ꢀ1.5 times Ueq of the attached C
atoms. Data were collected at 298(2) K for all the HF-MOFs reported in this
paper. All structures were examined using the Addsym subroutine of
PLATON21 to ensure that no additional symmetry could be applied to the
models. All ellipsoids in ORTEP diagrams are displayed at the 50% probability
level unless noted otherwise. The Supporting Information contains a detailed
data collection strategy and crystallographic data for the four HF-MOFs
reported in this paper. Crystal data and details of data collection,
structure solution, and refinement are summarized in Table 1. Crystal-
lographic data (excluding structure factors) for the structures reported in
this paper have been deposited with the CCDC as deposition Nos.
CCDC 788025ꢀ788028 (see also Table 1). Copies of the data can be
obtained, free of charge, on application to the CCDC, 12 Union Road,
Cambridge CB2 lEZ, U.K. (fax: þ 44 (1223) 336 033; e-mail: deposit@
ccdc.cam.ac.uk).
Synthesis of [Co2(hfbba)2(3-mepy)2] (DMF)3 (Co-HFMOF-D).
A 0.5 mL portion of 3-methyl pyridine stock solution and 1.5 mL of H2hfbba
stock solution (0.20 M) were mixed in a 5 mL vial. To this solution was
3
added 0.5 mL of Co(NO3)2 6H2O stock solution (0.20 M). The vial was
3
capped and heated to 85 °C for 96 h. The mother liquor was decanted, and
the products were washed with DMF (15 mL) three times. Dark pink
colored crystals of Co-HFMOF-D were collected by filtration and dried in air
(10 min) [Yield: 52%, 0.0151 g depending on Co(NO3)2 6H2O]. FT-IR:
3
(KBr 4000ꢀ450 cmꢀ1): 3393(m, br), 2935(w), 19441(w), 1628(m),
1406(s), 1172(s), 929(m), 780(m), 481(m) cmꢀ1
Synthesis of [Co(hfbba)(3-mepy)(H2O)] (Co-HFMOF-W).
.
Hydrothermal reaction of Co(NO3)2 6H2O (0.035, 0.12 mmol) with
3
0.5 mL of 3-methyl pyridine and excess H2hfbba (0.196 g, 0.50 mmol) in
a 25 mL acid-digestion bomb using deionized water (7 mL) at 85 °C for
96 h produced pink colored crystals of Co-HFMOF-W. Crystals were
collected by filtration, washed with ethanol, and dried in air (10 min).
[Yield: 42%, 0.0147 g depending on Co(NO3)2 6H2O]. FT-IR: (KBr
3
4000ꢀ450 cmꢀ1): 3203 (m, br), 3088(w), 2528(w), 1697(m), 1609(s),
1546(m), 1392(s), 1293(m), 1171(m), 930(w), 786(m), 725(m),
512(w) cmꢀ1
Synthesis of [Mn2(hfbba)2(3-mepy)] (H2O) (Mn-HFMOF-D).
.
3
A 0.5 mL portion of 3-methyl pyridine stock solution and 1.5 mL of
3856
dx.doi.org/10.1021/ic1017246 |Inorg. Chem. 2011, 50, 3855–3865

Inorganic Chemistry
ARTICLE
Table 1. Crystal Data and Structure Refinement for HF-MOFs Reported in This Paper
Co-HFMOF-D
Co-HFMOF-W
Mn-HFMOF-D
Mn-HFMOF-W
empirical formula
formula weight
crystal system
C
28H20F6N4O7 Co
C23H17F6NO5Co
560.31
C23H16F6NO4.5Mn
547.31
C23H17F6NO5Mn
556.32
696.65
monoclinic
C2/c
orthorhombic
Pna21
monoclinic
C2
orthorhombic
Pna21
space group
unit cell dimensions
a = 26.957(19) Å
b = 11.025(8) Å
c = 24.602(15) Å
β = 119.74(3)°
6349(7)
a = 26.194(13) Å
b = 10.524(5) Å
c = 8.243(4) Å
a = 28.086(8) Å
b = 7.583(2) Å
c = 12.109(3) Å
β = 105.461(5)°
2485.6(11)
2
a = 26.406(8) Å,
b = 10.626(3) Å,
c = 8.473(3) Å
volume
2272.4(19)
4
2377.3(13)
4
Z
8
density (calculated)
reflections collected
independent reflections
data/restraints/parameters
goodness-of-fit on F2
final R indices [I > 2σ(I)]
1.458
1.638
1.463
1.554
5402
5254
4365
4182
4980
4653
2991
3773
5402/16/331
1.054
5254/2/332
1.095
4365/4/320
1.010
4182/2/334
1.052
R1 = 0.1297
wR2 = 0.3308
R1 = 0.1343
wR2 = 0.3359
0.163 and ꢀ0.959 e Åꢀ3
R1 = 0.0550
wR2 = 0.1133
R1 = 0.0641
wR2 = 0.1168
0.088 and ꢀ0.998 e Åꢀ3
R1 = 0.0682
wR2 = 0.1675
R1 = 0.0959
wR2 = 0.1797
0.100 and ꢀ0.361e Åꢀ3
R1 = 0.0354
wR2 = 0.0913
R1 = 0.0405
wR2 = 0.0935
0.055 and ꢀ0.326 e Åꢀ3
R indices (all data)
largest diff. peak and hole
H2 and CO2 Adsorption Measurements. Hydrogen adsorp-
tionꢀdesorption experiments were conducted at 77 K using a Quanta-
chrome Quadrasorb automatic volumetric instrument. Ultrapure H2
(99.95%) was purified further by using calcium aluminosilicate adsor-
bents to remove trace amounts of water and other impurities before
introduction into the system. For measurements at 77 K, a standard low-
temperature liquid nitrogen dewar vessel was used. CO2 adsorptionꢀ
desorption measurements were done at room temperature (298 K).
Before gas adsorption measurements, the sample was activated at room
temperature (for 24 h) and 100 °C (for 36 h) under ultrahigh vacuum
(10ꢀ8 mbar) overnight. About 75 mg of samples were loaded for gas
adsorption, and the weight of each sample was recorded before and after
outgassing to confirm complete removal of all guest molecules including
the coordinated H2O in Co-HFMOF-W and Mn-HFMOF-W.
’ DESCRIPTION OF CRYSTAL STRUCTURES
Crystal Structure of [Co2(hfbba)2(3-mepy)2] (DMF)3 (Co-
3
HFMOF-D). Crystal structure of Co-HFMOF-D contains two
crystallographically independent Co2þ ions, two hfbba ligands,
two 3-methyl pyridine ligands, and three lattice DMF molecules
in its asymmetric unit (Figure 1a). Both Co2þ centers of Co-HF-
MOF-D have almost the same coordination environments with a
nearly ideal square-pyramidal sphere (τ ≈ 0)23 enclosed by four
hfbba ligands [CoꢀO distance ranges from 2.024(2) to 2.051(2) Å]
and one 3-methyl pyridine ligand [CoꢀN = 2.051(3) Å]. The
dicobalt paddlewheel SBU (secondary building unit)24 for Co-
HFMOF-D with the Co Co distance of 2.746(1)Å is shown in
3 3 3
Figure 1a, expanded to show the four hfbba ligands, each coordinated
to a dicobalt paddlewheel unit via one of their carboxylate groups.
The second carboxylate group of each hfbba ligand coordinates
to another paddlewheel unit, generating the extended corrugated
2-D layered structure (Figure 1b). In Co-HFMOF-D, 3-methyl
pyridine ligands occupy the axial positions of dicobalt paddle-
wheel, blocking the pores. By joining only Co2þ centers with
ligand atoms, topological simplification of Co-HFMOF-D shows
the formation of square shaped pores and the mode of attach-
ment of ligands with the metal center as shown in Figure 1c. In
Co-HFMOF-D, the sheets stack along b axis affording square-
shaped channels from the sheet cavities that run through the
gross structure (Figure 1d) creating a square grid topology. The
distance between equivalent atoms in between neighboring
sheets is approximately 3.5 Å. The ꢀCF3 groups of H2hfbba
ligands are directed to the outside of the larger square channels
while one DMF molecule is sitting inside the pore and two are
arranged in the interlayer region respectively. The pore diameter
for Co-HFMOF-D is ∼3.106 Å across, based on largest sphere
that could fit into the pore and also remain in contact with the van
der Waals surface.25 The ꢀCF3 groups of one channel in Co-
HFMOF-D are located in between the edges of the square
shaped channel with a minimal interlayer void (Figure 1d).
’ RESULTS AND DISCUSSION
Synthesis. We used 4,40-(hexafluoroisopropylidene) bis-
(benzoic acid) because (a) a twisted conformation of this ligand
could lead to a possible helical architecture,12a (b) different
deprotonated degrees of the ligands under different reaction
conditions may result in variable coordination modes in the
products, and (c) long and bent molecular structure of this
primary building unit may lead to the formation of microporous
coordination frameworks with channels. Influence of the solvent
(DMF/H2O) on the structure of these MOFs was reflected in
their structure. Co-HFMOF-D and Mn-HFMOF-D, synthesized
from DMF, contain 2-D connectivity whereas Co-HFMOF-W
and Mn-HFMOF-W, synthesized from H2O, are 3-D in nature.22
It is noteworthy that our previous experience while synthesizing
HF-MOFs from water resulted in zero or one-dimensional (1-D)
connectivity, whereas the same from DMF created a 3-D
structure. We will first discuss the crystal structure of HF-MOFs
that have been synthesized in DMF and follow that by a
discussion of the structures synthesized in H2O.
3857
dx.doi.org/10.1021/ic1017246 |Inorg. Chem. 2011, 50, 3855–3865

Inorganic Chemistry
ARTICLE
Figure 1. Crystal structure of Co-HFMOF-D. (a) Ball and Stick representation of the SBU showing the paddle-wheel motif of Co2þ. Two 3-methyl-
pyridine ligands occupy the axial positions. (b) 2-D coordination layer in Co-HFMOF-D with Co2þ paddle-wheel binuclear nodes (view down c axis).
(c) Topological simplification of Co-HFMOF-D, by joining only Co2þ centers (magenta) with carbon atoms of isopropyl group (black). (d)
Coordination layer in Co-HFMOF-D (view down b axis) showing the 3.106 Å channels. Hydrogen atoms, guest molecules, and 3-methyl-pyridines are
omitted for clarity. Color code: Co (magenta), N (blue), O (red), C (black), F (green).
Figure 2. Crystal structure of Mn-HFMOF-D. (a) Ball and Stick representation of the SBU showing the binuclear M2N2(μ2-CO2)2 unit. (b) 2-D
coordination layer in Mn-HFMOF-D with each hfbba ligand is connected to two Mn2þ metal centers (view down a axis). (c) Zigzag network topology of
Mn-HFMOF-D, by joining only Mn2þ centers (green) with carbon atoms of isopropyl group (black). (d) Space fill Mn-HFMOF-D (view down b axis)
showing the 3.002 Å channels; note the large interlayer void compared to Co-HFMOF-D. Hydrogen atoms, guest molecules, and 3-methyl-pyridines are
omitted for clarity. Color code: Mn (green), N (blue), O (red), C (black), F (light green).
The 2-D parallel interpenetrating network is reinforced by the
found in Mn-HFMOF-D. As a result there are two types of SBUs
in the binuclear Mn-HFMOF-D unit (Figure 2a). Among these
SBUs, one is in octahedral co-ordination geometry as four hfbba
ligands [MnoctꢀO distance ranges from 2.158 (3) to 2.185 (2) Å]
and two 3-methyl pyridine ligands [MnꢀN = 2.266 (3) Å] are
coordinated. Another SBU is in the square planar co-ordination
sphere where only four hfbba ligands [Mn ꢀO distance ranges
from 2.113 (3) to 2.154 (2) Å and OꢀMnꢀO angle ranges from
existence of other noncovalent interactions like CꢀH
F
3 3 3
hydrogen bonds (D, 3.327 Å; d, 2.774 Å; θ, 117.32°).26
Crystal Structure of [Mn2(hfbba)2(3-mepy)] (H2O) (Mn-
3
HFMOF-D). In the 2-D structure of Mn-HFMOF-D, the asym-
metric unit is composed of one Mn2þ ion, one hffbba ligand, one
3-methyl pyridine ligand, and one lattice H2O molecule. Two
different types of co-ordination environments around Mn2þ are
3858
dx.doi.org/10.1021/ic1017246 |Inorg. Chem. 2011, 50, 3855–3865

Inorganic Chemistry
ARTICLE
Figure 3. Crystal structure of Co-HFMOF-W/Mn-HFMOF-W. (a) Ball and stick representation of the SBU of Co-HFMOF-W showing the
coordination environment around the metal. (b) Coordinated hfbba ligands form the zigzag type structure along the crystallographic ac plane. (c) Zigzag
network topology of M-HFMOF-D, by joining only Mþ2 centers (magenta) with carbon atoms of isopropyl group (black). (d) Space filling model along
crystallographic ab plane shows the formation of a 1-D channel assembling these square shaped pores. Hydrogen atoms, guest molecules, and 3-methyl-
pyridines are omitted for clarity. Color code: M (magenta), N (blue), O (red), C (black), F (light green).
89.42° to 95.09°] are attached to the metal center. In this
structure, these octahedral and square planar metal centers are
arranged alternatively along the crystallographic b axis (Figure 2b).
The crystal structure of Mn-HFMOF-D adopts a 2-D arrangement
as the co-ordination of Mn2þꢀhfbbaꢀMn2þ propagates along the c
axis and simultaneously the MnꢀCO2ꢀMn propagates along the b
axis. Since the octahedral Mn2þ sites are blocked by 3-methyl
pyridine, which is a monodentate ligand, the crystal structure fails
to propagate along the crystallographic a axis. In the crystal
structure of Mn-HFMOF-D, each hfbba ligand is connected to
two Mn2þ metal centers, that is, octahedral and square planar
respectively through a zigzag fashion as shown in Figure 2b. By
joining only Mn2þ centers with ligand atoms, the topological
simplification of Mn-HFMOF-D shows the formation of a zigzag
network and the mode of attachment of ligands with the metal
center (Figure 2c). In the structure of Mn-HFMOF-D, the
propagation of accessible square shaped pores of about 3.0 Å
pore diameter is along the b axis in which lattice water molecules
are sitting inside. Here ꢀCF3 groups are protruding outside the
adjacent channels within interlayers which are spaced at 2.847 Å,
in zigzag manner (Figure 2d). Unlike Co-HFMOF-D, ꢀCF3
groups of one channel in Mn-HFMOF-D are located on top of
the square shaped channel edges with a significant interlayer
void. The 2-D parallel interpenetrating network is reinforced by
Each octahedral Mn2þ/Co2þ ion is surrounded by four oxygens
from hfbba ligands [MꢀO distance ranges from 2.071 (2) to
2.212 (2) Å], one oxygen from H2O [MꢀO distance =2.169-
(3)ꢀ2.224(2) Å], and one nitrogen from 3-methyl pyridine
ligand [MꢀN distance = 2.124ꢀ2.248 Å]. In Mn-HFMOF-W
and Co-HFMOF-W, the metalꢀmetal distance is 4.494 Å to
4.616 Å, which are connected through the COOꢀ group of hfbba
ligands. In the SBU of Mn-HFMOF-W and Co-HFMOF-W, on
the adjacent metal center 3-methyl pyridine ligands are coordi-
nated above and below positions alternatively (Figure 3a). The
coordinated water molecule is coordinated on the opposite side
of 3-methyl pyridine ligand. Four hfbba ligands are coordinated
to adjacent metal centers from one carboxyl group which extends
further joining to the next SBU. In the structure of Mn-HFMOF-
W and Co-HFMOF-W, alternatively joined 3-methyl pyridine
ligands are interdigited in the pores by blocking them through the
ab plane. In these structures, each hfbba ligand coordinates with
two adjacent metal centers through one of its carboxyl groups,
which extends further forming the hexagonal pores along with
interpenetration of 3-methyl pyridine and coordinated water
molecules inside. Coordinated hfbba ligands form the zigzag type
structure along the crystallographic ac plane (Figure 3b). By
joining only the Co2þ/Mn2þ centers with ligand atoms, the
topological simplification of Mn-HFMOF-W and Co-HFMOF-
W shows the formation of a zigzag network and the mode of
attachment of ligands with metal center as shown in Figure 3c.
The V shaped hfbba ligand when coordinating with the metals
gives the square shaped pores. Space filling model of these MOFs
along crystallographic ab plane shows the formation of a 1-D
channel assembling these square shaped pores (Figure 3d).
We have synthesized four new polymeric frameworks Co-
HFMOF-D, Co-HFMOF-W, Mn-HFMOF-D, and Mn-HFMOF-
W as shown in Scheme 1, which forms 2-D and 3-D networks
with diverse architectures depending on the solvent of synthesis.
We expected that the insertion of additional 3-picoline ligand in
the synthesis media should have a crucial effect, as they induces
the ΠꢀΠ stacking interactions affecting the dimensionality of
the existence of other noncovalent interactions like CꢀH
F
3 3 3
hydrogen bonds (D, 3.302 Å; d, 2.530 Å; θ, 140.52°).26
Crystal Structures of [Mn(hfbba)(3-mepy)(H2O)] (Mn-
HFMOF-W) and [Co(hfbba)(3-mepy)(H2O)] (Co-HFMOF-W).
Three dimensional Mn-HFMOF-W and Co-HFMOF-W have
been synthesized from H2O, using hydrothermal conditions in
an acid digestion bomb at 120 °C. Mn-HFMOF-W and Co-
HFMOF-W are iso-structural containing Mn2þ and Co2þ metal
centers (see the unit cell dimensions in Table 1) in the orthor-
hombic Pna21 space group. The asymmetric unit of Mn-
HFMOF-W and Co-HFMOF-W contains one crystallographi-
cally independent Mn2þ/Co2þ ion, one hfbba ligand, one
3-methyl pyridine ligand, and one coordinated H2O molecule.
3859
dx.doi.org/10.1021/ic1017246 |Inorg. Chem. 2011, 50, 3855–3865

Inorganic Chemistry
ARTICLE
Figure 5. Different types of SBUs observed in all the HF-MOFs
reported in the paper.
show formation of a 3-D framework with interdigited 3-methyl
pyridine molecules (Figures 3a and 3d). Also, in these two HF-
MOFs open metal sites can be observed as they contain the
coordinated H2O molecules which could be removed by strong
evacuation.
Figure 4. (a) μb2ꢀOCO bridging mode observed in Co-HFMOF-W,
Mn-HFMOF-W, and Mn-HFMOF-D. (b) μb2ꢀOCO bridging mode
observed in Co-HFMOF-D.
Thermal Stability, PXRD Analysis. To examine the architec-
tural and thermal stability of HF-MOFs reported in this paper, we
prepared them at the gram scale to allow detailed investigation of
the aforementioned properties. TGA performed on the as-
synthesized Co-HFMOF-D, Co-HFMOF-W, Mn-HFMOF-D,
and Mn-HFMOF-W revealed that these compounds have high
thermal stability (see Section S3 in the Supporting Informa-
tion for all data and interpretations regarding guest mobility
and thermal stability of these HF-MOFs). The TGA trace for
Co-HFMOF-D showed a gradual weight-loss step of ∼13.5%
(15ꢀ200 °C), corresponding to escape of all DMF in the pores
(3 DMF; calcd. ∼14%) followed by a sharp weight loss (200ꢀ
450 °C) probably because of the decomposition of the coordi-
nated 3-methyl pyridine molecules before decomposition of the
framework. The TGA of Mn-HFMOF-D and Mn-HFMOF-W
shows the sharp weight loss of ∼4.5% (15ꢀ100 °C) correspond-
ing to escape of all H2O molecules in pores (1 H2O; calcd.
∼3.5% for Mn-HFMOF-W and ∼2.7% for Mn-HFMOF-D)
followed by a plateau before a sharp weight loss (200ꢀ300 °C)
probably because of the decomposition of the coordinated
3-methyl pyridine molecules. After 300 °C, the framework
decomposes completely giving a 40% residue. The TGA of
Co-HFMOF-W shows a gradual weight loss step of ∼11.5%
(15ꢀ125 °C) corresponding to the loss of coordinated and
framework water molecules (1 H2O; calcd. ∼4.5%) followed by
the decomposition of the framework probably because of decom-
position of 3-methyl pyridine molecules and escape of coordi-
nated H2O molecules.
To confirm the phase purity of the bulk materials, PXRD
experiments were carried out on all complexes. The PXRD of
experimental and computer-simulated patterns of all of them are
shown in the Supporting Information (Figure S1 to S4 in ESI).
As shown in the figures, all major peaks of the experimental
PXRD patterns of compounds Co-HFMOF-D, Co-HFMOF-W,
Mn-HFMOF-D, and Mn-HFMOF-W match quite well with that
of simulated PXRDs, indicating their reasonable crystalline phase
purity. The experimental pattern of Co-HFMOF-D has a few
diffraction lines that are unindexed and some that are slightly
broadened in comparison with those simulated patterns. This is
probably due to the loss of DMF molecules from the lattice
because of grinding during the analysis.
the resulting polymeric framework, and therefore its square grid
topology. In all the structures 3-picoline occupies the axial
position of the M2N2(μ2-CO2)2 or M2N1O1(μ2-CO2)2 the co-
ordination sphere (Figure 4). Bimetallic clusters formed by co-
ordination of metal centers with carboxylate groups play an
important role in the determination of the architecture of the
resultant framework. In the HF-MOFs reported in this paper, the
co-ordination mode is μb2ꢀOCO, that is, both the carboxylate
oxygen atoms are involved in the co-ordination with two Mþ2
atoms in monodentate fashion (See Scheme 1 in Supporting
Information for a detailed representation of the connectivity of
hfbba2ꢀ). Although the co-ordination mode is same in all HF-
MOFs, their dimensionality, SBU, and resultant frameworks are
totally different from each other. It seems that the solvent of
synthesis and the conditions for reaction are affecting the net-
work structures. Co-HFMOF-D and Mn-HFMOF-D synthesized
from DMF have the 2-D structure, whereas Co-HFMOF-W [flack
parameter: 0.01(2)] and Mn-HFMOF-W [flack parameter: 0.04-
(2)]27 synthesized from H2O have the isostructural 3-D archi-
tecture with an octahedral SBU in the same Pna21 space group as
shown in Figure 5. The adoption of a noncentrosymmetric space
group and 21 screw axis by these two HF-MOFs could be
attributed to the bent nature of the hfbba link.28 But Co-
HFMOF-D and Mn-HFMOF-D synthesized from DMF have
different structures (Co-HFMOF-D, octahedral SBU with pad-
dlewheel; Mn-HFMOF-D, octahedral and square planar SBU in
same structure) with different space groups (C2/c in Co-
HFMOF-D and C2 in Mn-HFMOF-D). Although combination
of hfbba2ꢀ with Mþ2 can produce 10 possible bridging modes of
hfbba2ꢀ, we observe only one co-ordination mode (μb2ꢀOCO)
along this series (Figure 4), even we changed solvent and
synthetic conditions. Tetradentate bridging mode of hfbba2ꢀ
results in the formation of bimetallic tetracarboxylate clusters in
all the HF-MOFs, where apical positions are occupied either by
3-methyl pyridine or coordinated H2O molecules (Figure 5).
Within these HF-MOFs, Co-HFMOF-D and Mn-HFMOF-D
show formation of 2-fold parallel 2-Df2-D interpenetration
with a 1-D channel through the crystallographic ac plane (Figures 1d
and 2d). Co-HFMOF-W and Mn-HFMOF-W on the other hand
3860
dx.doi.org/10.1021/ic1017246 |Inorg. Chem. 2011, 50, 3855–3865

Inorganic Chemistry
ARTICLE
Gas Adsorption Experiments. The crystal structures of these
HF-MOFs confirmed that all of them have small pores of 3ꢀ4 Å
in diameter, so we concentrated on the gas adsorption studies of
these HF-MOFs. Recently researchers investigated that open
metal sites and solvent free frameworks are more useful for gas
adsorption. So as-synthesized samples of Co-HFMOF-D, Co-
HFMOF-W, Mn-HFMOF-D, and Mn-HFMOF-W were im-
mersed in dry chloroform at ambient temperature for 72 h,
evacuated at ambient temperature for 24 h, then at an elevated
temperature 100 °C for 36 h under ultrahigh vacuum (10ꢀ8
mbar) overnight, to create a solvent free framework. Samples
thus obtained were optimally evacuated, as evidenced by their
well-maintained PXRD patterns and the long plateau (ambient
temperature to 350 °C) in their TGA traces.
All of these four HF-MOFs are nonporous to N2 as they have a
lesser aperture size than the kinetic diameter of N2 (3.6 Å);
however, these HF-MOFs are able to take the H2 (2.89 Å) and
CO2 (3.4 Å) as they have a lesser kinetic diameter. Furthermore,
the low kinetic energy of the N2 molecules at 77 K result in N2
molecules being unable to effectively enter small pores.29 All
these HF-MOFs show reversible type I H2 and CO2 adsorption
isotherms at 77 K and 298 K, respectively. Co-HFMOF-D
showed highest reversible type I H2 and CO2 adsorption in this
series, that is, 0.78 wt % and 1.48 mmol/g as pressure approaches
to 1 atm as shown in Figure 6. Iso-structural Co-HFMOF-W and
Mn-HFMOF-W show nearly the same 0.67 and 0.72 wt % of H2
uptake, and 1.20 and 1.34 mmol/g of CO2 adsorption. Mn-
HFMOF-D shows the lowest H2 (0.60 wt %) and CO2 (1.06
mmol/g) adsorption. This result is well anticipated as Co-
HFMOF-D contains the robust paddle-wheel Co(II) motif with
3-methyl pyridine pointing outward of the pore. As a result the
pores are accessible to gases. On the other hand Co-HFMOF-W
and Mn-HFMOF-W have 3-methyl pyridine molecules blocking
the pore. Although H2 adsorption for these HF-MOFs are
somewhat moderate, they still are comparable with the H2
adsorption of the highest capacity zeolites, some carbon materi-
als, and some other HF-MOFs reported in the literature11aꢀf,30
(see Table 2 for detailed comparison of H2 and CO2 uptake of F-
MOFs reported so far). It is noteworthy that these materials
show much higher volumetric H2 and CO2 uptake because of
their high material density (see section S4 in the Supporting
Information for a detailed description of volumetric H2 and CO2
uptake of the HF-MOFs reported).
Magnetic Properties. Magnetic interaction arises from the
effective coupling of the paramagnetic centers through bridging
groups of the crystal framework. Here we have shown how
magnetic interaction changes with the distance between para-
magnetic metal centers. The temperature dependence of the
magnetic susceptibility (χ) and the effective magnetic moment
(μeff) for Co-HFMOF-D and Co-HFMOF-W is shown in
Figure 7, panels a and b. At 300 K, μeff values were calculated as
Figure 6. H2 (77 K) and CO2 (298 K) isotherm of the HF-MOFs
reported in the paper. Filled and open symbols represent adsorption and
desorption branches, respectively.
Table 2. Hydrogen and Carbon Dioxide Uptake Data of HF-MOFs Reported so Far
name of MOFb
H2a wt %
CO2 mmol/g
[Zn2(tfbdc)2 (dabco)]11f
1.78 wt %
[Co3(hfbba)6 (phen)2]12a
0.90 wt %
[Cu2(hfbba)2 (3-mepy)2] (DMF)2 (3-mepy)12b
0.58 wt %
3
[Zn5(triazole)6 (tfbdc)2(H2O)2] (4H2O)11a
11c
0.43 wt %
3
[Cu(hfipbb)(H2hfipbb)0.5
]
0.23 wt %
[Co2(hfbba)2(3-mepy)2] (DMF)3 (Co-HFMOF-D)
0.78 wt %
1.48 mmol/g [298 K]
1.34 mmol/g [298 K]
1.20 mmol/g [298 K]
1.06 mmol/g [298 K]
2.67 mmol/g [195 K]
1.83 mmol/g [195 K]
1.04 mmol/g [293 K]
3
[Mn(hfbba)(3-mepy)(H2O)] (Mn-HFMOF-W)
0.72 wt %
[Co(hfbba)(3-mepy)(H2O)] (Co-HFMOF-W)
0.67 wt %
[Mn2(hfbba)2(3-mepy)] (H2O) (Mn-HFMOF-D)
0.60 wt %
3
[Zn2(hfipbb)2 (bpdab)] 2DMF11d
0.87 wt % [20 atm]
0.57 wt % [20 atm]
3
[Cd2(hfipbb)2 (DMF)2] 2DMF11d
3
[Zn2(hfbba)1.5] (DMF) 2(H2O)11e
11c
3
3
[Cu(hfipbb)(H2hfipbb)0.5
]
1.1 wt % [48 atm]
2.33 wt % [64 atm]
[Ag2 (Ag4-Tz6)]9a
a Here it should be noted that wherever pressure and temperature are not mentioned, there the pressure is 1 atm and the temperature is 77 K. b tfbdc =
Tetrafluoroterephthalic acid, dabco = 1,4-diazabicyclo[2.2.2]octane, hfbba = 4,40-(Hexafluoroisopropylidene) bis(benzoic acid), phen = 1,10-
phenanthroline, 3-mepy = 3-methyl pyridine, triazole = 1,2,4-triazole, Tz = 3,5-bis(trifluoromethyl)-1,2,4-triazole.
3861
dx.doi.org/10.1021/ic1017246 |Inorg. Chem. 2011, 50, 3855–3865

Inorganic Chemistry
ARTICLE
5.5 and 4.4 μB for Co-HFMOF-D and Co-HFMOF-W, respec-
tively, which are appreciably lower than the theoretical value of
7.7 μB for two Co2þ ions in an octahedral crystal field environ-
ment with 6 uncoupled spins. It can be noted from Figure 7,
panels a and b, that the temperature dependent decreasing trend
of μB is not the same for Co-HFMOF-D and Co-HFMOF-W.
Moreover, the χT is also larger for Co-HFMOF-D than Co-
HFMOF-W for the same number of Co2þ spins per molecular
cluster unit. The reason could be the presence of intercluster
coupling which is possible in the Co-HFMOF-D because of a
relatively smaller intercluster Co2þ center distance (CoꢀCo
distance = 2.746 Å). This also indicates the presence of short-
range magnetic interactions. The continuous decrease of the χT
product with decreasing T from room temperature values of 3.8
and 2.4 emu K/mol Oe to the lowest measured values of 0.8 and
0.6 emu K/mol Oe for Co-HFMOF-D and Co-HFMOF-W,
respectively, indicates the presence of antiferromagnetic ex-
change interaction between the two Co2þ (S = 3/2) metal
centers within a cluster.31 At 5 K, a magnetic moment of 1.3
and 1.15 μB per Co2þ center is observed for Co-HFMOF-D and
Co-HFMOF-W, respectively. These values are less than the spin
only values for one unpaired electron (1.73 μB) for Co2þ. The
field dependence of the magnetization at 5 K for Co-HFMOF-D
and Co-HFMOF-W is shown in Figure 7c. In the case of Co-
HFMOF-D we observed nonlinearity in the curve, but in Co-
HFMOF-W, it is close to linear (or nonlinearity is quite small).
The presence of nonlinearity and coercivity of 35 Oe in the
magnetization versus field shows the presence of short-range
interactions at low temperature in Co-HFMOF-D, which could
be due to the short inter Co2þ ion interaction.
The CurieꢀWeiss fit of the inverse molar susceptibility χꢀ1 in the
temperature regime 165ꢀ350 K yields θ = ꢀ278 and ꢀ55 K for Co-
HFMOF-D and Co-HFMOF-W, respectively. The negative sign of
the Weiss constant further suggests the presence of antiferromagnetic
interaction between near neighbors, although the anisotropy of the
octahedral Co2þ will also contribute to these values.32 The lower value
of the Weiss constant for Co-HFMOF-W than for Co-HFMOF-D can
be attributed to a larger inter Co2þ ion distance in Co-HFMOF-W
than in Co-HFMOF-D which reduces the inter cluster magnetic
interaction as indicated above. At temperatures below 100 K, in
the cases of Co-HFMOF-D the inverse molar susceptibility
deviates from a linear segment showing the characteristic of an
antiferromagnetic system because of short-range interaction only.
The straight line fit of the inverse molar susceptibility χꢀ1 in this
temperature regime in both the structures yields a Weiss constant
θ value near to 0 K. This magnetic behavior gives a picture where
the spins come to a halt because of spin frustration while aligning
in an antiparallel fashion with decreasing thermal motion. We did
not observe any divergence between the zero-field-cooled (ZFC)
and field-cooled (FC) data in both the samples.
Figure 7. Temperature dependence of the magnetic susceptibility χ
(left axis), the effective magnetic moment μeff (right axis) for (a) Co-
HFMOF-D and (b) Co-HFMOF-W. Insets show ball and stick repre-
sentation of the SBU of respective HF-MOFs showing the distance
between two neighboring Co2þ atoms as 2.746 Å and 4.494 Å in Co-
HFMOF-D and Co-HFMOF-W, respectively. (c) Field dependence of
the magnetization for Co-HFMOF-D and Co-HFMOF-W at 5 K. Inset
shows the opening of the hysteresis loop at 5 K for Co-HFMOF-D.
The temperature dependence of magnetic susceptibility and effec-
tive magnetic moment for Mn-HFMOF-D and Mn-HFMOF-W is
Figure 8. Temperature dependence of the magnetic susceptibility χ (left axis), the effective magnetic moment μeff (right axis) for (a) Mn-HFMOF-D
and (b) Mn-HFMOF-W. Insets show ball and stick representation of the SBU of respective HF-MOFs showing the distance between two neighboring
Mn2þ atoms, 3.732 Å and 4.616 Å, in Mn-HFMOF-D and Mn-HFMOF-W, respectively.
3862
dx.doi.org/10.1021/ic1017246 |Inorg. Chem. 2011, 50, 3855–3865

Inorganic Chemistry
ARTICLE
shown in Figure 8. At 300 K, the effective magnetic moment of
8.3 and 8.0 μB for Mn-HFMOF-D and Mn-HFMOF-W respec-
tively is once again appreciably lower than the theoretical value of
11.8 μB for two Mn2þ ions with 10 uncoupled spins. At 5 K, a
magnetic moment of 2.55 and 2.5 μB per Mn2þ center is
observed, a value slightly higher than the spin only value for
one unpaired electron (1.73 μB). The extrapolation of the inverse
molar susceptibility χꢀ1 in the temperature region (175ꢀ350 K)
yields θ = ꢀ30 K for Mn-HFMOF-D. The inverse molar
susceptibility χꢀ1 for Mn-HFMOF-W shows the paramagnetic
nature in the whole measured temperature range with a Weiss
constant θ value near 0 K. As in the case of Co-HFMOF-W, there
is no long-range magnetic ordering in the measured temperature
region in Mn-HFMOF-D and Mn-HFMOF-W. The degree of
spin frustration, f, in Mn-HFMOF-D is higher than 10, indicating
strong frustration, but there is no spin frustration in Mn-HFMOF-
W, since magnetic ordering is a cooperative effect which is
determined by the magnetic coupling between paramagnetic
centers through the bridging ligands. The framework structure
gives the advantage of tailoring the magnetic property of the
MOF by changing the paramagnetic metal center to center
distance by changing the ligand, whereas in case of inorganic
molecules this cannot be done.28 In MOFs we can have designer’s
materials according to the required property.
’ ASSOCIATED CONTENT
S
Supporting Information. Description of experimental de-
b
tails, including synthetic methods, crystallography, supplementary
figures, including TGA, infrared spectroscopy, PXRD profiles,
tables of crystallographic data, CIF files, and anisotropic thermal
ellipsoids for HF-MOFs reported in this paper. This material is
available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: r.banerjee@ncl.res.in. Fax: þ 91-20-25902636. Phone:
þ 91-20-25902535.
’ ACKNOWLEDGMENT
P.P. acknowledges CSIR for a project assistantship (PA-II) from
CSIR’s XIth Five Year Plan Project (NWP0022-H). R.B. acknowl-
edges Dr. S. Sivaram, Director NCL, for in-house project
(MLP020626) and CSIR’s XIth Five Year Plan Project (Grant
NWP0022-H) funding, and also Dr. B. D. Kulkarni, Dr. S. Pal,
and Dr. K. Vijaymohanan for their encouragement. Financial
assistance from the DST (SR/S1/IC-22/2009) & (SR/S5/NM-
104/2006) is acknowledged.
’ REFERENCES
’ CONCLUSION
(1) (a) Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W.; Chae, H. K.;
Eddaoudi, M.; Kim, J. Nature 2003, 423, 705. (b) Janiak, C. J. Chem. Soc.,
Dalton Trans. 2003, 2781. (c) Moulton, B.; Zaworotko, M. J. Chem. Rev.
2001, 101, 1629. (d) Eddaoudi, M.; Moler, D. B.; Li, H.; Chen, B.; Reineke,
T. M.; O’Keeffe, M.; Yaghi, O. M. Acc. Chem. Res. 2001, 34, 319. (e) Robson,
R. J. Chem. Soc., Dalton Trans. 2000, 3735. (f) Yaghi, O. M. Nat. Mater. 2007,
6, 92. (g) Mueller, U.; Schubert, M.; Teich, F.; Puetter, H.; Schierle-Arndt, K.;
Pastre, J. J. Mater. Chem. 2006, 16, 626. (h) Georgiev, I. G.; MacGillivray,
L. R. Chem. Soc. Rev. 2007, 36, 1239. (i) Corma, A.; Garcia, H.; Xamena,
F. X. L. Chem. Rev. 2010, 110, 4606. (j) James, S. L. Chem. Soc. Rev. 2003,
32, 276. (k) Yaghi, O. M.; Li, H.; Davis, C.; Richardson, D.; Groy, T. L. Acc.
Chem. Res. 1998, 31, 474. (l) Janiak, C. Angew. Chem., Int. Ed. Engl. 1997,
36, 1431. (m) Blake, A. J.; Champness, N. R.; Hubberstey, P.; Li, W.-S.;
Withersby, M. A.; Schroder, M. Coord. Chem. Rev. 1999, 183, 117.
(n) Murray, L. J.; Dinca, M.; Long, J. R. Chem. Soc. Rev. 2009, 38, 1294.
(o) Kesanli, B.; Cui, Y.; Smith, M.; Bittner, E.; Bockrath, B.; Lin, W. Angew.
Chem., Int. Ed. 2005, 44, 72. (p) Chen, B.; Xiang, S.; Qian, G. Acc. Chem. Res.
2010, 43, 1115.
(2) (a) Chen, B.; Liang, C.; Yang, J.; Contreras, D. S.; Clancy, Y. L.;
Lobkovsky, E. B.; Yaghi, O. M.; Dai, S. Angew. Chem., Int. Ed. 2006,
45, 1390. (b) Choi, H. J.; Suh, M. P. J. Am. Chem. Soc. 2004, 126, 15844.
(c) Pan, L.; Olson, D. H.; Ciemnolonski, L. R.; Heddy, R.; Li, J. Angew.
Chem., Int. Ed. 2006, 45, 616. (d) Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak,
D.; Wachter, J.; O’Keeffe, M..; Yaghi, O. M. Science 2002, 295, 469.
(e) Bourrelly, S.; Llewellyn, P.; Serre, C.; Millange, F.; Loiseau, T.; Ferey,
G. J. Am. Chem. Soc. 2005, 127, 13519. (f) Panella, B.; Hirscher, M.;
Puetter, H.; Mueller, U. Adv. Funct. Mater. 2006, 16, 520. (g) Liu, Y.;
Eubank, J. F.; Cairns, A. J.; Eckert, J.; Kravtsov, V. C.; Luebke, R.;
Eddaoudi, M. Angew. Chem., Int. Ed. 2007, 46, 3278.
A new series of partially fluorinated MOFs has been synthe-
sized solvothermally, using bent ligand hfbba2ꢀ and divalent
metal ions Co2þ and Mn2þ, along with terminal ligand 3-methyl
pyridine. The bridging tetradentate mode of hfbba2ꢀ produces
the bimetallic tetracarboxylate clusters in the all HF-MOFs. Co-
HFMOF-D and Mn-HFMOF-D, synthesized from DMF, show
formation of 2-fold parallel 2-Df2-D interpenetration with a
1-D channel whereas Co-HFMOF-W and Mn-HFMOF-W,
synthesized from H2O, show formation of a 3-D framework
with interdigited 3-methyl pyridine molecules in pores. These
results show that other factors like the solvent of synthesis, pH,
and reaction temperature also play an important role on the
adoption of the resulting MOF structure. In is noteworthy that
previous work on partially fluorinated MOFs and an explicit
comparison with nonfluorinated analogues imparted a disadvan-
tage for fluorination. On the other hand, our results suggest that
perfluorination is advantageous, which reinforces arguments
made by Yang et al. and Cheetham and co-workers. All the
HF-MOFs along this series shows comparable H2 and CO2
adsorption with other reported F-MOFs, and it is hard to prove
or speculate on the adsorption data for the closest nonfluorinated
MOF analogues of the MOFs we have reported in the paper. In
our opinion significant research activity is necessary before we
accept/discard the effect of exposed fluorine atoms regarding gas
adsorption. The Co2þ show dominantly antiferromagnetic cou-
pling followed by the appearance of short-range interaction at
low temperature in the case of Co-HFMOF-D which could be
due to the shorter inter Co2þ ion distances compared to those
of Co-HFMOF-W. Likewise, Mn-HFMOF-D shows a domi-
nantly antiferromagnetic nature whereas Mn-HFMOF-W shows a
paramagnetic nature in the whole measured temperature range.
We are continuing to utilize the other neutral bridging coligands
along with H2hfbba to design the new HF-MOFs with specific
structures and properties.
(3) (a) Caskey, S. R.; Wong-Foy, A. G.; Matzger, A. J. J. Am. Chem.
Soc. 2008, 130, 10870. (b) Millward, A. R.; Yaghi, O. M. J. Am. Chem. Soc.
2005, 127, 17998. (c) Morris, R. E.; Wheatley, P. S. Angew. Chem., Int.
Ed. 2008, 47, 4966. (d) Kumar, D.-K.; Das, A.; Dastidar, P. Cryst. Growth
Des. 2007, 7, 205. (e) Hu, S.; Zhang, J.-P.; Li, H.-X.; Tong, M.-L.; Chen,
X.-M.; Kitagawa, S. Cryst. Growth Des. 2007, 7, 2286. (f) Chen, B.-L.; Ma,
S.-Q.; Zapata, F.; Fronczek, F.-R.; Lobkocsky, E.-B.; Zhou, H.-C. Inorg.
Chem. 2007, 46, 1233. (g) Kitagawa, S.; Kitaura, R.; Noro, S. Angew.
Chem., Int. Ed. 2004, 43, 2334. (h) Thallapally, P. K.; Tian, J.; Motkuri,
3863
dx.doi.org/10.1021/ic1017246 |Inorg. Chem. 2011, 50, 3855–3865

Inorganic Chemistry
ARTICLE
R. K.; Fernandez, C. A.; Dalgarno, S. J.; McGrail, P. B.; Warren, J. E.;
Atwood, J. L. J. Am. Chem. Soc. 2008, 130, 16842. (i) Mckinlay, R. M.;
Thallapally, P. K.; Atwood, J. L. Chem. Commun. 2006, 2956. (j) Luo, J.;
Xu, H.; Liu, Y.; Zhao, Y.; Daemen, L. L.; Brown, C.; Timofeeva, T. V.;
Ma, S.; Zhou, H.-C. J. Am. Chem. Soc. 2008, 130, 9626.
(4) (a) Deshpande, R. K.; Minnaar, J. L.; Telfer, S. G. Angew. Chem.,
Int. Ed. 2010, 49, 4598. (b) Wu, C. D.; Hu, A.; Zhang, L.; Lin, W. B.
J. Am. Chem. Soc. 2005, 127, 8940. (c) Shultz, A. M.; Farha, O. K.; Hupp,
J. T.; Nguyen, S. T. J. Am. Chem. Soc. 2009, 131, 4204. (d) Alkordi,
M. H.; Liu, Y. L.; Larsen, R. W.; Eubank, J. F.; Eddaoudi, M. J. Am. Chem.
Soc. 2008, 130, 12639. (e) Horike, S.; Dinca, M.; Tamaki, K.; Long, J. R.
J. Am. Chem. Soc. 2008, 130, 5854. (f) Lin, W. B. J. Solid State Chem.
2005, 178, 2486. (g) Fujita, M.; Kwon, Y. J.; Washizu, S.; Ogura, K. J. Am.
Chem. Soc. 1994, 116, 1151. (h) Seo, J. S.; Whang, D.; Lee, H.; Jun, S. I.;
Oh, J.; Jeon, Y. J.; Kim, K. Nature 2000, 404, 982.
(5) (a) McKinlay, A. C.; Morris, R. E.; Horcajada, P.; Ferey, G.; Gref,
R.; Couvreur, P.; Serre, C. Angew. Chem., Int. Ed. 2010, 49, 2. (b) Rieter,
W. J.; Pott, K. M.; Taylor, K. M. L.; Lin, W. J. Am. Chem. Soc. 2008,
130, 11584. (c) Rieter, W. J.; Taylor, K. M. L.; An, H.; Lin, W. J. Am.
Chem. Soc. 2006, 128, 9024. (d) Horcajada, P.; Serre, C.; Maurin, G.;
Ramsahye, N. A.; Balas, F.; Vallet-Regi, M.; Sebban, M..; Taulelle, F.;
Ferey, G. J. Am. Chem. Soc. 2008, 130, 6774. (e) Freiberg, S.; Zhu, X. X.
Int. J. Pharmacol. 2004, 282, 1. (f) Soppimath, K. S.; Aminabhavi, T. M.;
Kulkarni, A. R.; Rudzinski, W. E. J. Controlled Release 2001, 70, 1.
(6) (a) Fang, Q. R.; Zhu, G. S.; Jin, Z.; Ji, Y. Y.; Ye, Y. W.; Xue, M.;
Yang, H.; Wang, Y.; Qiu, S.-L. Angew. Chem., Int. Ed. 2007, 46, 6638.
(b) Rosi, N. L.; Eckert, J.; Eddaoudi, M.; Vodak, D. T.; Kim, J.; O’Keeffe,
M.; Yaghi, O. M. Science 2003, 300, 1127. (c) Ma, S. Q.; Sun, D. F.;
Simmons, J. M.; Collier, C. D.; Yuan, D. Q.; Zhou, H. C. J. Am. Chem.
Soc. 2008, 130, 1012. (d) Furukawa, H.; Yaghi, O. M. J. Am. Chem. Soc.
2009, 25, 8876. (e) Furukawa, H.; Kim, J.; Ockwig, N. W.; O’Keeffe, M.;
Yaghi, O. M. J. Am. Chem. Soc. 2008, 130, 11650. (f) Kaye, S. S.; Dailly,
A.; Yaghi, O. M.; Long, J. R. J. Am. Chem. Soc. 2007, 129, 14176.
(g) Furukawa, H.; Miller, M. A.; Yaghi, O. M. J. Mater. Chem. 2007,
17, 3197. (h) Hayashi, H.; Cote, A. P.; Furukawa, H.; O’Keeffe, M.;
Yaghi, O. M. Nat. Mater. 2007, 6, 501. (i) Wong-Foy, A. G.; Matzger,
A. J.; Yaghi, O. M. J. Am. Chem. Soc. 2006, 128, 3494. (j) Choi, H. J.;
Dinca, M.; Long, J. R. J. Am. Chem. Soc. 2008, 130, 7848. (k) Dinca, M.;
Long, J. R. Angew. Chem., Int. Ed. 2008, 47, 6766.
(10) Fischer, R. A.; Woll, C. Angew. Chem., Int. Ed. 2008, 47, 8164.
(11) (a) Hulvey, Z.; Falcao, E. H. L.; Eckert, J.; Cheetham, A. K.
J. Mater. Chem. 2009, 19, 4307. (b) Hulvey, Z.; Sava, D. A.; Eckert, J.;
Cheetham, A. K. Inorg. Chem. 2011, 50 (2), 403. (c) Pan, L.; Sander,
M. B.; Huang, X.; Li, J.; Smith, M.; Bittner, E.; Bockrath, B.; Johnson,
J. K. J. Am. Chem. Soc. 2004, 126, 1308. (d) Yang, W.; Lin, X.; Blake, A. J.;
Wilson, C.; Hubberstey, P.; Champness, N. R.; Schroder, M. Inorg.
Chem. 2009, 48, 11067. (e) Fernandez, C. A.; Thallapally, P. K.; Motkuri,
R. K.; Nune, S. K.; Sumrak, J. C.; Tian, J.; Liu, J. Cryst. Growth Des. 2010,
10, 1037. (f) Chun, H.; Dybtsev, D. N.; Kim, H.; Kim., K. Chem.—Eur. J.
2005, 11, 3521.
(12) (a) Pachfule, P.; Dey, C.; Panda, T.; Vanka, K.; Banerjee, R.
Cryst. Growth Des. 2010, 10, 1351. (b) Pachfule, P.; Dey, C.; Panda, T.;
Banerjee, R. CrystEngComm 2010, 12, 1600.
(13) (a) Robson, R.; Abrahams, B. F.; Batten, S. R.; Gable, R. W.;
Hoskins, B. F.; Liu, J. Supramolecular Architecture; ACS Publications:
Washington, DC, 1992. (b) Hennigar, T. L.; MacQuarrie, D. C.; Losier,
P.; Rogers, R. D.; Zaworotko, M. J. Angew. Chem., Int. Ed. Engl. 1997,
36, 972. (c) Tong, M.-L.; Ye, B.-H.; Cai, J.-W.; Chen, X.-M.; Ng, S. W.
Inorg. Chem. 1998, 37, 2645. (d) Su, C.-Y.; Cai, Y.-P.; Chen, C.-L.; Smith,
M. D.; Kaim, W.; Zur Loye, H.-C. J. Am. Chem. Soc. 2003, 125, 8595.
(e) Meng, X.; Song, Y.; Hou, H.; Han, H.; Xiao, B.; Fan, Y.; Zhu, Y. Inorg.
Chem. 2004, 43, 3528. (f) Du, M.; Bu, X.-H.; Guo, Y.-M.; Liu, H.; Batten,
S. R.; Ribas, J.; Mak, T. C. W. Inorg. Chem. 2002, 41, 4904.
(14) (a) Burrows, A. D.; Cassar, K.; Friend, R. M. W.; Mahon, M. F.;
Rigby, S. P.; Warren, J. E. CrystEngComm 2005, 7, 548. (b) Chesman,
A. S. R.; Turner, D. R.; Deacon, G. B.; Batten, S. R. Chem. Commun.
2010, 46, 4899. (c) He, H.; Collins, D.; Dai, F.; Zhao, X.; Zhang, G.; Ma,
H.; Sun, D. Cryst. Growth Des. 2010, 10, 895.
(15) It should be noted that the fluorination referred to in the rest of
the article is only partial, as not all the hydrogens were substituted with
fluorines in the obtained crystal structures. Reference related to per-
fluorinated Metal Organic Framework (F-MOFs) has been provided in
reference 9a and 9b. Since we have reported only partially fluorinated
MOFs here, addition of an “H” to the acronyms has been done to reduce
the confusion.
(16) SMART, Version 5.05; Bruker AXS, Inc.: Madison, WI, 1998.
(17) SAINT-Plus, Version 7.03; Bruker AXS Inc.: Madison, WI,
2004.
(18) Sheldrick, G. M. SADABS, Version 2.03, and TWINABS, Version
1.02; University of G€ottingen: G€ottingen, Germany, 2002.
(19) Sheldrick, G. M. SHELXS ‘97; University of G€ottingen:
G€ottingen, Germany, 1997.
(20) Sheldrick, G. M. SHELXTL ‘97; University of G€ottingen:
G€ottingen, Germany, 1997.
(7) (a) Nakagawa, K.; Tanaka, D.; Horike, S.; Shimomura, S.;
Higuchia, M.; Kitagawa, S. Chem. Commun. 2010, 46, 4258. (b) Wang,
B.; Cote, A. P.; Furukawa, H.; O’Keeffe, M.; Yaghi, O. M. Nature 2008,
453, 207. (c) Walton, K. S.; Millward, A. R.; Dubbeldam, D.; Fros, H.;
Low, J. J.; Yaghi, O. M.; Snurr, R. Q. J. Am. Chem. Soc. 2008, 130, 406.
(d) Llewellyn, P. L.; Bourrelly, S.; Serre, C.; Vimont, A.; Daturi, M.;
Hamon, L.; Weireld, G. D.; Chang, J.-S.; Hong, D.-Y.; Hwang, Y. K.;
Jhung, S. H.; Ferey, G. Langmuir 2008, 24, 7245. (e) Yazaydn, A. O.;
Snurr, R. Q.; Park, T.-H.; Koh, K.; Liu, J.; LeVan, M. D.; Benin, A. I.;
Jakubczak, P.; Lanuza, M.; Galloway, D. B.; Low, J. J.; Willis, R. R. J. Am.
Chem. Soc. 2009, 131, 18198. (f) Chandler, B. D.; Cramb, D. T.; Shimizu,
G. K. H. J. Am. Chem. Soc. 2006, 128, 10403. (g) Banerjee, R.; Phan, A.;
Wang, B.; Knobler, C.; Furukawa, H.; O’Keeffe, M.; Yaghi, O. M. Science
2008, 319, 939. (h) Banerjee, R.; Furukawa, H.; Britt, D.; Knobler, C.;
O’Keeffe, M.; Yaghi, O. M. J. Am. Chem. Soc. 2009, 131, 3875.
(8) (a) Blomqvist, A.; Araujo, C. M.; Srepusharawoot, P.; Ahuja, R.
PNAS. 2007, 104, 20173. (b) Li, Z.; Zhu, G.; Lu, G.; Qiu, S.; Yao, X.
J. Am. Chem. Soc. 2010, 132, 1490. (c) Dinca, M.; Dailly, A.; Liu, Y.;
Brown, C. M.; Neumann, D. A.; Long, J. R. J. Am. Chem. Soc. 2006,
128, 16876. (d) Choi, H. J.; Dinca, M.; Dailly, A.; Long, J. R. Energy
Environ. Sci. 2010, 3, 117. (e) Sumida, K.; Horike, S.; Kaye, S. S.; Herm,
Z. R.; Queen, W. L.; Brown, C. M.; Grandjean, F.; Long, G. J.; Dailly, A.;
Long, J. R. Chem. Sci. 2010, 1, 184. (f) Dinca, M.; Dailly, A.; Tsay, C.;
Long, J. R. Inorg. Chem. 2008, 47, 11. (g) Roswell, J. L. C.; Yaghi, O. M.
J. Am. Chem. Soc. 2006, 128, 1304. (h) Roswell, J. L. C.; Yaghi, O. M.
Angew. Chem., Int. Ed. 2005, 44, 4670.
(21) Spek, A. L. PLATON, A Multipurpose Crystallographic Tool;
Utrecht University: Utrecht, The Netherlands, 2005.
(22) The abbreviation ꢀD and ꢀW corresponds to H2O and DMF
respectively.
(23) Addison, A. W.; Rao, T. N.; Reedijk, J.; Rijn, J. V.; Verschoor,
G. C. J. Chem. Soc., Dalton Trans. 1984, 1349.
(24) (a) O’Keefe, M.; Eddaoudi, M.; Li, H.; Reineke, T. M.; Yaghi,
O. M. J. Solid State Chem. 2000, 152, 3. (b) Tranchemontagne, D. J.;
Mendoza-Cortes, J. L.; O’Keefe, M.; Yaghi, O. M. Chem. Soc. Rev. 2009,
38, 1257. (c) Mellot-Draznieks, C.; Dutour, J.; Ferey, G. Angew. Chem.,
Int. Ed. 2004, 43, 6290.
(25) All calculation were done using Cerius2 software (Ver. 4.2,
Accelrys); van der Waals radii were taken into consideration in all cases
(C, 1.70; H, 1.20; O, 1.52; N, 1.55; Cl, 1.79; Br, 1.89 Å).
(26) (a) Golovanov, D. G.; Lyssenko, K. A.; Antipin, M. Y.;
Vygodskii, Y. S.; Lozinskaya, E. I.; Shaplov, A. S. CrystEngComm 2005,
7, 53. (b) Althoff, G.; Ruiz, G.; Rodríguez, V.; Lꢀopez, G.; Pꢀerez, J.; Janiak,
C. CrystEngComm 2006, 8, 662. (c) Takahashi, S.; Jukurogi, T.; Katagiri,
T.; Uneyama, K. CrystEngComm 2006, 8, 320. (d) Choudhury, A. R.;
Guru Row, T. N. CrystEngComm 2006, 8, 265. (e) Mariaca, R.; Behrnd,
N.-R.; Eggli, P.; Stoeckli-Evans, H.; Hulliger, J. CrystEngComm 2006,
8, 222. (f) D’Oria, E.; Novoa, J. J. CrystEngComm 2008, 10, 423.
(g) Desiraju, G. R.; Steiner, T. In IUCr Monograph on Crystallography;
(9) (a) Yang, C.; Wang, X.; Omary, M. A. J. Am. Chem. Soc. 2007,
129, 15454. (b) Yang, C.; Wang, X. P.; Omary, M. A. Angew. Chem., Int.
Ed. 2009, 48, 2500.
3864
dx.doi.org/10.1021/ic1017246 |Inorg. Chem. 2011, 50, 3855–3865

Inorganic Chemistry
ARTICLE
Oxford Science: Oxford, 1999; Vol. 9. (h) Ruiz, J.; Rodríguez, V.; Haro,
C. D.; Espinosa, E.; Pꢀerez, J.; Janiak, C. Dalton Trans. 2010, 39, 3290.
(27) (a) Flack, H. D.; Bernardinelli, G. Acta Crystallogr. 1999,
A55, 908. (b) Flack, H. D. Acta Crystallogr. 1983, A39, 876.
(28) (a) Janiak, C.; Chamayou, A.-C.; Royhan Uddin, A. K. M.;
Uddin, M.; Hagen, K. S.; Enamullah, M. Dalton Trans. 2009, 3698.
(b) Gil-Hernandez, B.; Gili, P.; Vieth, J. K.; Janiak, C.; Sanchiz, J.
Inorg. Chem. 2010, 49, 7478.
(29) Li, J.-R.; Kuppler, R. J.; Zhou, H.-C. Chem. Soc. Rev. 2009,
38, 1477.
(30) (a) Zhao, X.; Xiao, B.; Fletcher, A. J.; Thomas, K. M. J. Phys.
Chem. B. 2005, 109, 8880. (b) Sircar, S.; Golden, T. C.; Rao, M. B.
Carbon 1996, 34, 1.
(31) Ouellette, W.; Prosvirin, A. V.; Valeioh, J.; Dunbar, K. R.;
Zubieta, J. Inorg. Chem. 2007, 46, 9067.
(32) Daniel, C.; Hart, H. J. Am. Chem. Soc. 2009, 131, 5101.
3865
dx.doi.org/10.1021/ic1017246 |Inorg. Chem. 2011, 50, 3855–3865