Enhancement of H2 adsorption in coordination framework materials by use of ligand curvature

Article abstract of DOI:10.1002/chem.200802292

Solvothermal reaction of the ligands H4L110 ((2,7-phenanthrenediyl)- diisophthalic acid) and H4L111 ([2,7-(9,10-dihydrophenanthrenediyl)]diiso- phthalic acid) with Cu(NO3)22.5 H2O in a slightly acidified mixture of DMF/ 1,4-dioxane/H2O afforded the solvat

Full text of DOI:10.1002/chem.200802292

FULL PAPER
DOI: 10.1002/chem.200802292
Enhancement of H2 Adsorption in Coordination Framework Materials by
Use of Ligand Curvature
Sihai Yang,[a] Xiang Lin,[a] Anne Dailly,[b] Alexander J. Blake,[a] Peter Hubberstey,[a]
Neil R. Champness,*[a] and Martin Schrçder*[a]
Abstract: Solvothermal reaction of the
ligands H4L110 ((2,7-phenanthrenediyl)-
diisophthalic acid) and H4L111 ([2,7-
(9,10-dihydrophenanthrenediyl)]diiso-
the same NbO framework structure,
differing only at the 9 and 10 positions
of the phenanthrene group. The BET
surface areas for desolvated NOTT-110
and NOTT-111 were estimated to be
2960 and 2930 m2 gÀ1, respectively.
Compared with their phenyl analogues,
introduction of phenanthrene groups to
these porous CuII–carboxylate frame-
work materials leads to an enhance-
ment of H2 adsorption. Thus, the H2
isotherms for desolvated NOTT-110
and NOTT-111 confirm 2.64 and
2.56 wt% total H2 uptake, respectively,
at 1 bar and 78 K. NOTT-110 shows a
high total H2 storage capacity of
7.62 wt% at 55 bar and 77 K (8.5 wt%
at saturation) with a total volumetric
capacity of 46.8 gLÀ1 at 55 bar and
77 K.
ACHTUNGTRENNUNGphthalic acid) with CuACHTUNGTRNEN(GUN NO3)2·2.5H2O
in a slightly acidified mixture of DMF/
1,4-dioxane/H2O afforded the solvated
framework compounds [Cu
(H2O)2](DMF)7.5A(H2O)5 (NOTT-110)
and [Cu2A (H2O)2](DMF)7.5A(H2O)5
(L111
(NOTT-111), respectively. Crystal
(L110)-
2ACHTUNGTRENNUNG
A
R
CHTUNGTRENNUNG
Keywords: carboxylate ligands
·
C
)
E
N
CHTUNGTRENNUNG
copper · hydrogen storage · metal–
organic frameworks · microporous
materials
structure determinations confirmed
that NOTT-110 and NOTT-111 have
Introduction
177 (11.3 wt% at 70 bar),[3,4] IRMOF-20 (6.7 wt% at 80 bar
excess uptake),[4] [(Mn4Cl)
3A(btt)8] (BTT=1,3,5-benzenetris-
tetrazole; 6.9 wt% at 90 bar),[5] [Cu
2A(tptc)] (NOTT-101)
(H4tptc=1,1’,4’,1’’terphenyl-3,5,3’’,5’’-tetracarboxylic acid;
6.06 wt% at 20 bar),[6] [Cu
2A(qptc)] (NOTT-102) (H4qptc=
CTHUNGTRENNUNG
The utilisation of hydrogen (H2) as a substitute for fossil
fuels for mobile applications is in part predicated on the de-
velopment of viable storage systems.[1] Metal–organic coor-
dination frameworks composed of metal centres and clusters
bridged by organic linkers are being studied extensively be-
cause they can show high permanent porosity with unusually
high surface areas.[2] Several such materials have now for-
mally reached or exceeded 6.0 wt% H2 storage at reasona-
ble pressures (<90 bar) albeit at 77 K. These include MOF-
CHTUNGTRENNUNG
CTHUNGTRENNUNG
1,1’,4’,1’’,4’’,1’’’-quaterphenyl-3,5,3’’’,5’’’-tetracarboxylic acid;
6.07 wt% at 20 bar),[6] and more recently MOF-5 (10.0 wt%
at 100 bar).[7] H2 sorption by these materials displays excel-
lent reversibility and fast kinetics, but the weak dispersive
interactions that hold H2 molecules within the frameworks
require cryogenic operating temperatures and reasonably
high pressures to afford significant H2 uptake. A great deal
of effort is being focused on devising methodologies to in-
crease the adsorption enthalpy for H2 and to maximise volu-
metric and gravimetric H2 storage capacities. Attempts to
achieve higher heats of adsorption are focused on 1) con-
structing frameworks with very narrow pores, in which over-
lapping potentials from two or more pore walls interact with
a single H2 molecule;[8] 2) construction of open metal coor-
dination sites to provide a stronger direct H2 binding site to
the metal nodes;[5,9,10] 3) entanglement of frameworks
(framework catenation)[11] and 4) doping with light, non-
transition electron-donating metal(0) centres such as Li, Na
and Mg to introduce electrostatic and orbital interaction
contributions instead of solely dispersive interactions.[12] En-
[a] S. Yang, Dr. X. Lin, Prof. Dr. A. J. Blake, Dr. P. Hubberstey,
Prof. Dr. N. R. Champness, Prof. Dr. M. Schrçder
School of Chemistry, University of Nottingham
University Park, Nottingham NG7 2RD (UK)
Fax : (+44)115-951-3563
E-mail: M.Schroder@nottingham.ac.uk
Neil.Champness@nottingham.ac.uk
[b] Dr. A. Dailly
Chemical and Environmental Sciences Laboratory
General Motors Corporation, Warren, MI 48090 (USA)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200802292. It includes additional
views of the crystal structures, TGA and PSD analysis, powder XRD
patterns, technical details for gas adsorption experiments and detailed
D2 and H2 isotherms
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hancing H2 storage capacity thus remains a major challenge,
and strategies that focus solely upon increasing pore vol-
umes do not necessarily afford the best H2 storage materi-
als.[2h,6] Currently, the pursuit of higher H2 adsorption ca-
pacities has been developed either by topological engineer-
ing to optimise pore size and shape and to enlarge pore vol-
umes,[6,13] or by insertion of other adsorbate surfaces inside
the pores.[14]
and 9,10-dihydrophenanthrene analogues, NOTT-110 and
NOTT-111, respectively, and investigated the correlation of
H2 adsorption behaviour with pore surface modification in
these materials.
Results and Discussion
We have explored a series of coordination frameworks
based on CuII–paddlewheel complexes with biphenyl-
(NOTT-100), terphenyl- (NOTT-101) or quaterphenyl-
(NOTT-102) 3,3’,5,5’-tetracarboxylic acids.[6] The strategy of
using longer ligands to create larger pores has significantly
improved the total H2 uptake from 4.02 wt% for NOTT-100
to 6.07 wt% for NOTT-102. However, this strategy appears
to fail when the pore size and pore volume reach certain
threshold values: the much larger pore volume of NOTT-
102 (1.14 cm3 gÀ1) displays H2 uptake at 20 bar, which is simi-
lar to that found for NOTT-101 (1.08 cm3 gÀ1).[6] Therefore,
we have investigated chemical modification of the tetracar-
boxylate ligand to enhance further the H2 uptake, including
introduction of functionalised or bulky groups into the
framework. We have obtained the desired phenanthrene
Introduction of functionalised groups into the framework
was accomplished by the replacement of the biphenyl group
in the quaterphenyl-3,3’,5,5’-tetracarboxylic acid with
a
phenanthrene group. The ligands were synthesised by
Suzuki coupling of benzene-1,3-dicarboxyethylester-5-boron-
ic acid and 2,7-dibromophenanthrene (for H4L110) or 2,7-di-
bromo-9,10-dihydrophenanthrene (for H4L111). The study of
framework materials derived from tetracarboxylate iso-
phthalate ligands is gaining much current interest.[6,15] Solvo-
thermal reaction of the ligands (H4L110 or H4L111) with Cu-
AHCTUNGTRENNUNG
C
)
E
N
CHTUNGTRENNUNG
A
)
E
N
CHTUNGTRENNUNG
Single-crystal X-ray structure determinations of NOTT-110
and NOTT-111 confirmed that the two frameworks are iso-
structural NbO lattices incorporating binuclear paddle-
wheel–CuII nodes (Figure 1), and differ only at the 9 and 10
positions of the phenanthrene group. A view along the crys-
tallographic c axis (Figure 2a) shows hexagonal channels
that run through the structures of NOTT-110 and NOTT-
111. The diameter of the channel is predefined by the geom-
etry of the [Cu2ACHTNUTRGNEG(UN O2CR)4] node and the span of the dicarbox-
ylatophenyl moiety of the isophthalate group on each termi-
nus of the bridging ligand. Therefore, the diameters of the
channels are the same in both structures, approximately
5.0 ꢁ and the channels are interconnected through triangu-
lar windows, which can be seen along the crystallographic a
Figure 1. Views of a) the 4-connected Cu2ACTHNUGTRNEG(UN O2CR)4 paddlewheel unit;
b) the 4-connected ligand (L110) connecting to four Cu
wheel units.
2ACHTUNGTRNEN(UNG O2CR)4 paddle-
Figure 2. a) Chemical structure diagrams for H4L102 (H4qptc), H4L110 and H4L111; b) space-filling views along the crystallographic c axis and c) a axis for
NOTT-102, NOTT-110 and NOTT-111.
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Hydrogen Adsorption in Metal–Organic Frameworks
FULL PAPER
or b axes (Figure 2c). Although it is difficult to derive relia-
ble estimates of pore size from the crystal structure because
of disorder in the structure, pore size distribution analysis
from N2 isotherms of the desolvated materials at 78 K sug-
gest that the pore size of these two materials decreases
slightly on introduction of the phenanthrene and dihydro-
phenanthrene groups. In the isolated crystals, the solvent
molecules are disordered within the pores and their contri-
butions to the single-crystal X-ray diffraction patterns were
removed by applying PLATON/SQUEEZE.[16] The total ac-
cessible free volumes in the desolvated structures were thus
estimated to be 73% for both NOTT-110 and NOTT-111.
Importantly, powder XRD confirms the phase purity of bulk
samples (see the Supporting Information).
The solvent molecules (DMF and water) in these CuII
complexes can be exchanged for acetone or removed by
heating at 2008C under a flow of N2 gas or at 1008C under
vacuum. Compounds NOTT-110 and NOTT-111 show very
similar thermal behaviour as determined by thermogravi-
metric analysis (TGA). The blue-green crystalline samples
lose solvent rapidly between 25 and 1208C, resulting in the
formation of a deep purple-blue crystalline material.
To study the gas sorption isotherms of the evacuated
frameworks, the acetone-exchanged samples were loaded
into a Hiden Isochema IGA-003 instrument, and were de-
gassed at 1208C and 10À10 bar for 10 h to give fully desolvat-
ed NOTT-110 and NOTT-111. Isotherms for N2, H2 and D2
were measured at 78 K. Both N2 isotherms show typical
type I adsorption behaviour, which confirms the retention of
the microporous structures after the removal of solvents
from the crystalline samples (Figure 3a). The BET surface
areas for the desolvated complexes NOTT-110 and NOTT-
111 were estimated to be 2960 and 2930 m2 gÀ1, respectively,
compared with a value of 2942 m2 gÀ1 for NOTT-102. Al-
though the BET surface areas are almost the same for these
three related materials, the maximum N2 uptake increases
from 736 cm3 gÀ1 for NOTT-102, to 768 cm3 gÀ1 for NOTT-
111, and to 790 cm3 gÀ1 for NOTT-110. Dubinin–Astakhov
analysis of the isotherm data indicates that the pore sizes in
the desolvated NOTT-110 and NOTT-111 are the same, dis-
tributed narrowly around 8.0 ꢁ, which is slightly lower than
that in NOTT-102 (8.3 ꢁ). The pore volumes calculated
from the maximum N2 adsorption are 1.22 and 1.19 cm3 gÀ1
for desolvated NOTT-110 and NOTT-111, respectively.
These data show that the three desolvated frameworks dis-
play similar adsorption behaviour towards N2, indicating
that expansion of the carbon backbone within the frame-
work does not significantly affect N2 adsorption.
Figure 3. a) N2 sorption isotherms; b) H2 sorption isotherms (inset shows
uptake at low loading) for NOTT-102, NOTT-110 and NOTT-111 at
78 K. *: NOTT-102 adsorption; *: NOTT-102 desorption; ~: NOTT-
110 adsorption; ~: NOTT-110 desorption; &: NOTT-111 adsorption; &:
NOTT-111 desorption.
served is due to H2 rather than other impurities. We ob-
tained values of 1.05–1.20 for the molar ratio of adsorbed
D2/H2 over the pressure range 0.1–8.0 bar at 78 K (see the
Supporting Information), entirely consistent with the values
(1.06–1.10) observed experimentally for adsorption on
metal–organic and porous carbon materials at 77 K.[17,18]
The H2 isotherms of desolvated NOTT-110 and NOTT-
111 confirm 2.64 and 2.56 wt% total uptake, respectively, at
1 bar and 78 K (Figure 3b), which are among the highest
values so far reported for coordination framework materi-
als,[2f] apart from PCN-12.[15b] These values are 18% higher
than that of NOTT-102 (2.24 wt%), although the N2 iso-
therm data yield similar BET surface areas and pore vol-
umes for all three desolvated frameworks. Of NOTT-100,
NOTT-101 and NOTT-102, compound NOTT-102 has the
largest pore volume and pore size, but the lowest H2 uptake
at 1 bar.[6] We conclude that a smaller pore size can increase
the affinity for H2 adsorption owing to the overlap of the
potential energy fields of the pore walls. Therefore, the
larger pore size of NOTT-102 reduces the adsorption affinity
and, thus, presents the lowest uptake at low loading. Howev-
er, we observed higher uptakes and affinities for H2 in
NOTT-110 and NOTT-111, although they exhibit a pore size
similar to that in NOTT-102. More interestingly, they have
Gravimetric H2 adsorption data were recorded over the
range 0–20 bar at 78 K. All data were corrected for the
buoyancy of the system, samples and absorbates (see the
Supporting Information). All H2 isotherms show good rever-
sibility and an absence of hysteresis. The H2 adsorption ki-
netic data confirm that equilibrium is achieved rapidly
within approximately 3 min of the isotherm pressure step.
Importantly and significantly, D2 isotherm experiments were
used to validate and confirm that the H2 adsorption ob-
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M. Schrçder, N. R. Champness et al.
even higher H2 uptake at low loading than NOTT-100,
which has the smallest pore size (6.5 ꢁ) in this series.[6]
Given that all three compounds (NOTT-102, NOTT-110 and
NOTT-111) have the same NbO topology and have chemi-
cally very similar internal surfaces comprising binuclear Cu–
carboxylate nodes and aryl groups, the implication of the ad-
sorption results presented herein is that the extra molecular
surface area introduced by phenanthrene and hydrophenan-
threne groups promotes higher affinity between H2 mole-
cules and the framework. However, even with similarly high
H2 uptake at high pressure, the ZnII-based materials give a
lower uptake at 1.0 bar (MOF-177 1.25 wt%;[3] MOF-5
1.32 wt%[7]) than the CuII-based materials NOTT-110 and
NOTT-111, indicating that the latter CuII structures can pro-
vide stronger affinity for H2 at low pressure, as well as high
H2 storage capacity at high pressure. This suggests that CuII
materials are possibly better candidates for high H2 storage
capacities for low-pressure applications.
sults are consistent with each other. Langmuir–Freundlich
analysis of the isotherms for NOTT-102, NOTT-110 and
NOTT-111 shows that they have almost the same maximum
total H2 storage capacities of 8.5 wt% (see the Supporting
Information). Interestingly, significant enhancement of H2
adsorptions was observed in the low- to medium-pressure
range (0–20 bar). At 20 bar, the total H2 uptakes for NOTT-
110 and NOTT-111 were 6.59 and 6.48 wt%, respectively,
which was approximately 8% higher than the capacity of
NOTT-102 (Figure 4b), but lower than the maximum im-
provement of 18% observed at 1 bar. This is physically sen-
sible because the maximum uptake is limited by the total
pore volume, which is very similar in all three materials,
whereas adsorption at lower pressures is dominated by the
adsorbate–adsorbent interactions, which are closely related
and controlled by the surface chemistry of the pores. Thus,
introducing the phenanthrene and 9,10-hydrophenanthrene
groups has proven to be a successful mechanism to enhance
H2 uptake at low pressures without reducing the total
uptake of H2.
Compounds NOTT-110 and NOTT-111 not only show ex-
cellent H2 storage capacity on a gravimetric basis, but their
storage capacities on a volumetric basis (46.8 gLÀ1 for
NOTT-110 at 55 bar and 45.4 gLÀ1 for NOTT-111 at 48 bar)
are also among the highest reported for coordination frame-
work materials (Figure 4b).[3,4,7] The maximum volumetric
H2 uptakes predicted by fitting the total uptake data to the
Langmuir–Freundlich equation are 52.2 and 52.8 gLÀ1 for
NOTT-110 and NOTT-111, respectively. These values are
comparable to that of MOF-177 (48.3 gLÀ1 at 70 bar), al-
though the gravimetric uptakes are significantly lower than
for MOF-177 (11.3 wt%).[3] This mainly arises because of
the low density of the ZnII-based material (0.427 gcmÀ3 for
MOF-177),[4] which indicates that a highly porous material,
even one with ultrahigh gravimetric storage capacity, may
not necessarily be an optimum volumetric H2 storage mate-
rial. Recently, Long et al. reported a high-pressure H2 ad-
sorption study on air-free synthesised MOF-5.[7] Interestingly
and importantly, compared with the in-air synthesised
MOF-5, the total H2 uptake significantly improves from 7.0
to 9.0 wt% at 50 bar. On a volumetric basis, NOTT-110 and
NOTT-111 are still lower than the air-free synthesised
MOF-5 (58.4 gLÀ1), but they show better H2 storage poten-
tial in the low-pressure region (<10 bar) than MOF-5 (Fig-
ure 4b), indicating stronger affinities of H2 for the frame-
work core in NOTT-110 and NOTT-111. The densities of
the adsorbed H2 at 50 bar with respect to pore volume, as
determined from H2 isotherms assuming no distortion of the
framework structure under pressure, were measured as
0.0621 and 0.0616 gcmÀ3 for NOTT-110 and NOTT-111, re-
spectively, which are close to the density of liquid H2
(0.0708 gcmÀ3) at its boiling point, suggesting that the ad-
sorbed H2 is highly compressed. These data are lower than
the values (0.0762 gcmÀ3) of coordination frameworks with
small pores.[8b]
High-pressure volumetric H2 adsorption measurements at
77 K confirm that NOTT-110 and NOTT-111 achieve excess
H2 adsorption of 5.43 and 5.47 wt%, respectively, converting
to total uptakes of 7.62 and 7.36 wt% at 55 and 48 bar, re-
spectively (Figure 4a), higher than for NOTT-102. Up to
20 bar, both volumetric and gravimetric measurement re-
Figure 4. a) High-pressure H2 adsorption isotherms for NOTT-110 and
NOTT-111 at 77 K. &: excess NOTT-110; c: total NOTT-110; ~:
excess NOTT-111; c: total NOTT-111; b) volumetric H2 adsorption
isotherms for NOTT-110 (~), NOTT-111 (&), MOF-177 (!)[3] and
An alternative view of the structures of NOTT-110 and
NOTT-111 provides a valuable interpretation of the H2 ad-
[7]
^
MOF-5 ( ) at 77 K (inset shows uptake at low loading).
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Hydrogen Adsorption in Metal–Organic Frameworks
FULL PAPER
sorption by these materials. Analysis of the crystal structures
reveals that the structures are composed of alternate link-
ACHTUNGTRENNUNGages between two types of copper–ligand cages, [Cu24(L)6]
4À
4À
and [Cu12(L)12] in which L is either [L110
(Figure 5). Each [Cu24(L)6] cage consists of twelve [Cu2-
(O2CR)4] units and six ligands, whereas each [Cu12(L)12]
]
or [L111
]
ACHTUNGTRENNUNG
cage comprises six copper paddlewheel units and twelve li-
gands. The [Cu24(L)6] cage is highly elongated with an ellip-
tical cavity of about 34ꢂ10ꢂ10 ꢁ, whereas the [Cu12(L)12]
cage has a more spherical cavity of approximately 18ꢂ11ꢂ
11 ꢁ. These two types of cages of D3h symmetry are alter-
nately linked and Figure 5 illustrates that the phenanthrene
and 9,10-hydrophenanthrene groups cover more cage sur-
face than the biphenyl groups in NOTT-102, making the
cages more compact in NOTT-110 and NOTT-111. Given
that introduction of these groups does not significantly
affect the pore size and volume in the three desolvated
frameworks, but does apparently enhance the uptake of and
affinity for H2, a new strategy for delivering higher adsorp-
tion capacities can be defined, based on coordination frame-
work materials incorporating compact cages.
One would anticipate that higher uptakes at low pressures
would be linked to higher isosteric heats of adsorption. To
gain insight into the mechanism of uptake enhancement, the
H2 adsorption isotherms were also measured at 88 K and
isosteric heats of adsorption (Qst) were determined by fitting
a virial-type equation to both the 78 and 88 K H2 adsorption
isotherm data (Figure 6).[5,17,19] The virial analysis shows that
the isosteric heats of adsorption exhibit maxima at 5.70, 5.68
Figure 6. Isosteric heat of H2 adsorption for NOTT-102 (c), NOTT-110
(c) and NOTT-111 (c).
and 6.21 kJmolÀ1 (error ~0.1 kJ) at zero surface coverage
for NOTT-102, NOTT-110 and NOTT-111, respectively, and
decrease with increasing H2 loading. NOTT-110 and NOTT-
111 display quite different behaviour in their adsorption en-
thalpies. The isosteric heat for NOTT-110 is similar to
NOTT-102, whereas NOTT-111 is ~1.0 kJmolÀ1 higher than
the others at all of the measured loadings, which means that
higher uptake capacities may not necessarily be related to
higher heats of adsorption. The 9,10-hydrophenanthrene
substituent is slightly bulkier than the phenanthrene group,
and the consequent loss of planarity, as well as the noncon-
jugated surface, may provide stronger binding sites by pro-
viding a pocket for adsorption
(Figure 5). This, therefore, rep-
resents a new protocol for pro-
viding stronger overall binding
sites in coordination frame-
work materials by hydrogena-
tion of the ligand to afford a
partially nonconjugated sur-
face.
Conclusion
We have synthesised and char-
acterised two new CuII-based
coordination
frameworks,
NOTT-110 and NOTT-111. In-
corporation of phenanthrene
and 9,10-dihydrophenanthrene
groups into the frameworks
leads to enhancements to both
H2 adsorption capacity com-
pared with the parent tetra-
phenyl NOTT-102 analogue,
and this can be attributed to
the changes in the cage surface
structure. Exceptionally high
total H2 storage capacities of
Figure 5. ACHTUNGTRENNUNG[Cu24L6] and [Cu12L12] cages in NOTT-102, NOTT-110 and NOTT-111. The phenanthrene and dihy-
drophenanthrene groups in NOTT-110 and NOTT-111, respectively, are highlighted by using a space-filling
style.
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M. Schrçder, N. R. Champness et al.
Crystal data for NOTT-110: [Cu
blue-green block; 0.08ꢂ0.08ꢂ0.04 mm; R3m; a=b=18.3411(4), c=
52.6041(15) ꢁ; V=15325.0 (6) ꢁ3; Z=9; 1calcd =1.271 gcmÀ3
m=
0.698 mmÀ1; F
(000)=6174/39972 total reflections/3311 unique reflections;
2CATHGNUNERTNU(NG C30H14O8)ACHTUNEGTR(GNUNN H2O)2] (C3H7NO)7.5ACHTUNGTRENNUNG(H2O)5;
7.62 wt% at 55 bar and 77 K have been observed in NOTT-
110, with volumetric capacities for NOTT-110 and NOTT-
111 of 46.8 and 45.4 gLÀ1, respectively. It is reasonable to
anticipate the discovery of new materials with enhanced H2
storage performance, and we are currently undertaking the
challenge of deploying ligand decoration for the synthesis of
new coordination frameworks with higher H2 storage capaci-
ty.
¯
;
AHCTUNGTRENNUNG
with Rint =0.139; final R1 (wR2)=0.085 (0.237); GOOF=1.035. The final
difference Fourier extrema were 0.78 and À0.68 eꢁÀ3
.
Crystal data for NOTT-111: [Cu2ACHTUNGTREN(NNGU C30H16O8)AHCUTNRTGE(NGNUN H2O)2] (C3H7NO)7.5ACHTUNGTRENNUNG(H2O)5;
¯
blue-green block; 0.10ꢂ0.08ꢂ0.04 mm; R3m; a=b=18.3555(4), c=
52.4245(16) ꢁ; V=15296.7(7) ꢁ3; Z=9; 1calcd =1.276 gcmÀ3
m=
0.700 mmÀ1; F
(000)=6192/35275 total reflections/3674 unique reflections;
;
AHCTUNGTRENNUNG
R
int =0.113; final R1 (wR2)=0.088 (0.233); GOOF=1.058. The final dif-
ference Fourier extrema were 0.51 and À0.26 eꢁÀ3
.
Adsorption isotherms (0–20 bar) were measured by using a Hiden Iso-
chema Intelligent Gravimetric Analyser, which is an ultrahigh vacuum
(1ꢂ10À10 bar), clean system with a diaphragm and turbo pumping system.
In a typical procedure, 50–100 mg dry sample were used for the measure-
ment. Hydrogen and deuterium were purified by using calcium alumino-
silicate and activated carbon adsorbents to remove trace amounts of
water and other impurities. Volumetric H2 sorption measurements were
performed over a pressure range of 0–60 bar by using an automatically
controlled Sievertsꢃ apparatus (PCT-Pro 2000 from Hy-Energy LLC). All
measurements were made with ultrahigh purity grade (99.999%) H2 and
He (See the Supporting Information). CCDC-700860 and 700861 contain
the supplementary crystallographic data for complexes NOTT-110 and
NOTT-111, respectively. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
Experimental Section
Ligand syntheses: The ligands H4L110 and H4L111 were synthesised by
using similar experimental procedures. The synthesis of H4L110 is de-
scribed herein: 2,7-dibromo-phenathrene (0.34 g, 1.0 mmol), diethylisoph-
thalate-5-boronic acid (0.64 g, 2.4 mmol) and K3PO4 (1.05 g, 5.0 mmol)
were mixed in 1,4-dioxane (40 mL), and the mixture was deaerated by
using argon gas for 20 min. [PdACHTNUGTRNEUG(N PPh3)4] (0.05 g, 0.022 mmol) was added
to the reaction mixture with stirring and the mixture was heated to 858C
for 3 days under argon. The resultant mixture was isolated by conven-
tional extraction procedures. The final product H4L110 was obtained by
hydrolysing the crude product with 2m aqueous NaOH, followed by
1
acidification with concentrated HCl (0.44 g, 87%). H NMR ([D6]DMSO,
300 MHz): d=9.05 (d, J=9 Hz; 2H), 8.65ACTHUNTGRNEUNG(s; 4H), 8.56 (s; 2H), 8.51 (s;
2H), 8.17 (d, J=9 Hz; 2H), 8.13 (s; 2H); elemental analyses calcd (%)
for C30O8H18: C 71.15, H: 3.58; found: C 71.14, H 3.63.
H4L111 1H NMR ([D6]DMSO, 300 MHz): d=8.49 (m; 6H), 8.06 (d, J=
:
9 Hz; 2H), 7.75 (m; 4H), 3.03 ppm (s; 4H); elemental analysis calcd (%)
for C30O8H20: C 70.86, H 3.96; found: C 71.38, H 3.97.
Acknowledgements
We thank the EPSRC and the University of Nottingham for support and
funding. We are grateful to the EPSRC-funded National Crystallography
Service at the University of Southampton for data collection. M.S. grate-
fully acknowledges receipt of a Royal Society Wolfson Merit Award and
of a Royal Society Leverhulme Trust Senior Research Fellowship. S.Y.
thanks Shell and the EPSRC for DHPA funding.
Metal complex syntheses: Analogous experimental procedures were em-
ployed for the syntheses of NOTT-110 and NOTT-111, and the details for
compound NOTT-110 are described herein: H4L110 (0.10 g, 0.20 mmol)
and CuACHTUNGTRENNUNG(NO3)2·2.5H2O (0.11 g, 0.60 mmol) were mixed and dispersed in
DMF/1,4-dioxane/H2O (50 mL, 3:1:1 v/v/v). The resulting blue-green
slurry turned clear upon addition of three drops of concentrated HCl. It
was found that acidic reaction solutions afforded more highly crystalline
products. The solution was heated to 908C for 20 h. The blue-green crys-
talline product was washed sequentially with DMF, and dried briefly in
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:
Compound NOTT-111: IRACTHNUTRGENUG(N KBr): n˜ =2930 (w), 1654 (vs), 1587 (m), 1492
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tensities. The final formulae were calculated from the SQUEEZE results
combined with elemental analysis data.
4834
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Chem. Eur. J. 2009, 15, 4829 – 4835

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Received: November 5, 2008
Published online: March 23, 2009
Chem. Eur. J. 2009, 15, 4829 – 4835
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4835