Metal-organic framework materials with ultrahigh surface areas: Is the sky the limit?

Article abstract of DOI:10.1021/ja3055639

We have synthesized, characterized, and computationally simulated/validated the behavior of two new metal-organic framework (MOF) materials displaying the highest experimental Brunauer-Emmett-Teller (BET) surface areas of any porous materials reported to

Full text of DOI:10.1021/ja3055639

Subscriber access provided by University Libraries, University of Memphis
Article
Metal-organic Framework Materials with
Ultrahigh Surface Areas: Is the Sky the Limit?
Omar K. Farha, Ibrahim Eryazici, Nak Cheon Jeong, Brad G Hauser, Christopher E Wilmer, Amy
A. Sarjeant, Randall Q. Snurr, SonBinh T. Nguyen, Ahmet Özgür Yazaydin, and Joseph T. Hupp
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/ja3055639 • Publication Date (Web): 20 Aug 2012
Downloaded from http://pubs.acs.org on August 23, 2012
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Journal of the American Chemical Society is published by the American Chemical
Society. 1155 Sixteenth Street N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 7
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
Metal-organic Framework Materials with Ultrahigh Surface Areas:
Is the Sky the Limit?
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Omar K. Farha,1,‡,* Ibrahim Eryazici,1,‡ Nak Cheon Jeong,1 Brad G. Hauser,1 Christopher E. Wilmer,2
Amy A. Sarjeant,1 Randall Q. Snurr,2 SonBinh T. Nguyen,1 A. Özgür Yazaydın,3,* Joseph T. Hupp1,*
1 Department of Chemistry and International Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road,
Evanston, Illinois 60208ꢀ3113. 2 Department of Chemical & Biological Engineering, Northwestern University, 2145 Sheriꢀ
dan Road, Evanston, Illinois 60208, USA. 3 Department of Chemical Engineering, University of Surrey, Guildford, GU2
7XH, United Kingdom.
Supporting Information Placeholder
ABSTRACT: We have synthesized, characterized, and computationally simulated/validated the behavior of two new metalꢀorganic
framework (MOF) materials displaying the highest experimental BrunauerꢀEmmettꢀTeller (BET) surface areas of any porous mateꢀ
rials reported to date (~7,000 m2/g). Key to evacuating the initially solventꢀfilled materials without pore collapse, and thereby acꢀ
cessing the ultraꢀhigh areas is the use of a supercritical CO2 activation technique. Additionally, we demonstrate computationally
that by shifting from phenyl groups to "space efficient" acetylene species as linker expansion units, the hypothetical maximum surꢀ
face area for a MOF material is substantially greater than previously envisioned (~14,600 m2/g (or greater) versus ~10,500 m2/g).
Introduction
One of the first breakthroughs in obtaining MOFs with perꢀ
manent microporosity came in 1998 from Li et al., who deꢀ
scribed a material having a Langmuir surface area of 310
m2/g.20 Striking increases in reported surface areas for MOFs
followed for the next several years, with values reaching 3,800
m2/g in 200521 and a remarkable 5,200 m2/g in 2009.22 Among
the reported highꢀarea materials were MOF-523,24(especially in
anhydrous form25), MOF-177,25,26 MIL-101,21 UMCM-1,27
and UMCM-222 (Table 1). Efforts to achieve even higher
surface areas appeared to stall – not primarily because of diffiꢀ
culty in synthesizing new candidate materials, but because of
the progressively greater tendency of these materials to colꢀ
lapse upon removal of solvent. Fortunately, a MOF activation
method recently introduced by our lab28,29 and based on superꢀ
critical carbon dioxide (see below) has enabled difficultꢀtoꢀ
activate, largeꢀcavity MOFs to be evacuated without frameꢀ
work collapse or channel blockage. Based on this advance,
two MOFs with experimentally accessible BET surface areas
slightly above 6,000 m2/g have been reported: MOF-21030
and NU-10031 (NU = Northwestern University; NU-100 is also
known as PCN-61032).
Extensive research over the past few years has been focused
on the synthesis and characterization of microporous materials
with high internal surface areas. MetalꢀOrganic Frameworks
(MOFs),1ꢀ3 a crystalline subset of these materials, have shown
promise in a wide range of applications from gas storage,4ꢀ6
chemical separations,7ꢀ10 chemical sensing,11 and catalysis,12ꢀ14
to ion exchange,15 light harvesting,16,17 and drug delivery.18,19
High internal surface area is one of the foremost attributes of
MOFs and has been shown to be highly desirable in many
potential applications involving catalysis or storage. (Particuꢀ
larly relevant is the sorptionꢀbased storage of technologically
important gases at temperatures above their respective critical
temperatures. For example, at T > 191 K methane cannot
form methane/methane multiꢀlayers; thermodynamically exꢀ
cess adsorption, therefore, can be achieved only via direct
contact between individual methane molecules and the sorbent
surface.)
Additionally fueling interest in MOFs is their extraordinary
compositional and structural variety (e.g., ca. 10,000 experiꢀ
mentally known MOFs versus fewer than 300 zeolites) and the
fact that many display permanent porosity, ultraꢀlow densities,
and wellꢀdefined pores and channels. Further, the crystallinity
of MOFs allows for their unambiguous structural characterizaꢀ
tion by Xꢀray diffraction, greatly simplifying efforts to use
computational modeling to predict or explain their unusual or
unique physical properties. In this report, we have synthesized
and characterized two new MOFs that display the highest exꢀ
perimental BrunauerꢀEmmettꢀTeller (BET) surface areas to
date (~7,000 m2/g). Additionally, we demonstrate computaꢀ
tionally a new surface area ceiling for MOFs (~14,600 m2/g)
that substantially exceeds what much of the MOF community
perceives to be a theoretical upper limit (~10,500 m2/g).
Results and Discussion
Many researchers believe that the recordꢀhigh surface areas for
NU-10031 and MOF-21030 are “close to the ultimate [experiꢀ
mental] limit for solid materials.”33 This belief no doubt stems
from: a) simulations showing that the upper theoretical limit
for MOF surface areas is about 10,500 cm2/g when linkers are
constructed from repeating phenyl groups,25,34 and b) anticiꢀ
pated practical problems, such as poor solubility, low synthetic
yields, and cumbersome purification protocols, for candidate
linkers featuring very large numbers of phenyl repeat units.
We reasoned, however, that both the experimental maximum
and the perceived theoretical ceiling could be substantially
increased by moving beyond phenylꢀonly struts to more “areaꢀ
ACS Paragon Plus Environment

Journal of the American Chemical Society
efficient” building blocks for MOF linkers. A recent prelimiꢀ
Page 2 of 7
1
2
nary report from our labs provides qualitative support for this
notion.35
3
4
5
6
7
8
9
Table 1. BET surface areas and pore volumes for highly
porous MOFs.
BET surface
area (m2 g-1)
Pore vol-
MOF
Ref.
ume (cm3 g-
1
MFU-4l
NOTT-102
PCN-61
2750
2940
3000
3160
3670
3800
3800
3920
4000
4030
4160
4230
4300
4460
4750
4850
4660/5110
5200
6140
6240
7010
7140
1.26
36
37
38
39
40
41
24
42
38
43
27
21
44
30
26
45
32,46
22
1.14
1.36
1.27
1.52
1.62
1.55
ꢀ
1.36
ꢀ
ꢀ
2.15
4.30
2.16
1.59
2.03
2.17
2.32
2.82
3.6
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Cu24(TPBTM)8(H2O)24
SNU-77
NOTT-112
MOF-5
UMCM-1-NH2
PCN-66
Be12(OH)12(BTB)24
UMCM-1
MIL-101c
Bio-MOF-100
MOF-205
MOF-177
DUT-23-Co
NOTT-116/PCN-68
UMCM-2
NU-100
MOF-210
NU-109E
NU-110E
31
30
Herein
Herein
3.75
4.40
We thus turned our attention to (3,24)ꢀpaddlewheel conꢀ
nected MOF networks (rht-topology), pioneered by the Edꢀ
daoudi group47 and significantly further explored by us,31,48
Zhou and coꢀworkers32 and Schroeder and coꢀworkers.41
A
key feature of the rht-topology is that catenation (interpenetraꢀ
tion or interweaving of multiple frameworks) is mathematicalꢀ
ly precluded.49,50 Capitalizing on this topology, we syntheꢀ
sized two new materials with ultraꢀhigh surface areas, NU-109
and NU-110, from two new hexaꢀcarboxylated linkers. The
synthesis and characterization of the hexaꢀcarboxylicꢀacid
forms of the desired linkers (LH6-1 and LH6-2, Figures 1a and
1h, Scheme S1) are described in the Supporting Information
(SI). Briefly, LH6 species were obtained via saponification of
the corresponding hexaester precursors, which, in turn, were
obtained via Sonagashira coupling of 1,3,5ꢀtriiodobenzene
with the appropriate acetyleneꢀterminated compounds.
Solvothermal reactions of LH6-1 or LH6-2 and
.
Cu(NO3)2 2.5H2O in DMF/EtOH/HCl (DMF = dimethylforꢀ
mamide) at 75°C afforded MOFs having the framework forꢀ
mula [Cu3(L6-(109))(H2O)3]n (NU-109E, E = Experimental, L6-
= the hexaꢀanion of LH6-1) or [Cu3(L6-(110))(H2O)3]n (NU-
Figure 1. Structural features of NU-109 and NU-110. a, Schematic drawꢀ
(109)
ing of the chemical structure of LH6 for NU-109. b-g, Representations of
the singleꢀcrystal Xꢀray structure of NU-109 showing: LH6 connecting six
paddlewheel units (b), cubaoctahedral building blocks (c), and different
cages within NU-109 (d-g). h, Schematic drawing of the chemical strucꢀ
ture of LH6 for NU-110. i-m, Representations of the singleꢀcrystal Xꢀray
structure of NU-110 showing: LH6 connecting six paddlewheel units (i),
cubaoctahedral building blocks (j), and different cages in NU-110 (k-n).
Hydrogens and disordered solvent molecules are omitted for clarity.
Carbon = gray; oxygen = red; copper = teal. Purple spheres are included
to guide the eye in distinguishing between the three cages.
110E, L6-
= the hexaꢀanion of LH6-2) after 48 hours. Xꢀ
(110)
ray analysis of single crystals of NU-109E and NU-110E reꢀ
vealed nonꢀcatenated structures in which the framework nodes
consist of CuII2 units coordinated by the carboxylates of L6- in
a paddlewheel fashion. The axial sites of the CuII units are
2
coordinated by water molecules that were not well resolved in
the Xꢀray analysis (Figures 1b and 1i). The experimental
structures of NU-109E and NU-110E were found to be in exꢀ
cellent agreement with the predicted structures, NU-109SP
(SP = Simulation of the Predicted structure) and NU-110SP
(see SI for more details). The predicted and
ACS Paragon Plus Environment

Page 3 of 7
Journal of the American Chemical Society
experimental structures of both materials have a cubic space
ture) and NU-110SE to NU-100SE31 and NOTT-11646/PCN-
68,32 which likewise share the rhtꢀtopology. These patterns
(Figures 2d and 2e) show the lowest angle peak progressively
shifting to smaller 2θ, which corresponds to an increasing unit
cell length and therefore a larger distance between the copper
nodes, culminating with NU-110SE. Thermogravimetric
analysis (TGA) of NU-109E and NU-110E revealed in both
cases a mass loss at about 100°C, assigned to solvent (DMF),
with no further mass loss occurring until 325°C (Figure 2f).
Both MOFs contain more free solvent than either NU-
100E/PCN-610 or NOTT-116E/PCN-68E, pointing to the
potential for greater permanent porosity.
1
2
3
4
5
6
7
8
group, Fm m, with unitꢀcell dimensions of a = b = c = 65.899
3
Å (NU-109SP at 0 K), 64.528 Å (NU-109E at 100 K), 70.330
Å (NU-110SP at 0 K), and 68.706 Å (NU-110E at 297 K).
The differences in the unit cells between the experimental and
simulated structures are only 1.37 Å and 1.62 Å for NU-109
and NU-110, respectively. The experimental structures were
solved, in part, by utilizing the coordinates of the in silico
structures predicted by using molecular modeling techniques.
9
NU-109 and NU-110 share several topological features.
Briefly, each L6- unit contributes to the formation of three
cuboctahedron cages (Figures 1c and 1j). Both contain three
types of cages (Figures 1g and 1n, Figure S19) that are fused
in ways that provide for continuous channels. Cuboctahedral
cage 1 (Figures 1d and 1k) is formed from 24 isophthalate
groups from L6- units and 12 pairs of copper ions (i.e., 24 toꢀ
tal). The nodes forming triangular windows in cage 1 are
shared with cage 2 (Figures 1e and 1l), while those forming
rectangular windows are shared with cage 3 (Figures 1f and
1m). Cage 2 (Figures 1e and 1l) defines a truncated tetraheꢀ
dron, and is formed from isophthalate groups from four L6-
linkers and 12 pairs of copper ions (i.e., 24 total). As exꢀ
pected, cage 3 (Figure 1f and 1m) is describable as a truncated
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Regardless of how striking the NU-109E and NU-110E
structures may be, for many applications–especially those
centering on storage and separation–removal of guest solvent
molecules from the pores without significantly diminishing
porosity is crucial. Failure to prevent porosity loss will result
in significant discrepancies between the surface areas obtained
experimentally and those estimated from computational modꢀ
eling. Since MOFs containing large pores such as NU-109
and NU-110 are particularly predisposed to collapse, we emꢀ
ployed an unconventional MOF activation strategy recently
developed by our team28,29 and now used by MOF researchers
throughout the world (e.g., Kaskel,45 Yaghi,30,51 Hong52 and
others) to activate them. The activation takes advantage of
supercritical carbon dioxide (SCD) processing, which was
performed with a Tousimis™ Samdri® PVTꢀ30 critical point
dryer. Prior to drying, DMF/EtOHꢀsolvated MOF samples
were soaked in 100% ethanol, replacing the soaking solution
every day for 3 days. The ethanolꢀcontaining samples were
placed inside the dryer and the ethanol was exchanged with
CO2 (liq.) over a period of 10 h. The temperature was then
raised and CO2 was vented under supercritical conditions
where capillary forces and solvent surfaceꢀtension are inherꢀ
ently absent (see SI for more details).
II
cuboctahedron and is formed by 24 Cu2 paddlewheel nodes
and portions of eight distinct L6- units.
The phase purity of bulk samples of NU-109 and NU-110
was confirmed via powder Xꢀray diffraction (PXRD) measꢀ
urements (Figures 2a and 2b). Additionally, the simulated
PXRD patterns from experimental and predicted structures are
in excellent agreement (Figure 2c). This confirms that, apart
from minor differences in unit cell dimensions, the predicted
structures are identical to the experimentally obtained materiꢀ
als. These differences are tentatively ascribed to the differꢀ
ence between experimental (i.e., Xꢀray collection) and simulaꢀ
tion temperatures. Furthermore, we compared the PXRD patꢀ
terns of NU-109SE (SE = Simulated from Experimental strucꢀ
Figure 2. TGA and PXRD profiles. a-c, PXRD patterns of NU-109 and NU-110. d-e, PXRD patterns of NU-109, NU-110, NU-100,31 and NOTT-
11646/PCN-68.32 f, TGA profiles of NU-109, NU-110, NU-100,31 and NOTT-11646/PCN-68.32
The porosities of SCDꢀactivated NU-109 and NU-110 were
examined via nitrogen adsorption at 77 K. N2 isotherms
showed extraordinarily high limiting uptakes of 2480 and
2845 cm3/g for NU-109E and NU-110E, respectively (Figure
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 4 of 7
3). The experimental BET surface areas of activated NU-
material. Chae at al.25 described a useful conceptual basis for a
109E and NU-110E were found to be 7010 and 7140 m2/g, in
excellent agreement with the fitted (in silico) BET surface
areas for NU-109SE (6950 m2/g) and NU-110SE (7400 m2/g)
and with the simulated BET surface area for NU-109SP (7560
m2/g) and NU-110SP (7800 m2/g) (Table 2). The deviation in
surface areas between the SE and SP materials reflect the
small, but finite, differences in dimensions of the experimental
versus calculated unit cells. Nonetheless, these surface areas
are the highest for any porous materials reported to date.
Moreover, the total pore volumes of NU-109E and NU-110E
are 3.75 and 4.40 cm3/g, which are substantially larger than
any other highꢀporeꢀvolume MOFs (see Table 1). Finally, the
observed void volumes of ca. 93% (for each) exceed those for
any other solventꢀevacuated MOF material described to date.
It is worth noting that the nitrogen isotherms shown in Figure
3 are typeꢀIV rather than typeꢀI, reflecting the fact that both
NU-109 and NU-110 contain multiple types (sizes) of pores.
The simulated isotherms show three distinct regions, while the
experimental data do not resolve these as clearly. However,
the simulated and experimental pore size distributions are in
excellent agreement as shown in Figures S30 and S32. Addiꢀ
tionally, PXRD patterns for asꢀsynthesized, activated and reꢀ
solvated NU-109 and NU-100 show no evidence for structural
changes during activation and porosity measurements.
strategy to achieve highꢀsurfaceꢀarea ordered materials. By
progressively excising smaller fragments from an infinite graꢀ
phene sheet and calculating Connolly53 surface areas of the
remaining framework, they found that exposing all latent edgꢀ
es to give isolated sixꢀmembered rings would yield a surface
area of 7,745 m2/g. The exposed sixꢀmembered rings were
essentially benzene molecules without hydrogens, whose inꢀ
clusion would have given an even higher surface area. By
putting this strategy into practice, they synthesized MOF-177
from Zn4O clusters and 1,3,5ꢀbenzenetribenzoate (BTB) orꢀ
ganic linkers, which showed a recordꢀbreaking surface area at
that time (4,750 cm2/g). (Subsequently, it was realized that for
sorption applications, moleculeꢀaccessible surface areas are
physically more meaningful than Connolly surface areas.54
Additionally, Snurr and coꢀworkers showed that, subject to
well defined “consistency criteria”, experimental BET surface
areas for fully evacuated MOFs (but not Langmuir or Connolꢀ
ly surface areas) correspond closely to moleculeꢀaccessible
surface areas.54)
In a related approach, Schnobrich et al.34 constructed a seꢀ
ries of structures (in silico) by incrementally adding benzenes
to the linker of MOF-5 (1,4ꢀterephthalic acid). This study
revealed that a MOF-5 analogue with an infinite number of
benzenes in its linker would give an N2ꢀaccessible surface area
of 10,436 m2/g, which is very close to the maximum attainable
surface area (10,577 m2/g) for structures derived from benzene
rings regardless of their topology. These studies have, until
now, largely defined surfaceꢀarea targets for MOF materials
for both experimental and theoretical investigations, and the
use of benzene chains of different forms and lengths has beꢀ
come a common way of synthesizing materials with high surꢀ
face areas.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Table 2. Experimental and simulated surface areas and
pore volumes for NU-109, NU-110, NU-109SP, and NU-
110SP.
BET surface
area (m2 g-1)
Pore volume
(cm3 g-1)
MOF
NU-109SP
NU-109SE
NU-109E
NU-110SP
NU-110SE
NU-110E
7560
6950
7010±80
7800
7400
7140
4.12
3.90
3.75
4.44
4.18
4.40
Here we propose and demonstrate that there are routes to atꢀ
taining MOFs with even higher surface areas. The basis of one
of these routes relies on further exposing the edges of a sixꢀ
membered carbon ring by dividing it into three separate but
chemically linked pieces, where each consists of two carbon
atoms linked by a triple bond. These pieces are roughly equivꢀ
alent to acetylenes, but with carbonꢀcarbon single bonds to
neighboring pieces replacing terminal hydrogen atoms. Emꢀ
ploying three linked acetylenes in place of a single benzene
ring in a material should result in a significantly higher moleꢀ
culeꢀaccessible surface area, since larger numbers of exposed
edges (i.e., adsorption sites) are presented.54 We hypothesized
that stepwise addition of acetylenes to the linker of a MOF
would yield, substantially higher gravimetric surface than
would the stepwise addition of benzene units (for comparisons
at the same unit cell size).
SP = Simulated of Predicted structure
= Simulated of Experimental structure
= Experimental results
SE
E
3,000
2,500
2,000
1,500
1,000
500
NU-110
NU-109
To test the hypothesis, we constructed three series of hypoꢀ
thetical MOFs based on (3,24)ꢀpaddlewheel connected netꢀ
works. (Recall that these networks, in contrast to that for, say,
MOF-5, cannot form interpenetrated structures–an important
practical consideration, as catenation can otherwise present a
major experimental obstacle to obtaining high surface area
materials. For example, a family of highly catenated (ca. 12ꢀ
fold) terpyridineꢀbased coordination polymers recently deꢀ
scribed by our labs, exhibits surface areas of a few to several
hundred m2/g;55 however, the polymers would be expected to
yield surface areas higher than 6,400 m2/g if they could ever
be prepared in singleꢀnetwork form.) The desired hypothetical
structures were constructed by incrementally adding: a) pheꢀ
0
0.00
0.20
0.40
0.60
Pressure (P/P0)
Figure 3. Sorption data for NU-109E and NU-110E. Experimental nitroꢀ
gen isotherms for NU-109E (red squares) and NU-110E (blue circles).
While the BET surface areas of the new MOFs are large
(nearly 70% of the theoretical maximum for materials with
benzeneꢀderived linkers), can higher surface area materials be
experimentally obtained? Attempts have been made previousꢀ
ly to calculate the highest possible surface area for a porous
ACS Paragon Plus Environment

Page 5 of 7
Journal of the American Chemical Society
II
and simulated BET surface area analyses of MOFs NU-109E and
nyl, b) phenylethynyl, or c) ethynyl groups to the Cu2 ꢀ
1
2
3
4
5
6
7
8
NU-110E; details of molecular simulations and geometric surface
area calculation of A, B, and C MOF series. This material is
available free of charge via the Internet at http://pubs.acs.org.”
paddlewheel clusters until their unitꢀcell edge lengths reached
at least 300 Å (Figure 4). For each series, we then calculated
accessible surface areas and plotted them against the unitꢀcell
lengths; as anticipated, the areas become progressively larger
as the cell lengths increases. Upper limit surface areas were
determined by implementing a highꢀquality fitting that enꢀ
tailed the use of a fiveꢀparameter “exponential rise to max”
equation (see SI for details). When only phenyl units were
used in the linkers (case a), the upper limit for the gravimetric
surface area was found to be 9950 m2/g, which is only slightly
lower than the theoretical limit reported for MOFs derived
from benzeneꢀcontaining struts.25,34 When phenylethynyl
groups were used (case b), we found that the upper limit of the
gravimetric surface area increased to a value of 12,250 m2/g.
Finally and most excitingly, the use of only ethynyl units in
the linker extensions (case c) resulted in an upper limit of
14,600 m2/g.
AUTHOR INFORMATION
Corresponding Authors
* o-farha@northwestern.edu, a.yazaydin@surrey.ac.uk, and
j-hupp@northwestern.edu
9
Author Contributions
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
‡These authors contributed equally.
The manuscript was written through contributions of all authors.
All authors have given approval to the final version of the manuꢀ
script.
ACKNOWLEDGMENTS
JTH, STN, and RQS gratefully acknowledge the U. S. Dept. of
Energy’s Office of Energy Efficiency and Renewable Energy for
primary financial support. IE is supported by NSF grant # EECꢀ
0647560 administered through the Northwestern NSEC, which
also provides additional general support on MOF design and synꢀ
thesis. AÖY thanks the European Commission Marie Curie Inꢀ
ternational Reintegration for financial support. STN acknowledgꢀ
es additional financial support from the AFOSR. The Cambridge
Crystallographic Data Centre deposition numbers for NU-109 and
NU-110 are CCDC 856012 and 856013, respectively.
REFERENCES
Figure 4. Estimated accessible surface areas of MOFs with rhtꢀtopology
constructed by LH6 ligands consisting of linkers A, B, and C, where the
center benzene of the ligand was extended by addition of increasing numꢀ
ber (n) of phenyl, phenylethynyl, and ethynyl moieties, respectively. For
the longest unit cell edge lengths (~310 Å) n is 26, 15, and 40 for A, B,
and C, respectively.
(1)
O'Keeffe, M.; Peskov, M. A.; Ramsden, S. J.; Yaghi, O. M.
Acc. Chem. Res. 2008, 41, 1782.
(2)
Férey, G. Chem. Soc. Rev. 2008, 37, 191.
(3)
Horike, S.; Shimomura, S.; Kitagawa, S. Nature Chem. 2009,
1, 695.
(4)
Murray, L. J.; Dincă, M.; Long, J. R. Chem. Soc. Rev. 2009,
The computational modeling results clearly show that the
strategy of using progressively more acetylenes in the organic
linkers of MOFs, whether alone or with other molecular subꢀ
units, has the potential of creating ordered structures with surꢀ
face areas substantially higher than any previously envisioned
for metalꢀorganic framework materials. Importantly, it seems
reasonable to conclude that even the recordꢀhigh surface area
of 7,140 m2/g for NU-110 does not define the practical experꢀ
imental upper limit for surface areas of porous materials, as it
corresponds to only about 49% of the theoretical upper limit
for MOFs featuring acetyleneꢀrich linkers. Indeed, it is conꢀ
ceivable that other linker motifs–for example, ones based on
extended polyenes, or on connectingꢀatoms that are lighter
than carbon–could yield even higher computational ceilings
for surface areas.
38, 1294.
(5)
Hu, Y. H.; Zhang, L. Adv. Mater. 2010, 22, E117.
(6)
Sculley, J.; Yuan, D.; Zhou, H.ꢀC. Energy Environ. Sci. 2011,
4, 2721.
(7)
38, 1477.
(8)
38.
(9)
Li, J.ꢀR.; Kuppler, R. J.; Zhou, H.ꢀC. Chem. Soc. Rev. 2009,
An, J.; Geib, S. J.; Rosi, N. L. J. Am. Chem. Soc. 2010, 132,
Britt, D.; Furukawa, H.; Wang, B.; Glover, T. G.; Yaghi, O. M.
Proc. Natl. Acad. Sci. U. S. A. 2009, 106, 20637.
(10) Bae, Y.ꢀS.; Spokoyny, A. M.; Farha, O. K.; Snurr, R. Q.;
Hupp, J. T.; Mirkin, C. A. Chem. Commun. 2010, 46, 3478.
(11) Allendorf, M. D.; Bauer, C. A.; Bhakta, R. K.; Houk, R. J. T.
Chem. Soc. Rev. 2009, 38, 1330.
(12)
(13)
Ma, L.; Abney, C.; Lin, W. Chem. Soc. Rev. 2009, 38, 1248.
Lee, J.; Farha, O. K.; Roberts, J.; Scheidt, K. A.; Nguyen, S.
T.; Hupp, J. T. Chem. Soc. Rev. 2009, 38, 1450.
(14) Farha, O. K.; Shultz, A. M.; Sarjeant, A. A.; Nguyen, S. T.;
Hupp, J. T. J. Am. Chem. Soc. 2011, 133, 5652.
(15)
(16)
An, J.; Rosi, N. L. J. Am. Chem. Soc. 2010, 132, 5578.
Lee, C. Y.; Farha, O. K.; Hong, B. J.; Sarjeant, A. A.; Nguyen,
Conclusions
The utility of NU-109 and NU-110 as new benchmark, ultraꢀ
high surface area materials has been demonstrated syntheticalꢀ
ly and corroborated computationally. We also have shown that
the theoretical upper limit for MOF surface areas is 14,600
m2/g, if not higher.
S. T.; Hupp, J. T. J. Am. Chem. Soc. 2011, 133, 15858.
(17) Kent, C. A.; Mehl, B. P.; Ma, L.; Papanikolas, J. M.; Meyer, T.
J.; Lin, W. J. Am. Chem. Soc. 2010, 132, 12767.
(18) Horcajada, P.; Serre, C.; ValletꢀRegí, M.; Sebban, M.; Taulelle,
F.; Férey, G. Angew. Chem., Int. Ed. 2006, 45, 5974.
(19)
(20)
Rocca, J. D.; Liu, D.; Lin, W. Acc. Chem. Res. 2011, 44, 957.
Li, H.; Eddaoudi, M.; Groy, T. L.; Yaghi, O. M. J. Am. Chem.
ASSOCIATED CONTENT
Soc. 1998, 120, 8571.
(21)
Férey, G.; MellotꢀDraznieks, C.; Serre, C.; Millange, F.;
Supporting Information. Synthesis of LH6 ligand, NU-109E
and NU-110E MOFs; Xꢀray crystallography analysis, activation,
N2 gas adsorption, pore size distribution, PXRD, and experimental
Dutour, J.; Surblé, S.; Margiolaki, I. Science 2005, 309, 2040.
(22)
Koh, K.; WongꢀFoy, A. G.; Matzger, A. J. J. Am. Chem. Soc.
2009, 131, 4184.
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 6 of 7
(23)
Li, H.; Eddaoudi, M.; O'Keeffe, M.; Yaghi, O. M. Nature
(40)
Park, H. J.; Lim, D.ꢀW.; Yang, W. S.; Oh, T.ꢀR.; Suh, M. P.
1999, 402, 276.
Chem. Eur. J. 2011, 17, 7251.
1
2
3
(24)
Kaye, S. S.; Dailly, A.; Yaghi, O. M.; Long, J. R. J. Am. Chem.
(41)
Yan, Y.; Lin, X.; Yang, S.; Blake, A. J.; Dailly, A.;
Soc. 2007, 129, 14176.
Champness, N. R.; Hubberstey, P.; Schröder, M. Chem. Commun. 2009,
1025.
(25)
Chae, H. K.; SiberioꢀPérez, D. Y.; Kim, J.; Go, Y.; Eddaoudi,
4
5
6
7
M.; Matzger, A. J.; O'Keeffe, M.; Yaghi, O. M. Nature 2004, 427, 523.
(42)
16, 212.
(43)
Wang, Z.; Tanabe, K. K.; Cohen, S. M. Chem. Eur. J. 2010,
Sumida, K.; Hill, M. R.; Horike, S.; Dailly, A.; Long, J. R. J.
(26)
Furukawa, H.; Miller, M. A.; Yaghi, O. M. J. Mater. Chem.
2007, 17, 3197.
(27)
Koh, K.; WongꢀFoy, A. G.; Matzger, A. J. Angew. Chem., Int.
Am. Chem. Soc. 2009, 131, 15120.
(44)
Ed. 2008, 47, 677.
An, J.; Farha, O. K.; Hupp, J. T.; Pohl, E.; Yeh, J. I.; Rosi, N.
(28)
Nelson, A. P.; Farha, O. K.; Mulfort, K. L.; Hupp, J. T. J. Am.
L. Nat. Commun. 2012, 3, 604.
8
9
Chem. Soc. 2008, 131, 458.
(29)
(30)
(45)
Klein, N.; Senkovska, I.; Baburin, I. A.; Grünker, R.; Stoeck,
Farha, O. K.; Hupp, J. T. Acc. Chem. Res. 2010, 43, 1166.
Furukawa, H.; Ko, N.; Go, Y. B.; Aratani, N.; Choi, S. B.;
U.; Schlichtenmayer, M.; Streppel, B.; Mueller, U.; Leoni, S.; Hirscher,
M.; Kaskel, S. Chem. Eur. J. 2011, 17, 13007.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Choi, E.; Yazaydın, A. Ö.; Snurr, R. Q.; O'Keeffe, M.; Kim, J.; Yaghi, O.
M. Science 2010, 329, 424.
(46)
Yan, Y.; Telepeni, I.; Yang, S.; Lin, X.; Kockelmann, W.;
Dailly, A.; Blake, A. J.; Lewis, W.; Walker, G. S.; Allan, D. R.; Barnett,
S. A.; Champness, N. R.; Schröder, M. J. Am. Chem. Soc. 2010, 132,
4092.
(47)
M. J.; Eddaoudi, M. J. Am. Chem. Soc. 2008, 130, 1833.
(48) Eryazici, I.; Farha, O. K.; Hauser, B. G.; Yazaydın, A. Ö.;
Sarjeant, A. A.; Nguyen, S. T.; Hupp, J. T. Cryst. Growth Des. 2012, 12,
1075.
(49)
63, 344.
(50)
(31)
Farha, O. K.; Yazaydın, A. Ö.; Eryazici, I.; Malliakas, C. D.;
Hauser, B. G.; Kanatzidis, M. G.; Nguyen, S. T.; Snurr, R. Q.; Hupp, J. T.
Nature Chem. 2010, 2, 944.
Nouar, F.; Eubank, J. F.; Bousquet, T.; Wojtas, L.; Zaworotko,
(32)
Yuan, D.; Zhao, D.; Sun, D.; Zhou, H.ꢀC. Angew. Chem., Int.
Ed. 2010, 49, 5357.
(33)
Liu, J.; Thallapally, P. K.; McGrail, B. P.; Brown, D. R.; Liu,
J. Chem. Soc. Rev. 2012.
(34)
Schnobrich, J. K.; Koh, K.; Sura, K. N.; Matzger, A. J.
DelgadoꢀFriedrichs, O.; O'Keeffe, M. Acta Cryst. Sect. A 2007,
Langmuir 2010, 26, 5808.
(35)
Farha, O. K.; Wilmer, C. E.; Eryazici, I.; Hauser, B. G.; Parilla,
http://rcsr.anu.edu.au/.
Valente, C.; Choi, E.; Belowich, M. E.; Doonan, C. J.; Li, Q.;
P. A.; O’Neill, K.; Sarjeant, A. A.; Nguyen, S. T.; Snurr, R. Q.; Hupp, J.
T. J. Am. Chem. Soc. 2012, 134, 9860.
(51)
Gasa, T. B.; Botros, Y. Y.; Yaghi, O. M.; Stoddart, J. F. Chem. Commun.
2010, 46, 4911.
(52)
Hong, M.ꢀC. Chem. Commun. 2011, 47, 9861.
(53)
(54)
J. Phys. Chem. C 2007, 111, 15350.
(55)
T.; Nguyen, S. T. Dalton Trans. 2011, 40, 9189.
(36)
Denysenko, D.; Grzywa, M.; Tonigold, M.; Streppel, B.;
Krkljus, I.; Hirscher, M.; Mugnaioli, E.; Kolb, U.; Hanss, J.; Volkmer, D.
Chem. Eur. J. 2011, 17, 1837.
Han, D.; Jiang, F.ꢀL.; Wu, M.ꢀY.; Chen, L.; Chen, Q.ꢀH.;
(37)
Lin, X.; Telepeni, I.; Blake, A. J.; Dailly, A.; Brown, C. M.;
Connolly, M. L. Science 1983, 221, 709.
Düren, T.; Millange, F.; Férey, G.; Walton, K. S.; Snurr, R. Q.
Simmons, J. M.; Zoppi, M.; Walker, G. S.; Thomas, K. M.; Mays, T. J.;
Hubberstey, P.; Champness, N. R.; Schröder, M. J. Am. Chem. Soc. 2009,
131, 2159.
Eryazici, I.; Farha, O. K.; Compton, O. C.; Stern, C.; Hupp, J.
(38)
Zhao, D.; Yuan, D.; Sun, D.; Zhou, H.ꢀC. J. Am. Chem. Soc.
2009, 131, 9186.
(39)
Zheng, B.; Bai, J.; Duan, J.; Wojtas, L.; Zaworotko, M. J. J.
Am. Chem. Soc. 2011, 133, 748.
ACS Paragon Plus Environment

Page 7 of 7
Journal of the American Chemical Society
Table of Contents (TOC) Graphic.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
7
ACS Paragon Plus Environment