The Utilization of Amide Groups to Expand and Functionalize Metal-Organic Frameworks Simultaneously

Article abstract of DOI:10.1002/chem.201504907

A new stepwise ligand-elongation strategy by amide spacers is utilized to prepare isoreticularly high-porous metal-organic frameworks (MOFs), namely, quasi-mesoporous [Cu₂(PDBAD)(H₂O)]_n (H₄PDBAD=5,5′-((4,4′-((pyridine-3,5-dicarbonyl)bis(azanediyl))bis(benzoyl))bis(azanediyl))diisophthalic acid; NJU-Bai22: NJU-Bai for Nanjing University Bai's group), and mesoporous [Cu₂(PABAD)(H₂O)]_n (H₄PABAD=5,5′-((4,4′-((4,4′-((pyridine-3,5-dicarbonyl)bis(azanediyl))bis(benzoyl))bis (azanediyl))bis(benzoyl))bis(azanediyl))diisophthalic acid; NJU-Bai23). Compared with the prototypical MOF of [Cu₂(PDAD)(H₂O)]_n (H₄PDAD=5,5′-(pyridine-3,5-dicarbonyl)bis(azanediyl)diisophthalic acid; NJU-Bai21, also termed as PCN-124), both MOFs exhibit almost the same CO₂ adsorption enthalpy and CO₂ selectivity values, and better capacity for CO₂ storage under high pressure; these results make them promising candidate materials for CO₂ capture and sequestration. Interestingly, this new method, in comparison with traditional strategies of using phenyl or triple-bond spacers, is easier and cheaper, resulting in a better ability to retain high CO₂ affinity and selectivity in MOFs with large pores and high CO₂ storage capacity. Additionally, it may lead to the high thermal stability of the MOFs and also their tolerance to water, which is related to the balance between the density of functional groups and pore sizes. Therefore, this strategy could provide new opportunities to explore more functionalized mesoporous MOFs with high performance.

Full text of DOI:10.1002/chem.201504907

DOI: 10.1002/chem.201504907
Full Paper
&
Structure Elucidation |Hot Paper|
The Utilization of Amide Groups To Expand and Functionalize
Metal–Organic Frameworks Simultaneously
Zhiyong Lu,[a, b] Junfeng Bai,*[a] Cheng Hang,[a] Fei Meng,[a] Wenlong Liu,[c] Yi Pan,[a] and
Xiaozeng You[a]
Abstract: A new stepwise ligand-elongation strategy by
amide spacers is utilized to prepare isoreticularly high-
porous metal–organic frameworks (MOFs), namely, quasi-
mesoporous [Cu2(PDBAD)(H2O)]n (H4PDBAD=5,5’-((4,4’-((pyri-
dine-3,5-dicarbonyl)bis(azanediyl))bis(benzoyl))bis(azane-
diyl))diisophthalic acid; NJU-Bai22: NJU-Bai for Nanjing Uni-
versity Bai’s group), and mesoporous [Cu2(PABAD)(H2O)]n
(H4PABAD=5,5’-((4,4’-((4,4’-((pyridine-3,5-dicarbonyl)bis(aza-
and better capacity for CO2 storage under high pressure;
these results make them promising candidate materials for
CO2 capture and sequestration. Interestingly, this new
method, in comparison with traditional strategies of using
phenyl or triple-bond spacers, is easier and cheaper, result-
ing in a better ability to retain high CO2 affinity and selectivi-
ty in MOFs with large pores and high CO2 storage capacity.
Additionally, it may lead to the high thermal stability of the
MOFs and also their tolerance to water, which is related to
the balance between the density of functional groups and
pore sizes. Therefore, this strategy could provide new oppor-
tunities to explore more functionalized mesoporous MOFs
with high performance.
nediyl))bis(benzoyl))bis
(azanediyl))bis(benzoyl))bis(azane-
diyl))diisophthalic acid; NJU-Bai23). Compared with the pro-
totypical MOF of [Cu2(PDAD)(H2O)]n (H4PDAD=5,5’-(pyridine-
3,5-dicarbonyl)bis(azanediyl)diisophthalic acid; NJU-Bai21,
also termed as PCN-124), both MOFs exhibit almost the
same CO2 adsorption enthalpy and CO2 selectivity values,
Introduction
The best and most efficient CCS material should possess
both high storage capacity and high selectivity. However, the
design of CCS materials is still a great challenge.[1a,3a] To meet
these requirements, MOFs could serve as ideal platforms that
are capable of being deliberately and finely tailored and func-
tionalized on a molecular level. Several groups, including that
of Yaghi, have made profound contributions to the design of
MOFs with high CO2 affinity and selectivity, such as attaching
polar functional groups to organic ligands,[4] immobilizing ni-
trogen bases on open metal sites (OMSs),[5] impregnating
metal irons,[6] and shrinking inner pores to adapt to the size of
the CO2 molecule.[7] Nevertheless, these precedents commonly
face the problem of triggering a loss in the CO2 storage capaci-
ty of the MOFs upon improving their CO2 selectivity and, at
the same time, encountering a barrier of diffusion due to
smaller pores. On the other hand, if larger pores, mesopores
for instance, as well as high CO2 storage capacity are the main
focus, which is generally exemplified by isoreticular expansion
of MOFs through triple bonds or phenyl spacers,[8] the mass-
transfer problem may be appropriately avoided, but a decline
in CO2 selectivity would be induced. Inserting amide groups
into the skeleton of MOFs, as initiated by our group, is a prom-
ising approach for the functionalization of MOFs almost with-
out compromising the surface area and porosity; this gener-
ates MOFs with high CO2 selectivity and high CO2 storage ca-
pacity.[9]
Global warming caused by rapid accumulation of CO2 is of
great concern for society as the main factor that causes cli-
mate change.[1] To eliminate CO2 emission, great efforts have
been dedicated to developing versatile CO2 capture materials
with low energy consumption, and a number of porous solids
with good physical adsorption properties, such as zeolites and
carbons,[2] have been intensively investigated. Recently, metal–
organic frameworks (MOFs), emerging as a new type of materi-
al for CO2 capture and sequestration (CCS), have attracted
much interest due to their crystalline and modular nature in
both organic and inorganic parts.[3]
[a] Dr. Z. Lu, Prof. Dr. J. Bai, C. Hang, F. Meng, Prof. Dr. Y. Pan, Prof. Dr. X. You
State Key Laboratory of Coordination Chemistry
Nanjing University, Nanjing 210093 (P.R. China)
E-mail: bjunfeng@nju.edu.cn
[b] Dr. Z. Lu
College of Mechanics and Materials
Hohai University, Nanjing 210098 (P.R. China)
[c] Prof. Dr. W. Liu
College of Chemistry and Chemical Engineering
Yangzhou University, Yangzhou 225002 (P.R. China)
Supporting information and ORCID number from the author for this article
are available on the WWW under http://dx.doi.org/10.1002/
chem.201504907. It includes synthetic procedures, crystallographic tables,
powder XRD and thermogravimetric data, additional gas adsorption iso-
therms, Langmuir and BET surface area analyses, pore size distributions,
and details of the isosteric adsorption enthalpy and IAST calculations.
To further expand our work, and also inspired by the struc-
tures of proteins built upon repeating peptide bonds,[10] we
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wondered if it was possible to use the amide group as a basic
spacer in ligand elongation to further expand and functionalize
isostructural MOFs under the guidance of the isoreticular prin-
ciple.[11] Herein, a highly connected MOF with txt topology was
chosen as a target platform for isoreticular syntheses due to its
high stability as a results of high connectivity. Based upon a V-
shaped ligand, 5,5’-(pyridine-3,5-dicarbonyl)bis(azanediyl)dii-
sophthalic acid (H4PDAD; Figure 1a, n=0), by expanding the
ligand with para-aminobenzoic acid (PAB) units (with amide
groups embedded after the amidation reaction, as a semirigid
skeleton that comprehensively mediates the conflict between
isoreticular synthesis and flexibility[12]), isoreticular txt-type
MOFs were successfully synthesized. Compared with the proto-
typical MOF NJU-Bai21 (NJU-Bai for Nanjing University Bai’s
group) synthesized from H4PDAD, its extended analogues,
quasi-mesoporous NJU-Bai22 and mesoporous NJU-Bai23,
show much higher CO2 storage capacity, but comparable CO2
selectivity. This new way of ligand elongation, in contrast with
traditional strategies of using phenyl or triple-bond spacers,
can simultaneously realize pore expansion and functionaliza-
tion, and provide better access to mesoporous MOFs with high
CO2 storage capacity, as well as good CO2 affinity and selectivi-
ty. Meanwhile, some other problems caused by pure acetylene
or phenyl groups, such as low solubility of ligands, complicat-
ed procedures, and high cost in synthesis, can be solved sub-
sequently.
Results and Discussion
Synthesis and crystal structure
Preliminary exploratory reactions were based on solvothermal
reactions between cupric nitrate and V-shaped ligands (Fig-
ure 1a) in similar solvent systems. The reaction of H4PDAD (n=
0) and Cu(NO3)2·3H2O in a mixture of DMF/H2O (5/1 v/v) con-
taining HNO3 afforded blue rhombic dodecahedral crystals of
[Cu2(PDAD)(H2O)]n, NJU-Bai21 (also termed as PCN-124[13]).
Based upon H4PDAD, ligands were elongated with one or two
pairs of PAB units, and then H4PDBAD (5,5’-((4,4’-((pyridine-3,5-
dicarbonyl)bis(azanediyl))bis(benzoyl))bis(azane -diyl))diisoph-
thalic acid) (n=1) and H4PABAD (5,5’-((4,4’-((4,4’-((pyridine-3,5-
dicarbonyl)bis(azanediyl))bis(benzoyl))bis (azanediyl))bis(ben-
zoyl))bis(azanediyl))diisophthalic acid) (n=2; Figure 1a and
Scheme 1) were successfully synthesized. From these two li-
gands, [Cu2(PDBAD)(H2O)]n (NJU-Bai22) and [Cu2(PABAD)(H2O)]n
(NJU-Bai23) were correspondingly obtained.
¯
NJU-Bai21 crystallizes in cubic space group Im3m. It exhibits
a typical (3,36)-connected txt topology[14] (Figure 1c) isostruc-
tural to that of Cu-DBPP[13], which is connected with triple-
bond spacers instead. (For clarity, Cu-DBPP and PCN-124 were
renamed as NJU-Bai20 and NJU-Bai21, respectively, in our in-
cipient work for zero and one pair of amide groups in their li-
gands; and likewise for NJU-Bai22 and -Bai23 shown in Fig-
Figure 1. a) V-shaped ligand simplified as a three-connected node. b) Small rhombihexahedron cage simplified as a 36-connected node. c) The (3,36)-connect-
ed txt topology. d) Specific connections between the ligand and small rhombihexahedron cages. e) Three kinds of cages (or pores) and their packing mode.
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Scheme 1. The syntheses of H4PDAD, H4PDBAD, and H4PABAD. DMA=N,N-
dimethylacetamide, DMAP=4-dimethylaminopyridine.
Figure 2. Isoreticular expansion of txt-type MOFs induces a variation in pore
size from micro- to mesopores.
ure S7 in the Supporting Information.) Three types of cages (A,
B, and C) exist in NJU-Bai21 with diameters of 1.2, 1.1, and
0.76 nm (Figure 2), respectively.
culated by using the PLATON routine, with a solvent-accessible
volume of 66.2% in the dehydrated structure of NJU-Bai22.
The isoreticular character of NJU-Bai21 and NJU-Bai22 re-
veals good consistency in isoreticular synthesis by the V-
shaped ligands; thus the crystal structure of NJU-Bai23, with
longer ligands, is assumed to be of the same type. In the
shape of a rhombic dodecahedron, NJU-Bai23 crystallizes with
a size of about 2”2”2 mm3. However, due to very weak dif-
fraction, the single-crystal structure of NJU-Bai23 was not suc-
cessfully obtained. To confirm the structure of NJU-Bai23, we
loaded a single crystal of it onto an X-ray diffractometer with
CuKa radiation for unit cell analysis; the values are listed in
Table 1. The same crystal system and gradually increasing cell
volumes after ligand elongation imply the isoreticular feature
of NJU-Bai23 as being similar to those of NJU-Bai22 and -Bai21.
Furthermore, the powder X-ray diffraction (PXRD) pattern of
As an isostructural analogue of NJU-Bai21, NJU-Bai22 also
¯
crystallizes in cubic space group Im3m, and the symmetric unit
consists of one quarter of a PDBAD ligand, two crystallographi-
cally quarter Cu2+ ions, and one quarter of a coordinated
water molecule (Figure S8b in the Supporting Information). All
copper clusters reveal a paddle-wheel-like shape, of which four
equatorial sites are occupied by different benzene-1,3-dicar-
boxylate (bdc) moieties. One of the axial sites of the paddle-
wheel is coordinated to the pyridyl nitrogen atom of the
ligand, which makes the paddle-wheel a site for extension.
Therefore, the small rhombihexahedron cage, widely known as
a “nanoball”,[15] is composed of 12 cupric paddle-wheel clusters
and 24 bdc moieties; in total, this results in 36 points of exten-
sion (Figure 1). As expected, NJU-Bai22 exhibits the same txt
topology (Figure 1 and Figure S7 in the Supporting Informa-
tion), by simplifying ligands to 3-connnected nodes and nano-
balls as 36-connected nodes. The overall structure also consists
of three types of cages, cages A, B, and C, as shown in
Figure 2. Two of them are strongly correlated with the size of
the ligands. Thus, owing to ligand expansion, cage B is extend-
ed to a diameter of 1.9 nm, which is close to that of a meso-
pore, and cage C is inflated to 1.2”0.72 nm3 (Figure 2). The
inner cavity of NJU-Bai22 endows it with high porosity, as cal-
Table 1. Crystal unit cell parameters obtained from single-crystal X-ray
experiments.
MOFs
Length of
ligand [Š]
Crystal
system
a=b=c
[Š]
a=b=g
[8]
V
[Š
À3
]
NJU-Bai21
NJU-Bai22
NJU-Bai23
17
25
36
cubic I
cubic I
cubic I
30.41
38.72
46.03
90
90
90
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NJU-Bai23 was fully indexed and a LeBail profile fitting routine
was performed by using the Rietica software (Rp=2.855%,
¯
wRp=4.977%); this resulted in a space group of Im3m with
3
a=46.0307 Š and V=97531.0 Š (Figure S10 in the Supporting
Information). Clearly, crystal parameters obtained from the
PXRD pattern coincide with that measured on the single-crys-
tal X-ray diffractometer, which confirms the assumption of the
structure of NJU-Bai23. Through a comparison of the PXRD
patterns of NJU-Bai23, -Bai22, and -Bai21, as shown in Figure 3,
Figure 3. PXRD patterns and crystal-shape comparison of NJU-Bai21, -Bai22,
and -Bai23.
Figure 4. a) N2 adsorption isotherms of NJU-Bai20, -Bai21, -Bai22, and -Bai23
at 77 K. b) PSDs in NJU-Bai20, -Bai21, -Bai22, and -Bai23.
shifting of the principal diffraction lines toward lower angles
after ligand elongation indicates isoreticular crystal-lattice ex-
pansion. Similar shifting of PXRD peaks synchronous with
ligand elongation is commonly observed in isoreticular
MOFs;[8a,16] thus, to some extent, validating our inference
about the crystal structure of NJU-Bai23. Meanwhile, a similar
crystal shape also contributes perceptive evidence. Therefore,
based upon the connectivity of NJU-Bai21 and -Bai22, the cage
models of NJU-Bai23 were constructed by using Gaussian-
View 3.0. As shown in Figure 2, cage B in NJU-Bai23 is extend-
ed to have a diameter of 2.9 nm and cage C is extended to
1.7”0.82 nm3. The accuracy of these models and their pore
apertures can be further confirmed by pore size distribution
(PSD) analysis of NJU-Bai23 given in the following section,
making NJU-Bai23 one of the mesoporous MOFs. Notably, the
geometry of the main pore, cage B, gradually changes from fu-
siform in NJU-Bai21 to approximately spherical in NJU-Bai23,
which may contribute to the mechanical stability of NJU-Bai23.
Similar behavior was also observed in the Ar isotherm of NJU-
Bai23 at 87 K, as shown in Figure S19 in the Supporting Infor-
mation. The occurrence of multilayer sorption in the large mes-
oporous cavities after surface coverage and small pore filling
may explain this stepwise sorption behavior. The saturated ni-
trogen uptakes at 77 K in NJU-Bai22 and NJU-Bai23 are 758
and 1157 cm3 gÀ1, which feature high Langmuir surface areas
of about 3299 and 5142 m2 gÀ1, respectively, if monolayer cov-
erage of N2 is assumed. Notably, the Langmuir surface area of
NJU-Bai23 is comparable to that of MOF-177[19] (5340 m2 gÀ1),
MIL-101c[20] (5900 m2 gÀ1), PCN-66[8c] (4600 m2 gÀ1), and PCN-
68[8c] (6033 m2 gÀ1); this makes it a MOF with one of the high-
est surface areas. By applying the BET model, the apparent sur-
face area of NJU-Bai22 was calculated to be 2177 m2 gÀ1. For
NJU-Bai23, from the first plateau, the BET surface area was cal-
culated to be 2519 m2 gÀ1. In contrast, NJU-Bai20 and NJU-
Bai21 with smaller ligands exhibit total nitrogen uptakes of
580 and 510 cm3 gÀ1 (Figure 4a), with BET surface areas of 2221
and 1979 m2 gÀ1. The total pore volumes of NJU-Bai22 and
-Bai23 obtained from N2 isotherms (P/P0 =0.976) are 1.17 and
1.75 cm3 gÀ1, of which the latter is higher than that of
some well-known mesoporous MOFs, such as MOF-177
(1.59 cm3 gÀ1), PCN-66 (1.36 cm3 gÀ1), and NOTT-112[17a]
(1.62 cm3 gÀ1). Based on the Ar adsorption isotherm of NJU-
Bai22 at 87 K (Figure S19 in the Supporting Information), PSD
analysis by nonlocal density functional theory (NLDFT) meth-
ods shows that there are distributions of micropores at 0.6–0.9
and 1.1–1.2 nm, and quasi-mesopores at 1.5–2.1 nm (Fig-
Surface area and porosity
The permanent porosity of NJU-Bai22 and -Bai23 was con-
firmed by N2 adsorption measurements at 77 K. As shown in
Figure 4a, NJU-Bai22 exhibits a reversible pseudo-type I iso-
therm with a slight step before the plateau appears, which is
typical in MOFs with both micro- and mesopores.[17] In con-
trast, NJU-Bai23 reveals distinctive step at P/P0 ꢀ0.16 with
a clear hysteresis in its type IV isotherm, which is a characteris-
tic of MOFs with hierarchically assembled mesopores.[8a,16d,18]
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ure 4b), which coincides with the three types of cages ob-
served in the crystal structure of NJU-Bai22. To test the reliabili-
ty of the NLDFT mode, the pore distributions of NJU-Bai20 and
-Bai21 were also analyzed; all results were in good accordance
with pore sizes measured in their crystal structures (Figure 2
and Figure S6 in the Supporting Information). Then, for NJU-
Bai23, the same analysis method was applied, and the pore
sizes were distributed among 0.7–0.9, 1.5–1.7, and around
2.9 nm (Figure 4b). Clearly, these results are consistent with
the pores we built for NJU-Bai23; therefore, the crystal struc-
ture of NJU-Bai23 and its mesoporous characteristic can be
confirmed.
decreases in CO2 adsorption relative to NJU-Bai21 (72.9 cm3 gÀ1
for NJU-Bai22 and 49.0 cm3 gÀ1 for NJU-Bai23 at 298 K and
1 bar) were observed, which is a common phenomenon after
pore expansion,[19,8c] slight bending along the y axis in the
curve of the adsorption isotherms indicates strong interactions
between CO2 molecules and the framework. As illustrated in
Figure 5c, the zero-coverage CO2 adsorption enthalpies of
NJU-Bai22 and NJU-Bai23 were calculated to be 25.6 and
25.1 kJmolÀ1, respectively. Both values are close to that of NJU-
Bai21 and much higher than that of NJU-Bai20; this implies
that the strong CO2 affinity of the frameworks can be retained
after ligand elongation with repeated amide spacers.
Because the utilization of amide spacers can largely retain
the adsorption enthalpy of CO2, we further investigated the
CO2 selectivities of the four isoreticular analogues. As shown in
Figures S28–S31 in the Supporting Information, the CH4 and N2
adsorption isotherms of NJU-Bai20, -Bai21, -Bai22, and -Bai23
were collected at 298 K. Although the CO2 adsorption capacity
declines upon ligand elongation, the N2 and CH4 adsorptions
also show similar tendencies. Initially, the amount of CH4
uptake of NJU-Bai21 at 1 bar is 20.3 cm3 gÀ1. After ligand elon-
gation with one unit, NJU-Bai22 can only adsorb 16.1 cm3 gÀ1
of CH4. With ligand elongated by two units, the amount of CH4
uptake of NJU-Bai23 decreases to 11.9 cm3 gÀ1. Similar behavior
was also observed in the N2 uptakes, from 4.82 cm3 gÀ1 in NJU-
Bai21 to 4.07 cm3 gÀ1 in NJU-Bai22 and 2.52 cm3 gÀ1 in NJU-
Bai23. This consistency may lead to the invariability of CO2 se-
lectivity. Thus, based upon experimental CO2, CH4, and N2 iso-
therms, the CO2 selectivities of NJU-Bai21, -Bai22, and -Bai23
were calculated by means of simplified ideal adsorption solu-
tion theory (IAST), which serves as the benchmark for the sim-
CO2 adsorption properties and selectivities
To investigate the influence of ligand elongation by amide
spacers on CO2 uptake capacity, we continued to measure the
CO2 adsorption behavior of these analogues at 273 and 298 K.
It is our preconception that the CO2 affinities and selectivities
of the two new isoreticular analogues should be almost the
same as that of NJU-Bai21 and much higher than that of NJU-
Bai20 without amide groups. Like the results demonstrated in
our previous work,[9a,b,e–g] the introduction of amide spacers in
NJU-Bai21 significantly improves CO2 adsorption (206.5 cm3 gÀ1
at 273 K and 1 bar and 115.1 cm3 gÀ1 at 298 K and 1 bar), com-
pared with NJU-Bai20 with triple-bond spacers (136.4 cm3 gÀ1
at 273 K and 1 bar and 68.0 cm3 gÀ1 at 298 K and 1 bar; Fig-
ure 5a and b). Correspondingly, the CO2 adsorption enthalpy
shows a clear increase, from 22.2 kJmolÀ1 for NJU-Bai20 to
25.9 kJmolÀ1 for NJU-Bai21, with zero coverage (Figure 5c). For
NJU-Bai22 and -Bai23 with longer ligands, although gradual
Figure 5. CO2 adsorption isotherms of NJU-Bai20, -Bai21, -Bai22, and -Bai23 at 273 (a) and 298 K (b). c) CO2 adsorption enthalpies of NJU-Bai20, -Bai21, -Bai22,
and -Bai23. d) The selectivities of CO2 over N2 and CH4 of NJU-Bai20, -Bai21, -Bai22, and -Bai23. e) CO2 adsorption isotherms of NJU-Bai20, -Bai21, -Bai22, and
-Bai23 in the high-pressure range.
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ulation and computational analysis of binary mixture adsorp-
tion from experimental isotherms.[1a,21] The adsorption selectivi-
ty is defined as Si/j =(q1/q2)/(p1/p2), in which qi is the amount of
i adsorbed and pi is the partial pressure of i in the mixture. As
shown in Figure 5d, at 1 bar in a binary mixture of CO2 and N2
with a ratio of 15:85, the predicted CO2/N2 selectivities of NJU-
Bai21, -Bai22, and -Bai23 are 93, 81, and 72, respectively. In an
equimolar gas-phase mixture of CO2 and CH4, the CO2 selectivi-
ties of NJU-Bai21, -Bai22, and -Bai23 are 7.8, 6.7, and 5.8, re-
spectively. Clearly, ligand expansion does not cause a drastic
decline in CO2 selectivity against N2 and CH4. Given that the
CO2/N2 and CO2/CH4 selectivities of NJU-Bai23 show a slight de-
crease compared with that of NJU-Bai21, they are still about
two times that of NJU-Bai20 without amide groups (CO2/N2:
31, CO2/CH4: 3.9) and significantly higher than that of some
well-known MOFs, such as CuBTC (CO2/N2: 21, CO2/CH4: 5),[22]
bio-MOF-11 (CO2/N2: 36),[22,23] Cu-TPBTM (CO2/N2: 21)[9f] and
MOF-177 (CO2/N2:5, CO2/CH4:4.4),[24] as shown in Table S3 in
the Supporting Information. The high selectivities of CO2 over
N2 and CH4 in these three isoreticularly amide-decorated MOFs
suggest their possible application in capturing CO2 from flue
gas or upgrading natural gas; meanwhile, these MOFs are also
rare examples of retaining good CO2 selectivity in mesoporous
MOFs.
Table 2. Density of functional groups in NJU-Bai21, -Bai22, -Bai23, and
their hypothetical isostructural counterparts with phenyl or triple-bond
spacers.
[b]
[c]
[d]
MOFs
V
[Š
NOMS
NLBS
DF
À3
]
[nmÀ3
]
NJU-Bai21
NJU-Bai22
NJU-Bai23
NJU-Bai21-P/T[a]
NJU-Bai22-P/T
NJU-Bai23-P/T
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24
24
24
24
24
24
48
96
144
0
0
0
2.5
2.1
1.7
0.85
0.4
0.24
[a] P/T indicates isostructural MOFs with phenyl or triple-bond spacers in-
stead of amide spacers. [b] Amount of OMSs per unit cell. [c] Amount of
LBSs per unit cell. [d] DF =density of functional groups.
capacity; however, herein there is a contradiction, which im-
plies that the amide groups promote CO2 storage. After elon-
gating the ligands by one unit, NJU-Bai22 shows a higher
excess CO2 uptake of 937 mggÀ1 (48.4 wt%) at 40 bar. If gas-
eous CO2 compressed within the pore void is taken into con-
sideration, the total CO2 uptake is 1046 mggÀ1 (51.5 wt%) at
40 bar. This value is larger than those of Cu-TDPAT[26]
(892 mggÀ1, SBET =1938 m2 gÀ1), IRMOF-6[1b] (858 mggÀ1, SBET
2516 m2 gÀ1), MIL-100(Cr)[27] (792 mggÀ1 BET =1900 m2 gÀ1),
=
Ligand elongation in the isoreticular synthesis of NJU-Bai21
not only generates large pores, mesopores for instance, but
also retains good affinity for CO2 molecules and good CO2 se-
lectivity. This phenomenon should be mainly due to retaining
the density of functional groups. It is widely acknowledged
that OMSs are a distinct type of binding sites preferred by CO2
molecules.[25] Together with the amide groups, classified as
Lewis base sites (LBSs), two main kinds of binding sites for CO2
molecules exist in the three amide-decorated analogues NJU-
Bai21, -Bai22, and -Bai23. As the cell volume increases gradual-
ly, the amount of OMSs remains constant, whereas the quanti-
ty of LBSs almost doubles. Thus, the density of functional
groups only shows a small decline (from 2.5 nmÀ3 to 2.1 and
1.7 nmÀ3), although a steep increase in cell volume occurs,
which contributes to the slight decline in CO2 adsorption en-
thalpy. Assuming that the amide spacers of these amide-deco-
rated analogues were substituted by phenyl or triple-bond
spacers and their cell volumes almost remained constant, simi-
lar to the traditional method of ligand elongation without
LBSs, the densities of functional groups in the substitutes
would be far lower than those of their prototypes (Table 2),
which would make the CO2 affinities and selectivities of substi-
tutes for NJU-Bai22 and -Bai23 even lower than that of a substi-
tute of NJU-Bai21, namely, NJU-Bai20.
, S
IRMOF-11[1b] (647 mggÀ1, SBET =2096 m2 gÀ1), and HKUST-1[1b]
(40.1 wt%, SBET =2211 m2 gÀ1), with a comparative surface area
to NJU-Bai22. For NJU-Bai23, it is not yet saturated when the
pressure reaches 40 bar. At this pressure, the excess CO2
uptake amount is 1268 mggÀ1 (55.9 wt%) and the total CO2
uptake is 1430 mggÀ1 (58.9 wt%). Although the total CO2
uptake of NJU-Bai23 is much lower than that of some MOFs
with extremely high surface areas, such as MOF-210 and MOF-
200,[19] it is still comparable to those of MOF-177[19]
(1356 mggÀ1, SBET =4500 m2 gÀ1) and MOF-205[19] (1495 mggÀ1,
S
BET =4460 m2 gÀ1); even NJU-Bai23 has a much lower BET sur-
face area. Interestingly, the CO2 adsorption isotherm of NJU-
Bai23 shows two distinct steps at P=15 and P=25 bar without
hysteresis, whereas NJU-Bai22 shows a slight step at P=12 bar
in its CO2 adsorption isotherm. This may be correlated to flexi-
bility induced by the amide groups. When CO2 molecules fill
the pores under high pressure, the PAB moieties begin to
rotate to adapt to the congested environment caused by CO2
molecules. Because the ligands of NJU-Bai22 and NJU-Bai23
are expanded by one and two pairs of PAB units, respectively,
their CO2 adsorption isotherms under high pressure reveal one
and two steps correspondingly. Therefore, the reasonability of
the structural assumption for NJU-Bai23 is again confirmed.
Bearing in mind the large pores we obtained, and the good
CO2 enthalpies and selectivities resulting from the amide
spacers, we further measured the CO2 storage capacity of the
four isoreticular analogues at 298 K under high pressure. As
shown in Figure 5e, although NJU-Bai21 possesses a lower sur-
face area and pore volume than NJU-Bai20, a higher CO2
uptake amount was observed in NJU-Bai21, especially between
0 and about 10 bar. According to common sense, a larger sur-
face area and pore volume will guarantee a better gas storage
Thermal and water stability
Due to the high connectivity of this kind of (3,36)-connected
MOFs, we further investigated the stability. A large quantity of
bulk materials was prepared and applied in thermal stability
and water stability measurements. The purity of the bulk mate-
rials has been demonstrated by the good agreement between
the PXRD patterns and simulated patterns from single-crystal
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Figure 6. Variable-temperature (VT) PXRD patterns of activated samples of NJU-Bai21 (a), -Bai22 (b), and -Bai23 (c) under vacuum. The temperature increased
by 308C from 30 to 4508C. Results of water stability tests for NJU-Bai21 (d), -Bai22 (e), and -Bai23 (f), respectively.
data (Figure 6d–f). Each sample was divided into two parts:
the activated one for VT-PXRD measurements in vacuum (Fig-
ure 6a–c) and the as-synthesized one for VT-PXRD measure-
ment in vacuum (Figures S39–S42 in the Supporting Informa-
tion). As shown in Figure 6, the structural compactness of the
whole framework endows this type of MOF with good thermal
stability. For NJU-Bai21, a shifting of PXRD peaks to higher
angles was observed at 3008C, which indicated flexibility of
the whole structure at high temperature; this later induced
structural collapse. For NJU-Bai22, no similar behavior was ob-
served and it retained its structure below 3908C. After expan-
sion of ligands by two units, the activated sample of NJU-Bai23
can be stable up to 4208C, although the as-synthesized
sample easily collapses under vacuum due to the evacuation
of solvent molecules (Figure S42 in the Supporting Informa-
tion). For an activated sample of NJU-Bai23, longer ligands
make the main pores (cage B) more approximately spherical,
which is stable from a mechanical perspective. Thus, without
the interruption of solvent molecules, NJU-Bai23 exhibits
higher thermal stability than that of NJU-Bai21 and NJU-Bai22.
However, if solvent molecules exist, surface tension caused by
their evacuation would easily lead to the distortion of ligands,
especially for longer ligands, as illustrated in Figure S36 in the
Supporting Information, and then structural collapse is trig-
gered, as exemplified by the as-synthesized sample of NJU-
Bai23. Therefore, for the activated sample as the main form in
practical applications, longer ligands endow this type of MOF
with higher thermal stability, as also demonstrated by ther-
mogravimetric analysis (TGA; Figures S32–S35 in the Support-
ing Information).
for more than one week in water (Figure S38 in the Supporting
Information). This good performance can be attributed to two
factors. First, half of the axial sites of copper paddle wheels are
occupied by pyridyl groups with CuÀN bonds, which are stron-
ger bonds than CuÀO bonds.[3a] When water molecules attack
metal clusters, strong bonds ensure better resistance. Second,
the hydrophobic acetylene groups in the ligands provide a hy-
drophobic environment in the pores. In this respect, if the hy-
drophobic moieties are substituted by some polar functional
groups to improve the affinity for specific gases, as exemplified
by NJU-Bai21, NJU-Bai22, and NJU-Bai23 with amide groups,
the water stability will be weakened. Therefore, NJU-Bai21 can
only maintain its structure for 36 h and NJU-Bai23 can last no
longer than 3 h. Surprisingly, the water stability of NJU-Bai22 is
comparable to that of NJU-Bai20, and much better than those
of NJU-Bai21 and NJU-Bai23. NJU-Bai22 is able to maintain its
structure for eight days, although part of it collapses into an
amorphous state. To explain this phenomenon, two factors
should be discussed: the density of the functional groups and
pore sizes. A higher density of functional groups means that
water molecules are attracted more easily, which causes the
breakdown of the whole framework. Meanwhile, large pores
permit free shuttling of water molecules; this raises the possi-
bility of water molecules attacking metal clusters. NJU-Bai22,
which possesses a moderate density of functional groups and
suitable pore sizes, therefore, exhibits the best water stability
of the three amide-decorated analogues.
Conclusion
When water stability tests were conducted, the as-synthe-
sized samples were directly immersed in fresh water and PXRD
patterns were collected every 12 h (Figure 6d–f). NJU-Bai20
shows the best water stability and its structure can be retained
We systematically used amide groups for ligand elongation
and MOF functionalization simultaneously, and successfully
synthesized quasi-mesoporous NJU-Bai22 and mesoporous
NJU-Bai23. In contrast with prototypical NJU-Bai21, although
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for NJU-Bai20, NJU-Bai21, and NJU-Bai22, respectively) for 20 h
under vacuum. For NJU-Bai23, the as-synthesized sample was
washed with DMF three times and then soaked in anhydrous
methanol for 3 days for solvent exchange. The sample was then ac-
tivated by supercritical CO2 (SCD) and then dried again under
vacuum for 6 h at 608C prior to gas adsorption/desorption meas-
urements. PSD was calculated from analysis of the Ar isotherm (ad-
sorption branch) at 87 K by using NLDFT, which implemented
a hybrid kernel based on a zeolite/silica model containing cylindri-
cal pores in the software package of Quantachrome AUTOSORB-
1 automatic volumetric instrument.
the pore apertures in NJU-Bai22 were expanded to the quasi-
mesoporous scale, the CO2 adsorption enthalpy and selectivity
remained almost constant, although the CO2 storage capacity
improved. Furthermore, the high thermal and water stability
make it a promising candidate for CCS. After further expansion,
mesoporous NJU-Bai23 still exhibits comparable CO2 adsorp-
tion enthalpy and selectivity, with an even higher CO2 storage
capacity and higher thermal stability, but it is vulnerable to
attack from water. NJU-Bai23 is a rare example of a mesoporous
MOF that exhibits a high CO2 storage capacity and high CO2
selectivity. The strategy of isoreticular expansion by amide
spacers may provide a new way to simultaneously expand the
pores and functionalize MOFs. Moreover, compared with tradi-
tional strategies, it is easier and cheaper and performs better
at retaining the CO2 affinity and selectivity of MOFs with large
pores and high CO2 storage capacity. Therefore, continuous
work to obtain txt or other types of MOFs with even larger
pores is still ongoing.
The wt% gas uptake is defined by Equation (1):
wt % ¼ ð100 Â NÞ=ð1000 þ NÞ
ð1Þ
in which N is excess (or total) adsorption (Nexc or Ntot, mggÀ1).
Acknowledgements
We are grateful for support of this work by the Natural Science
Foundation of China (21371091, 21371150).
Experimental Section
General
Keywords: amides
materials · metal–organic frameworks · structure elucidation
· isoreticular synthesis · mesoporous
All chemical reagents were obtained from commercial sources and,
unless otherwise noted, were used as received without further pu-
rification. 1H NMR spectra were recorded on a Bruker DRX-500
spectrometer with tetramethylsilane (TMS) as an internal reference.
Elemental analyses (C, H, and N) were performed on a PerkinElmer
240 analyzer. The IR spectra were recorded in the range of n˜ =
400–4000 cmÀ1 on a VECTOR TM 22 spectrometer as KBr pellets.
PXRD data were collected on a Bruker D8 ADVANCE X-ray diffrac-
tometer, at 40 kV, 40 mA, with CuKa radiation, equipped with a vari-
able-temperature stage and a vacuum system, with a scan speed
of 0.1 s8À1. The sample was held at the designated temperature for
at least 10 min between each scan. TGA was performed under an
N2 atmosphere (100 mLminÀ1) at a heating rate of 58CminÀ1 by
using a 2960 SDT thermogravimetric analyzer. MOF supercritical
CO2 drying was performed by using a Tousimisꢁ Samdriꢂ PVT-30
critical point dryer (Tousimis, Rockville, MD, USA).
[1] a) D. M. D’Alessandro, B. Smit, J. R. Long, Angew. Chem. Int. Ed. 2010, 49,
6058–6082; Angew. Chem. 2010, 122, 6194–6219; b) A. R. Millward,
O. M. Yaghi, J. Am. Chem. Soc. 2005, 127, 17998–17999.
[2] a) N. Hedin, L. Chen, A. Laaksonen, Nanoscale 2010, 2, 1819–1841; b) O.
Cheung, N. Hedin, RSC Adv. 2014, 4, 14480–14494; c) J. Wei, D. Zhou, Z.
Sun, Y. Deng, Y. Xia, D. Zhao, Adv. Funct. Mater. 2013, 23, 2322–2328.
[3] a) K. Sumida, D. L. Rogow, J. A. Mason, T. M. McDonald, E. D. Bloch, Z. R.
Herm, T. H. Bae, J. R. Long, Chem. Rev. 2012, 112, 724–781; b) Z. Zhang,
Z.-Z. Yao, S. Xiang, B. Chen, Energy Environ. Sci. 2014, 7, 2868–2899;
c) W. Lu, W. M. Verdegaal, J. Yu, P. B. Balbuena, H.-K. Jeong, H.-C. Zhou,
Energy Environ. Sci. 2013, 6, 3559–3564; d) S. Horike, K. Kishida, Y. Wata-
nabe, Y. Inubushi, D. Umeyama, M. Sugimoto, T. Fukushima, M. Inukai,
S. Kitagawa, J. Am. Chem. Soc. 2012, 134, 9852–9855; e) T.-H. Bae, M. R.
Hudson, J. A. Mason, W. L. Queen, J. J. Dutton, K. Sumida, K. J. Micklash,
S. S. Kaye, C. M. Brown, J. R. Long, Energy Environ. Sci. 2013, 6, 128–
138; f) O. Shekhah, Y. Belmabkhout, Z. Chen, V. Guillerm, A. Cairns, K.
Adil, M. Eddaoudi, Nat. Commun. 2014, 5, 4228.
Syntheses of ligands
[4] a) R. Banerjee, H. Furukawa, D. Britt, C. Knobler, M. O’Keeffe, O. M. Yaghi,
J. Am. Chem. Soc. 2009, 131, 3875–3877; b) H. Deng, C. J. Doonan, H.
Furukawa, R. B. Ferreira, J. Towne, C. B. Knobler, B. Wang, O. M. Yaghi,
Science 2010, 327, 846–850; c) W. Morris, B. Leung, H. Furukawa, O. K.
Yaghi, N. He, H. Hayashi, Y. Houndonougbo, M. Asta, B. B. Laird, O. M.
Yaghi, J. Am. Chem. Soc. 2010, 132, 11006–11008; d) Y.-S. Bae, O. K.
Farha, J. T. Hupp, R. Q. Snurr, J. Mater. Chem. 2009, 19, 2131–2134; e) T.
Gadzikwa, O. K. Farha, K. L. Mulfort, J. T. Hupp, S. T. Nguyen, Chem.
Commun. 2009, 3720–3722; f) Y. Zhao, H. Wu, T. J. Emge, Q. Gong, N.
Nijem, Y. J. Chabal, L. Kong, D. C. Langreth, H. Liu, H. Zeng, J. Li, Chem.
Eur. J. 2011, 17, 5101–5109; g) Z. Chen, S. Xiang, H. D. Arman, P. Li, D.
Zhao, B. Chen, Eur. J. Inorg. Chem. 2011, 2227–2231; h) Z. Chen, S.
Xiang, H. D. Arman, J. U. Mondal, P. Li, D. Zhao, B. Chen, Inorg. Chem.
2011, 50, 3442–3446.
[5] a) T. M. McDonald, D. M. D’Alessandro, R. Krishna, J. R. Long, Chem. Sci.
2011, 2, 2022–2028; b) T. M. McDonald, W. R. Lee, J. A. Mason, B. M.
Wiers, C. S. Hong, J. R. Long, J. Am. Chem. Soc. 2012, 134, 7056–7065.
[6] a) H. J. Park, M. P. Suh, Chem. Sci. 2013, 4, 685–690; b) Y.-S. Bae, B. G.
Hauser, O. K. Farha, J. T. Hupp, R. Q. Snurr, Microporous Mesoporous
Mater. 2011, 141, 231–235.
Details of the synthesis of H4PDAD (2), two new ligands H4PDBAD
(4) and H4PABAD (6), and H4PDED are given in the Supporting In-
formation.
Gas adsorption
Low-pressure gas sorption measurements were conducted by
using a Micrometritics ASAP 2020 surface area and pore size ana-
lyzer up to saturated pressure at different temperatures. High-pres-
sure gravimetric CO2 adsorption measurements were performed on
an ISOSORP HyGpra+V adsorption analyzer (Rubotherm, Germany)
over the 0–40 bar range at 298 K. Before the gas sorption measure-
ments, more than 400 mg (about 100 mg for high-pressure gas ad-
sorption) of as-synthesized samples of NJU-Bai20, NJU-Bai21, and
NJU-Bai22 were washed with DMF and methanol. Fresh anhydrous
methanol was then added and the samples were allowed to soak
for 3 days for solvent exchange. During this period, methanol was
refreshed every 8 h. Each sample was then charged into a sample
tube and activated at different temperatures (120, 80, and 1008C
[7] a) P. Nugent, Y. Belmabkhout, S. D. Burd, A. J. Cairns, R. Luebke, K. Forr-
est, T. Pham, S. Ma, B. Space, L. Wojtas, M. Eddaoudi, M. J. Zaworotko,
Chem. Eur. J. 2016, 22, 6277 – 6285
www.chemeurj.org
6284
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Nature 2013, 495, 80–84; b) S. D. Burd, S. Ma, J. A. Perman, B. J. Sikora,
R. Q. Snurr, P. K. Thallapally, J. Tian, L. Wojtas, M. J. Zaworotko, J. Am.
Chem. Soc. 2012, 134, 3663–3666; c) T. K. Prasad, M. P. Suh, Chem. Eur. J.
2012, 18, 8673–8680; d) L. Du, Z. Lu, K. Zheng, J. Wang, X. Zheng, Y.
Pan, X. You, J. Bai, J. Am. Chem. Soc. 2013, 135, 562–565.
O’Keeffe, O. Terasaki, J. F. Stoddart, O. M. Yaghi, Science 2012, 336,
1018–1023; b) Y. Yan, S. Yang, A. J. Blake, W. Lewis, E. Poirier, S. A. Bar-
nett, N. R. Champness, M. Schrçder, Chem. Commun. 2011, 47, 9995–
9997; c) X. Lin, I. Telepeni, A. J. Blake, A. Dailly, C. M. Brown, J. M. Sim-
mons, M. Zoppi, G. S. Walker, K. M. Thomas, T. J. Mays, P. Hubberstey,
N. R. Champness, M. Schrçder, J. Am. Chem. Soc. 2009, 131, 2159–2171;
d) T. Li, M. T. Kozlowski, E. A. Doud, M. N. Blakely, N. L. Rosi, J. Am. Chem.
Soc. 2013, 135, 11688–11691.
[8] a) O. K. Farha, I. Eryazici, N. C. Jeong, B. G. Hauser, C. E. Wilmer, A. A. Sar-
jeant, R. Q. Snurr, S. T. Nguyen, A. O. Yazaydin, J. T. Hupp, J. Am. Chem.
Soc. 2012, 134, 15016–15021; b) H. Furukawa, K. E. Cordova, M.
O’Keeffe, O. M. Yaghi, Science 2013, 341, 1230444; c) D. Yuan, D. Zhao,
D. Sun, H. C. Zhou, Angew. Chem. Int. Ed. 2010, 49, 5357–5361; Angew.
Chem. 2010, 122, 5485–5489.
[9] a) J. Duan, Z. Yang, J. Bai, B. Zheng, Y. Li, S. Li, Chem. Commun. 2012, 48,
3058–3060; b) Z. Y. Lu, H. Xing, R. Sun, J. F. Bai, B. S. Zheng, Y. Z. Li,
Cryst. Growth Des. 2012, 12, 1081–1084; c) R. Sun, Y.-Z. Li, J. Bai, Y. Pan,
Cryst. Growth Des. 2007, 7, 890–894; d) R. Sun, S. Wang, H. Xing, J. Bai,
Y. Li, Y. Pan, X. You, Inorg. Chem. 2007, 46, 8451–8453; e) K. Tang, R.
Yun, Z. Lu, L. Du, M. Zhang, Q. Wang, H. Liu, Cryst. Growth Des. 2013,
13, 1382–1385; f) B. Zheng, J. Bai, J. Duan, L. Wojtas, M. J. Zaworotko, J.
Am. Chem. Soc. 2011, 133, 748–751; g) B. Zheng, Z. Yang, J. Bai, Y. Li, S.
Li, Chem. Commun. 2012, 48, 7025–7027.
[17] a) Y. Yan, X. Lin, S. Yang, A. J. Blake, A. Dailly, N. R. Champness, P. Hub-
berstey, M. Schrçder, Chem. Commun. 2009, 1025–1027; b) D. Zhao, D.
Yuan, D. Sun, H. C. Zhou, J. Am. Chem. Soc. 2009, 131, 9186–9188; c) R.
Grünker, V. Bon, A. Heerwig, N. Klein, P. Müller, U. Stoeck, I. A. Baburin,
U. Mueller, I. Senkovska, S. Kaskel, Chem. Eur. J. 2012, 18, 13299–13303.
[18] a) N. Klein, I. Senkovska, K. Gedrich, U. Stoeck, A. Henschel, U. Mueller, S.
Kaskel, Angew. Chem. Int. Ed. 2009, 48, 9954–9957; Angew. Chem. 2009,
121, 10139–10142; b) I. Senkovska, S. Kaskel, Chem. Commun. 2014, 50,
7089–7098; c) J. An, O. K. Farha, J. T. Hupp, E. Pohl, J. I. Yeh, N. L. Rosi,
Nat. Commun. 2012, 3, 604; d) K. Wang, D. Feng, T. F. Liu, J. Su, S. Yuan,
Y. P. Chen, M. Bosch, X. Zou, H. C. Zhou, J. Am. Chem. Soc. 2014, 136,
13983–13986; e) K. Koh, A. G. Wong-Foy, A. J. Matzger, Angew. Chem.
Int. Ed. 2008, 47, 677–680; Angew. Chem. 2008, 120, 689–692.
[19] H. Furukawa, N. Ko, Y. B. Go, N. Aratani, S. B. Choi, E. Choi, A. O. Yazay-
din, R. Q. Snurr, M. O’Keeffe, J. Kim, O. M. Yaghi, Science 2010, 329, 424–
428.
[10] a) D. Li, H. Furukawa, H. Deng, C. Liu, O. M. Yaghi, D. S. Eisenberg, Proc.
Natl. Acad. Sci. USA 2014, 111, 191–196; b) D. Peri, J. Ciston, F. Gandara,
Y. Zhao, O. M. Yaghi, Inorg. Chem. 2013, 52, 13818–13820; c) P. Vairapra-
kash, H. Ueki, K. Tashiro, O. M. Yaghi, J. Am. Chem. Soc. 2011, 133, 759–
761; d) J. Bonnefoy, A. Legrand, E. A. Quadrelli, J. Canivet, D. Farrusseng,
J. Am. Chem. Soc. 2015, 137, 9409–9416.
[20] G. Ferey, C. Mellot-Draznieks, C. Serre, F. Millange, J. Dutour, S. Surble, I.
Margiolaki, Science 2005, 309, 2040–2042.
[11] a) M. Eddaoudi, J. Kim, N. Rosi, D. Vodak, J. Wachter, M. O’Keeffe, O. M.
Yaghi, Science 2002, 295, 469–472; b) O. M. Yaghi, M. O’Keeffe, N. W.
Ockwig, H. K. Chae, M. Eddaoudi, J. Kim, Nature 2003, 423, 705–714;
c) H. Furukawa, Y. B. Go, N. Ko, Y. K. Park, F. J. Uribe-Romo, J. Kim, M.
O’Keeffe, O. M. Yaghi, Inorg. Chem. 2011, 50, 9147–9152.
[21] Y. S. Bae, K. L. Mulfort, H. Frost, P. Ryan, S. Punnathanam, L. J. Broadbelt,
J. T. Hupp, R. Q. Snurr, Langmuir 2008, 24, 8592–8598.
[22] Z. Zhang, Z. Li, J. Li, Langmuir 2012, 28, 12122–12133.
[23] T. Li, D.-L. Chen, J. E. Sullivan, M. T. Kozlowski, J. K. Johnson, N. L. Rosi,
Chem. Sci. 2013, 4, 1746–1755.
[12] T. Devic, O. David, M. Valls, J. Marrot, F. Couty, G. Ferey, J. Am. Chem.
Soc. 2007, 129, 12614–12615.
[13] a) J. Park, J. R. Li, Y. P. Chen, J. Yu, A. A. Yakovenko, Z. U. Wang, L. B. Sun,
P. B. Balbuena, H. C. Zhou, Chem. Commun. 2012, 48, 9995–9997; b) P.
Zhang, B. Li, Y. Zhao, X. Meng, T. Zhang, Chem. Commun. 2011, 47,
7722–7724.
[24] a) J. A. Mason, K. Sumida, Z. R. Herm, R. Krishna, J. R. Long, Energy Envi-
ron. Sci. 2011, 4, 3030–3040; b) D. Saha, Z. Bao, F. Jia, S. Deng, Environ.
Sci. Technol. 2010, 44, 1820–1826.
[25] Z. Zhang, Y. Zhao, Q. Gong, Z. Li, J. Li, Chem. Commun. 2013, 49, 653–
661.
[26] B. Li, Z. Zhang, Y. Li, K. Yao, Y. Zhu, Z. Deng, F. Yang, X. Zhou, G. Li, H.
Wu, N. Nijem, Y. J. Chabal, Z. Lai, Y. Han, Z. Shi, S. Feng, J. Li, Angew.
Chem. Int. Ed. 2012, 51, 1412–1415; Angew. Chem. 2012, 124, 1441–
1444.
[27] P. L. Llewellyn, S. Bourrelly, C. Serre, A. Vimont, M. Daturi, L. Hamon, G.
De Weireld, J. S. Chang, D. Y. Hong, Y. Kyu Hwang, S. Hwa Jhung, G.
Ferey, Langmuir 2008, 24, 7245–7250.
[14] V. Guillerm, D. Kim, J. F. Eubank, R. Luebke, X. Liu, K. Adil, M. S. Lah, M.
Eddaoudi, Chem. Soc. Rev. 2014, 43, 6141–6172.
[15] a) J. Lu, A. Mondal, B. Moulton, M. J. Zaworotko, Angew. Chem. Int. Ed.
2001, 40, 2113–2116; Angew. Chem. 2001, 113, 2171–2174; b) J. J. t.
Perry, V. Kravtsov, G. J. McManus, M. J. Zaworotko, J. Am. Chem. Soc.
2007, 129, 10076–10077; c) A. J. Cairns, J. A. Perman, L. Wojtas, V. Kravt-
sov, M. H. Alkordi, M. Eddaoudi, M. J. Zaworotko, J. Am. Chem. Soc.
2008, 130, 1560–1561.
[16] a) H. Deng, S. Grunder, K. E. Cordova, C. Valente, H. Furukawa, M.
Hmadeh, F. Gandara, A. C. Whalley, Z. Liu, S. Asahina, H. Kazumori, M.
Received: December 5, 2015
Published online on March 31, 2016
Chem. Eur. J. 2016, 22, 6277 – 6285
www.chemeurj.org
6285
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