Introduction of functionality, selection of topology, and enhancement of gas adsorption in multivariate metal-organic framework-177

Article abstract of DOI:10.1021/ja512311a

Metal-organic framework-177 (MOF-177) is one of the most porous materials whose structure is composed of octahedral Zn₄O(-COO)₆ and triangular 1,3,5-benzenetribenzoate (BTB) units to make a three-dimensional extended network based on the qom topology. This topology violates a long-standing thesis where highly symmetric building units are expected to yield highly symmetric networks. In the case of octahedron and triangle combinations, MOFs based on pyrite (pyr) and rutile (rtl) nets were expected instead of qom. In this study, we have made 24 MOF-177 structures with different functional groups on the triangular BTB linker, having one or more functionalities. We find that the position of the functional groups on the BTB unit allows the selection for a specific net (qom, pyr, and rtl), and that mixing of functionalities (-H, -NH₂, and -C₄H₄) is an important strategy for the incorporation of a specific functionality (-NO₂) into MOF-177 where otherwise incorporation of such functionality would be difficult. Such mixing of functionalities to make multivariate MOF-177 structures leads to enhancement of hydrogen uptake by 25%.

Full text of DOI:10.1021/ja512311a

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Article
Introduction of Functionality, Selection of Topology, and Enhancement
of Gas Adsorption in Multivariate Metal–Organic Framework-177
Yue-Biao Zhang, Hiroyasu Furukawa, Nakeun Ko, Weixuan Nie, Hye Jeong Park,
Satoshi Okajima, Kyle E. Cordova, Hexiang Deng, Jaheon Kim, and Omar M. Yaghi
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/ja512311a • Publication Date (Web): 03 Feb 2015
Downloaded from http://pubs.acs.org on February 9, 2015
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Journal of the American Chemical Society
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Introduction of Functionality, Selection of Topology, and En-
hancement of Gas Adsorption in Multivariate Metal–Organic
Framework-177
0
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†
†
‡
†
‡
†
†,□
Yue-Biao Zhang, Hiroyasu Furukawa, Nakeun Ko, Weixuan Nie, Hye Jeong Park, Satoshi Okajima, Kyle E. Cordova,
,
†,§
,‡
,†,¶
Hexiang Deng,* Jaheon Kim,* and Omar M. Yaghi*
†
Department of Chemistry, University of California−Berkeley, Materials Sciences Division, Lawrence Berkeley National Laboratory,
and Kavli Energy NanoSciences Institute at Berkeley, University of California−Berkeley, Berkeley, California 94720, United States
‡
Department of Chemistry, Soongsil University, Seoul 156-743, Republic of Korea
§
College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China
□
Center for Molecular and NanoArchitecture, Vietnam National University, Ho Chi Minh City 721337, Vietnam
¶
King Abdulaziz City for Science and Technology, Riyadh 11442, Saudi Arabia
ABSTRACT: Metal–organic framework-177 (MOF-177) is one of the most porous materials whose structure is composed of octahedral
Zn
4
O(-COO) and triangular 1,3,5-benzenetribenzoate (BTB) units to make a three-dimensional extended network based on the qom to-
6
pology. This topology violates a long-standing thesis where highly symmetric building units are expected to yield highly symmetric networks.
In the case of octahedron and triangle combination, MOFs based on the pyrite (pyr) and rutile (rtl) nets were expected instead of qom. In
this study, we have made twenty-four MOF-177 structures with different functional groups on the triangular BTB linker having one or more
functionalities. We find that the position of the functional groups on the BTB unit allows the selection for a specific net (qom, pyr and rtl),
and that mixing of functionalities (-H, -NH
2
, and -C
4
H
4
) is an important strategy for the incorporation of a specific functionality (-NO ) into
2
MOF-177 where otherwise incorporation of such functionality would be difficult. Such mixing of functionalities to make multivariate MOF-
177 structures leads to enhancement of hydrogen uptake by 25%.
MOFs based on qom are found to have ultrahigh porosity and
exhibit useful gas storage behavior. This is in contrast to the unex-
INTRODUCTION
8
Generally, in the reticular chemistry of metal–organic frame-
ceptional behavior exhibited by MOFs based on the default nets
1
9
works (MOFs) where highly symmetric building units are used,
(
pyr and rtl). Therefore, we sought to investigate this system with
MOFs having the most symmetric nets are expected to form
the aim of (a) elaborating our original thesis of high-symmetry and
default nets, (b) providing insight into the design principles of
MOFs, and (c) showing how these could be used to further im-
prove properties of MOF-177 and other related systems.
(
termed default nets). An analysis of MOFs in the Cambridge
Structural Database revealed that over 80% of all structures belong
2
to a handful of these default nets. For example, the assembly of
tetrahedra usually leads to MOFs having the diamond net, and the
assembly of triangles gives the silicon net of SrSi
nets are the default nets for the assembly of tetrahedra or triangles
and they happen to be the most symmetric nets among a large
number of possible nets. Indeed, this principle of high symmetry
and default nets is applicable to the assembly of MOFs from other
shapes as well as those involving mixed shapes, and it has become a
useful guide in the design and synthesis of MOFs. One of the most
striking exceptions to this principle is the structure of MOF-177,
which is constructed from the octahedral Zn
gular 1,3,5-benzenetribenzoate (BTB) units to form the qom net, a
lower symmetry net, instead of one of the default high symmetry
nets (Scheme 1), pyrite (pyr) or rutile (rtl). The importance of this
observation is underlined by the pervasiveness of the qom net
when linking these shapes and expanding them as is the case with
3
In this study, we present two approaches in which we assess the
tolerance of the qom net to functionalization of the organic linker
and the mixing of linkers bearing different functionalities. We find
that the position of functional groups on the linker is critical in
selecting for qom net versus pyr and rtl nets, and that mixing of
linkers exclusively affords the qom net. Specifically, eleven deriva-
4
2
; both of these
tives of the BTB linker (BTB-X: -H, A; -NH
D; -OC , E; -(F) , F; -C , G; -F, H; -CH
/NH , K in Scheme 2, respectively) were designed and syn-
2
, B; -NO
2
, C; -OCH
3
,
5
7
H
7
2
4
H
4
3
, I; -mNH
2
, J; -
C
4
H
4
2
4
O(-COO) and trian-
6
thesized. With the exception of linker C, all linkers have been suc-
cessfully used alone to make isoreticular MOF-177 structures. Sin-
gle-crystal X-ray structures of the obtained MOF-177-X (X = B, D,
E, F, G, H, I, J, and K; Scheme 2) were found to have 3D frame-
works with the same underlying qom net, yet bared different func-
tionalities. When using linker F or J alone, isomeric MOFs based
on the pyr (MOF-155-F and MOF-155-J) or rtl (MOF-156-J) nets
6
7
its isoreticular forms, MOF-180 and MOF-200. Furthermore,
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with the same framework formula of Zn O(BTB-X) were also anhydrous N,N-dimethylformamide (DMF) was obtained from
4
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observed as a second phase or byproduct. Furthermore, by mixing
EMD Chemicals; anhydrous acetone (purity ≥ 99.8%, extra dry
with AcroSeal) was purchased from Acros Organics; chloroform
(pentene stabilized, HPLC grade) and anhydrous dichloromethane
(purity ≥ 99.8%; amylene stabilized) were purchased from Sigma-
Aldrich Co. and Fisher Scientific, respectively. N,N-
Diethylformamide (DEF) was provided by BASF SE (Ludwigsha-
fen, Germany), which was further purified through treatment with
two or three different type of linkers, fourteen multivariate
10
(
MTV) MTV-MOF-177 derivatives with the same underlying
qom net, but with varied ratios of incorporated functionalities were
prepared (Scheme 2): MTV-MOF-177-AB, Zn
NH -AC, Zn O(BTB)1.69(BTB-NO
Zn O(BTB)1.37(BTB-OCH -AE, Zn O(BTB)1.54(BTB-
OC -AF1, Zn O(BTB)1.46[BTB-(F)
Zn O(BTB)1.21[BTB-(F) 0.79; -AG, Zn O(BTB)1.29(BTB-C
AH, Zn O(BTB)1.17(BTB-F)0.83 -AI, Zn O(BTB)1.17(BTB-
CH 0.83; -AJ, Zn O(BTB)1.40(BTB-mNH 0.60; -BC, Zn
NH 1.18(BTB-NO 0.82; -BG, Zn O(BTB-NH 1.04(BTB-C
0.62(BTB-C
0.31(BTB-C
4
O(BTB)1.43(BTB-
2
)
0.57
;
4
2
)
0.31
;
-AD,
4
3
)
0.63
;
4
7
H
7
)
0.46
;
4
2
]
0.54
;
-AF2,
charcoal followed by reduced-pressure distillation. H
3
BTB was
4
2
]
4
4
H
4
)
0.71
;
purchased from TCI America. The H BTB functionalized linkers
3
0
1
2
3
4
5
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7
8
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3
4
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9
0
-
4
;
4
were prepared through Suzuki-Miyaura coupling reactions as de-
tailed in the Supporting Information (SI, Section S1). All starting
materials and solvents, except DEF, were used without further puri-
fication.
3
)
)
CG,
4
2
)
4
O(BTB-
2
2
)
4
2
)
4
H
4
0.96
) ;
-
Zn
Zn
4
O(BTB-NO
2
)
4
H
4
)
1.38
;
and
-ABG,
4
O(BTB)1.03(BTB-NH
2
)
4
H
4
)
0.66. The crystal struc-
1
H NMR spectra were acquired on a Bruker AVB-400 NMR
tures and chemical formulae of these MTV-MOF-177 derivatives
spectrometer. Elemental microanalyses (EA) were performed in
the Microanalytical Laboratory of the College of Chemistry at UC
Berkeley, using a Perkin Elmer 2400 Series II CHNS elemental
analyzer. Mass spectra (MS) were obtained from the chemistry
mass spectrometry facility in the QB3 Laboratory at UC Berkeley.
Attenuated total reflectance Fourier transform infrared (ATR-
FTIR) spectra of neat samples were recorded on a Bruker ALPHA
Platinum ATR-FTIR Spectrometer equipped with a single reflec-
tion diamond ATR module. Thermal gravimetric analysis (TGA)
curves were taken using a TA Q500 thermal analysis system with
were determined by elemental analysis, powder X-ray diffraction
1
(
PXRD) techniques, and H nuclear magnetic resonance (NMR)
spectroscopy. Among them, five fully functionalized MOF-177
(
MOF-177-B, -D, -F, and -I) analogs and seven MTV-MOF-177
(
MTV-MOF-177-AB, -AD, -AE, -AF1, -AF2, -AH, and -ABG)
derivatives were selected for gas adsorption studies and their per-
formance was compared with the parent, unfunctionalized MOF-
1
77 architecture (MOF-177-A). MOF-177-B and MOF-177-D
exhibit 25% higher volumetric hydrogen uptake than that of MOF-
77-A.
Scheme 1.
1
the heating rate of 5 °C/min under N or air flow (SI, Section S4).
2
a
Low-pressure adsorption isotherms were recorded on a Quad-
rasorb-SI or an Autosorb-1 (Quantachrome) volumetric gas ad-
sorption analyzer. Liquid nitrogen and argon baths were used for
the measurements at 77 and 87 K, respectively. Ultra-high-purity
grade N
2
, Ar, and H gases (Praxair, 99.999% purity) were used for
2
the adsorption measurements. Helium (Praxair, 99.999% purity)
was used for the estimation of dead space throughout all adsorption
measurements.
X-ray Diffraction Analyses. Single-crystal X-ray diffraction
SXRD) data of MOFs, unless otherwise mentioned, were collect-
(
ed on a Bruker diffractometer using Cu K radiation ( = 1.54178
Å). Diffraction data for MOF-177-G was collected in the beamline
1
1.3.1 of the Advanced Light Source at Lawrence Berkeley Nation-
al Laboratory, and diffraction data for MOF-156, MOF-157, and
MOF-177-J were collected in Pohang Accelerator Laboratory (Re-
public of Korea) using synchrotron radiation. Powder X-ray diffrac-
tion (PXRD) patterns were recorded using a Bruker D8 Advance
diffractometer with Cu K radiation ( = 1.54056 Å).
General Preparation and Activation of MOF Materials. To
minimize the number of factors (including concentration, solvent,
temperature, and time of reaction) that can affect the formation of
the qom topology, syntheses of the isoreticular MOF-177-X and
MTV-MOF-177 compounds were carried out under similar reac-
tion conditions as those employed for MOF-177-A (i.e. parent
MOF-177). In general, these MOFs were prepared by solvothermal
reaction of a mixture containing the appropriate BTB linker(s),
aThree possible (6,3)-coordinated nets formed from octahedra and
triangles building units with alternative arrangement. pyr and rtl are
two of the default (6,3)-coordinated nets that have only two kind of
vertices and one kind of edge, and two kind of vertices and two kind of
edges, respectively. qom is the underlying net in MOF-177 that has five
kind of vertices (three triangles and two octahedra) and five kind of
edges.
Zn(NO
3
)
2
∙6H O, and DEF. However, to improve the quality of
2
crystals, concentration of starting materials, solvent, reaction tem-
perature, and/or reaction time were slightly modified as required.
The resulting crystalline products were isolated by decanting the
mother liquor and were subsequently washed with fresh solvent.
EXPERIMENTAL SECTION
Starting Materials and General Procedures. Zinc nitrate hex-
ahydrate, Zn(NO
3
)
2
·6H O, was purchased from Fisher Scientific;
2
2
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Scheme 2.
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aBTB linkers with various functional groups at selected positions and the corresponding MOFs formed either by pure linker or mixing of various link-
ers. H BTB (A); H BTB-NH , 1,3,5-tris(3-amino-4-carboxyphenyl)benzene (B); H BTB-NO , 1,3,5-tris(3-nitro-4-carboxyphenyl)benzene (C);
BTB-OCH , 1,3,5-tris(3-methoxy-4-carboxyphenyl)benzene (D); H BTB-OC , 1,3,5-tris(3-benzyloxy-4-carboxyphenyl)benzene (E); H BTB-
(F) , 1,3,5-tris(3,5-difluoro-4-carboxyphenyl)benzene (F); H BTB-C , 1,3,5-tris(4-carboxy-naphthalen-1-yl)benzene (G); H BTB-F, 1,3,5-tris(3-
fluoro-4-carboxyphenyl)benzene (H); BTB-CH 1,3,5-tris(3-methyl-4-carboxyphenyl)benzene (I); BTB-mNH 1,3,5-tris(2-amino-4-
carboxyphenyl)benzene, (J); H BTB-C /NH
3
3
2
3
2
H
3
3
3
7
H
7
3
2
3
4
H
4
3
H
3
3
,
H
3
2
,
3
4
H
4
2
, 1-(3-amino-4-carboxyphenyl)-3-(4-carboxyphenyl)-5-(4-carboxynaphthalen-1-yl)-benzene (K).
6
Removal of guest molecules within the MOF materials’ pores
began with a solvent exchange procedure that included immersing
the as-synthesized samples into anhydrous DMF (typically 10 mL)
and refreshing the DMF three times over the course of three days.
Further solvent exchange, but this time with low boiling point sol-
vents, was carried out in a similar fashion (three times over the
dure.
MOF-177-B, Zn
B (12 mg, 0.025 mmol) and Zn(NO
4
O(BTB-NH
2
)
2
. A mixture of the acid form of
·6H O (63 mg, 0.22 mmol)
3
)
2
2
was dissolved in 10 mL of DEF in a 20 mL vial, which was heated at
85 °C for 48 h. Yellow block-shaped crystals were isolated and
washed with DEF (3 × 5 mL). To yield guest-free material, the as-
synthesized washed sample was fully exchanged with anhydrous
DMF (3 × 10 mL for 3 days), followed with anhydrous acetone (3
× 10 mL for 3 days), and finally activated by the SCD method. EA
for the activated sample of MOF-177-B: Calcd. for
1
1
course of three days). For typical activation, a MOF sample was
fully exchanged with chloroform or dichloromethane (10 mL) and
evacuated at room temperature for 6 h and at 100 °C for an addi-
1
2
tional 18 h. For supercritical CO
MOF sample was fully immersed in anhydrous acetone and thor-
oughly exchanged with liquid CO in the chamber of a Tousimis
Samdri PVT-3D critical point dryer. The sample was subsequently
kept in a supercritical CO atmosphere (typical conditions of 35 °C
and 1200 psi) for 30 min and then the supercritical CO was slowly
vented at room temperature over the course of several hours.
MOF-177-A, Zn O(BTB) . The synthesis of the parent MOF-
77 structure constructed from unfunctionalized H BTB and
Zn(NO ·6H O was carried out according to a published proce-
2
drying (SCD) activation, a
Zn
4
C
54
H
42
N
6
O
13 = Zn
4
O(BTB-NH ) : C, 52.37; H, 2.93; N, 6.79%.
2
2
2
Found: C, 50.12; H, 3.36; N, 5.57%.
MOF-177-C. The synthesis of MOF-177-C was unsuccessful
even after extensive efforts were undertaken involving the manipu-
lation of all the synthetic variables mentioned above.
2
2
MOF-177-D, Zn
of D (53 mg, 0.10 mmol) and Zn(NO
mmol) was dissolved in 10 mL DEF in a 20 mL vial, which was
heated at 100 °C for 20 h. Colorless block-shaped crystals were
4
O(BTB-OCH
3
)
2
. A mixture of the acid form
·6H O (250 mg, 0.840
4
2
3
)
2
2
1
3
3
)
2
2
3
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isolated and washed with DEF (3 × 5 mL). To yield guest-free ma-
2.93; N, 6.79%. Found: C, 51.63; H, 3.05; N, 6.75%.
MOF-177-K, Zn O(BTB-C /NH . A mixture of the acid
form of K (25 mg, 0.050 mmol) and Zn(NO ·6H O (125 mg,
.420 mmol) was dissolved in 10 mL DEF in a 20 mL vial, which
was heated at 100 °C for 48 h. Yellow block-shaped crystals were
isolated and washed with DEF (3 × 5 mL).
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
terial, the as-synthesized sample was fully exchanged with chloro-
form (3 × 10 mL for 3 days) and further activated by the conven-
tional method. EA for the activated sample of MOF-177-D: Calcd.
4
4
H
4
)
2 2
3
)
2
2
0
for Zn
Found: C, 52.67; H, 2.59; N, < 0.2%.
MOF-177-E, Zn O(BTB-OC
of E (76 mg, 0.10 mmol) and Zn(NO
4
C
60
H
42
O
19 = Zn
4
O(BTB-OCH ) : C, 54.24; H, 3.19%;
3
2
4
7
H
7
)
2
. A mixture of the acid form
·6H O (250 mg, 0.840
MOF-155-F, Zn
F (54 mg, 0.10 mmol) and Zn(NO
4
O[BTB-(F)
2
]
2
3
. A mixture of the acid form of
·6H O (250 mg, 0.840 mmol)
3
)
2
2
)
2
2
mmol) was dissolved in 10 mL DEF in a 20 mL vial, which was
heated at 100 °C for 20 h. Colorless block-shaped crystals were
isolated and washed with DEF (3 × 5 mL). EA for the as-
was dissolved in 10 mL DEF in a 20 mL vial, which was heated at
5 °C for 48 h. Colorless cubic-shaped crystals were isolated and
washed with DEF (3 × 5 mL).
MOF-155-J, Zn O(BTB-mNH
of J (54 mg, 0.10 mmol) and Zn(NO
8
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
synthesized sample of MOF-177-E: Calcd. for Zn
Zn O(BTB-OC ·(DEF)13: C, 62.38; H, 6.80; N, 5.87%. Found:
C, 61.52; H, 6.93; N, 5.98%.
MOF-177-F, Zn O[BTB-(F)
F (27 mg, 0.050 mmol) and Zn(NO
4
C
161
H
209
N
13
O
32
=
4
2
)
2
. A mixture of the acid form
·6H O (250 mg, 0.840
4
7
H )
7 2
3
)
2
2
mmol) was dissolved in 10 mL DMF in a 20 mL vial, which was
heated at 85 °C for 48 h. Colorless cubic-shaped crystals were iso-
lated as a byproduct of MOF-177-J.
4
2
]
2
. A mixture of the acid form of
·6H O (125 mg, 0.420
3
)
2
2
mmol) was dissolved in 10 mL DEF in a 20 mL vial, which was
heated at 100 °C for 48 h. Colorless block-shaped crystals were
isolated and washed with DEF (3 × 5 mL). To yield guest-free ma-
terial, the as-synthesized sample was fully exchanged with anhy-
drous dichloromethane (3 × 10 mL for 3 days) and further activat-
ed by the conventional method. EA for the activated MOF-177-F:
MOF-156-J, Zn
of J (43.5 mg, 0.090 mmol) and Zn(NO
4
O(BTB-mNH
2
)
2
. A mixture of the acid form
·6H O (200 mg, 0.672
3
)
2
2
mmol) was dissolved in DEF/MeOH (15 mL/1.5 mL) in a 20-mL
vial, which was heated at 95 °C for 24 h. Yellow rod-shaped crystals
were isolated and washed with DMF (3 × 20 mL). EA for the acti-
vated sample of MOF-156-J: Calcd. for Zn
Zn O(BTB-mNH : C, 52.37; H, 2.93; N, 6.79%. Found: C, 51.66;
H, 2.96; N, 6.57%.
MTV-MOF-177-XY (XY = AB, AC, AD, AE, AF1, AG, AH,
AI, AJ, BC, BG, and CG), Zn O(BTB-X)
Equimolar amounts of H BTB-X and -Y (0.050 mmol; 22 mg for A,
4 mg for B, 29 mg for C, 26 mg for D, 38 mg for E, 27 mg for F1,
9 mg for G, 25 mg for H, 24 mg for I, 24 mg for J) and
·6H O (250 mg, 0.840 mmol) in 10 mL DEF were
4
C
54
H
42
N
6
O
13
=
Calcd. for Zn
1.33%. Found: C, 47.03; H, 0.91; N, < 0.2%.
MOF-177-G, Zn O(BTB-C . A mixture of the acid form
of G (30 mg, 0.050 mmol) and Zn(NO ·6H O (125 mg, 0.420
4
C
54
H
18
O
13
F12 = Zn
4
O[BTB-(F)
2
]
2
: C, 47.54; H,
4
)
2 2
4
4
H
)
4 2
3
)
2
2
4
n
(BTB-Y)(2-n).
mmol) was dissolved in 10 mL DEF in a 20 mL vial, which was
heated at 100 °C for 48 h. Colorless block-shaped crystals were
isolated and washed with DEF (3 × 5 mL for 3 days). EA for the as-
3
2
2
synthesized sample of MOF-177-G: Calcd. for Zn
Zn O(BTB-C ·(DEF)16: C, 61.87; H, 7.16; N, 7.31%. Found:
C, 60.36; H, 7.42; N, 7.59%.
MOF-177-H, Zn O(BTB-F)
30 mg, 0.050 mmol) and Zn(NO
was dissolved in 10 mL DEF in a 20 mL vial, which was heated at
00 °C for 48 h. Colorless block-shaped crystals were isolated and
washed with DEF (3 × 5 mL for 3 days). EA for the as-synthesized
sample of MOF-177-H: Calcd. for Zn
Zn O(BTB-F) ·(DEF)15: C, 55.86; H, 6.87; N, 7.58%. Found: C,
4.71; H, 6.60; N, 7.63%.
MOF-177-I, Zn O(BTB-CH
I (24 mg, 0.050 mmol) and Zn(NO
4
C
158
H
218
N
16
O
29
Zn(NO
3
)
2
2
=
4
4
H )
4 2
placed in a 20 mL vial, which was heated at 100 °C for 24 h. Ob-
tained crystals were washed with DEF (3 × 5 mL).
4
2
. A mixture of the acid form of H
·6H O (125 mg, 0.420 mmol)
EA data for the as-synthesized samples.
(
3
)
2
2
MOF-177-AB:
Zn O(BTB)1.43(BTB-NH
.70%. Found: C, 56.43; H, 7.58; N, 8.74%.
MOF-177-AC: Calcd. for Zn
Zn O(BTB)1.69(BTB-NO 0.31·(DEF)15: C, 57.23; H, 7.22, N,
8.24%. Found: C, 55.96; H, 7.53, N, 8.33%.
MOF-177-AD: Calcd. for Zn
Zn O(BTB)1.37(BTB-OCH 0.63·(DEF)15: C, 57.75; H, 7.36; N,
7.72%. Found: C, 56.52; H, 7.73; N, 8.09%.
MOF-177-AE: Calcd. for Zn
Zn O(BTB)1.54(BTB-OC 0.46·(DEF)13: C, 59.21; H, 7.00; N,
.98%. Found: C, 61.52; H, 6.93; N, 5.98%.
MOF-177-AF1: Calcd. for Zn
Zn O(BTB)1.46(BTB-(F) 0.54·(DEF)15: C, 56.88; H, 7.10; N,
.71%. Found: C, 55.51; H, 7.58; N, 7.77%.
MOF-177-AG: Calcd. for Zn
Zn O(BTB)1.29(BTB-C 0.71·(DEF)14: C, 59.59; H, 7.10; N,
7.34%. Found: C, 58.63; H, 7.64; N, 7.61%.
MOF-177-AH: Calcd. for Zn
Zn
Found: C, 55.87; H, 7.62; N, 7.96%.
Calcd.
for
Zn
4
C
129
H
196.71
N
16.71
O
28
=
4
2
)
0.57·(DEF)15: C, 57.57; H, 7.37; N,
1
8
4
C
129
H
189
N
15
O
28
F
6
=
4
C
129
194.07
H N
15.93
O
29.86
=
4
2
4
2
)
5
4
3
)
2
. A mixture of the acid form of
·6H O (125 mg, 0.420 mmol)
4
C
130.89
H
198.78
N
15
O
29.89
=
3
)
2
2
4
3
)
was dissolved in 10 mL DEF in a 20 mL vial, which was heated at
100 °C for 48 h. Colorless block-shaped crystals were isolated and
washed with DEF (3 × 5 mL). To yield guest-free material, the as-
synthesized sample was fully exchanged with anhydrous dichloro-
methane (3 × 10 mL for 3 days) and further activated by the con-
ventional method. EA for the activated MOF-177-I: Calcd. for
4
C
128.66
H
181.28
N
13
O
27.38
=
4
7
7
H )
6
4
C
129
191.76
H N
15
O
28
F
3.24
=
4
2
)
Zn
6.12; H, 2.73; N, < 0.2%.
MOF-177-J, Zn O(BTB-mNH
of J (44 mg, 0.090 mmol) and Zn(NO
4
C
60
H
42
O
13 = Zn
4
O(BTB-CH ) : C, 58.47; H, 3.43%. Found: C,
3
2
7
5
4
C
132.52
H
188.26
N
14
O
27
=
4
2
)
2
. A mixture of the acid form
·6H O (200 mg, 0.672
4
4
4
H )
3
)
2
2
mmol) was dissolved in a mixture of DMF/NMP/EtOH (7.5
mL/7.5 mL/1.5 mL) in a 20 mL vial, which was heated at 95 °C for
4
C
124
181.51
H N
14
O
27
F
2.49
=
4
O(BTB)1.17(BTB-F)0.83·(DEF)14: C, 57.08; H, 7.01; N, 7.52%.
2
4 h. Yellow hexagonal plate crystals were isolated and washed with
DMF (3 × 5 mL). EA for the activated sample of MOF-177-J:
Calcd. for Zn O(BTB-mNH : C, 52.37; H,
4
C
54
H
42
N
6
O
13 = Zn
4
)
2 2
4
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Journal of the American Chemical Society
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
Figure 1. Crystal structures of MOF-177compounds synthesized from linkers with various functional groups. All of these MOFs made of pure linkers
have the same qom topology as MOF-177. Atom colors: C, black; O, red; N, blue; F, light green; Zn, blue polyhedra; H atoms were omitted for clari-
ty. Large color sphere represent voids in the structures.
MOF-177-AI:
Zn
Found: C, 57.44; H, 7.96; N, 7.95%.
MOF-177-AJ: Calcd. for
Zn O(BTB)1.40(BTB-mNH
.54%. Found: C, 55.63; H, 7.63; N, 8.98%.
MOF-177-BC: Calcd. for Zn
NH 0.82·(DEF)15: C, 54.76; H, 6.99; N, 10.40%.
Found: C, 52.94; H, 7.80; N, 10.12%.
MOF-177-BG: Calcd. for Zn
NH 0.96·(DEF)15: C, 59.08; H, 7.19; N, 8.88%.
Calcd.
for
Zn
4
C
126.49
H
188.98
N
15
O
27
=
(38 mg, 0.070 mmol) and Zn(NO
3
)
2
·6H O (250 mg, 0.840 mmol)
2
4
O(BTB)1.17(BTB-Me)0.83·(DEF)14: C, 58.45; H, 7.33; N, 7.54%.
was dissolved in 10 mL DEF in a 20 mL vial, which was heated at
100 °C for 24 h. Colorless block-shaped crystals were isolated and
washed with DEF (3 × 5 mL). EA for the as-synthesized sample of
Zn
4
C
124
H
185.8
N
15.8
O
27
=
MOF-177-AF2:
Zn O(BTB)1.21(BTB-(F)
.40%. Found: C, 55.09; H, 7.44; N, 7.70%. To yield guest-free
Calcd.
for
Zn
4
C
124
H
179.26
N
15
O
27
F
4.74
=
4
2
)0.60·(DEF)14: C, 57.47; H, 7.23; N,
4
2
)0.79·(DEF)14: Calcd. C, 56.21; H, 6.82; N,
8
7
4
C
129
H
196.08
N
21
O
32.92 = Zn O(BTB-
4
material, MOF-177-AF2 was fully exchanged with anhydrous ace-
tone (3 × 10 mL for 3 days) and further activated by the SCD
method.
2
)
1.18(BTB-NO )
2
4
C
140.52
H
203.88
N
18.2
O
28 = Zn O(BTB-
4
MTV-MOF-177-ABG, Zn
0.66. A mixture of the acid form of A (15 mg, 0.33 mmol), the
acid form of B (16 mg, 0.33 mmol), the acid form of G (19 mg,
.33 mmol), and Zn(NO ·6H O (250 mg, 0.840 mmol) was dis-
4
O(BTB)1.03(BTB-NH
2
)0.31(BTB-
2
)
1.04(BTB-C
4
H )
4
C
4
4
H )
Found: C, 57.02; H, 8.20; N, 8.75%.
MOF-177-CG: Calcd. for Zn
4
C
145.56
H
201.42
N
16.86
O
31.72
=
0
3
)
2
2
Zn
4
O(BTB-NO
2
)
0.62(BTB-C
4
H )1.38·(DEF)15: C, 59.13; H, 6.87; N,
4
solved in 10 mL DEF in a 20 mL vial, which was heated at 100 °C
for 24 h. Obtained crystals were washed with DEF (3 × 5 mL). To
yield guest-free material, MOF-177-ABG was fully exchanged with
anhydrous acetone (3 × 10 mL for 3 days) and further activated by
the SCD method. EA for activated sample of MOF-177-ABG:
7.99%. Found: C, 58.80; H, 7.48; N, 7.85%.
To yield guest-free materials, MOF-177-XY (-AB, -AC, -AD, -AE,
-
1
AF1, and -AG) were fully exchanged with anhydrous acetone (3 ×
0 mL for 3 days) and further activated by the SCD method.
MTV-MOF-177-AF2, Zn O(BTB)1.21(BTB-(F)
ture of the acid form of A (13 mg, 0.030 mmol), the acid form of F
Calcd. for Zn
NH
Found: C, 58.15; H, 2.19; N, 0.90%.
4
C
61.92
H
34.89
N
0.93
O
13
=
Zn
4
O(BTB)1.03(BTB-
4
2
)0.79. A mix-
2
)
0.31(BTB-C
4
4
H )0.66: Calcd. C, 58.96; H, 2.79; N, 1.03%.
5
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Journal of the American Chemical Society
Page 6 of 12
tive molecular mechanics calculation on a discrete BTB linker mol-
ecule suggested that even a small meta-NH group could impose a
RESULTS AND DISCUSSION
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
Design Strategy for the Functionalization of BTB Linkers. In
order to investigate the influence of linker functionalization on
MOF-177, we prepared ten different functionalized BTB linkers
that were chemically distinct and which had varying strength of
inductive effects and steric congestion (Scheme 2). All functionali-
ties incorporated were attached to the peripheral benzoate units as
opposed to the central benzene of the BTB linker. Eight of these
large energy barrier to the free rotation of the peripheral benzoate
unit (> 100 kcal/mol, Figure S16). The energy-minimal dihedral
angle between the peripheral benzoate and the central benzene in
the free molecule of linker J was found to be 65.2°, which is distinct-
ly different from that of the pristine linker A (41.7°).
In addition to steric congestion, we also note the influence that
inductive effects play when certain functionalized linkers are intro-
duced into the synthesis. In general, electron-withdrawing groups
will facilitate deprotonation (increase acidity), but meanwhile will
weaken the coordination ability of the carboxylate moiety of the
BTB derivatives were functionalized at the ortho-position (R
with additional R , Scheme 2) with electron-donating groups (-
NH , -OCH , -OC , and -CH ) or electron-withdrawing groups
-NO , -(F) , -C , and -F]. The sizes of the functional groups also
varied. Bulky substituents, such as -OC and -C , were chosen
to study steric effects. Furthermore, the same functional group (e.g.
NH ) was applied at different positions of the linker (ortho-, R
and meta-, R , for linker B and J, respectively) in order to study how
1
or
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
3
7
H
7
3
[
2
2
4
H
4
1
4
7
H
7
4
H
4
linker. For example, MOF-177-F, which incorporated the elec-
tron-withdrawing group -(F) , could only be realized using only
2
-
2
1
,
low concentrations of linker F. At higher concentrations, MOF-
155-F with pyr net was the predominate product. In the case of the
3
the conformation of the linker was imparted by functional groups at
stronger electron-withdrawing group, -NO , the reactivity of linker
2
these positions. This has been noted as critical for the design of
C was observed to be significantly lower than that of linker F,
which unfortunately prevented the realization of MOF-177-C even
after exhaustive efforts were undertaken. This observation is remi-
1
3
MOFs with different topologies. Finally, we further explored the
possibility of building the MOF-177 structure, with the qom net,
using a variety of functional groups on one linker (e.g. linker K with
niscent of the MOF-5 structure, in which the -NO
2
functionalized
-
H, -NH
2
and -C
4
4
H on each of the three peripheral benzoate units).
ditopic linker (the same functionality as in linker C) was unable to
1
0a
be introduced without the presence of a second ditopic linker. It
is plausible that the ortho-positioned -NO group is also capable of
orientating to other clusters, as was found in the Zn (-COO)10
cluster in MOF-123, rather than Zn O(-COO) , thus preventing
the formation of the MOF-177 structure.
Functionalization of the MOF-177 Structure. A series of nine
2
MOF-177-X structures, composed of only one type of linker, were
synthesized using the ten functionalized BTB linkers, B-K except
for C (Figure 1). Through SXRD analysis, all nine MOF-177-X
structures were found to have crystalized in the same trigonal space
7
O
2
4
6
1
5
group (P3
ത1c), have similar unit cell parameters with respect to one
Linker F and J select for pyr and rtl rather than qom net. Alt-
hough the MOF-177 architecture was realized for all, but one, link-
ers employed in this study, topological diversity was still observed
in the MOF synthesis, specifically when linkers F and J were em-
ployed alone.
another, and were confirmed to be isoreticular to MOF-177-A (SI,
Section S2). For each of these single-crystal structures, two Zn O(-
COO) clusters and three tritopic BTB linkers, with the respective
4
6
functionalities, were crystallographically independent and their
location and connectivity were well resolved to elucidate the qom
net. These findings demonstrated that the MOF-177 structure is, in
fact, tolerant to a wide range of functionalities with respect to steric
congestion and inductive effects imposed on the BTB linker.
MOF-155-F. Cubic-shaped crystals of MOF-155 were obtained
under the same synthetic conditions used for MOF-177-A, but
different in that linker F is substituted for linker A. The single crys-
tal X-ray structure of MOF-155 shows that this isomeric structure
crystallizes in the cubic Ia3
ത space group with an axis length of
A detailed analysis of the linker conformation in each single-
crystal structure of this MOF-177 series was performed (SI, section
25.9639(7) Å. In this structure, octahedral Zn
4
O(-COO) units are
6
2
). Specifically, two dihedral angles were calculated and tabulated
linked by tritopic BTB-(F) linkers to afford a three-dimensional
2
(Table S14): the angle between the peripheral benzoate units and
framework having a pyr net (Figure 2a). Furthermore, MOF-155
consists of two-fold interpenetrating frameworks, which leads to a
bicontinuous channel with a smaller internal pore diameter of 8 Å.
the central benzene (ϕ, Figure S15) and the angle between the
peripheral benzene and carboxylate (ψ, Figure S15). It was found
that the rotation of the ϕ angle was critical to adjust for the different
functionalities incorporated. Due to a slight rotational disorder
resulting from multiple independent linkers in the structure, the ϕ
angle is represented as an average. Relatively large ϕ angles were
observed in MOF-177-G and -J (65.8° and 52.7°, respectively),
which significantly differed from that of the pristine MOF-177-A
MOF-156-J. Needle-shaped crystals were obtained under the
same synthetic conditions used for MOF-177-A, but using linker J
instead of linker A. This MOF has a tetragonal P4 /mnm space
2
group with axis lengths of a = 24.360(3) and c = 16.909(3) Å. The
underlying net of this MOF is rtl, which is that of rutile: the Ti and
O atoms are replaced by Zn
4
O(-COO) units and linker J, respec-
6
(
36.9°). This is attributed to steric hindrance resulting from func-
tionalization at the R position. Although linker E incorporates a
bulky -OC group at the R position, the dihedral angle in MOF-
77-E was quite small (32.0°). These two results indicate that func-
tional groups at the meta-position (R ) of the peripheral benzoate
tively, to produce square channels of 9 Å in diameter (Figure 2b).
3
MOF-155-J. Interestingly, another MOF based on pyr was also
observed when using linker J alone (Scheme 2). This phase is a
byproduct during the synthesis of MOF-177-J and MOF-155-J.
MOF-155-J crystallizes in the cubic Pa 3ത space group with an axis
length of 25.888(3) Å (Figure S12 and Table S12). This structure
also has the same pyr net topology, but consists of two interpene-
trating frameworks.
7
H
7
1
1
3
units imposed greater steric restriction to the free rotation of the
benzoate; therefore the conformation of the respective linkers has
to be significantly altered in order to adopt the qom net. This is in
contrast to the functional groups at the ortho-position. A quantita-
6
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Page 7 of 12
Journal of the American Chemical Society
of the MTV-MOF-177 materials.
1
2
3
4
5
6
7
8
9
The PXRD pattern of MTV-MOF-177-ABG is shown in Figure
. To limit the contribution of solvent in the X-ray diffraction pat-
3
tern, MTV-MOF-177-ABG was activated. This process allowed for
the collection of a higher quality PXRD pattern. No extra diffrac-
tion peaks were observed from the experimental PXRD pattern in
comparison with the simulated pattern generated from the struc-
tural model of MOF-177-A. It is noted that only a small difference
in intensities were realized after the convergence of Pawley refine-
ment (Rwp = 17%; R
group (Trigonal P3
p
= 12%), which took into account the space
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
ത1c) and unit cell parameters (a = 38.123, c =
Figure 2. Crystal structure of MOF-155-F made from linker F in dou-
bly interpenetrated pyr net (a) and crystal structure of MOF-156-J
made from linker J forming the rtl net (b). Atom colors: C, black; O,
red; N, blue; F, green; Zn, blue polyhedra; H atoms were omitted for
clarity. The interpenetrating framework (green hexagons linked by
blue polyhedral) in (a) is also depicted. Atom colors: Zn, grey polyhe-
dra and C, grey. The large yellow sphere represents the void in the
structure.
30.632 Å).
Aside from the expected inductive effects, the relative positions
of the functionalities on the BTB linker can impact the confor-
mation of the linker structure, as evidenced by the varying linker
conformations observed in these topologically diverse MOFs.
When comparing the linker conformations in the different topolo-
gies, it is suggested that in the pyr net (MOF-155-F and -J), the
linkers F and J experience a slight distortion and deviate from the
molecular plane that is defined by the three carbon atoms from the
three carboxylate groups (Figure S18). Upon careful analysis of
linker J in the rtl net (MOF-156-J), distortion of the linker was not
observed (Figure S19), however, differences in linker orientation
accompanied by distortion of the SBU were (Figures S20 and S21).
Since the qom net can also be derived from these linkers, the de-
sign of the linker was not solely consequential for determining the
resulting topologies in these cases. Nevertheless, synthetic condi-
tions (dilution of reactant concentration or using different solvent
systems altogether) and the MTV approach were the most viable
means for obtaining control over the observed topological diversity.
Figure 3. PXRD pattern of activated (red) MTV-MOF-177-ABG
sample and the profile fitting using Pawley refinement (blue).The
difference plot (green) and Bragg position (magenta) are also dis-
played as references overlaid.
Next, an activated sample (ca. 10 mg) of MTV-MOF-177-ABG
was dissolved in DMSO-d
and 20% DCl in D
6
(deuterated dimethyl sulfoxide, 580 L)
O (20 L) for H NMR analysis. The proton
1
2
signals from each linker can be assigned based on the chemical
shifts and their inherent splitting patterns (Figure 4). The linker
ratio for A:B:G was calculated to be 1.00:0.32:0.62, which is differ-
ent from the input ratio used in the reaction mixture (elaborated
below). The formula of MTV-MOF-177-ABG was thus estimated
Multivariate (MTV) Metal-Organic Framework-177: Incor-
poration of Multiple Functionalities within the Same Frame-
work. Fourteen MTV-MOF-177 compounds were prepared by
mixing two or three types of linkers. This strategy was used in order
to assess how the introduction of multiple functional groups in
varying ratios within the pores of MOF-177-A impacts gas proper-
ties when compared to that of the parent MOF-177-A structure
as Zn
4
O(BTB)1.03(BTB-NH )0.31(BTB-Nap)0.66 and further con-
2
firmed by EA (see Experimental Section).
(
Scheme 1). For the binary MTV-MOF-177 compounds, ten were
composed of BTB and one functionalized BTB linker (MTV-
MOF-177-AB, -AC, -AD, -AE, -AF1, -AF2, -AG, -AH, -AI, and -AJ)
and three were composed of two different functionalized BTB link-
ers (MTV-MOF-177-BC, -BG, and -CG). Furthermore, a ternary
system of MTV-MOF-177-ABG was prepared by combining two
functionalized BTB linkers (B and G) with the pristine BTB linker
(
A) to illustrate the application of the MTV approach to the struc-
ture of MOF-177. The successful formation of highly crystalline
and phase-pure MTV-MOF-177 structures was confirmed by
PXRD analyses of the as-synthesized samples (SI, Section S3).
Once the phase purity was confirmed, the ratios of the linkers in the
1
Figure 4. H NMR spectrum of MTV-MOF-177-ABG demonstrating
the linker ratio in the MOF backbone. All three linkers are present with
significant occupancy. The chemical shifts were assigned to each corre-
sponding linkers and the integration were used for the calculation of
linker ratio.
1
MTV-MOF-177 derivatives were estimated from H NMR spectra
of their acid-digested samples (SI, Section S5). We describe the
characterization of MTV-MOF-177-ABG as a representative for all
7
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Journal of the American Chemical Society
Page 8 of 12
Control of Linker Ratios in Binary MTV-MOF-177. The rel- size of functional groups included within the framework; MOF-
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
ative ratios of the various linkers incorporated within the frame-
work were quantitatively examined in digested MOFs by NMR
spectroscopy. The relationships between the input ratio, based on
the concentration of linkers used in the synthesis, and the output
ratio, based on the concentration of linkers observed in the MOF
crystals, were systematically studied in four selected MTV-MOF-
177-X structures having smaller functional groups (e.g. MOF-177-
B, -D and -J) exhibit greater geometric surface areas when com-
pared to MOF-177-X structures with bulky functionalities (e.g.
MOF-177-G and -E). Remarkably, due to the high porosity of orig-
inal MOF-177-A, it is clear that these isostructural frameworks are
capable of retaining high porosity even upon addition of functional-
ities within the pores.
1
–
77 structures composed of two unique linkers (-AB, -AC, -AF, and
AG; Figure 5). From this, a clear trend is observed of the output
The porosity of the MOF-177-X isostructural series was experi-
linker ratio in the resulting MTV-MOF crystal increasing when a
higher input ratio of the corresponding linker was applied in the
starting solution of the reaction.
mentally proven by N
a). All examined MOF-177-X materials displayed significant N
2
adsorption measurements at 77 K (Figure
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
6
2
uptake in the low-pressure region (P/P
0
< 0.05) and near satura-
There is a clear deviation from the linear relationship that is ex-
pected in an ideal scenario of output ratio being equal to that of the
input. However, a general trend is noted of linker A being incorpo-
rated more readily than other functionalized linkers. In every exam-
ined MTV-MOF containing linker A, the amount of A was always
higher than the other linkers in the frameworks. The preferred
incorporation of linker A is most likely a result of the linker's flexi-
bility of rotation to adopt the MOF-177 structure (Figures S16 and
S17), however, many other factors, including reaction kinetics and
substituent effects, may also play important roles for this.
tion was observed at P/P = 0.2, which is indicative of permanent
0
microporosity. The profiles of the isotherms are all classified as
Type I. Additionally, all of these materials exhibit high BET surface
2
3
2
areas (large pore volumes) [3800 m /g (1.63 g/cm ), 2650 m /g
3
2
3
2
3
(1.53 g/cm ), 3690 m /g (1.53 g/cm ), 3480 m /g (1.68 g/cm )
for MOF-177-B, -D, -F, and -I, respectively]. These values are close
to those that were geometrically calculated from their structural
models (Table 1). As a reference, the Langmuir surface areas of
MOF-177-X analogs are also listed in Table 1. However, these
values are lower than those of unfunctionalized MOF-177-A due to
their smaller void fraction and larger crystal density.
It is worth noting that by employing the multivariate strategy,
linker C can be incorporated into the MOF-177 structure and in
significant amounts (higher than 60% when accompanied by linker
A, Figure 5) by manipulating the input linker ratios during the syn-
thesis. This is interesting given the fact that it proved difficult, if not
impossible, to construct an isoreticular MOF-177 structure when
linker C was used alone. Although an output ratio cannot be pre-
dicted a priori, a reproducible input/output relationship diagram
can be constructed (Figure 5). This proves beneficial when a tar-
geted functional group is needed with a desired concentration in
the MOF crystal.
The high N (Ar) uptake capacity at 77 K (87 K) is also observed
2
for the MTV-MOF-177 compounds (Figure 6b); these MOF ma-
terials showed Type I isotherms with no significant accompanied
hysteresis. The BET surface areas were calculated to be 3950, 2430,
2
2740, 3330, 4315, 4170, 4000, and 3490 m /g for MTV-MOF-177-
AB, -AC, -AD, -AE, -AF1, -AF2, -AG, and -ABG, respectively. A
noticeable trend is observed in that the estimated surface areas are
proportional to the pore volume and the surface areas are less sensi-
tive to the functionalities in the MOF structures (Table 1).
Figure 5. Diagram demonstrating the relationship between input ratios
and output ratios of various functionalized linkers in MTV-MOF-177-
AB (orange), -AC (magenta), -AF (green), and -AG (purple), respec-
tively. As the input ratio increases, the presence of linker in the MTV-
MOF backbone also increases, albeit in a nonlinear relationship.
Permanent Porosity and Hydrogen Adsorption Capacity.
Before the gas adsorption measurements were conducted, the void
fraction and geometrical surface area of the single-linker-based
MOF-177-X series were estimated (Table 1). As is shown, there is a
rough trend based on the relationship between porosity and the
Figure 6. N (Ar) adsorption isotherms at 77 K (87 K) for MOF-177
analogs (a) and MTV-MOF-177 derivatives (b) showing that all
MOFs have permanent porosity and high surface area after activation.
2
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Low-pressure hydrogen isotherms of MTV-MOF-177 deriva-
SUMMARY
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
tives were recorded at 77 K (Figure 7). The hydrogen uptake grad-
ually increased with an increase in the pressure, while no saturation
uptake was observed under the present experimental conditions.
An increase in volumetric hydrogen uptake was generally observed
in all the MTV-MOF-177 derivatives in comparison with the un-
functionalized MOF-177-A parent structure. It is worth noting that
the MOF-177-B and MOF-177-D are observed to have 25% higher
In this work, we have functionalized the highly porous MOF-177
structure through the incorporation of one or multiple types of
functionalized tritopic linkers. We have demonstrated that MOF-
177 with the qom topology is quite tolerant to a wide range of func-
tional groups. However, topological diversity and phase selection
was observed as a function of the positioning of the functional
group on the BTB linker. The MTV approach allowed the system-
atic investigation of multivariate materials with varying ratios of
multiple functionalities. In turn, this provided motivation for un-
covering the trend of disproportional incorporation of different
linkers in the synthesis, which enables the customized production
of MTV-MOF-177 structures with specific ratios of desirable func-
tionalities. Adsorption studies on selected MOF-177 analogs and
derivatives showed the retention of its high surface area and re-
vealed an enhancement in hydrogen uptake.
2
H volumetric uptake than that of the MOF-177-A at 800 Torr.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
On a fundamental level, we have shown that (a) the position of
functionality on an organic linker codes for certain MOFs of a spe-
cific topology, (b) a specific functionality, which could not be in-
troduced into a specific structure can be successfully introduced
into the desired MOF structure by the MTV approach, and (c) the
presence of more than one kind of functionality in MOFs leads to
enhancement of gas adsorptive properties where the whole per-
forms better than the sum of the parts.
ASSOCIATED CONTENT
Supporting Information. Linker syntheses and characterization,
SXRD data, linker conformations, molecular mechanics energy calcula-
tions, PXRD patterns, TGA curves, NMR spectroscopy, adsorption
isotherms, and CIF files. This material is available free of charge via the
Internet at http://pubs.acs.org.
Figure 7. Volumetric H
MTV-MOF-177 compounds (b). A maximum 25% increase of H
uptake can be observed with MOF-177-B and -D, when -NH and -
OCH functional groups are introduced respectively.
2
uptake at 77 K for MOF-177-X (a) and
2
AUTHOR INFORMATION
2
Corresponding Authors
hdeng@whu.edu.cn; jaheon@ssu.ac.kr; yaghi@berkeley.edu
3
A high-pressure methane adsorption isotherm for MTV-MOF-
77-AF1 was recorded at 298 K (Figure 8). The methane uptake
1
Notes
behavior of MTV-MOF-177-AF1 is similar to that of the unfunc-
The authors declare no competing financial interest.
3
3
tionalized MOF-177-A, which exhibits roughly 210 cm /cm (150
g/L) at 80 bar and 298 K.
ACKNOWLEDGMENT
This work was partially supported for synthesis by U.S. Department of
Energy, Office of Science, Office of Basic Energy Sciences, Energy
Frontier Research Center (DE-SC0001015), characterization by
KACST (Saudi Arabia), and gas adsorption by BASF SE (Ludwigsha-
fen, Germany). We acknowledge Drs. S. K. Dey, C. Valente, and Prof. J.
F. Stoddart (Northwestern University) for preliminary work on the
synthesis of the links; Drs. S. Teat and K. Gagnon for the synchrotron
X-ray diffraction data acquisition support at the beamline 11.3.1 (Ad-
vanced Light Source, Lawrence Berkeley National Laboratory); Drs. F.
Gándara (Yaghi group) and C. B. Knobler (UCLA) for support in X-
ray crystallography; and Drs. A. C.-H. Sue, M. Suzuki, A. M. Fracaroli, J.
Yuan (Yaghi group), and Mr. J. Park (KAIST, Republic of Korea) for
support in the sample preparation and characterization. J.K. thanks the
support by the Korea CCS R&D Center grant funded by the Ministry
of Science, ICT & Future Planning (NRF-2012-0008900), and the
Pohang Accelerator Laboratory for the X-ray data collection (Republic
of Korea).
Figure 8. Volumetric CH total uptake at 298 K for MTV-MOF-177-
4
AF1 (green) compared with those of the MOF-177-A (red) and the
bulk methane (black).
9
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Journal of the American Chemical Society
Table 1. Porosity data for MOF-177-X and MTV-MOF-177 compounds.
Page 10 of 12
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1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
a
Compound
Formula
Crystal
A
BET
2
A
Lang
2
A
geo
2
V
p
3
density
(m /g)
(m /g)
(m /g)
(cm /g)
3
(
g/cm )
0.43
0.46
0.49
0.66
0.51
0.54
0.47
0.46
0.46
0.48
0.44
0.45
0.45
0.48
0.45
0.46
0.47
0.45
0.44
0.44
0.49
0.50
0.54
0.47
MOF-177-A
MOF-177-B
MOF-177-D
MOF-177-E
MOF-177-F
MOF-177-G
MOF-177-H
MOF-177-I
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
Zn
4
O(BTB)
O(BTB-NH
O(BTB-OCH
O(BTB-OC
O(BTB-(F)
2
4740
3800
2650
ND
3690
ND
ND
3480
ND
5340
4620
3560
ND
4345
ND
ND
4760
ND
4800
4530
4510
2880
3980
4350
4360
4360
4810
4570
ND
ND
ND
ND
ND
ND
ND
ND
ND
1.89
1.63
1.53
ND
1.53
ND
ND
1.68
ND
ND
1.54
1.39
1.18
1.29
1.79
1.66
1.76
ND
ND
ND
ND
ND
ND
1.49
2
)
3
2
)
7
2
7
H
)
2
2
)
2
O(BTB-C
O(BTB-F)
4
H
2
4
)
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
O(BTB-CH
O(BTB-mNH
O(BTB-C /NH
3
)
2
MOF-177-J
MOF-177-K
2 2
)
4
H
4
2
)
2
ND
ND
MTV-MOF-177-AB
MTV-MOF-177-AC
MTV-MOF-177-AD
MTV-MOF-177-AE
MTV-MOF-177-AF1
MTV-MOF-177-AF2
MTV-MOF-177-AG
MTV-MOF-177-AH
MTV-MOF-177-AI
MTV-MOF-177-AJ
MTV-MOF-177-BC
MTV-MOF-177-BG
MTV-MOF-177-CG
MTV-MOF-177-ABG
O(BTB)1.43(BTB-NH
O(BTB)1.69(BTB-NO
O(BTB)1.37(BTB-OCH
O(BTB)1.54(BTB-OC
O(BTB)1.46(BTB-(F)
O(BTB)1.21(BTB-(F)
O(BTB)1.29(BTB-C
O(BTB)1.17(BTB-F)0.83
O(BTB)1.17(BTB-CH
O(BTB)1.40(BTB-mNH
2
)
)
0.57
0.31
3950
2430
2740
3330
4315
4170
4000
ND
ND
ND
ND
ND
4700
3727
3340
3960
5110
4710
4870
ND
ND
ND
ND
ND
2
3
)
0.63
0.46
7
H
7
)
2
)
0.54
2
)
0.79
4
H
4
)
0.71
3
)
0.83
0.60
2
)
ND
ND
ND
ND
O(BTB-NH
O(BTB-NH
O(BTB-NO
2
2
2
)
)
)
1.18(BTB-NO
1.04(BTB-C
0.62(BTB-C
2
)
0.82
4
H
H
4
)
0.96
4
4
)
1.38
ND
3490
ND
4122
O(BTB)1.03(BTB-NH
2
)
0.31(BTB-C
4
H
4
)
0.66
ND
aABET, ALang, and Ageo are the BET, Langmuir, and geometric surface areas, respectively. V
is the measured pore volume. ND, no data. Geometric sur-
p
16
face areas were calculated using Materials Studios 5.0 with the N
2
as probe (diameter 3.681 Å) according to published procedure.
Chem. Res. 2005, 38, 176.
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2, 5544. (d) Martí-Gastaldo, C.; Antypov, D.; Warren J. E.; Briggs, M. E.;
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