Construction of Stable Helical Metal-Organic Frameworks with a Conformationally Rigid “Concave Ligand”

Article abstract of DOI:10.1002/chem.202101173

A helical metal-organic framework was prepared by using a conformationally rigid tetratopic benzoic acid ligand with binding units pointing toward each other (concave ligand). To avoid the obvious intramolecular interactions between binding units, matching spacing groups were applied to introduce atropic repulsion, thereby allowing the formation of extended frameworks for the first time. With this new ligand design, a helical-shaped MOF with significantly improved air and moisture stability was successfully prepared, thus providing a new strategy for ligand design toward porous material constructions.

Full text of DOI:10.1002/chem.202101173

Accepted Article
Accepted Article
Title: Construction of Stable Helical Metal-Organic Frameworks with
Conformationally Rigid “Concave Ligand”
Authors: Xiaodong Shi, Kai Zhao, Ying He, Chuan Shan, Junyu Ren,
Yu Yan, Hanzhong Shi, Haonan Wang, Lukasz Wojitas, and
Zhiguang Song
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Chem. Eur. J. 10.1002/chem.202101173
Link to VoR: https://doi.org/10.1002/chem.202101173
01/2020

10.1002/chem.202101173
Chemistry - A European Journal
COMMUNICATION
Construction of Stable Helical Metal-Organic Frameworks with
Conformationally Rigid “Concave Ligand”
Kai Zhao, [a] Ying He, [b] Chuan Shan, [b] Lukasz Wojtas, [b] Junyu Ren, [c] Yu Yan, [b] Hanzhong Shi, [d]
Haonan Wang, [d] Zhiguang Song*[a] and Xiaodong Shi*[b]
Abstract: A helical-shaped metal-organic framework was prepared
using conformationally rigid tetratopic benzoic acid ligand with binding
units pointing toward each other (concave ligand). To avoid the
obvious intramolecular interactions between binding units, matching
spacing groups was applied to introduce atropic repulsion, allowing
the formation of extended frameworks for the first time. With this new
ligand design, a helical-shaped MOF was successfully prepared with
significantly improved air and moisture stability, providing a new
strategy for ligand design toward porous material constructions.
clusters, will certainly result in new molecular architecture,
which could further enrich the MOF research and
applications.
A) Ligand skeleton in MOF synthesis
examples
HOOC
COOH
“convex-ligand”
binding
unit
ZJU-31;
NU-1400
MOF network
ref. 8-9
organic skeleton
HOOC
COOH
“concave-ligand”
M
M
concave-ligand:
Mn+
With the high surface area and adjustable pore size, the
metal-organic framework (MOF) has enjoyed its unique
position in material science with many impressive
applications in various research areas both in academic and
industrial settings.[1] Despite the numerous stellar MOFs
synthesis, the general design of the organic ligands could be
divided into two parts: A) binding domain and B) structural
domain (skeleton).[2] The combination of different metal ion
binding patterns (clusters) and diverse organic skeletons
assure the ability to access a large number of porous
structures with versatile functionality.[3] Based on the
tremendous successes in ligand design and complex
synthesis, the focus of MOF research shifts more toward
practical applications in the past decade, with many
promising systems developed including targeting gas
separation/storage,[4]energy storage,[5] sensors,[6] and
intramolecular binding;
preventing network formation;
not good for MOF synthesis!?
MOF
?
B) This work: Facile synthesis of concave ligand and first helical MOF from concave ligand
prevent intramolecular binding
facile synthesis
X
A
A
H
H
5 steps
n
NH2
cheap SM
ꢀ35% overall
yields
n = 1,2,3
A = COOH
helical MOF
gram scale synthesis
designed atrop-repulsion
A
A
Scheme 1. Ligand skeleton in MOF network synthesis
In general, to ensure the effective synthesis of polymeric
network structures, the “open-arm” ligand design has been
adopted in almost all reported MOFs. As shown in Scheme 1A,
the binding units are positioned at the “convex” face of the ligand
skeleton, allowing easy structure extension. Some representative
MOFs with this “convex-ligand” design are ZJU-31[8] and NU-
1400.[9] Not surprise, ligand skeletons with binding units pointing
toward each other has not been widely applied in MOF synthesis
due to the concern that the primary binding mode of this “concave
ligand” is intramolecular coordination, preventing the formation of
extended polymeric networks.
Besides the unfavored binding geometry, another major
problem of “concave design” is the challenging synthesis of the
ligand with crowded substitution all located on one side of the
molecule.[10] To ensure practical synthesis, easy access to ligand
is one important feature in MOF chemistry.[11] Based on
conformation analysis and orthogonal functional groups synthesis
design, herein, we report a new helical-MOF synthesis using
properly designed concave ligand bearing atrop-repulsion, which
effectively prevents the undesired intramolecular binding unit
aggregation to ensure the polymeric network construction. To the
best of our knowledge, this is the first example of MOF reported
with the novel concave ligands design principle.
heterogeneous catalysis.[7]
Despite these tremendous
progress, one may envision that the new ligand design
principle remains as a critical factor in MOF research as it
would provide a fundamentally different linkage strategy for
porous material synthesis. Integration of the new design
principle with other typical binding features, such as various
secondary building units (SBUs) and different coordination
[*]
K. Zhao and Prof. Z. Song
State Key Laboratory of Supramolecular Structure and Materials,
College of Chemistry, Jilin University, Changchun, Jilin, 130012,
China
E-mail: szg@jlu.edu.cn
Dr. Y. He, C. Shan, Y. Yan, Dr. L. Wojtas and Prof. X. Shi
Department of Chemistry, University of South Florida
Tampa, FL 33620, United States.
Fax: (+1) 813-974-3203
E-mail: xmshi@usf.edu
With good structural rigidity and easy functionalization ability,
benzene has been widely applied as the backbone for ligand
skeleton synthesis.[12] One main challenge in preparing ligand
with “concave” binding units is the need of a spatial “crowed”
1,2,3-tri-substituted building blocks that bear orthogonal reactive
sites (selective reacting with C-2 over C-1 and C-3).[10] To achieve
MOF practical application, the readily available ligand with
Homepage: http://xmshi.myweb.usf.edu/index.htm
J. Ren
Department of Chemistry, University of North Texas, 1508 W
Mulberry St, Denton, TX76201, United States.
H. Shi and H. Wang
Department of Chemistry and Biomedical Engineering, University
of South Florida, Tampa, FL33620, United States.
1
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10.1002/chem.202101173
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efficient synthesis (large scale and show steps) is crucial. With a
strong interest in exploring this concave ligand design, we set a
goal to develop a practical synthesis of 1,2,3-trisubstituted ligands
through a modular approach. After exploring several different
approaches, we identified the application of diazonium and halide
as the orthogonal coupling units to achieve various concave-
shape ligands (6a-6c) with high overall yields and capability in
the undesired intramolecular interactions.
This atrop-
repulsion makes COOH in twisted conformation and
available for the construction of extended networks. With this
analysis, we put our efforts in synthesizing MOF using this
twisted arm ligand 6a. After exploring various MOF synthesis
conditions, a colorless single crystal was obtained when
treating 6a with Cd(NO3)2•4H2O in DMF and water mixture at
85 oC for 18 hours. After cooling the reaction mixture to room
temperature, complex 6a-MOF-Cd was obtained in 91%
yield. The FT-IR spectra of the resulting MOF confirmed the
disappearance of the carboxylic acid group at 3114 cm-1 and
coordinated carboxylate groups stretching at 1393 cm-1 and
1527 cm-1, indicating the coordination between carboxylates
and metal cations (see Fig S3).
large scale productions.
This modular synthetic route is
summarized in Figure 1.
HBr, H2O2
1) NaNO2, HCl
MeOH, rt. 98%
2) KI, H2O, rt
Br
Br
Br
Br
NH2
87% overall yields
NH2
I
1
2
3
(HO)2B
B(OH)2
n
HOOC
COOH
> 75%
(3% Pd(dppf)2Cl2)
Br
gram scale
MeOOC
B(OH)2
Br
1) 10% Pd(PPh3)4, 110 o
2) LiOH 85 o
> 55% two steps
C
n
n
C
6a: n=1
6b: n=2
6c: n=3
Br
Br
4a-4c
HOOC
COOH
Figure 1. General synthetic route of concave ligand 6.
The synthesis starts from commercially available para-
methyl aniline Bromination followed by oxidation
(diazonium formation) and iodination gave the 1,2,3-tri-
substituted arene in excellent yields and large scale (>100
gram). After screening various coupling conditions,
1
.
3
combination Pd(dppf)2Cl2 catalyst and aryl bis-boronic acid
(commercially available) was identified as the optimal
conditions, giving the C-2 coupling products
The resulting tetra bromoarene were charged with typical
Suzuki conditions followed by saponification to yield the
tetra-acid concave ligands. This synthesis has high
4 in good yields.
4
6
efficiency with the overall yields >35%. Also, the design is
based on the modular synthesis concept, where the different
combinations of central linkers (various length and binding
angle) and various binding arms could be easily prepared
under similar conditions. Some alternative linkers (alkyne
and heterocycles) and binding arms are currently under
investigation in our lab.
To explore whether concave-shape ligands could be
applied for MOF network construction, we put our focus on
evaluating ligand
6 with three different central arene linkages.
Compounds 6a-6c were prepared and applied in MOF
synthesis. Although almost fifty MOF growing conditions
have been tried under different combinations of cations,
solvents, and acid additives, ligands 6b and 6c failed to give
Figure 2. Helical MOF from concave ligand with atrop-repulsion
The single-crystal of 6a-MOF-Cd was obtained which
revealed the structure of 6a-MOF-Cd as triclinic space group
P-1 (a=10.615(8) Å, b=15.614(0) Å, and c=17.580(6) Å).[14]
As shown in Figure 2B, each asymmetric unit in 6a-MOF-Cd
crystalline polymeric MOF so far.
The competing
intramolecular binding between the concave binding
moieties could be problematic, which highlighted the
significant challenges in constructing porous networks using
consists of two Cd2+ and four concave ligands 6a
.
The
the concave ligand design.
Based on the structural
secondary building unit (SBU) contains two Cd with different
coordination patterns. Cd1 is bonded to six O atoms (two
from DMF and three from 6a, Cd1-O distances:2.210-2.354
Å), whereas Cd2 binds to seven O atoms (two from DMF and
three from 6a, Cd2-O=2.209-2.438 Å). With this twisted
concave ligand 6a and two types of Cd clusters, a new 2D
helical molecular architecture was formed. Two micropores
conformation analysis, we hypothesized that ligand 6a could
be used to overcome the intramolecular binding competition
with the “atrop-repulsion”.
As shown in Figure 2A, with a shorter linker, the two
benzene at the side arms could encounter steric repulsion
and push the two arenes away from each other.[13] As the
results, the two COOH binding units are twisted and prevent
2
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were identified with sizes of 6.7 Å and 5.6 Å. The distance
between the upper and lower hydrophobic edge of the 2D
planar structure is 14.4 Å (Figure 2C). The topology of 6a-
MOF-Cd was abstracted to 3,3,4-c using ToposPro.[15] The
ligand 6a was simplified into two connected triangles with
four carboxylates extending in different directions. After
removing free solvent molecules in the crystal structure, the
total void volume of 6a-MOF-Cd was calculated and
estimated to be 38.5 % by PLATON.[16]
the complex in aqueous solutions at different pH for 24 hours.
As shown in Figure 3C, the crystalline frameworks remain
intact in a wide range of acidic and basic conditions (pH=2 to
pH=12) and at high temperature (85 oC 24 hours). It is known
in literature that COO-Cd could be very labile in aqueous due
to the competing O-Cd binding. The excellent water and
acid/base stability of this new MOF is very impressive and
highlighted the clear advantage of this new concave ligand
design in MOF formation.
To confirm the phase purity, powder X-ray diffraction
(PXRD) spectra of 6a-MOF-Cd was collected.
The
diffraction patterns of the tested samples and the calculated
data from crystal structure were compared (Figure 3A). As
shown in the crystal structure, the hydrophobic methyl
groups on the edge of ligand 6a point to the upper and lower
faces of the complex, forming a hydrophobic centered tube.
This structure feature suggests the opportunity for future
structure modification by introducing different functional
groups at the methyl position for new network construction
and applications. CO2 adsorption isotherms of 6a-MOF-Cd
was recorded at 195 K. The Langmuir and Brunauer-
Emmett-Teller (BET) surface area were calculated to be
465.89 and 283.69 m2g-1 respectively. The maximum CO2
uptake of 6a-MOF-Cd of 113.4 cm3g-1 at P/P0=0.95 was
recorded (Figure 3D). Although this number is relatively low
compared to other reported MOFs,[4a,17] the introduction of
atrop-repulsion in concave ligand for the successful
synthesis of polymeric complexes representative provides a
new design principle for MOF synthesis.
Figure 3. A) PXRD patterns of 6a-MOF-Cd. B) Stability of 6a-MOF-Cd in
organic solution. C) Stability of 6a-MOF-Cd in aqueous solution from
pH=2 to pH=12. D) 195K CO2 uptake of 6a-MOF-Cd
In conclusion, based on structure functional group
orthogonal reactivity, we developed a facile synthesis of
tetra-carboxylate bearing concave binding geometry. As the
modular synthesis, various concave ligands containing
different linkers and arms could be readily synthesized in
gram scale. Through structure conformational analysis, we
identified ligand 6a with atrop-repulsion to avoid
intramolecular binding and successfully prepared the first
polymeric 6a-MOF-Cd complexes bearing a concave ligand
design. With the maximization of the A-1,3 repulsion effect,
the concave ligand 6a can spirally extend in a two-
dimensional space to produce a chiral helical 2D-MOF
molecular architecture. This new framework exhibited
excellent solvent and acid-base stability owing to its
hydrophobic surface. Based on this novel concave ligand
design, derivatization on such ligands towards the
development of new materials with the potential application
is undergoing in our laboratory.
Besides the readily available synthesis, complex
chemical and thermal stabilities are crucial for practical
applications of any new MOFs. As many other MOF
materials, the first stage of mass loss in 100-250 oC was
caused by the release of non-bond solvents (DMF and water,
etc). 6a-MOF-Cd was stable under vacuum of 110 oC for 12
hours. After the sorption experiment was carried out under
CO2 at 195K, the PXRD suggesting that the MOF framework
remains the same. PXRD of the sample after heating to 200
oC showed the collapse of the framework. Based on the TGA
result, the content of free DMF and water is 19.5%. The
weight loss of the sample between 410-520 oC is 54%, which
is the total amount of ligand 6a in the sample. After 520 oC,
there is almost no significant weight loss, and the final
residue is likely the CdO after metal oxidation and complex
decomposition (Figure S6).
Due to water or solvent binding competition, the chemical
stability of MOFs could be a concern, especially when
treating MOFs in acid or basic aqueous solution. To our
great satisfaction, this new MOF material from the concave
ligand showed excellent stability in a wide range of solvents
and large pH range. Soaking 6a-MOF-Cd in different
solvents (including water, MeOH, MeCN, THF, and DCM) for
a week gave almost no decomposition of the complexes with
PXRD signals remaining almost identical as the as-
synthesized MOF, demonstrating the excellent stability of
this new class of MOFs in various solvents (Figure 3B). The
acid and base stability was also investigated upon soaking
Acknowledgements
We are grateful to the NSF (CHE-1665122), the NIH
(1R01GM120240-01), and Jilin Province (20170307024YY,
20190201080JC) for financial support.
Keywords: MOF • concave ligand • helical structure • acid-base
stability
3
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[1]
a) S.Kitagawa, K.Uemura, Chem. Soc. Rev.,2005, 34, 109-119; b) H.C.
Zhou, J.R. Long, O.M. Yaghi, Chem. Rev.,2012, 112, 673-674; c) K.
Shen, L. Zhang, X. Chen, L. Liu, D. Zhang, Y. Han, J. Chen, J. Long, R.
Luque, Y. Li, B. Chen, Science, 2018, 359, 206-210; d) O. M. Yaghi, H.
Li, J. Am. Chem. Soc., 1995, 117, 10401-10402; e) Y. Tian, G. Zhu,
Chem. Rev., 2020, 120, 8934-8986; f) X. Qian, F. Sun, J. Sun, H. Wu, F.
Xiao, X. Wu, G. Zhu, Nanoscale, 2017, 9, 2003-2008; g) Y. Bai, Y. Dou,
L.-H. Xie, W. Rutledge, J.-R. Li, H.-C. Zhou, Chem. Soc. Rev.,2016, 45,
2327-2367.
[12] a) J.P. Meng, Z.S. Yan, J.Y. Long, Y. Gong, J.H. Lin, J. Solid State Chem.,
2017, 245, 74-81; b) Y.-B. Zhang, H. Furukawa, N. Ko, W. Nie, H.J. Park,
S. Okajima, K.E. Cordova, H. Deng, J. Kim, O.M. Yaghi, J. Am. Chem.
Soc., 2015, 137, 2641-2650; c) P.T.K. Nguyen, H.T.D. Nguyen, H.Q.
Pham, J. Kim, K.E. Cordova, H. Furukawa, Inorg. Chem., 2015, 54,
10065-10072.
[13] a) Y. Hu, X.-Y. Wang, P.-X. Peng, X.-C. Wang, X.-Y. Cao, X. Feng, K.
Mullen, A. Narita, Angew. Chem. Int. Ed., 2017, 56, 3374-3378; b) F.
Johnson, Chem. Rev., 1968, 68, 375-413; c) J.-S. Qin, S. Yuan, L. Zhang,
B. Li, D.-Y. Du, N. Huang, W. Guan., H.F. Drake, J. Pang, Y.Q. Lan, A.
Alsalme, H. C. Zhou, J. Am. Chem. Soc., 2019, 141, 2054-2060.
[14] Deposition numbers 2056649 (for 4a), 2056646 (for 5a), 2056648 (for 6a)
and 2056647 (for 6a-MOF-Cd) contains the supplementary
crystallographic data for this paper. These data are provided free of
charge by joint Cambridge Crystallographic Data Centre and
Fachinformationszentrum Karlsruhe Access Structures Service.
[15] V. A. Blatov, A. P. Shevchenko, A. M. Proserpio, Cryst. Growth Des.,
2014, 14, 3576-3585.
[2]
a) W.Lu, Z. Wei, Z. Y. Gu, T.-F. Liu, J. Park, J. Tian, M. Zhang, Q. Zhang,
T. Gentle III, M. Bosch, H.-C. Zhou, Chem. Soc. Rev., 2014, 43, 5561-
5593; b) O.M. Yaghi, M. O'Keeffe, N.W. Ockwig, H.K. Chae, M. Eddaoudi,
J. Kim, Nature, 2003, 423, 705-714; c) M. O’Keeffe, Chem. Soc. Rev.,
2009, 38, 1215-1217; d) H. Jiang, J. Jia, A. Shkurenko, Z. Chen, K. Adil,
Y. Belmabkhout, L.J. Weselinski, A.H. Assen, D.-X. Xue, M. O’Keeffe
and M. Eddaoudi, J. Am. Chem. Soc., 2018, 140, 8858-8867.
a) Z. Chen, S.L. Hanna, L.R. Redfern, D. Alezi, T. Islamoglu, O.K. Farha,
Coord. Chem. Rev., 2019, 386, 32-49; b) H. Furukawa, K.E. Cordova, M.
O’Keeffe, O.M. Yaghi, Science, 2013, 341, 1230444; c) H. Deng, C.J.
Doonan, H. Furukawa, R.B. Ferreira, J. Towne, A.B. Knobler, B. Wang,
O.M. Yaghi, Science, 2010, 327, 846-850; d) M. Ding, X. Cai, H.L. Jiang,
Chem. Sci., 2019, 10, 10209-10230.
[3]
[4]
[16] A.L. Spek, J. Appl. Cryst., 2003, 36, 7-13.
[17] a) W. Yang, A.J. Davies, X. Lin, M. Suyetin, R. Matsuda, AS.J. Blake, C.
Wilson, W. Lewis, J.E. Parker, C.C. Tang, M. W. George, P. Hubberstey,
S. Kitagawa, H. Sakamoto, E. Bichoutskaia, N. R. Champness, S. yang,
M. Schroder, Chem. Sci. 2012, 3, 2993-2999; b) H. Furukawa, N. Ko,
Y.B. Go, N. Aratani, S.B. Choi, E. Choi, A.O. Yazaydin, R.Q. Snurr, M.
O’Keeffe, J. Kim, O.M. Yaghi, Science, 2010, 329, 424-428.
a) O.K. Farha, A.O. Yazaydin, I. Eryazici, C.D. Malliakas, B.G. Hauser,
M.G. Kanatzidis, S.T. Nguyen, R.Q. Snurr, J.T. Hupp, Nature Chem.,
2010, 2, 944-948; b) J.L.C. Rowsell, O.M. Yaghi, J. Am. Chem. Soc.,
2006, 128, 1304-1315; c) X. Zou, G. Zhu, Adv. Mater., 2018, 30,
1700750; d) Q. Qian, P.A. Asinger, M.J. Lee, G. Han, K.M. Rodriguez, S.
Lin, F.M. Benedetti, A.X. Wu, W.S. Chi, Z.P. Smith, Chem. Rev., 2020,
120, 8161-8266; e) Y. He, Y. Zhang, L. Wojtas, N.G. Akhmedov, D. Thai,
H. Wang, X. Li, H. Guo, X. Shi, Chem. Sci., 2019, 10, 4192-4199.
a) K. Xi, S. Cao, X. Peng, C. Ducati, R. V. Kumar, A.K. Cheetham, Chem,
Commun., 2013, 49, 2192-2194; b) K. Cai, F. Sun, X. Liang, C. Liu, N.
Zhao, X. Zou, G. Zhu, J. Mater. Chem. A, 2017, 5, 12943-12950; c) H.
Zhang, X. Liu, Y. Wu, C. Guan, A.K. Cheetham, J. Wang, Chem.
Commun., 2018, 54, 5268-5288.
[5]
[6]
a) A.H. Assen, O. Yassine, O. Shekhah, M. Eddaoudi, K.N. Salama, ACS
Sens., 2017, 2, 1294-1301; b) L.E. Kreno, K. Leong, O.K. Farha, M.
Allendorf, R.P.V. Duyne, J.T. Hupp, Chem. Rev., 2012, 112, 1105-1125;
c) Y. Zhang, S. Yuan, G. Day, X. Wang, X. Yang, H.-C. Zhou, Coordin
Chem. Rev., 2018, 354, 28-45; d) B. Gui, Y. Meng, Y. Xie, J. Tian, G. Yu,
W. Zeng, G. Zhang, S. Gong, C. Yang, D. Zhang, C. Wang, Adv. Mater.,
2018, 30, 1802329.
[7]
a) T. A. Goetjen, J. Liu, Y. Wu, J. Sui, X. Zhang, J.T. Hupp, O.M. Farha,
Chem. Commun., 2020, 56, 10409-10418; b) Y. Zhao, S. Qi, Z. Niu, Y.
Peng, C. Shan, G. Verma, L. Wojtas, Z. Zhang, B. Zhang, Y. Feng, Y.
Chen, S. Ma, J. Am. Chem. Soc., 2019, 141, 14443-14450; c)F. Xie, G.-
P. Lu, R. Xie, Q.-H. Chen, H.-F. Jiang, M. Zhang, ACS Catal., 2019, 9,
2718-2724; d) M.Liu, K. Cao, Y. Fan, X. Guo, J. Wu, X. Meng, H. Hou,
Chem, Eur. J., 2018, 24, 1416-1424; e) K. Gao, H. Li, Q. Meng, J. Wu,
H. Hou, ACS Appl. Mater. Interfaces, 2021, 13, 2779-2787.
[8]
a) J. Cai, J. Yu, H. Wang, X. Duan, Q. Zhang, C. Wu, Y. Cui, Y. Yu, Z.
Wang, B. Chen, G. Qian, Cryst. Growth Des., 2015, 15, 4071-4074; b) B.
Wang, Q. Yang, C. Guo, Y. Sun, L.-H. Xie, J.R. Li, ACS Appl. Mater.
Interfaces, 2017, 9, 10286-10295; c) R. Luebke, Y. Belmabkhout, L.J.
Weselinski, A.J. Cairns, M. Alkordi, G. Norton, L. Wojtas, K. Adil, M.
Eddaoudi, Chem. Sci., 2015, 6 4095-4102; d) B. Gole, A. Bar, A. Mallick,
R. Banerjee, P. Mukherjee, Chem. Commun., 2013, 49, 7439-7441.
a) Y. Zhang, X. Zhang, J. Lyu, K.I. Otake, X. Wang, L.R. Redfern, C.D.
Malliakas, Z. Li, T. Islamoglu, B. Wang, O.K.Farha, J. Am. Chem. Soc.,
2018, 140, 11179-11183; b) J. Li, Y. He, L. Wang, G. Li, Y. Zou, Y. Yan,
D. Li, X. Shi, Z. Song, X. Shi, RSC Adv., 2020, 10, 41921-41925; c) L.
Lü, B. Mu, C.-X. Li, R.-D. Huang, J. Solid State Chem., 2016, 234, 93-
102.
[9]
[10] K. Zhao, Y. He, C. Shan, J. Ren. L. Wojtas, L. Wang, G. Li, Z. Song, X.
Shi, Chem. Eur. J., 2020, 26, 16272-16276.
[11] (a) F.A.A. Paz, J. Klinowski, S.M.F. Vilela, J.P.C. Tome, J.A.S. Cavaleiro,
J. Rocha, Chem. Soc. Rev., 2012, 41, 1088-1110; b) D. Zhao, D.J.
Timmons, D. Yuan, H.-C. Zhou, Acc. Chem. Res. 2011, 44, 123-133.
4
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Entry for the Table of Contents
A helical-shaped metal-organic framework was prepared using conformationally rigid tetratopic benzoic acid ligand with binding units
pointing toward each other (concave ligand). To avoid the obvious intramolecular interactions between binding units, matching spacing
groups was applied to introduce atropic repulsion, allowing the formation of extended frameworks for the first time. With this new ligand
design, a helical-shaped MOF was successfully prepared with significantly improved air and moisture stability, providing a new strategy
for ligand design toward porous material constructions.
5
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