Construction of isostructural hydrogen-bonded organic frameworks: limitations and possibilities of pore expansion

Article abstract of DOI:10.1039/d1sc02690a

The library of isostructural porous frameworks enables a systematic survey to optimize the structure and functionality of porous materials. In contrary to metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), a handful of isostructural f

Full text of DOI:10.1039/d1sc02690a

Volume 12
Number 28
28 July 2021
Pages 9563–9854
Chemical
Science
rsc.li/chemical-science
ISSN 2041-6539
EDGE ARTICLE
Nobuyuki Matubayasi, Abderrazzak Douhal, Ichiro Hisaki et al.
Construction of isostructural hydrogen-bonded organic
frameworks: limitations and possibilities of pore expansion

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Construction of isostructural hydrogen-bonded
organic frameworks: limitations and possibilities of
pore expansion†
Cite this: Chem. Sci., 2021, 12, 9607
All publication charges for this article
have been paid for by the Royal Society
of Chemistry
b
b
Yuto Suzuki,a Mario Gutierrez,
Senri Tanaka,c Eduardo Gomez,
´
d
c
*
Norimitsu Tohnai,
Nobuhiro Yasuda,e Nobuyuki Matubayasi,
b
a
*
*
Abderrazzak Douhal
and Ichiro Hisaki
The library of isostructural porous frameworks enables a systematic survey to optimize the structure and
functionality of porous materials. In contrary to metal–organic frameworks (MOFs) and covalent organic
frameworks (COFs), a handful of isostructural frameworks have been reported for hydrogen-bonded
organic frameworks (HOFs) due to the weakness of the bonds. Herein, we provide a rule-of-thumb to
develop isostructural HOFs, where we demonstrate the construction of the third and fourth generation
of isostructural HAT-based HOFs (TolHAT-1 and ThiaHAT-1) by considering three important structural
factors, that are (1) directional H-bonding, (2) shape-fitted docking of the HAT core, and (3) modulation
of peripheral moieties. Their structural and photo-physical properties including HCl vapor detection are
presented. Moreover, TolHAT-1, ThiaHAT-1, and other isostructural HOFs (CPHAT-1 and CBPHAT-1)
were thoroughly compared from the viewpoints of structures and properties. Importantly, molecular
dynamics (MD) simulation proves to be rationally capable of evaluating the stability of isostructural HOFs.
These results can accelerate the development of various isostructural molecular porous materials.
Received 17th May 2021
Accepted 18th June 2021
DOI: 10.1039/d1sc02690a
rsc.li/chemical-science
successfully manufactured with this methodology as follows.8–10
Yaghi and coworkers reported isostructural MOFs with pore size
Introduction
ranging from 1.4 to 9.8 nm constructed from a series of oligo-
phenylene ligands.8 Lin and coworkers reported a family of
isostructural MOFs and their catalytic activities.9 Dichtel and
coworkers reported the lattice expansion of 2D phthalocyanine
COFs by using linear diboronic acid linkers.10 However, it still
remains difficult to prepare isostructural frameworks in the
case of porous molecular crystals formed through weak inter-
molecular interactions,11,12 such as hydrogen-bonded organic
frameworks (HOFs)13–18 connected through reversible H bonds.
HOFs are available as highly crystalline materials with a large
domain via a facile recrystallization process. Additionally, if the
frameworks are damaged, they are capable of recovering and
regenerating via a wet process, such as solvent vapor annealing,
owing to the non-covalent nature of the H bonds.19 On the other
hand, the design principle to construct stable HOFs with
permanent porosity still remains unsatisfactory when
compared with MOFs and COFs, although reports of fascinating
HOFs with permanent porosity have been increasing over the
last two decades.20–26
Isostructural porous frameworks, whose molecular arrange-
ments and network topology are the same, but with different
pore sizes and chemical and physical properties, can provide an
important library for a systematic design and optimization of
the structure and properties of functional porous materials.1–6
Therefore, it is a touchstone for reticular chemistry to construct
such frameworks.7 The expansion of the pores may be readily
accomplished by elongating the length of ligand molecules or
spacer moieties. Indeed, isostructural MOFs and COFs were
aDivision of Chemistry, Graduate School of Engineering Science, Osaka University, 1-3
Machikaneyama, Toyonaka, Osaka 560-8531, Japan. E-mail: hisaki@chem.es.osaka-u.
ac.jp
b
´
´
´
Departamento de Quımica Fısica, Facultad de Ciencias Ambientales y Bioquımica,
INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, S/N, 45071
Toledo, Spain. E-mail: Abderrazzak.Douhal@uclm.es
cDivision of Chemical Engineering, Graduate School of Engineering Science, Osaka
University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan. E-mail:
nobuyuki@cheng.es.osaka-u.ac.jp
dDivision of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1
Yamadaoka, Suita, Osaka 565-7891, Japan
Homologous building block molecules of HOFs with
different lengths of arms oen gave non-isostructural, but
diverse frameworks with different molecular arrangements and
H-bonded network topologies.21–27 Only a handful of iso-
structural HOFs are known so far. Cooper, Day, and coworkers
employed triptycenetrisbenzimidazolone and its expanded
eJASRI, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan
† Electronic supplementary information (ESI) available: Details of synthesis,
characterization, thermal analysis, spectroscopic data, theoretical calculation,
and crystallographic data. CCDC 2081131, 2081132, and 2081133. For ESI and
crystallographic data in CIF or other electronic format see DOI:
10.1039/d1sc02690a
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Fig. 1 Illustration of keys 1, 2 and 3 to construct isostructural HOFs with different pore sizes. (a) Frameworks formed from triphenylene
derivatives. The molecules form isostructural hexagonal network motifs through directional H-bonding of the carboxy group (key 1), while the
stacking configurations of the derivatives differ from each other to result in non-isostructural HOFs (Tp-1 and BPTp-1). (b) Frameworks formed
from HAT-based molecules. Both molecules with carboxy-phenyl and -biphenyl groups form rigid and stable isostructural HOFs (CPHAT-1 and
CBPHAT-1) due to the uniform shape-fitted docking of the twisted HAT core (key 2). (c) Construction of isostructural frameworks with larger
pores by a systematic engineering of the arm moieties (key 3).
analogue to yield isostructural honeycomb frameworks.28,29 an answer to this question by constructing the third and fourth
Farha's, Chao's, and Chen's groups independently reported generation of isostructural HAT-based HOFs with larger pores.
pyrene-based isostructural HOFs based on pyrene derivatives The simple elongation of the arms from biphenylene to terphe-
with different substituents (carboxy, 4-carboxyphenyl, and 6- nylene (TPHAT) quickly reached the limit, while the modication
carboxynaphthalen-2-yl).19,30,31 Miljanic and coworkers also re- of the arms by 1,2-diphenylethyne (tolane) and 4,7-diphenyl-
´
ported a series of quasi-isotropic uorinated honeycomb benzo-2,1,3-thiadiazole allowed the formation of expanded
HOFs.32,33 The difficulty to obtain a set of isostructural HOFs is HOFs (TolHAT-1 and ThiaHAT-1), evidencing the importance of
clearly originated from weakness of H-bonds. Therefore, suitable arm engineering (key 3 in Fig. 1c). To our knowledge, the
a further design principle is necessary to construct isostructural present system has so far the largest number of isostructural
HOFs.
HOFs. In addition to their structures and properties, including
In connection with this, we have recently achieved the fabri- solid-state and solution uorescence behaviours, structural
cation of various isostructural hexagonal networks (HexNets) comparison between the four isostructural HOFs is also
through predictable H-bonding of C3-symmetric carboxylic acids described. Interestingly, ThiaHAT-1 exhibits a large sensitivity to
with p-conjugated cores, such as triphenylene (Tp) deriva- HCl vapours which can be recorded by UV-Vis absorption or
tives,34,35 where the most important structural factors are the emission experiments. Moreover, it is noteworthy that the
rigidity of the molecular skeletons and the highly directional and stability of HOFs can be precisely evaluated by molecular
predictable H bonds (key 1). However, the resultant HexNets dynamics (MD) simulation, reecting the importance of consid-
stack in different ways to form non-isostructural HOFs. Moreover, ering not only the interaction energy, but also the uctuation of
we show that two derivatives with even the same Tp core (Tp and the molecules. These results give an insight to develop a system-
BPTp) with carboxy-phenyl and -biphenyl arms form non- atic series of porous molecular crystalline materials.
isostructural frameworks (Fig. 1a). This is caused by the lack of
preferable unique stacking geometry between the molecules.
Meanwhile, we have demonstrated that two hexaazatriphenylene
Results and discussion
Synthesis and crystallization
(HAT) derivatives (CPHAT and CBPHAT) with carboxy-phenyl and
-biphenyl arms, respectively, yielded isostructural HOFs (Fig. 1b),
where the crucial structural factor is a twisted conformation of
the HAT core that enables the molecule to stack uniformly
through shape-tted docking (key 2).36,37
HAT derivatives, TPHAT, TolHAT, and ThiaHAT, were synthe-
sized as shown in Scheme 1. 1,2-Dione derivative 3a with a tol-
ane moiety was prepared by the Sonogashira coupling reaction
of 4,40-dibromobenzil (1) and hexyl 4-ethynyl-benzoate (2).
Dione derivatives 3b with terphenyl moieties and 3c with 4,7-
diphenyl-benzo-2,1,3-thiadiazole moieties were synthesized by
Can HAT derivatives with further elongated arms provide
another isostructural HOF with larger pores? Herein, we provide
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Scheme 1 Synthesis of (a) 3a, (b) 3b and 3c, and (c) TPHAT, TolHAT, and ThiaHAT.
the Suzuki–Miyaura cross-coupling reaction of 4,40-(pina- TolHAT-1 has the cell parameters of a ¼ b ¼ 59.529(1) A, c ¼
˚
3
˚
˚
colboryl)benzil derivative
nylcarboxylate derivatives
4
5
with hexyl 40-bromobiphe- 6.9637(2) A, and V ¼ 21 371.4(8) A and ThiaHAT-1 has a ¼ b ¼
3
˚
˚
˚
and 6, respectively. Then 65.827(5) A, c ¼ 6.9879(7) A, and V ¼ 26 223(4) A (Table S1†).
hexaaminobenzene, which was prepared by the reduction of The latter has a slightly elongated framework due to the longer
1,3,5-triamino-2,4,6-trinitrobenzene (7),38 was triply condensed arms of the building block molecule. Both molecules have D3h
-
with the corresponding dione derivatives 3a–c under acidic symmetry and are stacked via shape-tted docking of the HAT
˚
conditions to afford HAT derivatives with ester groups 9a–c, cores with intermolecular distances of 3.49 A to form one-
respectively. The hydrolysis of 9a–c gave the building block dimensional (1D) columns. The root means square deviations
molecules TolHAT, TPHAT, and ThiaHAT, respectively. As (RMSDs) of the HAT cores of TolHAT and ThiaHAT in the
˚
˚
a reference compound, BPTp with carboxybiphenyl groups was crystals are 0.215 A and 0.229 A, respectively. Their torsion
also synthesized and crystallized (for details, see ESI Sections 2 angles between adjacent aryl arms in the ortho-positions are
and 3†).
23.5ꢀ and 24.5ꢀ, respectively. The optimized structures obtained
To get the HOFs, the synthesized HAT derivatives were at the B3LYP/6-31G(d) level show more planar conformations
˚
˚
recrystallized by slow evaporation from a mixed solution of N,N- (RMSD on the HAT core: 0.111 A for TolHAT and 0.108 A for
dimethylacetamide (DMA) and an aromatic solvent [1,2,4- ThiaHAT; and torsion angles between arms: 17.8ꢀ for TolHAT
trichlorobenzene (TCB) or 1,2,4-trimethylbenzene (TMB)] at and 16.7ꢀ for ThiaHAT (see ESI Section 5†)), indicating that
60 ꢀC for TolHAT and TPHAT and at 120 ꢀC for ThiaHAT. TPHAT packing forces signicantly induced the molecular distortion of
gave pale green precipitates (TPHAT-P) (Fig. 2a), which only the HAT moieties in the crystalline states.
showed weak and broad peaks in the powder X-ray diffraction
In TolHAT-1 and ThiaHAT-1, the HAT derivatives form
(PXRD) pattern (Fig. S1†). TolHAT, on the other hand, gave yellow dimers of carboxyl groups through H bonds to provide 3D
green needle-like single crystals (TolHAT-1) with a width of 5–20 networks with a pcu-topology (Fig. 3i). The networks are 8-fold
mm and a length of over 100 mm (Fig. 2b). Similarly, ThiaHAT interpenetrated to give the whole frameworks possessing large
yielded yellow needle-like microcrystals (ThiaHAT-1) with a width C3-symmetric 1D pores with a triangular aperture. The height
˚
˚
of approximately 10 mm and a length of over 100 mm (Fig. 2c). and base of the aperture in TolHAT-1 are 19.2 A and 20.4 A,
˚
˚
TolHAT-1 and ThiaHAT-1 were subject to single-crystalline X-ray respectively, and those of ThiaHAT-1 are 18.0 A and 19.4 A,
diffraction (SCXRD) measurements with synchrotron X-ray radi- respectively (Fig. 3d and h). Although ThiaHAT has a longer arm
ation to pin-point their crystalline structure.
than TolHAT, the pores of ThiaHAT-1 are smaller than those of
TolHAT-1 because of the bulky thiadiazol groups of ThiaHAT.
The void ratios of ThiaHAT-1 and TolHAT-1 are 48% and 55%,
respectively, which were calculated by using PLATON soware
Crystallography
ꢀ
TolHAT and ThiaHAT crystallized into the space group R3c to
yield porous frameworks (TolHAT-1 and ThiaHAT-1) (Fig. 3).
39
˚
with a probe radius of 1.2 A.
It should be noted that the arms of the ThiaHAT molecule
are disordered in two positions A and B with a site occupancy of
0.662 and 0.338, respectively (Fig. 3j). The carboxy group in site
A forms a typical complementary H-bonded dimer with an
ꢀ
˚
O–H/O distance and an angle of 2.6 A and 170 , respectively,
while the group in site B forms a truncated dimer with an
O–H/O distance and a dihedral angle between carboxylate
ꢀ
˚
planes of 2.7 A and 59 , respectively (Fig. 3i). In both confor-
mations, the benzothiadiazole groups are inclined into the pore
and aligned vertically along the c axis (Fig. S4 and S5†).
Fig. 2 Polarized optical microscopy (POM) images of (a) TPHAT-P, (b)
TolHAT-1, and (c) ThiaHAT-1 under daylight. Scale bar: 100 mm.
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Fig. 3 Crystal descriptions of (a–d) TolHAT-1 and (e–h) ThiaHAT-1. (a and e) Twisted nonplanar conformations viewed down the c axis (top) and
the ab planes (bottom). (b and f) Packing diagrams. (c and g) 1D columns formed by shape-fitted docking of the HAT derivatives. (d and h)
Visualized void surfaces viewed down the c axis (top) and the ab planes (bottom) (yellow: inside and cyan: outside). (i) A H-bonded pcu-
topological network, which interpenetrates by 8-fold to form the frameworks of TolHAT-1 and ThiaHAT-1. (j) The disordered arms of ThiaHAT-1
into two positions A and B with an occupancy of 0.662 and 0.338, respectively. (k) H-bonded dimers formed from the arms A and B. A structure in
site B is not shown in (e–h).
Further structural comparison is conducted focusing on the Adjacent Ar-III moieties were assembled nearly parallel (15.0ꢀ)
assembling position of the arm moieties in TolHAT-1 and via face-to-face p stacking. Similarly, TolHAT-1 has a small
ThiaHAT-1, as well as in previously reported HOFs, CPHAT-1 torsion angle (ꢁ15.1ꢀ) between Ar-I and Ar-III rings because of
and CBPHAT-1 (Fig. 4). The benzene rings directly bonded to the less sterically hindered ethynyl moiety, resulting in parallel
the HAT core are labeled Ar-I. Similarly, the benzene rings face-to-face p stacking of the adjacent Ar-III rings. On the other
adjacent to the terminal carboxyl group are labeled Ar-III in hand, it is difficult for ThiaHAT-1 to form the same parallel
CBPHAT, TolHAT, and ThiaHAT. The middle moieties between assembly of the arms due to bulky Ar-II rings, i.e. a benzothia-
Ar-I and Ar-III rings are labeled Ar-II in ThiaHAT. The dihedral diazole (Tz) group. The Tz group is twisted by 37.4ꢀ and 18.8ꢀ
angles of the neighbouring aryl groups (i.e. the HAT core, Ar-I, against Ar-I and Ar-III, respectively. Adjacent Tz groups interact
Ar-II, and Ar-III) are listed in Table 1. The torsion angles through face-to-edge CH/p interactions with a contact angle of
between Ar-I and the core are 23.5ꢀ for CPHAT, 25.5ꢀ for 58.5ꢀ. Every other Tz group is oriented in the same direction and
CBPHAT, 25.6ꢀ for TolHAT, and 28.2ꢀ for ThiaHAT. The assembled through multiple dipole–dipole interactions.40,41
distortions are similar to each other. Ar-I rings are aligned via There is also an intermolecular H-bonding interaction between
edge-to-face CH/p interaction with a contact angle of 33.6ꢀ Ar-II nitrogen and Ar-I hydrogen atoms of two molecules away
(CPHAT), 38.1ꢀ (CBPHAT), 37.1ꢀ (TolHAT), and 46.5ꢀ (ThiaHAT). (Fig. S5†). Consequently, the introduction of the Tz group forces
The contact angles of all these HOFs follow the same tendency the arm to have a limited conformation, which, combined with
as the distortion described above with the exception of ThiaHAT shape-tted docking of the HAT core, induces the ThiaHAT
due to the bulky group.
molecules to be organized into a crystalline framework.
On the basis of the aforementioned results, we suggest that,
In previously reported CBPHAT-1, Ar-I and Ar-III were twisted
moderately (ꢁ26.7ꢀ), and their rotation direction was opposite in the case of TPHAT, the conformations of the terphenyl arm
to the rotation direction between the core and Ar-I. Therefore, may not be suitable either for attractive face-to-face or for face-
the torsion angle between the core and Ar-III was only ꢁ16.0ꢀ. to-edge interaction, preventing the formation of crystalline
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Fig. 4 Arm assembling behaviour of (a) CPHAT-1, (b) CBPHAT-1, (c) TolHAT-1, and (d) ThiaHAT-1 from the orthogonal two different views (left
and right). (e–h) Contact structures of aryl rings (left: Ar-I, center: Ar-II, and right: Ar-III) in CPHAT-1, CBPHAT-1, TolHAT-1, and ThiaHAT-1,
respectively. (Inset) Chemical structures of stacking HAT derivatives. The aromatic rings in the order adjacent to the HAT core are defined as I
(purple), II (cyan), and III (yellow), respectively. The HAT core is coloured in gray.
Table 1 Dihedral angles among the core and aromatic rings in the arm moiety
CPHAT/ꢀ
CBPHAT/ꢀ
TolHAT/ꢀ
ThiaHAT (A site)/ꢀ
ThiaHATa (B site)/ꢀ
Core-I
23.5
—
—
—
—
25.5
—
25.6
—
28.2
61.6
80.4
37.4
55.5
18.8
28.2
62.6
41.7
38.5
65.6
76.6
Core-II
Core-III
I and II
I–III
ꢁ16.0
ꢁ19.1
—
—
ꢁ26.7
—
ꢁ15.1
—
II and III
—
a
Details are shown in Fig. S6.
porous frameworks. Additionally, considering the above inter- trimethylbenzene (TMB) instead of DMA and TCB because of its
pretation, it could be possible to construct isostructural HOFs more prominent PXRD pattern, although both of them have the
with further expanded pores by varying the bulkiness of elon- same framework structure (Fig. S7†). TG analysis of TolHAT-1
gated arms. Namely, molecules with no steric hindrance shows a stepwise curve with no clear plateau, indicating that
between arm components, such as TolHAT, could form HOFs solvent molecules were released from the pore in two steps: up
through simply face-to-face p stacking, while those with steri- to approximately 80 ꢀC and up to 300 ꢀC (Fig. S8†).37 PXRD
cally hindered arm components, such as ThiaHAT, could also patterns were recorded with increasing temperatures to follow
produce HOFs through edge-to-face interactions among con- the structural changes in the framework induced by guest
formationally restricted arm components.
removal (Fig. 5a). The intensity of diffraction peaks such as
ꢀ
ꢀ
ꢀ
ꢀ
those at 2q ¼ 2.96 and 5.94 , ascribable to the (2 1 0) and (4 2 0)
planes, respectively, slightly increases upon removal of the
disordered solvent molecules up to 85.5 ꢀC (red line). Then, the
intensity of the peaks at 2q ¼ 2.96ꢀ and 5.94ꢀ decreases at higher
temperatures, and instead, weak peaks at 2q ¼ 3.60ꢀ and 5.06ꢀ
were recorded, indicating a structural transition. This temper-
ature corresponds to the second stage of guest removal in the
Thermal analysis and activation
To investigate their thermal behavior, thermal gravimetric (TG)
and variable temperature (VT) PXRD analyses were conducted
on the as-formed crystals of HOFs. The crystalline bulk of Tol-
HAT-1 was prepared from a mixed solution of DMA and 1,2,4-
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Fig. 5 (a) Variable temperature (VT)-PXRD patterns of the as-formed HOF TolHAT-1. (b) PXRD patterns of activated HOF TolHAT-1aN (N ¼ I–IV)
with the simulation pattern of TolHAT-1. (c) VT-PXRD patterns of TolHAT-1aIV from rt to 360 ꢀC. Red line indicates the temperature where the
network begins to collapse and blue line corresponds to the temperature where the framework is fully collapsed. The asterisk (*) denotes a non-
identifiable peak appeared for the activated TolHAT samples.
TG curve, indicating that the structural transition coincides their intensities increase over 100 ꢀC until reaching a plateau at
with the removal of guest molecules from the framework.
170 ꢀC due to the removal of severely disordered TCB molecules,
Keeping this in mind, the activation (i.e. removal of solvent which is frequently observed for HOFs.35–37 The original
molecules lling the pores) of TolHAT-1 was performed by the diffraction peaks are retained up to 305 ꢀC; however, higher
following four methods: (I) heating at high temperature (120 ꢀC) temperatures produce a rapid decrease of the intensity of the
under vacuum; (II) immersing in benzene to exchange the (100) peak, evidencing the collapse of the framework.
trapped solvent with benzene molecules followed by heating at
The activation of ThiaHAT-1 was, therefore, conducted by
relatively low temperature (80 ꢀC) under vacuum; (III) method I described above. Heating under vacuum allowed the
immersing in benzene followed by freeze-drying; (IV) formation of an activated framework ThiaHAT-1a (Fig. 6b),
immersing sequentially in dichlorobenzene, chlorobenzene, which maintained its structure and crystallinity. Other
toluene, and benzene, followed by freeze-drying. The complete
removal of the solvent from the activated materials was
conrmed by 1H-NMR spectroscopy (Fig. S9†). PXRD patterns of
the materials activated by methods I–IV, termed TolHAT-1aN (N
¼ I–IV), were recorded (Fig. 5b). The crystallinity of TolHAT-1aI
and TolHAT-1aII was completely lost. However, TolHAT-1aIII
retained its crystallinity, while one non-identiable peak
appeared at 3.60ꢀ, which may be ascribable to another phase
partially formed by the transformation of the original frame-
work. By a more controlled exchange of the solvent molecules,
the intensity of the peak became weaker (TolHAT-1aIV), but still
present, revealing that the framework of TolHAT-1a is quite
fragile and prone to undergoing phase transition.
The obtained TolHAT-1aIV was then subject to VT-PXRD
measurements (Fig. 5c). The intensity of the peak at 2q ¼
ꢀ
2.96ꢀ starts to decrease at 190 C (the pattern coloured in red)
and vanishes at 298 ꢀC (blue line) (Fig. 5c and S10†). This
behaviour is in contrast with that of a HOF based on hexakis[(4-
carboxyphenyl)ethynyl]benzene, which is stable at high
temperatures up to 300 ꢀC, as reported by Chen and
coworkers.27
Thermal analysis of ThiaHAT-1 was conducted (Fig. 6). The
TG curve shows two-step release of solvent (TCB) molecules,
suggesting that TCB molecules are in two different locations in
the voids corresponding to the middle and the corner ones.37
The curve reaches a plateau at 180 ꢀC, indicating a complete
removal of solvent molecules. The HOF was also subject to VT-
PXRD experiments (Fig. 6c). The PXRD peaks of the as-formed
ThiaHAT-1 show no shi at different temperatures, while
Fig. 6 (a) TG profiles of ThiaHAT-1 (green line) and ThiaHAT-1a (red
line). (b) PXRD pattern of ThiaHAT-1a activated via method I with the
simulation pattern of ThiaHAT-1. (c) VT-PXRD patterns of ThiaHAT-1
heated from RT to 360 ꢀC. Inset: changes of the (100) peak intensity of
ThiaHAT-1 with temperature. The intensity rapidly decreased from
305 ꢀC (red line), which indicated the collapse of the framework and
no peak was detected at over 330 ꢀC.
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activation methods also yielded the same activated HOFs on the other hand, show a signicant uptake of gasses [N2: 18.3,
(Fig. S11†). The activation completion was conrmed by the 1H- O2: 21.9, CO2: 13.8, and H2: 3.28 mmol(STP) gꢁ1] (Fig. 7b). The
NMR spectrum of the material dissolved in DMSO-d6 BET surface area and pore width were calculated to be 1394 m2
(Fig. S12†). This ThiaHAT-1a was also subject to VT-PXRD gꢁ1, and 1.58 nm, respectively, which are larger than those of
experiments, showing that the crystalline network is stable up CBPHAT-1a.
to 305ꢀ (Fig. S13†).
Computational evaluation of stability
Evaluation of the stability and porosity of HOFs
To investigate the stability of the HOFs, the intermolecular
To evaluate the chemical stability, the activated HOFs were
immersed in various solvents and solutions (water, conc. HClaq
interactions and extents of structural disorder were calculated.
Firstly, complexation energies between two stacked molecules
in HOFs were calculated (Fig. 8). The stability increases pro-
portionally to the arm length in the cases of CPHAT-1 (ꢁ38.4 to
ꢁ58.4 kcal molꢁ1), CBPHAT-1, (ꢁ63.9 to ꢁ90.9 kcal molꢁ1) and
TolHAT-1 (ꢁ82.1 to ꢁ108.6 kcal molꢁ1). This result suggests
that TolHAT should have been more stable than CPHAT-1 and
CBPHAT-1. In the case of ThiaHAT, the increase of stabilization
energy (ꢁ74.0 to ꢁ112.7 kcal molꢁ1) becomes slow; particularly
the energy calculated at the M062X level is smaller than that of
TolHAT, which is caused by the face-to-edge contact of the arm
moieties. These results indicate that the stability of the HOFs
cannot be evaluated from complexation energies.
Secondly, to assess the structural disorders of the HOFs, all-
atom MD (molecular dynamics) simulations were conducted at
300 K and 1 bar on the frameworks of CPHAT-1, CBPHAT-1,
TolHAT-1, and ThiaHAT-1. The procedures of MD are described
in the ESI,† and snapshot congurations of CPHAT-1 and Tol-
HAT-1 seen from the c-axis are depicted in Fig. 9a as represen-
tative examples. The structural disorder is more evident in the
arm parts than in the HAT cores, and the disorder of the arm is
larger for TolHAT-1 than for CPHAT-1. The extent of disorder
can be quantied in terms of the root-mean-square displace-
ment (RMSD) averaged over all the heavy (non-hydrogen) atoms
in the system. In the present work, RMSD was computed for the
uctuations in the a- and b-directions. A RMSD plot over the
time course of MD for 10 ns (Fig. 9b) shows that the frameworks
formed by the H bonds are stable at 300 K. The disorder of the
framework represented by RMSD is larger in the order of Tol-
HAT-1 > CBPHAT-1 > ThiaHAT-1 > CPHAT-1, and this is in fair
correspondence with the experimentally observed decomposi-
tion temperatures of the frameworks, which reects a higher
stability of the framework in the order of CPHAT-1 > CBPHAT-1
,
NaOHaq, ethanol, CHCl3, and diethyl ether) and tested through
PXRD measurements (Fig. S14†). For the case of TolHAT-1aIV,
its crystallinity is lower than that of the original, indicating that
the introduction and removal of guest molecules caused
a partial collapse of the framework. The PXRD patterns of
ThiaHAT-1a, on the other hand, retain the original diffraction
prole, indicating its good stability in various solvents.
However, the porosity aer being immersed in conc. HClaq and
NaOHaq became lower than that of pristine ThiaHAT-1a
(Fig. S15, S20, and Table S2†).
The permanent porosity of the activated frameworks of
TolHAT-1 and ThiaHAT-1, as well as TPHAT-1 (Fig. S18–S20†),
was evaluated by gas adsorption experiments at ꢁ196 ꢀC for N2,
O2, and H2 and at ꢁ78 ꢀC for CO2. For the case of TolHAT-1aN (N
¼ I–IV), the uptake of N2 gas varied with the activation method
(Fig. S19, S20, and Table S3†) and TolHAT-1aIV showed the
highest porosity among them (SA: 330 m2 gꢁ1 and pore width:
1.66 nm) (Fig. 7a). This demonstrates the importance of
a controlled activation. The gas uptakes and BET surface area of
TolHAT-1aIV are yet lower than those of CBPHAT-1a (SA: 1288
m2 gꢁ1, Table S4†), suggesting that a large part of the original
structure was collapsed or transformed into a less- or non-
porous structure. The gas sorption isotherms of ThiaHAT-1a,
Fig. 7 (a and c) Gas sorption isotherms and (b and d) pore distribution
of (a and b) TolHAT-1aIV and (c and d) ThiaHAT-1a. The isotherms Fig.
8
Complexation energy–linker length plot of CPHAT-1,
were recorded at ꢁ196 ꢀC for N2, O2, and H2 and at ꢁ78 ꢀC for CO2. CBPHAT-1, TolHAT-1, and ThiaHAT-1, calculated at the B3LYP-D3/6-
Solid and open symbols denote absorption and desorption processes, 311G(d,p), M062X/6-311G(d,p) and wB97XD/6-311(d,p) levels with the
respectively.
counterpoise method for BSSE correction.
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Vis steady-state absorption and emission spectroscopy and
time-resolved emission and single crystal uorescence micros-
copy. Unfortunately, during the experiments, TolHAT-1 was
revealed to be unstable under UV light excitation, probably due
to the presence of the ethynyl moieties of TolHAT-1, which can
be a breaking point of the structure upon its excitation with
high energies (Fig. S22†). In contrast, ThiaHAT-1 exhibits an
excellent stability under light irradiation, even under fs-laser
excitation conditions. ThiaHAT-1 crystalline powder displayed
a bright yellow emission upon illumination with UV light (365
nm), with an emission quantum yield of 8%. A foreground of
the photoproperties of ThiaHAT-1 is shown in Fig. 10.
UV-Vis steady state properties
The absorption spectrum of ThiaHAT-1 crystalline powder
consists of two broad bands with intensity maxima located at
ꢂ435 and 600 nm (Fig. 10a). Consequently, the emission spec-
trum strongly depends on the excitation wavelength. For exci-
tation wavelengths lower than 500 nm, the emission spectrum
of ThiaHAT-1 is a broad band with the maximum intensity
centered at 565 nm, while its excitation with wavelengths longer
than 500 nm produces a red-shied emission spectrum, with
the intensity maximum showing up at 644 nm (Fig. 10a). Both,
the absorption and emission spectra of ThiaHAT-1 are red-
shied when compared to its isostructural HOF, CBPHAT-1
(abs. 435 nm; em. 500 nm),37,43 reecting a stronger charge
transfer (CT) character. Interestingly, as commented above,
ThiaHAT-1 presents additional absorption (600 nm) and emis-
sion (644 nm) bands that are not observed for CBPHAT-1.37,43
There exists two plausible explanations: (i) the building blocks
of ThiaHAT-1 are strongly interacting through H bonds, pre-
forming anionic species in the ground state. Similar red-shied
absorption and emission bands owing to anions have been
described for other HOFs in the presence of NaOH.43 (ii) The
intrinsic structure of ThiaHAT-1 induces a higher interaction
between crystals, leading to the formation of aggregates, which
will absorb and emit less energetic electromagnetic radiation.
To shed more light on this and other aspects of the photo-
dynamical properties of ThiaHAT-1, its time-resolved photo-
behavior was investigated by means of a picosecond (ps) time-
correlated single photon counting (TCSPC) system.
Fig. 9 (a) Snapshot configurations of CPHAT-1 and TolHAT-1 seen
from the c-axis. (b) RMSD during the time course of MD. (c) Correlation
plots of the total RMSD against the contributions from the HAT core
and arm parts. RMSD was computed for the fluctuations of the heavy
(non-hydrogen) atoms in the system along the lateral (a and b)
directions. The (total) RMSD values that are plotted in (b) and refer to
the abscissa in (c) were calculated over all the heavy atoms. In (c), the
RMSDs averaged over 10 ns are shown.
ꢂ ThiaHAT-1 > TolHAT-1. The above correspondence is actually
reminiscent of the Lindemann criterion which states that the
crystal with a larger RMSD will be “closer” to melting. Our
RMSD (computed along the lateral directions) can thus describe
the crystal stability. RMSD is a quantity readily obtained in MD
simulations, and it will be of use for predicting the stability of
a HOF.
Fig. 9c further shows the RMSDs computed separately over
the HAT core and arm parts. The RMSD is smaller for the HAT
core than for the arm. As Fig. 9a shows, the structural disorder
is more pronounced in the arm part. The correlation with the
total RMSD is seen for the arm RMSD. The crystal stability is
thus governed by the extent of disorder of the arm part, and
therefore, a rule-of-thumb for producing more stable HOFs
would be the design of arms with suppressed uctuations.
TCSPC observations
The photodynamic properties of ThiaHAT-1 were explored by
exciting (ps laser pulses) the sample at 371 and 515 nm and
collecting the emission decays at several wavelengths, which
were then analysed using a multiexponential global t method.
The obtained results show a comparable multiexponential
photobehavior independently of the excitation wavelength, with
time constants of: s1 ¼ 160–180 ps, s2 ¼ 710–720 ps, and s3 ¼
2.3–2.5 ns (Fig. 10b, c and Table S8†). The contribution of the
shortest component (s1) to the signal is higher in the bluest
region of the spectrum, while the longest component (s3)
Photophysical properties
Since porous molecular crystals are promising materials for contributes more to the emission decays recorded at longer
photophysical materials,42 the photophysical properties of Tol- wavelengths. Based on that, and following the steady state
HAT-1 and ThiaHAT-1 were evaluated by a combination of UV- discussion, the s1 component can be attributed to the species
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Fig. 10 (a) Absorption and emission spectra of ThiaHAT-1 in the powder form. The excitation wavelengths are indicated in the inset. (b and c)
Emission decays of ThiaHAT-1 in the powder form upon excitation at (b) 371 nm and (c) 515 nm. The solid lines are from the best multiexponential
global fit and the recorded wavelengths are indicated in the figure. (d) Absorption and emission spectra of ThiaHAT-1 in DMF suspension. For
emission, the excitation wavelength was 410 nm. (e) fs-Emission decays of ThiaHAT-1 in DMF suspension. The solid lines are from the best
multiexponential global fit and the IRF is the instrumental response function.
initially excited, which deactivate from the rst singlet excited reecting the occurrence of different photoreactions. However,
state (S1), while the longest s3 component corresponds to the while the shortest s1 component rises from wavelengths longer
emission of the anionic species. This is further supported by the than 500 nm, the longest s2 one only rises in the reddest part
increase in the total contribution of this component when (from 650 nm). Based on our previous explanations, where the
excited at 515 nm, which may indicate that the red-shied anion species uoresce at the longest wavelengths, it is
absorption and emission bands could have originated from reasonable to attribute the 4.4 ps component to an excited-state
the anionic species. On the other hand, as described previously, PT reaction. The shortest 450-fs component, which rises from
ThiaHAT-1 also exhibits a strong CT character, and therefore, 500 nm, can be therefore associated with an ultrafast CT event,
the intermediate component (s2) can be ascribed to the emis- leading to the formation of the species having a CT character,
sion of these CT species. The isostructural CBPHAT-1 had also
exhibited a multiexponential behavior with time components
assigned to species initially excited, others undergoing a CT and
anions.37,43
Ultrafast dynamics
To unveil the ultrafast dynamics of the proton transfer (PT) and
CT reactions, ThiaHAT-1 crystals dispersed in a DMF solution
were investigated by means of an ultrafast femtosecond (fs) up-
conversion (emission) technique. Prior to the fs-experiments,
we evaluated the steady state properties of ThiaHAT-1 in DMF
(Fig. 10d). The absorption spectrum is now better dened with
narrow bands having their intensity maxima at 208 and 410 nm,
while the emission spectrum has its maximum at 510 nm.
Subsequently, a suspension of ThiaHAT-1 in DMF was pumped
with a 410-nm fs-laser and its emission was probed at different
wavelengths ranging from 450 to 650 nm (Fig. 10e). The fs-
Fig. 11 Acid responsiveness of ThiaHAT-1. (a) Photographs of the
crystalline powder before (left) and after (right) being exposed to HCl
under daylight (top) and UV light (365 nm, bottom). (b) Absorption, (c)
emission and (d) normalized emission spectra of ThiaHAT-1 before
emission decays are well tted to a double exponential func-
tion with time constants of s1 ¼ 450 fs and s2 ¼ 4.4 ps and an
offset of ꢂ320 ps (Table S9†). Both time components decay in
the highest energetic regions and rise in the lowest ones, and after being exposed to vapors of HCl.
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Table 2 Summary of the structural features and properties of the four isostructural HOFs based on HAT derivatives
CPHAT-1
CBPHAT-1
TolHAT-1
ThiaHAT-1
˚
Periodicity of the framework/A
18.66
0.267
3.59
22.5
4
19.75
0.205
3.57
22.1
6
14.5
0.45
12.4
1288
361.7
304.5
307
29.77
0.215
3.49
23.5
8
19.2
0.55
16.6
440
32.91
0.229
3.49
24.5
8
18.0
0.48
15.5
1394
415.7
313.9
305
˚
RMSD of the HAT core plane/A
˚
Stacking distance/A
Torsion angle of arms/ꢀ
Number of interpenetrations
˚
Height of the channel aperture/A
Void ratio
6.4
0.31
a
˚
Pore width based on NLDFT/A
—
BET surface area/m2 gꢁ1
N2 uptake/mL(STP) gꢁ1
CO2 uptake/mL(STP) gꢁ1
Decomposition temp./ꢀC
Ref.
649
21.39
137.4
339
155.2
168.6
190
Ref. 36
Ref. 37
This work
This work
a
Not determined.
which relax to the ground state within a time of 720 ps as illumination (Fig. 11a). Indeed, the absorption spectrum of
described in the TCSPC part.
ThiaHAT-1 crystals aer being dosed with HCl displays an
increase in the intensity of the band at 600 nm (Fig. 11b). The
emission spectrum of ThiaHAT-1 suffers from
a strong
Single crystal microscopy
quenching (up to 98% of the initial intensity) upon interaction
with HCl vapors (Fig. 11c). Additionally, a new band with its
intensity maximum located at 700 nm is recorded (Fig. 11d).
The increase in the intensity of the red-shied bands reects
a protonation of ThiaHAT-1. Apart from the thiadiazole group,
this HOF contains several N atoms susceptible to being
protonated, so the interaction with a strong acid like HCl will
induce the protonation, producing the observed changes.
Remarkably, ThiaHAT-1 retains the dark brown colour and
quenched emission aer its dosing with HCl, making this HOF
a promising candidate to fabricate an HCl vapochromic smart
sensor. The idea behind this is that if at any time the HOF
interacts with HCl, it will retain the information until checked.
Additionally, the yellow colour and the emission of ThiaHAT-1
can be partially recovered (up to 55% of the initial emission
intensity) by heating the sample at 130 ꢀC for 18 hours
(Fig. S26†), so there is a possibility to reuse this material. It is
noteworthy that acetic acid (AcOH) did not alter the absorption
spectrum of ThiaHAT-1 and just slightly quenched its emission
(Fig. S27†). This can be explained in terms of the weak acidity of
acetic acid, which cannot efficiently protonate the HOF.
The emission properties of ThiaHAT-1 were also appraised at
a single crystal level using a ps time-resolved confocal uores-
cence microscope. The emission spectra obtained for different
isolated crystals are reminiscent of that obtained for the bulk
material (Fig. S23†). Similarly, the ps-photodynamical behav-
iour provides time constants of 300 ps, 800 ps and 2.7 ns
(Fig. S24 and Table S10†), which are comparable to those
observed in the bulk, and therefore, can be attributed to the
initially excited species (300 ps), species having CT character
(800 ps) and anions (2.7 ns). Interestingly, the emission recor-
ded for the ThiaHAT-1 single crystals is highly anisotropic,
showing a histogram with a value of around 0.45 when the
crystals are oriented perpendicularly to the plane of observa-
tion, and a value of ꢁ0.1 aer their rotation by 90ꢀ (Fig. S25†).
This fact clearly evidences that ThiaHAT-1 has a highly ordered
structure, where the fundamental units are arranged through
p–p stacking interactions along the length axis of the crystal
while the dipole moments are oriented perpendicularly.
Luminescence vapochromic sensing
ThiaHAT-1 has exhibited an outstanding response to the pres-
ence of HCl vapors, which can be easily inspected by the naked
eye under daylight or UV irradiation. Short time exposure (5 min
Conclusion
to 1 h) to HCl vapors induced a strong colour change of Thia- In this work, we synthesized three HAT derivatives (TPHAT,
HAT-1 powder from vibrant yellow to dark brown, and disap- TolHAT, and ThiaHAT) and explored the construction of iso-
pearance of strong yellow emission was observed upon UV light structural HOFs with larger pores through arm engineering.
9616 | Chem. Sci., 2021, 12, 9607–9618
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The simple elongation of arms from biphenylene to terpheny-
lene quickly reached the limit, while the modication of the
arms with 1,2-diphenylethyne and 4,7-diphenylbenzo-2,1,3-
thiadiazole allowed the formation of expanded HOFs (Tol-
HAT-1 and ThiaHAT-1). Especially, ThiaHAT-1 showed a great
Notes and references
1 A. G. Slater and A. I. Cooper, Science, 2015, 348, aaa8075.
2 C. S. Diercks, Y. Liu, K. E. Cordova and O. M. Yaghi, Nat.
Mater., 2018, 17, 301–307.
3 M. J. Kalmutzki, N. Hanikel and O. M. Yaghi, Sci. Adv., 2018,
4, aat9180.
4 C. Gropp, S. Canossa, S. Wuttke, F. Gandara, Q. Li,
L. Gagliardi and O. M. Yaghi, ACS Cent. Sci., 2020, 6, 1255–
1273.
5 J. Li, P. M. Bhatt, J. Li, M. Eddaoudi and Y. Liu, Adv. Mater.,
2020, 32, 2002563.
6 W. Xu, B. Tu, Q. Liu, Y. Shu, C. C. Liang, C. S. Diercks,
O. M. Yaghi, Y. B. Zhang, H. Deng and Q. Li, Nat. Rev.
Mater., 2020, 5, 764–779.
7 O. M. Yaghi, M. J. Kalmutzki and C. S. Diercks, Introduction
to Reticular Chemistry: Metal-Organic Frameworks and
Covalent Organic Frameworks, Wiley, 2019, ISBN 978-3-527-
3450-1.
8 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. O'Keeffe, O. Terasaki, J. F. Stoddart and
O. M. Yaghi, Science, 2012, 336, 1018–1023.
9 T. Zhang, K. Manna and W. Lin, J. Am. Chem. Soc., 2016, 138,
3241–3249.
ꢀ
stability even at high temperatures (up to 305 C), a high BET
surface area of 1394 m2 gꢁ1, and irreversible HCl responsivity in
spectroscopy. Moreover, it is noteworthy that the stability of
HOFs can be precisely evaluated by MD simulation, reecting
the importance of considering not only the interaction energy,
but also the uctuation of the molecules. We gave details on the
photobehavior of ThiaHAT-1 as crystals and in solutions
providing information on the dynamics from the fs to the ns
regime. Remarkably, ThiaHAT-1 shows a large sensitivity to HCl
vapors which can be followed by either absorption or emission
measurements. These results give an insight to develop
a systematic series of porous molecular crystalline materials. To
summarize, a comparison of the structural, chemical and
robustness properties of this series of isostructural HAT HOFs is
shown in Table 2.
´
Author contributions
Y. S. designed, synthesized and characterized all materials,
evaluated the properties of the materials and co-wrote the
paper. M. G. designed, performed and analyzed the femto-
second experiments, and co-wrote the paper. E. G. performed
and analyzed the absorption and uorescence experiments, and
evaluated acid responsiveness. S. T. conducted the MD
calculation. N. T. contributed to the gas sorption and VTPXRD
measurements. N. Y. contributed to the synchrotron X-ray
radiation experiments. N. M., A. D. and I. H. planned and
supervised the research, analyzed the data and co-wrote the
paper. All authors discussed the results and commented on the
manuscript. I. H. led the project.
10 E. L. Spitler, J. W. Colson, E. J. Uribe-Romo, A. R. Woll,
M. R. Giovino, A. Saldivar and W. R. Dichtel, Angew. Chem.,
Int. Ed., 2012, 51, 2623–2627.
11 I. Bassanetti, S. Bracco, A. Comotti, M. Negroni,
´
C. Bezuidenhout, S. Canossa, P. P. Mazzeo, L. Marchio and
P. Sozzani, J. Mater. Chem. A, 2018, 6, 14231–14239.
12 G. Xing, I. Bassanetti, S. Bracco, M. Negroni,
C. Bezuidenhout, T. Ben, P. Sozzani and A. Comotti, Chem.
Sci., 2019, 10, 730–736.
13 Y. F. Han, Y. X. Yuan and H. B. Wang, Molecules, 2017, 22,
266.
14 J. Luo, J. W. Wang, J. H. Zhang, S. Lai and D. C. Zhong,
CrystEngComm, 2018, 20, 5884–5898.
Conflicts of interest
There are no conicts to declare.
15 R. B. Lin, Y. He, P. Li, H. Wang, W. Zhou and B. Chen, Chem.
Soc. Rev., 2019, 48, 1362–1389.
16 I. Hisaki, C. Xin, K. Takahashi and T. Nakamura, Angew.
Chem., Int. Ed., 2019, 58, 11160–11170.
Acknowledgements
This work was supported by KAKENHI (JP18H01966,
JP19H04206, and JP21H01919) from MEXT and by Bilateral
Programs (JPJSBP120207401) from JSPS, Japan. I. H. thanks the
Izumi Science and Technology Foundation. N. M. is supported
by the Elements Strategy Initiative for Catalysts and Batteries
(No. JPMXP0112101003) and the Fugaku Supercomputer Project
(No. JPMXP1020200308) from the Ministry of Education,
Culture, Sports, Science, and Technology. A. D. acknowledges
the nancial support from MINECO through project MAT2017-
86532-R, JCCM through project SBPLY/19/180501/000212, and
UCLM (FEDER, proposal number: 2020-GRIN-28929). Y. S.
17 I. Hisaki, J. Inclusion Phenom. Macrocyclic Chem., 2020, 96,
215–231.
18 B. Wang, R.-B. Lin, Z. Zhang, S. Xiang and B. Chen, J. Am.
Chem. Soc., 2020, 142, 14399–14416.
19 Q. Yin, P. Zhao, R. J. Sa, G. C. Chen, L. Jian, T. F. Liu and
R. Cao, Angew. Chem., Int. Ed., 2018, 57, 7691–7696.
20 F. Hu, C. Liu, M. Wu, J. Pang, F. Jiang, D. Yuan and M. Hong,
Angew. Chem., Int. Ed., 2017, 56, 2101–2104.
21 B. Han, H. Wang, C. Wang, H. Wu, W. Zhou, B. Chen and
J. Jiang, J. Am. Chem. Soc., 2019, 141, 8737–8740.
22 P. Li, Y. He, H. D. Arman, R. Krishna, H. Wang, L. Weng and
B. Chen, Chem. Commun., 2014, 50, 13081–13084.
23 Y. He, S. Xiang and B. Chen, J. Am. Chem. Soc., 2011, 133,
14570–14573.
acknowledges
a Grant-in-Aid for JSPS Research Fellow
(20J20301). X-ray diffraction data, including preliminary data-
sets, were collected at BL40XU in SPring-8 with the approval of
JASRI (proposal no. 2018B1244, 2019A1161, and 2019B1134).
© 2021 The Author(s). Published by the Royal Society of Chemistry
Chem. Sci., 2021, 12, 9607–9618 | 9617

View Article Online
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24 P. Li, Z. Chen, M. R. Ryder, C. L. Stern, Q. H. Guo, X. Wang, 33 M. I. Hashim, H. T. M. Le, T. H. Chen, Y. S. Chen,
O. K. Farha and J. F. Stoddart, J. Am. Chem. Soc., 2019, 141,
12998–13002.
O. Daugulis, C. W. Hsu, A. J. Jacobson, W. Kaveevivitchai,
´
X. Liang, T. Makarenko, O. Miljanic, I. Popovs, H. V. Tran,
25 K. Kobayashi, T. Shirasaka, E. Horn and N. Furukawa,
Tetrahedron Lett., 2000, 41, 89–93.
X. Wang, C. H. Wu and J. I. Wu, J. Am. Chem. Soc., 2018,
140, 6014–6026.
26 P. Li, P. Li, M. R. Ryder, Z. Liu, C. L. Stern, O. K. Farha and 34 I. Hisaki, S. Nakagawa, N. Ikenaka, Y. Imamura, M. Katouda,
J. F. Stoddart, Angew. Chem., Int. Ed., 2019, 58, 1664–1669.
M. Tashiro, H. Tsuchida, T. Ogoshi, H. Sato, N. Tohnai and
27 X. Zhang, L. Li, J. X. Wang, H. M. Wen, R. Krishna, H. Wu,
M. Miyata, J. Am. Chem. Soc., 2016, 138, 6617–6628.
W. Zhou, Z. N. Chen, B. Li, G. Qian and B. Chen, J. Am. 35 I. Hisaki, Y. Suzuki, E. Gomez, Q. Ji, N. Tohnai, T. Nakamura
Chem. Soc., 2020, 142, 633–640. and A. Douhal, J. Am. Chem. Soc., 2019, 141, 2111–2121.
28 A. Pulido, L. Chen, T. Kaczorowski, D. Holden, M. A. Little, 36 I. Hisaki, N. Ikenaka, E. Gomez, B. Cohen, N. Tohnai and
S. Y. Chong, B. J. Slater, D. P. McMahon, B. Bonillo, A. Douhal, Chem.–Eur. J., 2017, 23, 11611–11619.
C. J. Stackhouse, A. Stephenson, C. M. Kane, R. Clowes, 37 I. Hisaki, Y. Suzuki, E. Gomez, B. Cohen, N. Tohnai and
T. Hasell, A. I. Cooper and G. M. Day, Nature, 2017, 543,
657–664.
A. Douhal, Angew. Chem., Int. Ed., 2018, 57, 12650–12655.
38 D. Z. Rogers, J. Org. Chem., 1986, 51, 3904–3905.
29 M. Mastalerz and I. M. Oppel, Angew. Chem., Int. Ed., 2012, 39 A. L. Spek, Acta Crystallogr., Sect. D: Biol. Crystallogr., 2009,
51, 5252–5255. 65, 148–155.
30 K. Ma, P. Li, J. H. Xin, Y. Chen, Z. Chen, S. Goswami, X. Liu, 40 C. Song, Y. He, B. Li, Y. Ling, H. Wang, Y. Feng, R. Krishna
S. Kato, H. Chen, X. Zhang, J. Bai, M. C. Wasson, and B. Chen, Chem. Commun., 2014, 50, 12105–12108.
R. R. Maldonado, R. Q. Snurr and O. K. Farha, Cell Rep. 41 T. Ikeda, T. Iijima, R. Sekiya, O. Takahashi and T. Haino, J.
Phys. Sci., 2020, 1, 100024. Org. Chem., 2016, 81, 6832–6837.
31 B. Wang, X. L. Lv, J. Lv, L. Ma, R. B. Lin, H. Cui, J. Zhang, 42 M. R. Nunzio, I. Hisaki and A. Douhal, J. Photochem.
Z. Zhang, S. Xiang and B. Chen, Chem. Commun., 2019, 56,
66–69.
32 T.-H. Chen, I. Popov, W. Kaveevivitchai, Y.-C. Chuang,
Photobiol. C: Photochem. Rev., 2021, 47, 100418.
43 E. Gomez, Y. Suzuki, I. Hisaki, M. Moreno and A. Douhal, J.
Mater. Chem. C, 2019, 7, 10818–10832.
ˇ
´
Y.-S. Chen, O. Daugulis, A. J. Jacobson and O. S. Miljanic,
Nat. Commun., 2014, 5, 5131.
9618 | Chem. Sci., 2021, 12, 9607–9618
© 2021 The Author(s). Published by the Royal Society of Chemistry