Fabrication of (4, 10) and (4, 12)-Connected Multifunctional Zirconium Metal-Organic Frameworks for the Targeted Adsorption of a Guest Molecule

Article abstract of DOI:10.1021/acs.inorgchem.9b02950

Following the principle of a topology guide, a zirconium MOF (PCN-207) based on the H₄TPTA ligand (tetramethyl(4,4′,4″,4?-(pyrazine-2,3,5,6-tetrayl))tetrabenzoic acid) with C₂ symmetry and an 8-connected Zr₆(μ_3-

Full text of DOI:10.1021/acs.inorgchem.9b02950

Article
pubs.acs.org/IC
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
Fabrication of (4, 10) and (4, 12)-Connected Multifunctional
Zirconium Metal−Organic Frameworks for the Targeted Adsorption
of a Guest Molecule
Liangliang Zhang,†,⊥ Bingbing Guo,‡,⊥ Huihui He,† Xiurong Zhang,‡ Yang Feng,‡ Weidong Fan,‡
Junlong Cao,† Guang Lu,§ Yanhui Chen,*,∥ Daofeng Sun,*,‡ and Wei Huang*,†
†MIIT Key Laboratory of Flexible Electronics (KLoFE), Shaanxi Key Laboratory of Flexible Electronics (KLoFE), Xi'an Key
Laboratory of Flexible Electronics (KLoFE), Xi'an Institute of Flexible Electronics, Institute of Flexible Electronics (IFE),
Northwestern Polytechnical University, Xi’an 710072, Shaanxi, China
‡School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, Shandong 266580, China
§School of Chemistry and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266510, China
∥Department of Applied Chemistry, School of Science, Northwestern Polytechnical University, Xi’an 710072, China
S
* Supporting Information
ABSTRACT: Following the principle of a topology guide, a
zirconium MOF (PCN-207) based on the H4TPTA ligand
(tetramethyl(4,4′,4″,4‴-(pyrazine-2,3,5,6-tetrayl))-
tetrabenzoic acid) with C2 symmetry and an 8-connected
Zr6(μ3‑OH)8(OH)8]8+ cluster with D4h symmetry has been
synthesized. PCN-206 can also be obtained by modulating the
benzoic acid usage to change the flexibility of the H4TPTA
ligand. The unique positions of 8-connected Zr6 clusters in
the flu and scu networks and the flexibility of the tetratopic
primary linker enable the precise insertion of fumarate (FA),
1,4-benzenedicarboxylic acid (H2BDC), and even 2,6-naph-
thalenedicarboxylic acid (H2NDC) in a one-pot reaction.
Auxiliary linkers are used to generate new MOF structures or topologies or to split the pore spaces, which may significantly
change the porosity and chemical and physical properties of scaffold MOFs. The results provide a successful strategy for the
rational design of multicomponent Zr-MOFs. Because of differences in composition and configuration between structures,
PCN-207 shows the highest separation capability of light hydrocarbons; moreover, PCN-206 exhibits the highest adsorption
capacity of 2,4-D and DCF among MOFs at present.
connected.19−21 Therefore, cluster flexibility makes topology
INTRODUCTION
■
predictions challenging for Zr-MOFs such as PCN-221-
As a kind of highly porous and ordered crystalline material,
225,22−26 MOF-801-841,21 MOF-525-545,27 and NU-1000-
metal organic frameworks (MOFs), linked by inorganic metal
1200.28−30 It should be noted that the introduction of flexible
ligands makes topology predictions more complex. It is a great
challenge to design and target the topologies of Zr-MOFs
when we take the linker complexity and cluster flexibility into
consideration at the same time. A recent report by Matzger has
discussed the effects of linker geometry and flexibility on the
formation of different Zr-tetratopic carboxylate MOFs.31 They
demonstrated that Zr-MOFs with csq topology can be targeted
by designing rectangularly shaped linkers with high aspect
ratios. However, the shapes and aspect ratios of linkers are
almost identical in csq- and scu-type frameworks. Very recently,
Zhou and co-worker reported how to control the structure of
ions/clusters and organic linkers,1−4 have proven potential
applications in the fields of gas adsorption and separation,5,6
light harvesting,7,8 and catalysis.9,10 In the past two decades,
the development of coordination chemistry has overcome the
drawbacks of traditional MOFs for practical applications, such
as thermal and chemical stability.11 According to the soft−hard
acid−base theory, organic carboxylate MOFs with a high
oxidation state ion or cluster show stronger coordination
stabilities than transition element- or rare earth element-based
MOFs.12−17 Since Lillerud reported the first zirconium MOF,
named UiO-66 with a [Zr6O4(OH)4(BDC)6] cluster, in
2008,18 more and more scientific interest has focused on Zr-
based MOFs because of their unparalleled thermal and
chemical stability.
Among all reported Zr-MOFs, the Zr6 cluster shows 6, 8,
Received: October 5, 2019
and 12 connections and in rare cases can be 9 and 10
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.9b02950
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Zr-tetracarboxylate frameworks through steric tuning and
studied their formation mechanism intensively.32
With regard to multicomponent and mixed-linker MOFs, it
is exceedingly difficult to control the structures and phase
purity of the products in a one-pot reaction as a result of the
increasing number of constituents and the appearance of
multiple phases. Zhou’s group recently developed a sequential
linker installation strategy to map the exact position of a linker
in a multicomponent MOF.33 Moreover, considering that
crystallization is an exclusionary rather than inclusionary
phenomenon, our group succeeded in sieving and functionaliz-
ing Zr-MOFs with targeted structures using auxiliary linkers in
a rigid ligand system by controlling the thermodynamic
processes.34
Because of the development of coordination chemistry and
reticular chemistry, the rational design and construction of
MOFs with intricate structural complexity have been
developed and have achieved great success. Thus, a pore
space partitions (PSP) strategy was applied in tuning host−
guest interactions.35 For example, it can significantly enhance
the framework stability and impact the gas sorption properties.
As a result, pore environments of parent MOFs can be
precisely controlled by introducing multiple components into
MOFs, which contributes to synergetic gas storage and
cooperative catalysis functions.
Figure 1. (a) Structure of H4TPTA. (b) 8-Connected Zr6 cluster in
PCN-207. (c) Dodecahedral cage in the framework of PCN-207. (d)
Augmented flu topology of PCN-207, where the purple and turquiose
polyhedra represent 4- and 8-connected nodes, respectively.
Herein, by modulating the thermodynamics using auxiliary
linkers, we synthesized PCN-207 and PCN-206 with (4, 8)-
connected flu and scu topology, and after incorporating linear
ligands, the structure of PCN-206 turned into a (4, 10)-
connected net and the structure of PCN-207 turned into a (4,
10)-connected zln topology and (4, 12)-connected PCN-208.
The introduction of auxiliary linkers can modulate the phase
purity on a wider 2D scale together with new structures and
topologies. A DFT calculation on the ligand energy barrier was
used to interpret the formation of a PCN series. Besides, the
adsorption and separation properties of PCN-206-208 before
and after incorporating linear ligands have been investigated
comparably, including the adsorption removal of pharmaceut-
ical waste from water and the adsorption and separation of
light hydrocarbons.
is different from the 109°28′ in an ideal tetrahedron (Figure
1b).
Moreover, in the structure of PCN-207, each [Zr6(μ3-
OH)8(OH)8]8+ SBU is surrounded by eight tetrahedral
TPTA4− ligands, and each TPTA4− links four [Zr6(μ3-
OH)8(OH)8]8+ SBUs. Thus, there is a kind of open
dodecahedral cage in the framework of PCN-207 with
dimensions of about 27.06 × 24.35 × 10.33 Å3, with three
hanging open windows in sizes of 12.73 × 13.59, 11.93 × 9.92,
and 14.9 × 6.65 Å2, respectively, consisting of eight TPTA4−
tetrahedra and six [Zr6(μ3-OH)8(OH)8]8+ SBUs as vertices
and 24 TPTA4− ligand edges (Figure 1c). These dodecahedral
cages are further connected into a 3D open framework by
sharing their rhombic facets. From the viewpoint of topology,
the [Zr6(μ3-OH)8(OH)8]8+ SBUs can be viewed as eight
connected nodes and tetrahedral TPTA4− ligands can be
regarded as four connected linkers. Hence, the tetrahedral
TPTA4− ligands link [Zr6(μ3-OH)8(OH)8]8+ SBUs to form a
(4, 8)-connected net with flu topology, which has been shown
in two reported rigid Zr-MOFs (PCN-52132 and MOF-84121)
based on similar inorganic [Zr6(μ3-OH)8(OH)8]8+ units
connected by organic ligands (Figure 1d).
Effect of Benzoic Acid in a One-Pot Reaction. As we all
know, the modulating linkers will affect the coordination of
linkers and/or clusters, which will impact the final structure
and the phase purity. For example, PCN-222 and PCN-224
can be sieved and purified to some degree by tuning the
concentration of benzoic acid. When we decrease the
concentration of BA from 1.85 to 1.1 M, a PCN-206 powder
is obtained. Powder X-ray diffraction analysis indicates that
PCN-206 crystallizes in orthogonal space group Cmmm and
contains 8-connected [Zr6(μ3-OH)8(OH)8]8+ clusters and 4-
connected TPTA4− ligands (Figure 2a). TPTA4− ligands adopt
a rectangular planar conformation with C2h symmetry, which is
different from tetrahedral in PCN-207. As shown in Figure 2b,
[Zr6(μ3-OH)8(OH)8]8+ clusters with D4h symmetry were
connected by TPTA4− ligands, which is similar to that of
PCN-207, creating a porous framework with rhombic channels
RESULTS AND DISCUSSION
■
Structure Description of PCN-207. The solvothermal
reaction of H4TPTA with zirconium tetrachloride and benzoic
acid in DMF at 120 °C for 24 h led to the formation of
colorless octahedral single crystals of PCN-207. X-ray single-
crystal diffraction indicates that PCN-207 crystallizes in
orthogonal space group Fmmm and contains 8-connected
[Zr6(μ3-OH)8(OH)8]8+ clusters connected by tetrahedral
TPTA ligands (Figure 1a). All of the triangular faces in each
[Zr6(μ3-OH)8(OH)8]8+ cluster are capped with μ3-OH groups.
Only eight edges are linked by carboxylates from tetrahedral
TPTA4− ligands, which is different from that of the UiO series,
and the remaining coordination sites are terminal −OH/H2O
groups. To satisfy the demands of symmetry, both Zr6(μ3-
OH)8(OH)8]8+ clusters and tetrahedral TPTA4− ligands suffer
a symmetry reduction. The symmetry of [Zr6(μ3-
OH)8(OH)8]8+ clusters in PCN-207 has changed from Oh to
D4h, which has been reported in PCN-222,23 PCN-521,32 and
MOF-545.27 At the same time, the symmetry of the tetrahedral
TPTA ligands is also reduced to the lowest C2 with the angles
of two adjacent phenyl rings at about 66.05 and 115.12°, which
B
DOI: 10.1021/acs.inorgchem.9b02950
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
reaction, such as with fumarate (FA), 1,4-benzenedicarboxylic
acid (H2BDC), and 2,6-naphthalenedicarboxylic acid
(H2NDC). Considering the similar length between second
modulating linkers and two adjacent Zr6 clusters, the one-pot
method was applied. Fortunately, FA can be accommodated
into PCN-206, and H2BDC and H2NDC ligands are installed
into the pocket of PCN-207. PCN-207 exhibits excellent
spongelike behavior, which contributes to the flexible of
H4TPTA ligands on the a axis. The resulting compounds,
designated as PCN-206-FA, PCN-207-BDC, and PCN-207-
NDC, maintain adequate crystallinity following guest encap-
sulation and are subsequently analyzed by single-crystal X-ray
diffraction and PXRD. The existence and positions of BDC
and NDC are unambiguously observed in the crystallo-
graphically resolved structure (Figure 3).
As for PCN-207-BDC and PCN-207-NDC, both of them
crystallize in the Fmmm space group. Interestingly, the unit
cells of PCN-207-BDC and PCN-207-NDC gradual changed
in size compared to the prototype MOF (PCN-207). A
significant increase in the length of the a axis (from 14.1 to
16.5 Å) and a slight decrease in the length of the b/c axis were
observed upon linker inclusion. Tetrahedral TPTA4− ligands
also adopt the lowest D2 symmetry, with the angles of two
adjacent phenyl rings being about 67.48 and 114.39° for PCN-
207-BDC and 35.89 and 53.73° for PCN-207-NDC. With
regard to PCN-206-FA, it also adopts the Cmmm space group.
There is no obvious change between PCN-206 and PCN-206-
FA in the unit cell parameter because of the perfect match in
length between the pockets and FA linkers. The crystallo-
graphic data for PCN-206, PCN-206-FA, PCN-207, and PCN-
207-BDC are summarized in Table S1. Take PCN-207-BDC as
an example: each Zr6 cluster is 10-connected to 8 TPTA4− and
2 BDC linkers. It is very interesting that the dodecahedral cage
observed in the framework of PCN-207 was divided into two
half-dodecahedral cages. The topology of PCN-206-FA, PCN-
Figure 2. (a) Structure of H4TPTA. (b) 8-Connected Zr6 cluster in
PCN-206. (c) Dodecahedral cage in the framework of PCN-206. (d)
Augmented scu topology of PCN-206, where the purple and turquiose
polyhedra represent 4- and 8-connected nodes, respectively.
that are approximately 15.2373 × 26.775 Å2 in diameter in the
c axis (Figure 2c). The walls of the rhombic channel are
composed of two channels with diameters of 14.44 × 11.35
and 14.32 × 8.4 Å2 in an axis. Therefore, PCN-206 adopts a (4,
8)-connected network with scu topology (Figure 2d).
Effect of Second Modulating Linkers in a One-Pot
Reaction. A careful inspection of the structure of PCN-206
and PCN-207 shows that each cluster is connected by eight
carboxylate groups with the remaining four coordination sites
occupied by aqua ligands. Two of them are in the equatorial
plane, and the distance between two adjacent Zr6 clusters is 5.0
and 6.262 Å, which can accommodate a linear dicarboxylate
linker by replacing the terminal OH−/H2O via an acid−base
Figure 3. Structures of different MOF pairs with pockets to selectively accommodate different auxiliary linkers: PCN-206 for FA, PCN-207 for
BDC, and PCN-208 for NDC.
C
DOI: 10.1021/acs.inorgchem.9b02950
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 4. Topologies for (a) PCN-206-FA, (b) PCN-207-NDC, and (c) PCN-208-NDC.
Figure 5. Synthesis map showing the effect of auxiliary linkers. (a) PCN-206 and PCN-207 modulated by FA and (b) PCN-206, PCN-207, and
PCN-208 modulated by NDC.
207-BDC, and PCN-207-NDC changed from a (4, 8)-
connected net to a (4, 10)-connected net.
ligand, which are 6.64 × 8.16 and 10.49 × 8.16 Å2, respectively.
Thus, H NMR digestion experiments of digested PCN-206-
1
What is more interesting is that PCN-208-NDC can be
obtained by incorporating more H2NDC linkers. It should be
pointed out that PCN-208 could not be accessed directly
under the present experimental conditions. The connected
numbers of the PCN-207 and PCN-208 series vary from
unsaturated (4, 8)- and (4, 10)- to saturated (4, 12)-connected
after increasing the concentration of linear ligands gradually
(Figure 4). Compared with the rotation of benzene rings in
PCN-206 by 61.07° in the opposite direction, the benzene
rings of PCN-208-NDC rotate 49.95° in the same direction,
thus forming the new topological configurations. In PCN-208-
NDC, each [Zr6(μ3-O)4(μ3-OH)4]12+ linked eight TPTA4−
and four NDC, and each TPTA4− is connected to four clusters
to form (4,12)-c. The 8.17 × 16.38 Å2 quadrilateral tunnels are
divided into two different triangular tunnels by the NDC
FA, PCN-207-BDC, PCN-207-NDC, and PCN-208-NDC
certify the different linker ratios in the synthesized MOFs,
and they are formulated as [Zr6(μ3-O)4(μ3-OH)4]-
[(OH)2(H2O)2]TPTA2FA (PCN-206-FA), [Zr6(μ3-O)4(μ3-
OH)4][(OH)2.6(H2O)2.6]TPTA2NDC0.7 (PCN-207-NDC),
and [Zr6(μ3-O)4(μ3-OH)4][(OH)1.2(H2O)1.2]TPTA2NDC1.4
(PCN-208-NDC). Generally, the auxiliary linker contents in
MOFs gradually escalate as their ratios in the starting materials
increase, suggesting the partial occupation of auxiliary linkers.
Inspired by the success of Yaghi’s group on multivariate
MOFs, we also tried to use N3-BDC, NH2-BDC, OH-BDC,
SO3Na-BDC, NO2-BDC, and 2,5-(OH)2-BDC linkers to
exchange the H2BDC ligand in PCN-207-BDC in one-pot
and linker exchange reactions,36 but we failed to get any of
them. There are mainly three reasons for this. First, because of
D
DOI: 10.1021/acs.inorgchem.9b02950
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
the steric hindrance between the pore and organic ligands, the
pockets of PCN-207-BDC are not compatible for the BDC
ligands with different functional groups. Second, the linker
basicity (pKa) may be not suitable for substitution. Third,
H2BDC ligands resist exchange, which indicates the stronger
coordination capability between carboxylate and Zr6 clusters.
Synthesis Map Analysis in a One-Pot Reaction. Huge
filtered experiments were carried out to systematically
investigate the effect of second modulating linkers by fixing
the concentration of benzoic acid and altering the linker ratios
of the starting materials (Table S2). The effects of the linker
ratio and modulating reagent are summarized in the synthesis
map (Figure 5). PCN-206 can be obtained under a wide range
of synthesis conditions by adding FA (Figure 5a). The use of
BDC and NDC will promote the formation of PCN-207-BDC,
PCN-207-NDC, and PCN-208-NDC, respectively. However,
PCN-207 has one pocket to fit NDC and PCN-208 has two
pockets per Zr6 cluster. Therefore, the formation of PCN-207-
NDC and PCN-208-NDC can be dictated by the amount of
NDC added (Figure 5b). To form pure-phase PCN-207-NDC,
the NDC concentration can be as high as 16 M to avoid the
formation of PCN-208. Further increasing the NDC
concentration favors the formation of PCN-208, which has
more NDC in its structure. These phenomena are in line with
Le Chatelier’s principle. Normally, DUT-53 is thus formed if a
large excess of NDC is added because of the potential
competition between the primary linker and the auxiliary
linker, but this situation can be avoided to a great extent
because the tetratopic linkers are more competitive than the
ditopic auxiliary linker.20
DFT Calculation of the Ligand Energy Barrier. To
investigate the relationship between energy and structure,
density functional theory (DFT) calculations were performed
on the basis of M06-2X-D3/6-311G(d) using the Gaussian 09
D.01 software package.37 We calculated the single-point energy
of each linker in the three compounds. Because all of the
linkers in PCN-206, PCN-207, and simulated PCN-208 share
the same composition and similar (4,8)-connected Zr6 clusters,
the energy difference between each set of linkers is attributed
to the structural differences. For comparison, all of the energy
is normalized by subtracting the energy value of PCN-207. The
relative energies of PCN-206 and PCN-208 are +32.197 and
+56.839 kcal/mol, so the stable order of linkers is PCN-207 >
PCN-206 > PCN-208, which matches very well with the
experimental findings (Figure S2).
The permanent porosity of the PCN-206, -207, and -208
series has been confirmed with the as-synthesized sample by
nitrogen sorption experiments at 77 K (Figure 6). PCN-206
and PCN-207 exhibit a type-I isotherm of N2 sorption at 77 K
and 1 bar, implying the existence of micropores in their
structures. The N2 uptake of PCN-207 is a little larger than
that of PCN-206, and the Brunauer−Emmett−Teller (BET)
surface areas of PCN-206 and PCN-207 are 1156 and 1241 m2
g−1, respectively. Nitrogen physisorption experiments on PCN-
206-FA, PCN-207-BDC, PCN-207-NDC, and PCN-208-NDC
at 77 K and 1 bar also revealed type-I isotherms with a
maximum nitrogen uptake of 433 cm3 g−1 for PCN-206-FA,
354 cm3 g−1 for PCN-207-BDC, 323 cm3 g−1 for PCN-207-
NDC, and 309 cm3 g−1 for PCN-208-NDC. The BET surface
areas of PCN-206-FA, PCN-207-BDC, PCN-207-NDC, and
PCN-208-NDC are 1428, 1194, 1107, and 1068 m2 g−1,
respectively, which is in good agreement with the single-crystal
X-ray diffraction data. The permanent porosity is well
Figure 6. N2 sorption isotherms of PCN-206-208 systems at 77 K and
1 bar.
maintained before and after inserting the second linkers. The
decrease in the BET surface areas of PCN-207-BDC, PCN-
207-NDC, and PCN-208-NDC is a result of their occupation
of the free space inside the MOF cavity. Surprisingly, the
increase in the BET surface area of PCN-206-FA may
contribute to the structurally rigid enhancement. To our
delight, the pockets of PCN-207 and PCN-208 can be divided
into two pieces. The insertion of FA, BDC, and NDC will
affect the properties of PCN-207 and PCN-208 significantly,
such as the changes in the pore environment, Lewis acid sites,
the flexiblity and rigidity of the framework, the pore size
distribution, and the thermal and chemical stabilities.
Thermal and Chemical Stability Analyses. To inves-
tigate the differences in the PCN-206-208 series, thermogravi-
metric analyses were performed to assess their thermal
stability. As shown in Figure S3, PCN-206-208 is stable up
to 400 °C and shows excellent thermal stability toward heat.
Thus, the inset of the second linkers did not improve the
thermal stability significantly, which also indicates the stability
of the parent MOF. Take PCN-206-FA as an example. The
inset of FA brings about an enrichment in rigidity but shows a
small enhancement in thermal stability compared to that of
PCN-206. It may contribute to the similar sizes between the
pockets and FA linkers, melting point, and linker contents. A
similar situation can be found in PCN-207-BDC. However,
PCN-208-NDC has weak thermal stability, which is attributed
to the ligand energy barrier. It also certifies that the energy
value of PCN-207 is the lowest. We note that the influencing
factors of the energy level of the ligand in the crystal cannot be
evaluated solely by the distortion of linkers. It is possible that
the insertion of the ancillary ligand affects the energy of the
ligand, but from the results of the test, the insertion of the
ancillary ligands slightly increases the stability of the
corresponding series but does not cause large differences
among the different series.
The chemical stabilities were first qualitatively analyzed by
their PXRD patterns after treatment in acidic (pH 2), neutral
(pH 7), and basic (pH 10 and 12) environments for 24 h
(Figure S4). According to the results of PXRD, all of the
samples had excellent crystallinity after treatment with acid and
base, indicative of their superb chemical stabilities. Further-
more, take PCN-206-FA and PCN-207-BDC as examples.
Their chemical stabilities are measured via quantified digestion
E
DOI: 10.1021/acs.inorgchem.9b02950
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 7. (a−c) Comparison of the adsorption effect at different pH values and (d−f) adsorption kinetics curves. PCN-206 (black), PCN-206-FA
(red), PCN-207 (green), PCN-207-BDC (magenta), and PCN-208-NDC (navy).
analysis because of the high tolerance of defects in Zr-MOFs.
Together with the results of H NMR and PXRD, despite the
partial or complete dissociation of FA and BDC ligands in
acidic and basic environments, the resultant MOFs retain
intact frameworks without a loss of crystallinity (Figures S5−
S12).
Removal of Pharmaceutical Wastewater. The excellent
thermal and chemical stabilities prompt us to investigate their
practical applications. Covering drugs, cosmetics, and toiletries,
these are collectively referred as pharmaceuticals and personal
care products (PPCPs). Today’s waste disposal is a more and
more difficult task, especially for the treatment and utilization
of water resources. These PPCPs have already pose a serious
threat to water quality. However, the adsorption removal
efficiency of conventional adsorbents, such as activated carbon,
activated alumina and clay minerals, is usually very low.38,39
Therefore, the efficient and selective removal of PPCPs from
wastewater is extremely important and challenging.
In this work, the PCN-206, -207, -208 series was employed
as PPCPs adsorbents to study the effect of different structural
environments of MOF on PPCPs adsorption, explore their
adsorption kinetics and structural function relationships, and
provide a reference value for designing more efficient PPCP
adsorbents. 2,4-Dichlorophenoxyacetic acid (2,4-D), clofibric
acid (CLA), and diclofenac sodium (DCF) are three typical
PPCPs40−42 with water solubility that are often involved in life
and are used as adsorption objects: 2,4-D with a molecular size
of 10 × 5.6 × 1.8 Å3 is listed by the international agency for
research on cancer because of its toxicity and mutagenicity.
CLA is a widely used herbicide with a molecular size of 10 ×
5.0 × 4.3 Å3. DCF is one of the nonsteroidal anti-inflammatory
drugs, and its molecular size is 9.3 × 7.4 × 1.8 Å3.
1
The excellent acid−base water stability of the PCN-206-208
series is necessary for the application of wastewater treatment.
In view of this, the effect of water pH on adsorption was first
explored. We placed 3 mg of Zr-MOF in 10 mL of a PPCP
F
DOI: 10.1021/acs.inorgchem.9b02950
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
aqueous solution with different pH values (pH 3, 5, 6 7, 9).
Note that DCF is difficult to accommodate in solution with pH
< 5 (PPCP concentration, 100 mg/L 2,4-D; 50 mg/L CLA and
DCF, respectively). UV−vis spectroscopy was used to record
changes in PPCP solution concentration (Figures S13−S18).
PCN-206 and PCN-206-FA show good adsorption capacity for
2,4-D and DCF, and PCN-206-208 displays low adsorption to
CLA. Nitrogen adsorption tests showed that PPCPs entered
the pores of the MOF (Figure S19). For example, after PCN-
206 adsorbs 2,4-D, DCF, and CLA, its N2 adsorption decreases
from 337.23 to 99.37, 81.61, and 272.89 cm3/g, respectively,
and BET decreases from 1156 to 301.26, 289.57, and 642.35
m2/g, respectively. SEM images show that MOFs have no
distinct changes in morphological after the adsorption of
PPCPs (Figure S20). PXRD diffraction shows that the crystals
maintain good crystallinity after the adsorption of PPCPs
(Figure S21). PPCP adsorption results indicate that the pH
value of the solution has little effect on the adsorption of
PPCPs by MOFs (Figure 7a−c), which makes it more
accessible and practical under the harsh conditions of
wastewater. The adsorption capacity for 2,4-D and DCF with
similar trends in loading amount is the following: PCN-206 >
PCN-206-FA > PCN-208 > PCN-207 > PCN-207-BDC. The
reasons for the different capture capabilities of the PCN-206-
208 series may be as follows. First, the porosity of MOF is a
prerequisite for the capture of macromolecular objects.
Because the PCN-207 series belong to the flu configuration,
the twist of the ligand forms the cage configuration, and the
theoretical size of the open window (∼10 × 12 Å2) is similar to
the three molecular sizes and even smaller in some directions
(∼6 × 14 Å2). Therefore, PPCP cannot enter the oblate hole
of PCN-207 to achieve capture. When BDC is inserted into
PCN-207 to divide the cage, it is more difficult to achieve
macromolecular capture. In PCN-208-NDC, the channels in
PCN-208-NDC are also relatively small with 7.67 × 8.16 Å2
and 10.49 × 8.16 Å2 diameters, respectively, but it is beneficial
to the entry of molecules compared to the cage structure. In
contrast, the PCN-206 series possess unobstructed channels
with 15.24 × 26.78 Å2 diameters in scu topology, and PPCP
molecules are easier to access. On the other hand, we propose
that the adsorption site of PPCP with MOF is −COOH, and
the two adjacent methyl groups in CLA reduce the binding
ability of CLA to MOF, resulting in the inability of MOF to
capture CLA. The nitrogen atom in MOF is more likely to
touch the binding −COOH site, interacting with carboxyl
groups to capture PPCP. Furthermore, near-plane 2,4-D and
DCF easily interact with the flat ligand on the PCN-206
channel walls. The above factors lead to the result that the
adsorption capacity of the PCN-206 series for 2,4-D and DCF
is much higher than for other series.
of three different PPCP molecules were calculated by using eq
1 to plot the reticle (t/qt versus t) (Figure S22, Table S4). The
larger the k2 value, the faster the MOF adsorbs PPCP
molecules. As shown in Table S4, for 2,4-D, the k2 value
follows the order PCN-207 ≈ PCN-207-BDC > PCN-206 >
PCN-208-NDC > PCN-206-FA, and the trends in the
calculated k2 values of PPCPs@Zr-MOF composites are
consistent with the experimental adsorption data. When the
adsorption capacity is extremely small, the adsorption quickly
reaches equilibrium, and when the adsorbed amount increases,
the adsorption speed is also affected, which requires a relatively
long time.
The study of adsorption kinetics and the initial adsorption
capacity show that 2,4-D and DCF may be captured by MOFs
in large quantities. We then further evaluated the adsorption
capacity of different MOFs toward 2,4-D and DCF. MOFs of
0.30 mg/mL were added to a series of concentrations (ranging
from 20 to 300 mg/L) of PPCPs, and then we used the
Langmuir model to evaluate the MOFs’ affinities for guest
molecules. The Langmuir isotherm equation is given as
ce
qe
ce
qmax
1
=
+
qmaxb
(2)
q
max is the theoretical maximum adsorption capacity (mg/g), ce
is the saturation/equilibrium concentration of PPCP in the
supernatant (mg/L), and b is the Langmuir constant (related
to the adsorption strength or affinity, L/mg).
The qmax values were then calculated and summarized
ce
qe
according to the adsorption isotherms
(2) of Zr-MOF@
PPCPs in Figure S23 and are shown in Figure S24 and Table
S5. We found that the PCN-206 series has obvious capture
advantages for 2,4-D and DCF. The order of maximum
adsorption capacity of 2,4-D/DCF is PCN-206 > PCN-206-FA
> PCN-208-NDC > PCN-207 > PCN-207-BDC, and
Langmuir constants are also in this order. PCN-206 has the
largest adsorption capacity (470 mg/g for 2,4-D@PCN-206,
490 mg/g for DCF@PCN-206) and Langmuir constant (41.7
for 2,4-D@PCN-206, 76.3 for DCF@PCN-206). Because of
the flat scu topology of PCN-206, it is more conducive to the
entry of PPCP. PCN-206 and PCN-206-FA have capture
capacities of 470 and 450 mg/g for 2,4-D and 490 and 210
mg/g for DCF, respectively. Regardless of the PCN-206-FA’s
ability to capture DCF, the adsorption capacity of PCN-206
for 2,4-D and DCF is currently the largest in the open
literature. In addition, the insertion of FA slightly reduces the
adsorption of 2,4-D, but limits the amount of DCF adsorption
to half. Because the carbon−carbon double bond in FA has a
high electron cloud density, it is mutually exclusive with
−COO− in DCF, inhibiting the entry of DCF. Compared to
the traditional adsorbent activated carbon, the adsorption
capacity is much greater and double that of other MOFs as
well.26 In contrast, the PCN-207 series has an adsorption
capacity of only about 50 mg/g and PCN-208-NDC has
capacities of 160 and 120 mg/g for 2,4-D and DCF,
respectively. It can be seen that the distortion of the structure
will cause the difference in the ability to adsorb guest
molecules.
The adsorption kinetics of three PPCP molecules were
simulated using pseudo-second-order kinetics with this model
(r > 0.996) as follows:
t
qt
1
k2qe
1
qe
=
+
t
2
(1)
qe is the maximum adsorption amount of PPCPs at adsorption
equilibrium (mg/g), qt is the amount of adsorption at time t
(h), and k2 is the pseudo-second-order rate constant (g mg−1
h−1).
Subsequently, on the basis of the experimental data (Figure
7d−f), the pseudo-second-order kinetic parameters (k2 values)
Adsorption and Separation of Light Hydrocarbons.
Finally, we further tested the potential utility of the PCN-206,
-207, and -208 series in gas storage and separation by
evaluating single-component gas sorption isotherms for various
light hydrocarbons (CH4, C2H2, C2H4, C2H6, and C3H6) at
G
DOI: 10.1021/acs.inorgchem.9b02950
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 8. Sorption isotherms of hydrocarbons for desolvated (a) PCN-206, (b) PCN-206-FA, (c) PCN-207, (d) PCN-207-BDC, and (e) PCN-
208-NDC at 273 K. (f−j) Selectivities are predicted by IAST for C2/C1 and C3/C1 (0.5:0.5) gas mixtures at 273 K, respectively.
273 and 298 K and 1 bar. It should be pointed out that the
PCN-206 series exhibits a better performance compared to
those of PCN-207, PCN-207-BDC, and PCN-208-NDC. The
adsorption capacities of PCN-206 for CH4 (12.6 cm3
g−1),C2H2 (104.7 cm3 g−1), C2H4 (86.9 cm3 g−1), C2H6
(98.7 cm3 g−1), and C3H6 (115.2 cm3 g−1) are comparable
to those of UTSA-35a and UTSA-36a at 298 K and 1 bar
(Figure 8). The reason may come from the suitable pore size
H
DOI: 10.1021/acs.inorgchem.9b02950
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
distribution regulated with the scu topology and the affinity of
the pore surface for adsorbents. Thus, PCN-206 exhibits the
best performance for light hydrocarbon storage. More
interestingly, the CH4 adsorption amounts are much less
than those of C2 and C3 hydrocarbons under the same
conditions.
Experimental procedures, single-crystal X-ray crystallog-
raphy analysis, N2 sorption isotherms, and supplemen-
tary figures and tables (PDF)
Accession Codes
CCDC 1811246, 1965804, and 1879626 contain the
supplementary crystallographic data for this article. These
data can be obtained free of charge via www.ccdc.cam.ac.uk/
data_request/cif, or by emailing data_request@ccdc.cam.ac.
uk, or by contacting The Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44
1223 336033.
The PCN-206, -207, and -208 series are saturated with C3
hydrocarbons at lower pressures, and the slopes of adsorption
isotherms are much steeper than that of CH4, indicating the
stronger affinity between higher hydrocarbons and the pore
surfaces. Such great differences in adsorption amounts and the
interactions between higher hydrocarbons and CH4 indicate
that the PCN-206, -207, and -208 series may realize highly
selective separations of CH4 from C3 hydrocarbons. IAST is
used to predict the selectivity of binary mixtures of C2 or C3
hydrocarbons with CH4 (molar ratio 50:50) at 298 or 273 K,
respectively (Figure 8, Figures S25 and S26). Among them,
PCN-207-BDC showed relatively high selectivities of 20.13,
27.46, 32.51, and 244.0 for C2H2/CH4, C2H4/CH4, C2H6/
CH4, C3H4/CH4, and C3H6/CH4 at 298 K (Figure S25). With
the decrease in temperature, the selectivities of C2H2/CH4,
C2H4/CH4, C2H6/CH4, C3H4/CH4, C3H6/CH4 (0.5:0.5)
increased significantly to appreciable values of 76.71, 43.17,
92.07, and 1575.36 at 273 K. The selectivity of C3H6/CH4 is
higher than the corresponding values of MOFs. Moreover, the
adsorption enthalpies of PCN-207 and PCN-207-BDC are also
higher than those of the other PCN-206 and -208 series
(Figure S27). For example, the adsorption enthalpy of C3H6 of
PCN-207-BDC can reach 60 kJ/mol, which is much higher
than the 19 kJ/mol for PCN-206. This may be due to the cage
of 207-BDC being more conducive to the selection and
screening of gas molecules. The introduction of BDC increases
the rigidity of the crystals. At the same time, the insertion of
the BDC increases the selection selectivity ratio of C3H6/CH4
from 244 to 1575, and there is a certain increase in the
adsorption enthalpy of C3H6 and a decrease in the same
parameter for CH4.
AUTHOR INFORMATION
■
Corresponding Authors
*E-mail: yanhuichen@nwpu.edu.cn (Y.C.).
*E-mail: dfsun@upc.edu.cn (D.S.).
*E-mail: provost@nwpu.edu.cn (W.H.).
ORCID
Liangliang Zhang: 0000-0002-5091-018X
Yanhui Chen: 0000-0001-6511-1738
Author Contributions
⊥These authors contributed equally.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the National Natural Science
Foundation of China (NSFC 21875285, 21978240, 21676217
and 21701187), Key Research and Development Projects of
Shandong Province (2019JZZY010331), and the Fundamental
Research Funds for the Central Universities
(31020180QD115). L.Z. also thanks Chiming Wang from
the University of Science and Technology Beijing for help with
DFT simulations.
REFERENCES
■
CONCLUSIONS
■
(1) Furukawa, H.; Cordova, K. E.; O’Keeffe, M.; Yaghi, O. M. The
Chemistry and Applications of Metal-Organic Frameworks. Science
2013, 341, 1230444−1230444.
(2) Kalmutzki, M. J.; Hanikel, N.; Yaghi, O. M. Secondary building
units as the turning point in the development of the reticular
chemistry of MOFs. Sci. adv. 2018, 4, eaat9180.
(3) Zhou, H.-C. “J.”; Kitagawa, S. Metal−Organic Frameworks
(MOFs). Chem. Soc. Rev. 2014, 43, 5415−5418.
(4) Zhou, H. C.; Long, J. R.; Yaghi, O. M. Introduction to metal-
organic frameworks. Chem. Rev. 2012, 112, 673−674.
(5) Li, J. R.; Sculley, J.; Zhou, H. C. Metal-organic frameworks for
separations. Chem. Rev. 2012, 112, 869−932.
We have successfully fabricated and characterized a series of
stable Zr-MOFs with different topology with H4TPTA and
have calculated and explored the factors that affect different
aspects of crystal design synthesis. The flexibility of the ligand
leads to the variability of the distance and the distortion of the
skeleton, the suitable distance and unsaturated Zr6 cluster, and
the amount of modulating agent. The type and dosage of the
second modulating linkers can affect the formation of different
configurations. The PCN--206, -207, and -208 series show
permanent porosity and excellent thermal and chemical
stabilities. Because of the differences in structure, PCN-206
has the highest adsorption capability of light hydrocarbons;
moreover, PCN-206 exhibits ultrahigh 2,4-D and DCF
adsorption capacities. The PCN-207 series exhibits a superior
C3H6 adsorption enthalpy and C3H6/CH4 selectivity over
those of the other two series, meaning that this type of
structural design has a potential C3H6 adsorption capacity.
(6) Fan, W.; Wang, Y.; Zhang, Q.; Kirchon, A.; Xiao, Z.; Zhang, L.;
Dai, F.; Wang, R.; Sun, D. An Amino-Functionalized Metal-Organic
Framework, Based on a Rare Ba12(COO)18(NO3)2 Cluster, for
Efficient C3/C2/C1 Separation and Preferential Catalytic Perform-
ance. Chem. - Eur. J. 2018, 24, 2137−143.
(7) Hu, Z.; Deibert, B. J.; Li, J. Luminescent metal−organic
frameworks for chemical sensing and explosive detection. Chem. Soc.
Rev. 2014, 43, 5815−5840.
(8) Zhang, L.; Kang, Z.; Xin, X.; Sun, D. Metal−organic frameworks
based luminescent materials for nitroaromatics sensing. CrystEng-
Comm 2016, 18, 193−206.
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.inorgchem.9b02950.
(9) Zhang, T.; Lin, W. Metal−organic frameworks for artificial
photosynthesis and photocatalysis. Chem. Soc. Rev. 2014, 43, 5982−
5993.
I
DOI: 10.1021/acs.inorgchem.9b02950
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(10) Jiao, L.; Wang, Y.; Jiang, H.-L.; Xu, Q. Metal-Organic
Frameworks as Platforms for Catalytic Applications. Adv. Mater.
2018, 30, 1703663.
(11) Howarth, A. J.; Liu, Y.; Li, P.; Li, Z.; Wang, T. C.; Hupp, J. T.;
Farha, O. K. Chemical, thermal and mechanical stabilities of metal−
organic frameworks. Nat. Rev. Mater. 2016, 1, 15018.
(12) Tan, Y.-X.; Yang, X.; Li, B.-B.; Yuan, D. Rational design of a flu-
type heterometallic cluster-based Zr-MOF. Chem. Commun. 2016, 52,
13671−13674.
Structure, and Metalation of Two New Highly Porous Zirconium
Metal−Organic Frameworks. Inorg. Chem. 2012, 51, 6443−6445.
(28) Deria, P.; Mondloch, J. E.; Tylianakis, E.; Ghosh, P.; Bury, W.;
Snurr, R. Q.; Hupp, J. T.; Farha, O. K. Perfluoroalkane
functionalization of NU-1000 via solvent-assisted ligand incorpo-
ration: synthesis and CO2 adsorption studies. J. Am. Chem. Soc. 2013,
135, 16801−16804.
(29) Gutov, O. V.; Bury, W.; Gomez-Gualdron, D. A.;
Krungleviciute, V.; Fairen-Jimenez, D.; Mondloch, J. E.; Sarjeant, A.
A.; Al-Juaid, S. S.; Snurr, R. Q.; Hupp, J. T.; Yildirim, T.; Farha, O. K.
Water-stable zirconium-based metal-organic framework material with
high-surface area and gas-storage capacities. Chem. - Eur. J. 2014, 20,
12389−12393.
(30) Liu, T. F.; Vermeulen, N. A.; Howarth, A. J.; Li, P.; Sarjeant, A.
A.; Hupp, J. T.; Farha, O. k. Adding to the Arsenal of Zirconium-
Based Metal−Organic Frameworks. Eur. J. Inorg. Chem. 2016, 2016,
4349−4352.
(31) Ma, J.; Tran, L. D.; Matzger, A. J. Toward Topology Prediction
in Zr-Based Microporous Coordination Polymers: The Role of Linker
Geometry and Flexibility. Cryst. Growth Des. 2016, 16, 4148−4153.
(32) Zhang, M.; Chen, Y. P.; Bosch, M.; Gentle, T., 3rd; Wang, K.;
Feng, D.; Wang, Z. U.; Zhou, H. C. Symmetry-guided synthesis of
highly porous metal-organic frameworks with fluorite topology.
Angew. Chem., Int. Ed. 2014, 53, 815−818.
(33) Yuan, S.; Chen, Y. P.; Qin, J. S.; Lu, W.; Zou, L.; Zhang, Q.;
Wang, X.; Sun, X.; Zhou, H. C. Linker Installation: Engineering Pore
Environment with Precisely Placed Functionalities in Zirconium
MOFs. J. Am. Chem. Soc. 2016, 138, 8912−8919.
(34) Zhang, L.; Yuan, S.; Fan, W.; Pang, J.; Li, F.; Guo, B.; Zhang,
P.; Sun, D.; Zhou, H.-C. Cooperative Sieving and Functionalization of
Zr Metal−Organic Frameworks through Insertion and Post-
Modification of Auxiliary Linkers. ACS Appl. Mater. Interfaces 2019,
11, 22390−22397.
(35) Zhai, Q.-G.; Bu, X.; Zhao, X.; Li, D.-S.; Feng, P. Pore Space
Partition in Metal−Organic Frameworks. Acc. Chem. Res. 2017, 50,
407−417.
(13) Guo, B.; Li, F.; Wang, C.; Zhang, L.; Sun, D. A rare (3,12)-
connected zirconium metal−organic framework with efficient iodine
adsorption capacity and pH sensing. J. Mater. Chem. A 2019, 7,
13173−13179.
(14) Kalidindi, S. B.; Nayak, S.; Briggs, M. E.; Jansat, S.; Katsoulidis,
̀
A. P.; Miller, G. J.; Warren, J. E.; Antypov, D.; Cora, F.; Slater, B.;
Prestly, M. R.; Martí-Gastaldo, C.; Rosseinsky, M. J. Chemical and
Structural Stability of Zirconium-based Metal-Organic Frameworks
with Large Three-Dimensional Pores by Linker Engineering. Angew.
Chem., Int. Ed. 2015, 54, 221−226.
(15) Wang, Y.; Feng, L.; Fan, W.; Wang, K.; Wang, X.; Wang, X.;
Zhang, K.; Zhang, X.; Dai, F.; Sun, D.; Zhou, H. Topology
Exploration in Highly Connected Rare-Earth Metal−Organic Frame-
works via Continuous Hindrance Control. J. Am. Chem. Soc. 2019,
141, 6967−6975.
(16) Feng, L.; Wang, K.; Day, G.; Zhou, H. The chemistry of multi-
component and hierarchical framework compounds. Chem. Soc. Rev.
2019, 48, 4823−4853.
(17) Jin, F.; Zhao, C.; Ma, H.; Chen, G.; Dong, Y. Homochiral
BINAPDA-Zr-MOF for Heterogeneous Asymmetric Cyanosilylation
of Aldehydes. Inorg. Chem. 2019, 58, 9253−9259.
(18) Cavka, J. H.; Jakobsen, S.; Olsbye, U.; Guillou, N.; Lamberti,
C.; Bordiga, S.; Lillerud, K. P. A New Zirconium Inorganic Building
Brick Forming Metal Organic Frameworks with Exceptional Stability.
J. Am. Chem. Soc. 2008, 130, 13850−13851.
(19) He, T.; Zhang, Y. Z.; Kong, X. J.; Yu, J. M.; Lv, X. L.; Wu, Y. F.;
Guo, Z. J.; Li, J. R. Zr(IV)-Based Metal-Organic Framework with T-
Shaped Ligand: Unique Structure, High Stability, Selective Detection,
(36) Deng, H.; Doonan, C. J.; Furukawa, H.; Ferreira, R. B.; Towne,
J.; Knobler, C. B.; Wang, B.; Yaghi, O. M. Multiple Functional Groups
of Varying Ratios in Metal-Organic Frameworks. Science 2010, 327,
846−850.
2−
and Rapid Adsorption of Cr2O7 in Water. ACS Appl. Mater.
Interfaces 2018, 10, 16650−16659.
(20) Zhao, Y. M.; Qi, S. B.; Niu, Z.; Peng, Y. L.; Shan, C.; Verma,
G.; Wojtas, L.; Zhang, Z. J.; Zhang, B.; Feng, Y. Q.; Chen, Y. S.; Ma,
S. Q. Robust Corrole-Based Metal−Organic Frameworks with Rare 9-
Connected Zr/Hf-Oxo Clusters. J. Am. Chem. Soc. 2019, 141, 14443.
(21) Furukawa, H.; Gandara, F.; Zhang, Y. B.; Jiang, J.; Queen, W.
L.; Hudson, M. R.; Yaghi, O. M. Water adsorption in porous metal-
organic frameworks and related materials. J. Am. Chem. Soc. 2014,
136, 4369−4381.
(37) Pizarro, S.; Gallardo, M.; Leyton, C.; Castro, E.; Gajardo, F.;
Delgadillo, A. Effect of pH in the photoluminescence of a ruthenium
complex featuring a derivative of the ligand pyrazine[2,3-f][1,10]-
phenanthroline. Spectrochim. Acta, Part A 2015, 146, 61−65.
(38) Zhao, P. G.; Liu, N. N.; Jin, C. N.; Chen, H. X.; Zhang, Z. J.;
Zhao, L. M.; Cheng, P.; Chen, Y. UiO-66: An Advanced Platform for
Investigating the Influence of Functionalization in the Adsorption
Removal of Pharmaceutical Waste. Inorg. Chem. 2019, 58, 8787−
8792.
(39) Wang, N. N.; Zhao, Q.; Zhang, A. L. Catalytic oxidation of
organic pollutants in wastewater via a Fenton-like process under the
catalysis of HNO3-modified coal fly ash. RSC Adv. 2017, 7, 27619−
27628.
(40) Jung, B. K.; Hasan, Z.; Jhung, S. H. Adsorptive removal of 2, 4-
dichlorophenoxyacetic acid (2, 4-D) from water with a metal−organic
framework. Chem. Eng. J. 2013, 234, 99−105.
(41) Hasan, Z.; Choi, E. J.; Jhung, S. H. Adsorption of naproxen and
clofibric acid over a metal−organic framework MIL-101 function-
alized with acidic and basic groups. Chem. Eng. J. 2013, 219, 537−544.
(42) Luo, Z. D.; Fan, S. R.; Liu, J. Q.; Liu, W. C.; Shen, X.; Wu, C.
P.; Huang, Y. J.; Huang, G. X.; Huang, H.; Zheng, M. B. A 3D stable
metal-organic framework for highly efficient adsorption and removal
of drug contaminants from water. Polymers 2018, 10, 209−223.
(22) Feng, D.; Jiang, H. L.; Chen, Y. P.; Gu, Z. Y.; Wei, Z.; Zhou, H.
C. Metal-organic frameworks based on previously unknown Zr8/Hf8
cubic clusters. Inorg. Chem. 2013, 52, 12661−12667.
(23) Feng, D.; Gu, Z. Y.; Li, J. R.; Jiang, H. L.; Wei, Z.; Zhou, H. C.
Zirconium-Metalloporphyrin PCN-222: Mesoporous Metal-Organic
Frameworks with Ultrahigh Stability as Biomimetic Catalysts. Angew.
Chem., Int. Ed. 2012, 51, 10307−10310.
(24) Feng, D.; Gu, Z.-Y.; Chen, Y.-P.; Park, J.; Wei, Z.; Sun, Y.;
Bosch, M.; Yuan, S.; Zhou, H.-C. A Highly Stable Porphyrinic
Zirconium Metal−Organic Framework with shp-a Topology. J. Am.
Chem. Soc. 2014, 136, 17714−17717.
(25) Feng, D.; Chung, W. C.; Wei, Z.; Gu, Z. Y.; Jiang, H. L.; Chen,
Y. P.; Darensbourg, D. J.; Zhou, H. C. Construction of Ultrastable
Porphyrin Zr Metal−Organic Frameworks through Linker Elimi-
nation. J. Am. Chem. Soc. 2013, 135, 17105−17110.
(26) Jiang, H. L.; Feng, D. W.; Wang, K. C.; Gu, Z. Y.; Wei, Z. W.;
Chen, Y. P.; Zhou, H. C. An Exceptionally Stable, Porphyrinic Zr
Metal−Organic Framework Exhibiting pH-Dependent Fluorescence.
J. Am. Chem. Soc. 2013, 135, 13934−13938.
́
(27) Morris, W.; Volosskiy, B.; Demir, S.; Gandara, F.; McGrier, P.
L.; Furukawa, H.; Cascio, D.; Stoddart, J. F.; Yaghi, O. M. Synthesis,
J
DOI: 10.1021/acs.inorgchem.9b02950
Inorg. Chem. XXXX, XXX, XXX−XXX