Metal-Organic Frameworks with Tb4 Clusters as Nodes: Luminescent Detection of Chromium(VI) and Chemical Fixation of CO2

Article abstract of DOI:10.1021/acs.inorgchem.7b00323

Two multifunctional metal-organic frameworks based on cubane-like tetrahedron Tb₄ clusters as nodes have been synthesized and characterized. Compound 1 exhibits a 2D lanthanide-organic framework with Tb₄ clusters as nodes, and compound 2 possesses a 3D framework with Tb₄ clusters and Mn²⁺ as nodes. Interestingly, luminescent investigations on them reveal that the two compounds can act as recyclable luminescent probes for chromium(VI) anion species and the corresponding detection limit can reach 10^-7 mol/L. Furthermore, 1 and 2 own efficient catalytic activity for the chemical fixation of CO₂ with epoxides under mild conditions. Importantly, they both can be recycled at least three times without compromising the activity.

Full text of DOI:10.1021/acs.inorgchem.7b00323

Article
pubs.acs.org/IC
Metal−Organic Frameworks with Tb4 Clusters as Nodes: Luminescent
Detection of Chromium(VI) and Chemical Fixation of CO2
Jie Dong, Hang Xu, Sheng-Li Hou, Zhi-Lei Wu, and Bin Zhao*
Department of Chemistry, Key Laboratory of Advanced Energy Material Chemistry, MOE, and Collaborative Innovation Center of
Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071, China
S
* Supporting Information
ABSTRACT: Two multifunctional metal−organic frameworks based on
cubane-like tetrahedron Tb4 clusters as nodes have been synthesized and
characterized. Compound 1 exhibits a 2D lanthanide−organic framework
with Tb4 clusters as nodes, and compound 2 possesses a 3D framework
with Tb4 clusters and Mn2+ as nodes. Interestingly, luminescent
investigations on them reveal that the two compounds can act as
recyclable luminescent probes for chromium(VI) anion species and the
corresponding detection limit can reach 10−7 mol/L. Furthermore, 1 and
2 own efficient catalytic activity for the chemical fixation of CO2 with
epoxides under mild conditions. Importantly, they both can be recycled at
least three times without compromising the activity.
developing methods or technologies to transform CO2 into
valuable raw materials.15 One of the most promising
technologies is the coupling reaction of CO2 and epoxides to
form cyclic carbonates,16 which are important chemical
intermediates and have been widely used in the synthesis of
specialty fine chemicals and pharmaceuticals. Furthermore, the
cycloaddition of CO2 to an epoxide product with no
byproducts is in accordance with green chemistry and atomic
economy.15c,e With large-sized porosity and Lewis acidic sites,
stable lanthanide-based MOFs are considered to be ideal
candidates for CO2 conversion with epoxides. As a kind of
effective heterogeneous catalysis, MOF-based catalysts possess
satisfactory circulation and separability,17 which have good
application prospects in industry.
With the above considerations in mind, two MOFs,
{[Tb4(BPDC)4(μ3-OH)4(H2O)8]·11H2O}n (1) and {[Tb4Mn-
(BPDC)3(μ3-OH)4(HCOO)1.5(H2O)4]·2.5OH·8H2O}n (2),
based on Tb4 clusters as nodes were obtained (H2BPDC =
4,4′-dicarboxylate-2,2′-dipyridine anion). Compound 1 pos-
sesses a 2D framework with Tb4 as nodes, while compound 2 is
a 3D MOF based on [Tb4(OH)4]8+ clusters and transition-
metal Mn2+, which both exhibit high thermal stability.
Luminescence explorations reveal that compounds 1 and 2
can detect chromium(VI) anions with high sensitivity and
recyclability and can serve as fluorescent probes for chromium-
(VI) anions. On the other hand, in terms of CO2 conversion,
compounds 1 and 2 can efficiently catalyze the cycloaddition
reaction with CO2 and epoxides under mild conditions;
INTRODUCTION
■
As a promising class of porous materials, metal−organic
frameworks (MOFs) have attracted immense attention because
of not only their fascinating structures but also their potential
applications in gas storage,1 magnetism,2 optical property,3
chemical sensing,4 catalysis,5 etc. Among these applications,
MOFs employed as chemical sensors have been extensively
studied, and the hot issue of research mainly focused on the
detection of anions,6 cations,7 and small organic molecules,8
etc. However, a few studies have involved the detection of
chromium(VI) anion species (CrO4 or Cr2O72−), which are
2−
well-known toxic anions and pose a serious threat to human
health and the environment, having been listed as a U.S.
Environmental Protection Agency prior pollutant.9 Nowadays,
with the development of industry, more and more poisonous
chromium(VI) species are discharged, and they were
recognized or removed via conventional methods, such as ion
exchange,10 membrance separation,11 photocatalytic degrada-
tion,12 etc.13 Nevertheless, these methods have the defects of
poor regeneration and inferior chemical stability. Therefore,
MOFs that have the incomparable advantages of high
sensitivity, good regeneration, and excellent chemical stabilities
as luminescent sensors to detect chromium(VI) anions are
urgently needed to prevent chromium(VI) anions from
endangering human health and the environment.
On the other hand, carbon dioxide (CO2) chemistry has
recently attracted much attention from the scientific
community not only because the rapidly increasing atmospheric
CO2 levels are projected to have a detrimental consequence on
the global climate but also because CO2 is an inexpensive,
nontoxic, renewable, and abundant C1 building block for
organic synthesis.14 Great effort has been devoted to
Received: February 6, 2017
© XXXX American Chemical Society
A
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furthermore, these compounds can be reused at least three
times without any obvious loss in catalytic activity.
synthesis, and compound 2 was obtained. Structure analysis
suggested that compound 2 crystallizes in the cubic system with
space group I213. As illustrated in Figure S1b,c, the asymmetric
unit has two crystallographically independent Tb3+ ions, in
which the eight-coordinated Tb1 (Figure S1b) is surrounded by
three carboxylic oxygen atoms (O4, O10, and O13), three μ3-
oxygen atoms (O5, O9a, and O9b), one oxygen atom (O2AA)
from a coordinated water molecule, and one oxygen atom of a
formic anion (O16), which is derived from decarboxylation of
the H2BPDC ligand, because aromatic compounds are more
likely to decarboxylate under thermal insulation and alkaline
conditions.18 The seven-coordinated Tb2 (Figure S1c) is
surrounded by three carboxylic oxygen atoms (O11a, O11b,
and O11c), three μ3-oxygen atoms (O9a, O9b, and O9c), and
one oxygen atom (O14) from a coordinated water molecule.
Four Tb3+ ions are bridged by four μ3-OH into a tetranuclear
cluster, [Tb4(OH)4]8+ (Figure 1c), which shows a cubane-like
structure. Furthermore, each [Tb4(OH)4]8+ cluster is bridged
with six BPDC2− ligands and three formate anions (Figure S1f),
while the [Tb4(OH)4]8+ cluster in 1 is linked with eight
BPDC2− ligands. Additionally, every [Tb4(OH)4]8+ cluster in 2
is bridged with three adjacent [Tb4(OH)4]8+ clusters by three
formate anions into a 3D framework, which possesses two
kinds of different channels (Figure S2c,d) with diameters of 5
and 10.4 Å along the c direction. Six nitrogen atoms from three
BPDC2− anions complete the six-coordinated environment of
Mn2+ (Figure 1d), and the units [Tb4(OH)4]8+ with Mn2+ are
connected by BPDC2− into a 3D framework (Figure 1e). Along
the c direction, 2 presents square channels with diameters
ranging from 1.92 to 7.62 Å, and the potential total void
volume of open channels in compound 2 is about 40.5%, as
calculated by the PLATON program. Topological analysis
showed that every [Tb4(OH)4]8+ unit is bridged with six
[Mn(BPDC)3]4− units and three format anions to form an
interesting 9-connected node, and every [Mn(BPDC)3]4− unit
is linked with six [Tb4(OH)4]8+ units to form a 6-connected
node. According to this simplification, the structure of
compound 2 can be simplified as a 6,9-connected 3D
framework with a topology symbol of sqc (Figure S2b).
Powder X-ray Diffraction (PXRD) Analysis and
Thermogravimetric Analysis (TGA). The PXRD patterns
of compounds 1 and 2 are recorded in Figure S3, and the
PXRD patterns are almost in conformity with the simulated
ones, indicating that compounds 1 and 2 are pure phases.
In order to study the thermal stability of the compounds,
TGA was measured under a N2 atmosphere, which are shown
in Figure S4. The TGA curve of 1 shows that, from room
temperature to 124 °C, a weight loss of 10.12% can be
observed, which corresponds to the loss of free water molecules
(calcd: 9.83%). Then, the curve shows a weight loss of 7.04%
from 128 to 461 °C, corresponding to the loss of coordinated
water molecules (calcd: 7.15%). Subsequently, compound 1
starts to decompose above 469 °C. Also, compound 2 shows
high thermal stability. As shown in Figure S4, from room
temperature to 122 °C, a weight loss of 8.42% can be observed
in the TGA curve of 2, which corresponds to the loss of free
water molecules (calcd: 8.0%). With the temperature
increasing, the curve shows a weight loss of 7.5% from 172
to 448 °C, corresponding to the loss of coordinated water
molecules and formate anions (calcd: 7.62%). Then, compound
2 starts to decompose above 477 °C.
EXPERIMENTAL SECTION
■
Preparation of {[Tb4(BPDC)4(μ3-OH)4(H2O)8]·11H2O}n (1). A
mixture of Tb(NO3)3·6H2O (0.2 mmol, 90.6 mg), H2BPDC (0.1
mmol, 24.4 mg), 100 μL of triethylamine, 4 mL of anhydrous alcohol,
and 4 mL of distilled water was sealed in a 25 mL Teflon-lined
stainless steel autoclave. The autoclave was heated at 200 °C for 72 h
under autogenous presser and then cooled slowly to room temperature
at a rate of 2 °C/h. Colorless flaky crystals were obtained and washed
with distilled water. The yield was 65% [based on Tb(NO3)3·6H2O].
Elem anal. Calcd for compound 1: C, 28.65; H, 3.08; N, 5.57. Found:
C, 29.09; H, 2.97; N, 5.31.
Preparation of {[Tb4Mn(BPDC)3(μ3-OH)4(HCOO)1.5(H2O)4]·
2.5OH·8H2O}n (2). Compound 2 was obtained in a manner similar
to that of compound 1 except that MnCl2·4H2O (0.05 mmol, 10 mg)
was added. The yellow block crystals were washed with distilled water.
The yield was 50% [based on Tb(NO3)3·6H2O]. Elem anal. Calcd for
compound 2: C, 24.84; H, 2.76; N, 4.64. Found: C, 25.46; H, 2.36; N,
4.97.
RESULTS AND DISCUSSION
■
Structure Description of 1. Single-crystal X-ray diffraction
(XRD) analysis reveals that compound 1 crystallizes in the
tetragonal system with space group I41/acd, which shows a 2D
layer structure. In the structure, the asymmetric unit contains a
unique Tb3+ ion and one BPDC2− ligand, and the eight-
coordinated Tb3+ ion is completed by three carboxylic oxygen
atoms (O16, O19, and O20) of three BPDC2− ligands, two
oxygen atoms (O21 and O23) of two water molecules, and
three μ3-oxygen atoms (O2a, O2b, and O2c; Figure S1a). Four
Tb3+ ions are bridged by μ3-OH into a cubane-like tetranuclear
cluster [Tb4(OH)4]8+ (Figure 1a), which is further linked by
eight BPDC2− ligands into a 2D framework (Figures 1b and
S1e), possessing exposed nitrogen atom sites (Figure S1d).
Structure Description of 2. Considering the hollow
distribution sites of nitrogen atoms in compound 1, 0.05
mmol of MnCl2·4H2O (10 mg) was added in the process of
Figure 1. (a) [Tb4(OH)4]8+ units of compound 1. (b) 2D framework
of 1 along the c direction. (c) [Tb4(OH)4]8+ units of compound 2. (d)
[Mn(BPDC)3]4− units of 2. (e) 3D framework of 2 along the c
direction. Hydrogen atoms and free water molecules are omitted for
clarity.
Luminescent Behaviors and Sensing Properties. The
solid-state photoluminescence spectra of the free ligand
B
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(H2BPDC) and compounds 1 and 2 were measured under
ambient conditions by excitation at 285 nm (Figure S7).
Obviously, four characteristic emission peaks of Tb3+ are
observed at 490, 544, 584, and 622 nm, which can be attributed
5
7
to the transitions of D4 → FJ (J = 6, 5, 4, and 3) from Tb3+
ions, respectively.19 The strongest D4 → F5 transition, which
shows green-light emission, is assigned to the magnetic-dipole-
induced transition.4
5
7
To explore the influence of different anions on the
luminescence of 1, 3 mg samples of 1 were dispersed in 2.7
mL of distilled water, forming a suspension solution by an
ultrasonic method. Then 300 μL of a NamX (KmX) solution (1
× 10−2 M; X = CH3COO−, IO3 , NO3 , BrO3 , Br−, Cl−, N3 ,
−
−
−
−
SO42−, I−, BF4 , ClO4 , SCN−, Cr2O72−, CrO42−, MnO4 ) was
slowly dropped into the above solutions to form a suspension
of 1-X in distilled water (1 × 10−3 M). With the perturbation of
various anions, the resultant suspensions were monitored using
a fluorescence spectrophotometer, and the corresponding
luminescence curves still showed characteristic emission peaks
(Figure S8) of Tb3+ ions. Then only the dominant emission
peaks at 544 nm were recorded in Figure 2. Obviously, most
−
−
−
Figure 3. Emission spectra of 1 with different concentrations of
2−
2−
Cr2O7 ions and the luminescence intensity versus Cr2O7
concentration plot.
concentration of Cr2O72−, and Ksv represents the quenching
rate constant),20 which is close to the Stern−Volmer equation
I0/I = 1 + Ksv[Cr2O72−]. The Ksv value is calculated to be 1.13
× 104 L/mol, revealing that Cr2O72− displays a high quenching
efficiency on the emission of compound 1.
Because of the requirements of recyclability and economy for
luminescent probes in practical applications, it is necessary to
investigate the recycling performance of compound 1 as a
2−
Cr2O7 luminescent probe. Herein, we attempted to simply
immerse 1 in the water solution of 10−3 M Cr2O7 ions for
2−
2−
minutes to form 1-Cr2O72−, and then 1-Cr2O7 was washed
with water several times. As shown in Figures 4a and S12, the
luminescence intensity and PXRD pattern of the recycled 1 are
well consistent with the original results. Also, those
experimental results agree with the original ones after being
recycled five times, which indicates that compound 1 as a
5
7
Figure 2. Ratio of D4 → F5 transition intensities of 1 immersed in
2−
Cr2O7 probe can be recycled with a fast and simple method.
various NamX (KmX) aqueous solutions (monitored at 544 nm).
anions display negligible influence on the emission or weaken
2−
2−
the luminescence to some extent, while Cr2O7 and CrO4
exhibit a drastic quenching effect on the luminescence of 1,
which can be clearly observed, indicating that compound 1 can
2−
2−
act as a promising chemical sensor of Cr2O7 and CrO4
among various anions. Because of the similar luminescent
2−
2−
quenching phenomena of Cr2O7 and CrO42−, Cr2O7 was
chosen to serve as the representative in the study of
luminescent behaviors and sensing properties.
2−
In addition, to explore the detection limit of 1 as a Cr2O7
2−
probe, a series of suspensions of 1-Cr2O7 were prepared by
dropping different concentrations of Cr2O72− (10−7−10−3 mol/
L) in distilled water. The luminescence intensity of 1 gradually
decreased with increasing concentration of Cr2O72−, and the
decreased luminescence intensity still could be clearly observed
when 1 was immersed in a 10−7 mol/L Cr2O7 solution
2−
(Figure 3), indicating that the detection limit of 1 as a
luminescent probe for detecting Cr2O72− can reach 10−7 mol/L.
2−
To further explore the quenching effect of Cr2O7 on the
2−
emission, a plot of the luminescence intensity versus Cr2O7
concentration was made (Figure 3), which can be linearly fitted
into the equation I0/I = 1.120 + Ksv[Cr2O72−] (I0 and I
represent the luminescence intensity of 1 before and after the
Figure 4. (a) Luminescent intensity (544 nm) of compound 1 after
being recycled five times. (b) Luminescent intensity (544 nm) of
compound 2 after being recycled five times.
2−
addition of Cr2O7 respectively; [Cr2O72−] represents the
C
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Besides, the PXRD patterns of compound 1 immersed in
different solvents were measured and remained well consistent
with the simulated ones, indicating that the framework of 1 still
remains stable (Figure S14). Additionally, in order to testify
Table 1. Cycloaddition Reaction of CO2 with Styrene Oxide
under Various Conditions
a
2−
that there were no Cr2O7 ions remaining in the framework
after washing with water, the corresponding samples were
measured by inductively coupled plasma (ICP) spectroscopy
(Table S2), and the results show that there is only 0.012 ppm
of Cr6+ residues in the framework of compound 1 after
recycling five times, which indicates that the introduced
Cr2O7 ions have been removed completely.
Similar luminescent investigations on compound 2 were
b
entry
catalyst
TBAB(mol %)
T (°C)
t (h)
yield (%)
1a
1b
1c
2a
2b
0
1
2
1
2
2.5
2.5
2.5
0
60
60
60
60
60
12
12
12
12
12
42
78
95
<1
<1
2−
0
carried out, and the corresponding emission peaks (544 nm)
a
Reaction conditions: styrene oxide (240.3 mg, 2.0 mmol), solvent-
free, catalysts 1 (25 mg, about 2 mol %, based on Tb4 clusters) and 2
(22 mg, about 2 mol %, based on Tb4 clusters), CO2 (0.1 MPa),
TBAB (17 mg, 2.5 mol %). Determined by H NMR spectroscopy
using 1,3,5-trimethoxybenzene as an internal standard.
2−
were recorded. As shown in Figures S9 and S10, Cr2O7 still
exhibits a drastic quenching effect on the luminescence of 2,
and other anions have negligible effects on the emission.
Moreover, the detection limit of 2 as a luminescent probe for
b
1
2−
detecting Cr2O7 can also reach 10−7 mol/L. The quenching
2−
effect of Cr2O7 on the emission was also explored. A plot of
% cocatalyst tetrabutylammonium bromide (TBAB) and 2 mol
% compound 1 or compound 2 (based on Tb4 clusters),
without solvent. The desired product 4-phenyl-1,3-dioxolan-2-
one was obtained after 12 h, and the yield could reach 78% and
95%, respectively (entries 1b and 1c in Table 1). In contrast,
the value was only 42% (entry 1a in Table 1) under 2.5 mol %
TBAB without compound 1 or 2, suggesting that these
compounds play important roles in the reaction.
2−
the luminescence intensity versus Cr2O7 concentration was
made (Figure S11), which could be linearly fitted into the
equation I0/I = 1.003 + Ksv[Cr2O72−], close to the Stern−
Volmer equation I0/I = 1 + Ksv[Cr2O72−], and the Ksv value is
calculated to be 0.5 × 104 L/mol, revealing that Cr2O7
2−
displays a high quenching efficiency on the emission of
compound 2.
The recycling performance of compound 2 was also
investigated. A similar experimental process was measured,
and the corresponding results are recorded in Figures 4b and
S13, indicating that compound 2 as a luminescent probe of
To further investigate the catalytic generality of compounds,
various typical epoxide substrates were examined for the
cycloaddition reaction. As showed in Table 2, substrates with
electron-withdrawing groups generally had better yields. For
example, the cycloaddition reactions of CO2 with epichlorohy-
drin (entry 2) was effectively catalyzed in high yields (85% and
99%). When glycidyl phenyl ether (entry 3) and benzyl glycidyl
ether (entry 4) were used, the desired products were generated
with excellent yields (87% and 99%; 64% and 70%). The results
can be explained by the fact that the electron-withdrawing
substituents facilitate nucleophilic attack during the ring
opening of the epoxide. However, the aliphatic hydrocarbon
epoxide (entry 5), 1,2-epoxy-2-methylpropane (entry 6), and
propylene oxide and 1,2-epoxyoctane (entry 7) were converted
to the corresponding cyclic carbonate with low yield. In
addition, compound 2 has a little higher catalytic efficiency than
compound 1, possibly due to the different CO2 adsorption
capacities (CO2 adsorption/desorption of compound 2, as
shown in Figure S16, while CO2 adsorption/desorption of
compound 1 was not detected out), or the synergistic effect of
Mn2+ in compound 2.21
Additionally, as stable heterogeneous catalysts, the com-
pounds could be separated from the reaction mixture through
centrifugation and filtration. The recycle performances of
compounds 1 and 2 were measured, and the corresponding
results were recorded (Figure 5). ICP analysis (Table S2) of
the reaction mixture filtrate reveals only 0.012 and 0.018 ppm
of leakage from the robust frameworks, confirming the
heterogeneous nature of the reaction. It is noted that the
excellent catalytic activity of the two compounds still can be
observed after the compounds were employed three times, and
the robust frameworks of catalysts still remained intact, which is
confirmed by PXRD investigations (Figures S12 and S13).
On the basis of the reported mechanism of the cycloaddition
of CO2 and epoxides, a tentative mechanism is discussed.
Frameworks 1 and 2 with porous channels can enrich CO2 and
the substrate, then epoxides are activated by the Tb3+ sites in
2−
Cr2O7 can be recycled at least five times, with negligible loss
in the luminescent response and PXRD well consistent with the
original results. Meanwhile, the corresponding ICP (Table S2)
reveals that the recycled samples do not contain Cr2O72−, and
the recovered luminescence is attributed to the absence of
2−
Cr2O7
.
Then, the possible mechanism is discussed. First, well-
matched PXRD results suggest that the frameworks are still
intact after the introduction of Cr2O72−, proving that
luminescence quenching is not caused by collapse of the
framework. Second, from the UV−vis adsorption spectra of a
K2Cr2O7 aqueous solution (Figure S15) emerge strong
absorption bands in the ranges of 230−312 and 312−500
nm, and the excitation wavelength of 1 and 2 is 285 nm, which
2−
indicates that a Cr2O7 solution can significantly absorb the
energy of the excitation wavelength, resulting in the
luminescence quenching of 1 and 2. Third, the concentration
of Cr2O72− and the luminescent intensity can be well fitted into
the Stern−Volmer equation, indicating that the quenching
process can be attributed to the dynamic process mechanism.
That is to say, the adsorption of Cr2O72− in the UV−vis region,
as well as the collision interaction between structures and free
2−
Cr2O7 anions, consumes the energy and reduces the
luminescent intensity.
Catalytic Properties. Lanthanide metals are oxyphilic, and
many of their compounds possess Lewis acidity. Considering
the potential Lewis acidity of the two compounds, their
catalytic capacities were explored, and here the transformation
of CO2 with epoxides as a model reaction was investigated.
Styrene oxide was selected as a probe substrate to explore the
optimized reaction conditions, and the corresponding results
are recorded in Table 1. Under mild temperature (60 °C) and
pressure (0.1 MPa), the reaction was conducted using 2.5 mol
D
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Table 2. Cycloaddition Reaction of CO2 with Various
a
Substrates
Figure 5. (a) Recycle tests of 1 for the cycloaddition reaction of CO2
with styrene oxide. (b) Recycle tests of 2 for the cycloaddition reaction
of CO2 with styrene oxide.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.7b00323.
■
S
Synthesis, crystal data, IR, TGA, and PXRD (PDF)
X-ray crystallographic data in CIF format for 1 (CCDC
1520757) and 2 (CCDC 1520758) (CIF)
a
Reaction conditions: epoxides (2.0 mmol), solvent-free, catalysts 1
AUTHOR INFORMATION
Corresponding Author
*E-mail: zhaobin@nankai.edu.cn. Fax: (+86)-22-23502458.
■
and 2 (25 and 22 mg, respectively, about 2 mol %, based on Tb4
clusters), CO2 (0.1 MPa), 60 °C, TBAB (17 mg, 2.5 mol %).
b
1
Determined by H NMR spectroscopy using 1,3,5-trimethoxyben-
zene as an internal standard. Letter a in the table represents catalyst 1,
and letter b represents catalyst 2.
ORCID
Bin Zhao: 0000-0001-9003-9731
Notes
The authors declare no competing financial interest.
compounds and Br− effectively promotes the ring opening of
the epoxides. Then, CO2 and the oxygen anion of the opened
ring react to form an alkylcarbonate salt. Finally, the
corresponding cyclic carbonates are obtained through ring
closure (Figure S18).
ACKNOWLEDGMENTS
■
This work was supported by the NSFC (Grants 21625103,
21571107, and 21473121), Project 111 (Grant B12015), and
the SFC of Tianjin (Grant 15JCZDJC37700).
REFERENCES
■
CONCLUSION
■
(1) Li, B.; Wen, H. M.; Cui, Y.; Qian, G.; Chen, B. Multifunctional
lanthanide coordination polymers. Prog. Polym. Sci. 2015, 48, 40−84.
(2) (a) Weng, D. F.; Wang, Z. M.; Gao, S. Framework-structured
weak ferromagnets. Chem. Soc. Rev. 2011, 40, 3157−3181. (b) Chang,
L. X.; Xiong, G.; Wang, L.; Cheng, P.; Zhao, B. A 24-Gd nanocapsule
with a large magnetocaloric effect. Chem. Commun. 2013, 49, 1055−
1057. (c) Rinehart, J. D.; Long, J. R. Exploiting single-ion anisotropy in
the design of f-element single-molecule magnets. Chem. Sci. 2011, 2,
2078−2085. (d) Roy, S.; Chakraborty, A.; Maji, T. K. Lanthanide−
organic frameworks for gas storage and as magneto-luminescent
materials. Coord. Chem. Rev. 2014, 273−274, 139−164. (e) Shi, P. F.;
Zheng, Y. Z.; Zhao, X. Q.; Xiong, G.; Zhao, B.; Wan, F. F.; Cheng, P. 3
D MOFs containing trigonal bipyramidal Ln5 clusters as nodes: large
magnetocaloric effect and slow magnetic relaxation behavior. Chem. -
Eur. J. 2012, 18, 15086−15091. (f) Zhang, P.; Zhang, L.; Wang, C.;
In conclusion, two multifunctional MOFs, {[Tb4(BPDC)4(μ3-
OH)4(H2O)8]·11H2O}n and {[Tb4Mn(BPDC)3(μ3-
OH)4(HCOO)1.5(H2O)4]·2.5OH·8H2O}n, were synthesized
and characterized. Characterization of the structures showed
that compound 1 exhibits a 2D framework with Tb4 clusters as
nodes and compound 2 possesses a 3D framework with Tb4
clusters and Mn2+ as nodes. Interestingly, they both possess the
capacity to detect chromium(VI) anion species after being
recycled, and the detection limits for both can reach 10−7 mol/
L. Importantly, these multifunctional compounds are demon-
strated as new types of effective heterogeneous catalysts to
catalyze the cyclization reaction with epoxides and CO2, and
the recycling number can reach three times.
E
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Xue, S.; Lin, S. Y.; Tang, J. Equatorially coordinated lanthanide single
ion magnets. J. Am. Chem. Soc. 2014, 136, 4484−4487.
(8) (a) Dong, X. Y.; Wang, R.; Wang, J. Z.; Zang, S. Q.; Mak, T. C.
W. Highly selective Fe3+ sensing and proton conduction in a water-
stable sulfonate−carboxylate Tb−organic-framework. J. Mater. Chem.
A 2015, 3, 641−647. (b) Chen, B.; Yang, Y.; Zapata, F.; Lin, G.; Qian,
G.; Lobkovsky, E. B. Luminescent Open Metal Sites within a Metal−
Organic Framework for Sensing Small Molecules. Adv. Mater. 2007,
19, 1693−1696.
(9) (a) Levina, A.; Lay, P. A. Mechanistic studies of relevance to the
biological activities of chromium. Coord. Chem. Rev. 2005, 249, 281−
298. (b) Wen, G. X.; Han, M. L.; Wu, X. Q.; Wu, Y. P.; Dong, W. W.;
Zhao, J.; Li, D. S.; Ma, L. F. A multi-responsive luminescent sensor
based on a super-stable sandwich-type terbium(III)-organic frame-
work. Dalton Trans. 2016, 45, 15492−15499. (c) Liu, W.; Huang, X.;
Xu, C.; Chen, C. Y.; Yang, L. Z.; Dou, W.; Chen, W. M.; Yang, H.; Liu,
W. S. A multi-responsive regenerable europium-organic framework
luminescent sensor for Fe3+, CrVI anions, and picric acid. Chem. - Eur. J.
2016, 22, 18634. (d) Cao, C. S.; Hu, H. C.; Xu, H.; Qiao, W. Z.; Zhao,
B. Two solvent-stable MOFs as a recyclable luminescent probe for
detecting dichromate or chromate anions. CrystEngComm 2016, 18,
4445−4451.
(10) (a) Fei, H.; Bresler, M. R.; Oliver, S. R. A new paradigm for
anion trapping in high capacity and selectivity: crystal-to-crystal
transformation of cationic materials. J. Am. Chem. Soc. 2011, 133,
11110−11113. (b) Fei, H.; Han, C. S.; Robins, J. C.; Oliver, S. R. J. A
Cationic Metal−Organic Solid Solution Based on Co(II) and Zn(II)
for Chromate Trapping. Chem. Mater. 2013, 25, 647−652. (c) Fu, H.-
R.; Xu, Z.-X.; Zhang, J. Water-Stable Metal−Organic Frameworks for
Fast and High Dichromate Trapping via Single-Crystal-to-Single-
Crystal Ion Exchange. Chem. Mater. 2015, 27, 205−210. (d) Lalonde,
M.; Bury, W.; Karagiaridi, O.; Brown, Z.; Hupp, J. T.; Farha, O. K.
Transmetalation: routes to metal exchange within metal−organic
frameworks. J. Mater. Chem. A 2013, 1, 5453. (e) Wawrzkiewicz, M.
Removal of C.I. Basic Blue 3 dye by sorption onto cation exchange
resin, functionalized and non-functionalized polymeric sorbents from
aqueous solutions and wastewaters. Chem. Eng. J. 2013, 217, 414−425.
(f) Boyer, T. H.; Singer, P. C. Stoichiometry of Removal of Natural
Organic Matter by Ion Exchange. Environ. Sci. Technol. 2008, 42, 608−
613.
(3) (a) Cui, Y.; Song, R.; Yu, J.; Liu, M.; Wang, Z.; Wu, C.; Yang, Y.;
Wang, Z.; Chen, B.; Qian, G. Dual-emitting MOF supersetdye
composite for ratiometric temperature sensing. Adv. Mater. 2015, 27,
1420−1425. (b) He, Y.; Furukawa, H.; Wu, C.; O’Keeffe, M.; Krishna,
R.; Chen, B. Low-energy regeneration and high productivity in a
lanthanide-hexacarboxylate framework for high-pressure CO2-CH4-H2
separation. Chem. Commun. 2013, 49, 6773−6775. (c) Hu, Z.; Deibert,
B. J.; Li, J. Luminescent metal-organic frameworks for chemical sensing
and explosive detection. Chem. Soc. Rev. 2014, 43, 5815−5840.
(d) Liu, Y.; Pan, M.; Yang, Q. Y.; Fu, L.; Li, K.; Wei, S. C.; Su, C. Y.
Dual-Emission from a Single-Phase Eu−Ag Metal−Organic Frame-
work: An Alternative Way to Get White-Light Phosphor. Chem. Mater.
2012, 24, 1954−1960. (e) Rocha, J.; Carlos, L. D.; Paz, F. A.; Ananias,
D. Luminescent multifunctional lanthanides-based metal-organic
frameworks. Chem. Soc. Rev. 2011, 40, 926−940.
(4) (a) Liu, W. S.; Jiao, T. O.; Li, Y. Z.; Liu, Q. Z.; Tan, M. Y.; Wang,
H.; Wang, L. F. Lanthanide Coordination Polymers and Their Ag+-
Modulated Fluorescence. J. Am. Chem. Soc. 2004, 126, 2280−2281.
(b) Liu, B.; Wu, W. P.; Hou, L.; Wang, Y. Y. Four Uncommon
Nanocage-based Ln-MOFs: Highly Selective Luminescent Sensing for
Cu2+ ions and Selective CO2 Capture. Chem. Commun. 2014, 50,
8731−8734. (c) Xu, H.; Hu, H. C.; Cao, C. S.; Zhao, B. Lanthanide
Organic Frameworks as a Regenerable Luminescent Probe for Fe3+.
Inorg. Chem. 2015, 54, 4585−4587.
(5) (a) Han, J. W.; Hill, C. L. A Coordination Network That
Catalyzes O2-Based Oxidations. J. Am. Chem. Soc. 2007, 129, 15094−
15095. (b) Gandara, F.; Puebla, E. G.; Iglesias, M.; Proserpio, D. M.;
́
Snejko, N.; Monge, M. A. Controlling the Structure of Arenedisul-
fonates toward Catalytically Active Materials. Chem. Mater. 2009, 21,
655−661. (c) Qin, J.; Wang, P.; Li, Q. Y.; Zhang, Y.; Yuan, D.; Yao, Y.
M. Catalytic production of cyclic carbonates mediated by lanthanide
phenolates under mild conditions. Chem. Commun. 2014, 50, 10952−
10955. (d) Decortes, A.; Castilla, A. M.; Kleij, A. W. Salen-complex-
mediated formation of cyclic carbonates by cycloaddition of CO2 to
epoxides. Angew. Chem., Int. Ed. 2010, 49, 9822−9837. (e) Guo, X.;
Zhu, G.; Li, Z.; Sun, F.; Yang, Z.; Qiu, S. A lanthanide metal-organic
framework with high thermal stability and available Lewis-acid metal
sites. Chem. Commun. 2006, 3172−3174. (f) Whiteoak, C. J.; Kielland,
N.; Laserna, V.; Escudero-Adan, E. C.; Martin, E.; Kleij, A. W. A
powerful aluminum catalyst for the synthesis of highly functional
organic carbonates. J. Am. Chem. Soc. 2013, 135, 1228−1231.
(g) Gong, Y. N.; Ouyang, T.; He, C. T.; Lu, T. B. Photoinduced
water oxidation by an organic ligand incorporated into the framework
of a stable metal-organic framework. Chem. Sci. 2016, 7, 1070−1075.
(6) (a) Xu, H.; Cao, C. S.; Zhao, B. A water-stable lanthanide-organic
framework as a recyclable luminescent probe for detecting pollutant
phosphorus anions. Chem. Commun. 2015, 51, 10280−10283.
(b) Chen, B. L.; Wang, L. B.; Zapata, F.; Qian, G. D.; Lobkovsky,
E. B. A Luminescent Microporous Metal-Organic Framework for the
Recognition and Sensing of Anions. J. Am. Chem. Soc. 2008, 130,
6718−6719. (c) Duan, T. W.; Yan, B.; Weng, H. Europium activated
yttrium hybrid microporous system for luminescent sensing toxic
anion of Cr(VI) species. Microporous Mesoporous Mater. 2015, 217,
196−202. (d) Li, G. P.; Liu, G.; Li, Y. Z.; Hou, L.; Wang, Y. Y.; Zhu, Z.
H. Uncommon pyrazoyl-carboxyl bifunctional ligand-based micro-
porous lanthanide systems: sorption and luminescent sensing
properties. Inorg. Chem. 2016, 55, 3952−3959.
(11) Chakravarti, A. K.; Chowdhury, S. B.; Chakrabarty, S.;
Chakrabarty, T.; Mukherjee, D. C. Liquid membrane multiple
emulsion process of chromium(VI) separation from waste waters.
Colloids Surf., A 1995, 103, 59−71.
(12) Shaham-Waldmann, N.; Paz, Y. Beyond charge separation: The
effect of coupling between titanium dioxide and CNTs on the
adsorption and photocatalytic reduction of Cr(VI). Chem. Eng. J. 2013,
231, 49−58.
(13) (a) Blaney, L. M.; Cinar, S.; SenGupta, A. K. Hybrid anion
exchanger for trace phosphate removal from water and wastewater.
Water Res. 2007, 41, 1603−1613. (b) Prasanna, S. V.; Vishnu Kamath,
P. Chromate uptake characteristics of the pristine layered double
hydroxides of Mg with Al. Solid State Sci. 2008, 10, 260−266.
(14) Sakakura, T.; Choi, J. C.; Yasuda, H. Transformation of Carbon
Dioxide. Chem. Rev. 2007, 107, 2365−2387.
(15) (a) Wang, J. Y.; Huang, L.; Yang, R. Y.; Zhang, Z.; Wu, J. W.;
Gao, Y. S.; Wang, Q.; O’Hare, D.; Zhong, Z. Y. Recent advances in
solid sorbents for CO2 capture and new development trends. Energy
Environ. Sci. 2014, 7, 3478−3518. (b) Keith, D. W. Why Capture CO2
from the Atmosphere. Science 2009, 325, 1654−1655. (c) Aresta, M.;
Dibenedetto, A.; Angelini, A. Catalysis for the valorization of exhaust
carbon: from CO2 to chemicals, materials, and fuels. technological use
of CO2. Chem. Rev. 2014, 114, 1709−1742. (d) Jiang, H. L.; Tsumori,
N.; Xu, Q. A series of (6,6)-connected porous lanthanide-organic
framework enantiomers with high thermostability and exposed metal
sites: scalable syntheses, structures, and sorption properties. Inorg.
Chem. 2010, 49, 10001−10006. (e) Markewitz, P.; Kuckshinrichs, W.;
(7) (a) Zhao, B.; Chen, X. Y.; Cheng, P.; Liao, D. Z.; Yan, S. P.; Jiang,
Z. H. Coordination Polymers Containing 1D Channels as Selective
Luminescent Probes. J. Am. Chem. Soc. 2004, 126, 15394−15395.
(b) Chen, B.; Wang, L.; Xiao, Y.; Fronczek, F. R.; Xue, M.; Cui, Y.;
Qian, G. A luminescent metal-organic framework with Lewis basic
pyridyl sites for the sensing of metal ions. Angew. Chem., Int. Ed. 2009,
48, 500−503. (c) Zhao, X. Q.; Zhao, B.; Shi, W.; Cheng, P. Structures
and luminescent properties of a series of Ln−Ag heterometallic
coordination polymers. CrystEngComm 2009, 11, 1261−1269.
Leitner, W.; Linssen, J.; Zapp, P.; Bongartz, R.; Schreiber, A.; Muller,
̈
T. E. Worldwide innovations in the development of carbon capture
technologies and the utilization of CO2. Energy Environ. Sci. 2012, 5,
7281−7305. (f) Sumida, K.; Rogow, D. L.; Mason, J. A.; McDonald, T.
F
DOI: 10.1021/acs.inorgchem.7b00323
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
M.; Bloch, E. D.; Herm, Z. R.; Bae, T. H.; Long, J. R. Carbon dioxide
capture in metal-organic frameworks. Chem. Rev. 2012, 112, 724−781.
(16) (a) Yoshida, M.; Ihara, M. Novel methodologies for the
synthesis of cyclic carbonates. Chem. - Eur. J. 2004, 10, 2886−2893.
(b) Li, P. Z.; Wang, X. J.; Liu, J.; Lim, J. S.; Zou, R. Q.; Zhao, Y. L. A
triazole-containing metal-organic frameworks as a highly effective and
substrate size-dependent catalyst for CO2 conversion. J. Am. Chem. Soc.
2016, 138, 2142−2145.
(17) Zhao, Y.; Tian, J. S.; Qi, X. H.; Han, Z. N.; Zhuang, Y. Y.; He, L.
N. Quaternary ammonium salt-functionalized chitosan: An easily
recyclable catalyst for efficient synthesis of cyclic carbonates from
epoxides and carbon dioxide. J. Mol. Catal. A: Chem. 2007, 271, 284−
289.
(18) (a) Zheng, Q. X.; Morimoto, M.; Takanohashi, T. A novel
process for the production of aromatic hydrocarbons from brown coal
in water medium by hydrothermal oxidation and catalytic hydro-
thermal decarboxylation. Fuel 2016, 182, 437−445. (b) Bernard, A.
M.; Cerioni, G.; Piras, P. P. Mechanism of decarbalkoxylation of
arylmethylenepropanedioic acid dimethyl esters. Tetrahedron 1990, 46,
3929−3940. (c) Krapcho, A. P.; Ciganek, E. The krapcho deal-
koxycarbonylation reaction of esters with a-electron-withdrawing
substituents. Organic Reactions 2013, 81, 1−536.
(19) (a) Cui, Y.; Xu, H.; Yue, Y.; Guo, Z.; Yu, J.; Chen, Z.; Gao, J.;
Yang, Y.; Qian, G.; Chen, B. A luminescent mixed-lanthanide metal-
organic framework thermometer. J. Am. Chem. Soc. 2012, 134, 3979−
3982. (b) Zhao, J.; Wang, Y. N.; Dong, W. W.; Wu, Y. P.; Li, D. S.;
Zhang, Q. C. A Robust Luminescent Tb(III)-MOF with Lewis Basic
Pyridyl Sites for the Highly Sensitive Detection of Metal Ions and
Small Molecules. Inorg. Chem. 2016, 55, 3265−3271. (c) Lu, W. G.;
Jiang, L.; Feng, X. L.; Lu, T. B. Three-dimensional lanthanide anionic
metal-organic frameworks with tunable luminescent properties
induced by cation exchange. Inorg. Chem. 2009, 48, 6997−6999.
(d) Gong, Y. N.; Jiang, L.; Lu, T. B. A highly stable dynamic
fluorescent metal-organic framework for selective sensing of nitro-
aromatic explosives. Chem. Commun. 2013, 49, 11113−11115.
(20) (a) Keizer, J. Nonlinear fluorescence quenching and the origin
of positive curvature in stern-volmer plots. J. Am. Chem. Soc. 1983,
105, 1494−1498. (b) Lakos, Z.; Szarka, A.; Koszorus, L.; Somogyi, B.
Quenching-resolved emission anisotropy: a steady state fluorescence
method to study protein dynamics. J. Photochem. Photobiol., B 1995,
27, 55−60. (c) Kent, C. A.; Liu, D.; Meyer, T. J.; Lin, W. B. Amplified
luminescence quenching of phosphorescent metal-organic frameworks.
J. Am. Chem. Soc. 2012, 134, 3991−3994. (d) Zheng, M.; Tan, H. Q.;
Xie, Z. Q.; Zhang, L. G.; Jing, X. B.; Sun, Z. C. Fast response and high
sensitivity europium metal organic framework fluorescent probe with
chelating terpyridine sites for Fe3+. ACS Appl. Mater. Interfaces 2013, 5,
1078−1083.
(21) (a) Valyaev, D. A.; Lavigne, G.; Lugan, N. Manganese
organometallic compounds in homogeneous catalysis: Past, present,
and prospects. Coord. Chem. Rev. 2016, 308, 191−235. (b) Sampson,
M. D.; Kubiak, C. P. Manganese Electrocatalysts with Bulky Bipyridine
Ligands: Utilizing Lewis Acids To Promote Carbon Dioxide Reduction
at Low Overpotentials. J. Am. Chem. Soc. 2016, 138, 1386−1393.
G
DOI: 10.1021/acs.inorgchem.7b00323
Inorg. Chem. XXXX, XXX, XXX−XXX