UiO-68-PT MOF-Based Sensor and Its Mixed Matrix Membrane for Detection of HClO in Water

Article abstract of DOI:10.1021/acs.inorgchem.9b01032

As an important type of reactive oxygen species (ROS), hypochloric acid (HClO) is closely linked with our daily life, and its convenient and rapid detection is very significant and imperative. Fluorescent and visual probes are being recognized as powerful and convenient tools for detection of ROS in the environment and living organisms by visualizing and imaging. In this contribution, a new metal-organic framework-based fluorescent probe UiO-68-PT, which was generated from a phenthiazine-decorated benzimidazole bridging dicarboxyl ligand and ZrCl₄ under solvothermal conditions via in situ one-pot approach, is reported. The obtained UiO-68-PT features a unique HClO and Vitamin C-triggered reversible redox process, which is accompanied by both visual and fluorescence changes. Therefore, it can be a highly sensitive, specific, and reusable sensor to detect HClO species in water via both visual and fluorogenic observation (turn-on). Furthermore, its mixed membrane material (MMM) was fabricated by the combination of UiO-68-PT and poly(vinyl alcohol), and the obtained hydrophilic MMM can be used as a reversible colorimetric card for visual detection of the HClO in aqueous solution.

Full text of DOI:10.1021/acs.inorgchem.9b01032

Article
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
pubs.acs.org/IC
UiO-68-PT MOF-Based Sensor and Its Mixed Matrix Membrane for
Detection of HClO in Water
Qian-Ying Li, Yan-An Li,* Qun Guan, Wen-Yan Li, Xiao-Jie Dong, and Yu-Bin Dong*
College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for
Chemical Imaging in Universities of Shandong, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong
Normal University, Jinan 250014, P. R. China
*
S Supporting Information
ABSTRACT: As an important type of reactive oxygen species (ROS), hypochloric acid (HClO) is closely linked with our daily
life, and its convenient and rapid detection is very significant and imperative. Fluorescent and visual probes are being recognized
as powerful and convenient tools for detection of ROS in the environment and living organisms by visualizing and imaging. In
this contribution, a new metal−organic framework-based fluorescent probe UiO-68-PT, which was generated from a
phenthiazine-decorated benzimidazole bridging dicarboxyl ligand and ZrCl under solvothermal conditions via in situ one-pot
4
approach, is reported. The obtained UiO-68-PT features a unique HClO and Vitamin C-triggered reversible redox process,
which is accompanied by both visual and fluorescence changes. Therefore, it can be a highly sensitive, specific, and reusable
sensor to detect HClO species in water via both visual and fluorogenic observation (turn-on). Furthermore, its mixed
membrane material (MMM) was fabricated by the combination of UiO-68-PT and poly(vinyl alcohol), and the obtained
hydrophilic MMM can be used as a reversible colorimetric card for visual detection of the HClO in aqueous solution.
8
INTRODUCTION
group, and so on developed a series of HClO-specific
■
9
,10
fluorescent probes, in which various fluorophores
such as
As a very important type of reactive oxygen species (ROS),
hypochloric acid (HClO) plays a vital role in our daily life and
rhodamine, boron-dipyrromethene (BODIPY), fluorescein,
naphthalimide, and so on were chosen as the fluorescence
response groups. All these organic fluorophores, however,
make the probes possess advantage in detecting HClO in
organic or organic cosolvents over the aqueous solution due to
their organic nature. Even dispersed in the cosolvent system,
the organic probes are still prone to aggregate; furthermore,
they induce the aggregation-caused quenching (ACQ), and
this will inevitably limit their application in aqueous system
such as environmental water monitoring and assessment.
As an important class of porous crystalline hybrid materials,
metal−organic frameworks (MOFs) have received enormous
innate immune system of the living organism. For example,
HClO ranging from 1 × 10−5 to 1 × 10−2 M is extensively used
1
for antimicrobial treatment of tap water. On the one hand, in
vivo, HClO, which is produced from H O and chloride ions
2
2
catalyzed by myeloperoxidase (MPO), acts as an intracellular
regulator and can activate cell differentiation, proliferation, and
the immune system during physiological and pathological
11
2
processes. On the other hand, excessive HClO could oxidize
nucleic acids, proteins, cholesterol, lipids, and so on,
consequently leading to tissue damage and causing various
diseases such as angiocardiopathy, lung injury, osteoarthritis,
atherosclerosis, and even cancer. Therefore, the development
of efficient and convenient methods for detecting HClO is very
significant and urgently required.
12
3
attention due to their numerous potential applications. In
principle, organic fluorophores could be grafted on MOF
frameworks via either in situ one-pot synthesis or postsynthetic
modification (PSM). In doing so, the possible ACQ effect
Fluorescent probe-based method has been recognized as a
powerful tool to detect small molecular species such as HClO
due to their highly sensitive, selective, real-time, and easy
Received: April 9, 2019
4
−6
7
manipulating nature.
For example, Nagano’s group, Ma’s
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.9b01032
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
should be averted because of their orderly arrangement in
2H, −CH
2
−), 3.90 (s, 3H, −CH
3
), 3.90(s, 3H, −CH
3
), 3.43−3.40 (t,
1
3
2
H, −CH −), 1.59−1.54 (m, 2H, −CH −). Anal. (%) calcd: C 72.94,
MOF frameworks. Besides, the large surface areas of MOFs
could facilitate the contact between the MOF-based probes
and the analytes; moreover, their open channels would permit
a rapid and uncommitted diffusion of the analytes.
Consequently, a fast sensing response could be achieved.
Very recently, an attractive approach has been developed for
the preparation of MOF-based and polymer-involved mixed
2
2
H 4.99, N 6.72; Found: C 72.81, H 5.07, N 6.64.
The as-synthesized esterified ligand (1 mmol, 0.625 g) was stirred
in a tetrahydrofuran (THF) (20 mL)/H O (50 mL) solution of
NaOH (25 mmol, 1.0 g) at 40 °C for 12 h. After removal of THF in
vacuum, the residue was heated, until the solid was fully dissolved;
then, the resulting solution was acidified with diluted HCl, until no
more precipitate was generated (pH < 2). The formed precipitate was
washed with water and dried in air to afford H L-PT as white solids
(0.59 g, yield 98%). IR (KBr pellet cm ): 2963 (m), 1688 (vs), 1607
2
14
matrix membranes (MMMs). This alternative way not only
realized the MOF processability but also made the MOF-based
shaped devices for the practical applications in water
monitoring and treatment possible.
2
−
1
(s), 1458 (s), 1424 (m), 1323 (s), 1294 (s), 1184 (s), 1016 (s), 769
(s), 743 (s), 547 (w). H NMR (400 MHz, DMSO-d
ppm): 8.19−8.18 (d, 1H, -C H -), 8.18−8.17 (d, 2H, -C H -), 8.05−
1
, 25 °C, TMS,
6
In this contribution, we report a novel UiO-68 type of MOF,
namely, UiO-68-PT, which was prepared by the combination
6
2
6
4
8
.04 (d, 2H, -C H -), 8.04−8.03 (d, 2H, -C H -), 7.60−7.58 (d, 1H,
6
4
6
4
-
C H -), 7.58−7.56 (d, 2H, -C H -), 7.24−7.22 (d, 1H, −CH−),
6
2
6
4
of the prefunctionalized dicarboxylic acid ligand H L-PT and
2
7
2
3
.13−7.12 (d, 2H, -C H -), 7.10−7.08 (d, 2H, -C H -), 6.94−6.90 (t,
6
4
6
4
Zr(IV) salt under solvothermal conditions (Scheme 1). The
H, -C H -), 6.63−6.61 (d, 2H, -C H -), 4.10−4.07 (t, 2H, −CH −),
6
4
6
4
2
.44−3.47 (t, 2H, −CH −), 1.57−1.54 (m, 2H, −CH −). Anal. (%)
2
2
Scheme 1. Synthesis of H L-PT and UiO-68-PT
2
calcd: C 72.34, H 4.55, N 7.03; Found: C 72.66, H 4.67, N 6.96.
Synthesis of UiO-68-PT. ZrCl (9.6 mg, 0.041 mmol), H L-PT
15 mg, 0.025 mmol), and acetic acid (120 μL) were dissolved in
4
2
(
dimethylformamide (DMF; 3.2 mL) and then filtered into a Pyrex
glass tube. The tightly capped flasks were kept in an oven at 100 °C
under static conditions for 24 h. The product was isolated by
centrifugation and washed with DMF (three times). The obtained
powder was immersed in fresh DMF (80 °C, 6 h) and then in alcohol
(
60 °C, 48 h), with the soaking solvent replaced every 12 h to
exchange the alcohol. The product was further washed with alcohol
(
8
1
three times) and dried at 80 °C to provide UiO-68-PT (3.79 mg) in
0% yield. IR (KBr pellet cm ): 3338 (m), 2971 (m), 1592 (m),
417 (s), 1250 (s), 1104 (w), 778 (s), 659 (s). Anal. (%) calcd for the
−
1
desolvated sample C216H154N O S Zr : C 60.00, H 3.65, N 5.93, S
18
56
6
6
4
.52; Found: C 59.78, H 3.57, N 6.03, S 4.37.
Synthesis of UiO-68-PTO. UiO-68-PT (1 mg) was dispersed in 1
mL of water, and then 10 μL of newly prepared HClO solution (0.1
M) was added; the mixture changed from white to red immediately.
After it was centrifuged and washed with water, ethanol, and ether,
−1
UiO-68-PTO was obtained. IR (KBr pellet cm ): 3370 (w), 2973
w), 1588 (s), 1538 (s), 1417 (s), 1249 (w), 1166 (w), 1086 (w),
045 (w), 1017 (w), 871 (w), 778 (w), 755 (w). Anal. (%) calcd for
the desolvated sample C216H154N O S Zr : C 59.65, H 3.57, N 5.80,
(
1
18
56
6
6
S 4.42; Found: C 59.02, H 3.78, N 5.93, S 4.26.
obtained UiO-68-PT with phenthiazine-based moiety is a
highly sensitive and selective MOF-based probe for detecting
HClO via both visual and fluorogenic ways (turn-on). So far as
we know, this is the first reusable MOF-based fluorescent
probe for HClO. More importantly, by mixing UiO-68-PT
with poly(vinyl alcohol) (PVA), a UiO-68-PT-based MMM
was fabricated, and it can be a reusable colorimetric card to
selectively detect the HClO in water.
Synthesis of UiO-68-PT′. UiO-68-PTO (1 mg) was dispersed in
1
mL of water, and then 50 μL of newly prepared Vitamin C (VC)
solution (0.1 M) was added. After it was stirred at room temperature
for 30 min, the reaction solution color changed from red to white.
After it was centrifuged and washed with water, ethanol, and ether,
1
5
−1
UiO-68-PT′ was obtained. IR (KBr pellet cm ): 3380 (w), 2970
(w), 1588 (s), 1538 (s), 1416 (s), 1250 (w), 1181 (w), 1096 (w),
1018 (w), 826 (w), 778 (w), 753 (w). Anal. (%) calcd for the
desolvated sample C216H154N O S Zr : C 60.00, H 3.65, N 5.93, S
18
56
6
6
EXPERIMENTAL SECTION
4.52; Found: C 60.21, H 3.76, N 6.12, S 4.49.
MS and H NMR Measurement on the Digested MOFs. In a
■
1
Synthesis of H L-PT. A mixture of 10-(3-(4,7-dibromo-1H-
2
typical procedure, ∼10 mg of activated MOF sample was sonicated in
benzo[d]imidazol-1-yl)propyl)-10H-phenothiazine (1 mmol, 0.515
g), 4-methoxylcarbonylphenylboronic acid (3 mmol, 0.54 g), CsF
4.75 mmol, 0.72 g), and tetrakis(triphenylphosphine) palladium
0.33 mmol, 0.38 g) in anhydrous dioxane (50 mL) was refluxed for
1
mL of dimethyl sulfoxide and 10 μL of 30% hydrogen fluoride
aqueous solution. Thereafter, the system was diluted with H O, until
no more precipitate formed. The generated organic species was
(
(
2
2
collected by centrifugation, washed with H O, and dried in vacuo for
4 h in N . After removal of the solvent in vacuum, the crude product
2
2
1
MS and H NMR study.
was purified by column chromatography (silica gel, CH Cl /ethyl
2
2
Preparation of MMMs. UiO-68-PT (10 mg) were dispersed into
an aqueous solution (3 mL) of poly(vinyl alcohol) (40 mg) and then
sonicated for 30 min. UiO-68-PT-based MMMs were obtained by
drying the obtained solution on a flat Teflon mold at 100 °C for 1 h.
acetate = 10:1) to afford the esterified ligand as white crystalline solids
−
1
(
2
7
0.363 g, yield 58%). IR (KBr pellet cm ): 3343 (m), 3051 (m),
944 (m), 1715 (s), 1456 (m), 1375 (s), 1280 (s), 1188 (s), 863 (s),
1
75 (s), 632 (w). H NMR (400 MHz, deuterated dimethyl sulfoxide
(
−
DMSO-d ), 25 °C, tetramethylsilane (TMS), ppm): 8.26 (s, 1H,
H
2
L-PT (10 mg) was dissolved into DMF (1 mL), an aqueous
solution (2 mL) of poly(vinyl alcohol) (40 mg) was added, and then
the solution was sonicated for 30 min. The H L-PT-based MMMs
6
CH−), 8.23 (s, 2H, -C H -), 8.09−8.06 (d, 2H, -C H -), 8.03−8.01
6
2
6
4
(
d, 2H, -C H -), 7.63−7.61 (d, 2H, -C H -), 7.63−7.60 (d, 2H,
2
6
4
6
4
-
C H -), 7.24−7.22 (t, 2H, -C H -), 7.14−7.11 (d, 2H, -C H -),
were obtained by drying the above solution on a flat Teflon mold at
100 °C for 1 h.
6
4
6
4
6
4
7
.09−7.06 (d, 2H, -C H -), 6.95−6.93 (t,2H, -C H -), 4.08−4.05 (t,
6
4
6
4
B
DOI: 10.1021/acs.inorgchem.9b01032
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Inorganic Chemistry
Article
2
RESULTS AND DISCUSSION
As shown in Scheme 1, the phenthiazine fluorophore with
area of UiO-68-PT is only 90.5 m /g, which is significantly
16
■
2
smaller than that of UiO-68 (4170 m /g). The pore sizes in
UiO-68-PT are centered at ca. 9.5 and 11.6 Å (Figure S2,
Supporting Information), which are also less than its parent
attached Me L-PT was prepared by Pd-catalyzed Suzuki
2
coupling reaction in DMF under reflux between 4,7-
dibromo-substituted and phenthiazine-decorated benzimida-
zole and 4-(methoxycarbonyl)benzeneboronic acid in moder-
ate yield. After successive alkali hydrolysis and acidification, the
17
UiO-68 (ca. 11.7 and 17.7 Å). Such differences clearly
resulted from pore clogging by the phenthiazine-decorated
benzimidazole moiety attached to the MOF framework.
Interestingly, the phenothiazine moiety attached UiO-68-PT
could go through a white-red-white reversible color change
with oxidant HClO and reductant VC successively in aqueous
solution. As shown in Figure 1a, after addition of the newly
prepared HClO aqueous solution, the white UiO-68-PT
changed to deep red UiO-68-PTO immediately. In addition,
the deep red color of UiO-68-PTO reverted back to white by
the addition of excess VC at room temperature for 5 min,
indicating that UiO-68-PT′ was generated. However, the
measured PXRD patterns of UiO-68-PT, UiO-68-PTO, and
UiO-68-PT′ were identical to that of the UiO-68, suggesting
that their structural integrity and crystallinity were well-
preserved during this reversible color change process (Figure
obtained H L-PT was used to synthesize the UiO-68-PT by
2
heating a mixture of H L-PT/ZrCl in DMF with the aid of
2
4
acetic acid at 100 °C for 24 h (yield, 80%).
The obtained UiO-68-PT was characterized by scanning
electron microscopy (SEM). As indicated in Figure 1a, the
1
a). Also, this visual color change was further confirmed by
their UV−vis spectra. It is different from white UiO-68-PT
and UiO-68-PT′; the deep red UiO-68-PTO showed an
intensive absorption band centered at 533 nm (Figure 1b).
Besides visual color change, this reversible process was also
accompanied by a sharp emission change. As shown in Figure
1
c, the luminescence response of UiO-68-PT toward HClO
showed that the dramatical emission intensity increase at ca.
90 nm was found to be up to 27-fold after it reacted with
3
HClO. After further addition of reducing agent VC, the strong
emission of UiO-68-PTO was quenched again. No obvious
differences for particle morphology, permanent porosity, pore
widths, and thermogravimetric behavior were observed during
this MOF-based redox process (Figure 1 and Figure S2,
Supporting Information).
This reversible color change process was further explored by
the high-resolution mass spectra (HRMS) based on the
digested MOFs by HF. As shown in Figure 2a, the existence of
L-PT species in UiO-68-PT was proved by the molecular ion
peak (m/z) at 596.1615 (Calcd: 596.1639). In the presence of
HClO, the phenothiazine group on UiO-68-PT was oxidized
in aqueous solution to afford the phenothiazine sulfoxide
containing UiO-68-PTO, which was supported by the
molecular ion peak (m/z) observed at 612.1551 (Calcd:
612.1588) (Figure 2b). Moreover, the peak (m/z = 596.1606)
Figure 1. (a) PXRD patterns and photographs (inset, scale bar: 1
μm) of UiO-68-PT, UiO-68-PTO, and UiO-68-PT′. (b) UV−Vis
spectra of UiO-68-PT, UiO-68-PTO, and UiO-68-PT′. (c)
Fluorescence change of UiO-68-PT (1 mg) in aqueous solution (1
mL) upon successive addition of HClO (0.1 M, 10 μL) and VC (0.1
M, 50 μL) (λ = 323 nm, λ = 390 nm). (inset) Photographs of the
associated with H L-PT reappeared after addition of VC,
ex
em
2
samples.
indicating that the H L-PTO linkage in UiO-68-PTO was
2
reduced and that the UiO-68-PT (UiO-68-PT′) was
obtained UiO-68-PT featured the hexagonal platelike
morphology with a diameter of ∼700 nm, which was well-
supported by the dynamic light scattering (DLS) measurement
regenerated in aqueous solution under the given conditions.
1
The H NMR of digested of MOFs showed that the H
L-PT
2
could be completely transformed during this process (Figure
S3, Supporting Information). In addition, the Fourier trans-
(
Figure S1, Supporting Information). The measured powder
X-ray diffraction (PXRD) showed UiO-68-PT has the same
form infrared (FTIR) spectrum of UiO-68-PTO showed that
16
−1
crystallographic structure with its pristine UiO-68, in which
the 2:1 ratio of tetrahedral and octahedral cages formed by the
linear organic linkers and 12-connected Zr O (OH) nodes
the characteristic band at 1045 cm
for >SO was
18
observed, which further evidenced the formation of the
phenothiazine sulfoxide during this HClO-involved oxidation
process (Figure S3, Supporting Information).
6
4
4
were observed. The permanent porosity of UiO-68-PT was
explored by measuring nitrogen gas (N ) adsorption at 77 K. It
Besides visual color change, this reversible redox process also
caused a dramatic emission change. As shown in Figure 2d, the
strong electron-donating phenothiazine moiety can quench the
benzimidazole emission via the photoinduced electron transfer
(PET) pathway. With the aid of HClO, the electron-
donating phenothiazine was transferred to phenothiazine
2
is different from UiO-68; UiO-68-PT herein showed a type-II
sorption behavior (Figure S2, Supporting Information). The
lack of hysteresis indicated that the adsorption process was
reversible and that the adsorption and desorption mechanisms
were similar. The measured Brunauer−Emmett−Teller surface
19
C
DOI: 10.1021/acs.inorgchem.9b01032
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Inorganic Chemistry
Article
Figure 2. HRMS spectra of the acid-digested UiO-68-PT (a), UiO-68-PTO (b), and UiO-68-PT′ (c). The reversible emission change mechanism
d).
(
sulfoxide, which could significantly prohibit the PET from
phenothiazine to benzimidazole; consequently, the benzimida-
zole-centered strong emission was recovered (Figure 2d). After
further reduction of UiO-68-PTO by VC, the phenothiazine-
attached UiO-68-PT was regenerated (UiO-68-PT′), and the
benzimidazole emission was quenched again.
Furthermore, this MOF-based reversible redox process was
also well-supported by the same functional group trans-
formation on the free organic linker of H L-PT, and the result
2
demonstrated that the ligand-based redox reaction readily
1
occurred under the same conditions. As shown in the H NMR
spectra (Figure S4, Supporting Information), the signals
corresponding to the αH and βH on the phenothiazine
sulfoxide underwent the clear downfield shift with a Δδ = 1.32
(
αH) and 0.63 ppm (βH) after oxidation. Meanwhile, the αH
Figure 3. (a) Emission spectra of UiO-68-PT (0.1 mg/mL) upon
addition of HClO at different concentrations in the aqueous solution.
and βH returned to their original positions upon addition of
VC.
The emission maximum was observed at 392 nm (λ = 323 nm). (b)
ex
On the basis of the aforementioned observation, UiO-68-PT
could be used as a visual or fluorescent sensor for detecting
HClO in aqueous solution. Considering the low HClO
concentration in the environment, for example, in tap water,
high sensitivity for HClO probe is necessary. For this, the
sensitivity of UiO-68-PT was determined by the emission
spectra. As indicated in Figure 3a, the emission intensity at 392
nm was linearly related to the HClO concentration in a range
from 0 to 80 μM with a linear coefficient up to 0.9947 (Figure
S5, Supporting Information). The limit of detection (LOD)
was 0.28 μM based on LOD = 3 σ/k (where σ = standard
deviation, and k = slope of the linear plot). Such a low
detection limit makes the UiO-68-PT available for detecting
HClO in tap water.
Besides sensitivity, the high selectivity is another essential
feature for the probe. So, the selectivity of UiO-68-PT toward
HClO over other analytes in tap water was examined. As
shown in Figure 3b, the color of aqueous solution containing
UiO-68-PT (0.1 mg/mL, water) did not show any color
Color change of UiO-68-PT (0.1 mg/mL, water) in the presence of
2
+
2+
various analytes (0.1 M), from left to right: blank, Ca , HClO, Cu ,
3
+
2+
+
2+
+
−
2+
2+
Fe , H O , Zn , K , Mg , Na , NO , Fe , Ba . (c) Fluorescence
2
2
2
spectra of probe UiO-68-PT (0.1 mg/mL) to HClO (0.1 M) over
various relevant species (0.1 M).
2+
2+
3+
change upon addition of each analyte, that is, Ca , Cu , Fe ,
2+
+
2+
+
−
2+
2+
H O , Zn , K , Mg , Na , NO , Fe , Ba , which is further
2
2
2
confirmed by the emission spectra. As indicated in Figure 3c,
only HClO could induce the significant fluorescence increase;
no detectable fluorescence changes were observed for other
possible species in water. To our delight, the oxidation process
of UiO-68-PT by HClO is very quick, and the whole oxidation
response time is less than 10 s based on the measured emission
intensity (Figure S6, Supporting Information).
For practical application, the UiO-68-PT-based MMM was
fabricated. The UiO-68-PT-based MMM (20% content) was
readily fabricated by ultrasonically mixing UiO-68-PT (10 mg)
and PVA (40 mg) in aqueous solution (3 mL) for 5 min.
20
D
DOI: 10.1021/acs.inorgchem.9b01032
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Inorganic Chemistry
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2
Figure 4. (a) Different views of the UiO-68-PT-based MMM (1.5 × 3.0 cm ) indicating resilience to mechanical stress. (b) SEM image and
elemental mapping of the UiO-68-PT-based MMM. (c) SEM image of the cross section of MMM. (d) Color change of the UiO-68-PT-based
MMM induced by HClO (5 mg/L) and VC (0.1 M).
Figure 5. (a) Color change of the UiO-68-PT-based MMM immersed in HClO aqueous solution with different concentrations (<3 min). (b) The
linearity between relative intensity and HClO concentration in the range of 0−0.8 mg/L (with the linear coefficient of 0.9801; inset is the test result
in tap water).
Afterward, it was dried on the Teflon mold at 100 °C for 1 h to
afford a stand-alone and elastic membrane with 20 wt % of
UiO-68-PT loading (Figure 4a). As shown in Figure 4b, SEM
image and elemental mapping showed the obtained free-
standing membrane is flat, pliable, and free of macroscopic
defects and that the MOF particles were evenly dispersed in
the membrane. The cross-sectional image indicated that the
membrane is ca. 15 μm in thickness (Figure 4c). In addition,
the membrane surface energy was measured based on the static
contact angles (Figure S7, Supporting Information). The drop
image was obtained from the drop wetting state (both left and
right contact angles) via an image analysis system; meanwhile,
the ultrapure water was used as the test liquid, and all the
measurements were performed at room temperature. The
obtained results showed that the contact angles of PVA and
UiO-68-PT-based MMM are 58.5 ± 2.0° and 63.4 ± 2.0°,
respectively. As expected, the involved MOF particle did not
significantly change the hydrophilicity of PVA, which would be
beneficial to its application in aqueous media.
solution under ambient conditions. Although a series of MOF-
2
1
based MMMs have been reported very recently, the
reversible visual color-changed MOF-MMMs are still un-
22
precedented.
As shown in Figure 5a, the visual color change of the UiO-
68-PT-based MMM could be clearly observed within a HClO
concentration range of 0−5.0 mg/L. Moreover, the relative
intensity and HClO concentration showed a good linearity in a
range of 0−0.8 mg/L (Figure 5b), which covered the HClO
23
concentration requirement in tap water of China. So, the
detection of HClO in tap water was performed. The tap water
sample was collected from Jinan (Shandong, China), and it was
immediately analyzed after sampling without any pretreatment.
After it was immersed in the tap water sample at room
temperature for 3 min, the color of the UiO-68-PT-based
MMM changed, and the HClO content of 0.32 mg/L was
determined based on the intensity−concentration standard
curve (Figure 5b). The H L-PT-based MMM, however, did
2
not show obvious color changes under the same conditions
After it was immersed in HClO solution (5 mg/L), the light
yellow UiO-68-PT-based MMM changed to deep red within 3
min. By addition of VC (0.1 M) at room temperature, the deep
red MMM reverted to light yellow (Figure 4d). The MOF
structure in the MMM was well-preserved during this color-
change process, which was well-supported by the measured
PXRD patterns (Figure S8, Supporting Information). There-
fore, the UiO-68-PT-based MMM herein could be considered
as a reusable colorimetric card for detecting HClO in aqueous
(
Figure S9, Supporting Information).
CONCLUSION
■
In summary, we report the first of its kind, a novel MOF-based
redox-reversible fluorescent probe UiO-68-PT, which was
generated from the phenothiazine-decorated benzimidazole
bridging dicarboxylic acid ligand and Zr(IV) via in situ one-pot
approach. The obtained UiO-68-PT can be a highly sensitive
E
DOI: 10.1021/acs.inorgchem.9b01032
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
and selective probe to detect HClO via both visual and
fluorogenic observation. More importantly, UiO-68-PT-based
MMM was fabricated by mixing MOF with poly(vinyl
alcohol), and the obtained MMM can be used as a naked-
eye colorimetric card to detect the HClO in tap water. We
expect the presented approach to be viable for the fabrication
of many new types of MOF-based materials and shaped
devices for practical applications, especially for the increasing
global environmental issues.
and Elesclomol-Induced HClO in Cancer Cells. J. Am. Chem. Soc.
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ASSOCIATED CONTENT
Supporting Information
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Ferrocene-Based Fluorescent Probe for Hypochlorous Acid and Its
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Eur. J. 2008, 14, 4719−4724.
■
*
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.9b01032.
Materials and instrumentation, synthesis of the com-
(9) (a) Yuan, L.; Lin, W.; Xie, Y.; Chen, B.; Song, J. Fluorescent
Detection of Hypochlorous Acid from Turn-On to FRET-Based
Ratiometry by a HOCl-Mediated Cyclization Reaction. Chem. - Eur. J.
pound H L-PT, N sorption isotherms and pore width
2
2
of UiO-68-PT, UiO-68-PTO, UiO-68-PT′, and
2012, 18, 2700−2706. (b) Xiao, H.; Xin, K.; Dou, H.; Yin, G.; Quan,
MMMs, FTIR spectra, H L-PT/H2L-PTO/H2L-PT′
2
Y.; Wang, R. A fast-responsive mitochondria-targeted fluorescent
probe detecting endogenous hypochlorite in living RAW 264.7 cells
and nude mouse. Chem. Commun. 2015, 51, 1442−1445. (c) Yin, W.;
Zhu, H.; Wang, R. A Sensitive and Selective Fluorescence Probe
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Application for Biological Imaging. Dyes Pigm. 2014, 107, 127−132.
redox reactions process, water contact angles, and PXRD
of PVA and UiO-68-PT-based MMM (PDF)
AUTHOR INFORMATION
Corresponding Authors
E-mail: yananli@sdnu.edu.cn. (Y.-A.L.)
E-mail: yubindong@sdnu.edu.cn. (Y.-B.D.)
■
(
d) Li, J.; Li, P.; Huo, F.; Yin, C.; Liu, T.; Chao, J.; Zhang, Y.
*
−
Ratiometric Fluorescent Probes for ClO and in Vivo Applications.
*
Dyes Pigm. 2016, 130, 209−215.
ORCID
(10) Wybraniec, S.; Starzak, K.; Pietrzkowski, Z. Chlorination of
Yan-An Li: 0000-0003-4972-5101
Qun Guan: 0000-0002-5522-5106
Yu-Bin Dong: 0000-0002-9698-8863
betacyanins in several hypochlorous acid systems. J. Agric. Food Chem.
016, 64, 2865−2874.
11) Mei, J.; Hong, Y.; Lam, J. W. Y.; Qin, A.; Tang, Y.; Tang, B. Z.
2
(
Aggregation-induced emission: the whole is more brilliant than the
Notes
parts. Adv. Mater. 2014, 26, 5429−5479.
The authors declare no competing financial interest.
(12) (a) Hu, Z.; Deibert, B.; Li, J. Luminescent metal−organic
frameworks for chemical sensing and explosive detection. Chem. Soc.
Rev. 2014, 43, 5815−5840. (b) Qiu, S.; Xue, M.; Zhu, G. Metal−
organic framework membranes: from synthesis to separation
application. Chem. Soc. Rev. 2014, 43, 6116−6140. (c) Li, F.-L.;
Shao, Q.; Huang, X.; Lang, J.-P. Nanoscale Trimetallic Metal-Organic
Frameworks Enable Efficient Oxygen Evolution Electrocatalysis.
Angew. Chem., Int. Ed. 2018, 57, 1888−1892. (d) Hu, F.-L.; Mi, Y.;
Zhu, C.; Abrahams, B. F.; Braunstein, P.; Lang, J.-P. Stereoselective
Solid-State Synthesis of Substituted Cyclobutanes Assisted by
Pseudorotaxane-like MOFs. Angew. Chem., Int. Ed. 2018, 57,
12696−12701. (e) Liu, D.; Lang, J.-P.; Abrahams, B. F. Highly
Efficient Separation of a Solid Mixture of Naphthalene and
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ACKNOWLEDGMENTS
We are grateful for financial support from NSFC (Grant Nos.
1671122, 21475078, and 21805172), the Taishan Scholar’s
Construction Project, the Doctoral Fund of Shandong
Province (Grant No. ZR2017BB067), and China Postdoctoral
Science Foundation funded project (Grant No.
■
2
2
017M612328).
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