Cu MOF-based catalytic sensing for formaldehyde

Article abstract of DOI:10.1039/c8tc01703d

Developing a catalyst with a uniform and well-defined crystal structure is very important to establish a catalytic sensing system with high efficiency. In this work, Cu-BTC metal-organic frameworks (MOFs) without a crystalline CuO or Cu₂O phase were successfully synthesized by using a low temperature synthesis method, and the as-prepared Cu-BTC MOFs were found to have outstanding catalytic activity towards the traditional oxidase substrate, o-phenylenediamine (OPD), to generate a colored and fluorescent product. The results of the kinetics analysis revealed that the catalytic behavior of Cu-BTC MOFs towards OPD could well follow the typical Michaelis-Menten equation, indicative of a strong affinity between Cu-BTC MOFs and OPD. On the basis of these findings, taken together the condensation reaction between the -CHO group of formaldehyde and the -NH₂ group of OPD to form Schiff base compounds, a novel Cu-BTC MOF-based catalytic sensing system for detecting gaseous formaldehyde could be successfully established.

Full text of DOI:10.1039/c8tc01703d

View Article Online
View Journal
Journal of
M at erials Chemistry C
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: P. Gao, X. Sun, B.
Liu, H. Lian, X. Liu and J. Shen, J. Mater. Chem. C, 2018, DOI: 10.1039/C8TC01703D.
Volume
4
Number
1
7
January 2016 Pages 1–224
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Journal of
Materials Chemistry C
Materials for optical, magnetic and electronic devices
www.rsc.org/MaterialsC
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 2050-7526
PAPER
~
Nguyên T. K. Thanh, Xiaodi Su et al.
Fine-tuning of gold nanorod dimensions and plasmonic properties using
the Hofmeister effects
rsc.li/materials-c

Please do not adjust margins
Page 1 of 10
Journal of Materials Chemistry C
View Article Online
DOI: 10.1039/C8TC01703D
Journal Name
ARTICLE
Cu MOFs-based catalytic sensing for formaldehyde
a,b
a,b
a,b
a,b
c
a,b
Ping Gao, Xiang-Ying Sun, Bin Liu, Hui-Ting Lian, Xin-Qiang Liu and Jiang-Shan Shen
*
Received 00th January 20xx,
Accepted 00th January 20xx
Developing a catalyst with the uniform and well-defined crystal structure is very important to establish a catalytic sensing
system with high efficiency. In this work, Cu-BTC metal-organic frameworks (MOFs) without crystalline CuO or Cu O phase
2
DOI: 10.1039/x0xx00000x
were successfully synthesized by using a low temperature synthesis method, and the as-prepared Cu-BTC MOFs were
found to have outstanding catalytic activity towards the traditional oxidase substrate, o-phenylenediamine (OPD), to
generate a colored and fluorescent product. The results of kinetic analysis revealed that the catalytic behavior of Cu-BTC
MOFs towards OPD could well follow the typical Michaelis-Menten equation, indicative of a strong affinity between Cu-
BTC MOFs and OPD. On the basis of these findings, taken together the condensation reaction between the -CHO group of
www.rsc.org/
2
formaldehyde and the -NH group of OPD to form Schiff base compounds, a novel Cu-BTC MOFs-based catalytic sensing
system of detecting gaseous formaldehyde could be successfully established.
1
1, 12
pollutants.
However, it should be pointed out that most
Introduction
of these nanomaterials used as artificial enzyme mimics in
the field of bio-/chemosensing were short of uniform and
well-defined crystal structures. Developing artificial enzyme
mimics with well-defined crystal structures are very
important for further understanding their catalytic
mechanisms and establishing the relationship between
catalytic activity and crystal structure, which are also
beneficial to obtain excellent catalysts for establishing highly
sensitive catalytic sensing systems. However, quite a few
works involving in this aspect have been reported at present.
This lack can be considered to result from the difficulty of
preparing these enzyme-like nanomaterials with uniform and
well-defined crystal structures.
Enzymes are very critical for sustaining life operation because
they can accurately manipulate various complex and
functional chemical reactions in life systems. Natural
enzymes not only can act as the catalyst role in life, but also
can be utilized to develop bio-/chemosensing platforms due
to their highly catalytic efficiency. However, most of used
natural enzymes have some shortcomings including complex
and tedious procedures of purification, high cost of
producing, and harsh conditions of storage and usage, which
are unfavourable for their practical applications such as
establishing
bio-/chemosensing
systems.
Therefore,
developing various kinds of artificial enzyme mimics to
replace the natural enzymes is attracting tremendous
attentions in recent years mainly due to the high stability and
Metal-organic frameworks (MOFs), a novel kind of porous
materials, have been widely used in the fields of gas
1
3-17
18
19
1
-3
storage/separation,
2
catalysis,
drug delivery,
and
facilely producing of artificial enzyme mimics. In particular,
some metal/metal oxide/metal sulfide nanomaterials,
0-25
sensing.
Compared with traditional metal/metal
4
5
6
7
8
9
10
oxide/metal sulfide nanomaterials, MOFs can show several
advantages: (i) MOFs with varied and tunable structures can
be synthesized by employing various metal ions and organic
3 4 2 4
including Au, Ag, CeO, Fe O , CoFe O , FeS, and CdS,
were found to have intriguing enzyme-like catalytic activity.
These nanomaterials have been employed to establish a
series of bio-/chemosensing systems and to even catalyse the
decomposition reactions of environmental organic
2
6
linkers as building blocks; (ii) MOFs have uniform and well-
defined crystal structures which can ensure the uniformity of
their pore and channel size, and large surface area, also
resulting in improving the catalytic selectivity; (iii) Most of
MOFs possess highly thermal and mechanical stability which
are beneficial to the repeatable usage, in particular under
a.
College of Materials Science and Engineering, Huaqiao University, Xiamen
3
Key Laboratory of Molecular Designing and Green Conversions (Huaqiao
University), Fujian Province University, Xiamen 361021, China
Department of Environmental Science and Engineering, Tan Kah Kee College,
Xiamen University, Zhangzhou, 363105, China
61021, China.
b.
c.
27
some extremely operation conditions. Therefore, these
advantages can ensure that MOFs should be ideal catalysts
which are useful for establishing excellent catalytic sensing
systems. However, hitherto the established catalytic sensing
systems involving in MOFs used as the catalysts are fairly
*
†
Corresponding authors. E-mail: jsshen@hqu.edu.cn
Electronic Supplementary Informaꢀon (ESI) available: Fig S1-S7 and Table
S1.CCDC reference number 1854611. For ESI and crystallographic data in CIF see
DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 2 of 10
View Article Online
DOI: 10.1039/C8TC01703D
ARTICLE
Journal Name
2
8-30
2
scarce.
The reasons for this shortage likely include: (i) for
m /g, which is indicative of its good porous structure. It was
found that Cu-BTC MOFs have the outstanding catalytic
activity towards the traditional enzyme substrate OPD which
could be catalysed to generate a fluorescent species.
Considering the condensation reaction of forming Schiff base
compounds between the –CHO group of formaldehyde and
limited kinds of metal ions which have excellent catalytic
activity towards the traditional substrates to trigger the
fluorogenic or chromogenic reactions, it is not easy to obtain
their corresponding MOFs which have single crystal
structures with high quality. It should be noted that some
reported works of catalytic sensing involving in MOFs are lack
2
the –NH group of OPD, a catalytic sensing platform for
3
1-33
of the detailed characterization of crystal structures;
(ii)
detecting gaseous formaldehyde was expected to be well
established (Scheme 1). When a certain amount of gaseous
formaldehyde was introduced into the solution containing
OPD and the as-prepared Cu-BTC MOFs, the catalytic
fluorogenic reaction was found to be gradually suppressed,
due to the condensation reaction between formaldehyde and
although some metal ions have excellent catalytic activity
towards these substrate molecules, the catalytic activity of
their corresponding MOFs are greatly lowered or even
disappear, due to the strong binding between metal ions and
3
4
ligands. Therefore, looking for one kind of metal ions with
excellent catalytic activity to prepare the corresponding
MOFs which can retain their partially or largely catalytic
activity, is the prerequisite for establishing highly sensitive
MOFs-based catalytic sensing systems. In 2016, our group
2 2
OPD. However other tested common gases like N , CO , and
air did not produce observable effects on this catalytic
reaction. Therefore, a novel, sensitive and selective catalytic
sensing system of detecting gaseous formaldehyde could be
successfully established.
2
+
found that Cu ions have extremely highly catalytic activity
towards the oxidation reaction of o-phenylenediamine (OPD)
which is a traditional enzyme substrate molecule to generate
3
5
Experimental section
a fluorescent compound. Therefore, we considered that
2
whether Cu ions can serve as the good candidate to prepare
MOFs capable of retaining partially or largely its original
+
Materials and instruments
Materials. KCl (99.5%, AR), methanol (99.5%, AR), ethanol
2
+
catalytic activity. If Cu -based MOFs possessing good
catalytic activity for the fluorogenic reactions could be
successfully prepared, it could not only offer an opportunity
to establish novel highly sensitive MOFs-based catalytic
sensing systems, but also lead to structural diversity of
catalysts compared with that of metal ions.
(
99.7%, AR), glacial acetic acid (99.5%, AR), N,N-
Dimethylformamide (99.5%, AR), hydrochloric acid (36-38%,
AR), acetonitrile (99%, AR), dichloromethane (99.5%, AR), and
tris(hydroxymethyl)aminomethane (Tris, 99%, BR) were
purchased from GuoYao (Shanghai, China). 1,3,5-benzene
3
tricarboxylic acid (H BTC) (98%), 3,3’,5,5’-tetramethyl
benzidine (TMB, 99%), and p-acetamidophenol (99%, AR)
were purchased from Aladdin (Shanghai, China). Copper
nitrate trihydrate (99%, AR) was obtained from Xiya Reagent
(Shandong, China). Nafion solution (5%) was obtained from
Sigma-Aldrich (Darmstadt, Germany). OPD (99.5%) was
obtained from Macklin (Shanghai, China). Standard gases of
2 2
CO , N , air and formaldehyde (100 ppm) were purchased
from Putian Tongchuang Biotechnology Co. Ltd. (Beijing,
China). Ultrapure water were purified by a Milli-Q system.
Instruments. Photoluminescence (PL) spectra were
recorded with
a FS5 fluorescence spectrophotometer
(Edinburgh, UK). UV-vis absorption (UV) spectra were
recorded with a UV-2600 spectrophotometer (Shimadzu,
Japan). PXRD experiments were performed by using a
Rigaku/SmartLa analyzer with Cu Kα radiation (λ= 1.5406 Å)
with the 2θ range from 5° to 60°. SCXRD data were collected
by using a Gemini ECCD diffractometer with Mo Kα (λ =
Scheme 1. The draft illumination of the catalytic sensing mechanism in this work.
Therefore, in this work, by employing 1,3,5-benzene
2
+
3
tricarboxylic acid (H BTC) and Cu ions as the building blocks,
Cu-BTC MOFs could be successfully prepared by using a low
temperature synthesis method . The data of single crystal X-
ray crystallographic diffraction (SCXRD) revealed that the as-
prepared Cu-BTC MOFs adopt a cubic structure, and powder
X-ray powder diffraction (PXRD) experiments indicated that
0.71073 Å) (Aglient Technologies, Poland Sp.ZO.O). X-ray
photoelectron spectroscopy (XPS) experiments were
conducted by using an EscaLab 250Xi X-ray photoelectron
spectrometer with the excitation of an Al Kα X-ray radiation
source at 1486.6 eV (Thermo Scientific, USA). Fourier
transform infrared (FT-IR) spectra were recorded with a
Nicolet iS 50 instrument (Thermo Scientific, USA). The
experiments of electrospray ionization mass spectrometry
2
no CuO or Cu O phase could be observed in the as-prepared
Cu-BTC MOFs, different from that of Cu-BTC MOFs prepared
o
under high temperature of above 100 C. The surface area of
the as-prepared Cu-BTC MOFs was estimated to 1554.835
(ESI-MS) were performed on an infinity ultrahigh pressure
2
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 3 of 10
View Article Online
DOI: 10.1039/C8TC01703D
Journal Name
ARTICLE
liquid chromatography (UHPLC) system with a quadrupole
time-of-flight (Q-TOF) mass spectrometer (Agilent
Technologies, USA). Nuclear magnetic resonance (NMR)
experiments were conducted with a 500 MHz/AVANCE III
system (Bruker, Switzerland). Cyclic voltammetry curves
were obtained on a CHI760E electrochemical workstation
30%. The error bars could be obtained by measuring three
parallel solutions.
Kinetic analysis of the catalytic activity of the as-prepared
Cu-BTC MOFs towards OPD as the substrate was carried out
by varying OPD concentration, such as 0.004, 0.01, 0.02, 0.04,
0.08, 0.14 and 0.20 mM. According to Michaelis-Menten
equation, V = Vmax × [S]/(K + [S]), which is derived at the
m
(Shanghai Chenhua Instrument Co., Ltd, China).
condition assuming in the presence of a steady-state reaction
conditions, we could calculate the apparent kinetic
Scanning electronic microscopy (SEM) experiments were
performed with a Hitachi S-3500N system (Japan). Brunauer-
Emmett-Teller (BET) test was conducted with an Autosorb-iQ
automatic surface area and pore size distribution analyzer
m
parameters. In this equation, V is the initial velocity, K is
called as the Michaelis constant, Vmax is the reaction velocity
when the catalyst is saturated with the substrate, and [S] is
the substrate concentration. The initial catalytic velocity was
calculated from the initial slopes of curves of PL intensity at
(
Quantachrome Instruments, USA). Thermal gravimetric
analysis (TGA) and differential thermal analysis (DTA) curves
were measured with DTG-60H thermos-gravimetric-
a
564 nm wavelength vs time. The reaction velocity was
analyzer (Shimadzu, Japan).
measured in 50 mM Tris-HCl buffer solution of pH 7.4
-1
containing 15% acetonitrile, 0.67 mg·mL Cu-BTC MOFs and
o
varied OPD concentration at 60 C. The error bars could be
Experimental procedures
Synthesis of Cu-BTC MOFs. After a sires of optimized
obtained by measuring three parallel solutions.
experiments were conducted, a low temperature synthesis
Electrochemical measurements. A typical three electrode
system was employed. The working electrode was a modified
glassy carbon electrode with a diameter of 3 mm, the
reference electrode was an Ag/AgCl electrode, and counter
electrode was platinum wire electrode. First, the bare glassy
carbon electrode was polished by using the polishing powder
with the size of 1.0, 0.3, and 0.05 μm, in turn, and then was
sequentially put in ethanol and water for ultrasonic washing
of 3 min. Cyclic voltammogram (CV) experiment of OPD was
recorded in 50 mM Tris-HCl buffer solution of pH 7.4
containing 15% acetonitrile, 1% KCl and 50 mM OPD. Before
the measurement, the buffer solution was bubbled with
nitrogen gas for 30 min for removing the dissolved oxygen.
The applied potential was ranged from -1.5 to 1.2 V, and the
method was chosen to prepare Cu
3
(BTC)
O was dissolved in 6 mL water-
DMF mixed solvent of 1:1 (v/v) , and 0.24 g H BTC was
dissolved in 3 mL ethanol. Then, Cu(NO solution and 12 mL
2
MOFs, the single
3
6
3 2 2
crystals. 0.49 g Cu(NO ) ·3H
3
3 2
)
glacial acetic acid were added to H3BTC solution. The
resulting solution was then sealed in a small glass vial and
o
placed in a heating oven at 55 C for 3 days. After the
solution was naturally cooled to room temperature, the blue
Cu-BTC MOF crystals appeared on the inner wall of the glass
vial. All crystals were collected, and carefully washed by
ethanol for three times, for solvent exchange. Then, all
o
crystals were dried in vacuum at 60 C for 2 h, and stored in a
common dyer for further experiments.
-1
scan rate was set to 50 mV·s . CV and differential pulse
voltammetry (DPV) of the as-prepared Cu-BTC MOFs were
also conducted. First, 5 mg ground powder of the as-
prepared Cu-BTC MOFs was weighted and added into 0.8 mL
water-isopropanol mixed solution(v/v = 3:1). Then, 20 μL 5%
Nafion solution was added to the above solution, and the
mixed solution was put in an ultrasonic cleaner by ultrasound
for 10 min to obtain a homogeneous ink. 10 μL ink was
dropped into the working electrode to form a uniform film
after the electrode was dried. 50 mM Tris-HCl buffer solution
of pH 7.4 containing 15% acetonitrile was employed as the
electrolyte after the solution was bubbled with nitrogen gas
for 30 min for removing the dissolved oxygen. For CV
scanning, the potential was changed from -0.4 to 0.4 V, and
The catalytic activity of the as-prepared Cu-BTC MOFs.
In order to investigate the catalytic activity of the as-
prepared Cu-BTC MOFs, PL spectrum of the oxidation product
of OPD catalysed by Cu-BTC MOFs in 50 mM Tris-HCl buffer
solution of pH 7.4 was monitored by a FS5 fluorescence
spectrophotometer with the excitation wavelength of 415
nm. For
a typical catalytic reaction experiment, the
experimental procedure was followed: 300 μL 0.8 mM OPD
solution and 2.0 mg Cu-BTC MOFs were added into 2.7 mL 50
mM Tris-HCl buffer solution of pH 7.4 containing 15%
acetonitrile (by volume). Then, the reaction solution was
o
heated in water bath at 60 C for 35 min. PL spectrum was
immediately recorded, after the solution was quickly cooled
to the room temperature. For the experiments of the effect
of experimental parameters on this catalytic reaction, only
the checked experimental parameter was changed yet other
parameters were fixed to be same in this tested group. For
the checked experimental parameters, the reaction time was
changed from 0 min to 35 min, pH was adjusted from 4.2 to
-1
the scan rate was set to 50 mV·s . For DPV scanning, the
potential was ranged from 0.4 to -0.4 V, and the scan rate
-1
was set to 50 mV·s .
Repeatability experiments of Cu-BTC MOFs. To investigate
the reusability and catalytic stability of the as-prepared Cu-
BTC MOFs towards OPD, the experiments of cycling catalytic
oxidation reaction were performed. The detailed
experimental procedure as the follow: 300 μL 0.8 mM OPD
o
o
1
0.2, temperature was set from 30 C to 80 C, OPD
concentration was ranged from 4 μM to 0.2 mM, Cu-BTC
-1
MOFs concentration was altered from 0.23 mg·mL to 1.0
-1
mg·mL , and the content of acetonitrile was varied from 0 to
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 4 of 10
View Article Online
DOI: 10.1039/C8TC01703D
ARTICLE
Journal Name
solution and 2.0 mg Cu-BTC MOFs were added into 2.7 mL 50
mM Tris-HCl buffer solution of pH 7.4 containing 15%
acetonitrile, and the mixed solution was placed into
respectively, indicated that the building units direct to form a
symmetrical three-dimensional framework. The water and
ethanol molecules were found in the channel as guest
molecules to stabilize the porous structure. The crystal data
were deposited in Table S1 (referring to CCDC No. CCDC
reference number 1854611, which has been supplemented at
Cambridge Crystallographic Data Centre). The results of PXRD
experiments were shown in Fig. 2. The XRD pattern of Cu-BTC
o
water bath at 60 C for 35 min, and then PL spectrum was
measured by using the excitation wavelength of 415 nm.
After the measurement of PL spectrum was completed, the
reaction solution was filtered to recover solid crystals. The
collected crystals were carefully washed by ethanol for three
3
6
o
MOFs can well match that of the previous report. It should
be pointed out that, Cu-BTC MOFs synthesized by this
method is somewhat different from those synthesized by the
conventional hydrothermal synthesis method under high
temperature, and the temperature used in other reported
times, and then placed in a vacuum dryer at 60 C for 2 h. The
resulting solid crystals were reused in next cycle of the
catalytic reaction of OPD under the same experimental
conditions. The experiment of the catalytic reaction of OPD
was cycled for 5 times.
o
37
case was higher than 55 C used in this work. The XRD
reflection peaks of CuO (2θ = 35.5° and 38.7°) or Cu O (2θ =
Detection of gaseous formaldehyde. For detecting gaseous
formaldehyde by using the fluorogenic reaction of OPD
catalysed by the as-prepared Cu-BTC MOFs, the experimental
procedure was followed: The flow rate of standard
2
36.43°) can’t be observed in the as-prepared Cu-BTC MOFs in
this work yet appeared in the reported case which used the
hydrothermal synthesis method under high temperature of
-1
o
38
formaldehyde gas was fixed as 40 mL·min , and a series of
exposure times, such as 0 s, 5 s, 15 s, 30 s, 1 min, 2 min, 4
min, 6 min, 8 min, 10 min and 15 min, were tested. After 100
ppm standard formaldehyde gas was flowed to 5 mL 8 mM
oxygen-free OPD solution with various exposure times, the
over 100 C (inset of Fig. 2). Therefore, it can be believed
that the reaction temperature has an important effect on
2
whether forming CuO or Cu O phase in Cu-BTC MOFs.
resulting solution was sealed and heated in a water bath at
o
0 C for 30 min. Then, 2 mg Cu-BTC MOFs were added into
5
30 μL above reaction solution which was mixed with a certain
volume of 50 mM Tris-HCl buffer solution of pH 7.4
containing 15% acetonitrile, resulting in a total volume of 3
mL. After that, the mixed solution was sealed and heated in a
o
water bath at 60 C for 35 min. Then, the PL spectrum of the
catalytic reaction solution was measured by
a FS5
fluorescence spectrophotometer with an excitation
wavelength of 415 nm. The error bars could be obtained by
measuring three parallel solutions.
2
+
Results and discussion
Fig. 1 Schematic view of the coordination environment of (a) Cu and views inside of
the structure of the as-prepared Cu-BTC MOFs from the [100] (b) and [111] (c) axis
direction.
In this work, Cu-BTC MOFs were prepared by using a low
temperature synthesis method. The SEM and optical
microscope images of the as-prepared Cu-BTC MOFs were
shown in Fig. S1a-d. The cubic geometry structure of blue Cu-
BTC MOFs could be observed, and the average diameter was
estimated to ca. 600 μm. SCXRD experiments can further
confirm that the as-prepared Cu-BTC MOFs adopt the cubic
structure. The diffraction peaks were refined by using the
space group Fm-3m, affording the lattice parameters of a =
1
2
3
4
3
2
36
degree
40
2θ
/
1
2
26.3805(3) Å, b = 26.3805(3) Å, c = 26.3805(3) Å, and α, β, γ =
9
0°. As shown in Fig. 1a, the minimum repeating unit
2
+
3
4
3
contains three Cu and two deprotonated H BTC ligands.
2
+
Every Cu can coordinate with four carboxylate groups,
resulting in forming a square structure in the bottom
position, and one oxygen atom can fill on the top position to
offer a paddle wheel-like secondary building unit. The
1
0
20
30
40
50
2
θ
/
degree
2
+
Fig. 2 PXRD patterns of the simulated (1), as-prepared (2), reused (3), and after
distance between two neighboring Cu is 2.634 Å. The inside
views of the structure of Cu-BTC MOFs from both [100] (b)
and [111] (c) axis directions were shown in Fig. 1b and Fig. 1c,
o
o
sensing tested (4) Cu-BTC MOFs. Inset: local enlarged view of PXRD from 30 to 42 .
4
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 5 of 10
View Article Online
DOI: 10.1039/C8TC01703D
Journal Name
FT-IR spectrum of the as-prepared Cu-BTC MOFs reveals
ARTICLE
2 2 4
and 288.82 eV (Fig. 4), resulting from Cu (O CR) . The binding
-1
that, the peak of 488 cm can be ascribed to the stretching
energy of O1s is 532.06 eV, originating from the lattice
2-
oxygen O . The peaks with the binding energies of 935.09 eV
-1
-1
vibration of Cu-O bond, and 1371 cm and 1450 cm can be
attributed to the stretching vibration of C-O in the
carboxylate group and the bending vibration of O-H,
and 954.89 eV can be assigned to Cu2p3/2 and Cu2p1/2
,
respectively. The peaks of the binding energies of 940.47,
944.59 eV and 963.15 eV belong to the satellite peaks of
-1
respectively (Fig. 3a). The peak of 1639 cm can be assigned
to the stretching vibration of C=O, different from the peak of
2
+
Cu2p3/2 and Cu2p1/2, indicative of predominant Cu form in
-
1
43
the catalyst. This observation reveals that no crystalline
1
720 cm in H
3
BTC, likely because that the oxygen atom in
2
the carboxyl group could coordinate with Cu , resulting in a
+
2
Cu O exists in Cu-BTC MOFs, also supportive of obtaining Cu-
3
9
red shift.
Considering the porous structure of Cu-BTC
BTC MOFs without crystalline Cu
temperature synthesis method.
2
O phase by using this low
MOFs, the surface area was measured. Before the N
2
adsorption isotherm was measured, 27.3 mg Cu-BTC MOFs
o
was dried at 40 C by vacuum for overnight. BET surface area
Binding energy / eV
1200 530
0
400
800
535
540
0
was calculated by taking the p/p range from 0.05 to 0.2 of
(a)
(b)
O 1s
the isotherm. The surface area was estimated to 1554.835
2
m /g (Fig. 3c), which is higher than those of Cu-based MOFs
Cu2p
O1s
4
0-42
synthesized by other ways,
and pore size distribution of
C1s
Cu-BTC MOFs was shown in Fig. 3d, supportive of its good
porous structure.
(c)
C 1s (d)
Cu 2p
0
C-C
36.139%
Cu 2p3/2
(a)
100
(b)
1
2
Cu 2p1/2
-
10
-20
30
8
6
4
0
0
0
-COO
3
24.177%
200
-
280
284
288
292
930
940
950
960
Binding energy / eV
4
000
3000
2000
1000
0
400
o
600
-1
Wavenumber / cm
Temp ( C)
Fig. 4 XPS spectra of the as-prepared Cu-BTC MOFs: (a) the total spectrum, (b) O 1s
adsorption
desorption
4
4
4
80
(c)
(d)
spectrum, (c) C 1s spectrum and (d) Cu 2p spectrum.
0
0
0
.010
.005
.000
60
40
p
TMB
OPD
-acetamidophenol
6
00000
0
0
0
0
0
.8
.6
.4
.2
.0
(a)
(b)
(c)
450000
300000
150000
0
0
.0 0.2 0.4 0.6 0.8 1.0
5
10 15 20 25 30
p / p0
Pore size diameter / nm
Fig. 3 (a) FT-IR spectra of reused (1), as-prepared (2) Cu-BTC MOFs, and ligand H
3). TGA (red) and DTG (blue) curves (b), N adsorption-desorption isotherm (c) and
pore size distribution (d) of the as-prepared Cu-BTC MOFs.
3
BTC
(
2
4
00
500
600
700
Wavelength / nm
To probe the thermal stability of the as-prepared Cu-BTC
o
MOFs, TGA with heating rate of 5 C per min was used. As
Fig. 5 PL spectra of OPD (red line, λex=415 nm) and p-acetamidophenol (blue
line, λex=330 nm), and UV-vis absorption spectrum of TMB (black line) catalysed
by the as-prepared Cu-BTC MOFs (a). Typical PL photographs of OPD catalysed
by the as-prepared Cu-BTC MOFs (b), and of original OPD without catalysis (c),
illuminated by 365 nm UV lamp in dark room. Experimental conditions: OPD, p-
acetamidophenol and TMB concentrations were set to 0.08 mM, respectively;
shown in Fig. 3b, Cu-BTC MOFs have two weightless intervals.
First, Cu-BTC MOFs lost water and ethanol guest molecules
from the pores with a weight loss of 36.14% when
o
o
temperature was enhanced from 50 C to 200 C. Then, a
o
o
o
platform appeared from 200 C to 325 C, indicated that the
framework could maintain a stable state in this temperature
range. When the temperature was increased to be higher
the temperature was 60 C; Cu-BTC MOFs concentration was set to 0.67
-
mg·mL ; the reaction time was 35 min; 50 mM Tris-HCl buffer solution of pH
1
7
.4 containing 15% acetonitrile content was used.
o
than 325 C, the crystal structure would collapse, resulting in
The catalytic activity of the as-prepared Cu-BTC MOFs was
a sharp drop of the weight with loss ratio of ca. 24.18%.
investigated by employing OPD as the substrate. When 50
mM Tris-HCl buffer solution of pH 7.4 containing 15%
These observations can support that Cu-BTC MOFs have good
o
thermal stability below 325 C. It is beneficial to develop a
-1
acetonitrile, 0.67 mg.mL Cu-BTC MOFs, and 0.08 mM OPD
o
was heated in the water bath at 60 C for 35 min, the
thermal stable catalyst in the field of catalytic sensing.
The experiments of XPS and energy dispersive spectrum
resulting solution was found to become yellow color and emit
yellow light under the irradiation of 365 nm UV lamp, yet its
origin solution was non-fluorescent and colorless (Fig. 5b-c).
The PL spectrum was recorded with maximum emission peak
at 564 nm by using the excitation wavelength of 415 nm (Fig.
(
EDS) were employed to evaluate the chemical components
of the as-prepared Cu-BTC MOFs. EDS result reveals that Cu
element exists in Cu-BTC MOFs, and its content was 7.47%
(Fig. S2). The XPS peak of C1s can be observed at 285.07 eV
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 6 of 10
View Article Online
DOI: 10.1039/C8TC01703D
ARTICLE
Journal Name
-
·mL ;
1
min. Experimental conditions: Cu-BTC MOFs concentration was 0.67 mg
5a). This result reveals that the as-prepared Cu-BTC MOFs
[
OPD] = 0.08 mM; 50 mM Tris-HCl buffer solution of pH 7.4 containing 15%
likely possess outstanding catalytic activity towards OPD and
the catalytic reaction can generate a fluorescent product. To
further confirm the role of Cu-BTC MOFs, the experiments of
removing dissolved oxygen and with or without the
illumination of light were conducted. When dissolved oxygen
acetonitrile content was used.
pH
[OPD] / mM
4
5
6
7
8
9
10
0.00 0.05 0.10 0.15 0.20
4
2
0000
0000
0
40000
20000
0
(
a)
(b)
in the buffer solution was largely removed by bubbling N
2
for
30 min or Cu-BTC MOFs were not added into the buffer
solution, the PL intensity was found to be greatly lowered or
even disappear, that means, the reaction could be greatly
suppressed or even not occur (Fig. S3). Similarly, it was found
that the illumination of room light has not significant effect
on the fluorogenic reaction, indicated that the catalytic effect
of light on this reaction could be excluded for the observable
fluorogenic reaction (Fig. S3). Therefore, it could be deduced
that the dissolved oxygen is the oxidant and Cu-BTC MOFs are
the catalysts in this fluorogenic reaction. The electrochemical
experiments were also employed to further support the
catalyst role of Cu-BTC MOFs. Theoretically, if Cu-BTC MOFs
can directly oxidize OPD, the Gibbs free energy of this
assumed redox reaction should have a negative value.
According to the CV curves of Cu-BTC MOFs and OPD, the
(c)
(d)
3
2
0000
0000
30000
20000
0.2 0.4 0.6 0.8 11.0
0
5
10 15 20 25 30
Content of acetonitrile / %
-
[Cu-MOF] / mg⋅mL
Fig. 7 pH-dependent change of the catalytic activity of the as-prepared Cu-BTC MOFs
towards OPD (a). The relationships between the PL intensity at 564 nm wavelength
and OPD concentration (b), Cu-BTC MOFs concentration (c), and the content of
acetonitrile (d), respectively. Experimental conditions: Cu-BTC MOFs concentration
-
1
was 0.67 mg·mL (a, b, and d); [OPD] = 0.08 mM (a, c, and d); the reaction
o
temperature was 60 C (a-d); the reaction time was 35 min (a-d); 50 mM Tris-HCl
half-wave potential (φ
h
) of the cathodic peak of Cu-BTC MOFs
) of the anodic peak of OPD
buffer solution of pH 7.4 (b-d) was used; the acetonitrile content was 15% (a-c).
and the half-wave potential (φ
h
could be estimated to 0.055 V and 0.368 V, respectively (Fig.
S4-S5). Therefore, the difference between the two potentials
To further probe the catalytic reaction of the as-prepared
Cu-BTC MOFs towards OPD, the effects of temperature, pH,
OPD concentration, Cu-BTC MOFs concentration, acetonitrile
content and reaction time on this catalytic fluorogenic
reaction were detailedly investigated. When the temperature
(
h
Δφ ) was calculated to be -0.313 V, and the Gibbs free
-1
energy ΔG could be further calculated to 30.199 kJ·mol ,
according to the equation of ΔG = -nΔφF. Because the
calculated value of the Gibbs free energy is positive value, it
could be concluded that Cu-BTC MOFs did not directly oxidize
OPD. This result could substantially support the catalyst role
of Cu-BTC MOFs. In order to fully study the catalytic
performance of Cu-BTC MOFs, other traditional enzyme
substrates like TMB and p- acetamidophenol were chosen as
the substrates in this catalytic fluorogenic reaction,
respectively, to check whether Cu-BTC MOFs can catalyse
their oxidation reaction. However, no colored or fluorescent
product could be observed (Fig. 5a). Therefore, the as-
prepared Cu-BTC MOFs can be considered to have high
catalytic selectivity towards OPD as the substrate.
o
o
was enhanced from 40 C to 80 C, the catalytic activity was
generally increased and showed a platform after the
o
temperature was extended up to 60 C (Fig. 6b). The reaction
time effects on the catalytic reaction under various tested
reaction temperatures were found to have an increase
tendency on the PL intensity at 564 nm wavelength with
increasing the reaction time from 0 to 35 min (Fig. 6a). For 70
o
o
C and 80 C, when the reaction time was increased up to 20
min, the catalytic reaction nearly reached a platform. The
experimental results of pH effect reveals that, when pH was
changed from 4.2 to 10.2, the catalytic activity first increased
and then decreased (Fig. 7a). With increasing OPD
concentration from 4 μM to 0.2 mM, the PL intensity at 564
nm wavelength was found to gradually increase and reach a
platform when OPD concentration was set to be higher than
0.08 mM (Fig. 7b). For Cu-BTC MOFs concentration effect, it
was found that the tendency of the PL intensity at 564 nm
wavelength first increased and then decreased with
o
4
5
0
0
C
C
(a)
(b)
o
40000
30000
20000
10000
0
40000
30000
20000
10000
0
o
o
o
6
7
0
0
C
C
C
80
-1
increasing Cu-BTC MOFs concentration from 0.23 mg·mL to
-
1
1
.0 mg·mL (Fig. 7c). Considering that acetonitrile can
2
+
35
promote the catalytic activity of Cu ions, the effect of
acetonitrile content on the catalytic reaction of Cu-BTC MOFs
towards OPD was also investigated. With increasing
acetonitrile content from 0 to 30%, the catalytic activity was
found to be first enhanced and then have a platform (Fig. 7d).
Therefore, after the experiments of the effects of
experimental parameters were performed, 50 mM Tris-HCl
0
10
20
30
45
60
75
o
C
Time / min
Temperature /
Fig. 6 (a) Time-dependent change of PL intensity at 564 nm wavelength of the
catalytic reaction of the as-prepared Cu-BTC MOFs towards OPD under various
reaction temperatures. (b) The relationship between PL intensity at 564 nm
wavelength and the reaction temperature when the reaction time was chosen as 35
6
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 7 of 10
View Article Online
DOI: 10.1039/C8TC01703D
Journal Name
ARTICLE
buffer solution of pH 7.4 containing 15% acetonitrile, 0.67
conditions the as-prepared Cu-BTC MOFs could be repeatedly
used at least 5 times to catalyse the fluorogenic reaction of
OPD, without significantly decreasing its original catalytic
activity (Fig. 9). Furthermore, the XRD peaks of the reused
Cu-BTC MOFs after the cycle of 5 times was found to be
identical to those of the as-prepared Cu-BTC MOFs (Fig.2),
and IR result of the reused Cu-BTC MOFs is similar to that of
the as-prepared Cu-BTC MOFs (Fig. 3a). These observations
indicate that after the cycle experiments the component and
valence state of Cu-BTC MOFs did not significantly change,
which also confirm the catalyst role of the as-prepared Cu-
BTC MOFs. Therefore, the as-prepared Cu-BTC MOFs could be
viewed as the excellent potential catalysts for establishing
repeatable sensing platforms, which is expected to be able to
overcome the shortcoming of uncyclable usage in the case of
-1
mg.mL Cu-BTC MOFs, and 0.08 mM OPD, the reaction
o
temperature of 60 C and the reaction time of 35 min were
chosen for further experiments.
On the basis of these above experimental results, the
investigation on the reaction kinetics of the as-prepared Cu-
BTC MOFs towards OPD as the substrate was further
conducted. The initial rate method was employed to measure
the apparent steady-state kinetic parameters of this catalytic
4
4
reaction. As shown in Fig. 8a, the catalytic reaction of Cu-
BTC MOFs towards OPD could follow the traditional
Michaelis-Menten equation. Furthermore,
reciprocal curve was obtained with a good linear relationship
Fig. 8b). Vmax and K were calculated by using the double-
reciprocal curve (Table 1). Obviously, the small K value of
a
double-
(
m
m
2
+
35
this catalytic system indicated that the affinity between OPD
and Cu-BTC MOFs was stronger than that of other catalyst
Cu ions as the catalyst.
4
systems such as HRP, MnO
5
45
2
,
3 4 3 4
Ag PO and Ag@Ag PO
4
6
microcubes (MCs) when OPD was used as the substrate.
Furthermore, the maximum reaction velocity could reach the
100
8
6
4
0
0
0
2
level of those of HRP and MnO . These results can also
further support that Cu-BTC MOFs did play the catalyst role in
this fluorogenic reaction.
25
20
15
10
5
0
0
.8
(
a)
(b)
20
0
0.6
1st
2nd
3rd
4th
5th
Number of cycles
0.4
Fig. 9 Repeatability tests of 5 cycles on the catalytic fluorogenic reaction of the as-
prepared Cu-BTC MOFs towards OPD as the substrate.
0.2
0.0
0.0
0.1
cOPD / mM
0.2
0
100
1/cOPD / mM
200-1
300
Fig. 8 Steady-state kinetic analysis of the fluorogenic reaction of OPD catalysed
by Cu-BTC MOFs on the basis of the Michaelis–Menten equation (a), and its
double-reciprocal plot (b).
Table 1. Comparison of apparent kinetic parameters of the as-prepared Cu-BTC MOFs
in this work and other reported catalysts.
Substr
ate
-1
Catalyst
HRP
K
m
(mM)
V
max (M·s )
Ref.
45
-8
-8
-6
-6
-8
OPD
OPD
OPD
OPD
OPD
0.59
0.31
3.31
1.23
4.65×10
45
MnO
2
8.21×10
2.77×10
5.18×10
1.53×10
46
Ag
3
4
PO MCs
46
Ag@Ag
3 4
PO MCs
Fig. 10 ESI-MS result of the purified oxidation product of OPD catalysed by the
Cu-BTC MOFs
0.0567
This work
as-prepared Cu-BTC MOFs. The main peak of m/z of 211.0980 can be ascribed
+
to 2,3-diaminophenazine ([M + H] , calcd. m/z is 211.0978 ). The raw product
was extracted from the reaction aqueous solution by using CH
organic solvent was removed by using rotary evaporation. Then, the product
was put in vacuum freeze-drying equipment for overnight. Finally, the
purified product was obtained for performing ESI-MS experiment.
2 2
Cl , and the
Considering that the reusability is one of advantage of
MOFs, repeating the usage of the as-prepared Cu-BTC MOFs
in the catalytic fluorogenic reaction of OPD was further
investigated. It was found that under the tested experimental
a
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 8 of 10
View Article Online
DOI: 10.1039/C8TC01703D
ARTICLE
To further study the fluorogenic reaction of OPD
Journal Name
between formaldehyde and OPD could occur, that is, with
increasing formaldehyde it would generate the products
containing one –C=N– or even two –C=N– bonds in the same
catalysed by the as-prepared Cu-BTC MOFs, the product of
1
this catalytic reaction was probed by using ESI-MS and H
NMR. After the purification procedure was performed, the
experimental result of ESI-MS of the product reveals that the
recorded m/z peak value of 211.0978 can be assigned to 2,3-
2
OPD molecule due to OPD bearing two –NH groups. Two
linear relationships between the PL intensity at 564 nm
wavelength and the exposure time of formaldehyde could
also be obtained from the PL response curves of
formaldehyde (Fig. 12b). The limit of detection (LOD) of
gaseous formaldehyde could be calculated to 0.358 s (3s/k, n
= 9, in which k is the slope of the relationship curve in the
exposure time ranging from 0 to 60 s).
1
diaminophenazine (Fig. 10). The result of H NMR can further
confirm this main product (Fig. 11). Therefore, these results
can well support our proposed catalytic mechanism (Scheme
1).
To transform the exposure time of formaldehyde into
formaldehyde concentration (ppm), the following equation
4
7
(1) could be used,
8
6
4
2
0000
0000
0000
0000
0
70000
Exposure time / s
0
(a)
(b)
Y=66149.9-283.7X
2
R =0.936
9
00s
60000
50000
Y=52617.41-4.62X
1
2
Fig. 11 H NMR result (500 MHz, DMSO-d
fluorogenic reaction of OPD catalysed by Cu-BTC MOFs.
.56-7.54 ppm (m, 2H), 6.91 ppm (s, 2H), 6.26 ppm (s, 4H). The marked “*” peaks
6
) of the purified oxidation product of the
R =0.991
δ
7.90-7.88 ppm (m, 2H),
40000
5
00
600
700
0
200 400 600 800
Exposure time / s
7
Wavelength / nm
are unknown peaks. The purification of product was the same as the above
mentioned procedure.
Fig. 12 The effect of exposure time of gaseous formaldehyde on the PL spectra of
OPD solution catalysed by the as-prepared Cu-BTC MOFs (a) and the relationship
between PL intensity at 564 nm wavelength and the exposure time of formaldehyde
Formaldehyde gas, generally released from various
artificial boards in home, office and public buildings, is
considered as a highly dangerous indoor pollutant. Taking
into account that the –CHO group of formaldehyde can easily
react with the -NH2 group of OPD to form Schiff base
compounds, a detection method of gaseous formaldehyde
based on the catalytic fluorogenic reaction of Cu-BTC MOFs
towards OPD as the substrate is thus expected to be
developed. When the buffer solution containing OPD was
bubbled with a certain amount of formaldehyde gas, the
catalytic reaction in the presence of Cu-BTC MOFs was found
to be suppressed. To detailedly study the feasibility of
sensing gaseous formaldehyde, the flow rate of
(
b). The error bars represent the standard deviation of three measurements.
νtV1C
C = w V0V2
0
…… (1)
where C is formaldehyde concentration (ppm), ν is the flow
-1
rate of formaldehyde gas (mL·min ), t is exposure time of
formaldehyde gas (s), and V is the volume of OPD solution
bubbled by formaldehyde gas (mL). V is the added volume of
the forming Schiff base solution to this catalytic system (mL),
is the total volume of catalytic system solution (mL). w is
0
1
V
2
4
8
the maximum solubility of formaldehyde (40%) in water,
C
0
is the concentration of used standard formaldehyde gas
(ppm). Therefore, LOD of formaldehyde could also be
calculated to 18.67 ppb (3s/k, n = 9, k is the slope of
relationship curve in the exposure time ranging from 0 to 60
s), according to the equation (1) of gaseous formaldehyde
concentration. This LOD is much lower than those of non-
catalytic sensing systems for detecting gaseous
−1
formaldehyde gas was fixed as 40 mL·min and various
exposure times were set, before the buffer solution was
sealed and heated under various temperatures. To study the
optimum temperature and time of the reaction between OPD
and formaldehyde, a series of temperatures (30, 40, 50, and
o
0 C) and reaction times (15, 30, 60, 90, and 120 min) were
6
4
9-51
tested, respectively (Fig S6). Therefore, after checking a series
o
of experiments, 50 C and 30 min were chosen as the
formaldehyde,
indicative of high sensitivity of this sensing
systems due to introducing catalytic fluorogenic reaction.
The selectivity of this catalytic sensing platform towards
reaction temperature and reaction time, respectively, in this
condensation reaction. Further catalytic reaction experiments
reveal that, with increasing exposure time of introducing
formaldehyde gas, the PL intensity at 564 nm wavelength was
found to have two kinds of decrease (Fig. 12). Two different
response curves likely indicate that two different reactions
2 2
other common gases such as N , CO , and air were also
investigated. Under the similar experimental conditions, it
was found that individual these tested gases did not have a
significant inhibitory effect on this catalytic system, even if
the concentrations of these tested gases were set to be much
8
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 9 of 10
View Article Online
DOI: 10.1039/C8TC01703D
Journal Name
ARTICLE
higher than that of formaldehyde (Fig. 13). Therefore, this
result reveals that this catalytic sensing system has good
selectivity for gaseous formaldehyde. The forming product of
the condensation reaction between formaldehyde and OPD
was further probed by using ESI-MS. According to the result
of ESI-MS, it was deduced that this condensation reaction
could form 1-methylbenzimidazole and benzimidazole
detecting gaseous formaldehyde. Several intriguing
enlightenments could be summarized in this catalytic sensing
system, for example, (i) it is helpful for developing novel
catalysts with uniform and well-defined crystal structures to
establish highly sensitive catalytic sensing systems; (ii) Cu-BTC
MOFs with high specific surface area show high catalytic
2
+
fluorogenic activity, similar to that of Cu ions; (iii) the
structural diversity and alterability of ligands, and diverse
(Scheme 1), because the recorded m/z peak of 133.0762 and
2
+
1
19.0606 could be assigned to 1-methylbenzimidazole ([M +
coordination models of Cu ions can endow Cu MOFs with a
great promise in the field of artificial enzymatic mimics,
+
+
H] , calcd. m/z is 133.0760) and benzimidazole ([M + H] ,
calcd. m/z is 119.0604), respectively (Fig. S7). It should be
pointed out that PXRD result of after sensing tested Cu-BTC
MOFs was found to be almost same with that of unused Cu-
BTC MOFs (Fig.2), substantially supportive of its catalyst role.
2
compared with that of Cu ions.
+
Conflicts of interest
There are no conflicts to declare.
0
0
0
0
0
0
.5
.4
.3
.2
.1
.0
Formaldehyde
Carbon dioxide
Nitrogen
Acknowledgements
Atmosphere
This work was supported by the National Natural Science
Foundation of China (No. 21377124 and 21575044), the
Natural Science Foundation of Fujian Province (No.
2015J01062 and 2017J01015), Promotion Program for Young
and Middle-aged Teacher in Science and Technology
Research (No. ZQN-YX303), the project of new faculty (No.
15BS202) of Huaqiao University, Graphene Powder &
Composite Research Center of Fujian Province (2017H2001),
and the Program for New Century Excellent Talents in Fujian
Province University.
0
5
15 30 60 120 240 360 480 600 900
Exposure time / s
Fig. 13 The selectivity of the catalytic fluorogenic system of the as-prepared Cu-
BTC MOFs towards OPD as the substrate for individual CO , air and
formaldehyde gas under various exposure times. The error bars represent the
standard deviation of three measurements. F represents the PL intensity at
64 nm wavelength of the OPD solution catalyzed by Cu-BTC MOFs in the
N
2
,
2
References:
1
. Gao, L., Zhuang, J., Nie, L., Zhang, J. and Zhang, Y., Nat.
Nanotech., 2007, 2, 577-583.
. Malvi, B., Panda, C., Dhar, B.B. and Gupta, S.S., Chem.
Commun., 2012, 48, 5289-5291.
. Choleva, T.G., Gatselou, V.A., Tsogas, G.Z. and Giokas, D.L.,
Microchim. Acta, 2018, 185:22.
. Jv, Y., Li, B. and Cao, R., Chem. Commun., 2010, 46, 8017-8019.
5. Jiang, H., Chen, Z., Cao, H. and Huang, Y., Analyst, 2012, 137,
560-5564.
0
5
2
absence of formaldehyde or other common tested gases; F represents the PL
intensity at 564 nm wavelength of the OPD solution catalyzed by Cu-BTC MOFs
in the presence of formaldehyde or other common tested gases.
3
4
Conclusions
5
In summary, in this work Cu-BTC MOFs without crystalline
6
. Xu, C. and Qu, X., NPG Asia Materials, 2014, 6, 1-16.
. Wei, H. and Wang, E., Anal. Chem., 2008, 80, 2250-2254.
. Fan, Y. and Huang, Y., Analyst, 2012, 137, 1225-1231.
CuO or Cu
2
O phase could be successfully synthesized by using
7
8
a
low temperature synthesis method, exhibiting the
outstanding catalytic activity towards the traditional enzyme
substrate OPD to generate a fluorescent product. It is first
time for reporting that Cu-based MOFs with uniform and
well-defined structural characterization have excellent
catalytic fluorogenic activity. The effects of experimental
parameters on this catalytic reaction were detailedly
investigated. The catalytic kinetic investigations reveal that
this catalytic fluorogenic reaction of Cu-BTC MOFs towards
OPD as the substrate could be followed by traditional
Michaelis–Menten equation. On the basis of these findings,
and taken together with the fact that the –CHO group of
9. Dai, Z., Liu, S., Bao, J. and Ju, H., Chem. Eur. J., 2009, 15, 4321-
4326.
10. Maji, S.K., Dutta, A.K., Srivastava, D.N., Paul, P., Mondal, A. and
Adhikary, B., J. Mol. Catal. A: Chem., 2012, 358, 1-9.
11. Imaz, I., Rubio-Martínez, M., García-Fernández, L., García, F.,
Ruiz-Molina, D., Hernando, J., Puntes, V. and Maspoch, D., Chem.
Commun., 2010, 46, 4737-4739.
1
1
2. Wei, H. and Wang, E., Chem. Soc. Rev., 2013, 42, 6060-6093.
3. Rowsell, J.L.C., Millward, A.R., Park, K.S. and Yaghi, O.M., J.
Am. Chem. Soc., 2004, 126, 5666-5667.
4. Panella, B., Hirscher, M., Pütter, H. and Müller, U., Adv. Funct.
Mater., 2006, 16, 520-524.
2
formaldehyde can react with the –NH group of OPD to form
1
Schiff bases, a novel, highly selective and sensitive catalytic
sensing platform was thus successfully developed for
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 9
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 10 of 10
View Article Online
DOI: 10.1039/C8TC01703D
ARTICLE
Journal Name
1
5. Du, M., Li, C., Chen, M., Ge, Z., Wang, X., Wang, L. and Liu, C.,
J. Am. Chem. Soc., 2014, 136, 10906-10909.
6. Zhou, L.J., Deng, W.H., Wang, Y.L., Xu, G., Yin, S.G. and Liu,
Q.Y., Inorg. Chem., 2016, 55, 6271-6277.
40. Gascon, J., Aguado, S. and Kapteijn, F., Microporous
Mesoporous Mater., 2008, 113, 132-138.
1
41. Sanz, R., Martínez, F., Orcajo, G., Wojtasc, L. and Brionesa, D.,
Dalton Trans., 2013, 42, 2392-2398.
1
2
1
7. Li, Y.J., Wang, Y.L. and Liu, Q.Y., Inorg. Chem., 2017, 56, 2159-
42. Schlesinger, M., Schulze, S., Hietschold, M. and Mehring, M.,
Microporous Mesoporous Mater., 2010, 132, 121-127.
43. Tian, P., Liu, D., Li, K., Yang, T., Wang, J., Liu, Y. and Zhang, S.,
Bioresour. Technol., 2017, 244, 206-212.
164.
8. Phan, N.T.S., Nguyen, T.T., Nguyen, K.D. and Vo, A.X.T., Appl.
Catal. A: Gen., 2013, 464-465, 128-135.
9. Horcajada, P., Serre, C., Maurin, G., Ramsahye, N.A., Balas, F.,
1
44. Shen, J.S., Wu, J.J., Sun, X.Y., Wu, Z.L., Gao, P. and Liu, B., J.
Mater. Chem. C, 2017, 5, 3757-3764.
Vallet-Regí, M., Sebban, M., Taulelle, F. and Férey, G., J. Am. Chem.
Soc., 2008, 130, 6774-6780.
45. Liu, X., Wang, Q., Zhao, H., Zhang, L., Su, Y. and Lv, Y., Analyst,
2012, 137, 4552-4558.
2
0. Kreno, L.E., Leong, K., Farha, O.K., Allendorf, M., Van Duyne,
R.P. and Hupp, J.T., Chem. Rev., 2012, 112, 1105-1125.
1. Wales, D.J., Grand, J., Ting, V.P., Burke, R.D., Edler, K.J.,
Bowen, C.R., Mintova, S. and Burrows, A.D., Chem. Soc. Rev., 2010,
46. Chai, D., Ma, Z., Qiu, Y., Lv, Y., Liu, H., Song, C. and Gao, G.,
Dalton Trans., 2016, 45, 348-354.
2
47. Zhao, H., Li, X., Li, W., Wang, P., Chen, S. and Quan, X., RSC
Adv., 2014, 4, 36444-36450.
4, 15-18.
2
2. He, L., Liu, Y., Liu, J., Xiong, Y., Zheng, J., Liu, Y. and Tang, Z.,
48. Dong, S. and Dasgupta, P.K., Environ. Sci. Technol., 1986, 20,
637-640.
Angew. Chem. Int. Ed., 2013, 52, 3741-3745.
3. Lustig, W.P., Mukherjee, S., Rudd, N.D., Desai, A.V., Li, J. and
Ghosh, S.K., Chem. Soc. Rev., 2017, 46, 3242-3285.
2
49. Zhou, K., Ji, X., Zhang, N. and Zhang, X., Sens. Actuators, B,
2006, 119, 392-397.
2
5
2
4. Hu, Z., Deibert, B.J. and Li, J., Chem. Soc. Rev., 2014, 43, 5815-
50. Kawamura, K., Kerman, K., Fujihara, M., Nagatani, N., Hashiba,
T. and Tamiya, E., Sens. Actuators, B, 2005, 105, 495-501.
51. Dong, B., Song, X., Tang, Y. and Lin, W., Sens. Actuators, B,
2016, 222, 325-330.
840.
5. Hu, Z., Tan, K., Lustig, W.P., Wang, H., Zhao, Y., Zheng, C.,
Banerjee, D., Emge, T.J., Chabal, Y.J. and Li, J., Chem. Sci., 2014, 5,
4873-4877.
26. Tranchemontagne, D.J., S, J.L.M., Keeffe, M.O. and Yaghi,
O.M., Chem. Soc. Rev., 2009, 38, 1257-1283.
7. Lee, J., Farha, O.K., Roberts, J., Scheidt, K.A., Nguyen, S.T. and
Hupp, J.T., Chem. Soc. Rev., 2009, 38, 1450-1459.
8. Tan, H., Ma, C., Gao, L., Li, Q., Song, Y., Xu, F., Wang, T. and
Wang, L., Chem. Eur. J., 2014, 20, 16377-16383.
2
2
2
1
3
9. Chen, Y., Hoang, T. and Ma, S., Inorg. Chem., 2012, 51, 12600-
2602.
0. Liu, F.L., Xu, Y.W., Zhao, L.M., Zhang, L.L., Guo, W.Y., Wang,
R.M. and Sun, D.F., J. Mater. Chem. A, 2015, 3, 21545-21552.
3
1
3
1. Ai, L., Li, L., Zhang, C., Fu, J. and Jiang, J., Chem. Eur. J., 2013,
9, 15105-15108.
2. Wang, Y., Zhu, Y., Binyam, A., Liu, M., Wu, Y. and Li, F.,
Biosensors and Bioelectronics, 2016, 86, 432-438.
3
4
3
3. Liu, Y.L., Zhao, X.J., Yang, X.X. and Li, Y.F., Analyst, 2013, 138,
526-4531.
4. Qin, F., Jia, S., Wang, F., Wu, S., Song, J. and Liu, Y., Catal. Sci.
Technol., 2013, 3, 2761-2768.
3
9
3
5. Xu, Y., Wu, X.Q., Shen, J.S. and Zhang, H.W., RSC Adv., 2015, 5,
2114-92120.
6. Tovar, T.M., Zhao, J., Nunn, W.T., Barton, H.F. and Peterson,
G.W., J. Am. Chem. Soc., 2016, 138, 11449-11542.
7. Schlichte, K., Kratzke, T. and Kaskel, S., Microporous
Mesoporous Mater., 2004, 73, 81-88.
8. Hartmann, M., Kunz, S., Himsl, D. and Tangermann, O.,
Langmuir, 2008, 24, 8634-8642.
3
3
39. Huang, K., Xu, Y., Wang, L. and Wu, D., RSC Adv., 2015, 5,
32795-32803.
1
0 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins