TiO2@UiO-66 Composites with Efficient Adsorption and Photocatalytic Oxidation of VOCs: Investigation of Synergistic Effects and Reaction Mechanism

Article abstract of DOI:10.1002/cctc.202001466

TiO₂@UiO-66 composite with intimate contact interfaces is fabricated by in situ solvothermal methods. Compared with other UiO-based composites, TiO₂@UiO-66 exhibits superior photocatalytic activity for oxidation of toluene into CO₂ during long-time reaction under flowing conditions. This is because (1) the intimate contact interface and well-matched band structure between TiO₂ and UiO-66 can effectively separate and transfer photogenerated electrons; (2) the synergistic effect between UiO-66 and TiO₂ promotes the adsorption of toluene and desorption of CO₂ and provides sufficient active sites for photocatalytic reaction. The toluene conversion and CO₂ production on 4TiO₂@U are 3.27 and 4.10 times higher than that on UiO-66, respectively. 4TiO₂@U also shows the highest activity for formaldehyde and rhodamine B degradations. The in situ FTIR results exhibit that toluene can be oxidized by ^.O₂^? and h⁺ to benzaldehyde and benzoic acid, then further oxidized to oxalic acid, and finally mineralized into CO₂ and H₂O.

Full text of DOI:10.1002/cctc.202001466

The European Society Journal for Catalysis
Supported by
Accepted Article
Title: TiO2@UiO-66 Composites with Efficient Adsorption and
Photocatalytic Oxidation of VOCs: Investigation of Synergistic
Effect and Reaction Mechanism
Authors: Jinhui Zhang, Ziyang Guo, Zhenxiang Yang, Jun Wang, Jun
Xie, Mingli Fu, and Yun Hu
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: ChemCatChem 10.1002/cctc.202001466
Link to VoR: https://doi.org/10.1002/cctc.202001466
01/2020

10.1002/cctc.202001466
ChemCatChem
FULL PAPER
TiO2@UiO-66 Composites with Efficient Adsorption and
Photocatalytic Oxidation of VOCs: Investigation of Synergistic
Effect and Reaction Mechanism
Jinhui Zhang,[a] Ziyang Guo,[a] Zhenxiang Yang,[a] Jun Wang,[a] Jun Xie,[a] Mingli Fu,[a,b,c] Yun Hu*[a,b,c]
[a]
J. Zhang, Z. Guo, Z. Yang, J. Wang, J. Xie, Prof. M. Fu, Prof. Y. Hu*
School of Environment and Energy
South China University of Technology
Guangzhou Higher Education Mega Centre, Guangzhou 510006 (P.R. China)
*E-mail: huyun@scut.edu.cn
[b]
[c]
Prof. M. Fu, Prof. Y. Hu
Guangdong Provincial Key Laboratory of Atmospheric Environment and Pollution Control
South China University of Technology
Guangzhou Higher Education Mega Centre, Guangzhou 510006 (P.R. China)
Prof. M. Fu, Prof. Y. Hu
Guangdong Provincial Engineering and Technology Research Centre for Environmental Risk Prevention and Emergency Disposal
South China University of Technology
Guangzhou Higher Education Mega Centre, Guangzhou 510006 (P.R. China)
Supporting information for this article is given via a link at the end of the document.
Abstract: TiO2@UiO-66 composite with intimate contact interfaces
superior photocatalytic performance due to the effective
separation and transfer of photoinduced electrons-holes.
Therefore, various TiO2 based heterojunctions including
is fabricated by in situ solvothermal methods. Compared with other
UiO-based
composites,
TiO2@UiO-66
exhibits
superior
photocatalytic activity for oxidation of toluene into CO2 during long-
time reaction under flowing conditions. This is because (1) the
intimate contact interface and well-matched band structure between
TiO2 and UiO-66 can effectively separate and transfer
photogenerated electrons; (2) the synergistic effect between UiO-66
and TiO2 promotes the adsorption of toluene and desorption of CO2
and provides sufficient active sites for photocatalytic reaction. The
toluene conversion and CO2 production on 4TiO2@U are 3.27 and
4.10 times higher than that on UiO-66, respectively. 4TiO2@U also
shows the highest activity for formaldehyde and Rhodamine B
degradations. The in situ FTIR results exhibit that toluene can be
WO3/TiO2,[13]
Pt-MoS2/TiO2,[14]
CuS-CdS/TiO2,[15]
and
[16]
LaVO4/TiO2
have drawn much attention due to their good
photocatalytic performance for toluene degradation. However,
the activity and mineralization efficiency dramatically dropped
after several static cycles or long-term flowing condition
evaluation due to the carbonaceous residues during the reaction.
Therefore, to explore of TiO2-based composites with stable and
high photocatalytic activity and CO2 selectivity during long-term
VOCs degradation is imperative.
Metal-organic frameworks (MOFs) are a fascinating class of
porous crystalline materials built by joining the metal-oxo
clusters with organic linker. MOFs have drawn extensive
attention due to the tunable pore size, large surface area, pore
volumes and designable framework structures.[17] Based on
these characteristics, MOFs have attracted great study in many
-
oxidized by •O2 and h+ to benzaldehyde and benzoic acid, then
further oxidized to oxalic acid, and finally mineralized into CO2 and
H2O.
fields, such as gas storage,[18] separation[19] and catalysis[20]
.
Meanwhile, MOFs have been used in photocatalytic oxidation of
VOCs as photocatalysts and exhibit some photocatalytic
activity.[21-23] TiO2-UiO-66-NH2 composite was synthesized and
used for VOCs degradation under flowing conditions. The
composite exhibited good VOCs conversion while the CO2
selectivity is poor.[21-22] MIL-101-Fe-NH2 was synthesized by
Zhang et al. and used for toluene degradation under static
conditions. It was found that the sample had a good toluene
removal rate, but it took 10 h to reach the degradation rate of
79.8%.[23] Additionally, the strength of the interaction between
MOF and toluene or CO2 was not considered, and some
researches have pointed out that MOF with -NH2 is not an ideal
MOF candidate material for VOCs degradation because -NH2
has strong adsorption performance for CO2 molecule.[24-26]
Moreover, the possible reaction mechanism of toluene on MOF
based composite under dynamic reaction system has not been
explored. Therefore, we have designed a high-performance
MOF based composite by in situ synthesis method for the first
time for VOCs degradation under flowing conditions, and
explored the role of MOFs in the VOCs oxidation process.
1. Introduction
Volatile organic compounds (VOCs) are considered as a kind
of toxic pollutants in the atmosphere, which are mainly from
building materials, furniture, decoration materials and other
consumer products.[1,2] They not only give rise to a harmful effect
on human health but also lead to serious ecosystem effects.[3,4]
Semiconductor photocatalysis has been proved to be an
effective and promising alternative technology for the removal of
VOCs from the atmospheric environment under mild operating
conditions.[5-7]
TiO2 is the most common photocatalyst in environmental
remediation because of its strong oxidative ability, low
environmental influence, low cost and chemical stability.[8,9]
However, the rapid recombination of photoinduced carriers limits
the wide applications of TiO2. Therefore, numerous studies have
been carried out to solve this problem, such as ions doping[10]
surface modification[11] and semiconductor coupling[9,12]. Among
them, semiconductor coupling is an efficient method to achieve
,
1
This article is protected by copyright. All rights reserved.

10.1002/cctc.202001466
ChemCatChem
FULL PAPER
Herein, a series of TiO2@UiO-66 composite is fabricated via
in situ solvothermal approach and the photocatalytic
performance of the composite was investigated by VOCs
oxidation under UV condition. UiO-66 is a typical Zr-based MOF
material, which has a similar topological structure with UiO-66-
NH2, with regular 3D structure, high surface area, excellent
stability and semiconductor properties. The TiO2@UiO-66
composite showed superior and stable photocatalytic activity
and CO2 selectivity for toluene degradation during long-term
evaluation under flowing condition, compared to pure TiO2, UiO-
66 and TiO2-UiO-66 prepared by evaporation (named as: 4TiO2-
U-Evap) and mechanical (named as: 4TiO2-U-Mech) methods.
The intimate contact interfaces between TiO2 and UiO-66 in the
TiO2@UiO-66 composite promoted the separation and the
transfer of photoinduced charge carriers. Meanwhile, the
synergistic effect of the adsorption capacity of the MOF and the
photocatalytic properties of TiO2 for toluene significantly
enhanced the removal efficiency. Such a method of exploring
the role of MOF in toluene photocatalytic oxidation provided a
theoretical foundation for the design of high-performance MOF
based photocatalysts for VOCs degradation.
Zr4+ (preferential pre-coordination with soft oxygen groups of the
TiO2 based on the hard-soft acid-base principle) and H2BDC in
situ self-assembly around the TiO2 under a high temperature to
form TiO2@UiO-66.[22,28] Therefore, the strong phase
interactions exist between TiO2 and UiO-66 based on the XRD
results. In addition, UiO-66-NH2, 4TiO2-U-Mech, 4TiO2-U-Evap
and 4TiO2@UN have been all successfully prepared. They also
have phase interactions exist between two components in the
composite (Figure 1c and 1d). However, compared with the
composite prepared by evaporation and mechanical methods
(Figure 1d), the diffraction peak of 4TiO2@U prepared by in situ
method shifts to a higher large-angle side, suggesting a stronger
interaction between two components in the composite prepared
by in situ solvothermal method.
2. Results and Discussion
2.1 Characterization of photocatalysts
Figure 2. FT-IR spectra (a,c) and enlarged view (b,d) of the different
composites.
The FT-IR spectra are performed to illustrate the molecular
structure of the samples. In Figure 2a, the broad peak located
around 3000-3700 cm-1 is ascribed to the O-H stretching band of
water molecules on the samples. The broad peak attributed to
Ti-O-Ti stretching vibration is observed on TiO2 at the range of
400-900 cm-1. The band at 1638 cm-1 is assigned to hydroxyl
stretching vibration resulting from the Ti-OH bond on the TiO2
surface. As for UiO-66, the bands at 1567 and 1393 cm-1 are
assigned to the asymmetric and symmetric vibration of carboxyl
groups in the benzene rings of UiO-66, respectively.[29] In
addition, the peaks at 818 and 745 cm-1 are the C-H vibration
and O-H vibration in terephthalate ligand, respectively.[29,30] The
band at 550 cm-1 is related to the Zr-(OC) asymmetric stretching
vibration.[30] The peaks at 660 and 475 cm-1 are assigned to the
µ3-O and the µ3-OH stretching vibration, respectively.[30,31]
Compared with the pristine UiO-66, the relative intensity of UiO-
66 characteristic peaks in TiO2@UiO-66 significantly decreases,
and the characteristic peak of TiO2 increases. It is worth noting
that the IR band ~705 gradually appeared and increased with
increase TiO2 content (see inset enlarged view in Figure 2a),
suggesting that the generation of Ti-O-Zr groups.[32] The new
characteristic peak indicated that the TiO2 successfully
coordinated with Zr4+ cations, forming tight interfacial contact
between TiO2 and UiO-66.[22] Furthermore, from the narrow scan
spectra (Figure 2b), the symmetric Vs(COO-) and asymmetric
Figure 1. XRD patterns (a,c) and enlarged view (b,d) of the different
composites.
XRD analysis is used to determine the crystallite structure
and the composition of composites. The diffraction of UiO-66 is
perfectly in agreement with that reported in the literature (Figure
1a),[27] demonstrating UiO-66 has been successfully synthesized.
In the case of TiO2, only anatase phase is detected (JCPDS
021-1272). For the TiO2@UiO-66 composite, all peaks in
composite can be attributed to those of UiO-66 and TiO2,
indicating that the composite is successfully synthesized.
Meanwhile, the XRD peaks of TiO2@UiO-66 composite exhibit
an obvious right-shift compared to pure UiO-66 (Figure 1b). The
right-shift of XRD peaks is may be because the hard oxophilic
2
This article is protected by copyright. All rights reserved.

10.1002/cctc.202001466
ChemCatChem
FULL PAPER
Figure 3. SEM images of TiO2 (a), UiO-66 (b), 2TiO2@U (c), 4TiO2@U (d), 6TiO2@U (e) and TEM images of 4TiO2@U (f, g and h).
3
This article is protected by copyright. All rights reserved.

10.1002/cctc.202001466
ChemCatChem
FULL PAPER
Vas(COO-) vibration of carboxyl groups in the ligand of
MOFs slightly shift from 1393 and 1567 cm-1 to 1398 and 1576
cm-1 respectively, with increasing TiO2 content. This suggests
that the chemical environment around UiO-66 has been
changed, because the UiO-66 crystals grow in situ in the
presence of the TiO2 nanoparticle. Besides, the IR data show
that UiO-66-NH2, 4TiO2@UN, 4TiO2-U-Mech and 4TiO2-U-Evap
have been successfully prepared. Meanwhile, there are also
interactions between the two components in the composite
(Figure 2c, 2d and Figure S1) because the carboxyl groups in
the ligand of MOFs slightly shift to higher wavenumber.
However, compared with 4TiO2-U-Mech and 4TiO2-U-Evap, the
carboxyl groups of 4TiO2@U shift to a higher wavenumber,
indicating that TiO2 and UiO-66 in 4TiO2@U have a stronger
interaction, which is in accordance with XRD results.
the Zr 3d5/2 (182.56 and 183.21 eV) and Zr 3d3/2 (185.06 and
185.65 eV), respectively, suggesting the existence of Zr+4.[29] In
the case of 4TiO2@U, the binding energy of C 1s is 0.05 eV
higher than that of UiO-66 sample. In contrast, the peaks of O
1s and Zr 3d present a significant negative shift of -1.52 and -
0.09 eV respectively, as compared with the UiO-66 sample.
These results suggest that the surrounding chemical
environment of UiO-66 is changed after the introduction of TiO2.
In addition, the characteristic peaks of Ti 2p in the 4TiO2@U
composite (458.55 and 464.60 eV) is 0.35 eV higher than that
in TiO2 (458.45 and 464.25 eV),[34] indicating the existence of
an interaction between TiO2 and UiO-66.
The thermal stability of the composite is analyzed with
4TiO2@U as a representative material and the result is shown
in Figure S2. The Thermo-gravimetric (TG) results of pure UiO-
66 exhibits three weight loss, which can be corresponded to the
o
removal of water molecules from surface (below 150 C), guest
molecules decomposition (200-400 oC) and the BDC unit
decomposition of UiO-66 (500-600 oC), respectively.[31,33]
However, 4TiO2@U has almost no weight loss below 500 oC,
showing a significantly enhanced thermal stability compared to
UiO-66. This may be due to the stronger interaction between
TiO2 and UiO-66 which prevents the decomposition of UiO-66.
Based on the TG results, the actual contents of TiO2 and UiO-
66 in 4TiO2@U are 84% and 16%, respectively.[21]
The size, morphology and crystallinity of the as-prepared
samples are observed by the SEM and TEM analyses. Pure
Figure 4. XPS spectra of TiO2, UiO-66 and 4TiO2@U: C 1s (a), O 1s (b), Zr
3d (c) and Ti 2p (d).
TiO2 consists of
a large number of small nanoparticles
aggregated together (Figure 3a). As shown in Figure 3b,
pristine UiO-66 exhibits uniform octahedral structure and clean
surface with grain sizes of the edge are about 400 nm. As for
TiO2@UiO-66 composite, TiO2 is attached to the surface of
UiO-66, which is conducive to promote the contact between
active sites and VOCs molecules as well as light harvesting in
the photocatalytic reaction (Figure 3c-g). Besides, the edge of
UiO-66 in composite gradually increases from ca. 200 nm to
500 nm with the increase of the TiO2 ratio (Figure 3c-e),
indicating that strong interactions exist between TiO2 and UiO-
66 of the composite. Meanwhile, the TiO2 nanoparticles are
intimately adhering on the surface of UiO-66 (Figure 3f and g),
and the lattice spacing is ca. 0.35 and 0.235 nm, corresponding
to the {101} and {001} planes of anatase TiO2, respectively.
The XPS results of 4TiO2-U-Mech, 4TiO2-U-Evap and
4TiO2@UN are also investigated (Figure S4 and Figure S5).
Compared with 4TiO2-U-Evap and 4TiO2-U-Mech, the peaks of
Zr 3d in 4TiO2@U shift to lower binding energy, but the Ti 2p
shift to a higher value, indicating the electron density of TiO2 in
4TiO2@U shift to Zr more easily. Therefore, it can be concluded
that TiO2 and UiO-66 in 4TiO2@U prepared by one-pot
solvothermal method have a stronger interactions and closer
interface contact.
2.2. Photoelectrochemical properties
The chemical composition and valence state in TiO2, UiO-66,
4TiO2@U, 4TiO2@UN, 4TiO2-U-Evap and 4TiO2@U-Mech are
obtained by XPS analyses. XPS survey spectra (Figure S3 and
Table S1) indicates that TiO2-UiO composite is made up of C, N,
O, Zr and Ti elements, indicating a two-phase composition of
the materials. For UiO-66, the fitted peaks of C 1s at 284.50,
285.11 and 288.80 eV are assigned to the C=C bond, C-H
bond and the carboxylate (O-C=O) carbon, respectively (Figure
4a).[33] The peaks of O 1s at 530.46, 531.54 and 532.27 eV can
be assigned to the Zr-O bond, C=O in H2BDC and hydroxyl
groups, respectively (Figure 4b).[29] The Zr 3d (Figure 4c) core
level spectrum exhibits four peaks, which can be attributed to
Figure 5. UV-vis absorption spectra and calculated Tauc plot (inset) (a) and
Mott-Schottky plot (b) of TiO2, UiO-66 and TiO2@UiO-66 composites.
4
This article is protected by copyright. All rights reserved.

10.1002/cctc.202001466
ChemCatChem
FULL PAPER
UV-vis absorption spectra of pure TiO2, UiO-66 and TiO2-
UiO composite are measured to evaluate the optical absorption
property. As shown in Figure 5a, compared with the pristine
UiO-66, the UV light region absorption intensity of TiO2@UiO-
66 is obviously enhanced as the amount of TiO2 increases,
which can be attributed to the excellent interfacial contact
between the TiO2 and UiO-66. Meanwhile, the absorption
intensity of 4TiO2@U is higher than that of 4TiO2-U-Mech and
4TiO2-U-Evap (Figure S6). This is expected to improve the
photocatalytic performance of the TiO2@UiO-66 composite for
VOCs degradation.[35] Correspondingly, the band gap energy
(Eg) of samples can be calculated by the Kubelka-Munke
equation. The Tauc plot (the inset figure in Figure 5a)
demonstrates the Eg of TiO2@UiO-66 composite situates exist
between TiO2 and UiO-66, indicating the strong interaction of
the composite structure and the generation of heterojunction
between TiO2 and UiO-66.
separation and transfer efficiency of photoexcited electron-hole
(Figure 6b).[9] From the EIS results displayed in Figure 6c and
6d, it can be seen that 4TiO2@U also exhibits the highest
charge carrier transfer efficiency due to its lowest arc radius,
indicating that a “nanoscale mixing” by one-pot solvent-
thermal synthesis method will promote electron transfer.
2.3. Photocatalytic performance
2.3.1. Toluene removal and CO2 production
The photocatalytic activity of TiO2, UiO-66 and TiO2@UiO-
66 composite is evaluated by oxidation of toluene during long
time reaction under UV condition. The sag curves in the first
180 min are attributed to the toluene adsorption/desorption
process on the catalyst surfaces (Figure 7a). Under the UV light
condition, the toluene concentration exhibits a sudden decrease
and then to be stable, especially when toluene passed through
the TiO2@UiO-66 composite. The pristine UiO-66 and TiO2
show certain photocatalytic activity with only 20.37% and
36.89% of toluene removal respectively, in 720 min, which can
be attributed to the rapid recombination of photogenerated
carriers. Compared with a single material, the TiO2@UiO-66
composite exhibits excellent photocatalytic activity, and the
highest efficiency is obtained by 4TiO2@U, on which 66.59% of
toluene is removed within 720 min under UV light irradiation.
Also, 4TiO2@U shows the highest CO2 production (103.92
ppm) and selectivity (89%), which is much higher than that of
TiO2 (62.13 ppm) and UiO-66 (25.34 ppm). Thus, it can be
found that the 4TiO2@U sample shows superior toluene
conversion and CO2 production, which are 3.27 and 4.10 times
higher than that of UiO-66 as well as 1.81 and 1.67 times
higher than that of pure TiO2, respectively. These results
illustrate that the TiO2@UiO-66 prepared by in situ solvothermal
methods are able to promote the separation and transfer of
photoinduced carriers, thus improving the photocatalytic
performance.
To further clarify the electronic structure of the catalysts, the
electrochemical flat potential has been measured by using
Mott-Schottky plots at the frequency of 1000 Hz. The slopes of
all samples are positive, indicating their typical n-type
semiconductor nature (Figure 5b). The flat band position of
TiO2 and UiO-66 is -0.08 and -0.47 eV vs NHE, respectively.
The conduction band potential (ECB) of n-type semiconductor is
0.2 eV above the flat band potential.[29] Thus, the ECB of TiO2
and UiO-66 is estimated to be -0.28 and -0.67 eV, respectively.
Combined with Eg results and the formula of Eg=EVB-ECB, the
valence band position (EVB) of TiO2 and UiO-66 is 3.01 and
3.23 eV, respectively.
Figure 7. Toluene removal (a) and generated COx concentration (b) on the
catalysts under UV light irradiation. The close symbols represent [CO2] and
the open symbols represent [CO].
Figure 6. Photocurrent responses (a,b) and EIS Nyquist plots (c,d) of the
different composites.
To unveil the charge migration and transfer efficiency in
composite, photocurrent analyses are performed and the
results are illustrated in Figure 6. Compared with pure TiO2 and
UiO-66, 4TiO2@U exhibits superior photocurrents intensity
(Figure 6a), indicating that the two components in the
composite promote the separation of the photogenerated
carrier. 4TiO2@U also exhibits a higher photocurrent response
than 4TiO2-U-Evap and 4TiO2-U-Mech, suggesting that a
compact connection between the two components can promote
To prove the superiority of UiO-66 over other common UiO
topology materials such as UiO-66-NH2, TiO2@UiO-66-NH2
composite is used for toluene degradation under the same
condition. As shown in Figure S7, 4TiO2@U exhibits higher
photocatalytic activity and CO2 production than 4TiO2@UN.
This is because amino groups in the porous structure of UiO-
66-NH2 served as basic sites for adsorbing CO2 molecule,
which inhibits the contact of toluene with the active sites.[26,36]
5
This article is protected by copyright. All rights reserved.

10.1002/cctc.202001466
ChemCatChem
FULL PAPER
2.3.2. Toluene and formaldehyde degradation on different
composites
respectively. Both liquid phase and gas phase reactions show
that 4TiO2@U can be widely used in water treatment and air
pollution control.
The photocatalytic oxidation of toluene by 4TiO2-U-Mech
and 4TiO2-U-Evap are also performed under the same reaction
condition (Figure 8). 4TiO2@U shows higher photocatalytic
2.3.4. Effects of humidity
performance
than
4TiO2-U-Mech
and
4TiO2-U-Evap,
suggesting the in situ prepared material can more easily
promote migration and separation of photogenerated charge
carriers because of the intimate connection between the two
components. Also, the photocatalytic oxidation of formaldehyde
has been carried out (Figure S8). 4TiO2@U shows the highest
formaldehyde conversion, which is 83% within 72 h of light
irradiation. Moreover, the CO2 selectivity on 4TiO2@U reaches
90%. We also compared our work with some relevant
researches. The composites and reaction system in this study
exhibit higher photocatalytic activity and selectivity even under
more difficult reaction conditions (Table S2).
To investigate the effect of relative humidity (RH) on toluene
removal over 4TiO2@U material, the oxidation reactions of
toluene with different relative humidity levels (RH=0% (extreme
dry), 20% (dry), 40% (dry) and 60% (moderate), 80% (humid))
have been performed and the results are shown in Figure 10.
When the RH increases from 0% to 20%, the adsorption
amount of toluene is similar, indicating that relative dry
condition has little effect on the adsorption of toluene. However,
the adsorption amount of toluene significantly decreases when
the RH increases from 20% to 80%, suggesting that a high
water vapor level in the air stream can generate a well-
organized physical barrier on the material surface and impede
effective contact between pollutant and catalyst surface.[37]
Under the UV light condition, it can be found that the
photocatalytic performance of 4TiO2@U also depends on the
RH. As the RH increases from 0 to 80%, the toluene removal
and CO2 production initially increases and then decreases,
reaching a maximum performance at RH=60%. According to
previous study,[37,38] water vapor can generate hydroxyl radical
( • OH) served as active species during the photocatalytic
process. Meanwhile, a research has pointed out that the
competitive adsorption of water molecules and reaction
intermediates on the photocatalyst surface can prevent the
deactivation of the catalyst.[39] Thus, it can be concluded that
water molecules both have a negative effect on the adsorption
process and a positive effect on the photocatalysis process.
Figure 8. Toluene removal (a) and generated COx concentration (b) on
different composites under UV light irradiation. The close symbols represent
[CO2] and the open symbols represent [CO].
2.3.3. Photocatalytic degradation of RhB
Figure 10. Toluene removal (a) and generated COx concentration (b) by
4TiO2@U under different relative humidity. The close symbols represent
[CO2] and the open symbols represent [CO].
Figure 9. Photocatalytic degradation of RhB (a) and linear fit log plots of RhB
(b) degradation curves by different photocatalysts under UV light irradiation.
To further investigate the effect of RH on adsorption and
photocatalysis process, the photocatalytic degradation of
toluene by 4TiO2@U has been performed at 60% or 0% RH
and under the dark or illumination conditions, respectively
(Figure S9). It can be found that water molecules not only
occupy active sites under dark conditions and inhibit the
adsorption of toluene, but also can promote the degradation of
toluene under UV light irradiation. This clearly indicates that
appropriate RH plays a key role in photocatalytic reaction.
In order to fully evaluate the photocatalytic performance of
the composite, photocatalytic degradation of RhB in wastewater
is carried out under the UV light conditions. Compared with
pure TiO2, UiO-66, 4TiO2-U-Mech and 4TiO2-U-Evap, 4TiO2@U
shows the highest photocatalytic activity, the removal efficiency
of RhB is 97.58% in 180 min (Figure 9a). These results indicate
that the composite prepared by in situ solvothermal method can
promote the charge carrier separation, thus improving the
photocatalytic activity. A pseudo-first order kinetic equation [-
ln(C/Co) = kt] produces a good fit to the experimental data
(Figure 9b). The reaction rate constant k of 4TiO2@U is
0.01838 min-1, which is about 1.82 and 8.63 times higher than
that of TiO2 (0.01009 min-1) and UiO-66 (0.00213 min-1),
2.3.5. Catalyst stability
6
This article is protected by copyright. All rights reserved.

10.1002/cctc.202001466
ChemCatChem
FULL PAPER
To verify the stability of the composite under UV light
irradiation, 4TiO2@U has been characterized before and after
photoreaction using XRD and SEM analyses. The crystalline
structure of the fresh and used composites are similar after 720
min irradiation (Figure S10a). In addition, no apparent changes
in morphology structure are observed before and after the
reaction (Figure S10b and 10c). These results demonstrate that
the as-prepared 4TiO2@U composite has high stability during
the photocatalytic oxidation process.
Table 1. Desorption temperature and integrated area of desorption peak of
TiO2, UiO-66 and TiO2-UiO composite.
Samples
TiO2
UiO-
66
4TiO2@U
4TiO2@UN
4TiO2-
U-
4TiO2-
U-
Meach
Evap
Area[a]
63
4657
574
943
436
267
421
214
428
313
432
Temperature[b]
424
[a] Integrated area of desorption peak. [b] Desorption temperature.
2.4 Mechanism for toluene photocatalytic oxidation
2.4.1 Temperature programmed desorption
The fast desorption of CO2 around the active centers is also
favorable for increasing catalytic activity and CO2 selectivity.
Thus, the interaction between CO2 and materials is investigated
using CO2-TPD and the result are shown in Figure S11. Both
4TiO2@U and 4TiO2@UN present three desorption peaks at
about 110, 200 and 290 oC, which can be assigned to CO2
desorption from weak basic (50~230 oC) or strong basic
(230~365 oC) groups.[24,40] As shown in Table S3, the
desorption amount (the desorbed peak area) of CO2 at strong
basic sites of 4TiO2@UN is more than that of 4TiO2@U.
Meanwhile, the strong base/weak base ratio of 4TiO2@UN is
higher than that of 4TiO2@U. These results suggest that the
adsorption capacity of 4TiO2@UN to CO2 is higher than that of
4TiO2@U. This is because amino groups served as basic sites
in the organic ligand can immobilize CO2 molecules to stay on
the reactive site.[34] Combined with the C7H8-TPD result, it can
be found that 4TiO2@U can immobilize toluene for
photocatalytic degradation and release CO2 to airstream due to
the higher selective adsorption of toluene than that of CO2.
Thus, 4TiO2@U exhibits higher photocatalytic activity and CO2
selectivity than 4TiO2@UN.
Figure 11. Toluene-TPD profiles of different samples: (a) UiO-66, TiO2 and
4TiO2@U, (b) 4TiO2@U, 4TiO2-U-Evap, 4TiO2-U-Mech and 4TiO2@UN.
The C7H8-TPD tests are used to provide an insight into the
interaction between toluene and samples. As shown in Figure
11a and Table 1, pure TiO2 shows poor toluene adsorption
capacity due to its low surface area and non-porous structure.
In contrast, due to the high surface area and 3D porous
structure, pristine UiO-66 exhibits excellent toluene adsorption
capacity. As for 4TiO2@U, the toluene adsorption capacity is
higher than that of TiO2, but lower than that of UiO-66,
indicating that UiO-66 in the composite is the main site for
toluene adsorption. Meanwhile, the desorption peak
temperature of toluene on UiO-66 is higher than that of pure
TiO2, suggesting the interaction of toluene with UiO-66 is
stronger than that with TiO2. For 4TiO2@U composite, the
desorption peak temperature of toluene is between pure TiO2
and UiO-66, indicating that the interaction between 4TiO2@U
and toluene is mainly originated from UiO-66. Additionally,
compared with TiO2 and UiO-66, 4TiO2@U composite exhibits
much higher activity (Figure 7), indicating that the strong
toluene adsorption capacity of UiO-66 and superior
photocatalytic activity of TiO2 are well inherited by 4TiO2@U.
Besides, 4TiO2@U also exhibits higher desorption temperature
and larger desorption peak area compared with 4TiO2@UN,
4TiO2-U-Mech and 4TiO2-U-Evap (Figure 11b and Table 1),
suggesting that the interaction between toluene and 4TiO2@U
is stronger than that between toluene and the other three
composites. Meanwhile, 4TiO2@U shows higher photocatalytic
performance than 4TiO2@UN, 4TiO2-U-Mech and 4TiO2-U-
Evap (Figure S7 and S8). Thus, it can be concluded that the
effective adsorption of toluene and the strong interaction
between toluene and composites are beneficial to toluene
degradation.
2.4.2. In situ FT-IR results
Figure 12. In situ FT-IR spectra of toluene oxidation (a) on 4TiO2@U, (b) and
(c) at the wavenumber range of 3800-3600 and 1800-1400 cm-1 from Figure
13a, and (d) on UiO-66 and 4TiO2@U at 60 min under UV light irradiation.
In situ FT-IR tests are employed to investigate the trend of
transient intermediates and give an important insight into the
7
This article is protected by copyright. All rights reserved.

10.1002/cctc.202001466
ChemCatChem
FULL PAPER
reaction mechanism. Figure 12 shows in situ FTIR spectra of
samples during the photo-oxidation of gas toluene in a real-time
flowing system. The spectra are collected using the clean
sample as the background. Prior to UV light illumination (t=0),
toluene is introduced into the chamber to reach adsorption
equilibrium on the surface of materials, and the characteristic
peaks of toluene gradually appear. The peaks around 3028 and
2888 cm-1 can be ascribed to the C-H stretching vibration of the
aromatic ring and methyl group,[12] respectively (Figure 12a).
The abroad bands from 3800 to 3600 cm-1 are the feature
bands of hydroxyl groups and act as the adsorption sites of
toluene, including the bridged (3685 and 3650 cm-1) and
terminal hydroxyls (3752, 3741, 3729 and 3712 cm-1) (Figure
12b).[41,42] The bands at 1608, 1515 and 1490 cm-1 are
assigned to vibrations of the benzene rings, and the band at
1460 cm-1 is associated with the asymmetric methyl bending
vibration (Figure 12c). When the UV light irradiates on the
surface of the sample, the peaks at 2360 and 2340 cm-1
corresponding to CO2 increase obviously as the reaction
proceeds. Meanwhile, some new surface species are formed
and increase significantly with increasing reaction time (Table
S4). Specifically, the new peaks at 1687 and 1735 cm-1 can be
attributed to the carbonyl vibration of the aldehyde group and
the vibrational mode of a carbonyl group respectively, indicating
the formation of benzaldehyde.[12] The bands at 1560 and 1542
cm-1 are caused by the asymmetric stretching vibration model
of the carboxylate group COO-, suggesting the formation of
benzoic acid.[7,43] The band at 1720 and 1423 cm-1 reported as
the v (C=O) and v (C-O) of oxalic acid, indicating toluene is
effectively oxidation by composite under UV condition.[12,44] The
band at 1635 cm-1 is related to the scissor vibration modes of
physically adsorbed water. According to the experimental
results and reaction pathway proposed by previous reports,
toluene oxidation can be divided into three steps: 1) toluene is
adsorbed on the surface of the composite; 2) the methyl groups
2.4.3. Reactive oxygen species confirmation and interfacial
electron transfer
To explore the main active species and possible reaction
mechanism, a series of the radical trapping experiments are
carried out with trapping agents of AgNO3 for e-,
-
triethanolamine (TEOA) for h+, p-benzoquinone (BQ) for •O2 ,
-
isopropanol (IPA) for •OH. The •O2 is the main active specie
because the composite nearly deactivate when it is
compounded with BQ (Figure 13). The removal ratio of toluene
decreases rapidly when e- is trapped by AgNO3, suggesting that
e- can be captured by O2 to form •O2- for the further oxidation of
toluene. The conversion of toluene also obviously depresses
when the composite is compounded with TEOA, indicating that
h+ is one of the main radicals for toluene degradation. In
contrast, • OH is not an important contributor since the
photocatalytic activity decreases slightly when the composite is
treated by IPA.
-
of toluene is attacked by the active species (h+, •O2 and •OH)
and completely oxidized to carboxyl group; 3) benzoic acid
breakage to generate oxalic acid and finally mineralized to CO2
and H2O during the reaction.[45-48]
Figure 13. Photocatalytic degradation of toluene on 4TiO2@U composite with
different kinds of scavengers.
-
To confirm the generation of •O2 in the reaction process,
- [49]
NBT is used as probe molecules to detect • O2 .
The
Figure S12 displays the in situ FT-IR spectra of UiO-66
during the photo-oxidation of toluene. The feature peaks of
toluene (2940, 2870, 1581 and 1506 cm-1) and new peaks,
such as benzaldehyde (1735, 1687, 1652 cm-1), benzoic acid
(1560 and 1542 cm-1), oxalic acid (1720, 1698 and 1423 cm-1)
and CO2 (2340 cm-1), can be all clearly found. The
characteristic peak intensity of intermediate products
(benzaldehyde, benzoic acid) on the surface of UiO-66 at the
range of 1800~1400 cm-1 are higher than that on 4TiO2@U
(Figure 12d and Table S4), suggesting that the stronger
adsorption affinity of intermediate products on UiO-66 surface.
Meanwhile, these phenomena also can be concluded that the
synergistic effect of the adsorption property of the UiO-66 and
the photocatalytic activity of TiO2 for toluene significantly
enhanced the photocatalytic activity, thus avoiding the
absorbance of NBT gradually decreases with the illumination
time, suggesting that •O2- radicals are generated on the surface
of 4TiO2@U because • O2 can react with NBT to form
diformazan under light irradiation (Figure S13a). These results
suggest that photoinduced electron can effectively transfer and
-
-
form • O2 under light conditions, resulting in superior
photocatalytic activity for organic pollutants oxidation.
Based on the experimental results above, a possible
mechanism for toluene oxidation is proposed in Scheme 1.
Under UV light irradiation, both TiO2 and UiO-66 can be excited
and generate electrons and holes in the conduction band (CB)
and valence band (VB), respectively. Owning to the intimate
interfacial contact between TiO2 and UiO-66, the
photogenerated electrons in the CB of TiO2 can directly transfer
into the VB of UiO-66. Additionally, the VB edge potential of
UiO-66 and TiO2 is higher than the oxidation potential of H2O/•
OH (2.7 eV vs NHE.). Therefore, some holes in the VB of
deposition
of
recalcitrant
degradation
intermediates
(carbonaceous residues). Besides, some studies have pointed
out that benzoic acid strongly adsorbs on the surface of the
catalyst, leading to the deactivation of photocatalyst.[43] Thus,
UiO-66 exhibits poor photocatalytic performance.
8
This article is protected by copyright. All rights reserved.

10.1002/cctc.202001466
ChemCatChem
FULL PAPER
catalyst transform water molecule into •OH. In addition, other
holes react directly with the toluene in reaction system.
Meanwhile, the CB potential of UiO-66 is more negative than
IR results reveal that the adsorbed toluene can be converted
into benzaldehyde, benzoic acid and oxalic acid gradually, and
decomposed into CO2 and H2O finally. The present work
provides an effective strategy to construct a high-performance
MOF based catalyst for the degradation of organic pollutants.
-
the potential energy of O2/•O2 (-0.3 eV vs. NHE),[29] thus
-
electrons can be captured by O2 to form •O2 . Therefore, the
possible reaction formulas for the photocatalytic oxidation of
toluene over TiO2@UiO-66 composites can be described as
follows:
4. Experimental Section
TiO2@UiO-66 + hv → h+ + e-
H2O/OH- (surface) + h+ → •OH
-
O2 + e- → •O2
4.1 Preparation of catalysts
C7H8 + •O2 /h+/•OH → C6H5CH2• → C6H5CH2OO• → C6H5CHO
-
→ C6H5COOH
Synthesis of TiO2@UiO-66: TiO2 nanoparticles were fabricated via
solvothermal method.[49] TiO2@UiO-66 composite was synthesized via
the hydrothermal method. In detail, ZrCl4 (0.2332 g) and H2BDC (0.1661
g) were dissolved in 50 mL of DMF under stirring. After that, 6 mL of
acetic acid was added. And then a certain amount of TiO2 (0.80, 1.60
and 2.40 g) was dispersed into the above mixture with stirring for 30 min.
The mixed solution was transferred into a 100 mL Teflon-lined stainless
steel autoclave and maintained at 120 oC for 24 h without stirring. After
cooling, the product was collected from the solution by centrifuging and
washing with DMF and methanol as well as dried under vacuum at 100
oC for 12 h. The composite was labelled as xTiO2@U (x=2, 4 and 6),
where x is the mass ration of TiO2 with respect to two important
precursors (ZrCl4 and H2BDC) of UiO-66.
-
C6H5COOH + •O2 /h+/•OH → H2C2O4 → CO2 + H2O.
Synthesis of TiO2@UiO-66-NH2: Similar procedure was used in the
preparation of the TiO2@UiO-66 but using 0.1812 g NH2-BDC instead of
0.1661 g H2BDC. The sample was named as 4TiO2@UN.
Synthesis of UiO-66: Similar procedure was used in the preparation
of the UiO-66 except that no TiO2 powder was added into the synthesis
mixture of TiO2@UiO-66.
Scheme 1. The proposed mechanism for the photocatalytic oxidation of
toluene on the TiO2@UiO-66 composite.
Synthesis of UiO-66-NH2: Similar procedures were used in the
preparation of the UiO-66 but using 0.1812 g NH2-BDC instead of
0.1661 g H2BDC.
3. Conclusion
For comparison, the mechanical mixing sample was prepared by
mixing the prepared 840 mg of TiO2 and 160 mg of as-prepared UiO-66
via grinding in the air at room temperature, and it was denoted as 4TiO2-
U-Mech. Solvent evaporation sample was also prepared by mixing of
the prepared 840 mg of TiO2 and 160 mg of pristine UiO-66 in 50 mL of
methanol, then stirred in fume hood until dryness and dried at 100 oC for
12 h, and it was denoted as 4TiO2-U-Evap.
In summary, TiO2@UiO-66 composite has been successfully
prepared by in situ solvothermal method and used for organic
pollutant (toluene, formaldehyde and RhB) degradations under
UV light irradiation. The TiO2@UiO-66 composite exhibits
higher photocatalytic activity for toluene and formaldehyde
oxidation than TiO2, UiO-66 and the composites prepared with
evaporation and mechanical mixing methods during a 720 min
of long-term evaluation under continuous flow system. The
composite also exhibits outstanding RhB removal efficiency in
wastewater. The improved photocatalytic activity of TiO2@UiO-
66 can be assigned to two main aspects. On one hand, the
composite possesses matched band structure and close
interfacial contact between UiO-66 and TiO2, which leads to
efficient separation and transfer of photoinduced carriers, thus
enhancing photocatalytic activity and CO2 selectivity. On the
other hand, the synergistic effect between UiO-66 and TiO2 in
the composite combines the adsorption and photocatalytic
oxidation of toluene, which not only can improve the adsorption
of toluene and desorption of CO2, but also has sufficient active
sites in the composite. The mechanism for toluene oxidation
implies that •O2- and h+ are the main active species. In situ FT-
4.2. Characterizations
All the catalysts were systematically characterized by XRD, FTIR,
SEM, TEM, UV-vis, XPS, PL, TPD, in situ FT-IR, photoelectrochemical
measurements and detection of reactive species. The detection
conditions of different characterizations are given in supporting
information.
4.3. Activity test
9
This article is protected by copyright. All rights reserved.

10.1002/cctc.202001466
ChemCatChem
FULL PAPER
[19] Z. X. Zhao, X. L. Ma, A. Kasik, Z. Li, Y. S. Lin, Ind. Eng. Chem. Res.
2012, 52, 1102-1108.
The photocatalytic oxidation of toluene and formaldehyde were
evaluated at room temperature in a continuous flow reactor.[21,50] The
initial concentration of toluene and formaldehyde are 25 ppm and 10
ppm, respectively. 100 mg of samples were used for each experiment
and the relative humidity was 60%.
[20] K. Epp, I. Luz, W. R. Heinz, A. Rapeyko, F. X. L. i. Xamena, R. A.
Fischer, ChemCatChem 2020, 12, 1720-1725.
[21] J. H. Zhang, Y. Hu, J. X. Qin, Z. X. Yang, M. L. Fu, Chem. Eng. J. 2020,
385, 123814-123826.
[22] P. Z. Yao, H. L. Liu, D. T. Wang, J. Y. Chen, G. Y. Li, T. C. An, J. Colloid
Inter. Sci. 2018, 522, 174-182.
The photocatalytic degradation of RhB was carried out in a home-
made reactor.[8] 20 mg of a photocatalyst was added to 100 mL of
solution containing 20 mg/L RhB.
[23] Z. G. Zhang, X. Li, B. Liu, Q. D. Zhao, G. Chen, RSC adv. 2016, 6, 4289-
4295.
[24] J. Kim, S. N. Kim, H. G. Jang, G. Seo, W. S. Ahn, Appl. Catal. A 2013,
453, 175-180.
[25] A. Crake, K. C. Christoforidis, A. Kafizas, S. Zafeiratos, C. Petit, Appl.
Catal. B 2017, 210, 131-140.
Acknowledgements
[26] X. J. Wang, X. L. Zhao, D. Q. Zhang, G. S Li, H. X. Li, Appl. Catal. B
2018, 228, 47-53.
This work was supported by National Natural Science
Foundation of China (21777047) and the Scientific Research
Project of Guangzhou City (201804020026).
[27] M. J. Katz, Z. J. Brown, Y. J. Colón, P. W. Siu, K. A. Scheidt, R. Q. Snurr,
J. T. Hupp, O. K. Farha, Chem. Commun. 2013, 49, 9449-9451.
[28] X. Liu, R. Dang, W. J. Dong, X. B. Huang, J. Tang, H. Y. Gao, G. Wang,
Appl. Catal. B 2017, 209: 506-513.
[29] X. Q. Xu, R. X. Liu, Y. H. Cui, X. X. Liang, C. Lei, S. Y. Meng, Y. L. Ma, Z.
Q. Lei, Z. W. Yang, Appl. Catal. B 2017, 210, 484-494.
[30] X. D. Zhang, Y. Yang, X. T. Lv, Y. X. Wang, N. Liu, D. Chen, L. F. Cui, J.
Hazard. Mater. 2019, 366, 140-150.
Conflict of Interest
[31] T. Lee, Y. H. Chang, H. L. Lee, CrystEngComm, 2017, 19, 426-441.
[32] A. A. Silahua-Pavón, C. G. Espinosa-González, F. Ortiz-Chi, J.
GpePacheco-Sosa, H. Pérez-Vidal, J. CarlosArévalo-Pérez, S.
Godavarthi, J. G. Torres-Torres, Catal. Commun. 2019, 129: 105723.
[33] Y. Su, Z. Zhang, H. Liu, Y. Wang, Appl. Catal. B 2017, 200, 448-457.
[34] S. Z. You, Y. Hu, X. C. Liu, C. H. Wei, Appl. Catal. B 2018, 232, 288-298.
[35] Y. C. Huang, B. Long, M. N. Tang, Z. B. Rui, M. S. Balogun, Y. X. Tong,
H. B. Ji, Appl. Catal. B 2016, 181, 779-787.
The authors declare no conflict of interest.
Keywords: TiO2@UiO-66 • VOCs • photocatalytic oxidation •
reaction mechanism • synergistic effect
[1] A. Chaudhary, S. Hellweg, Environ. Sci. Technol. 2014, 48, 14607-14614.
[2] D. Sarigiannis, S. P. Karakitsios, A. Gotti, I. Liakos, A. Katsoyiannis,
Environ. int. 2011, 37, 743-765.
[36] D. R. Sun, Y. H. Fu, W. J. Liu, L. Ye, D. K. Wang, L. Yang, X. Z. Fu, Z. H.
Li, Chem-Eur. J. 2013, 19, 14279-14285.
[3] H. Huang, Y. Xu, Q. Feng, D. Y. C. Leung, Catal. Sci. Technol. 2015, 5,
2649-2669.
[37] A. H. Mamaghani, F. Haghighat, C. S. Lee, Build. Environ. 2018, 138,
275-282.
[4] J. Fan, Q. M. Ren, S. P. Mo, Y. H. Sun, M. L. Fu, J. L. Wu, L. M. Chen, P.
R. Chen, D. Q. Ye, ChemCatChem, 2020, 12, 1046-1054.
[5] S. Weon, J. Choi, T. Park, W. Choi, Appl. Catal. B 2017, 205, 386-392.
[6] S. Weon, W. Choi, Environ. Sci. Technol. 2016, 50, 2556-2563.
[7] A. H. Mamaghani, F. Haghighat, C. S. Lee, Appl. Catal. B 2017, 203, 247-
269.
[38] Q. J. Geng, Q. M. Wang, B. Zhang. Ind. Eng. Chem. Res. 2012, 51,
15360-15373.
[39] O. Debono, F. Thevenet, P. Gravejat, V. Hequet, C. Raillard, L. Lecoq, N.
Locoge, Appl. Catal. B 2011, 106, 600-608.
[40] G. Y. Jiang, L. Zhang, Z. Zhao, X. Y. Zhou, A. J. Duan, C. M. Xu, J. S.
Gao, Appl. Catal. A 2008, 340, 176-182.
[8] G. Y. He, J. H. Zhang, Y. Hu, Z. G. Bai, C. H. Wei, Appl. Catal. B 2019,
250, 301-312.
[41] M. El-Roz, M. Kus, P. Cool, F. Thibault-Starzyk, J. Phys. Chem. C. 2012,
116, 13252-13263.
[9] X. Song, Y. Hu, M. M. Zheng, C. H. Wei, Appl. Catal. B 2016, 182, 587-
597.
[42] J. J. Sun, X. Y. Li, Q. D. Zhao, M. O. Tadé, S. M. Liu, J. Mater. Chem. A.
2015, 3, 21655-21663.
[10] H. Liu, B. Shen, M. Xing, J. Zhang, B. Tian, Res, Chem, Intermediat.
2016, 42, 3459-3471.
[43] M. D. Hernández-Alonso, I. Tejedor-Tejedor, J. M. Coronado, M. A.
Anderson, Appl. Catal. B 2011, 101, 283-293.
[11] F. He, A. Y. Meng, B. Cheng, W. K. Ho, J. G. Yu, Chinese J. Catal. 2020,
41, 9-20.
[44] J. Liu, P. L. Wang, W. Q. Qu, H. R. Li, L. Y. Shi, D. S. Zhang, Appl. Catal.
B 2019, 257, 117880-117888.
[12] S. Bao, J. Wan, B. Tian, J. Zhang, Res, Chem, Intermediat. 2018, 44,
6137-6149.
[45] W. Cui, J. Y. Li, L. Chen, X. A. Dong, H. Wang, J. P. Sheng, Y. J. Sun, Y.
Zhou, F. Dong, Sci. Bull. 2020, 65, 1626-1634.
[13] X. G. Wang, M. H. Sun, M. Muruganathan, Y. R. Zhang, L. Z. Zhang,
Appl. Catal. B 2020, 260, 118205-118215.
[46] R. M. Chen, J. Y. Li, J. P. Sheng, W. Cui, X. A. Dong, P. Chen, H. Wang,
Y. J. Sun, F. Dong, Appl. Catal. B 2020, 278, 119318.
[47] F. Zhang, X. Y. Li, Q. D. Zhao, Q. Z. Zhang, M. Tadé, S. M. Liu, J.
Colloid Inter. Sci. 2015, 457, 18-26.
[14] J. F. Qu, D. Y. Chen, N. J. Li, Q. F. Xu, H. Li, J. H. He, J. M. Lu, Appl.
Catal. B 2019, 256, 117877-117884.
[15] Y. J. Xin, Q. H. Chen, G. D. Zhang, J. Alloy. Compd. 2018, 751, 231-240.
[16] X. J. Zou, X. Y. Li, Q. D. Zhao, S. M. Liu, J. Colloid Inter. Sci. 2012, 383,
13-18.
[48] J. Y. Li, R. M. Chen, W. Cui, X. A. Dong, H. Wang, K. H. Kim, Y. H. Chu,
J. P. Sheng, Y. J. Sun, F. Dong, ACS Catal. 2020, 10(13), 7230-7239.
[49] J. X. Qin, J. Wang, J. J. Yang, Y. Hu, M. L. Fu, D. Q. Ye, Appl. Catal. B
2020, 267, 118667-118676.
[17] P. Falcaro, R. Ricco, A. Yazdi, I. Imaz, S. Furukawa, D. Maspoch, R.
Ameloot, J. D. Evans, C. J. Doonan, Coordin. Chem. Rev. 2016, 307,
237-254.
[50] Q. Q. Huang, Y. Hu, Y. Pei, J. H. Zhang, M. L. Fu, Appl. Catal. 2019, 259,
118106-118119.
[18] D. Alezi, Y. Belmabkhout, M. Suyetin, P. M. Bhatt, L. J. Weseliński, V.
Solovyeva, K. Adil, I. Spanopoulos, P. N. Trikalitis, A. Emwas, M.
Eddaoudi, J. Am. Chem. Soc. 2015, 137, 13308-13318.
10
This article is protected by copyright. All rights reserved.

10.1002/cctc.202001466
ChemCatChem
FULL PAPER
Entry for the Table of Contents
TiO2@UiO-66 composite synthesized by one-pot solvent-thermal method possesses the characteristic of tight contact interface
and matched band structure between TiO2 and UiO-66, which are conducive to the separation and transfer of charge carriers, thus
promoting the degradation of adsorbed toluene on UiO-66.
11
This article is protected by copyright. All rights reserved.