Metal-free amino-incorporated organosilica nanotubes for cooperative catalysis in the cycloaddition of CO2 to epoxides

Article abstract of DOI:10.1016/j.cattod.2018.07.004

The novel amino-incorporated benzene-bridging organosilica nanotubes (AM-NT) were used to efficiently catalyze the cycloaddition of CO₂ to epoxides, producing cyclic carbonates under mild conditions. The highest activity was achieved on AM_0.4-NT nanotubes with a pore diameter of ～7 nm and a length of ～60 nm in presence of tetrabutylammonium iodide (TBAI). The remarkably enhanced catalytic performance could be ascribed to the cooperative effect of the silanols as acid sites and the amino groups as basic sites, facilely generated in the channel, as well as the transport of substrates and products facilitated by the nanotubes with large pore diameters and short lengths as well as hydrophobicity. Moreover, the catalyst exhibited effective catalytic activity for a broad range of epoxides with a reasonable reusability.

Full text of DOI:10.1016/j.cattod.2018.07.004

Accepted Manuscript
Title: Metal-free amino-incorporated organosilica nanotubes
for cooperative catalysis in the cycloaddition of CO2 to
epoxides
Authors: Shengbo Zhang, Xiao Liu, Mei Li, Yan Wei, Gefei
Zhang, Jinyu Han, Xinli Zhu, Qingfeng Ge, Hua Wang
PII:
S0920-5861(18)30112-3
DOI:
Reference:
https://doi.org/10.1016/j.cattod.2018.07.004
CATTOD 11549
To appear in:
Catalysis Today
Received date:
Revised date:
Accepted date:
23-2-2018
10-5-2018
3-7-2018
Please cite this article as: Zhang S, Liu X, Li M, Wei Y, Zhang G, Han J,
Zhu X, Ge Q, Wang H, Metal-free amino-incorporated organosilica nanotubes for
cooperative catalysis in the cycloaddition of CO2 to epoxides, Catalysis Today (2018),
https://doi.org/10.1016/j.cattod.2018.07.004
This is a PDF file of an unedited manuscript that has been accepted for publication.
As a service to our customers we are providing this early version of the manuscript.
The manuscript will undergo copyediting, typesetting, and review of the resulting proof
before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that
apply to the journal pertain.

Metal-free amino-incorporated organosilica nanotubes for
cooperative catalysis in the cycloaddition of CO2 to epoxides
Shengbo Zhang,a,1 Xiao Liu,c,1 Mei Li,a Yan Wei,a Gefei Zhang,a Jinyu Han,a Xinli Zhu,a
Qingfeng Ge,a,b* Hua Wanga*
aKey Laboratory for Green Chemical Technology of the Ministry of Education, School of
Chemical Engineering and Technology, Collaborative Innovation Center of Chemical Science
and Engineering, Tianjin University, Tianjin 300072, P. R. China
bDepartment of Chemistry and Biochemistry, Southern Illinois University, Carbondale, IL 62901,
United States
cKey Laboratory of Pesticide & Chemical Biology of the Ministry of Education, College of
Chemistry, Central China Normal University, Wuhan 430079, P. R. China
E-mail: tjuwanghua@tju.edu.cn; E-mail: qge@chem.siu.edu
1 These authors contributed equally.
1

Graphic Abstract
Highlights


Novel amine-incorporated organosilica nanotubes with large-pore diameter and short-
channel were applied for the cycloaddition of CO2 to epoxides.
The remarkably enhanced catalytic performance could be ascribed to the cooperative effect
of the silanols and the –NH2 groups, facilely generated in the channel, as well as the
facilitated transport and the hydrophobicity.

The amine-incorporated organosilica nanotubes catalyst displayed enhanced catalytic
activities and recyclability.
Abstract: The novel amino-incorporated benzene-bridging organosilica nanotubes (AM-NT)
were used to efficiently catalyze the cycloaddition of CO2 to epoxides, producing cyclic
carbonates under mild conditions. The highest activity was achieved on AM0.4-NT nanotubes
with a pore diameter of ~7 nm and a length of ~60 nm in presence of tetrabutylammonium iodide
(TBAI). The remarkably enhanced catalytic performance could be ascribed to the cooperative
effect of the silanols as acid sites and the amino groups as basic sites, facilely generated in the
2

channel, as well as the transport of substrates and products facilitated by the nanotubes with large
pore diameters and short lengths as well as hydrophobicity. Moreover, the catalyst exhibited
effective catalytic activity for a broad range of epoxides with a reasonable reusability.
Keywords: cycloaddition of CO2 to epoxides; organosilica nanotubes; amine-incorporated;
cooperative catalysis.
1. Introduction
The increasing emission of carbon dioxide (CO2) has been linked to severe global warming
and attracted widespread attention in recent years [1-3]. In the context of carbon capture and
sequestration, several efficient routes have been developed for chemical fixation of CO2 in the
production of the value-added chemicals [4-9]. Cycloaddition of CO2 to epoxides to form cyclic
carbonates is one of the most promising pathways because of a 100% atom-economy. Cyclic
carbonates are widely used as green polar aprotic solvents, monomers for plastics and
pharmaceuticals, and electrolytes for lithium-ion batteries [10-13]. Homogeneous processes of
producing cyclic carbonate are limited by the loss of catalysts in recycling and high cost of
products separation. In contrast, processes using the heterogeneous catalysts, especially porous
materials such as zeolites [14-15], metal-organic frameworks (MOFs) [16-21], porous
materials/supported ionic liquids [22-25], and functional polymers [26-31] overcome those
limitations of the homogeneous processes.
Despite of enormous progress being made on the design and synthesis of efficient
heterogeneous catalysts for cyclic carbonates, the catalytic activity remains lower, especially for
epoxides with large molecular size, due mainly to the diffusion limit. For example, the highly
porous metal-organic framework incorporating metal sites and nitrogen-rich groups [17-19] and
3

a periodic mesoporous organosilica with a basic urea-derived framework (PMO-UDF) [32] have
been shown to catalyzed addition of CO2 to epoxides to produce cyclic carbonates. In particular,
those materials exhibited an excellent catalytic efficiency toward small molecular size epoxides.
Unfortunately, for epoxide with a large molecular size, the activity of those materails decreases
sharply, due to slow diffusion in small pores of MOFs (~1 nm in diameter) and PMO-UDF (~2
nm in diameter). Additionally, improvements of thermal and chemical stabilities are needed for
those materials as a practical catalyst. Eliminating metal active sites in the catalytic material will
likely make the process greener and more eco-friendly [16-31].
Organosilica nanotubes have been prepared from bridged organosilane precursors using a
sample micelle-templating approach. These nanotubes have several distinct advantages,
including large pore size, uniform surface silanols, being easily functionalized, controllable
hydrophobicity/hydrophilicity, high surface areas and structural stability [33-37]. The presence
of the silanol hydroxyl groups (-OH) can facilitate the ring opening of epoxide. In this case, the
hydroxyl group coordinates with the epoxide ring and polarize the C-O bond to form an activated
epoxide, which is able to facilely undergo ring-opening upon nucleophilic attacks by Br- or I-
[38-45]. Several research groups reported that the amino group (-NH2) can adsorb and activate
CO2 at ambient pressure [46-50]. Recently, we synthesized a novel solid mesoporous material by
one-pot, benzene-bridged organosilica nanotubes containing amino groups in the pore (AM-NT)
to support the AuPd nanoparticles for visible-light-driven hydrogen evolution [37]. The -OH and
-NH2 active sites can be facilely generated in the pore by assembling the corresponding
precursors during the framework construction. The acid-base pair, silanol and -NH2 functional
group in organosilica materials, are expected to function cooperatively to catalyze the
cycloaddition of CO2 to epoxides. Additionally, AM-NT is hydrophobic due to the presence of
4

benzene in the organosilica framework. The hydrophobicity is believed to favor the organic
transformations in an organic solvent [51-52]. In the presnt stduy, we use AM-NT as metal-free
solid catalysts with tetrabutylammonium iodide as a cocatalyst for coupling CO2 with various
epoxides. We found that very short AM0.4-NT with ~60 nm in length and ~7 nm in pore diameter
exhibited a high initial catalytic avtivity. Furthermore, amino-incorporated benzene-bridging
organosilica nanotubes show a reasonable catalytic activity for a broad range of substrates and
good reusability.
2. Experimental
2.1 Materials
1,4-bis(triethoxysilyl)benzene (BTEB) and triblock copolymer EO20PO70EO20 (Pluronic P123,
Mw = 5800) were purchased from Sigma-Aldrich Company Ltd. (U.S.A.). 3-
aminopropyltrimethoxysilane (97%), tetraethoxysilane (TEOS) and hexamethyldisilazane
(HMDS) were purchased from J&K. Other reagents were obtained from Shanghai Chemical
Reagent.
2.2 Synthesis of amino-incorporated organosilica nanotubes
Amine-incorporated organosilica nanotubes were synthesized according to the previous report
[37]. In a typical synthesis, 0.55 g of P123 and 1.75 g of KCl were dissolved in 150 mL 2 M HCl
solution at 38 °C with stirring for 2 h and followed by adding 2.1 mmol of 1,4-
bis(triethoxysilyl)benzene (BTEB) with vigorous stirring for an additional 12 h. Then 1.4 mmol
of 3-aminopropyltrimethoxysilane (APTMS) was added dropwise, and the mixture was stirred
for 24 h (The molar ratio of APTMS to the initial silane mixture was 0.4) before being
transferred to a PTFE hydrothermal reactor at 100 °C. After reacting for 24 h, the solid product
5

was recovered by filtration and followed by drying. Finally, the surfactant was extracted by
refluxing the sample in an acid-ethanol solution for 24 h. Deprotonation of the amine groups was
achieved by stirring the extracted samples in 0.01 M NaOH aqueous solution. The sample was
denoted as AM0.4-NT. For comparison, AM-NT samples with 0.1 and 0.2 molar fraction of
aminosilane were also synthesized, denoted as AM0.1-NT and AM0.2-NT, respectively.
2.3
Characterization
The nitrogen adsorption-desorption isotherms were collected on a Micromeritics Trisstar 3000
instrument at 77 K. The specific surface area was estimated according to the Brunauer–Emmett–
Teller model. Transmission electron microscopys (TEM) were carried out with a Philips Tecnai
13
G2 F20 system at 200 kV. Solid-state C cross polarization magic-angle spinning (CP MAS)
NMR spectra and 29Si MAS NMR spectra were collected on a 400 MHz instrument.
2.4
AM-NT-Catalyzed cycloaddition of CO2
In a typical experiment, a mixture of propylene epoxide (10 mmol), DMF (5 mL), CO2 (1.0
MPa), AM0.4-NT (65 mg for 0.067mmol N) and tetrabutylammonium iodide (TBAI) (0.1 mmol)
was added to a stainless steel autoclave equipped with an automatic stirrer and temperature
controlling system. The autoclave was flushed three times with CO2 and pressurized to 1.0 MPa
and kept at 70 °C for 10 h for reaction. After the reaction, the catalyst powder was filtered via an
organic membrane and the resulting liquid was analyzed by Bruker 456 gas chromatograph
equipped with a flame ionization detector (FID).
3.
Results and discussion
3.1 Synthesis of amino-incorporated organosilica nanotubes (AMx-NT).
6

The amino-incorporated organosilica nanotubes (AMx-NT) with different molar fractions of
APTMS were synthesized. According to the detailed characterization in our previous report [37],
the AMx-NT samples are composed of nanotubes with ~7 nm inner diameter and ~3 nm wall
thickness. The lengths of the nanotubes for AMx-NT can shortened by increasing the fraction of
APTMS. The AM0.4-NT has a length of ~60 nm, shorter than >100 nm nanotubes of AM0.1-NT
and AM0.2-NT. The incorporation of the –NH2 and –OH functional groups in the nanotubes has
29
13
been confirmed by the results of Si magic angle spinning (MAS) NMR, solid-state C cross
polarization magic-angle spinning (CP MAS) NMR and X-ray photoelectron spectroscopy (XPS)
analyses. Those characterizations consistently indicate that the silanols and the alkyl-NH2 groups
have been built in the nanotubes successfully.
3.2 AMx-NT-catalyzed cycloaddition of CO2 to epoxides.
Catalytic performances of as-prepared AMx-NT catalysts for the cycloaddition of CO2 to
propylene epoxide were evaluated at 70 °C and 1.0 MPa CO2 for 10 h. The results are shown in
Figure 1 and Table 1. The physical properties of the catalysts are listed in Table S1. As shown in
Table 1, only trace amount of cyclic carbonate was formed on AM0.1-NT without TBAI (Entry 1)
while only TBAI without catalysts gave a low conversion of 7.2% (Entry 2). Combining AMx-
NT and TBAI resulted in a significantly increased conversion (Entries 3-5). The best TOF of 80
h-1 (based on the converted amounts of propylene epoxide by per mmol N) was obtained on
AM0.4-NT. The remarkable enhancement of catalytic activity can be attributed to the effcient
ring-openning of propylene epoxide through a mechanism that is similar to that on the silica
supported ionic liquid [22-25]. In this case, the acidic surface silanol groups interact with the
activate propylene epoxide, which is subsequently attacked by a nucleophile I- from TBAI to
open the ring. Meanwhile, the amino groups and amine-silanol activate CO2 and contribute to the
7

overall enhancement of the catalytic performance. The function of -NH2 is revealed by the low
conversion of 10% when an amino-free NT is used (Figure 5c). Furthermore, both AM0.1-NT and
AM0.2-NT with longer lengths exhibited lower TOFs of 44 h-1 and 56 h-1, respectivly, than that
using AM0.4-NT as the catalyst. (Entries 3-4). These results demonstrate that short nanotube is
necessary for obtaining a high activity. This is expected as a short length enables more efficient
transport of reactants and products.
Figure 1. (a) Conversion of cycloaddition of CO2 to epoxide on AM0.1-NT, AM0.2-NT, AM0.4-NT. (b)
Conversion of cycloaddition of CO2 to epoxide on Gam-NT, NH2-MCM-41, NH2-SBA-15, NH2-SNT and
AM0.4-NT.
For comparison, the catalytic performane of Gam-NT prepared by post-grafting the
aminosilane on the organosilica nanotubes was tested. (Scheme S1, Figure 2a, Figures S1-S2).
The Gam-NT catalyst only gave a TOF of 19 h-1 (Entry 6), clearly smaller than those on AMx-
NT (Entries 3-5). Therefore, one-pot method is advantageous over the post-grafted one. To show
the hydrophobic effect on the catalytic performance, the aminosilane was immobilized on the
pure silica support using the one-pot method to prepare three catalysts, NH2-SBA-15 with 6.4 nm
pore (Figure 2b, Figures S3-S5), NH2-MCM-41 with 2.9 nm pore (Figure 2c, Figures S6-S7) and
8

NH2-SNT with 7.8 nm pore but without the bridged benzene in the nanotubes framework (Figure
2d, Figures S8-S9), respectively. All three catalysts exhibited lower TOFs of 30 h-1, 24 h-1 and 36
h-1 (Entries 7-9) than those of the AMx-NT series. These results showed that the longer
nanotubes with less hydrophobicity limit transport of the reactants and products through the
pores. In the case of NH2-MCM-41, small pore diameters cause diffusion limitation.
Additionally, amine-free organosilica nanotube (Entry 10) gave 22% conversion, much higher
than that of TBAI alone. It demonstrated that the silanol groups play an effective role in
activating epoxides.
Figure 2. The TEM images of (a) Gam-NT, (b) NH2-SBA-15, (c) NH2-MCM-41 and (d) NH2-SNT.
9

The above results demonstrate that the dual catalyst system AM0.4-NT with TBAI showed
much higher TOF than other tested catalysts. The enhanced activity can be attributed to effective
activation of CO2 and propylene epoxide through the cooperative catalysis of the acidic silanol,
basic amino groups in presence of a nucleophile I- anion, and the effective transport of the
reactant and product facilitated by the large-pore size, short pore length as well as
hydrophobicity of the pores.
Table 1. Cycloaddition of CO2 to epoxides with different catalysts.a
Entry
Catalysts
Pore size
(nm)
7.5
Co-catalyst
Conversion
TOFb
(h-1)
-
(%)
Traces
7.2
95
1
2
AM0.1-NT
-
-
-
TBAI
TBAI
TBAI
TBAI
TBAI
TBAI
TBAI
TBAI
TBAI
-
3
AM0.1-NT
AM0.2-NT
AM0.4-NT
Gam-NT
NH2-SBA-15
NH2-MCM-41
NH2-SNT
NT
7.5
44
56
80
19
30
24
36
-
4
7.3
99
5
6.8
99
6
6.5
67
7
6.4
85
8
2.9
79
9
7.8
90
10
7.9
22
aReaction conditions: substrate (10 mmol), solvent (DMF, 5 mL), catalysts (0.067 mmol N), TBAI (0.1 mmol),
b
1.0 MPa CO2, 70 °C, 10 h. TOF was calculated from the data within the first 1 h and according to the
following equation: TOF = mmolconverted propylene epoxide / (mmolN × h).
3.3 Effects of reaction conditions.
10

The effect of different reaction conditions such as CO2 pressure and reaction temperature on
propylene carbonate synthesis were investigated. As shown in Figure 3a, the CO2 pressure had a
significant impact on the conversion of propylene epoxide. The conversion of propylene epoxide
was dramatically increased from 60% to 98% with the increase of CO2 pressure from 0.2 MPa to
1.0 MPa, and remained nearly constant in the range of 1.0-3.0 MPa. However, further increasing
CO2 pressure to 4.0-5.0 MPa resulted in a lower conversion of 82% propylene epoxide. The
reason is that the exceedingly high CO2 pressure may block the interaction between the catalyst
and propylene epoxide, and cause a low concentration of propylene epoxide in the vicinity of the
catalyst (so-called dilution effect) [32,53-57]. Hence, a mild CO2 pressure of 1.0 MPa was used
in our experiment. The effect of reaction temperature was also investigated. As shown in Figure
3b, the conversion of propylene epoxide increases with the increasing reaction temperature in the
range of 25-70 °C and levels off upon further increasing reaction temperature to 120 °C.
Figure 3. Influence of reaction conditions of (a) CO2 pressure and (b) reaction temperature on propylene
epoxide conversion.
3.4 AM0.4-NT for cycloaddition of CO2 to other epoxides.
11

We further extend the application of the metal-free amino-functionalized nanotubes as
catalysts for cycloaddition of CO2 to substituted epoxides (Table 2). As shown in Table 2, high
activity and selectivity were achieved for various terminal epoxides with either electron-
withdrawing or electron-donating groups (Entries 1-7). Furthermore, the relatively less reactive
subustrates, cyclopentene oxide and cyclohexene oxide, were also applied (Entries 8-9).
However, the lower activities were observed due to the steric hindrance originated from the two
rings in the substrate [43]. Notably, AM0.4-NT could effectively catalyze the cycloaddition of
CO2 to epoxides with large molecular sizes (Entries 5-7), achieving a high conversion and
selectivity in 12 h. This reaction time is less than that reported on either MOFs or PMO [18, 19,
32] as the catalyst. Obviously, AM0.4-NT with a large pore diameter (~7 nm) and short length has
the advantage over those materials with small pore diameters (MOFs ~ 1 nm and PMO ~ 2 nm).
Table 2. Cycloaddition of CO2 to various epoxides catalyzed by AM0.4-NT.a
Entry
Substrate
Product
Conversion/%
Selectivity/%
O
O
1
98
99
O
O
O
O
O
O
O
2
3
4
5
6
96
99
95
95
92
99
99
99
99
99
O
O
O
Cl
Cl
O
O
O
O
O
O
O
O
Cl
Cl
O
O
O
O
Br
Br
12

7
8
9
90
70
74
99
92
96
aReaction conditions: substrate (10 mmol), solvent (DMF, 5 mL), AM0.4-NT (65 mg), TBAI (0.1 mmol), 1.0
MPa CO2, 70 °C, 12 h.
3.5 Reusability of AM0.4-NT in catalytic cycloaddition of CO2 to propylene epoxide.
The reusability experiments were performed at 6 h intervals to confirm the stability of the
AM0.4-NT under 70 °C and 1 MPa. After the reaction, the AM0.4-NT was recovered by filtration
and reused for the next run. As shown in Figure 4a, there was no significant decrease in
conversion (>92%) and selectivity (99% for propylene carbonate) after the 6th cycle. Furthermore,
13
the analysis of the recovered catalyst by TEM, nitrogen adsorption-desorption and C CP MAS
NMR (Figure 4b,c,d) indicated the structure and the composition were maintained after six
cycles. These results indicate that AM0.4-NT has an excellent reusability.
13

Figure 4. (a) The recycling performance of AM0.4-NT for cycloaddition of CO2 to epoxide; (b) The TEM
13
image, (c) Nitrogen adsorption-desorption isotherms and (d) C CP MAS NMR spectrum of AM0.4-NT after
the 6th reaction.
3.6 Reaction mechanism
Based on the present results and previous reports [27, 43, 53-57], a possible mechanism can be
proposed for the cycloaddition of CO2 to epoxides to form cyclic carbonates on the AMx-NT
catalysts (Scheme 1). Initially, the acidic silanols uniformly built in the pores, which act as the
proton donors to form hydrogen bonds with the oxygen atoms of the epoxides and help to
polarize the C-O bond. Subsequently, the nucleophilic I- anion attacks the less hindered -carbon
atom of epoxide to open the epoxy ring. Silanol-NH2 interaction help to adsorb and activate CO2
as well as facilitate coupling of the activated CO2 with the ring-opened intermediate to form the
carbonate intermediate. Finally, the intramolecular ring-closure occurs to generate the cyclic
carbonate, liberating the AM0.4-NT and TBAI catalysts. The cooperative effect of silanol groups,
14

-NH2 groups and co-catalyst TBAI enables the reaction to proceed effectively under mild
conditions.
Scheme 1. Proposed reaction mechanism for the AM0.4-NT-catalyzed cycloaddition of CO2 to epoxides.
Herenin, as shown schematically in Figure 5a, AM0.4-NT-Me, i.e. the silanols of AM0.4-NT
were capped by the trimethylsilyl [-Si(CH3)3] groups, was utilized to illustrate the cooperative
effetct between the -NH2 groups and the silanols. Figure 5b shows the 29Si MAS NMR spectrum
of the AM0.4-NT and AM0.4-NT-Me. For AM0.4-NT-Me, a new peak at 15 ppm appears due to
1
the trimethylsilane group [-Si(CH3)3], and the peaks of silicon species T [SiC(OH)2(OSi)] and
3
2T [SiC(OH)(OSi)2] were significantly weakened and even disappeared, while the peak of T
[SiC(OSi)3] was enhanced. These results support a successful capping of silanol groups.
According to the results of the controlled experiments conducted under 1.0 MPa CO2 and 70 °C
for 5 hours (Figure 5c), the pure organosilica nanotubes without amino functional groups (NT)
exhibited a lower catalytic activity (10% conversion after 5 h), indicating the critical role of the -
15

NH2 groups for cycloaddition reaction. Furthermore, the AM0.4-NT-Me exhibited a lower
catalytic activity (only 36% conversion after 5 h) than AM0.4-NT in the absence of the -OH
groups. These results confirm that the -NH2 groups (basic sites) function synergetically with
silanols (acidic sites) to achieve a high activity for the activation of the epoxide as well as CO2
under mild conditions.
29
Figure 5. (a) The end-capped route of AM0.4-NT, (b) Si MAS NMR spectrum of the AM0.4-NT and AM0.4-
NT-Me and (c) catalytic activity of NT, AM0.4-NT and AM0.4-NT-Me. Reaction conditions: substrate (10
mmol), solvent (DMF, 5 mL), TBAI (0.1 mmol), 1.0 MPa CO2, 70 °C, 5 h.
4. Conclusions
Novel amino-incorporated organosilica nanotubes with large pore diameter and short pore length
were successfully applied for catalytic CO2 conversion in the production of the cyclic carbonates.
AM0.4-NT in combination with TBAI displayed a remarkable catalytic activity and reusability as
compared with other amino-functionalized heterogeneous catalysts. The present study
demonstrated that a cooperative mechanism between the acidic hydroxyls of silanols and basic -
16

NH2 groups from the alkyl -NH2 groups is in action for an enhanced catalytic activity.
Furthermore, the nanotubes with short lengths and large diameters efficiently reduce the
diffusion limitation and improve the reactivity. We also demonstrated that the AM04-NT catalyst
is effective for CO2 reaction with a broad range of epoxides. Although the functionalized
organosilica nanotubes were only tested for the cycloaddition reaction, their application as solid
catalysts in metal-free catalysis involving organic reagents is of great potentials.
Acknowledgments
We thank instrumental analysis center of Tianjin University for assistance with TEM and NMR
analysis. This work was supported by the National Key Research and Development Program of
China (2016YFB0600900) and the National Natural Sciences Foundation of China (Grant
No.21576204, 21373148, 21206117 and U1662109).
References
[1]
S. J. Datta, C. Khumnoon, Z. H. Lee, W. K. Moon, S. Docao, T. H. Nguyen, I. C.
Hwang, D. Moon, P. Oleynikov, O. Terasaki, K. B. Yoon, Science 350 (2015)
302–306.
[2]
[3]
R. S. Haszeldine, Science 325 (2009) 1647–1652.
E. S. Sanz-Pérez, C. R. Murdock, S. A. Didas, C. W. Jones, Chem. Rev. 116 (2016)
11840–11876.
[4]
[5]
X. B. Lu, D. J. Darensbourg, Chem. Soc. Rev. 41 (2012) 1462-1484.
X. C. Kang, Q. G. Zhu, X. F. Sun, J. Y. Hu, J. L. Zhang, Z. M. Liu, B. X. Han,
Chem. Sci., 7 (2016) 266–273.
[6]
[7]
A. Goeppert, M. Czaun, G. K. S. Prakash, G. A. Olah, Energy Environ. Sci., 5
(2012) 7833–7853.
B. Yu, J.-N. Xie, C.-L. Zhong, W. Li, L.-N. He, ACS Catal, 5 (2015) 3940-3944.
17

[8]
X. H. Liu, J. G. Ma, Z. Niu, G. M. Yang, P. Cheng, Angew. Chem. Int. Ed. 54
(2015) 988-991.
[9]
Q.-W. Song, Z.-H. Zhou, L.-N. He, Green Chem., 19 (2017) 3707-3728.
D. J. Darensbourg, Chem. Rev., 107 (2007) 2388–2410.
A. Decortes, A. Castilla, A. Kleij, Angew. Chem. Int. Ed. 2010, 49, 9822-9837.
[10]
[11]
[12] J. Wang, Y. Zhang, Green Chem., 18 (2016) 5248-5253.
[13] M. North, R. Pasquale, C. Young, Green Chem., 12 (2010) 1514–1539.
[14] J. Dong, P. Cui, P. F. Shi, P. Cheng, B. Zhao, J. Am. Chem. Soc. 137 (2015)
15988-15991.
[15] T. H. Bae, M. R. Hudson, J. A. Mason, W. L. Queen, J. J. Dutton, K. Sumida, K. J.
Micklash, S. S. Kaye, C. M. Brown, J. R. Long, Energy Environ. Sci. 6 (2013)
128–138.
[16] T. He, B. Ni, X. Xu, H. Li, H. Lin, W. Yuan, J. Luo, W. Hu, X. Wang, ACS Appl.
Mater. Interfaces, 9 (2017) 17969-17976.
[17] R. Zou, P. Z. Li, Y. F. Zeng, J. Liu, R. Zhao, H. Duan, Z. Luo, J. G. Wang, R. Zou,
Y. Zhao, Small, 12 (2016) 2334-2343.
[18] P. Z. Li, X. J. Wang, J. Liu, J. S. Lim, R. Zou, Y. Zhao, J. Am. Chem. Soc. 138
(2016) 2142-2145.
[19] Y.-H. Han, Z.-Y. Zhou, C.-B. Tian, S.-W. Du, Green Chem., 18 (2016) 4086-4091.
[20] W. Y. Gao, Y. Chen, Y. Niu, K. Williams, L. Cash, P. J. Perez, L. Wojtas, J. Cai,
Y. S. Chen, S. Q. Ma, Angew. Chem. Int. Ed. 53 (2014) 2615-2619.
[21] Z. R. Jiang, H. W. Wang, Y. L. Hu, J. L. Lu, H. L. Jiang, ChemSusChem 8 (2015)
878–885.
[22] L. G. Ding, B. J. Yao, W. L. Jiang, J. T. Li, Q. J. Fu, Y. A. Li, Z. H. Liu, J. P. Ma,
Y. B. Dong, Inorg. Chem, 56 (2017) 2337-2344.
[23] W. Wang, C. Li, L. Yan, Y. Wang, M. Jiang, Y. Ding, ACS Catal, 6 (2016) 6091-
6100.
[24] J. Tharun, K.-M. Bhin, R. Roshan, D. W. Kim, A. C. Kathalikkattil, R. Babu, H. Y.
Ahn, Y. S. Won, D.-W. Park, Green Chem., 18 (2016) 2479-2487.
[25] S. M. Sadeghzadeh, Green Chem., 17 (2015) 3059-3066.
18

[26] Y. Du, H. Yang, S. Wan, Y. Jin, W. Zhang, J. Mater. Chem. A, 5 (2017) 9163-
9168.
[27] Q. Sun, B. Aguila, J. Perman, N. Nguyen, S. Ma, J. Am. Chem. Soc, 138 (2016)
15790-15796.
[28] G. Ji, Z. Yang, H. Zhang, Y. Zhao, B. Yu, Z. Ma, Z. Liu, Angew. Chem. Int. Ed.,
55 (2016) 9685-9689.
[29] Z. Dai, Q. Sun, X. Liu, C. Bian, Q. Wu, S. Pan, L. Wang, X. Meng, F. Deng, F.-S.
Xiao, J. Catal, 338 (2016) 202-209.
[30] J. Wang, J. G. Wei Yang, G. Yi, Y. Zhang, Chem. Commun, 51 (2015) 15708-
15711.
[31] Y. Xie, T. T. Wang, X. H. Liu, K. Zou, W. Q. Deng, Nat. Commun, 4 (2013)
1960-1966.
[32] M. Liu, X. Lu, L. Shi, F. Wang, J. Sun, ChemSusChem, 10 (2017) 1110-1119.
[33] X. Liu, X. B. Li, Z. Guan, J. Liu, J. Zhao, Y. Yang, Q. H. Yang, Chem. Commun.,
47 (2011) 8073-8075.
[34] S. Zhang, H. Wang, M. Li, J. Han, X. Liu, J. Gong, Chem. Sci., 8 (2017) 4489-
4496.
[35] S. Zhang, H. Wang, M. Li, J. Han, S. Inagaki, X. Liu, Dalton Trans., 46 (2017)
9369-9374.
[36] X. Liu, Y. Goto, Y. Maegawa, T. Ohsuna, S. Inagaki, APL Mater., 2 (2014)
113308-113314.
[37] S. Zhang, H. Wang, L. Tang, M. Li, J. Tian, Y. Cui, J. Han, X. Zhu, X. Liu, Appl.
Catal. B Environ. 220 (2018) 303-313.
[38] J. Wang and Y. Zhang, ACS Catal, 6 (2016) 4871-4876.
[39] W. Wang, C. Li, L. Yan, Y. Wang, M. Jiang and Y. Ding, ACS Catal, 6 (2016)
6091-6100.
[40] W.-H. Zhang, P.-P. He, S. Wu, J. Xu, Y. Li, G. Zhang, X.-Y. Wei, Appl. Catal. A
Gen, 509 (2016) 111-117.
[41] X.-D. Lang, Y.-C. Yu, L.-N. He, J.Mol. Catal. A Chem, 420 (2016) 208-215.
[42] J. Sun, J. Wang, W. Cheng, J. Zhang, X. Li, S. Zhang and Y. She, Green Chem, 14
(2012) 654-660.
19

[43] V. B. Saptal, T. Sasaki, K. Harada, D. Nishio-Hamane, B. M. Bhanage,
ChemSusChem, 9 (2016) 644-650.
[44] T. Takahashi, T. Watahiki, S. Kitazume, H. Yasuda and T. Sakakura, Chem.
Commun, 0 (2006) 1664-1666.
[45] A. M. Hardman-Baldwin and A. E. Mattson, ChemSusChem, 7 (2014) 3275-3278.
[46] R. Srivastava, D. Srinivas, P. Ratnasamy, Micropor. Mesopor. Mater. 90 (2006)
314–326.
[47] S-M. Hong, S. H. Kim, K. B. Lee, Energy Fuels, 27 (2013) 3358-3363.
[48] T. C. dos Santos, S. Bourrelly, P. L. Llewellyn, J. W. Carneiro, C. M. Ronconi,
Phys. Chem. Chem. Phys, 17 (2015) 11095-11102.
[49] T. H. Nguyen, S. Kim, M. Yoon, T. H. Bae, ChemSusChem, 9 (2016) 455-461.
[50] G. S. Foo, J. J. Lee, C-H. Chen, S. E. Hayes, C. Sievers, C. W. Jones,
ChemSusChem, 10 (2017) 266-276.
[51] D. Kim, D. W. Kim, O. Buyukcakir, M.-K. Kim, K. Polychronopoulou, A. Coskun,
Adv. Funct. Mater, 27 (2017) 1700706-1700713.
[52] J. Sun, H. Wang, X. Gao, X. Zhu, Q. Ge, X. Liu, J. Han, Micropor. Mesopor.
Mater., 247 (2017) 1-8.
[53] Z.-Z. Yang, L.-N. He, C.-X. Miao, S. Chanfreau, Adv. Synth. Catal, 352 (2010)
2233-2240.
[54] J.-Q. Wang, D.-L. Kong, J.-Y. Chen, F. Cai, L.-N. He, J. Mol. Catal. A, 249 (2006)
143-148.
[55] M. Liu, J. Lan, L. Liang, J. Sun and M. Arai, J. Catal, 347 (2017) 138-147.
[56] H. Li, C. Li, J. Chen, L. Liu, Q. Yang, Chem. Asian J, 12 (2017) 1095-1103.
[57] S. Jayakumar, H. Li, Y. Zhao, J. Chen, Q. Yang, Chem. Asian J, 12 (2017) 577-
585.
20