Novel hydrazine-bridged covalent triazine polymer for CO2 capture and catalytic conversion

Article abstract of DOI:10.1016/S1872-2067(18)63040-2

Carbon dioxide (CO₂) capture and catalytic conversion has become an attractive and challenging strategy for CO₂ utilization since it is an abundant, inexpensive, and renewable C1 resource and a main greenhouse gas. Herein, a novel hydrazine-bridged covalent triazine polymer (HB-CTP) was first designed and synthesized through simple polymerization of cyanuric chloride with 2,4,6-trihydrazinyl-1,3,5-triazine. The resultant HB-CTP exhibited good CO₂ capture capacity (8.2 wt%, 0 °C, and 0.1 MPa) as well as satisfactory recyclability after five consecutive adsorption-desorption cycles. Such a polymer was subsequently employed as a metal-free heterogeneous catalyst for the cyclo-addition of CO₂ with various epoxides under mild and solvent-free conditions, affording cyclic carbonates with good to excellent yields (67%–99%) and high functional-group tolerance. The incorporation of hydrazine linkages into HB-CTP's architecture was suggested to play the key role in activating epoxides through hydrogen bonding. Moreover, HB-CTP can be reused at least five times without significant loss of its catalytic activity.

Full text of DOI:10.1016/S1872-2067(18)63040-2

Chinese Journal of Catalysis 39 (2018) 1320–1328
a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c h n j c
Article (Special Column on the 15th International Conference on Carbon Dioxide Utilization (ICCDU XV))
Novel hydrazine‐bridged covalent triazine polymer for CO2 capture
and catalytic conversion
Anhua Liu *, Jinju Zhang, Xiaobing Lv
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, Liaoning, China
A R T I C L E I N F O
A B S T R A C T
Article history:
Carbon dioxide (CO2) capture and catalytic conversion has become an attractive and challenging
strategy for CO2 utilization since it is an abundant, inexpensive, and renewable C1 resource and a
main greenhouse gas. Herein, a novel hydrazine‐bridged covalent triazine polymer (HB‐CTP) was
first designed and synthesized through simple polymerization of cyanuric chloride with
2,4,6‐trihydrazinyl‐1,3,5‐triazine. The resultant HB‐CTP exhibited good CO2 capture capacity (8.2
wt%, 0 °C, and 0.1 MPa) as well as satisfactory recyclability after five consecutive adsorp‐
tion‐desorption cycles. Such a polymer was subsequently employed as a metal‐free heterogeneous
catalyst for the cyclo‐addition of CO2 with various epoxides under mild and solvent‐free conditions,
affording cyclic carbonates with good to excellent yields (67%–99%) and high functional‐group
tolerance. The incorporation of hydrazine linkages into HB‐CTP's architecture was suggested to play
the key role in activating epoxides through hydrogen bonding. Moreover, HB‐CTP can be reused at
least five times without significant loss of its catalytic activity.
Received 5 January 2018
Accepted 2 February 2018
Published 5 August 2018
Keywords:
Covalent triazine polymer
Capture
Catalysis
Carbon dioxide
Cyclic carbonate
© 2018, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.
Published by Elsevier B.V. All rights reserved.
1. Introduction
from insufficient long‐term stability and/or deactivation by
moisture [9–12]. Notably, porous polymers, with the ad‐
Nowadays, carbon dioxide (CO2) capture and sequential
catalytic conversion has been rationally proposed and de‐
ployed to address the issue of excessive CO2 emission, as it is a
nontoxic, easily available, and sustainable C1 building block in
organic synthesis and a greenhouse gas that causes global
warming and environmental crises [1–3]. In this context, a di‐
versity of bifunctional materials with ordered porosity and
efficient catalytic sites has been developed, such as met‐
al‐organic frameworks (MOFs), zeolites, and porous carbons
[4–6]. Among these, MOFs and zeolites have shown excellent
CO2 capture performance due to the presence of metal cations,
as well as donor ligands and polar functional sites, within the
structure [7,8]. However, their practical applications suffer
vantages of high stability toward heat and humidity, as well as
low density and metal‐free features, have been shown to be
feasible and powerful as solid adsorbents for CO2 capture and
heterogeneous catalysts for CO2 conversion [13,14]. Therefore,
the development of reliable technologies for CO2 capture and
conversion by such organic materials is certainly attractive and
promising.
The 1,3,5‐triazine moiety possesses a nitrogen‐rich feature,
as well as planar, rigid, and high‐symmetry structural charac‐
teristics, rendering it desirable for the construction of extended
CO2‐specific networks with permanent porosity [15,16].
Meanwhile, as one commercial available industrial chemical,
cyanuric chloride (CC) is the chlorinated derivative of triazine.
* Corresponding author. Tel/Fax: +86‐411‐84986257; E‐mail: ahliu@dlut.edu.cn
This work was supported by the National Natural Science Foundation of China (21406025), the China Postdoctoral Science Foundation
(2014M551067), and the Start‐Up Foundation of Dalian University of Technology (DUT13RC(3)58).
DOI: 10.1016/S1872‐2067(18)63040‐2 | http://www.sciencedirect.com/science/journal/18722067 | Chin. J. Catal., Vol. 39, No. 8, August 2018

Anhua Liu et al. / Chinese Journal of Catalysis 39 (2018) 1320–1328
1321
Owing to the electron‐deficient nature of carbons residing in
the triazine ring, CC has been widely applied in the construc‐
tion of porous triazine polymers by electrophilic substitution of
its chlorine atoms with different nucleophiles [17–19]. For in‐
stance, porous covalent organic polymers from reaction of CC
with piperazine have been devised, with CO2 adsorption capac‐
ities up to 5616 mg/g at 65 °C and 20.0 MPa, which have been
proved to be stable in boiling water for at least 1 week [20].
Porous sulfur‐bridged covalent organic polymers derived from
CC and 1,3,5‐benzenetrithiol could also provide up to 3294
mg/g of CO2 at 45 °C and 20.0 MPa, while being highly stable
against heating up to 400 °C [21]. In addition, ferro‐
cene‐functionalized microporous aromatic polymers were
synthesized by a one‐step Friedel‐Crafts reaction of ferrocene
and CC and have been shown to have a good CO2 adsorption
capability of 16.9 wt% at 0 °C and 0.1 MPa [22].
However, although chemical fixation of CO2 into val‐
ue‐added chemicals has been a long‐sought goal in both aca‐
demia and industry, the inherent thermodynamic stability and
kinetic inertness of CO2 pose a challenge for its chemical con‐
version under industrially viable conditions [23,24]. In order to
overcome this obstacle, employment of high‐energy starting
materials seems to be the wisest choice for utilization of inac‐
tive CO2 as a reactant. Therefore, the atom‐economical reaction
involving the cyclo‐addition of CO2 with epoxides to render
five‐membered cyclic carbonates has been intensively studied
[25–30]. Among the variety of catalysts developed, it is worth
mentioning that porous organic polymers have been demon‐
strated as recyclable organocatalysts for this transformation
[31–35]. However, the reaction protocols involving such poly‐
mers as heterogeneous catalysts often need high temperature
[31], solvents [32,33], and/or transition‐metal components
[34,35] to enhance their reactivity. Hence, polymer‐type met‐
al‐free catalysts that can operate under mild and solvent‐free
conditions are still in demand.
CO2 adsorbent but also an active and recyclable catalyst for
cyclo‐addition of CO2 with various epoxides to afford cyclic
carbonates at high efficiency. Hence, this work provides a facile
method for the first synthesis of a hydrazine‐bridged covalent
triazine polymer, which shows promising applications in CO2
capture and catalytic conversion.
2. Experimental
2.1. Chemicals
CO2 (99.999%) was used as received without further
purification. The 1,4‐dioxane was distilled from sodium/
benzophenone under N2. CC was purchased from J&K Scientific
(USA). Hydrazine hydrate was acquired from Alfa Aesar of
ThermoFisher Scientific (USA). Tetra‐n‐butylammonium
bromide (TBAB) was obtained commercially from Tianjin
Guangfu Fine Chemical Research Institute (China). 2,4,6‐
trihydrazinyl‐1,3,5‐triazine was synthesized according to the
established method [38]. Glycidyl propargyl ether and
4‐(2,3‐epoxypropyl)‐morpholine were prepared by coupling a
reaction of corresponding terminal propargylic alcohol or
morpholine with epichlorohydrin according to the literature
methods with modifications [39,40]. Other epoxides and the
remaining reagents were obtained commercially and used
without further purification.
2.2. Characterization
Nuclear‐magnetic‐resonance (NMR) spectra were recorded
on a Bruker AdvanceII 400M‐type spectrometer. Fourier‐
transform infrared (FTIR) spectroscopy was measured using a
Nicolet NEXUS FTIR spectrophotometer. Thermal gravimetric
analysis (TGA) was carried out by a Mettler Toledo TGA2
STAR* SYSTEM under a N2 atmosphere with a ramp rate of 10
°C/min. Elemental analysis was determined with an Elementar
Vario EL III elemental analyzer. Solid‐state 13C CP/MAS NMR
Herein, a novel hydrazine‐bridged covalent triazine polymer
(HB‐CTP) was designed and synthesized through a simple nu‐
cleophilic substitution reaction of 2,4,6‐trihydrazinyl‐1,3,5‐
triazine with CC promoted by sodium carbonate at 110 °C, as
shown in Scheme 1. This new material was devised to acquire
two outstanding advantages for CO2 capture and conversion:
(1) numerous triazine units to facilitate the reversible adsorp‐
tion of CO2 through their basic nitrogen sites that decorate the
inside of the material’s pores and (2) massive hydrazine moie‐
ties activated by electron‐deficient triazines to coordinate with
the substrates by formation of hydrogen bonds [33,36,37]. In‐
deed, HB‐CTP was discovered to be not only a viable and stable
spectra were recorded on
spectrometer. X‐ray powder diffraction (XRD) measurements
were performed on Rigaku D/MAX 2400 X‐ray
a Varian Infinity‐Plus 400
a
diffractometer. Adsorption‐desorption measurements for N2
and CO2 were conducted on a Quantachrome Autosorb iQ2
apparatus. The Brunauer‐Emmett‐Teller (BET) method was
used to calculate the specific surface area. Scanning electron
microscopy (SEM) investigations were performed on a Hitachi
UHR FE‐SEM SU8200 instrument. Transmission electron
microscopy (TEM) images were obtained on a FEI TF30
Scheme 1. Synthesis of HB‐CTP.

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Anhua Liu et al. / Chinese Journal of Catalysis 39 (2018) 1320–1328
apparatus.
4‐hexyl‐1,3‐dioxolan‐2‐one (2g). 1H NMR (400 MHz, CDCl3):
δ = 4.83–4.66 (m, 1H), 4.51 (t, J = 8.0 Hz, 1H), 4.06 (t, J = 8.0 Hz,
1H), 1.81–1.63 (m, 2H), 1.46–1.29 (m, 8H), 0.88 (t, J = 6.4 Hz,
3H). 13C NMR (100 MHz, CDCl3): δ = 155.1, 77.1, 69.4, 33.9, 31.5,
28.8, 24.3, 22.5, and 14.0.
2.3. Catalyst preparation
In a Schlenk apparatus under dry nitrogen atmosphere,
sodium carbonate (18 mmol, 1.91 g), CC (3 mmol, 0.55 g), and
2,4,6‐trihydrazinyl‐1,3,5‐triazine (3 mmol, 0.51 g) was added to
1,4‐dioxane (20 mL) at room temperature. The above mixture
was stirred at room temperature for 6 h and then at 110 °C for
48 h. Afterwards, the light yellow precipitate was collected by
filtration and washed consecutively with dimethylformamide,
water, and methanol. Finally, the quantitatively yielded
product, designated HB‐CTP, was dried at 120 °C under
vacuum for 24 h. Elemental analysis results were as follows:
calculated value (%) N 63.78, C 33.42, H 2.80; found value (%)
N 60.75, C 27.89, H 2.65.
1
4‐(methoxymethyl)‐1,3‐dioxolan‐2‐one (2h). H NMR (400
MHz, CDCl3): δ = 4.81–4.77 (m, 1H), 4.48 (t, J = 8.4 Hz, 1H),
4.43–4.37 (m, 1H), 3.65–3.52 (m, 2H), 3.40 (s, 3H). 13C NMR
(100 MHz, CDCl3): δ = 155.1, 75.2, 71.5, 66.3, and 59.7.
4‐(isopropoxymethyl)‐1,3‐dioxolan‐2‐one (2i). 1H NMR
(400 MHz, CDCl3): δ = 4.80–4.77 (m, 1H), 4.48 (t, J = 8.4 Hz, 1H),
4.40–4.37 (m, 1H), 3.67–3.59 (m, 3H), 1.16 (d, J = 6.0 Hz, 6H).
13C NMR (100 MHz, CDCl3): δ = 155.2, 75.4, 72.8, 67.1, 66.4,
59.7, 21.9, and 21.8.
4‐(butoxymethyl)‐1,3‐dioxolan‐2‐one (2j). 1H NMR (400
MHz, CDCl3): δ = 4.82–4.76 (m, 1H), 4.47 (t, J = 8.4 Hz, 1H),
4.38–4.35 (m, 1H), 3.67–3.56 (m, 2H), 3.49 (d, J = 6.4 Hz, 2H),
1.57–1.50 (m, 2H), 1.38–1.29 (m, 2H), 0.89 (d, J = 7.6 Hz, 3H).
13C NMR (100 MHz, CDCl3): δ = 155.1, 75.2, 71.9, 69.7, 66.4,
31.6, 19.2, and 13.9.
2.4. General procedure for the cyclo‐addition reaction
A 15‐mL oven‐dried autoclave containing a magnetic stir
bar was charged with a corresponding epoxide (10 mmol),
HB‐CTP (50 mg), and TBAB (0.5 mmol, 0.16 g). The autoclave
was then purged with CO2 three times. The sealed autoclave
was pressurized to 2 MPa CO2 and continuously stirred at 80 °C
for 12 h. Afterwards, the autoclave was cooled to room
temperature, and the remaining CO2 was vented slowly. Yields
of the target products were determined by 1H NMR with
1,5‐dichloro‐2,4‐dinitrobenzene as an internal standard.
4‐((dodecyloxy)methyl)‐1,3‐dioxolan‐2‐one (2k). 1H NMR
(400 MHz, CDCl3): δ = 4.82–4.76 (m, 1H), 4.48 (t, J = 8.0 Hz, 1H),
4.40–4.36 (m, 1H), 3.67–3.58 (m, 2H), 3.49 (d, J = 6.8 Hz, 2H),
1.59–1.52 (m, 2H), 1.25 (m, 18H), 0.87 (d, J = 6.8 Hz, 3H). 13C
NMR (100 MHz, CDCl3): δ = 155.1, 75.2, 72.4, 69.8, 66.5, 32.0,
29.8, 29.8, 29.7, 29.7, 29.6, 29.5, 29.5, 26.1, 22.8, and 14.2.
4‐(phenoxymethyl)‐1,3‐dioxolan‐2‐one (2l). 1H NMR (400
MHz, CDCl3): δ = 7.33–7.29 (m, 2H), 7.02 (t, J = 7.4 Hz, 1H), 6.92
(d, J = 8.0 Hz, 2H), 5.06–5.00 (m, 1H), 4.62 (t, J = 8.4 Hz, 1H),
4.54 (dd, J = 8.5 and 5.9 Hz, 1H), 4.24 (dd, J = 10.5 and 4.4 Hz,
1H), 4.16 (dd, J = 10.5 and 3.6 Hz, 1H). 13C NMR (100 MHz,
CDCl3): δ = 157.9, 129.9, 122.2, 114.8, 74.2, 67.1, and 66.4.
4‐((benzyloxy)methyl)‐1,3‐dioxolan‐2‐one (2m). 1H NMR
(400 MHz, CDCl3): δ = 7.38–7.26 (m, 5H), 4.60–4.54 (m, 1H),
4.57 (q, J = 12.0 Hz, 2H), 4.47 (t, J = 8.4 Hz, 1H), 4.37 (dd, J = 8.3
and 6.0 Hz, 1H), 3.73–3.59 (m, 2H). 13C NMR (100 MHz, CDCl3):
δ = 155.0, 137.2, 128.4, 127.9, 127.6, 75.1, 73.5, 68.9, and 66.2.
4‐((allyloxy)methyl)‐1,3‐dioxolan‐2‐one (2n). 1H NMR (400
MHz, CDCl3): δ = 5.90–5.83 (m, 1H), 5.30–5.21 (m, 2H),
4.82–4.81 (m, 1H), 4.52–4.48 (m, 1H), 4.06–4.04 (m, 1H),
3.70–3.67 (m, 2H), 3.63–3.59 (m, 2H). 13C NMR (100 MHz,
CDCl3): δ = 155.0, 133.8, 118.1, 75.1, 72.7, 69.0, and 66.4.
2.5. Characterization data for cyclic carbonates
4‐Ethyl‐1,3‐dioxolan‐2‐one (2a). 1H NMR (400 MHz, CDCl3):
δ = 4.68–4.63 (m, 1H), 4.52 (t, J = 6.4 Hz, 1H), 4.07 (t, J = 6.0 Hz,
1H), 1.84–1.71 (m, 2H), 1.02 (t, J = 5.6 Hz, 3H). 13C NMR (100
MHz, CDCl3): δ = 155.2, 78.1, 69.1, 27.0, and 8.5.
4‐(chloromethyl)‐1,3‐dioxolan‐2‐one (2b). 1H NMR (400
MHz, CDCl3): δ = 4.97–4.94 (m, 1H), 4.59 (t, J = 8.7 Hz, 1H), 4.42
(dd, J = 8.8 and 6.3 Hz, 1H), 3.80–3.71 (m, 2H). 13C NMR (100
MHz, CDCl3): δ = 154.2, 74.3, 67.1, and 43.7.
4‐(bromomethyl)‐1,3‐dioxolan‐2‐one (2c). 1H NMR (400
MHz, CDCl3): δ = 4.98–4.92 (m, 1H), 4.59 (t, J = 8.8 Hz, 1H), 4.35
(dd, J = 8.9 and 5.9 Hz, 1H), 3.58–3.57 (m, 2H). 13C NMR (100
MHz, CDCl3): δ = 154.2, 74.1, 68.2, and 31.5.
1
4‐((prop‐2‐yn‐1‐yloxy)methyl)‐1,3‐dioxolan‐2‐one (2o). H
1
4‐(hydroxymethyl)‐1,3‐dioxolan‐2‐one (2d). H NMR (400
NMR (400 MHz, CDCl3): δ = 4.86–4.83 (m, 1H), 4.50 (t, J = 8.4
Hz, 1H), 4.40–4.36 (m, 1H), 4.27–4.16 (m, 2H), 3.79–3.69 (m,
2H), 2.48 (t, J = 2.4 Hz, 1H). 13C NMR (100 MHz, CDCl3): δ =
155.0, 78.6, 75.7, 74.8, 68.5, 66.3, and 58.9.
4‐phenyl‐1,3‐dioxolan‐2‐one (2p). 1H NMR (400 MHz,
CDCl3): δ = 7.46–7.42 (m, 3H), 7.38–7.35 (m, 3H), 5.68 (t, J = 8.0
Hz, 1H), 4.80 (t, J = 8.4 Hz, 1H), 4.37–4.35 (m, 1H). 13C NMR
(100 MHz, CDCl3): δ = 154.9, 135.9, 129.9, 129.4, 126.0, 78.1,
and 71.3.
MHz, DMSO‐d6): δ = 5.25 (t, J = 4.4 Hz, 1H), 4.81–4.77 (m, 1H),
4.52–4.45 (m, 1H), 4.29–4.27 (m, 1H), 3.68–3.64 (m, 1H),
3.53–3.48 (m, 1H). 13C NMR (100 MHz, DMSO‐d6): δ = 155.2,
70.0, 65.9, and 60.6.
4‐methyl‐1,3‐dioxolan‐2‐one (2e). 1H NMR (400 MHz,
CDCl3): δ = 4.88–4.79 (m, 1H), 4.53 (t, J = 8.1 Hz, 1H), 4.00 (t, J =
8.3 Hz, 1H), 1.45 (d, J = 6.3 Hz, 3H). 13C NMR (100 MHz, CDCl3):
δ = 155.1, 73.6, 70.7, and 19.4.
4‐butyl‐1,3‐dioxolan‐2‐one (2f). 1H NMR (400 MHz, CDCl3):
δ = 4.73–4.66 (m, 1H), 4.52 (t, J = 8.1 Hz, 1H), 4.06 (t, J = 7.8 Hz,
1H), 1.81–1.67 (m, 2H), 1.40–1.37 (m, 4H), 0.91 (t, J = 6.9 Hz,
3H). 13C NMR (100 MHz, CDCl3): δ = 155.2, 69.5, 33.7, 26.5, 22.3,
and 13.9.
4‐(morpholinomethyl)‐1,3‐dioxolan‐2‐one (2q). 1H NMR
(400 MHz, CDCl3): δ = 4.82–4.75 (m, 1H), 4.48 (t, J = 8.3 Hz, 1H),
4.18 (t, J = 7.7 Hz, 1H), 3.61 (t, J = 4.3 Hz, 4H), 2.62 (d, J = 5.3 Hz,
2H), 2.48 (m, 4H). 13C NMR (100 MHz, CDCl3): δ = 154.7, 74.8,
67.6, 66.4, 69.8, and 54.0.

Anhua Liu et al. / Chinese Journal of Catalysis 39 (2018) 1320–1328
1323
4,4‐dimethyl‐1,3‐dioxolan‐2‐one (2r). 1H NMR (400 MHz,
CDCl3): δ = 4.13 (s, 2H), 1.50 (s, 6H). 13C NMR (100 MHz, CDCl3):
δ = 154.7, 81.8, 75.5, and 26.1.
Hexahydrobenzo[d][1,3]dioxol‐2‐one (2s). 1H NMR (400
MHz, CDCl3): δ = 4.69–4.64 (m, 2H), 1.87–1.85 (m, 4H),
1.63–1.54 (m, 2H), 1.43–1.35 (m, 2H). 13C NMR (100 MHz,
CDCl3): δ = 155.4, 75.8, 26.8, and 19.2.
850
(1)
(2)
1271
1498
3. Results and discussion
3.1. Characterization
3315
3367
1571
1520
The functional connectivity and structure of HB‐CTP were
investigated with FTIR spectroscopy by comparison of the
spectra of CC, 2,4,6‐trihydrazinyl‐1,3,5‐triazine, and the
resultant HB‐CTP (Fig. 1). The disappearance of the
characteristic stretching vibration of C–Cl of CC at 850 cm−1,
together with the immense enhancement of N–H absorption
around 3367 cm−1, would reveal the total substitution of all
three Cl atoms of CC, as well as the massive formation of
hydrazine linkages. In addition, the strong bands in the
1200–1600 cm−1 region correspond to the stretching modes of
triazine units, while their breathing mode could be assigned
near 805 cm−1.
In the solid state 13C CP/MAS NMR spectroscopy (Fig. 2(a)),
the only theoretical signal for aromatic triazine carbons of
HB‐CTP was observed at 168.1 ppm. Such a clean chart without
any impurity peaks indicates the integrity of the corresponding
triazine framework. Meanwhile, the XRD pattern was found to
be featureless (Fig. 2(b)), illustrating an amorphous structure.
The morphology of HB‐CTP was further investigated by SEM
and TEM as depicted in Fig. 2(c) and (d), which show that the
(3)
805
1354
1587
3500 3000 2500 2000 1500 1000 500
Wavenumber (cm1)
Fig. 1. FTIR spectra of CC (1), 2,4,6‐trihydrazinyl‐1,3,5‐triazine (2), and
HB‐CTP (3).
HB‐CTP material mainly exists in aggregate form. Finally, as
shown in Fig. 2(e), the thermal stability of such hydrazine‐rich
polymer was disclosed, and the initial degradation could be
observed at above 250 °C.
3.2. N2 and CO2 adsorption
The porosity of the HB‐CTP material was measured by ni‐
trogen‐adsorption analysis carried out at –196 °C. As shown in
Fig. 3, the adsorption‐desorption process displays a reversible
(b)
(a)
Spining sideband
*
*
*
250
200
150
ppm
100
50
0
5
10 15 20 25 30 35 40 45 50
2/(o)
100
90
80
70
60
50
40
30
20
10
0
(c)
(d)
(e)
100 200 300 400 500 600 700 800
Temperature (oC)
Fig. 2. 13C CP/MAS NMR spectrum (a), XRD pattern (b), SEM (c) and TEM (d) images, and TGA curve (e) of HB‐CTP.

1324
Anhua Liu et al. / Chinese Journal of Catalysis 39 (2018) 1320–1328
(a)
180
160
140
120
100
80
1.8
1.6
1.4
Adsorption
Desorption
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Adsorption
Desorption
60
40
20
0
0.0
0.2
0.4
0.6
0.8
1.0
0.0
0.2
0.4
0.6
0.8
1.0
Relative pressure (p/p0)
Relative pressure (p/p0)
Fig. 3. N2 adsorption‐desorption isotherm of HB‐CTP.
(b)
55
50
45
40
35
30
25
20
15
10
5
type‐II isotherm, representing
a
nearly non‐porous or
macroporous adsorbent that tends to proceed through unre‐
stricted monolayer‐multilayer adsorption [41]. Indeed, the BET
surface area was found to be 51.2 m2/g, and the total pore
volume was 0.28 cm3/g at P/P0 = 0.99. Such a low level of po‐
rosity should be attributed to the strong interaction between
triazine framework layers through massive hydrogen bonds
donated by the hydrazine linkages. Furthermore, the average
pore size calculated from the Barrett‐Joyner‐Halenda method
also lies largely in the macroporous region.
Despite poor surface area and porosity, the HB‐CTP material
has shown good CO2 capture capacity (1.86 mmol/g, 8.2 wt%)
at 0 °C and 0.1 MPa conditions (Fig. 4(a)). This abnormal
achievement could be reasonable if one considers the fact that
polymers based on triazine units and hydrazine linkages would
hold an extremely high N content (60.75%, determined by
elemental analysis) to intrinsically favor CO2 adsorption
through dipole‐quadrupole interactions between the
polarizable CO2 molecule and the vast number of basic N sites
[42–45]. Moreover, the HB‐CTP still exhibited satisfactory
capture performance after at least five consecutive adsorp‐
tion‐desorption cycles, rendering good recyclability (Fig. 4(b)).
0
0
1
2
3
4
5
Cycles
Fig. 4. CO2 adsorption‐desorption isotherm (a) and recyclability (b) of
HB‐CTP.
lowering either HB‐CTP loading or CO2 pressure would lead to
a notable decrease in reaction efficiency (entries 5 and 6).
Subsequently, various functionalized terminal and internal
epoxides were subjected to the optimized conditions in order
to test the generality of the present reaction. As shown in
Scheme 2, a number of cyclic carbonates were selectively
synthesized with broad substrate scope owing to the
remarkable catalytic activity of HB‐CTP. Epoxides bearing alkyl,
3.3. Catalytic performance
Table 1
The successful capture of CO2 with 8.2 wt% capacity by
HB‐CTP gave us an opportunity to test its catalytic performance
for conversion of CO2 into cyclic carbonates by cyclo‐addition
reaction. Primary catalytic studies were performed with
2‐ethyloxirane 1a and CO2 (2 MPa) at 60 °C for 4 h (Table 1).
Without the catalyst HB‐CTP, only 15% yield of the
corresponding cyclic carbonate 2a was observed by the
co‐catalyst TBAB (5 mol%) (entry 1). It was found that the
introduction of HB‐CTP would have an obviously positive effect
on reaction outcome, indicating the feasibility of our catalyst
design (entry 2). Raising reaction temperature from 60 to 80 °C
resulted in further enhancement of catalytic activity (entry 3).
Positively, a 97% yield of 2a could be obtained when the
reaction time was extended to 12 h (entry 4). Furthermore,
Cyclo‐addition of CO2 with 2‐ethyloxirane 1a catalyzed by HB‐CTP.
Entry HB‐CTP (mg) CO2 (MPa)
T (°C)
60
60
80
80
t (h)
4
4
Yielda (%)
1
2
3
4
5
6
—
50
50
50
25
50
2
2
2
2
2
1
15
34
56
97
75
69
4
12
12
12
80
80
Reaction conditions: 1a (10 mmol), TBAB (5 mol%).
a Determined by 1H NMR.

Anhua Liu et al. / Chinese Journal of Catalysis 39 (2018) 1320–1328
1325
O
O
1
HB-CTP (50 mg)
O
O
+
CO2
TBAB (5 mol%), 2 MPa, 80 oC, 12 h
R
R
2
O
O
O
O
O
O
O
Scheme 3. Cyclo‐addition of CO2 with epoxides catalyzed by HB‐CTP
alone. Reaction conditions: epoxides (10 mmol), HB‐CTP (50 mg), 2
MPa, 120 °C, 8 h.
O
O
O
O
O
O
O
O
O
O
O
O
O
OH
Cl
Me
Br
Et
Bu
2f, 99%
2a, 97%
2b, 99%
O
2c, 99%
2d, 94%
O
2e, 99%
2960 cm−1 was due to the residue of TBAB co‐catalyst), which
indicates its remarkable stability toward reaction conditions.
O
O
O
O
O
O
O
O
O
O
O
O
3.5. Plausible reaction mechanism
O
O
O
O
Hex
Me
iPr
Bu
Lauryl
2g, 99%
2h, 93%
O
2i, 95%
O
2j, 96%
O
2k, 81%
It has already been reported that hydroxyl groups attached
to the catalyst could play a key role for the high efficiency in
cyclo‐addition of CO2 with epoxides [46]. In addition,
hydroxyl‐functionalized porous polymers could also activate
the epoxides by forming hydrogen bonds along the solid/liquid
interface [33,36,37]. Therefore, on the basis of these results, a
plausible reaction mechanism was proposed in which the
catalytic cycle within this process tends to proceed via the
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
Ph
2p, 88%
Ph
Bn
2n, 92%
O
2o, 98%
2l, 91%
2m, 87%
O
O
O
O
O
O
O
O
Me
Me
2r, 71%
O
N
2s, 90%
(a)
2q, 67%
100
Scheme 2. Substrate scope of the cyclo‐addition. Reaction conditions:
epoxides (10 mmol), HB‐CTP (50 mg), TBAB (5 mol%), 2 MPa, 80 °C, 12
h.
80
60
40
20
0
allyl, phenyl, benzyl, propargyl, ether, hydroxyl, halide, and
morpholinyl groups reacted smoothly to give the
corresponding products in good to excellent yields under
metal‐ and solvent‐free conditions (2a−2q). Notably, the less
reactive substrate 1k with lauryl substituent as well as
gem‐substituted 2,2‐dimethyloxirane 1r both furnished the
target cyclic carbonates (2k and 2r) in acceptable yields.
Furthermore, the internal cyclohexene oxide 1s could also be
successfully converted with high efficiency. It is worth
mentioning that HB‐CTP alone could act as sufficient catalyst
for cyclo‐addition of CO2 with epichlorohydrin 1a,
epibromohydrin 1b, or glycidol 1c affording comparable yields,
although a higher reaction temperature should be provided
(Scheme 3).
1
2
3
4
5
Cycles
(b)
(1)
3.4. Catalyst recycling
(2)
One advantage of the HB‐CTP catalyst is its heterogeneous
nature, which can operate under solvent‐free conditions.
Hence, recycling experiments were conducted to test its
recyclability and stability. The results depicted in Fig. 5(a)
demonstrate that, by simple centrifugation and vacuum drying,
HB‐CTP could be reused for at least five runs without
significant loss of catalytic activity, rendering the present
reaction potentially viable for practical applications. In
addition, by the comparison of the FTIR spectra of HB‐CTP
before and after recycling (Fig. 5(b)), the structure of such
catalyst was shown to be largely intact (the rare difference at
3500 3000 2500 2000 1500 1000 500
Wavenumber (cm1)
Fig. 5. (a) Recyclability of HB‐CTP in cyclo‐addition of CO2 with 1a, (b)
FTIR spectra of HB‐CTP before (1) and after (2) recycle. Reaction con‐
ditions: 1a (10 mmol), HB‐CTP (50 mg), TBAB (5 mol%), 2 MPa, 80 °C,
12 h.

1326
Anhua Liu et al. / Chinese Journal of Catalysis 39 (2018) 1320–1328
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Graphical Abstract
Chin. J. Catal., 2018, 39: 1320–1328 doi: 10.1016/S1872‐2067(18)63040‐2
Novel hydrazine‐bridged covalent triazine polymer for CO2
capture and catalytic conversion
Anhua Liu *, Jinju Zhang, Xiaobing Lv
Dalian University of Technology
A novel hydrazine‐bridged covalent triazine polymer was synthesized
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新型肼桥联共价三嗪聚合物在二氧化碳捕集和催化转化方面的应用
刘安华*, 张金菊, 吕小兵
大连理工大学精细化工国家重点实验室, 辽宁大连 116024
摘要: 二氧化碳的捕集和催化转化是近年来二氧化碳利用方面的研究热点. 其原因, 一方面二氧化碳是储量丰富、廉价易
得的可再生碳资源, 另一方面它又是带来环境问题的温室气体. 以金属有机框架、沸石和多孔聚合物材料为代表的同时具
有规则孔道和活性催化位点的双功能材料为实践这一新概念创造了条件. 但是, 金属有机框架和沸石的应用面临由其自
身结构所带来的热稳定性和/或水稳定性较低等问题. 多孔聚合物材料则由于其高稳定性、低密度以及非金属等优点, 逐渐
成为该领域的研究重点. 然而, 当前关于利用多孔聚合物类材料作为有机催化剂以实现二氧化碳固定的报道, 其反应过程
一般需要较高温度、有机溶剂和/或过渡金属催化组分, 仍有较大改进余地. 本文设计合成了新型肼桥联共价三嗪聚合物
(HB-CTP), 意图在利用其富氮三嗪结构单元促进二氧化碳捕集的同时, 以大量肼官能团通过氢键作用活化环氧化物, 进而
将二氧化碳在无溶剂和非金属的温和条件下催化固定为环状碳酸酯.
HB-CTP 材料的合成方法简便易行, 由 2,4,6-三肼基-1,3,5-三嗪与三聚氯氰发生的亲核取代反应制得. 采用多种表征
手段分析了该类新材料的结构和形态: 红外光谱表明三聚氯氰的 C–Cl 键在聚合过程中反应完全, 其位于 850 cm‒1 处的吸
收信号彻底消失; 固体核磁谱图仅在 168.1 ppm 处显示三嗪环的单峰信号, 表明了该材料结构的完整性; X 射线粉末衍射
测试并未发现特征峰, 表明 HB-CTP 呈无定形态; 透射电镜和扫描电镜的观测结果则进一步证实了该材料的团聚形态; 最
后, 热重分析显示 HB-CTP 具有良好的热稳定性, 250 ºC 以上才开始分解. 然后, 通过氮气吸附测定了 HB-CTP 比表面积
(51.2 m2/g) 和总孔容 (0.28 cm3/g), 其吸附等温线呈 II 型, 表明材料结构以大孔为主, 通过层间吸附. 随后的二氧化碳吸附
测试发现, HB-CTP 在 0 °C、0.1 MPa 条件下显示出较高的二氧化碳捕集容量 (8.2 wt%), 并且经过连续吸附脱附循环五次,
仍能保持较好的二氧化碳捕集能力. 在 HB-CTP 材料良好的二氧化碳捕集容量基础上, 本文考察了其催化活性, 发现带有
多种取代基的环氧化物均能在无溶剂、非金属的温和条件下, 以较高的收率被转化为环状碳酸酯类产物; 并且底物结构中

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Anhua Liu et al. / Chinese Journal of Catalysis 39 (2018) 1320–1328
的卤素、羟基、炔基、烯丙基和苄基等官能团均未发生副反应, 显示出良好的底物适用范围. 此外, HB-CTP 材料可通过简
单的离心操作实现分离回收, 且经连续使用五次, 其催化活性也没有明显降低.
综上所述, 该类新型肼桥联共价三嗪聚合物不仅能够高效捕集二氧化碳, 而且还可以将其在温和条件下催化转化为环
状碳酸酯类产物, 具有一定理论研究意义和实际应用价值.
关键词: 共价三嗪聚合物; 捕集; 催化; 二氧化碳; 环状碳酸酯
收稿日期: 2018-01-05. 接受日期: 2018-02-02. 出版日期: 2018-08-05.
*通讯联系人. 电话/传真: (0411)84986257; 电子信箱: ahliu@dlut.edu.cn
基金来源: 国家自然科学基金 (21406025); 中国博士后科学基金 (2014M551067); 大连理工大学基本科研业务费专项项目
(DUT13RC(3)58).
本文的电子版全文由Elsevier出版社在ScienceDirect上出版(http://www.sciencedirect.com/science/journal/18722067).