Triazine-Based Porous Organic Polymer with Good CO2 Gas Adsorption Properties and an Efficient Organocatalyst for the One-Pot Multicomponent Condensation Reaction

Article abstract of DOI:10.1002/cctc.201600840

A new porous organic polymer PDVBTT-1 (poly-divinylbenzene-co-triallyloxytriazine) has been synthesized through radical co-polymerization utilizing two monomers, that is, divinylbenzene and 2,4,6-triallyloxy-1,3,5-triazine in the presence of AIBN (azobisi

Full text of DOI:10.1002/cctc.201600840

DOI: 10.1002/cctc.201600840
Full Papers
Triazine-Based Porous Organic Polymer with Good CO2
Gas Adsorption Properties and an Efficient Organocatalyst
for the One-Pot Multicomponent Condensation Reaction
Piyali Bhanja, Sauvik Chatterjee, and Asim Bhaumik*[a]
A new porous organic polymer PDVBTT-1 (poly-divinylben-
zene-co-triallyloxytriazine) has been synthesized through radi-
cal co-polymerization utilizing two monomers, that is, divinyl-
benzene and 2,4,6-triallyloxy-1,3,5-triazine in the presence of
AIBN (azobisisobutyronitrile) as a radical initiator under solvo-
thermal conditions in the absence of any structure directing
agent. The polymer has been characterized thoroughly by N2
sorption, FTIR, UV/Vis, and solid-state 13C cross-polarization
magic angle spinning (CP MAS) NMR spectroscopy, field emis-
sion FE-SEM, high-resolution HR-TEM, and thermogravimetric/
differential thermal analysis (TG/DTA). Owing to the considera-
bly good surface area of 644 m2 gꢀ1 and surface basic sites
(1.10 mmolgꢀ1), the material showed very good CO2 adsorp-
tion properties. Furthermore, the porous polymer showed
good catalytic activity in the base-catalyzed, one-pot, multi-
component condensation reaction between various substitut-
ed aromatic aldehydes, malononitrile, and activated phenols
such as 2-naphthol, resorcinol, etc., for the synthesis of 2-
amino-chromenes in water and under solvent-free microwave
irradiation conditions. This N-rich porous polymer is highly re-
cyclable and thus it has potential for a wide range of base-cat-
alyzed organic transformations in the future.
Introduction
Recently, considerable research interest has been focused on
executing one-pot catalytic transformations involving two or
more reactions without segregation of any intermediates.[1]
This idea of a multicomponent condensation strategy is very
cost effective compared with the traditional methods in the
context of labor, raw materials, time, and energy consumption.
This strategy is particularly more useful for heterogeneous cat-
alysts than for homogeneous ones.[2] The chromene moiety
containing 2H-chromene and 4H-chromene exists in several
natural oxygen-containing heterocyclic compounds, which are
largely present in edible fruits and vegetables.[3] In various cos-
metic formulations, bio-degradable agrochemicals, pigments,
photoactive materials, and natural products of industrial im-
portance, substituted 2-amino-4H-chromenes are present as
the molecular building blocks.[4] Owing to a wide spectrum of
usefulness in various pharmacological and biological processes,
such as mutagenicity,[5] antitumor,[6] anticancer,[7] laboratory
analysis of many antimicrobial agents,[8] etc., chromene deriva-
tives have been intensively studied. There are several reports
of the synthesis of 2-amino-4H-cromenes in the presence of
some homogeneous inorganic bases such as K2CO3,[9] NaOH,[10]
as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU),[12] 1,4-diazabicy-
clo[2.2.2]octane (DABCO),[13] piperidine,[14] and pyridine.[15]
Owing to the homogeneous nature of the bases, product sep-
aration from the reaction mixture is very difficult and challeng-
ing although large product yields are observed over these cat-
alysts. In this context, there are some reports of the synthesis
of chromene derivatives by using metal-mediated heterogene-
ous catalysts such as CeO2-ZrO2,[16] Fe3O4@SiO2,[17] TAFMC-1,[18]
and CeO2-CaO[19] composites, although they have some draw-
back owing to the possibility of unexpected leaching of the
metals during the course of the reaction. Thus, it is very desira-
ble to develop novel heterogeneous organocatalysts, which
are metal-free, nontoxic, robust, inert towards moisture and air,
and have high recyclability.[20]
In recent years, porous organic polymers (POPs) such as con-
jugated microporous polymers (CMPs), crystalline triazine-
based frameworks (CTFs), porous aromatic frameworks (PAFs),
and polymers of intrinsic microporosity (PIMs) have attracted
wide scale attraction owing to their versatile potential for sen-
sors,[21] optoelectronics,[22] gas adsorption,[23] and catalysis.[24]
These porous organic materials have good Brunauer–Emmett–
Teller (BET) surface areas, surface hydrophobicity, high thermal
and mechanical stability, good flexibility in the framework, as
they can be designed by using a diverse range of organic
building blocks. Wang et al. have reported benzimidazole-con-
taining POPs for base-catalyzed reactions owing to N-rich cen-
ters.[25] Compared with the covalent imine network (CIN), cova-
lent organic frameworks (COFs), and metal–organic frameworks
(MOFs), POPs have gained more attention owing to their easy
synthesis.[26] Generally, POP materials can be designed by using
single or multiple organic monomers to produce a two- or
[11]
acids like TiCl4 as well as a few hazardous organic bases such
[a] P. Bhanja, S. Chatterjee, Prof. Dr. A. Bhaumik
Department of Materials Science
Indian Association for the Cultivation of Science
2A & B, Raja S.C. Mullick Road, Jadavpur, Kolkata 700032 (India)
Fax: (+91)33-2473-2805
E-mail: msab@iacs.res.in
Supporting information and the ORCID identification number(s) for the
author(s) of this article can be found under http://dx.doi.org/10.1002/
cctc.201600840.
ChemCatChem 2016, 8, 1 – 11
1
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
three-dimensional polymeric network through chain growth
and step growth co-polymerization reactions involving radical
polymerization, solvothermal synthesis, and condensation poly-
merization routes.[27] It is pertinent to note that various N-rich
microporous materials with considerable surface area have
shown excellent CO2 uptake capacities, for example, zeolitic
imidazole frameworks (ZIFs),[28] covalent organic frameworks
(COFs),[29] porous carbons,[30] etc. As CO2 is one of the major
greenhouse gases responsible for global warming, materials
having high CO2 capture properties have gained immense at-
tention in this context to keep the ecological balance of the
earth.[31] Further, such porous organic polymers containing N-
rich functionalities, that is, amine, amide, triazine, carbazole, or
porphyrin units with high surface basic sites can be employed
as heterogeneous base catalysts for various organic transfor-
mations.[32]
Figure 1. N2 adsorption/desorption isotherm of PDVBTT-1. Adsorption and
desorption isotherms are indicated by filled and empty circles, respectively.
The pore size distribution pattern has been plotted by employing the
NLDFT method, shown in the inset.
Herein, we have designed a new triazine-doped porous or-
ganic polymer through the radical polymerization of divinyl-
benzene (DVB) and 2,4,6-triallyloxy-1,3,5-triazine (TT) in the
presence of azobisisobutyronitrile (AIBN) as a radical initiator
under solvothermal conditions (Scheme 1). This robust, non-
air- and moisture-sensitive heterogeneous metal-free triazine-
based organocatalyst, PDVBTT-1, showed high CO2 uptake
property as well as excellent catalytic activity in the multicom-
ponent condensation reaction for the production of 2-amino-
chromene derivatives with a very good recycling efficiency.
this is shown in the inset of Figure 1. Here, two peaks corre-
sponding to peak maximums at 1.5 and 2.6 nm are observed.
Micropores 1.5 nm in dimension could be attributed to the
void space generated during the formation of the polymer net-
work and other ones 2.6 nm in dimension could be generated
as a result of the interparticle mesoporosity. In addition to the
NLDFT method, the t-plot method has also been applied to
differentiate between the micropores and external surface
area. According to the De Boer statistical thickness (t-plot), the
total BET surface area of PDVBTT-1 has contributions of 360
and 284 m2 gꢀ1 from the micropores and mesopores, respec-
tively. Here, the relative pressure regions for the determination
of the specific surface area and pore volume were P/P0 =0–0.3
and 0.9994 P/P0, respectively. The BET surface area for two
other materials, PDVBTT-2 and PDVBTT-3, synthesized with
other molar ratios of divinylbenzene and 2,4,6-triallyloxy-1,3,5-
triazine, are estimated as 160 and 428 m2 gꢀ1, respectively, and
these are shown in the Supporting Information (Figure S1). In
addition, the self-polymerized material PTT-1, synthesized in
the absence of DVB, showed a BET surface area of only
18 m2 gꢀ1.
Results and Discussion
Surface area and pore volume measurements
The Brunauer–Emmett–Teller (BET) surface area and porosity of
the PDVBTT-1 polymer were measured from nitrogen sorption
analysis at 77 K, where N2 acted as an adsorbate gas molecule.
The N2 adsorption/desorption isotherm of PDVBTT-1 polymer is
shown in Figure 1, which would be classified as a mixture of
type I and type IV without any hysteresis loop. In the low pres-
sure region (0.03–0.18 P/P0), the initial uptake of N2 clearly con-
firms the presence of micropores in the polymer matrix and
a very significant amount of N2 uptake in the high pressure
region (0.74–0.99 P/P0) is observed owing to interparticle po-
rosity. The BET surface area of this material is found to be
644 m2 gꢀ1 and the pore volume of 0.359 ccgꢀ1 is found from
the sorption isotherm. The NLDFT (non-local density functional
theory) model has been employed for the estimation of the
pore size distribution in the entire relative pressure range and
Framework and bonding
The presence of organic functionalities and chemical bonding
in the framework of PDVBTT-1 is confirmed from Fourier trans-
Scheme 1. Schematic outlining the synthesis of triazine-functionalized PDVBTT-1 polymer.
&
ChemCatChem 2016, 8, 1 – 11
www.chemcatchem.org
2
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Papers
form infrared spectroscopy (FTIR) and UV/Vis spectroscopic
analysis. The FTIR spectrum of PDVBTT-1 in the 4000 cmꢀ1 to
400 cmꢀ1 region is shown in Figure 2. It is seen from Figure 2c
Figure 3. Solid-state 13C CP MAS NMR spectrum of PDVBTT-1 material.
present in the model framework structure of PDVBTT-1 in the
upper portion of Figure 3. The aliphatic carbon peaks are ob-
served at different chemical environments of 80.5, 42.5, 28.6,
and 14.2 ppm, where the first peak indicates the deshielded
carbon atom close to the oxygen atom of the polymeric frame-
Figure 2. FTIR spectra of (a) DVB, (b) TT, and (c) PDVBTT-1 samples.
that a strong peak appears at 2926 cmꢀ1 for the methylene Cꢀ work.[35] The less intense signal at 110.8 ppm represents a trace
H stretching vibration. The additional pair of bands at 1602
and 1511 cmꢀ1 is attributed to the aromatic C=C stretching vi-
bration of divinylbenzene bearing a benzene ring as part of
the PDVBTT-1 polymer, which are also observed in both Fig-
ure 2a and b, corresponding to that of DVB and TT, respective-
ly. The observed peak at 1565 cmꢀ1 could be assigned to the
presence of C=N stretching vibrations of the triazine ring. Fur-
ther, it is also associated with peaks at 1407, 1334, and
1057 cmꢀ1 suggesting that the material contains a triallyl cya-
nurate moiety, peaks that are also present in Figure 2b.[33] The
peak at 1447 cmꢀ1 could be assigned to the aliphatic CꢀH
bending vibration. The other peaks at 789 and 708 cmꢀ1 are
due to out-of-plane bending vibrations of the aromatic CꢀH
bond. The UV/Vis spectrum of the PDVBTT-1 sample is shown
in Figure S2 (in the Supporting Information) where a strong
absorption band appears at 265 nm for the p!p* transition of
the heteroatom lone pair in the substituted aromatic ring. Dif-
ferent types of functional groups present in the polymer
matrix of PDVBTT-1 could be responsible for the multiple
bands in the UV/Vis spectrum.
amount of unreacted olefin in the material.[36] Thus, the solid-
state 13C CP MAS NMR analysis results demonstrate the forma-
tion of the desired porous polymer framework.
Microscopic analysis
The field emission FE-SEM images of PDVBTT-1 material at two
different magnifications are shown in Figure 4a and b. As seen
Figure 4. FE-SEM images for the PDVBTT-1 sample at two different magnifi-
cations: a) scale bar=1 mm; b scale bar=100 nm.
Solid-state 13C cross-polarization magic angle spinning (CP
MAS) NMR analysis
from the figure, the material exhibits a globular-like morpholo-
gy with a diameter of 130–160 nm, generated from the aggre-
gation of 25–30 nm small sphere-like particles. On the other
hand, the high-resolution transmission electron microscopic
images of this material are depicted in Figure 5a–d, where the
micropores (white spots) with diameters of approximately
1.4 nm are clearly seen and this is observed in different parts
of the specimen.
To get an idea about carbon atoms in different chemical envi-
ronments in the PDVBTT-1 polymeric moiety, solid-state 13C CP
MAS NMR analysis has been carried out in the range ꢀ20 to
200 ppm. Figure 3 shows the solid-state 13C CP MAS NMR spec-
trum of this porous organic polymer in which the triazine ring
containing carbon appears at a chemical shift of 170.6 ppm.[34]
Three intense peaks at 149.0, 138.2, and 126.1 ppm could be
assigned to the benzene ring containing carbons, which is
ChemCatChem 2016, 8, 1 – 11
www.chemcatchem.org
3
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
Figure 6. TGA (a) and DTA (b) plots of the PDVBTT-1 material.
Carbon dioxide uptake study
To explore the surface basic sites and high surface area, we
have performed the adsorption of Lewis acidic gas CO2 over
PDVBTT-1. Figure 7A demonstrates the CO2 adsorption/desorp-
tion isotherm of PDVBTT-1 polymer at two different tempera-
tures, 273 and 298 K (room temperature) up to 3 bar pressure.
As seen from the figure, the isotherm discloses a steady rise in
the CO2 uptake with the increase in the pressure of CO2. From
the adsorption isotherm pattern, it is clearly noticeable that
CO2 adsorption amount is somewhat low near the high pres-
sure region but the uptake amount does not reach a saturation
value, which suggests that the material can further adsorb CO2
at higher pressures. The total CO2 uptake capacities are 12.16
(53.5 wt%) and 2.84 mmolgꢀ1 (12.49 wt%) at 273 and 298 K
up to 3 bar pressure. Zhang et al. reported a series of novel
azo-functionalized co-polymerized networks with a CO2 uptake
ability up to 3.22 mmolgꢀ1 at 273 K/1.0 bar.[37] Chen et al. men-
tioned the remarkable CO2 uptake ability (18.8 wt% at 1 bar
and 273 K) of NOP-50A among a series of porous organic poly-
mers.[38] Ethiraj et al. reported the cerium-based metal–organic
framework with MOF-76 topology revealed excellent carbon di-
oxide adsorption properties (15 wt% at 1.1 bar).[39] Also, the
adsorbed gas can be easily recovered by decreasing in the ap-
plied pressure, as indicated from the reversible nature of the
desorption isotherm. With the help of the Clausius–Clapeyron
equation, the isosteric heat of adsorption (Qst) for PDVBTT-
Figure 5. HR-TEM images for the PDVBTT-1 material at different scales and
positions.
Thermal and elemental analysis
To understand the thermal stability of PDVBTT-1 polymer, ther-
mogravimetric/differential thermal analysis (TG/DTA)s was car-
ried out in the temperature region 25 to 8008C under air flow
conditions at 108C temperature ramp per minute. Figure 6 dis-
plays the TG/DTA plots of the PDVBTT-1 sample, where the
polymer starts decomposing at 3408C and the second weight
loss above 4758C is due to decomposition of the residual part
of stable oxygen-containing groups in the polymer framework,
which is compatible with the DTA profile.
Thus, it can be concluded that the PDVBTT-1 polymer shows
considerably high thermal stability. In addition to that, CHN
analysis of the material revealed the carbon, hydrogen, and ni-
trogen contents in the PDVBTT-1 polymer moiety, where C=
79.24%, H=7.48%, and N=6.76%. The elemental analysis
result agrees well with the theoretically calculated values (C=
81.00%, H=7.14%, N=5.45%, and O=6.23%) as obtained
from the stoichiometry of the framework of PDVBTT-
1.
Surface basic site measurements
To measure the total surface basic sites of the
PDVBTT-1 material, acid–base titration has been con-
ducted by using (M/100) standardized NaOH and (M/
100) oxalic acid solution in the presence of phe-
nolphthalein as an indicator. The total surface basic
sites of PDVBTT-1 was thus calculated as
1.10 mmolgꢀ1, which is good for its CO2 gas adsorp-
tion properties as well as for exploring its catalytic
Figure 7. (a) CO2 adsorption/desorption isotherm of PDVBTT-1 at two different tempera-
tures, 273 K and 298 K, and (b) isosteric heat of adsorption (Qst) plot of PDVBTT-1 material
as a function of CO2 gas molecules adsorbed.
potential in the multicomponent condensation reac-
tion.
&
ChemCatChem 2016, 8, 1 – 11
www.chemcatchem.org
4
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Papers
1 has been calculated from the adsorption isotherms at two
different temperatures and this is plotted in Figure 7B. More-
over, the initial Qst value was found to be 58.5 kJmolꢀ1 (error
bar ꢁ2.0%) indicating strong molecular interactions between
the material surface containing basic sites and adsorbate gas
molecules, although the value is much lower than that of the
chemical bond energy, generating the reversible physisorption
process.[34]
For standardization of the exact catalyst amount, first we
carried out the same experiment by combining benzaldehyde,
malononitrile, and resorcinol at 1008C for 15 min under micro-
wave conditions in the absence of any catalysis. However, no
condensation product is observed with these conditions. Then,
we added 10, 20, 30, and 40 mg of PDVBTT-1 catalyst for the
same reaction. With the increase in catalyst amount in the re-
action mixture from 10 to 30 mg, the product yield increased
steadily. However, the product yield became saturated with
over 30 mg of catalyst. Thus, 30 mg of organocatalyst was
chosen as the best amount for this multicomponent condensa-
tion reaction.
Catalysis
To compare this catalyst with other various homogeneous
and heterogeneous basic catalysts, the same model reaction
was carried out under the optimized reaction conditions. After
the experiment, it was observed that a significantly lower
amount of product is obtained in the presence of homogene-
ous base catalysts whereas over the PDVBTT-1 catalyst product
yields are much larger. These results are listed in Table 2. Pure
polymer PTT-1 as well as PDVBTT-2 and PDVBTT-3 were used
as catalysts for this three-component coupling reaction and in
all cases the observed 2-amino-4H-chromene yields are much
lower than PDVBTT-1 (Table 2).
The high surface area of PDVBTT-1 containing the basic sites
has motivated us to inspect the base-catalyzed organic trans-
formations employing this material as a heterogeneous orga-
nocatalyst.[40] Thus, we have performed a one-pot, three-com-
ponent condensation reaction by using various substituted ar-
omatic aldehyde, malononitrile, and activated phenols for the
production of 2-amino-chromenes in solvent-free and aqueous
media under microwave irradiation. Under typical microwave
heating conditions, we have carried out this base-catalyzed re-
action in MW G10-type glass vials containing organic sub-
strates such as benzaldehyde (1 mmol), malononitrile (1 mmol),
and resorcinol (1.1 mmol) in the presence of 30 mg of catalyst
under solvent-free conditions and with the addition of 2 mL of
water. The obtained product yields and turnover numbers
(TONs) from various electron donating/withdrawing group sub-
stituted aromatic aldehydes are listed in Table 1. The schematic
representation for the synthesis of 2-amino-4H-chromenes
over PDVBTT-1 catalyst has been drawn in Scheme 2. Here,
some important parameters such as reaction temperature,
time, and catalyst amount play crucial roles for this one-pot,
three-component reaction.
In addition, some other reported heterogeneous organoca-
talysts have been compared with our newly designed porous
organic polymer for the production of 2-amino-4H-chromenes
under benign conditions. Kumbhar et al. have reported[41] mi-
crowave-assisted 2-amino-4H-chromene synthesis with 86%
product yield by using multi-cationic ionic liquids. Li et al.
mentioned[42] a domino reaction for the synthesis of 2-amino-
4H-chromene derivatives by using bovine serum albumin
(BSA) as a catalyst with yields of 31–96% under the optimized
conditions. Mondal et al. have designed[43] triazine-functional-
ized ordered mesoporous organosilica as a novel organocata-
lyst (TFMO-1) for facile one-pot synthesis of 2-amino-4H-chro-
menes under solvent-free conditions with excellent yields.
Compared with these catalytic systems, the synthesis of the
PDVBTT-1 catalyst is very simple and the reaction conditions
are user friendly and energy efficient.
To investigate the optimum reaction temperature, we have
conducted some control reactions at different temperatures by
using three components, benzaldehyde, malononitrile, and re-
sorcinol, as a representative reaction without changing any of
the stoichiometric ratios. As seen from Table 2, the product
yield increased with increasing the temperature step by step,
but above 1008C no improvement in product yield is noticed.
Also, the time duration plays an important part in the same
multicomponent condensation reaction. The best product
yield is obtained for 15 min time duration whereas lower yields
resulted from this reaction when it was conducted for
a 20 min time period.
The probable reaction mechanism for the synthesis of 2-
amino-4H-chromene derivatives can be described with three
different steps, that is, (i) Knoevenagel reaction, (ii) Michael ad-
dition, and (iii) intra-molecular cyclization reactions, which are
shown in Scheme 3. At first, the aromatic aldehyde undergoes
a Knoevenagel condensation reaction with malononitrile to
Scheme 2. Schematic representation of the synthesis of 2-amino-4H-chromenes over PDVBTT-1 catalyst.
ChemCatChem 2016, 8, 1 – 11
www.chemcatchem.org
5
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
Table 1. Synthesis of substituted 2-amino-4H-chromene derivatives over PDVBTT-1 as a heterogeneous base catalyst in aqueous or solvent-free reaction
conditions.
Entry
Reactant
Product
Reaction medium
t
[h]
Yield[a]
[%]
TON[b]
1
solvent free
15
86
26.06
2
solvent free
15
84
25.45
3
solvent free
10
15
15
86
85
82
26.06
4
solvent free
25.75
5
solvent free
24.84
6
solvent free
15
83
25.15
7
water
15
85
25.75
&
ChemCatChem 2016, 8, 1 – 11
www.chemcatchem.org
6
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Papers
Table 1. (Continued)
Entry Reactant
Product
Reaction medium
t
[h]
Yield[a]
[%]
TON[b]
8
water
10
15
15
86
84
86
26.06
9
water
25.45
10
water
26.06
11
water
15
85
25.75
12
water
15
86
26.06
[a] For entries 1–6 and 7–12, the isolated product yields are obtained when resorcinol and b-naphthol were used as reactants with other two components,
that is, malononitrile and different substituted aromatic aldehydes in the presence of 30 mg of catalyst (PDVBTT-1) at 1008C under microwave irradiation.
[b] The turnover number (TON) indicates moles of substrate molecules converted per mole of active sites, estimated by using the total surface basic sites
obtained from acid–base titration. The error in the product yield is within ꢁ1%.
form a-cyanocinnamonitrile as an intermediate, which can
react with resorcinol through a Michael addition reaction. The
PDVBTT-1 catalyst containing oxygen increases the electrophi-
licity of a-cyanocinnamonitrile bearing a ꢀCN group and sur-
face basic group (ꢀN) can help to abstract the proton. Finally,
the Michael addition intermediate can undergoes an intra-mo-
lecular cyclization reaction followed by tautomerization to
yield the 2-amino-4H-chromene derivative.
In Figure 8, we have plotted the reusability data of the
PDVBTT-1 catalyst for the reaction between benzaldehyde, ma-
lononitrile, and resorcinol. It can be seen from this plot that
the PDVBTT-1 heterogeneous organocatalyst is highly recycla-
ble and it retained its catalytic activity without significant loss
after five successive reaction cycles. Only a very small decrease
in the product yield was observed after each reaction cycle,
suggesting a sustainable future for PDVBTT-1.
ChemCatChem 2016, 8, 1 – 11
www.chemcatchem.org
7
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
Table 2. Dependence of the reaction temperature, time, and various
types of catalysts for the synthesis of 2-amino-4H-chromenes.
Entry
Catalysts
T
[8C]
t
Yield[a]
[%]
[min]
1
2
3
4
5
6
7
8
9[b]
10[c]
11[d]
no catalyst
K2CO3
pyridine
piperidine
PTT-1
PDVBTT-2
PDVBTT-3
PDVBTT-1
PDVBTT-1
PDVBTT-1
PDVBTT-1
100
100
100
100
100
100
100
100
100
90
25
15
15
15
18
15
15
15
10
15
15
0
39
44
37
3.5
67
56
86
68
72
57
Figure 8. Recycling efficiency of PDVBTT-1 in the one-pot, three-component
coupling reaction.
assisted heating conditions for the production of 2-amino-
chromenes. The material exhibits 53.5 wt% and 12.49 wt% CO2
uptake capability at 273 and 298 K and 3 bar pressure. In addi-
tion, it showed excellent catalytic activity with high recycling
efficiency in the multicomponent condensation reaction. The
easy synthetic strategy described herein for the triazine-func-
tionalized porous organic polymer, its CO2 capture property,
and its potential as an organocatalyst is expected to contribute
significantly to its environmental and eco-friendly applications
in the near future.
80
[a] Product yields [%] were obtained (entries 1–7) at 1008C for 15 min in
the presence of various catalysts (30 mg) under microwave-assisted heat-
ing conditions where the reactants are benzaldehyde (1 mmol, 106 mg),
malononitrile (1 mmol, 66 mg), and resorcinol (1.1 mmol, 121 mg). Isolat-
ed yields [%] were obtained at different temperatures: [b] 1008C for
10 min; [c] 908C; and [d] 808C without changing the other reaction pa-
rameters.
Conclusions
In summary, we have designed a new triazine-functionalized
porous organic polymer through radical a co-polymerization
route involving divinylbenzene and 2,4,6-triallyloxy-1,3,5-tria-
zine in the presence of AIBN as a radical initiator under solvo-
thermal conditions. This porous polymer bears considerable
basic sites and high surface area with microporosity and these
are the main driving forces for its high CO2 uptake property as
well as excellent catalytic activity in the one-pot multicompo-
nent base-catalyzed condensation reaction under microwave-
Experimental Section
Materials
2,4,6-Triallyloxy-1,3,5-triazine (Mw =249.27 gmolꢀ1) and divinylben-
zene (Mw =130.19 gmolꢀ1) were purchased from Sigma–Aldrich,
India. Azobisisobutyronitrile (AIBN; Mw =164.21 gmolꢀ1) was ob-
tained from SRL, India, and it was used after recrystallization from
hot ethanol. Solvents were used without further purification. All
Scheme 3. Possible mechanism for synthesis of 2-amino-4H-chromenes over PDVBTT-1 catalyst by using benzaldehyde, malononitrile, and resorcinol.
&
ChemCatChem 2016, 8, 1 – 11
www.chemcatchem.org
8
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Papers
other organic substrates used in experiments were of analytical
grade produced by Merck.
Q-600 under air flow. A PerkinElmer 2400 Series II CHN analyzer
was used for elemental analysis of the porous polymer.
Synthesis of the porous polymer organocatalyst
Leaching and hot filtration tests
In a typical procedure, the porous organic polymer PDVBTT-1 was
synthesized through radical polymerization of divinylbenzene and
2,4,6-triallyloxy-1,3,5-triazine under solvothermal conditions by
using AIBN as a radical initiator without the aid of any template
molecule. First, divinylbenzene (1.562 g, 0.012 mol) and 2,4,6-trially-
loxy-1,3,5-triazine (0.747 g, 0.003 mol) were added to a 100 mL
round-bottom flask containing acetone (25 mL) and the mixture
was allowed to stir for 20 min. Before addition of recrystallized
AIBN (50 mg, 0.15 mmol) into the former solution mixture for initia-
tion of the polymerization reaction, the flask was purged with ni-
trogen gas to generate an inert atmosphere. Then, the mixture
was stirred for 2 h under a nitrogen atmosphere at room tempera-
ture (258C) to get a colorless slurry, which was kept in a Teflon-
lined stainless steel autoclave at 1208C for 24 h under static condi-
tions. The final product was washed thoroughly with acetone and
dried in aerobic conditions. The schematic illustration of synthesis
of the PDVBTT-1 polymeric framework is shown in Scheme 1. How-
ever, we have synthesized two other materials by varying both mo-
nomer ratios (7:3 and 9:1) of DVB and TT to give PDVBTT-2 and
PDVBTT-3, respectively, to optimize the specific BET surface area
without changing any reaction parameters and conditions. The N2
adsorption/desorption isotherms for the PDVBTT-2 and PDVBTT-3
materials showed lower surface areas than that of PDVBTT-1. We
have also synthesized self-polymerized material by using the poly-
merization of 2,4,6-triallyloxy-1,3,5-triazine under identical reaction
conditions and the resulting material has been designated as PTT-
1. Thus, the high BET surface area and microporosity of N-contain-
ing PDVBTT-1 polymer convinced us to explore the CO2 gas ad-
sorption property as well as the base-catalyzed one-pot multicom-
ponent condensation reaction. Thus, the PDVBTT-1 polymer has
been characterized thoroughly.
To check the heterogeneity of the organocatalyst, we carried out
a leaching test by using the same model reaction where the solid
catalyst was filtered after completion of the reaction and the one-
pot multicomponent coupling reaction was performed by utilizing
the filtrate. No product (2-amino-chromene) formation was noticed
in this case, which confirms no leaching behavior of the material,
suggesting a heterogeneous catalyst. For further clarification about
the leaching nature of the catalyst, hot filtration experiments were
performed. The reaction was stopped midway through the total
time and the reaction mixture was allowed to stir in dry methanol
(2 mL) for 1 h at room temperature. The solid catalyst was recov-
ered by simple filtration and after evaporation of methanol, the re-
1
maining product was subjected to H NMR spectroscopy, where no
peak was observed for the triazine moiety from the organocatalyst,
which clearly confirms the perfectly heterogeneous nature of the
PDVBTT-1 material.
Catalytic reaction and recyclability test
To examine the recyclability of the material as a basic catalyst in
the one-pot multicomponent reaction, we have studied the same
reaction by using benzaldehyde (1 mmol; 106 mg), malononitrile
(1 mmol, 66 mg), and resorcinol (1.1 mmol, 121 mg) for five succes-
sive runs under microwave conditions at 1008C for 15 min. After
completion of each reaction cycle, the catalyst was washed thor-
oughly with ethyl acetate and dried in air overnight. In a typical
MW method, before loading the reactant in the sealed tube, one
magnetic needle was inserted to ensure a homogeneous mixture
and after completion of the reaction, the mixture was cooled to
room temperature. The progress of the reaction was analyzed by
using thin layer chromatography (TLC) and the product was ex-
tracted with ethyl acetate after separation of the catalyst by simple
filtration techniques. To obtain the pure product, it was washed
with petroleum ether repeatedly to get rid of organic impurities
and then re-crystallized from hot methanol. The FTIR spectrum of
the reused catalyst is shown in Figure S3 (in the Supporting Infor-
mation), suggesting the polymer framework has been retained
compared with that of the freshly prepared catalyst PDVBTT-1 after
five reaction cycles. The reused catalyst PDVBTT-1 was further char-
acterized through N2 sorption, FE-SEM, HR-TEM, and TG/DTA analy-
sis to check the stability as well as sustainability of the framework.
The N2 adsorption/desorption isotherm of reused PDBVTT-1 catalyst
was similar to that of the freshly prepared catalyst, as is shown in
Figure S4 (in the Supporting Information). The SEM images of the
reused catalyst are given in Figure S5 (in the Supporting Informa-
tion), which revealed a similar globular-type morphology, suggest-
ing the material retained its framework stability after the fifth con-
secutive reaction cycle. Further, from the HR-TEM images of the
reused catalyst (Figure S6 in the Supporting Information) similar
sizes of pores with diameters of approximately 1.4 nm are found.
Further, to check the thermal stability of the reused PDVBTT-1 cata-
lyst after the fifth reaction cycle, TG/DTA experiments were carried
out from room temperature to 8008C and the profile diagram is
shown in Figure S7 (in the Supporting Information), which is similar
to the freshly prepared catalyst in its pattern. These results suggest
that PDVBTT-1 possesses good thermal and mechanical stability to
carry out repetitive recycling experiments. The pure crystalline
Characterization techniques
The Quantachrome Autosorb 1-C was used to record the nitrogen
adsorption/desorption isotherms of the porous organic polymers
at 77 K and the samples were activated for 12 h at 1208C under
high vacuum conditions to get rid of any adsorbed moisture or
solvent. The NLDFT pore-size distribution of PDVBTT-1 was estimat-
ed by employing N2 at 77 K and the carbon slit pore model of Au-
tosorb-1 software from the N2 adsorption/desorption isotherm. Uti-
lizing Bel Japan Inc. Belsorp-HP, the CO2 adsorption/desorption iso-
therms of the material were recorded at two different tempera-
tures, 298 and 273 K. The 13C CP MAS NMR spectrum of the poly-
mer was obtained with
a Bruker Advance 500 MHz NMR
spectrometer using a 4 nm MAS probe with a spinning rate
5000 Hz, with sideband suppression. To record the FTIR spectrum
of the samples, a PerkinElmer Spectrum 100 was used. UV/Vis dif-
fuse reflectance spectrum of the sample was recorded with a UV
2401PC with an integrating sphere attachment where BaSO4 was
used as the background standard. HR-TEM images of the hierarchi-
cally porous material were recorded by using a JEOL 2010 TEM, op-
erated at 200 kV where the sample was prepared by dropping a so-
nicated ethanolic suspension of the sample over a carbon-coated
copper grid. To investigate the morphology and particle size of the
sample, FE-SEM images were obtained by using a Jeol JEM 6700.
TG/DTA analysis of PDVBTT-1 was carried out with a temperature
ramp of 108Cminꢀ1 in a TGA instrument thermal analyzer TA-SDT
ChemCatChem 2016, 8, 1 – 11
www.chemcatchem.org
9
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
1
products were characterized by using H and 13C NMR spectrosco-
[22] a) C. Gu, N. Huang, Y. Chen, H. Zhang, S. Zhang, F. Li, Y. Ma, D. Jiang,
Angew. Chem. Int. Ed. 2016, 55, 3049–3053; Angew. Chem. 2016, 128,
3101–3105; b) Y. Xu, S. Jin, H. Xu, A. Nagai, D. Jiang, Chem. Soc. Rev.
2013, 42, 8012–8031.
py (data are given in section S8 in the Supporting Information).
[23] a) R. Dawson, A. I. Cooper, D. J. Adams, Poly. Int. 2013, 62, 345–352;
b) A. Modak, A. Bhaumik, J. Solid State Chem. 2015, 232, 157–162; c) Z.
Chang, D. S. Zhang, Q. Chen, X. H. Bu, Phys. Chem. Chem. Phys. 2013,
15, 5430–5442.
[24] a) Y. Zhang, S. N. Riduan, Chem. Soc. Rev. 2012, 41, 2083–2094; b) M. G.
Goesten, A. Szecsenyi, M. F. de Lange, A. V. Bavykina, K. B. S. S. Gupta, F.
Kapteijn, J. Gascon, ChemCatChem 2016, 8, 961–967; c) R. Li, Z. J. Wang,
L. Wang, B. C. Ma, S. Ghasimi, H. Lu, K. Landfester, K. A. I. Zhang, ACS
Catal. 2016, 6, 1113–1121; d) A. Modak, J. Mondal, A. Bhaumik, Appl.
Catal. A 2013, 459, 41–51; e) S. Mondal, J. Mondal, A. Bhaumik, Chem-
CatChem 2015, 7, 3570–3578.
Acknowledgments
P.B. and S.C. wish to thank CSIR and DST, New Delhi, for senior
and junior research fellowships, respectively. A.B. wishes to thank
DST, New Delhi, for use of instrumental facilities through the DST
Unit on Nanoscience and DST-UKIERI project grants.
Keywords: CO2 adsorption · heterogeneous catalysis · high
surface area · multicomponent condensation · porous organic
polymer
[25] Y. X. Wang, L. J. Wang, C. P. Liu, R. H. Wang, ChemCatChem 2015, 7,
1559–1565.
[26] a) N. L. Torad, M. Hu, Y. Kamachi, K. Takai, M. Imura, M. Naito, Y. Yamau-
chi, Chem. Commun. 2013, 49, 2521–2523; b) R. R. Salunkhe, Y. Kamachi,
N. L. Torad, S. M. Hwang, Z. Sun, S. X. Dou, J. H. Kim, Y. Yamauchi, J.
Mater. Chem. A 2014, 2, 19848–19854; c) H. Zhang, M. Zhang, P. Lin, V.
Malgras, J. Tang, S. M. Alshehri, Y. Yamauchi, S. Du, J. Zhang, Chem. Eur.
J. 2016, 22, 1141–1145.
[27] a) Q. Sun, Z. Dai, X. Meng, F. S. Xiao, Chem. Soc. Rev. 2015, 44, 6018–
6034; b) S. Hug, L. Stegbauer, H. Oh, M. Hirscher, B. V. Lotsch, Chem.
Mater. 2015, 27, 8001–8010; c) G. Chang, Z. Shang, T. Yu, L. Yang, J.
Mater. Chem. A 2016, 4, 2517–2523.
[1] a) A. Khodairy, S. K. Mohamed, A. M. Ali, M. T. El-Wassimy, N. S. Ahmed, J.
Chem. Pharm. Res. 2015, 7, 332–340; b) A. M. Akondi, M. L. Kantam, R.
Trivedi, J. Bharatam, S. P. B. Vemulapalli, S. K. Bhargava, S. K. Buddana,
R. S. Prakasham, J. Mol. Catal. A 2016, 411, 325–336; c) P. Chidurala, V.
Jetti, R. Pagadala, J. S. Meshram, S. B. Jonnalagadda, J. Heterocycl. Chem.
2015, 52, 1302–1307.
[2] a) C. M. R. Volla, L. Atodiresei, M. Rueping, Chem. Rev. 2014, 114, 2390–
2431; b) A. Rahmati, A. Moazzam, Z. Khalesi, Tetrahedron Lett. 2014, 55,
3840–3843.
[28] a) W. R. Woerner, A. M. Plonka, X. Chen, D. Banerjee, P. K. Thallapally, J. B.
Parise, J. Phys. Chem. C 2016, 120, 360–369; b) W. C. Lee, H. T. Chien, Y.
Lo, H. C. Chiu, T. P. Wang, D. Y. Kang, ACS Appl. Mater. Interfaces 2015, 7,
18353–18361; c) T. Wang, L. Shi, J. Tang, V. Malgras, S. Asahina, G. G.
Liu, H. B. Zhang, X. G. Meng, K. Chang, J. P. He, O. Terasaki, Y. Yamauchi,
J. H. Ye, Nanoscale 2016, 8, 6712–6720.
[29] a) Z. Kang, Y. Peng, Y. Qian, D. Yuan, M. A. Addicoat, T. Heine, Z. Hu, L.
Tee, Z. Guo, D. Zhao, Chem. Mater. 2016, 28, 1277–1285; b) L. Stegba-
uer, M. W. Hahn, A. Jentys, G. Savasci, C. Ochsenfeld, J. A. Lercher, B. V.
Lotsch, Chem. Mater. 2015, 27, 7874–7881.
[30] B. Zhu, C. Shang, Z. Guo, ACS Sustainable Chem. Eng. 2016, 4, 1050–
1057.
[31] R. Janardanan, S. Maksyutov, T. Oda, M. Saito, J. W. Kaiser, A. Ganshin, A.
Stohl, T. Matsunaga, Y. Yoshida, T. Yokota, Geophys. Res. Lett. 2016, 43,
3486–3493.
[32] a) Y. Zhang, S. A. Y. Zou, X. Luo, Z. Li, H. Xia, X. Liu, Y. Mu, J. Mater. Chem.
A 2014, 2, 13422–13430; b) X. Liu, S. A. Y. Zhang, X. Luo, H. Xia, H. Li, Y.
Mu, RSC Adv. 2014, 4, 6447–6453.
[33] N. Huang, X. Chen, R. Krishna, D. Jiang, Angew. Chem. Int. Ed. 2015, 54,
2986–2990; Angew. Chem. 2015, 127, 3029–3033.
[34] R. Gomes, P. Bhanja, A. Bhaumik, Chem. Commun. 2015, 51, 10050–
10053.
[35] B. Wen, J. J. Zhang, S. Z. Zhang, X. Q. Shan, S. U. Khan, B. S. Xing, Envi-
ron. Sci. Technol. 2007, 41, 3165–3171.
[36] a) P. Bhanja, R. Gomes, A. Bhaumik, RSC Adv. 2015, 5, 74916–74923;
b) R. Gomes, A. Bhaumik, J. Solid State Chem. 2015, 222, 7–11.
[37] Y. Zhang, Y. Zhu, J. Guo, S. Gu, Y. Wang, Y. Fu, D. Chen, Y. Lin, G. Yu, C.
Pan, Phys. Chem. Chem. Phys. 2016, 18, 11323–11329.
[38] D. Chen, S. Gu, Y. Fu, Y. Zhu, C. Liu, G. Li, G. Yu, C. Pan, Polym. Chem.
2016, 7, 3416–3422.
[39] J. Ethiraj, F. Bonino, J. G. Vitillo, K. A. Lomachenko, C. Lamberti, H. Re-
insch, K. P. Lillerud, S. Bordiga, ChemSusChem 2016, 9, 713–719.
[40] D. S. Yang, P. Liu, N. Zhang, W. Wei, M. B. Yue, J. M. You, H. Wang, Chem-
CatChem 2014, 6, 3434–3439.
[41] A. Kumbhar, S. Jadhav, R. Shejwal, G. Rashinkar, R. Salunkhe, RSC Adv.
2016, 6, 19612–19619.
[3] Z. Dong, X. Liu, J. Feng, M. Wang, L. Lin, X. Feng, Eur. J. Org. Chem.
2011, 137–142.
[4] a) E. Adbel Aziz Hafez, M. H. Elnagdi, A. G. A. Elagemey, F. M. A. A. El-
Taweel, Heterocycles 1987, 26, 903–907; b) S. R. Trenor, A. R. Shultz, B. J.
Love, T. E. Long, Chem. Rev. 2004, 104, 3059–3078.
[5] K. Hiramoto, A. Nasuhara, K. Michiloshi, T. Kato, K. Kikugawa, Mutat. Res.
1997, 395, 47–56.
[6] A. M. Fouda, Med. Chem. Res. 2016, 25, 1229–1238.
[7] a) M. Puppala, X. Zhao, D. Casemore, B. Zhou, G. Aridoss, S. Narayanapil-
lai, C. Xing, Bioorg. Med. Chem. 2016, 24, 1292–1297; b) P. N. Dube,
M. N. Waghmare, S. N. Mokale, Chem. Biol. Drug Des. 2016, 87, 608–617.
[8] a) K. Ratnakar Reddy, Y. Poornachandra, G. J. Dev, G. Mallareddy, J. B. Na-
nubolu, C. Ganesh Kumar, B. Narsaiah, Bioorg. Med. Chem. Lett. 2015, 25,
2943–2947; b) M. M. Khafagy, A. H. F. A. El-Wahas, F. A. Eid, A. M. El-
Agrody, Farmaco 2002, 57, 715–722.
[9] X. S. Shang, N. T. Li, H. X. Siyang, P. N. Liu, J. Org. Chem. 2015, 80, 4808–
4815.
[10] H. G. Bonacorso, M. B. Rodrigues, W. C. Rosa, L. B. Silva, C. P. Frizzo, N. O.
Zanatta, M. A. P. Martins, J. Fluorine Chem. 2015, 178, 296–305.
[11] B. S. Kumar, N. Srinivasulu, R. H. Udupi, B. Rajitha, Y. T. Reddy, P. N.
Reddy, P. S. Kumar, J. Heterocycl. Chem. 2006, 43, 1691–1693.
[12] M. A. Ibrahim, N. M. El-Gohary, S. Said, J. Heterocycl. Chem. 2016, 53,
117–120.
[13] S. Biswas, A. Dagar, S. M. Mobin, S. Samanta, Org. Biomol. Chem. 2016,
14, 1940–1945.
[14] S. K. Salama, A. F. Darweesh, I. A. Abdelhamid, A. H. M. Elwahy, J. Hetero-
cyclic Chem. 2016, DOI: 10.1002/jhet.2584.
[15] A. A. Kamble, R. R. Kamble, M. N. Kumbar, G. Tegginamath, Med. Chem.
Res. 2016, 25, 1163–1174.
[16] P. Sagar Vijay Kumar, L. Suresh, T. Vinodkumar, B. M. Reddy, G. V. P. Chan-
dramouli, ACS Sustainable Chem. Eng. 2016, 4, 2376–2386.
[17] M. Esmaeilpour, J. Javidi, F. Dehghani, F. N. Dodeji, RSC Adv. 2015, 5,
26625–26633.
[18] S. K. Kundu, J. Mondal, A. Bhaumik, Dalton Trans. 2013, 42, 10515–
10524.
[19] S. Samantaray, D. K. Pradhan, G. Hota, B. G. Mishra, Chem. Eng. J. 2012,
193–194, 1–9.
[42] L. Y. Li, Q. Q. Zeng, Y. X. Yang, H. F. Hu, M. Xu, Z. Guan, Y. H. He, J. Mol.
Catal. B 2015, 122, 1–7.
[43] J. Mondal, A. Modak, M. Nandi, H. Uyama, A. Bhaumik, RSC Adv. 2012, 2,
11306–11317.
[20] B. Das, B. Ravikanth, R. Ramu, K. Laxminarayana, B. V. Rao, J. Mol. Catal.
A 2006, 255, 74–77.
[21] a) Y. Li, S. Bi, F. Liu, S. Wu, J. Hu, L. Wang, H. Liu, Y. Hu, J. Mater. Chem. C
2015, 3, 6876–6881; b) Z. Xiang, R. Mercado, J. M. Huck, H. Wang, Z.
Guo, W. Wang, D. Cao, M. Haranczyk, B. Smit, J. Am. Chem. Soc. 2015,
137, 13301–13307.
Received: July 11, 2016
Published online on && &&, 0000
&
ChemCatChem 2016, 8, 1 – 11
www.chemcatchem.org
10
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

FULL PAPERS
P. Bhanja, S. Chatterjee, A. Bhaumik*
&& – &&
Triazine-Based Porous Organic
Polymer with Good CO2 Gas
Adsorption Properties and an Efficient
Organocatalyst for the One-Pot
Multicomponent Condensation
Reaction
Porous polymer for CO2 capture and
heterogeneous catalysis: A new
porous organic polymer (poly-divinyl-
benzene-co-triallyloxytriazine) has been
synthesized through radical co-polymer-
ization. The polymer showed good CO2
adsorption properties and excellent cat-
alytic activity for the synthesis of 2-
amino-4H-chromenes under microwave
irradiation.
ChemCatChem 2016, 8, 1 – 11
www.chemcatchem.org
11
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ