Luminescent Triazene-Based Covalent Organic Frameworks Functionalized with Imine and Azine: N2 and H2 Sorption and Efficient Removal of Organic Dye Pollutants

Article abstract of DOI:10.1021/acs.cgd.8b01458

Design of adsorbents with high stability and efficiency to achieve rapid uptake and high capacity for dye pollutants is a key challenge in environmental remedies. Herein, we have design and synthesized three triazene-based imine and azine functionalized c

Full text of DOI:10.1021/acs.cgd.8b01458

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Article
Luminescent Triazene Based Covalent Organic Frameworks
Functionalized with Imine and Azine: N2 and H2 Sorption
and Efficient Removal of Organic Dye Pollutants
Satyanarayana K. Konavarapu, and Kumar Biradha
Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.8b01458 • Publication Date (Web): 04 Dec 2018
Downloaded from http://pubs.acs.org on December 5, 2018
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Crystal Growth & Design
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Luminescent Triazene Based Covalent Organic Frameworks
Functionalized with Imine and Azine: N2 and H2 Sorption and
Efficient Removal of Organic Dye Pollutants
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Satyanarayana K. Konavarapu and Kumar Biradha*
Department of Chemistry, Indian Institute of Technology, Kharagpur-721302, India
ABSTRACT: Design of adsorbents with high stability, efficiency to achieve rapid uptake and high capacity for the dye
pollutants is a key challenge in environmental remedies. Herein, we have design and synthesized three triazene based
imine and azine functionalized covalent organic frameworks (COFs 1-3) via the formation of imine bonds by the
condensation of a flexible tripodal tri aldehyde (TFPT) with linear diamines. The COFs are characterized by elemental
analysis, FTIR, Solid-state NMR, TGA, FESEM, TEM and DRS. They exhibit permanent porosity with high surface areas and
N2 uptake capacities of 540, 1600 and 2235 cc/g by COFs 1-3 respectively. They are found to be chemically and thermally
stable and exhibit moderate hydrogen storage capacities. Photophysical studies reveals that, COFs 1-3 exhibited low band
gap values of 3.0, 2.5 and 2.25 eV respectively, indicating their semiconducting nature. All three materials are highly
luminescent and their emission maxima are found to depend on the nature of the diamine linker. Further, COFs 1-3 are
highly stable in water, and function as robust adsorbents, as evidenced by its high rapid uptake capacity (>96%) towards
anionic (MO, CR) and cationic (MB, CV) organic dye pollutants from their respective aqueous solutions (2.5X10-5 M).
The design and synthesis of micro porous materials is an
attractive area of research and caters to the day-to-day
applicative aspects.1-3 The quest for zeolite like materials
with better prospects for fine tuning the nature of cavities,
size, shape and functional properties is ongoing pursuit.
MOFs have been widely explored for their zeolitic
properties in the past two decades.4-6 Subsequently, the
covalent organic frameworks (COFs) which are new class
of materials, built up on covalent bonds, are also gaining
importance for their gas sorption, storage and separation,
catalysis, sensing, drug delivery, energy storage, magnetic
and optoelectronic properties.7-22 Generally, these COFs
are designed using two molecular components that are
linked via boronate,23 boroxine,24 imine,25 azine,26
triazene27 and imide linkages.28 In particular, the COFs
with imine and azine linkages are of wider interest given
their ease of synthesis from simple chemicals, crystallinity
and high stability.29,30 However, unlike MOFs, it is near to
impossible to obtain single crystals of COFs given the
nature of the reactions involved in their formation. To date
only a few single crystal structures of COFs are reported31-
trigonal molecule as it is highly flexible, electron deficient
and contain more number of nitrogen atoms. Recently,
TFPOT was shown to form COFs with p-
phenylenediamine, benzidine and tripodal amine by
Pitchumani et al. and Zhang et al. which exhibit gas
sorption, catalysis and photosensitizer properties.38,39
Further, Li et al. have demonstrated the importance of
interlayer hydrogen bonds in the COFs of TFPT by
introducing the hydrogen bonding functional groups on
the linear diamine linker such as benzidine.40, 41 However,
very limited examples have been reported on exploration
of
COF
towards
dye,
photophysical
and
photoluminescence properties.
Scheme 1. Structural drawings for TFPT, HA, PDA and
DAF
35
and most often the structures are deduced by PXRD,
FESEM, TEM, FTIR, solid state NMR and their other
properties.10,25 Despite of poor crystallinity and lack of
accurate understanding of the structures, they are widely
explored in the fields of gas adsorption, separation,
catalysis and removal of dye pollutants from waste water.36-
37
In this manuscript, we have strategically designed and
synthesized COFs 1-3 of TFPT using three diamine linkers
namely hydrazine monohydrate, p-phenylenediamine and
2,7-diaminofluorene respectively (Scheme-1). The amines
are selected such that they increase the pore size gradually
Several groups have shown that the COFs with triazene
core exhibit more basicity which facilitates binding of
guest molecules, metals and dyes. In this context, 2,4,6-tris
(4-formylphenoxy)-1,3,5-triazine (TFPOT) is an interesting
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Figure 1. FTIR spectra of TEPT, PDA, DAF, COF-1, COF-2 and
COF-3.
and also change the nature of networks given the
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7
8
differences in the chromophores of diamines. Apart from
synthesis and characterization of these COFs, the studies
are aimed at exploring the differences in their porosities,
luminescence and dye sorption properties based on the
diamine linkers. These COFs are found to have excellent
ability for N2 and H2 sorption and also to adsorb both
cationic (methylene blue (MB) and crystal violet (CV), and
anionic (methyl orange (MO) and congo red (CR) dyes.
The band gap values for COFs 1-3 calculated from DRS
indicate their semiconducting nature. The luminescence
studies reveal that the COFs are highly luminescent and
their emissions are found to change with the nature of
diamine linker.
The polymeric nature of the materials has been confirmed
by their lack of solubility in polar solvents such as DMF and
DMSO. Further, they are found to be stable under basic
conditions as they remain intact in 0.1 M NaOH solution
for several days (Figure S8-S10). From TGA it was observed
that COF-1 is stable upto 300 °C, whereas COF-2 & 3 were
stable up to 350 and 390 °C respectively, indicating their
high thermal stability (Figure S11). The FTIR spectra
(Figure 1) indicates the presence of imine group as C=N
stretching frequency appears at 1573, 1569 and 1570 cm-1 for
COFs 1-3 respectively, and absence of the aldehyde (1700
cm-1). Further, the presence of imine linkages reaffirmed
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by C CP-MAS NMR spectra of COFs 1-3. The solid-state
RESULTS AND DISCUSSION
13C NMR spectrum of COFs indicate the presence of imine
and triazene functionalities as all these materials exhibit
signals at ~153 ppm and ~172 ppm respectively (Figure 2).
The trialdehyde TFPT was synthesized by reacting p-
hydroxybenzaldehyde with cyanuric chloride in 3:1 ratio in
the presence of Na2CO3 in benzene. The solvothermal
reactions of TFPT with corresponding diamines such as
hydrazine monohydrate (HA), p-phenylenediamine (PDA)
and 2,7-diaminofluorene (DAF) in 2:3 ratio in the presence
of catalytic amounts of 6 M acetic acid in dioxane-
mesitylene solvent system at 120 °C resulted in the
formation COFs 1-3 respectively. These materials are found
to exhibit different colors light yellow, green and brown by
COFs 1-3, respectively, and are found to be insoluble in
organic solvents such as alcohols, acetone, chloroform,
ethers, acetonitrile, N,N-dimethylformamide (DMF) and
dimethyl sulfoxide (DMSO). The materials are thoroughly
characterized by elemental analysis, FTIR, solid state NMR,
powder XRD, SEM, TEM and DRS. Our efforts to obtain
crystalline materials of these COFs are unsuccessful.
Figure 2. Solid-state 13C NMR spectra for COF-1.
Scheme 2. Probable structure for COF-1, COF-2, and
COF-3
In case of COF-3 the presence of signal at 40 ppm confirms
the presence of sp3 carbon corresponding to 2,7-
diaminofluorene (Figure S12-S14). The PXRD patterns for
COFs 1 and 2 indicate their amorphous nature with some
broad peaks while those of COF-3 exhibit some sharp peaks
in the 2ϴ range of 20-30° (Figure 3). However, indexing of
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Crystal Growth & Design
COF-3 was not successful. To understand the morphology
of COFs, microscopic studies such as FESEM and TEM
have been performed. The FESEM and TEM images
indicate that COFs 1-3 exhibit spherical morphologies
(Figure 4), while their starting materials such as aldehyde
exhibits rod type morphology and amines exhibit plate-like
respectively. These three materials were found to exhibit
three different adsorption isotherms: COF-1 uptakes about
380 cc/g at p/p0 value of 0.15 bar and the uptake gradually
reaches to 540 by p/p0 of 1 bar; COF-2 uptakes about 800
cc/g at p/p0 value of 0.3 bar and the uptake remains
constant up to 0.9 bar and suddenly reached to the 1557
cc/g by 1 bar; whereas the uptake of COF-3 was found to
increase gradually up to 2235 cc/g by the p/p0 of 1 bar.
These sorption isotherm indicate that COF-1 and 2 are
microporous in nature while 3 is meso-porous in nature
(Figure 5a). These N2 sorption values are much better than
the recently reported COFs synthesized by the same
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2
3
4
5
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morphologies (Figure S21).
Based on above
characterizations, the probable structure of COFs 1-3 have
been proposed in Scheme 2.
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aldehyde with PDA.38,39
(a)
(b)
2400
2200
2000
1800
1600
1400
1200
1000
800
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120
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COF-1
COF-2
COF-3
COF-1
COF-2
COF-3
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20
400
200
0
0.2
0.4
0.6
0.8
1.0
0.2
0.4
0.6
0.8
1.0
Relative pressure(p/p0)
Relative pressure(p/p0)
Figure 5. (a) N2 adsorption and desorption isotherms for the
COFs 1-3 at 77 K and one bar; (b) H2 adsorption and
desorption isotherms at 77 K and one bar for the COFs 1-3.
Pore size distribution analysis by fitting the uptake of the
N2 isotherms using the nonlocal density functional theory
(NLDFT) method reveals that COFs 1-3 exhibit average
pore size of 11, 13 and 15 nm (Figure 6). The hydrogen
sorption analysis also reveals the similar trends in the
uptake values that is increase in uptake as the spacer
length increases, COFs 1-3 exhibit 70, 120, and 130 cc/g of
Figure 3. PXRD patterns of TEPT, PDA, DAF, COF-1, COF-2
and COF-3.
uptake respectively (Figure 5b).
isotherms are found to have identical nature for all three
However, the H2
COF-1
COF-2
COF-3
0.8
COFs that is gradual increase of uptake as the p/p0 values
increase.0.6
0.4
0.2
0.0
10
15
20
25
Figure 4. FESEM images for (a) COF-1; (b) COF-2; (c) COF-3;
TEM images for the (d) COFs 1; (e) COF-2; and (f) COF-3.
Pore width (nm)
Gas adsorption studies.
In order to characterize the porous properties of the
resulted COFs, N2 gas sorption studies were conducted on
all the three COFs at 77 K and one bar pressure. The COFs
were activated by soaking the as synthesized materials in
volatile solvents such as THF, acetone or chloroform for
seven days and degasifying at 150 °C under vacuum for 24
h. The N2 adsorption studies reveal that COFs 1-3 exhibited
maximum uptake capacities of 540, 1557, and 2235 cc/g,
respectively, at 77 K and one bar pressure. The BET surface
areas for COFs 1-3 were found to be 853, 2815 and 1798 m²/g
Figure 6. Pore size distribution of COF-1, COF-2, and COF-3.
Diffuse Reflectance Spectra.
The electronic properties of the COFs have been
investigated using the solid state UV-vis spectra in
comparison with those of parent components. Monomers
TFPT, PDA and DAF exhibited absorption bands at 300,
330 and 355 nm respectively (Figure 7a), whereas the COFs
1-3 exhibited absorption bands at 350, 400 and 450 nm
respectively (Figure 7b). The absorption bands of the COFs
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Crystal Growth & Design
2 and 3 are red-shifted compared to the parent diamines.
reducing the energy gap of π-π* transitions.
Page 4 of 8
This
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COFs 2 and-3 exhibited much higher red-shifts by 70 and
95 nm than the parent diamines respectively. Further the
band gap values for COFs 1-3 have been calculated from the
DRS spectra. Interestingly, COFs 1-3 exhibited lower band
gap values 3.0, 2.5 and 2.25 eV, respectively, which clearly
indicates the semiconducting nature of the materials
(Figure S22). These band gap values are comparable and
phenomenon is consistent with recently reported imine
linked porous organic polymers.50, 51
Dye Adsorption Studies.
Water contamination with toxic dyes and other water
soluble organics has been increasing day by day due to the
rapid developments in the industries such as printing,
medicine, leather, textile and fertilizer. Most of the dye
molecules are stable under adverse conditions, non-
biodegradable and their toxicity causes severe problems to
aquatic life.52,53 Thus, removing dyes from waste water
quickly and economically remains a great deal of challenge
(b)
(a)
lower than the reported COF-1 constructed by boroxine
linkage (3.6 eV) and IRMOF (3.73 eV).42-44
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for researchers.
Covalent organic frameworks with
advantages like tunable porosity, high surface area, water
stability and large scale production are envisaged as better
candidates for the removal of organic dyes from waste
water.54-56 Being highly chemical and thermal stable with
high BET surface area and with more nitrogen content, the
utility of COFs 1-3 as potential dye adsorbates from the
aqueous solution has been explored. The dye adsorption
performance of COFs 1-3 were studied by taking two
anionic dyes such as methyl orange (MO), congo red (CR)
and two cationic dyes such as methylene blue (MB) and
crystal violet (CV). The dye sorption experiments were
carried out by immersing 5 mg of COF material in 5 mL of
respective 10-5 M aqueous solutions of dye. The adsorption
was monitored by naked eye as well as by UV-vis spectra of
the aqueous solution at different time intervals.
Interestingly, COFs 1-3 exhibit good capability for the
removal of both anionic (MO & CR) and cationic (MB and
CV) dyes. The dye sorption abilities are found to be in the
order of COF-3 > COF-2 > COF-1, which indicates increase
in dye absorbing ability with the increase in the length of
the spacer. The COF-2 was found to adsorb MO, MB and
CV
Figure 7. Solid-state UV-vis spectra (diffuse reflectance
spectra) for (a) TFPT, PDA and DAF; (b) COFs 1-3
Solid-State Luminescence Properties.
Recently, luminescent MOFs and COFs have been
extensively explored for their applicative aspects such as
light
emitting
diodes,
chemical
sensing
and
optoelectronics.45-47 However, most of the MOFs possess
low hydrothermal stability which limits their industrial
application, whereas COFs are pure organic low dense
materials as they made up of lighter elements and robust
towards air and water. Synthesis of organic polymers by
judicious selection of conjugated organic spacers offers an
efficient methodology for obtaining new type of
electroluminescent
organic
materials.48,49
The
luminescence properties of the COFs 1-3 are studied as they
contain electron rich as well as electron deficient aromatic
moieties. The COFs 1-3 are found to exhibit the emission
maxima at 450, 505 and 540 nm, respectively upon the
excitation at 340 nm (Figure 8b). The diamines exhibited
λ max at 410 and 450 nm for PDA and DAF respectively, with
excitation wavelength of 330 and 340 nm respectively.
Figure 8a), while the TFPT is non-luminescent. The
emission bands of COFs 2 and 3 were red shifted by 95 and
90 nm compared to their parent diamines, respectively.
The observed redshifts for COF 2 and 3
(b)
(a)
COF-1
COF-2
COF-3
1.0
PDA
DAF
0.8
0.6
0.4
0.2
0.0
1.0
0.8
0.6
0.4
0.2
0.0
400 450 500 550 600
Wavelength (nm)
400
450
500
550
600
Wavelength (nm)
Figure 8. Solid-state luminescence spectra for (a) PDA and
DAF; (b) COFs 1-3
-could be due to the restricted motion of the individual
monomer units which leads to enhanced π-conjugation by
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Crystal Growth & Design
(FTIR) spectra were recorded with
a
Perkin-Elmer
1
Instrument Spectrum Rx Serial No. 73713. Elemental
analysis has been carried out by Perkin-Elmer Series II
2400, the diffuse reflectance spectra (DRS) were recorded
with a Cary model 5000 UV-vis-NIR spectrophotometer,
the PXRD patterns were recorded with Bruker D8-advance
diffractometer, 1H NMR spectra was recorded on BRUKER-
AC 400 MHz spectrometer, melting points were taken
using a Fisher Scientific melting point apparatus, Cat.
No.12-144-1, Solid-state luminescence was carried out by
using Spex Fluorolog-3 FL3-22) spectrofluorimeter and
Solid-state NMR was recorded on Varin INOVA 400 MHz
solid state spectroscopy. The absorption of the dye
solution was monitored by Shimadzu UV-1601 UV-vis
spectrophotometer.
Figure 9. UV-vis spectra for the uptake of different dyes from
aqueous solutions at various time intervals by COF-1 (a)
methylene blue; (b) crystal violet; (c) methyl orange; (d) congo
red
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9
-rapidly in first 5 minutes and the adsorption reaches to 98
% in 30 minutes. Whereas the adsorption of CR by COF-2
was found to be somewhat slower and requires about 60
minutes to adsorb 95% of the dye (Figure S23). Similar
trends were observed for the COF-3 also (Figure S24).
However, COF-1 is capable of adsorbing only MO, MB, and
CV sluggishly and requires 60 minutes to adsorb 95%, 92%
and 92% of the dyes respectively (Figure 9). Interestingly,
during the entire process of adsorption and desorption
process of dyes, the COFs 1-3 are found to be stable as in
dictated by their FTIR spectra (Figure S25-S27). The
removal percentages of the dyes have been calculated by
the following equation
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Synthesis of 2,4,6-tris (4-formylphenoxy)-1,3,5-triazine
(TFPOT). TFPOT was prepared by literature procedure p-
hydroxybenzaldehyde (1.6 g, 1.31 mol (1.3 excess)) and
cyanuric chloride (0.6 g, 3.25 mol) were added to a
suspension of Na2CO3 (10 g) in 50 mL of benzene. The
mixture was refluxed for 20 h. The reaction mixture was
then cooled and the solid was removed by filtration and
washed with hot AcOEt twice. The filtrate was extracted
with 10% Na2CO3 twice and with H2O once and the organic
layer was dried over anhydrous Na2SO4 and then
concentrated. The white powder was recrystallized from
20 mL of AcOEt to afford a white fluffy precipitate. IR (KBr)
ν 2833, 1702, 1567, 1361, 1211, 842 cm-l, lH NMR (CDCl3) 6 7.32
(d, 6H, J=8.5 Hz), 7.92 (d, 6H, J=8.5 Hz), 10.00 (S, 3H).
Where E% represents the removal percentage of organic
dyes; C0 and Ce denotes the initial and equilibrium
concentrations (mg/L) of the organic dyes in aqueous
solutions respectively.
CONCLUSIONS.
In summary, three porous triazene based imine and
azine functionalized covalent organic polymers COF-1,
COF-2 and COF-3 were synthesized using imine linkages
between flexible tripodal tri aldehyde (TFPT) and linear
diamines via solvothermal technique. The COFs are shown
to be thermally stable (>350 °C) and exhibited excellent N2
sorption values. The N2 sorption values are found to
increase with increasing the size of the spacer diamine.
The N2 uptake capacities of COF 1-3 are found to be 540,
1557 and 2235 cc/g respectively. The photophysical
properties of COFs 1-3 have been studied which shows
their semiconducting nature with low band gap values of
3.0, 2.5 and 2.25 eV respectively. Further, the luminescent
studies reveals that COFs 1-3 are highly luminescent and
their emission maximas are red-shifted compared to their
parent compounds. Further, the COFs 2 & 3 exhibited high
sorption capacity towards organic dyes such as MO, MB,
CV and CR from aqueous solutions, whereas COF-1
adsorbed MO, MB and CV only.
Synthesis of COF-1. COF-1 was prepared by taking (TFPT)
(44.1 mg, 0.1mmol) and hydrazine monohydrate (7.5 μmL,
0.15 mmol) were suspended in mixed anhydrous 1,4-
dioxane (4.0 mL) and mesitylene (2.0 mL) in the presence
of aqueous acetic acid ( 6.0 M) in a Pyrex tube. The sealed
tube was heated at 120° C for 3 days to yield a light yellow
solid, which was filtered and washed with THF, acetone
and methanol and ethyl acetate to remove any unreacted
building unit. The resulting powder was dried in vacuum.
Melting point of the material is above 320 °C elemental
analysis calcd (%) for C30H25N6O3: C 75.45, H 5.86, N 13.56;
found: C 76.49, H 4.98, N 14.23. FTIR (KBr): ν = 1573 (C=N),
1504, 1360, 1202, 1165, 1015, 1013, 806, 623 and 511 cm-1; Solid
13
state; C NMR: d= 153 (C=N), 172, 162, 161, 153, 131, 127 and
122 ppm.
Synthesis of COF-2. COF-2 was prepared by following
same procedure instead of hydrazine, p-phenylenediamine
was taken which resulted as light green color solid.
Melting point of the material was above 320 °C, elemental
analysis calcd (%) for C40H28N6O3: C 79.55, H 6.76, N 12.66;
found: C 78.89, H 7.48, N 13.23. FTIR (KBr): ν = 1569 (C=N),
2367, 1698, 1362, 1211, 1162, and 840 cm-1. Solid state 13C
NMR: d= 154 (C=N), 192, 172, 145, 134, and 121 ppm.
EXPERIMENTAL DETAILS
All
the
reagents
and
solvents
like
N,N′-
dimethylformamide,
dimethyl
sulfoxide,
dioxane
mesitylene, benzene, acetic acid, ethyl acetate Na2CO3 p-
hydroxybenzaldehyde, hydrazine monohydride, p-
phenylenediamine were purchased from local chemical
suppliers and used further distilled the solvents. The
solvents like methanol, THF, chloroform, acetone and
acetonitrile were HPLC grade. 2,7-diaminofluorene and
cyanuric chloride were purchased from Sigma-Aldrich.
Synthesis of COF-3. COF-3 was prepared following
same procedure instead of hydrazine, 2,7-diaminofluorene
was used and resulted as brown color solid melting of the
solid was above 320 °C. Elemental analysis calcd
C25H15N6O3: C55.65, H 3.76, N 12.36; found: C 56.26, H 3.20,
N 13.34: FTIR (KBr): ν = 1570 (C=N), 3421, 2344, 2362, 1363,
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1205, 1159, and 806 cm-1. Solid state 13C NMR: d= 154 (C=N),
44, 122, 129, 134, 148, 153 and 173 ppm
4) Liu, J.; Thallapally, P. K.; McGrail, B. P.; Brown, D. R.;
Liu, J. Progress in Adsorption-Based CO2 Capture by
Metal-Organic Frameworks. Chem. Soc.Rev. 2012, 41,
2308-2322.
1
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3
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7
8
Field Emission Scanning Electron Microscope
(FESEM). A field emission scanning electron microscope
(FESEM, Zeiss, Supra- 40) operating at 5-10 kV was used to
obtain the micrograph. For electron micrographs, the
polymer samples were dispersed in MeOH and drop casted
on the aluminum foil, allowed to dry at room temperature,
and then dried in desiccators for 24 h. A layer of gold was
sputtered on top to make a conducting surface, and finally,
the specimen was transferred into the microscope.
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Transmission Electron Microscope (TEM): The
polymer materials were examined by a transmission
electron microscope (FEI-TECNAIG20S-TWIN, Type-
5022/22). The sample was prepared by placing a drop of
MeOH dispersed material on a carbon-coated copper grid.
Gas Sorption Study. Powdered polymer materials have
been used for the gas adsorption study. The polymer
materials have been dried under vacuum for the gas
adsorption study. The gas sorption experiment was
performed using a Quantacrome autosorb iQ automated
gas sorption analyzer. Generally, 20-25 mg of sample was
taken in a 6 mm sample holder without a rod. Prior to the
sorption experiment, the samples were employed for
degassing at 150 °C under vacuum for 24 h
10) Lohse, M. S.; Bein, T. Covalent Organic Frameworks:
Structures, Synthesis, and Applications. Adv. Funct.
Mater. 2018, 28, 1705553.
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Frameworks (COFs): Perspectives of Industrialization.
CrystEngComm, 2018, 20, 1613-1634.
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Methane, and Carbon Dioxide in Highly Porous
Covalent Organic Frameworks for Clean Energy
Applications. J. Am. Chem. Soc. 2009, 131, 8875-8883.
13) Rabbani, M. G.; Sekizkardes, A. K.; Kahveci, Z.; Reich,
T. E.; Ding, R.; El-Kaderi, H. M. A 2D Mesoporous
Imine-Linked Covalent Organic Framework for High
Pressure Gas Storage Applications. Chem. Eur. J. 2013,
19, 3324-3328.
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Ochsenfeld, C.; Lercher, J. A.; Lotsch, B. V. Tunable
Water and CO2 Sorption Properties in Isostructural
Azine-Based Covalent Organic Frameworks Through
Polarity Engineering. Chem. Mater. 2015, 27, 7874-
7881.
ASSOCIATED CONTENT
Supporting Information. The Supporting Information is
available free of charge via the Internet at
http://pubs.acs.org.”
FTIR, XRPD, solid-state 13C NMR analysis, TGA
profile, SEM, TEM images, band gap calculations and dye
adsorption studies. (PDF)
AUTHOR INFORMATION
Corresponding Author
15) Peng, Y.; Huang, Y.; Zhu, Y.; Chen, B.; Wang, L.; Lai, Z.;
Zhang, Z.; Zhao, M.; Tan, C.; Yang, N.; Shao, F.; Han,
Y.; Zhang, H. Ultrathin Two-Dimensional Covalent
Organic Framework Nano sheets: Preparation and
Application in Highly Sensitive and Selective DNA
Detection. J. Am. Chem. Soc. 2017, 139, 8698-8704.
16) Mitra, S.; Sasmal, H. S.; Kundu, T.; Kandambeth, S.;
Illath, K.; Díaz, D. D.; Banerjee, R. Targeted Drug
Delivery in Covalent Organic Nano sheets (CONs) via
Sequential Post-synthetic Modification. J. Am. Chem.
Soc. 2017, 139, 4513-4520.
17) Spitler, E. L.; Dichtel, W.; Lewis, R. Acid-catalyzed
Formation of Two-dimensional Phthalocyanine
Covalent Organic Frameworks. Nat. Chem. 2010, 2,
672-677.
18) Sun, B.; Zhu, C. H.; Liu, Y.; Wang, C.; Wan, L. J.; Wang,
D. Oriented Covalent Organic Framework Film on
Graphene for Robust Ambipolar Vertical Organic
Field-Effect Transistor. Chem. Mater. 2017, 29, 4367-
4374.
*E-mail: kbiradha@chem.iitkgp.ernet.in. Fax: +91-3222-
282252. Tel: +91-3222-283346.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
We acknowledge SERB, New Delhi, India, for financial
support, and DST-FIST for the single crystal X-ray
diffractometer. S N K. K acknowledges UGC and IIT KGP, and
thank IIT KGP for a research fellowship. We thank Dr.
Subrahmanya Sarma
measurement.
A V (IICT) for solid-state NMR
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SYNOPSIS TOC
Three triazene based imine and azine functionalized covalent organic frameworks (COFs 1-3) have been designed
and synthesized via the formation of imine bonds from the condensation of a flexible tripodal tri aldehyde (TFPT)
and linear diamines and characterized by different techniques . The gas and dye adsorption of COFs 1-3 have been
explored successfully. Further their luminescence and photo physical properties have been studied.
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