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Novel Nitrogen and Sulfur Rich Hypercrosslinked Microporous Poly-Triazine-Thiophene Copolymer for Superior CO2 Capture Sudipta K Kundu, and Asim Bhaumik ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.6b00262 • Publication Date (Web): 12 Jun 2016 Downloaded from http://pubs.acs.org on June 17, 2016

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ACS Sustainable Chemistry & Engineering

Novel Nitrogen and Sulfur Rich Hypercrosslinked Microporous Poly-Triazine-Thiophene Copolymer for Superior CO2 Capture Sudipta K. Kundu and Asim Bhaumik* Department of Materials Science, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur 700 032, India, *Corresponding author. E-mail: [email protected]

Abstract A novel synthetic strategy has been developed for the preparation of hypercrossliked microporous copolymers, HMC-1, HMC-2 and HMC-3 by using 2,4,6-tri(thiophen-2-yl)1,3,5-triazine and thiophene monomers in their different molar ratios in the presence of anhydrous FeCl3 in chloroform under solvothermal conditions at 150 oC. These polymers are highly porous and robust materials, exhibiting very high BET surface areas and supermicroporosity. The presence of triazine and thiophene moieties within the copolymer network increases the electron donating basic N and S sites in the porous frameworks. Thus, these porous polymers displayed efficient adsorption of Lewis acidic CO2 molecules and show good CO2/N2 adsorption selectivity. The maximum CO2 uptake of 14.2 mmol g-1 at 273 K under 3 bar pressure has been observed. Keywords: Hypercrossliked microporous copolymer; poly-thiophene; copolymer; CO2 storage; CO2/N2 adsorption selectivity.

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INTRODUCTION In the recent years the design and synthesis of carbon dioxide storage materials is attracting increasing attention as carbon capture and sequestration (CCS)1,2 is one of the key technologies to get rid of the harmful effects of global warming caused a result of anthropogenic CO2 emission. The production of CO2 due to the burning of fossil fuels, exhausts from chemical industry, transportation sectors and power plants has been increasing day by day.3 Thus, one of the major scientific challenges to protect the environment is to develop new efficient solid adsorbents for CO2 capture and storage. The traditional CO2 capture is based on the chemical absorption of CO2 using alkanolamine solvents.4-6 However, these chemisorption techniques suffer from several disadvantages such as high energy consumption, volatility of the solvent, solvent regeneration, the corrosion of the equipment, toxicity7,8 and also regeneration process and recovery of CO2 is highly expensive.9 A promising alternative CO2 capture technology is the use of porous polymers due to their high CO2 adsorption capacity through reversible physisorption under the influence of temperature and pressure,10-12 and low regeneration energy.13 In this context, a wide range of materials including crystalline polymers like covalent organic frameworks (COFs)14-16 and amorphous polymers such as porous aromatic frameworks (PAFs)/ polymeric organic frameworks (POFs),17-21 conjugated microporous polymers (CMPs),22-24 porous organic polymers with porphyrin,25-27 triazine,28-31 benzimidazole,32-34 borazine,35 phenyl,36 and thiazolothiazole37 building blocks and other solid sorbents like carbon-based sorbents38-41, zeolites42,43 and polyvinyl amine/chitosan/graphene oxide mixed matrix membrane44 etc have been invented in the recent times. Apart from high specific surface area, narrow pore size distribution, very low skeleton density and surface basicity, the presence of the large amount of heteroatoms in the microporous polymer network increases CO2 adsorption capabilities due to local-dipole2 ACS Paragon Plus Environment

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quadrupole interactions between the polymer skeleton and CO2 molecules.45-47 Besides the CO2 capture capacity, the CO2/N2 selectivity is an important parameter for CCS applications of CO2 sorbents. CO2 is produced as a part of flue gas (containing ~70% N2 and ~15 % CO2 under ~1 bar) in many industrial processes. Thus, high selectivity for CO2/N2 is very demanding for its separation from flue gas mixture. The thiophene-based oxidative coupling reaction in the presence of cheap, readily available Lewis acid FeCl3 as catalyst are the common method for the preparation of hypercrosslinked microporous organic polymers. These organic polymers show high physicochemical stability, excellent chemical robustness and synthetic diversity. Oxidative polymerizations of 1,3,5-tris(2-thienyl)benzene monomer has been carried out in the presence of FeCl3 oxidant for the synthesis of microporous polymeric networks.48 Han’s group have developed microporous polycarbazole through oxidative coupling polymerization, which showed CO2 uptake capacity up to 21.2 wt% (4.82 mmol g-1) at 1 bar and 273 K.49 Recently, Dai et.al have designed a new triazine and carbazole bifunctionalized task-specific polymer which exhibits CO2 uptake of 18 wt% (4.1 mmol g-1) at 1 bar and 273 K.50 Tan et al have reported that the N, O and S-containing heterocyclic microporous organic polymers exhibit maximum CO2 uptake of 2.71 mmol g-1, 2.21 mmol g-1 and 2.88 mmol g-1, respectively at 1 bar and 273 K.51 Herein, we report a new strategy for the incorporation of triazine and thiophene moieties inside the hypercrosslinked microporous copolymers, HMC-1/2/3 by using different molar ratios of the two constituent monomers in the presence of anhydrous FeCl3 in chloroform under solvothermal conditions at 150 oC (Scheme.1). In this work, we first proposed that chloroform takes part in the formation of hypercrosslinked microporous copolymer under these conditions. These polymers were thoroughly characterized by powder XRD, N2 sorption, HR TEM, FE SEM,

13

C CP-MAS NMR spectroscopy. Owing to



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incorporation of triazine and thiophene moieties in the polymer networks, the binding affinity between pore walls and CO2 molecules has been enhanced and these polymers also display good CO2/N2 selectivity. The CO2 uptake capacities of these polymers are studied at two different temperatures to understand the nature of adsorbent-adsorbate interactions and to measure the isosteric heat of adsorption. EXPERIMENTAL SECTION Synthesis of copolymer: In a typical experimental procedure, anhydrous ferric chloride (5.33 mmol, 0.864 g) was taken in 50 mL flame-dried round bottom flask containing 15 mL dried chloroform and this RB flask was equipped with a dropping funnel and it was kept under stirring at N2 atmosphere. Then 2,4,6-tri(thiophen-2-yl)-1,3,5-triazine (0.33 mmol, 0.109 g)

Scheme 1. Synthesis of hypercrosslinked microporous copolymers (HMCs). 4 ACS Paragon Plus Environment

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and thiophene (0.33 mmol, 0.028 g) was dissolved in another 15 mL dried chloroform. The solution was taken in dropping funnel and it was added dropwise under stirring condition at room temperature (25 oC). Immediately, after the addition of the monomers a precipitate was formed and it was stirred under N2 atmosphere for 24 h. Then it was transferred to Teflonlined autoclave and kept at 150 oC for 48 h (Scheme 1). After cooling to room temperature the final precipitated solid was filtered and washed successively with methanol, acetone and dichloromethane and then vacuum dried in an oven at 80 oC for another 24 h. The material was again washed by Soxhlet extraction for 48 h with methanol to give 0.17 g of copolymer. Total three polymer samples were synthesized by using different molar ratios of 2,4,6tri(thiophen-2-yl)-1,3,5-triazine (TTPT) and thiophene (1:1 for HMC-1, 1:2 for HMC-2 and 2:1 for HMC-3). MATERIALS AND CHARACTERIZATIONS Thiophene was purchased from Sigma-Aldrich, India. Triflic acid was procured from Spectrochem, India. 2,4,6-tri(thiophen-2-yl)-1,3,5-triazine was synthesized from thiophene-2carbonitrile (see ESI). Dichloromethane, chloroform and anhydrous ferric chloride was obtained from Merck, India. Dichloromethane and chloroform are dried before using. Powder X-ray diffraction pattern of microporous copolymer materials was recorded on a Bruker D-8 Advance SWAX diffractometer operated at a voltage of 40 kV and a current of 40 mA and calibrated with a standard silicon sample, using Ni-filtered Cu-Kα (λ = 0.15406 nm). FT-IR spectra of the samples were recorded using a Perkin-Elmer spectrum 100 spectrophotometer. N2 adsorption/desorption isotherms were obtained by using a Quantachrome autosorb-1C at 77 K. CO2 uptake ability was performed by using a Bel Japan Inc. Belsorp-HP instrument at 273 K and 298 K up to 3 bar. Prior to the analysis, samples were degassed overnight at 140 o

C. JEOL JEM 6700F field emission scanning electron microscope (FE SEM) was used for

the determination of morphology of copolymer samples. The pore structure was visualized by 5 ACS Paragon Plus Environment


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using a JEOL JEM 2010 high resolution transmission electron microscope (HR TEM) operated at an accelerating voltage of 200 kV. The solid state 13C CP-MAS NMR spectra of the samples were taken in Bruker AscendTM 400 spectrometer. RESULT AND DISCUSSION The wide angle powder XRD patterns (Figure S1) of the polymers show very poor intensity broad peaks indicating amorphous nature of these hypercrossliked polymers. The porosities, surface areas and pore size distributions of all polymers were measured using N2 adsorptiondesorption analysis at 77 K, as shown in Figure 1. All the materials were activated by degassing at 150 oC under vacuum for 12 h. The isotherm shows type I reversible isotherm with a large N2 uptake below relative pressure P/Po = 0.1 suggesting permanent microporosity nature of the polymers. According to IUPAC classification,52 all the polymers are typical microporous materials. These N2 sorption analyses revealed BET (BrunauerEmmett-Teller) surface area (SBET) of 855, 425 and 566 m2 g-1 for HMC-1, HMC-2 and HMC-3, respectively. When the polymer was prepared under same reaction condition using only 2,4,6-tri(thiophen-2-yl)-1,3,5-triazine as monomer, it showed very poor BET surface area (only 6 m2 g-1). Here, low surface area of the material indicates lower crosslinking. Thiophene rings of TTPT are reluctant to react with chloroform through radical reaction due to electron deficient nature of triazine moiety, which reduce the electron density of the thiophene rings. We have measured the surface area of the polymers which have been produced before the solvothermal step, but the surface area is very low due to incomplete crosslinking. However, for solvothermally synthesized HMC-1 when 1:1 molar ratio of monomers TTPT and thiophene is used, we observed maximum surface area. This could be attributed to the fact that extended hypercrosslinking can occur not only from these monomers but also chloroform molecules takes part in the formation of copolymers. This resulted in extended crosslinking and it favours more when 1:1 molar ratio of monomers was 6 ACS Paragon Plus Environment

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taken to synthesize the copolymer. Pore size distributions of these polymers have been calculated from non local density functional theory (NLDFT) method. The pore size distributions of these polymers (Fig. 1B) using carbon slit pore model at 77 K show unimodal porosity with extra large micropore of 1.5 nm for all cases. HMC-1, 2 and 3 show the total pore volume of 0.2968 cc g-1, 0.1920 cc g-1 and 0.1618 cc g-1, respectively at P/Po = 0.9994.

Figure 1 N2 adsorption/desorption isotherms at 77 K of microporous polymers (A). Filled circles represent adsorption points and empty ones represent desorption points. Pore size distributions calculated from NLDFT method of these polymers (B). We have investigated the morphology of HMC-1, HMC-2 and HMC-3 microporous copolymer by HR TEM analysis and the results are shown in Figure 2. The TEM images of HMC-1 suggested typically inter-linking ribbon like porous networks. The length of these ribbons varied from ca. 15-50 µm with widths of ca. 0.8-3.0 µm. These ribbons are randomly oriented to form fine micropores in the polymeric network (Fig. 2B-C). The HR TEM images 7 ACS Paragon Plus Environment


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Figure 2. HR TEM images (A-C), (D-F) and (G-I) of HMC-1, HMC-2 and HMC-3 microporous polymers, respectively.

Figure 3. FE SEM images (A, B and C) of HMC-1, HMC-2 and HMC-3 microporous polymers, respectively. of HMC-2 (Fig. 2D-F) and HMC-3 (Fig. 2G-I) also displayed similar crosslinking ribbon like morphologies. FE SEM images of HMC-1, HMC-2 and HMC-3 are shown in Figure 3. SEM image of HMC-1 (Fig. 3A) further showed interlinked ribbon like morphology. In some


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places these ribbons assembled together to form larger particles. SEM images of HMC-2 (Fig. 3B) and HMC-3 (Fig. 3C) also displayed similar particle morphologies. The presence of triazine and thiophene functionality is confirmed from the FTIR spectra of polymers, as shown in Figure 4. The spectra show two strong absorption bands at 1505 cm-1 and 1370 cm-1 represent the aromatic C-N stretching and ‘breathing’ modes in the triazine units, respectively.53 The other absorption bands appear at 3090 cm-1 (sp2 C-H stretching of thiophene), 1624 cm-1 (thiophene C=C bond stretching) and 821 cm-1 (thiophene C-S bond stretching) indicate the presence of thiophene units in the copolymer networks. Whereas sp3 C-H bond stretching frequency at 2923 cm-1 confirms that chloroform also reacts with thiophene units at high temperature. The absorption band at 3428 cm-1 is exhibited due to O-H bond stretching of the absorbed moisture in the copolymer networks. We have characterized the materials produced before solvothermal treatment by FTIR spectroscopy. The FTIR spectra of these materials are shown in Figure S2.

Figure 4. FT IR spectra of the microporous polymers. The structural integrity of these microporous polymers, HMC-1, HMC-2 and HMC-3 is confirmed by solid state 13C CP-MAS NMR, shown in Figure 5. Each spectrum shows four peaks at 50.9 ppm, 130.9 ppm, 141.9 ppm and 168.9 ppm. As shown in Figure 5, the signal at 50.9 ppm could be attributed for the alkyl carbon suggesting that CHCl3 also takes part in the 9 ACS Paragon Plus Environment


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polymerization process.54 The signals at 130.9 ppm can be assigned for C2 and C3 carbons and 141.9 ppm can be assigned for C1 carbon (directly attached to triazine unit) of thiophene rings. The peak at 168.9 ppm is owing to the most deshielded carbon of triazine rings.

Figure 5. Probable structures of the copolymers and their 13C CP-MAS NMR spectra. The thermal stability of all microporous polymers were investigated by thermogravimetric (TG) analysis under air with heating rate of 10 oC min-1. As shown in Figure S3, for HMC-1 copolymer, only 17 % weight loss was occurred up to 300 oC. After 450 oC, a sharp decrease of weight was occurred due to decomposition of organic framework. In Figure S4, HMC-2 reveals 2 % weight loss at 47 oC due to removal of water molecules adsorbed within the porous framework. After 350 oC temperature, three distinct exothermic weight losses are observed. These exothermic weight losses (total 78 %) in the range 350 oC to 560 oC 10 ACS Paragon Plus Environment

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corresponding to the breaking of C-C, C-N and C-S bonds present in the framework. In Figure S5, TGA plot of HMC-3 shows 10 % weight loss up to 60 oC due to removal of moisture adsorbed in the porous frameworks. Beyond the temperature 320 oC, the material loses its weight sharply for the decomposition of organic framework. Elemental analysis of the HMCs suggested that these porous polymers are nitrogen (5.06-5.90%) and sulfur (27.1728.04%) rich (Table S1). Elemental analyses of HMCs show that experimental values are slightly less than theoretical values. The deviations are mainly due to inclusion of guest molecules in the polymer frameworks,55,56 which is further confirmed by weight loss before 100 oC in TGA curves (Figure S3-S5). Plausible structure of the materials. We have proposed the plausible structure of hypercrossliked microporous copolymer (HMC) from the FTIR (Figure 4) and solid state 13C CP-MAS NMR spectral analysis (Figure 5). Both spectroscopic results suggested that chloroform solvent reacts with thiophene units via chloromethane radical to form the hypercrosslinked microporous copolymers.54 In the first step during stirring at room temperature for 24 h, oligomers are formed and ferric chloride is reduced to ferrous chloride.57,58 Under solvothermal conditions chloromethane radical is formed through the reaction of chloroform and ferrous chloride at 150 oC temperature. This chloromethane radical reacts with thiophene units to give hypercrosslinked copolymer. We have measured the BET surface areas of the polymers which are produced before the solvothermal step at room temperature. But the surface area of the polymer was very low due to incomplete crosslinking. We have also measured the surface areas of the polymers which are produced after solvothermal treatments at 80 and 120 oC. But not much improvement in the BET surface area of the polymers are observed. When the solvothermal temperature was raised to150 oC, we got the polymer with maximum surface areas and thus this was the optimum synthesis conditions. Here, surface area increases with increasing solvothermal temperature as the 11 ACS Paragon Plus Environment


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extent of crosslinking increases via chloroform moiety in the framework. Under solvothermal conditions in autoclave at 150 oC temperature chloroform increases extend of crosslinking, resulting in the formation of interconnected ribbons. This could be the origin of large micropores in the polymer networks. We have proposed a plausible reaction mechanism in Figure S6 (supporting information). Thus, elevated synthesis temperature and the presence of chloroform are necessary for complete polymerization and extended crosslinking, and these are the most crucial parameters except the feed ratio of the monomers (TTPT and thiophene) for the formation of micropores. Table 1. Physical characteristics and CO2 adsorption capacity of hypercrosslinked microporous copolymers. Copolymers

TTPT : SBET Thiophene (m2 g-1)

Pore Size (nm)

Vtotal (cc g-1)

CO2 uptake (mmol g-1) under 3 bar 273 K 298 K

CO2/N2 selectivity (initial slope, 273 K)

HMC-1

1:1

855

1.5

0.2968

10.5

2.4

72:1

HMC-2

1:2

425

1.5

0.1920

13.7

1.9

70:1

HMC-3

2:1

566

1.5

0.1618

14.2

2.6

23:1


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Figure 6. CO2 adsorption-desorption isotherms of HMC-1/2 and 3 at 273 and at 298 K. The high surface areas and low pore size distributions with N, S-rich surface in these polymers inspired us to investigate the CO2 uptake capacity over the polymers. CO2 adsorption isotherms of microporous copolymer, HMC-1, HMC-2 and HMC-3 at 273 K and at 298 K are depicted in Figure 6. It can be seen that the CO2 uptake capacity increases monotonically with increasing CO2 pressure but, the rate of adsorption decreases at the high pressure. These microporous copolymers exhibit very high CO2 uptake, which are in the ranges of 10.5-14.2 mmol g-1 and 1.9-2.6 mmol g-1 at 273 K and 298 K, respectively under 3 bar pressure (Table 1). HMC-3 copolymer exhibits highest CO2 uptake, up to 14.2 mmol g-1 and 2.6 mmol g-1 at 273 K and 298 K respectively, under 3 bar pressure, which is the best among the known other thiophene based hypercrosslinked microporous materials.51 Furthermore, we have measured CO2 isotherms at two other temperatures, 288 and 308 K. These CO2 isotherms are shown in Figure S7A-C (Table S2). The presences of N and S 13 ACS Paragon Plus Environment


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atoms in the polymer networks are the responsible for the CO2 adsortion due to dipolequadrupole interactions between the polymer skeleton and CO2 molecules.59 It is pertinent to mention that although HMC-3 has medium surface area, it has highest CO2 storage capacity than HMC-1 and HMC-2. This could be attributed to the fact that HMC-3 has the highest N

Figure 7 Recycling efficiencies of HMC-1/2/3 for the CO2 adsorption at 273 K. and S contents in its polymer network (Table S1). The reversible natures of these isotherms indicated the absence of chemisorption of CO2 over HMC-1/2/3. The isosteric heat of adsorption (Qst) is calculated from the CO2 isotherms measured at 273, 288, 298 and 308 K temperature by using Clausius-Clapeyron equation. The isosteric heats of adsorption are plotted as a function of amount of CO2 uptake in Figure S8. These Qst values are below the energy of the chemical bond formation, but quite high heat of adsorption due to presence of triazine rings suggested the strong physisorptions of CO2 molecules at the surface of the copolymers. Reversible nature of these physisorption isotherms suggested facile release of CO2 upon release in pressure. The reproducibility of CO2 sorption uptakes for HMC-1, 2 and 3 materials are very high as seen from the uptakes after five consecutive adsorption14 ACS Paragon Plus Environment

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desorption cycles (Figure 7). Further, along with the CO2 uptake capacity over the hypercrosslinked microporous polymers, we have investigated the selectivity for gases over these copolymer networks. To examine the separation abilities of HMCs, N2 and CO2 sorption experiments were carried out at 273 K and 1 bar. The CO2/N2 selectivity for HMCs was calculated using the ratio of the initial slopes of the CO2 and N2 adsorption isotherms at 273 K and 1 bar. From these data, the calculated CO2/N2 selectivities of HMC-1, HMC-2 and HMC-3 were 72:1, 70:1 and 23:1, respectively at 273 K (Figures S9, S10 and S11). In Table S3 we have summarized the BET surface area, CO2 uptake and CO2/N2 selectivity of various porous organic materials. As seen from this table that these hypercrosslinked microporous poly-triazine-thiophene copolymers displayed relatively higher CO2 uptakes and comparable CO2/N2 selectivity over the related organic polymers. These results suggest that HMCs have good selectivity for the adsorption of CO2 over N2 and thus they have the potential for the selective removal of CO2 from flue gases. CONCLUSION In conclusion, we have reported a novel solvothermal method for the synthesis of Nand S-rich microporous triazine-based polythiophene copolymers having high BET surface area and good thermal stability. These hypercrosslinked polymers displayed excellent CO2 uptakes (14.2 mmol g-1 at 273 K/3 bar) and good gas adsorption selectivity of CO2 over N2. Very high CO2 uptakes and good selectivity for CO2/N2 suggested exciting future potential of these microporous polymers as selective adsorbent for the environmental clean-up. ASSOCIATED CONTENT Supporting Information



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Elemental analysis of HMCs, Wide angle powder XRD pattern, TG-DTA data, plausible reaction mechanism, Isosteric heat of adsorption and selectivity curves are provided here. This information is available free of charge via the Internet at http://pubs.acs.org/. AUTHOR INFORMATION Corresponding Author *Email: [email protected] Tel: 91-33-2473-4971 Fax: 91-33-2473-2805. Notes The authors declare no competing financial interest. ACKNOWLEDGMENT SKK thanks CSIR, New Delhi for his senior research fellowship. AB thanks DST, New Delhi for providing instrumental facility through the DST unit on nanoscience and DST-SERB project grants.


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References (1)

Pera-Titus, M. Porous Inorganic Membranes for CO2 Capture: Present and Prospects. Chem. Rev. 2014, 114, 1413-1492.

(2)

Chu, S. Carbon Capture and Sequestration. Science 2009, 325, 1599.

(3)

Haszeldine, R. S. Carbon Capture and Storage: How Green Can Black Be? Science 2009, 325, 1647-1650.

(4)

Hu, Y. L.; Verdegaal, W. M.; Yu S. H.; Jiang, H. L. Alkylamine-Tethered Stable Metal-Organic Framework for CO2 Capture from Flue Gas. ChemSusChem. 2014, 7, 734-737.

(5)

Rochelle, G. T. Amine Scrubbing for CO2 Capture. Science 2009, 325, 1652-1654.

(6)

Kim, D. Y.; Lee, H. M.; Min, S. K.; Cho, Y.; Hwang, I.-C.; Han, K.; Kim, J. Y.; Kim, K. S. CO2 Capturing Mechanism in Aqueous Ammonia: NH3-Driven DecompositionRecombination Pathway. J. Phys. Chem. Lett. 2011, 2, 689-694.

(7)

Banerjee, R; Furukawa, H.; Britt, D.; Knobler, C.; O’Keeffe, M.; Yaghi, O. M. Control of Pore Size and Functionality in Isoreticular Zeolitic Imidazolate Frameworks and their Carbon Dioxide Selective Capture Properties. J. Am. Chem. Soc. 2009, 131, 38753882.

(8)

Saleh, M.; Lee, H. M.; Kemp, K. C.; Kim, K. S. Highly Stable CO2/N2 and CO2/CH4 Selectivity in Hyper-Cross-Linked Heterocyclic Porous Polymers. ACS Appl. Mater. Interfaces 2014, 6, 7325-7333.

(9)

Woodward, R. T.; Stevens, L. A.; Dawson, R.; Vijayaraghavan, M.; Hasell, T.; Silverwood, I. P.; Ewing, A. V.; Ratvijitvech, T.; Exley, J. D.; Chong, S. Y.; Blanc, F.; Adams, D. J.; Kazarian, S. G.; Snape, C. E.; Drage, T. C.; Cooper, A. I. Swellable, Water- and Acid-Tolerant Polymer Sponges for Chemoselective Carbon Dioxide



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Capture. 2014, 136, 9028-9035. (10) Guillerm, V.; Weselinski, L. J.; Alkordi, M.; Mohideen, M. I. H.; Belmabkhout, Y.; Cairns, A. J.; Eddaoudi, M. Porous organic polymers with anchored aldehydes: a new platform for post-synthetic amine functionalization en route for enhanced CO2 adsorption properties. Chem. Commun. 2014, 50, 1937-1940. (11) D’Alessandro, D. M.; Smit, B.; Long, J. R. Carbon Dioxide Capture: Prospects for New Materials. Angew. Chem., Int. Ed. 2010, 49, 6058-6082. (12) Dawson, R.; Cooper, A. I.; Adams, D. J. Chemical functionalization strategies for carbon dioxide capture inmicroporous organic polymers. Polym. Int. 2013, 62, 345352. (13) Li, P. Z.; Wang, X. J.; Zhang, K.; Nalaparaju, A.; Zou, R. Y.; Zou, R. Q.; Jiang, J. W.; Zhao, Y. L. ‘‘Click’’-extended nitrogen-rich metal-organic frameworks and their high performance in CO2-selective capture. Chem. Commun. 2014, 50, 4683-4685. (14) Furukawa, H.; Yaghi, O. M. Storage of Hydrogen, Methane, and Carbon Dioxide in Highly Porous Covalent Organic Frameworks for Clean Energy Applications. J. Am. Chem. Soc. 2009, 131, 8875-8883. (15) Patel, H. A.; Je, S. H.; Park, J.; Jung, Y.; Coskun, A.; Yavuz, C. T. Directing the Structural Features of N2-Phobic Nanoporous Covalent Organic Polymers for CO2 Capture and Separation. Chem. Eur. J. 2014, 20, 772-780. (16) Huang, N.; Chen, X.; Krishna, R.; Jiang, D. L. Two-Dimensional Covalent Organic Frameworks for Carbon Dioxide Capture through Channel-Wall Functionalization. Angew. Chem. Int. Ed. 2015, 54, 2986-2990. (17) Ben, T.; Ren, H.; Ma, S.; Cao, D.; Lan, J.; Jing, X.; Wang, W.; Xu, J.; Deng, F.; Simmons, J. M.; Qiu, S.; Zhu, G. Targeted Synthesis of a Porous Aromatic Framework with High Stability and Exceptionally High Surface Area. Angew. Chem., Int. Ed.


Page 18 of 24

Page 19 of 24

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2009, 48, 9457. (18) Ma, H.; Ren, H.; Zou, X.; Sun, F.; Yan, Z.; Cai, K.; Wang, D.; Zhu, G. Novel lithiumloaded porous aromatic framework for efficient CO2 and H2 uptake. J. Mater. Chem. A, 2013, 1, 752-758. (19) Ben, T.; Li, Y.; Zhu, L.; Zhang, D.; Cao, D.; Xiang, Z.; Yao, X.; Qiu, S. Selective adsorption of carbon dioxide by carbonized porous aromatic framework (PAF). Energy Environ. Sci. 2012, 5, 8370-8376. (20) Katsoulidis, A. P.; Dyar, S. M.; Carmieli, R.; Malliakas, C. D.; Wasielewski, M. R.; Kanatzidis, M. G. Copolymerization of terephthalaldehyde with pyrrole, indole and carbazole gives microporous POFs functionalized with unpaired electrons. J. Mater. Chem. A 2013, 1, 10465-10473. (21) Lu, W.; Bosch, M.; Yuan, D.; Zhou, H.-C. Cost-Effective Synthesis of AmineTethered Porous Materials for Carbon Capture. ChemSusChem. 2015, 8, 433-438. (22) Cooper, A. I. Conjugated Microporous Polymers. Adv. Mater. 2009, 21, 1291-1295. (23) Jiang, J.-X.; Su, F.; Trewin, A.; Wood, C. D.; Campbell, N. L.; Niu, H.; Dickinson, C.; Ganin, A. Y.; Rosseinsky, M. J.; Khimyak, Y. Z.; Cooper, A. I. Conjugated Microporous Poly(aryleneethynylene) Networks. Angew. Chem., Int. Ed. 2007, 46, 8574-8578. (24) Bildirir, H.; Osken, I.; Ozturk, T.; Thomas, A. Reversible Doping of a Dithienothiophene-Based Conjugated Microporous Polymer. Chem. Eur. J. 2015, 21, 9306-9311. (25) Liu, X.; Li, H.; Zhang, Y.; Xu, B.; Xia, S. A, H.; Mu, Y. Enhanced carbon dioxide uptake by metalloporphyrinbased microporous covalent triazine framework. Polym. Chem. 2013, 4, 2445-2448.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(26) Wang, Z.; Yuan, S.; Mason, A.; Reprogle, B.; Liu, D-J.; Yu, L. Nanoporous

Porphyrin Polymers for Gas Storage and Separation. Macromolecules 2012, 45, 7413-7419. (27) Modak, A.; Nandi, M.; Mondal, J.; Bhaumik, A. Porphyrin based porous organic polymers: novel synthetic strategy and exceptionally high CO2 adsorption capacity. Chem. Commun. 2012, 48, 248-250. (28) Xiang, Z.; Zhou, X.; Zhou, C.; Zhong, S.; He, X.; Qin, C.; Cao, D. Covalent-organic polymers for carbon dioxide capture. J. Mater. Chem. 2012, 22, 22663-22669. (29) Liebl, M. R.; Senker, J. Microporous Functionalized Triazine-Based Polyimides with High CO2 Capture Capacity. Chem. Mater. 2013, 25, 970-980. (30) Zhu, X.; Tian, C.; Mahurin, S. M.; Chai, S.-H.; Wang, C.; Brown, S.; Veith, G. M.; Luo, H.; Liu, H.; Dai, S. A Superacid-Catalyzed Synthesis of Porous Membranes Based on Triazine Frameworks for CO2 Separation. J. Am. Chem. Soc. 2012, 134, 10478-10484. (31) Modak, A.; Pramanik, M.; Inagaki, S.; Bhaumik, A. A triazine functionalized porous organic polymer: excellent CO2 storage material and support for designing Pd nanocatalyst for C–C cross-coupling reactions. J. Mater. Chem. A 2014, 2, 1164211650. (32) Rabbani, M. G.; El-Kaderi, H. M. Synthesis and Characterization of Porous Benzimidazole-Linked Polymers and Their Performance in Small Gas Storage and Selective Uptake. Chem. Mater. 2012, 24, 1511-1517. (33) Rabbani, M. G.; Reich, T. E.; Kassab, R. M.; Jackson, K. T.; El-Kaderi, H. M. High CO2 uptake and selectivity by triptycene-derived benzimidazole-linked polymers. Chem. Commun. 2012, 48, 1141-1143.


Page 20 of 24

Page 21 of 24

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(34) Yu, H.; Tian, M.; Shen, C.; Wang, Z. Facile preparation of porous polybenzimidazole networks and adsorption behaviour of CO2 gas, organic and water vapors. Polym. Chem. 2013, 4, 961-968. (35) Jackson, K. T.; Rabbani, M. G.; Reich, T. E.; El-Kaderi, H. M. Synthesis of highly porous borazine-linked polymers and their application to H2, CO2, and CH4 storage. Polym. Chem. 2011, 2, 2775-2777. (36) Zhang, X.; Lu, J. Z.; Zhang, J. Porosity Enhancement of Carbazolic Porous Organic Frameworks Using Dendritic Building Blocks for Gas Storage and Separation. Chem. Mater. 2014, 26, 4023-4029. (37) Zhu, X.; Tian, C.; Jin, T.; Wang, J.; Mahurin, S. M.; Mei, W.; Xiong, Y.; Hu, J.; Feng, X.; Liu, H.; Dai, S. Thiazolothiazole-linked porous organic polymers. Chem. Commun. 2014, 50, 15055-15058. (38) Nandi, M.; Okada, K.; Dutta, A.; Bhaumik, A.; Maruyama, J.; Derks, D.; Uyama, H. Unprecedented CO2 uptake over highly porous N-doped activated carbon monoliths prepared by physical activation. Chem. Commun. 2012, 48, 10283-10285. (39) Li, P.; Xing, C.; Qu, S.; Li, B.; Shen, W. Carbon Dioxide Capturing by NitrogenDoping Microporous Carbon. ACS Sustainable Chem. Eng. 2015, 3, 1434-1442 (40) Pevida, C.; Drage, T. C.; Snape, C. E. Silica-templated melamine-formaldehyde resin derived adsorbents for CO2 capture. Carbon 2008, 46, 1464-1474. (41) Chaikittisilp, W.; Ariga, K.; Yamauchi, Y. A new family of carbon materials: synthesis of MOF derived nanoporous carbons and their promising applications. J. Mater. Chem. A 2013, 1, 14-19. (42) Merel, J.; Clausse, M.; Meunier, F. Experimental Investigation on CO2 PostCombustion Capture by Indirect Thermal Swing Adsorption Using 13X and 5A Zeolites. Ind. Eng. Chem. Res. 2008, 47, 209-215.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(43) Cavenati, S.; Grande, C. A.; Rodrigues, A. E. Adsorption Equilibrium of Methane, Carbon Dioxide, and Nitrogen on Zeolite 13X at High Pressures. J. Chem. Eng. Data 2004, 49, 1095-1101. (44) Shen, Y.; Wang, H.; Liu, J.; Zhang, Y. Enhanced Performance of a Novel Polyvinyl Amine/Chitosan/ Graphene Oxide Mixed Matrix Membrane for CO2 Capture. ACS Sustainable Chem. Eng. 2015, 3, 1819-1829. (45) Li, J.-R.; Kuppler, R. J.; Zhou, H.-C. Selective gas adsorption and separation in metalorganic frameworks. Chem. Soc. Rev. 2009, 38, 1477-1504. (46) Dawson, R.; Stockel, E.; Holst, J. R.; Adams, D. J.; Cooper, A. I. Microporous organic polymers for carbon dioxide capture. Energy Environ. Sci. 2011, 4, 4239-4245. (47) Saravanamurugan, S.; Kunov-Kruse, A. J.; Fehrmann, R.; Riisager, A. AmineFunctionalized Amino Acidbased Ionic Liquids as Efficient and High-Capacity Absorbents for CO2. ChemSusChem. 2014, 7, 897-902. (48) Schmidt, J.; Weber, J.; Epping, J. D.; Antonietti, M.; Thomas, A. Microporous Conjugated Poly(thienylene arylene) Networks. Adv. Mater. 2009, 21, 702-705. (49) Chen, Q.; Luo, M.; Hammershøj, P.; Zhou, D.; Han, Y.; Laursen, B. W.; Yan, C. G.; Han, B. H. Microporous Polycarbazole with High Specific Surface Area for Gas Storage and Separation. J. Am. Chem. Soc. 2012, 134, 6084-6087. (50) Zhu, X.; Mahurin, S. M.; An, S. H.; Do-Thanh, C. L.; Tian, C.; Li, Y.; Gill, L. W.; Hagaman, E. W.; Bian, Z.; Zhou, J. H.; Hu, J.; Liu, H.; Dai, S. Efficient CO2 capture by a task-specific porous organic polymer bifunctionalized with carbazole and triazine groups. Chem. Commun. 2014, 50, 7933-7936. (51) Luo, Y.; Li, B.; Wang, W.; Wu, K.; Tan, B. Hypercrosslinked Aromatic Heterocyclic Microporous Polymers: A New Class of Highly Selective CO2 Capturing Materials. Adv. Mater. 2012, 24, 5703-5707.


Page 22 of 24

Page 23 of 24

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(52) Rouquerol, J.; Avnir, D.; Fairbridge, C. W.; Everett, D. H.; Haynes, J. H.; Pernicone, N.; Ramsay, J. D. F.; Sing, K. S. W.; Unger, K. K. Recommendations for the characterization of porous solids. Pure Appl. Chem. 1994, 66, 1739-1758. (53) Roeser, J.; Kailasam, K.; Thomas, A. Covalent Triazine Frameworks as Heterogeneous Catalysts for the Synthesis of Cyclic and Linear Carbonates from Carbon Dioxide and Epoxides. ChemSusChem. 2012, 5, 1793-1799. (54) Minisci, F. Free-Radical Additions to Olefins in the Presence of Redox Systems. Acc. Chem. Res. 1975, 8, 165-171. (55) Holst, J. R.; Stöckel, E.; Adams, D. J.; Cooper, A. I. High Surface Area Networks from Tetrahedral Monomers: Metal-Catalyzed Coupling, Thermal Polymerization, and “Click” Chemistry. Macromolecules 2010, 43, 8531-8538. (56) Arab, P.; Rabbani, M. G.; Sekizkardes, A. K.; Đslamoğlu, T.; El-Kaderi, H. M. Copper(I)-Catalyzed Synthesis of Nanoporous Azo-Linked Polymers: Impact of Textural Properties on Gas Storage and Selective Carbon Dioxide Capture. Chem. Mater. 2014, 26, 1385-1392. (57) McCullough, R. D. The Chemistry of Conducting Polythiophenes. Adv. Mater. 1998, 10, 93-116. (58) Wu, F.; Chen, J.; Chen, R.; Wu, S.; Li, L.; Chen, S.; Zhao T. Sulfur/Polythiophene with a Core/Shell Structure: Synthesis and Electrochemical Properties of the Cathode for Rechargeable Lithium Batteries. J. Phys. Chem. C 2011, 115, 6057-6063. (59) Nandi, M.; Uyama, H. Exceptional CO2 Adsorbing Materials under Different Conditions. Chem. Record 2014, 14, 1134-1148.



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TABLE OF CONTENTS (TOC) GRAPHIC Novel Nitrogen and Sulfur Rich Hypercrosslinked Microporous Poly-TriazineThiophene Copolymer for Superior CO2 Capture Sudipta K. Kundu and Asim Bhaumik*

Novel hypercrossliked microporous copolymers bearing triazine and thiophene moieties have been synthesized and it showed CO2 uptake as high as 14.2 mmol g-1 at 273 K.


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Novel Nitrogen and Sulfur Rich Hyper-Cross ... - ACS Publications

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