Newly Designed Covalent Triazine Framework Based on Novel N

Dec 13, 2017 - Fourier transform infrared spectroscopy (FT-IR) measurements were carried out on a Thermo Nicolet 6700 FT-IR spectrometer using a KBr b...
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A newly designed covalent triazine framework based on novel Nheteroaromatic building block for efficient CO2 and H2 capture and storage Guangbo Wang, Karen Leus, Shuna Zhao, and Pascal Van Der Voort ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b16239 • Publication Date (Web): 13 Dec 2017 Downloaded from http://pubs.acs.org on December 14, 2017

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A newly designed covalent triazine framework based on novel Nheteroaromatic building block for efficient CO2 and H2 capture and storage

Guangbo Wang, Karen Leus, Shuna Zhao and Pascal Van Der Voort*

Center for Ordered Materials, Organometallics and Catalysis (COMOC), Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281 (S3), 9000 Ghent, Belgium.

KEYWORDS: Covalent Triazine Frameworks, N-heteroaromatic monomer, CO2 adsorption, H2 storage, CO2/N2 selectivity.

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ABSTRACT In this article, a set of novel covalent triazine frameworks were prepared by trimerization of 4,4',4'',4'''-(1,4-phenylenebis(pyridine-4,2,6-triyl))tetrabenzonitrile

in

molten

ZnCl2

under

ionothermal conditions. The influence of several parameters such as the ZnCl2/monomer ratio and reaction temperature on the structure and porosity of the resulting frameworks was systematically examined. After a thorough characterization, their performance in H2 and CO2 adsorption as well as their selectivity of CO2 over N2 was assessed. Notably, the CTF obtained using 20 molar equiv. of ZnCl2 at a reaction temperature of 400 ºC (CTF-20-400) exhibits an excellent CO2 adsorption capacity of 3.48 mmol/g at 1 bar and 273 K as well as a significantly high H2 uptake of 1.5 wt% at 1 bar and 77 K. These values belong to the top levels for all the CTFs measured under identical conditions to date. In addition, the obtained CTFs also present a relatively high CO2/N2 selectivity (up to 36 at 298 K) making them promising adsorbents for gas sorption and separation.

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INTRODUCTION Carbon dioxide, regarded as the main anthropogenic greenhouse gas, is widely accepted to be the primary contributor to global warming. Until now, the most established and applicable technique for CO2 capture is the chemical absorption of CO2 by aqueous amine solutions, also called “wet scrubbing”,1 however, it processes some inherent drawbacks including equipment corrosion, high energy consumption as well as regeneration difficulties.2 As a result, the development of alternative and more effective technologies or strategies for capturing or eliminating the produced CO2 levels from various industrial processes remains an urgent and challenging task. Lately, a new class of designable and robust porous organic polymers (POPs), such as metal organic frameworks (MOFs) or covalent organic frameworks (COFs), has shown plausible promise for this issue.3-6 Among them, covalent triazine frameworks (CTFs), a nitrogen-rich subclass of POPs, are nowadays intensively investigated to address this challenge due to their remarkable low framework density, large surface area, good thermal and chemical stability and the rational tunability of such networks.7-12 In addition, CTFs have been used in many other applications including heterogeneous catalysis13 and adsorption of organic dyes in liquid phase.14 Because of the strong electrostatic interactions between the accessible nitrogen sites and the carbon atoms of the CO2 molecules, theoretical calculations have demonstrated the introduction of nitrogen-rich groups, e.g. pyridine, pyridazine and triazine onto/into the structure walls of certain porous materials is able to significantly improve their CO2 adsorption capacity and selectivity as well as enhanced storage capacity of clean energy sources, such as H2.15 For example, El-Kaderi et. al. reported on a set of nitrogen-rich POPs, exhibiting high CO2 adsorption capacities as well as remarkable CO2/N2 and CO2/CH4 selectivities.16-18 In another

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study, a nitrogen-rich hexacarboxylate ligand was employed to synthesize a (3,24)-connected rth-type topology of MOF (NTU-105), which exhibits exceptionally high CO2 (36.7 wt% at 1 bar and 273 K) and H2 (2.75 wt% at 1 bar and 77 K) adsorption capacities.19 Lotsch and co-authors reported on a set of covalent triazine frameworks having a high nitrogen content for selective gas adsorption and separation, of which a bipyridine-CTF synthesized at 600 ºC (bipy-CTF600) exhibits superior CO2 (5.58 mmol/g at 273 K and 1 bar) and H2 uptakes (2.12 wt% at 77 K and 1 bar) and extremely high CO2 selectivities over N2.9 With this knowledge in mind, we present in this study the use of a novel heteroaromatic tetranitrile, 4,4',4'',4'''-(1,4-phenylenebis(pyridine4,2,6-triyl))tetrabenzonitrile, to design and synthesize a set of nitrogen-rich porous CTFs by varying the ZnCl2/monomer ratio and synthesis temperature. The influence of several parameters such as the ZnCl2/monomer ratio and reaction temperature on the structure and porosity of the resulting frameworks was systematically examined. After a thorough characterization, the obtained CTFs were explored for their CO2 and H2 adsorption properties. In addition, their selectivity of CO2 over N2 was also assessed for potential gas separation applications. EXPERIMENTAL SECTION Materials and analytical techniques. All the chemicals were bought from Sigma Aldrich or TCI Europe and used as such without further purifications. Powder-X-ray diffraction (XRPD) patterns were recorded on a Thermo Scientific ARL X’Tra diffractometer (Cu-Kα radiation (λ = 1.5406 Å) at 40 kV and 30 mA). Fourier Transform Infrared Spectroscopy (FT-IR) measurements were carried out on a Thermo Nicolet 6700 FT-IR spectrometer using a KBr beam splitter and a MCT detector. Elemental analysis were obtained using a Thermo Scientific Flash 2000 CHNS-O analyzer. Thermogravimetric analysis (TGA) curves were recorded under an air flow with a heating rate of 10°C/min in the range of 25-800 °C on a Netzsch STA-449 F3

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Jupiter-simultaneous TG-DSC analyzer. The Scanning Electron Microscopy (SEM) images of the CTFs materials were recorded on a JEOL JSM 7600F FEG. SEM. A Belsorp Mini instrument was employed to obtain the N2 adsorption isotherms at 77 K, whereas for the CO2 and H2 isotherms, an iSorb-HP gas sorption analyzer (Quantachrome) was used. All the materials were dried at 150 ºC under vacuum for 3 h before the gas adsorption measurements were performed. Synthesis

of

CTFs.

The

monomer,

4,4',4'',4'''-(1,4-phenylenebis(pyridine-4,2,6-

triyl))tetrabenzonitrile, was synthesized following the procedure reported by Zhang et al .20 In a typical CTF material synthesis, the ampoule was charged with the monomer (318 mg, 0.5 mmol) and various amounts of anhydrous ZnCl2 (ranging from 340 mg, 2.5 mmol to 1360 mg, 10 mmol) in the glovebox (See the experimental details in Table S1, Electronic Supplementary Information). Hereafter, the ampoule was evacuated, flame-sealed and slowly heated to the desired temperatures (400 ºC or 500 ºC) with the heating step of 1 ºC/min for 48 h. Hereafter, at room temperature, the ampoule was opened and the crude material was grounded and stirred in water for 6 h, filtrated and washed thoroughly with distillated water. Afterwards, the obtained black solid was stirred in HCl (1M) overnight, followed by successive washing with water, THF and acetone. Hereafter, the resulting CTF materials was activated at 150 ºC under vacuum overnight prior to further analysis. RESULTS AND DISCUSSION Synthesis and characterization of CTFs Generally, CTF materials can be prepared under ionothermal conditions using molten ZnCl2 both as the Lewis acidic trimerization catalyst and reaction medium7 or under strong Brønsted acid (CF3SO3H) conditions21. A systematic comparison of both methods on the resulting gas sorption

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properties was reported by Janiak et al.22 In this study, we only employed the typical ionothermal route to prepare the CTFs. As previous reports already demonstrated, the ZnCl2/monomer ratio as well as the synthesis temperature have great influence on the structural and porous characteristics of such networks.23-24 Therefore, in the present study, we followed the typical ionothermal procedure using 4,4',4'',4'''-(1,4-phenylenebis(pyridine-4,2,6-triyl))tetrabenzonitrile as the monomer to produce a series of CTFs by varying the reaction temperature and the amount of employed ZnCl2 (Scheme 1). The obtained CTFs are denoted as, CTF-mol equiv. ZnCl2temperature, in the following (e.g. CTF-5-400 is prepared with 5 mol equiv. ZnCl2 at 400 ºC).

Scheme 1. Illustration of the idealized building units of the CTF materials discussed in this work. The crystallinity of all the synthesized materials was checked by powder X-ray diffraction analysis (Figure S1). As expected, all the CTF materials are amorphous. A broad peak appeared at 2θ = 24º for the materials prepared at 500 ºC, indicating a generally amorphous structure with some graphitic two-dimensional layers.25 The successful trimerization reaction was confirmed by FT-IR measurements (Figure 1). For the CTF-5-400 and CTF-10-400, the characteristic band of

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cyano group at 2230 cm-1 can be clearly observed, showing an incomplete trimerization. This might be attributed to the high mass of the monomer and the employed amount of ZnCl2 is not sufficiently enough to completely dissolve the starting monomer and the formed oligomers. In contrast, when 20 mol equiv. ZnCl2 was used or the reaction temperature was increased to 500 ºC, the band for cyano group at 2230 cm-1 completely disappeared, showing that the trimerization is complete. At a synthesis temperature of 400 ºC, the typical bands for triazine rings at 1548 cm-1 and 1360 cm-1 are clearly visible, while at a higher reaction temperature (500 ºC) these vibrations are rather featureless, which might be attributed to the partial carbonization of the materials.9, 26

Figure 1. FT-IR spectra of the monomer and all the obtained CTFs discussed in this work. Elemental analysis results indicate a relatively lower nitrogen content in comparison to the theoretically expected values for all the obtained CTFs. Additionally, a significantly enhanced C/N ratio was observed when the reaction temperature and the amount of the employed ZnCl2

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was increased (Table S2), which can be attributed to the higher nitriles cleavages in the structure and to the triazine rings decomposition during the trimerization process at higher reaction temperature, which is in accordance with previous studies.8-9, 24-25 It should be noted that the total amount of elements (C, H, N) determined by element analysis is always lower than 100%, the deviation might be due to the trapped metal salts and water in the pores, which could not be removed completely.27-28 The SEM images, presented in Figure S2, showed that all the CTFs display the general morphology of aggregates of irregular lump having different sizes. The thermal stability of the obtained CTFs was confirmed by TGA analysis under air atmosphere (Figure S3). For the samples synthesized at 400 ºC, the framework starts to decompose at around 440 ºC, while the CTFs prepared at a higher temperature are stable up to 500 ºC, demonstrating their high thermal stability. Gas sorption properties. The permanent porosity properties of all the obtained CTFs were studied by N2 sorption measurements at 77 K (Figure 2). All the studied samples were activated at 150 ºC for 3 hours under vacuum prior to the measurements. As can be seen from Figure 2, the isotherms of all the CTFs are in fact a typical type I isotherm at low relative pressure combined with a type II isotherm at high relative pressure.11 Generally, all the CTFs show a steep increase of N2 uptake in the low P/P0 region, indicating the microporous character of the materials and the existence of a slight hysteresis loop of the isotherms suggests the presence of mesopores. More specifically, with the increase of the reaction temperature and the amount of ZnCl2, the Brunauer-EmmettTeller (BET) surface area and pore volume of the CTF materials increased from 802 m2/g and 0.48 cm3/g for CTF-5-400 to 1563 m2/g and 0.94 cm3/g for CTF-20-500, respectively. The higher porosity of the latter samples might be assigned to the presence of extra defects in the

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structure, created at higher temperatures or when more ZnCl2 is used.26, 29 The detailed porosity parameters for all the studied CTF materials are presented in Table 1.

Figure 2. N2 adsorption (closed symbols) and desorption (open symbols) isotherms of all the studied CTF materials measured at 77 K.

Table 1. BET surface areas, pore volumes, CO2 and H2 adsorption uptakes, CO2 adsorption of isosteric heat (Qst) and CO2/N2 selectivities of the presented CTFs SBET(a)

Vmicro(b)

Vtot(c)

(m2/g)

(cm3/g)

(cm3/g)

Vmicr o/Vtot

CTF-5-400

802

0.37

0.48

CTF-10-400

1033

0.50

CTF-20-400

1458

CTF-5-500

Sample

CO2 uptake (mmol/g)

H2 uptake (wt%)

Qst for CO2

CO2/N2(d)

(kJ/mol)

Selectivity

273 K

298 K

0.77

2.25

1.51

0.98

26

24

0.59

0.85

2.90

1.68

1.21

28

14

0.73

0.84

0.87

3.48

2.09

1.50

22

19

853

0.34

0.47

0.72

3.02

1.91

1.13

26

36

CTF-10-500

1251

0.7

0.78

0.9

3.20

1.90

1.34

26

18

CTF-20-500

1563

0.82

0.94

0.87

3.21

1.92

1.48

25

20

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(a)

BET surface area was calculated over the relative pressure range of 0.01-0.05 at 77 K; (b) Vmicro, micropore volume was calculated by N2 adsorption isotherm using t-plot method; (c) V tot, total pore volume was calculated at P/P0 = 0.98; (d) The selectivity was calculated by Henry Model

The unique N-heteroatom framework, the high surface area as well as the microporous nature of the studied CTF materials prompted us to further explore their gas sorption properties at atmospheric pressure. To this aim, CO2 adsorption isotherms were recorded at 273 K and 298 K (Figure 3 and Figure S4-S5). As shown in Figure 3, when using the same equiv. of ZnCl2, increasing the synthesis temperature from 400 ºC to 500 ºC results in the materials exhibiting a higher CO2 uptake, while at the same synthesis temperature (400 ºC), applying more equiv. of ZnCl2 results in CTFs having a higher CO2 adsorption capacity. Nevertheless, when the synthesis temperature is 500 ºC, the amount of employed ZnCl2 has little effect on the material’s CO2 adsorption capacity as the CO2 uptake is almost the same for all the samples obtained at 500 ºC. Among all the obtained CTFs, CTF-20-400 exhibits the highest CO2 adsorption uptake of 3.48 and 2.09 mmol/g at 273 K and 298 K, respectively. The CO2 uptake of CTF-20-400 is much higher in comparison to numerous CTFs measured at 273 K such as CTF-1 (2.47 mmol/g)30, CTF-DCN-500 (2.7 mmol/g)26, PCTF-1 to 3 (2.02-3 mmol/g)31 and CTF-0 (1.54-2.34 mmol/g)29.

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Figure 3. CO2 adsorption (closed symbols) and desorption (open symbols) isotherms of the studied CTF materials measured up to 1 bar at 273 K. The isosteric heat of CO2 adsorption (Qst) is considered as a rough estimate of the interaction energies. Thus, to get a better insight in the CO2 adsorption of the CTF materials, we calculated the Qst for all the CTFs by employing the Clausius-Clapeyron equation to fit the CO2 adsorption isotherms at 273 K and 298 K and plotted the Qst as a function of the adsorbed CO2 uptake (Figure S6). At low CO2 coverage, the Qst values are calculated to be 22-28 kJ/mol for the CTFs, which is much higher than the heat of liquefaction of bulk CO2 (17 kJ/mol)32 and similar to the isosteric heat of CO2 adsorption on activated carbon.33 These results indicate relatively strong interactions between CO2 molecules and the network, explaining the overall high CO2 uptakes of the CTFs. Moreover, the incorporation of nitrogen sites into CTFs not only afforded significant CO2 uptakes but also resulted in more preferential CO2 adsorption over N2, i.e., higher CO2/N2 selectivity, another crucial factor for realistic carbon capture. Thus we further calculated the CO2/N2 selectivity at 298 K of all the studied CTFs using the Henry model based on the CO2 and N2 adsorption isotherms (Figure S7 and S8) and the detailed values are listed in Table 1. The

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highest CO2/N2 selectivity was observed for CTF-5-500 (36 at 298 K), which is in line with the fact that smaller pores are favorable for N2 adsorption. As a potential renewable and clean alternative to current fossil fuels, hydrogen storage remains the major obstacle for its widespread applications and the development of safe and efficient ways of H2 storage remains urgent and challengeable. Recently, adsorptive hydrogen storage in MOFs and COFs has been explored as a plausible approach for hydrogen storage.34-35 Thus, we further carried out H2 adsorption measurements on all the obtained CTFs up to 1 bar at 77 K (Figure 4 and Figure S9-S10). In contrast to CO2 adsorption, H2 uptakes mainly depend on the materials’ surface area and the H2 adsorption capacities varied from 0.98 to 1.5 wt % (Table 1). The highest H2 adsorption capacity was found for CTF-20-400 (1.5 wt%), this value is comparable to that reported for DCBP-CTF (1.55 wt%)7 and is only slightly lower than PCTF-1 (1.86 wt%)36 and fl-CTF-400 (1.95 wt%)37.

Figure 4. H2 adsorption (closed symbols) and desorption (open symbols) isotherms for CTF-20400 and CTF-20-500 measured at 77 K.

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CONCLUSION In this study, we have employed a new monomer to obtain a set of highly microporous and nitrogen-rich CTFs as high-performance platforms for gas sorption and storage. The effect of several synthesis parameters including the reaction temperature and molar ratios of ZnCl2 on the structure and porosity properties of such networks was comprehensively studied. Notably, the microporosity together with the rich CO2-philic N sites results in the framework with excellent CO2 (3.48 mmol/g, at 273 K and 1 bar) and H2 (1.5 wt%, 77 K and 1 bar) uptakes. These values are among the top levels for all the reported CTFs measured under identical conditions. In addition, the obtained CTFs also exhibit relatively high CO2/N2 selectivities (up to 36) as calculated by Henry Model at 298 K. These properties together with their good thermal and chemical stability render the studied CTFs promising candidates as prospective carbon capture and hydrogen storage materials. ASSOCIATED CONTENT Supporting Information. The Supporting Information is available free of charge via the Internet at DOI: XXX. Table for the detailed amount of the chemicals used for the synthesis, Elemental Analysis results, XRD patterns of the CTFs, TGA results, SEM images, CO2 adsorption isotherms, isosteric heat of CO2 adsorption (Qst) and H2 adsorption isotherms. AUTHOR INFORMATION Corresponding Author * E-mail address: [email protected] Author Contributions

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The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Conflict of Interest There are no conflicts to declare. ACKNOWLEDGEMENT G.-B. W. thanks the China Scholarship Council (CSC) and UGENT BOF grant for PhD Funding. K. L. thanks the financial support from Ghent University. S.-N. Z. acknowledges the postdoctoral

scholarship

of

the

Ghent

University

Special

Research

Fund

(BOF.PDO.2016.0030.01). REFERENCE (1) Rochelle, G. T. Amine Scrubbing for CO2 Capture. Science 2009, 325 (5948), 1652-1654. (2) Wang, Q.; Luo, J.; Zhong, Z.; Borgna, A. CO2 capture by solid adsorbents and their applications: current status and new trends. Energy Environ. Sci. 2011, 4 (1), 42-55. (3) Zhang, Z. J.; Yao, Z. Z.; Xiang, S. C.; Chen, B. L., Perspective of microporous metal-organic frameworks for CO2 capture and separation. Energy Environ. Sci., 2014,7, 2868-2899. (4) Olajire, A. A. Recent advances in the synthesis of covalent organic frameworks for CO2 capture. J. CO2 Util. 2017, 17, 137-161. (5) Trickett, C. A.; Helal, A.; Al-Maythalony, B. A.; Yamani, Z. H.; Cordova, K. E.; Yaghi, O. M. The chemistry of metal–organic frameworks for CO2 capture, regeneration and conversion. Nat. Rev. Mater. 2017, 2, 17045. (6) Yu, J.; Xie, L.-H.; Li, J.-R.; Ma, Y.; Seminario, J. M.; Balbuena, P. B. CO2 Capture and Separations Using MOFs: Computational and Experimental Studies. Chem. Rev. 2017 117 (14), 9674–9754. (7) Kuhn, P.; Antonietti, M.; Thomas, A. Porous, Covalent Triazine-Based Frameworks Prepared by Ionothermal Synthesis. Angew. Chem. Int. Ed. 2008, 47 (18), 3450-3453.

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(8) Hug, S.; Tauchert, M. E.; Li, S.; Pachmayr, U. E.; Lotsch, B. V. A functional triazine framework based on N-heterocyclic building blocks. J. Mater. Chem. 2012, 22 (28), 1395613964. (9) Hug, S.; Stegbauer, L.; Oh, H.; Hirscher, M.; Lotsch, B. V. Nitrogen-Rich Covalent Triazine Frameworks as High-Performance Platforms for Selective Carbon Capture and Storage. Chem. Mater. 2015, 27 (23), 8001-8010. (10) Tao, L.; Niu, F.; Wang, C.; Liu, J.; Wang, T.; Wang, Q. Benzimidazole functionalized covalent triazine frameworks for CO2 capture. J. Mater. Chem. A 2016, 4 (30), 11812-11820. (11) Dey, S.; Bhunia, A.; Breitzke, H.; Groszewicz, P. B.; Buntkowsky, G.; Janiak, C. Two linkers are better than one: enhancing CO2 capture and separation with porous covalent triazinebased frameworks from mixed nitrile linkers. J. Mater. Chem. A 2017, 5 (7), 3609-3620. (12) Tuci, G.; Pilaski, M.; Ba, H.; Rossin, A.; Luconi, L.; Caporali, S.; Pham-Huu, C.; Palkovits, R.; Giambastiani, G. Unraveling Surface Basicity and Bulk Morphology Relationship on Covalent Triazine Frameworks with Unique Catalytic and Gas Adsorption Properties. Adv. Funct. Mater. 2017, 27 (7), 1605672-n/a. (13) Bhunia, A.; Esquivel, D.; Dey, S.; Fernandez-Teran, R.; Goto, Y.; Inagaki, S.; Van Der Voort, P.; Janiak, C. A photoluminescent covalent triazine framework: CO2 adsorption, lightdriven hydrogen evolution and sensing of nitroaromatics. J. Mater. Chem. A 2016, 4 (35), 1345013457. (14) Bhunia, A.; Dey, S.; Bous, M.; Zhang, C.; von Rybinski, W.; Janiak, C. High adsorptive properties of covalent triazine-based frameworks (CTFs) for surfactants from aqueous solution. Chem. Commun. 2015, 51 (3), 484-486. (15) Vogiatzis, K. D.; Mavrandonakis, A.; Klopper, W.; Froudakis, G. E. Ab initio Study of the Interactions between CO2 and N-Containing Organic Heterocycles. ChemPhysChem 2009, 10 (2), 374-383. (16) Rabbani, M. G.; El-Kaderi, H. M. Synthesis and Characterization of Porous BenzimidazoleLinked Polymers and Their Performance in Small Gas Storage and Selective Uptake. Chem. Mater. 2012, 24 (8), 1511-1517. (17) 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 (8), 1141-1143.

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(18) Rabbani, M. G.; Islamoglu, T.; El-Kaderi, H. M. Benzothiazole- and benzoxazole-linked porous polymers for carbon dioxide storage and separation. J. Mater. Chem. A 2017, 5 (1), 258265. (19) Wang, X.-J.; Li, P.-Z.; Chen, Y.; Zhang, Q.; Zhang, H.; Chan, X. X.; Ganguly, R.; Li, Y.; Jiang, J.; Zhao, Y. A Rationally Designed Nitrogen-Rich Metal-Organic Framework and Its Exceptionally High CO2 and H2 Uptake Capability. Sci. Rep. 2013, 3, 1149. (20) Wang, J.-H.; Zhang, Y.; Li, M.; Yan, S.; Li, D.; Zhang, X.-M. Solvent-Assisted Metal Metathesis: A Highly Efficient and Versatile Route towards Synthetically Demanding Chromium Metal–Organic Frameworks. Angew. Chem. Int. Ed. 2017, 56 (23), 6478-6482. (21) Ren, S.; Bojdys, M. J.; Dawson, R.; Laybourn, A.; Khimyak, Y. Z.; Adams, D. J.; Cooper, A. I. Porous, Fluorescent, Covalent Triazine-Based Frameworks Via Room-Temperature and Microwave-Assisted Synthesis. Adv. Mater. 2012, 24 (17), 2357-2361. (22) Bhunia, A.; Boldog, I.; Moller, A.; Janiak, C. Highly stable nanoporous covalent triazinebased frameworks with an adamantane core for carbon dioxide sorption and separation. J. Mater. Chem. A 2013, 1 (47), 14990-14999. (23) Kuhn, P.; Thomas, A.; Antonietti, M. Toward Tailorable Porous Organic Polymer Networks: A High-Temperature Dynamic Polymerization Scheme Based on Aromatic Nitriles. Macromolecules 2009, 42 (1), 319-326. (24) Kuhn, P.; Forget, A.; Su, D.; Thomas, A.; Antonietti, M. From Microporous Regular Frameworks to Mesoporous Materials with Ultrahigh Surface Area: Dynamic Reorganization of Porous Polymer Networks. J. Am. Chem. Soc. 2008, 130 (40), 13333-13337. (25) Park, K.; Lee, K.; Kim, H.; Ganesan, V.; Cho, K.; Jeong, S. K.; Yoon, S. Preparation of covalent triazine frameworks with imidazolium cations embedded in basic sites and their application for CO2 capture. J. Mater. Chem. A 2017, 5 (18), 8576-8582. (26) Wang, K.; Huang, H.; Liu, D.; Wang, C.; Li, J.; Zhong, C. Covalent Triazine-Based Frameworks with Ultramicropores and High Nitrogen Contents for Highly Selective CO2 Capture. Environ. Sci. Technol. 2016, 50 (9), 4869-4876. (27) Dey, S.; Bhunia, A.; Boldog, I.; Janiak, C. A mixed-linker approach towards improving covalent triazine-based frameworks for CO2 capture and separation. Microporous Mesoporous Mater. 2017, 241, 303-315. (28) Dey, S.; Bhunia, A.; Esquivel, D.; Janiak, C. Covalent triazine-based frameworks (CTFs)

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from triptycene and fluorene motifs for CO2 adsorption. J. Mater. Chem. A 2016, 4 (17), 62596263. (29) Katekomol, P.; Roeser, J.; Bojdys, M.; Weber, J.; Thomas, A. Covalent Triazine Frameworks Prepared from 1,3,5-Tricyanobenzene. Chem. Mater. 2013, 25 (9), 1542-1548. (30) Zhao, Y.; Yao, K. X.; Teng, B.; Zhang, T.; Han, Y. A perfluorinated covalent triazine-based framework for highly selective and water-tolerant CO2 capture. Energy Environ. Sci. 2013, 6 (12), 3684-3692. (31) Gu, C.; Liu, D.; Huang, W.; Liu, J.; Yang, R. Synthesis of covalent triazine-based frameworks with high CO2 adsorption and selectivity. Polym. Chem. 2015, 6 (42), 7410-7417. (32) Keskin, S.; van Heest, T. M.; Sholl, D. S. Can Metal–Organic Framework Materials Play a Useful Role in Large-Scale Carbon Dioxide Separations? ChemSusChem 2010, 3 (8), 879-891,. (33) Himeno, S.; Komatsu, T.; Fujita, S. High-Pressure Adsorption Equilibria of Methane and Carbon Dioxide on Several Activated Carbons. Journal of Chemical & Engineering Data 2005, 50 (2), 369-376. (34) Sculley, J.; Yuan, D.; Zhou, H.-C. The current status of hydrogen storage in metal-organic frameworks-updated. Energy Environ. Sci. 2011, 4 (8), 2721-2735. (35) Schlapbach, L.; Zuttel, A. Hydrogen-storage materials for mobile applications. Nature 2001, 414 (6861), 353-358. (36) Bhunia, A.; Vasylyeva, V.; Janiak, C. From a supramolecular tetranitrile to a porous covalent triazine-based framework with high gas uptake capacities. Chem. Commun. 2013, 49 (38), 39613963. (37) Hug, S.; Mesch, M. B.; Oh, H.; Popp, N.; Hirscher, M.; Senker, J.; Lotsch, B. V. A fluorene based covalent triazine framework with high CO2 and H2 capture and storage capacities. J. Mater. Chem. A 2014, 2 (16), 5928-5936.

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A novel nitrogen-rich covalent triazine framework showing significantly high CO2 and H2 adsorption capacities were rational designed and synthesized. 309x343mm (96 x 96 DPI)

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