Synthesis, Carbonization, and CO2 Adsorption Properties of

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Synthesis, carbonization, and CO2 adsorption properties of phloroglucinol-melamine-formaldehyde polymeric nanofibers Qiang Xiao, Junjun Wen, Yanna Guo, Jing-xiu Hu, Jin-Gui Wang, Fumin Zhang, Gaomei Tu, Yijun Zhong, and Wei-Dong Zhu Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.6b03494 • Publication Date (Web): 21 Nov 2016 Downloaded from http://pubs.acs.org on November 22, 2016

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Industrial & Engineering Chemistry Research

Synthesis, carbonization, and CO2 adsorption properties of phloroglucinol-melamine-formaldehyde polymeric nanofibers

Qiang Xiao,* † Junjun Wen, † Yanna Guo, † Jingxiu Hu, † Jingui Wang, ‡ Fumin Zhang, † Gaomei Tu, † Yijun Zhong, † and Weidong Zhu†

† Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Institute of Physical Chemistry, Zhejiang Normal University, Jinhua, 321004, P.R. China. E-mail: [email protected]; Tel/Fax: +86-579-82282234 ‡ Shandong Provincial Key Laboratory of Fine Chemicals, School of Chemistry and Pharmaceutical Engineering, Qilu University of Technology, Jinan, 250353, P.R. China.

Corresponding author * Tel/Fax: +86-579-82282234. E-mail: [email protected].

ACS Paragon Plus Environment


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ABSTRACT Amine-rich polymeric nanofibers were hydrothermally synthesized by a simple

polycondensation

formaldehyde

as

method starting

using

melamine,

materials.

phloroglucinol The

and

synthesized

phloroglucinol-melamine-formaldehyde (PMF) polymeric nanofibers were characterized by various techniques, such as scanning electron microscope (SEM), transmission electron microscope (TEM), N2 adsorption-desorption, Fourier transform infrared (FT-IR) spectroscopy and

13

C nuclear magnetic

resonance (NMR) etc. Pure CO2 gas adsorption on the as-prepared PMF nanofibers was investigated by the volumetric method. Breakthrough column experiments showed that CO2-N2 or CO2-CH4 mixtures could be separated on the PMF nanofibers. Additionally, the PMF polymeric fibers were carbonized, leading to nitrogen-rich carbon nanofibers (NCF), which exhibited an improved CO2 adsorption capacity.

Keywords: CO2 adsorbents, polymeric nanofiber, melamine, carbon nanofibers, porous resin


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Introduction Carbon dioxide capture and sequestration (CCS), i.e. snatching of CO2 and storing it, has been one of the effective way to reduce CO2 emissions since fossil fuels are currently the major energy sources.1,2 Now CO2 has also found other outlet as carbonous resources for the synthesis organic products, besides the approach of injecting into deep well.3 Currently, amine solution scrubbing is the dominant technique to capture CO2.4,5 Nevertheless, it has some inherent shortcomings, e.g. corrosion to equipment, highly energy-consuming and ease to decomposition during regeneration.6 Adsorption by using solid adsorbents is a conventional separation technology. Solid adsorbents such as activated carbon,7 zeolites8, mesoporous silica9, metal organic frameworks (MOFs)10, and covalent organic frameworks (COFs)11,12 are intensively investigated as CO2 adsorbents. However, some problems such as low adsorption capacity, low selectivity, poor stability and moisture sensitivity when they are used in CCS.13 Among the numerous work reported on the CO2 adsorbents, an effective strategy is to introduce amino groups with good CO2 affinity into porous networks, leading to greatly improved CO2 capacity and selectivity.14-20 Recently, melamine, with very high amine density (67% nitrogen by mass), was used as building blocks to construct microporous organic polymers (MOP) via the Schiff base chemistry.21,22 The melamine-based microporous organic polymers (MBMOP), possessing abundant microporosity and plenty of amine



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groups, exhibit high CO2 adsorption capacity, good CO2 selectivity and easy regeneration.23 However, the synthesis is performed refluxing in DMSO solvent at 453 K and inert atmosphere. The harsh synthesis conditions bring forth some severe problems, e.g. odorous smell and poor reproducibility, resulting in the gloomy prospect of the application in CO2 adsorption. Actually, melamine resins, formed by crosslinking of melamine and formaldehyde, are one of the most common commercial synthetic polymers. Unfortunately, the traditional melamine resins are nonporous, resulting in the inaccessibility of amine groups embedded in the melamine resins. Pevida et al. have synthesized a range of melamine-formaldehyde highly porous adsorbents using silica as template material and carbonization at different temperatures to produce highly porous nitrogen enriched carbons.24 Recently, Long’s group has reported a series of melamine based polymeric microspheres with an extended network using melamine, resorcinol and formaldehyde as precursors.25 Melamine and resorcinol, as rigid building blocks, produce rigidity within the formed network, leading to the formation of micropores. In other words, the crosslinking network of resorcinol and formaldehyde provides backbone to disperse amine groups in micropores, making them be available for CO2 adsorption.26 Herein we adopt phloroglucinol, which has three phenol reactive sites binding with formaldehyde molecules, as rigid building blocks to fabricate phloroglucinol-melamine-formaldehyde (PMF) polymeric networks in aqueous


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solution. Polymeric nanofibers were obtained from the simple hydrothermal system, as shown in Scheme 1. The adsorption of CO2 on the as-obtained PMF nanofibers was evaluated. Carbonization is a good approach to improve the porosity of melamine-based porous polymer and the resulted nitrogen containing carbonous materials show improved CO2 capture properties.27-30 One of the PMF samples was carbonized at elevated temperatures, producing nitrogen-rich carbon nanofibers. Benefit from the improved porosity, the nitrogen-rich carbon nanofibers carbonized at 1073 K show an enhanced CO2 adsorption capacity. The synthetic approach provides an alternative facile route for the preparation of polymeric nanofibers and carbon nanofibers, besides melt processing, interfacial polymerization, electrospinning, antisolvent-induced polymer precipitation, etc.31

Experimental section Materials Melamine (A.R., 99%)，phloroglucinol (HPLC, ≥99%)，formaldehyde solution, (A.R., 37%）were purchased from Aladdin Reagent Co., Ltd and used as received. Synthesis In a typical synthesis, 4.41 g phloroglucinol (35 mmol) and 40 ml deionized (DI) water were mixed in a 100 ml flask. After stirring at 313 K for 30 min, 8.52 g formaldehyde solution (105 mmol) was added to the above mixture



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followed by stirring for 100 min. The above mixture was referred to as A. Mixture B was prepared by mixing 4.41 g melamine (35 mmol), 40 ml DI water, and 8.52 g formaldehyde solution (105 mmol) at 343 K. Then the mixture B was added to the mixture A and stirred. The whole mixture was sealed into a 250 ml capped glass bottle and heated at 368 K for 24 h. The product was recovered by filtration, washed with DI water, and dried at 333 K overnight to get the final product in powder form. The synthesis compositions and corresponding sample codes are summarized in Table 1. Carbonization The PMF-1 sample was tiled in a quartz container. Then the sample was heated to 973 K, 1073 K or 1173 K at a heating ramp of 5 K min-1 in N2 flow and kept for 2 h. After cooled to room temperature in N2 flow, the obtained carbonized product was referred to as PMF-1-700, PMF-1-800, and PMF-1-900 for carbonization at 973 K, 1073 K, and 1173 K, respectively. Characterization Scanning electron microscope (SEM) images were obtained using a HITACHI S-4800 microscope equipped with a field emission gun. The acceleration voltage was set to 5 kV. The samples were stuck on the observation platform and sprayed with gold vapor under high vacuum for about 20 s. Transmission electron microscopy (TEM) observations were carried out on a 2100 JEOL TEM working at 200 kV. The sample was diluted in ethanol to give a 1:5 volume ratio, and sonicated for 10 min. The ethanol slurry was then


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dripped onto a Cu grid covered with a holey film of carbon. Fourier transform infrared (FT-IR) spectra were recorded on a Nicole Nexus 670 spectrometer with a resolution of 4 cm-1. N2 adsorptions were measured at 77 K using a Quantachrome Autosorb-1 analyzer. Prior to the measurements, the samples were outgassed in vacuum at 393 K for 8 h. The specific surface area was calculated by the BET (Brunauer-Emmett-Teller) method. The micropore surface area and volume were determined using the t-plot method. Thermogravity differential thermal analysis curve (TG-DTA) was obtained on a thermogravimetric analyzer (NETZSCH STA449) in a N2 flow with a heating ramp of 5 K min-1. The solid-state nuclear magnetic resonance (NMR) experiments were carried out at B0 = 9.4 T on a Bruker AVANCE III 400 WB spectrometer with a H-X BL4 double-resonance probe. The corresponding resonance frequency of

13

C was 100.6 MHz. Samples were packed in a 4 mm

ZrO2 rotor and spun at the magic angle (54.7o). The

13

C chemical shift was

externally referenced to the high field resonance of hexamethylbenzene at 17.35 ppm. CO2 gas adsorption CO2 adsorption measurements were performed on a Micromeritics ASAP 2020. The sample cell was loaded with ca. 250 mg sorbent. After the adsorbent was outgassed in vacuum at 393K for 12 h, the adsorption run was carried out using high purity CO2 (99.999%) in a pressure range from 0.01 to 118 kPa.



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High pressure CO2 adsorption measurements were carried out at 298 K on a Micromeritics HPVA-100 analyzer with a pressure range from 0.01 to 10 bar. Breakthrough column experiments The breakthrough column experiments were carried out in a homemade apparatus equipped with a stainless steel tube with an inner diameter of 4.65 mm and a length of 10 cm.23 Prior to the experiments, the adsorbent was purged by a He flow (20 ml min-1) at 423 K for 12 h. Breakthrough separation experiments

were

conducted

by

flowing

He−CO2−N2

mixtures

or

He−CO2−CH4 mixtures with a total flow rate of 8 ml min-1 at 298 K. Different gas composition was obtained by altering the gas flow rate controlled by mass flow controllers. The He flow rate is always setting at 4 ml min-1. Blank experiments were carried out using silica (20−40 mesh) with the same volume under the same conditions.

Results and discussion

Phloroglucinol-Melamine-Formaldehyde (PMF) polymer fibers

The products obtained through polycondensation of phloroglucinol, melamine, and formaldehyde exhibit a form of pale yellow powder, as shown in Fig. 1a. SEM images (Fig. 1b-f) indicate that all products show a uniform nanofibrous morphology. The melamine-free PF sample displays the finest fiber in thickness. When increasing the amount of melamine, the as-obtained


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PMF polymeric fibers become thick. By contrast, the phloroglucinol-free MF sample presents uniform microspheres, as reported by Zhou et al.25 TEM images provide more details of the inner structure of the fibers, as shown in Fig. 2. The PF sample originating from polycondensation of phloroglucinol and formaldehyde presents bunches of fibers. Close inspection indicates that the fibers align together and single fibers can be scarcely found (Fig. 2a). When introducing melamine to the phloroglucinol-formaldehyde synthesis system, the fibrous bundles separate and some single fibers are observed (Fig. 2d). The co-condensation of equivalent MF and PF system produces homogeneous PMF fibers with diameter of about 20 nm (Fig. 2b). When the mass ratio of the MF to PF system is 2, the diameter of the PMF nanofibers (PMF-2) increases but the uniformity decays, ranging from 30 nm to 100 nm (Fig. 2c). As shown in Scheme 1, the condensation among the hydroxymethyl

groups

between

formaldehyde-phloroglucinol

and

formaldehyde-melamine gives the hydroxymethyl derivatives. Upon heating, these

hydroxymethylated

species

undergo

further

condensation

and

crosslinking, resulting in the methylene bridged polymers. In the case of MF formation, the melamine is bridged by -NH-CH2-NH-, which is long and flexible. Driven by the potential of surface free energy minimization, microspherical particles are formed under the hydrothermal conditions. By contrast, in PF, the phloroglucinol is bridged by the shorter methylene groups. The steric hindrance from the hydroxyl groups on phloroglucinol brings forth



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the rigidity of the network. The in-plane condensation in addition to the steric hindrance tends to the formation of sheet structure, which is inclined to wrinkle and curve, resulting in the formation of fibrous structures. The FT-IR spectra (Fig. 3) reveal absorption peaks of the quadrant (1555 cm-1), semicircle stretching (1490 cm-1) and breathing (1340 cm-1) of the triazine ring, indicating the successful incorporation of the melamine into the network. The intensity of these peaks decreases in line with the content of melamine in the samples and fades away for the sample PF. Band of C=C stretching vibrations (1620 cm-1) attributed to the phenol ring of phloroglucinol appears in the spectra of PF and PMFs. Accordingly, the band intensity reduces with the decrease of the phloroglucinol content. The FT-IR spectra confirm the successful build-up of a three-dimensional phloroglucinol-melamine-formaldehyde (PMF) network. From the

13

C solid state

NMR spectra (Fig. 4), one can see that the PMF-1 sample displays signals at 106, 151, and 166 ppm, designated to the sp2 carbons on the benzene ring connected to methylene group, hydroxyl group, and the ones on the triazine ring, respectively. For the PF sample, the signal at 166 ppm disappears, indicating the absence of the triazine ring in PF. Instead, a signal at 160 ppm appears, which could also be designated to the sp2 carbons on the benzene ring connected to hydroxyl group but shifting downfield due to the steric hindrance effect of the benzene rings. Additionally, the PMF nanofibers exhibit fairly good thermal stability. Exothermic peak attributing to the organic decomposition appears around 573 K (Fig. S1).


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N2 adsorption-desorption isotherms at 77 K of the synthesized networks display a type II profile, indicating the majority of macropores (Fig. 5). One can observe that very steep climbs present on isotherms at relative pressure ranging from 0.95 to 0.99 as a consequence of N2 condensation in secondary pores or external surfaces. With the increase of the melamine amount, the N2 adsorption amount in the whole relative pressure range decrease correspondingly. For the sample of microspherical MF, in which phloroglucinol is absent, almost no adsorption occurs. The porosity data are summarized in Table 2. The sample of PF shows a specific surface area and a pore volume of 143 m2 g-1 and 0.30 cm3 g-1, respectively. Both the surface area and pore volume decrease when increasing the melamine content in the final fibers. As shown in Scheme 1, in the microspherical MF, the melamine is linked by the long and flexible -NH-CH2-NH-. As a result, the formed networks lack of rigidity. The pores or voids could not be formed. While in PF and PMF networks, the phloroglucinol is linked by the shorter methylene groups. The three hydroxyl groups on phloroglucinol inhibit free rotation and folding of phenolic ring due to the steric hindrance effect, confirmed by the

13

C NMR experiments. The rigid networks

form voids, giving rise to the microporosity of the fibrous structures. The nanofibers pack together and form secondary pores. CO2 adsorption on the as-prepared PMF nanofibers was investigated by the volumetric method. PMF-1 shows a CO2 adsorption amount of 1.12 mmol g-1 at the pressure of 118 kPa and 298 K, be equivalent to previously reported PAF-4



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[porous aromatic frameworks-4, poly(p-tetraphenylene) germane reported by Ben et al. 12], which has the specific surface area of up to 2246 m2 g-1 (Fig. 6a). By contrast, the melamine-free PF sample with the largest specific surface area and micropore volume only displays a CO2 amount adsorbed of 0.62 mmol g-1 (Fig. 6a). Additionally, almost no adsorption of CO2 is observed on the MF microspheres and no CO2 adsorption isotherm was acquired, as reported by Zhou et al.25 The fact indicates that both the functional groups and accessible surfaces are necessary for the CO2 adsorption. In the case of low pressure adsorption, the microporosity as well as the amine groups of the fibrous structures account for the CO2 adsorption. High pressure adsorption isotherms indicate that CO2 amount adsorbed increases with an increase of pressure. PMF-1 sample synthesized with equivalent melamine and phloroglucinol shows the best CO2 adsorption performance, on which an adsorption amount of 2.9 mmol g-1 at 298 K and 10 bar is available (Fig. 6b). Separation of binary gas mixture of CO2-N2 and CO2-CH4 on PMF-1 sample was tested by the breakthrough column technique. As shown in Fig. 7, at the beginning, CO2, N2 and CH4 are all retained in the column. Then the weakly adsorbed gas N2 or CH4 elutes followed by the more strongly adsorbed gas CO2. Under the investigated conditions, complete separations of CO2-N2 and CO2-CH4 mixtures were achieved on PMF-1. Interestingly, unlike some previously reported amino functionalized adsorbents,16,32,33 which could only be regenerated at evaluated temperatures, the PMF-1 can be easily regenerated by


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only purging in He flow rather than raising the temperature (Fig. S2), indicating this materials could be used as pressure swing adsorption (PSA) adsorbents. Increasing the regularity and microporosity of the polymeric framework by optimizing the synthetic conditions could improve the CO2 adsorption properties of the PMF polymeric materials. Here we decided to adopt a posttreatment procedure, i.e. carbonization, to improve the porosity and the adsorption properties. Phloroglucinol-Melamine-Formaldehyde (PMF) carbon fibers A PMF-1 sample was reproduced and used as the parent sample for carbonization. The PMF-1 sample was carbonized at different temperatures in nitrogen atmosphere to improve the porosity and the adsorption properties. After carbonization, color changes from pale yellow to black (Fig. 8a). SEM images show that the samples of PMF-1-700 and PMF-1-800 keep the fibrous morphology (Fig. 8b, c). On the other hand, the fibrous morphology of PMF-1-900 vanishes during the carbonization process at very high temperature of 1173 K (Fig. 8d). From the TEM images, one can see that the fibrous structures of PMF-1-700 and PMF-1-800 are dispersible even after calcined at 973 K and 1073 K, respectively (Fig. 9a, b). For the sample of PMF-1-900, the fibrous structures are fused together to form the large particles (Fig. 9c). The N2 adsorption-desorption isotherms of the carbonized samples are shown in Fig. 10. The isotherms of all the carbonized samples exhibit type I, indicating the presence of micropores. The porosity parameters are summarized



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in Table 3. The specific surface areas and pore volumes, especially micropore volume, for carbonized samples are greatly improved, compared to the parent PMF-1 sample. The PMF-1-800 sample carbonized at 1073 K shows the highest BET surface area and pore volume of 459 m2 g-1 and 0.34 cm3 g-1, respectively. Carbonization at 1173 K destroys fibrous structures forming large particles, which has been confirmed by the SEM and TEM observations. Element analysis of PMF-1 and corresponding carbonized samples indicates that the carbon content increases from 44.3 wt.% to more than 67 wt.% after carbonization at 973 K. Additionally, the carbonization degree increases with raising the temperature. On the other hand, the nitrogen content decreases from 24.4 wt.% to 11.6 wt.%, 9.6 wt.%, and 6.6 wt.% after the PMF-1 sample were carbonized at 973 K, 1073 K, and 1173 K, respectively (Table S1). The triazine rings almost disappear, confirmed by the FT-IR (Fig. S3). XPS spectra (Fig. S4) also reveal the changes occurring in N and C contents presented on the PMF-1 and corresponding carbonized PMF-1-800 surface. As shown in Fig. 11, all carbonized samples show improved CO2 adsorption amount compared with the parent PMF-1 sample. The parent PMF-1 sample displays about 1.33 mmol g-1 CO2 adsorption amount at 298 K and 100 kPa. The CO2 amount adsorbed is improved to 2.1 mmol g-1 on the carbonized PMF-1-800 sample. The nitrogen and abundant microporosity in carbonized PMF-1-800 sample are responsible for the improved CO2 adsorption property.27,34


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The developed synthetic approach by introducing phloroglucinol to a conventional melamine-formaldehyde resin synthesis system opens an opportunity for the fabrication of porous amine based polymeric materials. The facile hydrothermal synthesis conditions, the low-cost starting materials as well as the easy regeneration during CO2 capture operations endow the PMF polymer nanofibers with a promising prospect as CO2 adsorbents from both economical and environmental point of view.

Conclusions Phloroglucinol-melamine-formaldehyde (PMF) polymer nanofibers with diameters ranging from 20 nm to 100 nm were hydrothermally synthesized through a simply hydrothermal polycondensation. The PMF sample synthesized with equivalent amount of phloroglucinol and melamine shows a specific surface area of 52 m2 g-1, much larger than that synthesized in the absence of phloroglucinol, which presences microspherical morphology. A CO2 amount adsorbed of 1.12 mmol g-1 can be achieved on the PMF sample at 298 K and 118 kPa. Separation of mixture gases of either CO2-N2 or CO2-CH4 is available on the PMF sample. Carbonization of the PMF polymeric nanofibers generates nitrogen-rich carbon nanofibers (NCF). Optimal NCF sample carbonized at 1073 K exhibits a CO2 adsorption amount of 2.1 mmol g-1 at 298 K and 100 kPa.

Supporting information



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TG-DSC, capture-regeneration breakthrough curves, FT-IR, element analysis, XPS spectra. This material is available free of Charge via the Internet at http://pubs.acs.org.

Acknowledgements Financial support by the National Natural Science Foundation of China (21303166 and 21471131) is gratefully acknowledged. Q.X. thanks Prof. Jianwu Xie for the discussion of solid state 13C NMR.

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(16) Hao, S.; Xiao, Q.; Yang, H.; Zhong, Y.; Pepe, F.; Zhu, W. Synthesis and CO2 adsorption property of amino-functionalized silica nanospheres with centrosymmetric radial mesopores. Micropor. Mesopor. Mater. 2010, 132, 552. (17) Lu, W.; Sculley, J. P.; Yuan, D.; Krishna, R.; Wei, Z.; Zhou, H. C. Polyamine-tethered porous polymer networks for carbon dioxide capture from flue gas. Angew. Chem. Int. Ed. 2012, 51, 7480. (18) Hiyoshi, N.; Yogo, K.; Yashima, T. Adsorption of carbon dioxide on aminosilane-modified mesoporous silica. J. Jpn. Petrol. Inst. 2005, 48, 29. (19) Ma, X.; Wang, X.; Song, C. "Molecular basket" sorbents for separation of CO2 and H2S from various gas streams. J. Am. Chem. Soc. 2009, 131, 5777. (20) Xing, W.; Liu, C.; Zhou, Z.; Zhang, L.; Zhou, J.; Zhuo, S.; Yan, Z.; Gao, H.; Wang, G.; Qiao, S. Z. Superior CO2 uptake of n-doped activated carbon through hydrogen-bonding interaction. Energy Environ. Sci. 2012, 5, 7323. (21) Schwab, M. G.; Fassbender, B.; Spiess, H. W.; Thomas, A.; Feng, X.; Müllen, K. Catalyst-free preparation of melamine-based microporous polymer networks through schiff base chemistry. J. Am. Chem. Soc. 2009, 131, 7216. (22) Schwab, M. G.; Crespy, D.; Feng, X.; Landfester, K.; Muellen, K. Preparation of microporous melamine-based polymer networks in an anhydrous high-temperature miniemulsion. Macromol. Rapid Commun. 2011, 32, 1798. (23) Hu, J. X.; Shang, H.; Wang, J. G.; Luo, L.; Xiao, Q.; Zhong, Y. J.; Zhu, W. D. Highly enhanced selectivity and easy regeneration for the separation of CO2 over N2 on melamine-based microporous organic polymers. Ind. Eng. Chem. Res. 2014, 53,


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Tetraethylenepentamine-modified siliceous mesocellular foam (MCF) for CO2 capture. Ind. Eng. Chem. Res. 2013, 52, 4221. (34) Wickramaratne, N. P.; Jaroniec, M. Importance of small micropores in CO2 capture by phenolic resin-based activated carbon spheres. J Mater. Chem. A 2013, 1, 112.


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Table 1

The compositions for the hydrothermal synthesis of the polymeric samples Mixture A

Mixture B

sample

phloroglucinol/ g

formaldehyde solution/g

H2O/ml

melamine/g

formaldehyde solution/g

H2O/ml

PF MF PMF-1 PMF-2 PMF-3

4.414 4.414 2.207 4.414

8.522 8.522 4.261 8.522

40 40 20 40

4.414 4.414 4.414 2.207

8.522 8.522 8.522 4.261

40 40 40 20



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Table 2

Pore textural properties of the synthesized polymer samples

sample

SBET /m2·g-1

Smicro /m2·g-1

Vtotal /cm3·g-1

Vmicro /cm3·g-1

PF MF PMF-1 PMF-2 PMF-3

143 1.2 42 22 52

31 0 8.7 4.2 11

0.30 0.01 0.13 0.06 0.23

0.013 0 0.004 0.002 0.006


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Table 3 Pore textural properties of the synthesized polymer samples after carbonized at different temperatures sample

SBET /m2·g-1

Smicro /m2·g-1

Vtotal cm3·g-1

PMF-1-700 PMF-1-800 PMF-1-900

425 459 309

383 394 201

0.24 0.34 0.17

/


Vmicro cm3·g-1 0.15 0.15 0.08

/


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Figure captions Fig. 1

Photograph of PMF-1 (a) and SEM images of PF (b), MF (c), PMF-1 (d),

PMF-2 (e), PMF-3 (f) Fig. 2

TEM images of PF(a), PMF-1(b), PMF-2(c), PMF-3(d), insets are

corresponding low magnification images. Fig. 3

FT-IR spectra of PF (a), MF (b), PMF-1 (c), PMF-2 (d), PMF-3 (e).

Fig. 4

13

Fig. 5

77 K, N2 adsorption-desorption isotherms of the synthesized fibers. Inset:

C solid state NMR spectra of PF and PMF-1 samples.

isotherms in log scale. Fig. 6

Low pressure (a) and high pressure (b) CO2 adsorption isotherms of PF and

PMF nanofibers at 298 K. Fig. 7

Breakthrough curves of equivalent CO2−N2 and CO2−CH4 mixtures on

PMF-1. Fig. 8

Photograph of PMF-1-700 (a) and SEM images of PMF-1-700 (b),

PMF-1-800 (c), and PMF-1-900 (d). Fig. 9

TEM images of PMF-1-700 (a), PMF-1-800 (b), and PMF-1-900 (c).

Fig. 10 77 K N2 adsorption-desorption isotherms of the carbonized samples. Fig. 11 CO2 adsorption isotherms of PMF-1 and corresponding carbonization samples at 298 K.


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Scheme 1 Schematic representation of the preparation of PMF networks.



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Fig. 1


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Fig. 2



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Fig. 3


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Fig. 4



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Fig. 5


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Fig. 6



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Fig. 7


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Fig. 8



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Fig. 9


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Fig. 10



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Fig. 11


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Table of Contents (TOC) Graphic



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Scheme 1 Schematic representation of the preparation of PMF networks. 44x30mm (300 x 300 DPI)


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Fig. 1 Photograph of PMF-1 (a) and SEM images of PF (b), MF (c), PMF-1 (d), PMF-2 (e), PMF-3 (f) 104x52mm (300 x 300 DPI)



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Fig. 2 TEM images of PF(a), PMF-1(b), PMF-2(c), PMF-3(d), insets are corresponding low magnification images. 140x94mm (256 x 256 DPI)


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Fig. 3 FTIR spectra of PF (a), MF (b), PMF-1 (c), PMF-2 (d), PMF-3 (e). 86x72mm (300 x 300 DPI)



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Fig. 4 13C solid state NMR spectra of PF and PMF-1 samples. 83x66mm (300 x 300 DPI)


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Fig. 5 77 K, N2 adsorption-desorption isotherms of the synthesized fibers. Inset: isotherms in log scale. 46x34mm (300 x 300 DPI)



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Fig. 6 Low pressure (a) and high pressure (b) CO2 adsorption isotherms of PF and PMF nanofibers at 298 K. 38x15mm (300 x 300 DPI)


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Fig. 7 Breakthrough curves of equivalent CO2−N2 and CO2−CH4 mixtures on PMF-1. 50x36mm (300 x 300 DPI)



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Fig. 8 Photograph of PMF-1-700 (a) and SEM images of PMF-1-700 (b), PMF-1-800 (c), and PMF-1-900 (d). 70x52mm (300 x 300 DPI)


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Fig. 9 TEM images of PMF-1-700 (a), PMF-1-800 (b), and PMF-1-900 (c). 126x28mm (300 x 300 DPI)



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Fig. 10 77 K N2 adsorption-desorption isotherms of the carbonized samples. 87x69mm (300 x 300 DPI)


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Fig. 11 CO2 adsorption isotherms of PMF-1 and corresponding carbonization samples at 298 K. 47x36mm (300 x 300 DPI)


Synthesis, Carbonization, and CO2 Adsorption Properties of

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