Constructing benzoxazine-containing porous organic polymers for carbon dioxide and hydrogen sorption

Accepted Manuscript Constructing benzoxazine-containing porous organic polymers for carbon dioxide and hydrogen sorption Xuejiao Sun, Jianquan Li, Weiguo Wang, Qingyu Ma PII: DOI: Reference:

S0014-3057(18)31065-6 https://doi.org/10.1016/j.eurpolymj.2018.07.043 EPJ 8505

To appear in:

European Polymer Journal

Received Date: Revised Date: Accepted Date:

10 June 2018 17 July 2018 24 July 2018

Please cite this article as: Sun, X., Li, J., Wang, W., Ma, Q., Constructing benzoxazine-containing porous organic polymers for carbon dioxide and hydrogen sorption, European Polymer Journal (2018), doi: https://doi.org/10.1016/ j.eurpolymj.2018.07.043

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Constructing benzoxazine-containing porous organic polymers for carbon dioxide and hydrogen sorption Xuejiao Sun,a,b Jianquan Li,a,b Weiguo Wang,a,b Qingyu Maa,b,* a

Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, University of Jinan, Jinan 250022, China

b

School of Materials Science and Engineering, University of Jinan, Jinan 250022, China * Corresponding authors: [email protected]

Abstract Two novel benzoxazine-containing porous polymers, BPOP-1 and BPOP-2, have been synthesized by the direct Sonogashira-Hagihara coupling reactions of two brominated benzoxazine derivatives with a tetrahedral silicon-centered monomer. These polymers exhibit high porosity with the highest Brunauer-Emmer-Teller (BET) surface area of 623 m2 g-1 and the highest total pore volume of up to 1.78 cm3 g-1. Porosity comparison with other benzoxazine-containing porous polymers shows that the introduction of tetrahedral silicon-centered units into the porous networks is an efficient strategy to improve the porosity of the final porous polymers. For applications, these polymers possess good carbon dioxide uptakes of up to 1.79 mmol g-1 (7.9 wt%) at 273 K and 1.0 bar, a comparably high binding ability with CO2 with an adsorption enthalpy of up to 29.6 kJ mol-1, as well as a moderate hydrogen uptake of up to 5.87 mmol g-1 (1.12 wt%) at 77 K and 1.0 bar. These values are comparable to or higher than other porous polymers with a level of surface areas and previously reported benzoxazine-containing porous polymers, thereby suggesting their potential applications as efficient solid absorbents for storing CO2 and H2. Keywords porous organic polymers, benzoxazine; gas storage; carbon dioxide sorption; hydrogen sorption 1

1. Introduction Porous organic polymers (POPs) as an emerging class of porous materials have drawn much attention in recent years due to their extensive applications in gas separation, catalysis, light harvesting, sensors, energy storage, drug delivery and release, removal of pollutants, etc [1-4]. POPs can be categorized into four types: polymer of intrinsic microporosity (PIMs), hyper-crosslinked polymers (HCPs), conjugated microporous polymers (CMPs) and covalent organic frameworks (COFs) [5]. To design high-performance POP materials, two key factors, i.e., suitable monomers and polymerization methodologies, should be deliberately considered because of their correspondence to the stability and linkage efficiency of target porous networks. Among various monomers, tetrahedral silicon-centered compounds have attracted specific attention because porous polymers can be easily designed to exhibit high surface areas when using them as building units, which can lack the flexibility to pack efficiently thus resulting in facile formation of free volumes to promote the porosity [6, 7]. For example, a porous polymer with a ultrahigh BET surface area of 6461 m2 g-1 has been synthesized by the Yamamoto reaction of tetrakis(4-bromophenyl)silane [6]. Meanwhile, diversified polymerization reactions including Sonogashira-Hagihara reaction [8], Suzuki reaction [9, 10], Yamamoto reaction [6], Schiff reaction [11] and Friedel-Crafts reaction [12], have been utilized to prepare various POP materials. From the viewpoint of applications, gas adsorption, particularly carbon dioxide (CO2) storage and capture, has become an important topic for POP materials since CO2 is thought to be the main contributor for global warming [13-15]. To enhance CO2 adsorption capacity, an efficient strategy is the incorporation of heteroatoms (e.g., nitrogen, oxygen, sulfur and phosphorus) [16-18] or functional groups (e.g., amine, carboxyl, hydroxyl) [19, 20] within the networks due to the enhanced 2

affinity towards CO2 molecules. For example, Kang and co-workers reported highly selective CO2capturing polymeric organic networks derived from pyridine or thiophene- containing monomers due to the dipole-dipole interaction between CO2 and long-pair electrons on the nitrogen or sulfur atoms [21]. Apparently, a facile approach to realize this incorporation is direct utilization of heteroatomcontaining compounds as monomers. Among these monomers, benzoxazine derivatives, could be an ideal class of options because they simultaneously contain oxygen and nitrogen atoms within the structures, endowing the resultant porous materials with high content of heteroatoms and thus improved CO2 adsorption performance, in addition to high thermal stability and uniquely electronic and mechanical properties [22]. However, benzoxazine-based porous materials have been rarely investigated and only few functional porous organic materials or porous carbons derived from polybenzoxazine resins have been reported for CO2 capture, removal of mercury salts and electrochemical energy storage [23-27]. For example, Xu et al. reported benzoxazine-containing POPs by the condensation reactions of diamines, triphenol and paraformaldehyde [28]. However, these polymers exhibit low surface area and benzoxazine rings maybe not completely formed within the networks. Developing novel benzoxazine-containing POP materials is still highly desired. Herein, we present two novel benzoxazine-based porous organic polymers (BPOPs) based on tetrakis(4-ethynylphenyl)silane and dibrominated benzoxazine derivatives (BO-1 and BO-2) by Sonogashira-Hagihara coupling reactions (Scheme 1). In contrast to the formation of benzoxazine rings during the process of constructing porous networks [28], the present strategy is direct and benzoxazine units within the networks were first built as monomers BO-1 and BO-2. The resultant polymers show high porosity and moderate thermal stability. Moreover, their applications in CO2 and H2 adsorption has been also explored. 3

Scheme 1. Synthesis routes of benzoxazine-based porous organic polymers, BPOP-1 and BPOP-2. (i) Pd(PPh3)4/CuI, DMF/i-Pr2NH, 80ºC, 72h. The fragments of these porous polymers are shown as examples.

2. Experimental 2.1 Materials Unless otherwise stated, all the reagents were purchased from commercial suppliers and used without further purification. 6-Bromo-3-(4-bromophenyl)-3,4-dihydro-2H-1,3-benzoxazine (BO-1), 6-bromo-3-(3-bromophenyl)-3,4-dihydro-2H-1,3-benzoxazine

(BO-2)

and

tetrakis(4-

ethynylphenyl)silane were synthesized according to previous reports [29, 30]. Diisopropylamine (iPr2NH) was dried over CaH2 and used freshly. N,N-Dimethylformamide (DMF) was dried over CaH2 at 80℃ for 12 h, distilled under vacuum pressure and stored with 4 Å molecule sieves prior to use. 2.2 Synthesis of BPOP-1 and BPOP-2 BPOP-1. Under argon, Pd(PPh3)4 (0.024 g, 0.126 mmol), CuI (0.0526 g, 0.075mmol), BO-1 (0.36 g, 4

1.25 mmol) and tetrakis(4-ethynylphenyl)silane (0.27 g, 0.625 mmol) were added to a three-necked flask containing 20 mL of i-Pr2NH and 20 mL of DMF. Then the mixture was stirred at 80℃ for 72 h under argon. Then the mixture was cooled to room temperature, filtered and washed with distilled water, methanol, chloroform, tetrahydrofuran (THF) and acetone to remove amine salts, unconsumed monomers and catalyst residues. Further purification was carried out by exhaustive Soxhlet extraction with methanol for 24 h and THF for 24 h. Then the product was dried in vacuum at 80℃ for at least 12 h and BPOP-1 was afforded as a yellow solid (0.30 g, yield: 37.9%). Elemental analysis calc. (wt.%) for C60H38N2O2Si: C 85.08, H 4.52, N 3.31; Found C 84.20, H 4.23, N 4.35. BPOP-2. The synthetic procedure and post-treatment of BPOP-2 were similar to those used for BPOP-1 except that BO-1 was replaced by BO-2. BPOP-2 was afforded as a black solid (0.26 g, yield: 32.9%). Elemental analysis calc. (wt.%) for C60H38N2O2Si: C 85.08, H 4.52, N 3.31; Found C 84.40, H 4.52, N 4.13. 2.3 Characterization Fourier transform infrared (FT-IR) spectra were recorded in the wavenumber range of 400~4000 cm-1 using Bruker Tensor27 spectrophotometer. Solid-state 13C cross-polarization/magicangle- spinning (CP/MAS) NMR and

29Si

MAS NMR measurements were measured on a Bruker

AVANCE-500 NMR Spectrometer which is operating with a 5 mm tri-resonance MAS probe. Elemental analyses were conducted using an Elementar vario EL III elemental analyzer. Field-emission scanning electron microscopy experiments (FE-SEM) were performed by using FEI QUANTA FEG250 Spectrometer. Thermogravimetric analyses were performed with a MettlerToledo SDTA-854 TGA system in nitrogen at a heating rate of 10°C min-1 to 800°C. 5

Nitrogen sorption isotherms at 77 K were measured using Micromeritics ASAP 2020 surface area and porosity analyzer. Before the measurements, samples were degassed at 100°C for at least 12 h. A sample of ca. 100 mg and a UHP-graded nitrogen (99.999%) gas source were used in the measurements. BET surface areas were determined over a P/P0 range from 0.01 to 0.20. The pore size distributions were calculated based on a non-local density functional theory method (NL-DFT) using the carbon/slit-cylindrical pore mode of Micromeritics software. Carbon dioxide (CO2) sorption isotherms at 273 K and 298 K, and hydrogen (H2) adsorption isotherms were measured at 77 K on Micromeritics ASAP 2020 instrument. Prior to the measurements, the samples were pre-treated and degassed at 100°C for at least 12 h under vacuum.

3. Results and discussion 3.1. Synthesis and Characterization As shown in Scheme 1, benzoxazine-containing porous polymers, BPOP-1 and BPOP-2, were prepared by the Sonogashira-Hagihara coupling reactions of a silicon-centered monomer, tetrakis(4ethynylphenyl)silane with two brominated benzoxazine derivatives, BO-1 and BO-2. The reactions were conducted using Pd(PPh3)/CuI as the catalyst system and i-Pr2NH as the acid absorbent in DMF at 80ºC for 72 h. The crude products were washed with various solvents, treated with exhaustive Soxhlet extraction and dried under vacuum at 80ºC for 12 h to afford the final products. However, the yields are relatively low. This finding can be explained by the loss during the extraction process and the products with a low crosslinking degree may be partially soluble in the solvents. The collected products after extraction with high crosslinking degree are insoluble in common solvents such as THF, methanol, acetone, DMF and dimethylsulfoxide. Similar to previous reports [31, 32], a small difference was found between the theoretical and found contents of carbon, hydrogen and 6

nitrogen determined by elemental analysis. This difference may be attributed to the incomplete reactions, some residuals such as amine salts, solvents or catalysts, and incomplete combustion. The polymers were first characterized by FT-IR spectroscopy (Fig. 1). The weak peak at ca. 2200 cm-1 has been attributed to the bis-substituted acetylene (-C≡C-) bond, thereby indicating the successful linking of two starting monomers. The peaks at 1250 cm-1 and 1030 cm-1 are assigned to the asymmetric and symmetric stretching vibration peak of C-O-C, while the peak at 1081 cm-1 is assigned to asymmetric stretching of C-N-C [26, 28]. These results confirm the presence of benzoxazine units in the frameworks. The peaks from 1650 to 1380 cm-1 with moderate intensities have been attributed to the C=C stretching vibration from phenyl rings. In addition, a broad peak at ca. 3450 cm-1 may be assigned to –OH groups from water embedded in the samples.

Fig. 1. FT-IR spectra of BPOP-1 (black) and BPOP-2 (red). The characteristic peaks are indicated with arrows.

Then the structures of the polymers were determined by solid-state 13C CP/MAS NMR and 29 Si NMR spectroscopy. The 13C CP/MAS NMR spectra are shown in Fig. 2 along with the assignments 7

of their resonances. As expected, BPOP-1 and BPOP-2 show similar spectra because of their similar chemical structures. The peak ca. 90 ppm can be assigned to the ethynylene units (-C≡ C-) and carbon atom from the methylene units between oxygen and nitrogen in benzoxazine rings, which confirms the formation of internal triple bonds and thus success of the coupling reactions. The strong signals in the range of 110~150 ppm can be assigned to the sp2 phenylene carbon atoms in the silicon-centered units and benzoxazine units. In addition, the resonances appearing around 50 ppm can be attributed to the methylene carbon atoms attached to nitrogen atom. For

29

Si NMR

spectra, only one resonance peak is observed at -14.0 ppm and -14.3 ppm for BPOP-1 and BPOP-2, respectively (Fig. 3), and has been assigned to Si atom in the silicon-centered units. These results are consistent with other silicon-containing porous polymers [31, 33, 34].

Fig. 2. Solid-state 13C CP/MAS NMR spectra of BPOP-1 (black, down) and BPOP-2 (red, up)

8

Fig. 3. Solid-state 29 Si CP/MAS NMR spectra of (a) BPOP-1 and (b) BPOP-2

3.2. Porosity The porosity and porous structures of the polymers were evaluated by nitrogen adsorption and desorption experiments at 77 K. Fig. 4a shows the N2 isotherms of BPOP-1 and BPOP-2, from which BET specific surface area (SBET), microporous surface area (Smicro), total pore volume (Vtotal) and microporous volume (Vmicro) are calculated, and Table 1 summarizes the porosity data of each polymer. BPOP-1 gives rise to a type I isotherm with some type IV isotherm characteristics at higher relative pressure according to the IUPAC classification [35]. BPOP-1 exhibits a sharp uptake at lower relative pressure and gradually increasing uptake at higher relative pressure with hysteresis to a degree, thereby indicating the coexistence of micropores and mesopores within the structure. BPOP-2 gives rise to a combination of type I isotherm and type II isotherm with a sharp uptake at low relative pressure and then a continuously increasing uptake at higher relative uptake. The sharp uptake at a high relative pressure above 0.90 may arise in part from the interparticulate porosity associated with the meso- and macrostructures of the sample and their interparticulate voids. BPOP-1 exhibits a high porosity with SBET of 623 m2 g-1 and Vtotal of 0.48 cm3 g-1, whereas BPOP-2 has a 9

lower SBET of 238 m2 g-1, but much higher Vtotal of 1.78 cm3 g-1. The microporous properties of these polymers was calculated using t-plot method. The Smicro and Vmicro of BPOP-1 are 330 m2 g-1 and 0.13 cm3 g-1, and thus Vmicro/Vtotal ratio, which represents the contribution of microporosity to the network, is 0.27, which indicates the presence of micropores and mesopores within the network. In contrast, it is found that there is nearly no microporosity for BPOP-2 with Smicro and Vmicro of 53 m2 g1

and 0.06 cm3 g–1. Then the pore size distributions (PSDs) of BPOP-1and BPOP-2 were evaluated

by non-local density functional theory (NLDFT). As shown in Fig. 4b, BPOP-1 possesses a combination of micropores centered at 1.35 nm and mesopores centered at 3.93 nm, while BPOP-2 contains a narrow micropore centered at 1.40 nm and a very broad mesopores from 2 to 30 nm. The PSDs are in accord with the shape of the N2 isotherms.

Fig. 4. (a) Nitrogen adsorption (close symbols) and desorption (open symbols) isotherms of BPOP-1 (black) and BPOP-2 (red) at 77 K; (b) Pore size distributions of BPOP-1 (black) and BPOP-2 (red) evaluated by NLDFT. Table 1. Porosity data of BPOP-1 and BPOP-2 SBET[a]

Smicro[b]

Vtotal[c]

Vmicro[d]

/m2 g–1

/m2 g–1

/cm3 g–1

/cm3 g–1

BPOP-1

623

330

0.48

0.13

BPOP-2

238

53

1.78

0.06

Samples

10

CO2 uptake[e]

H2 uptake[f]

(wt%)

(wt%)

0.27

7.9

1.12

0.03

6.4

0.45

Vmicro/Vtotal

[a] Surface area calculated from N2 adsorption isotherm using the BET method; [b] Microporous surface area calculated from N2 adsorption isotherm using t-plot method; [c] Total pore volume calculated at P/P0=0.99; [d] Microspore volume derived using the t-plot method based on the Halsey thickness equation; [e] Carbon dioxide uptake at 273 K and 1.0 bar; [f] Hydrogen uptake at 77 K and 1.0 bar.

The porosity difference between BPOP-1 and BPOP-2 could be explained by the structure geometry of two benzoxazine-base monomers, BO-1 and BO-2. Compared to BO-1, BO-2 has a higher kinked geometry, which can lead to a distorted cross-linked network for BPOP-2 and thus result in more mesopores and decreased surface area. This phenomenon has been also found in our previous reports [31, 32]. For example, porous polymer derived from tetrakis(4-bromophenyl)silane with the reaction site at para- position exhibited higher surface area and microporosity than that from tetrakis(3-bromophenyl)silane with the reaction site at meta- position. Compared to other benzoxazine-based porous materials, the porosity of the present materials is higher or comparable. For example, Xu et al. have synthesized benzoxazine-containing porous polymers by condensation reaction of diamine, triphenol and paraformaldehyde and the polymers exhibited lower porosity with SBET of only up to 231 m2 g-1 [28]. Herein the enhanced porosity can be explained by two aspects. One is the incomplete formation of benzoxazine units by condensation reaction. It is known that benzoxazine shows a half chair conformation structure in space [36] and endows the six-ring structure with certain rigidity, resulting in a stable porous network. However, the formation of benzoxazine rings is incomplete, especially during the process that reaction mixture changed from homogenous system to heterogenous system. Therefore, in the final networks, there are a few unreacted groups such as amine and hydroxyl groups, which would occupy the volume and lower the porosity. In contrast, benzoxazine rings have been formed before the formation of porosity in the 11

present materials. Another is the introduction of tetrahedral silicon-centered units into the porous networks, which have been widely used as efficient monomers to enhance the porosity of porous materials [6, 7]. The present results further prove the effectivity of this strategy. In addition, the difference porosity of these two polymers reveals that altering the monomer species is a useful strategy to tune the porosity of the polymers, which are consistent with previous reports [37, 38]. 3.3. Thermal properties and morphology The thermal stability of these polymers was estimated by thermogravimetric analysis (TGA) under N2 with a heating rate of 10 °C min-1. The materials show a moderate thermal stability with Td,5% (decomposition temperature at 5% mass loss) at ca. 200°C (Fig. 5). Their morphology and particle size were observed by field-emission scanning electron microscopy (FE-SEM). BPOP-1 has an irregularly shaped particles with a wide range of size distribution from 100 nm to tens of micrometers (Fig. 6a), while BPOP-2 shows a similar morphology with irregular shapes but aggregating into large particles with the size of ca. 1 μm (Fig. 6b).

Fig. 5. TGA curves of BPOP-1 (black) and BPOP-2 (red) in nitrogen atmosphere with a heating rate 12

of 10 °C min-1

Fig. 6. FE-SEM images of BPOP-1 (a) and BPOP-2 (b). The scale bar is 1 μm.

3.4. Carbon dioxide and hydrogen sorption The presence of benzoxazine units with abundant nitrogen and oxygen atoms in the networks, which can provide high affinity towards gas molecules and thus high gas storage, promoted us to investigate their gas sorption properties. Therefore, CO2 sorption experiments of BPOP-1 and BPOP2 were first performed at 273 K and 298 K in order to evaluate their potential applications in carbon dioxide capture and storage. Fig. 7a shows the CO2 isotherms and Table 1 summarizes the data. BPOP-1 exhibits a high CO2 uptake of 1.79 mmol g-1 (7.9 wt%) at 273 K and 1.0 bar, and 0.98 mmol g-1 (4.3 wt%) at 298 K and 1.0 bar. Compared to BPOP-1, BPOP-2 expectedly possesses a lower CO2 uptake of 1.45 mmol g-1 (6.4 wt%) at 273 K and 1.0 bar, and 0.67 mmol g-1 (2.9 wt%) at 298 K and 1.0 bar. This finding is obviously due to lower surface area of BPOP-2 than BPOP-1, particularly lower microporosity, which has been found to be the main contribution to CO2 adsorption [39, 40]. These values are higher, or comparable to other polymers with a level of or higher surface areas, such as POP-2 (791 m2 g-1, 7.88 wt% at 273 K/1.0 bar) [31] and COF-102 (SBET: 3620 m2 g-1, 1.56 mmol g-1 at 273 K/1.0 bar) [41], even higher than porous polymers containing 13

electron-rich groups, such as triphenylamine-based polymer PTPA-3 (530 m2 g-1, 6.5 wt% at 273 K/1.0 bar) [42], ferrocene-containing material Fc-CMP-1 (519 m2 g-1, 1.45 mmol g-1 at 273 K/1.0 bar) [43] and benzoxazine-linked material BoxPOP-1 (231 m2 g-1, 5.5 wt% at 273 K/1.0 bar) [28] (Table 2). In addition, the hysteresis found in desorption isotherms can be explained by the delayed condensation effect, which is due to the presence of mesopores within the structure, similar to the nitrogen isotherms. Then the isosteric heat of adsorption (QST) was calculated from CO2 isotherms employing the Clausius-Clapeyron equation. It is found that both of them possess a relatively high enthalpy with QST of 29.6 kJ mol-1 and 28.6 kJ mol-1 for BPOP-1 and BPOP-2 at low coverage and a gradual decrease at higher coverage (Fig. 7b), indicating that there is a high affinity between the network and CO2 molecules. This high binding ability is apparently attributed to the heteroatoms (O and N atoms) from the benzoxazine units in the frameworks. Therefore, the mechanism of absorbing CO2 by these materials is a combination of physisorption and chemisorption. These results reveal that these materials could be promisingly utilized as solid absorbents for the capture and storage of CO2. Table 2. Comparison of CO2 uptakes of BPOP-1 and BPOP-2 with other porous materials Samples

SBET /m2 g–1

Method

CO2 uptake

Ref.

BPOP-1

623

273 K/1.0 bar

1.79 mmol g-1 / 7.9 wt%

This work

BPOP-2

238

273 K/1.0 bar

1.45 mmol g-1 /6.4 wt%

This work

POP-2

791

273 K/1.0 bar

7.88 wt%

[31]

COF-102

3620

273 K/1.0 bar

1.56 mmol g-1

[41]

PTPA-3

530

273 K/1.0 bar

6.5 wt%

[42]

Fc-CMP-1

519

273 K/1.0 bar

1.45 mmol g-1

[43]

BoxPOP-1

231

273 K/1.0 bar

5.5 wt%

[28]

The hydrogen adsorption experiments of BPOP-1 and BPOP-2 were also carried out at 77 K 14

and pressures up to 1.0 bar. The H2 uptakes can reach 5.87 mmol g-1 (1.12 wt%) and 2.26 mmol g-1 (0.45 wt%) for BPOP-1 and BPOP-2, respectively (Fig. 7c and Table 1). Under the same conditions (77 K/1.0 bar), the values are higher or comparable with other porous materials, such as SBA-15 (992 m2 g-1, 0.5 wt%) [44], TPOP-5 (810 m2 g-1, 1.07 wt%) [45] and BLP-1 (Cl) (1364 m2 g-1, 1.10 wt%) [46]. Thus, BPOP-1 and BPOP-2 can be also applied as absorbents in the area of hydrogen storage.

Fig. 7. (a) CO2 adsorption (close symbols) and desorption (open symbols) isotherms of BPOP-1 and BPOP-2 at 273 k and 298 K; (b) Isosteric heat of CO2 adsorption of FPOP-1 and FPOP-2; (c) H2 adsorption isotherm of BPOP-1 and BPOP-2 at 77 K.

4. Conclusion In summary, we report two novel benzoxazine-containing porous organic polymers (BPOP-1 and BPOP-2) based on tetrahedral silicon-centered monomer and brominated benzoxazine derivatives by Sonogashira-Hagihara coupling reactions. The resultant polymers show moderate thermal stability and high porosity with the highest BET surface areas of 622 m2 g-1 and the highest total pore volumes of 1.78 cm3 g-1. The porosity is higher than previously reported benzoxazinecontaining porous polymers, which indicates that the incorporation of tetrahedral silicon-centered units into the porous structures could efficiently enhance their porosity. Moreover, these polymers 15

possess good carbon dioxide capacities and hydrogen storage, thereby suggesting that these materials could be potentially applied as promising candidates for storing carbon dioxide and hydrogen.

Acknowledgements This work was supported by the National Natural Science Foundation of China (Grant No. 51373069) and the Natural Science Foundation of Shandong Province (Grant ZR2016EMM07).

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Graphical Abstract

Highlights 

Novel benzoxazine-containing porous organic polymers



High porosity with the highest BET surface area of 623 m2 g-1



Potential applications for storing CO2 and H2

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