Mesoporous Conjugated Polycarbazole with High Porosity via

Aug 27, 2014 - which is the highest specific surface area among the reported porous conjugated polycarbazoles by the same method. Mesoporous CPOP-9 ...
0 downloads 0 Views 340KB Size
Download PDF
Article pubs.acs.org/Macromolecules

Mesoporous Conjugated Polycarbazole with High Porosity via Structure Tuning Qi Chen, De-Peng Liu, Jian-Hua Zhu, and Bao-Hang Han* National Center for Nanoscience and Technology, Beijing 100190, China S Supporting Information *

ABSTRACT: Monomer building units play a key role in the porosity and adsorption performance of porous conjugated polymers. Three tetracarbazolyl-substituted monomers (Cz8−10) with similar molecular structures were designed and prepared in order to tune the porosity and pore size distribution of the obtained porous conjugated polycarbazoles (CPOP-8−10) via FeCl3-promoted carbazole-based oxidative coupling polymerization. Polymers CPOP-8 and CPOP-10 exhibit microporous nature similar to most of reported conjugated microporous polymers. Porosity analysis and adsorption performance indicate that CPOP-9 is predominantly mesoporous. The Brunauer−Emmett−Teller specific surface area of CPOP-9 is up to 2440 m2 g−1, which is the highest specific surface area among the reported porous conjugated polycarbazoles by the same method. Mesoporous CPOP-9 shows higher water vapor uptake capacity (804 mg g−1) than microporous polymers CPOP-8 (208 mg g−1) and CPOP-10 (181 mg g−1) at water saturated vapor pressure and 298 K, which might imply that pore size has a key effect on wettability of the porous polymers. With high specific surface area and pore volume, CPOP-9 exhibits high hydrogen uptake of 5.22 wt % (77 K) and carbon dioxide uptake of 70.0 wt % (298 K) at 18.0 bar. Additionally, the uptake capacity of CPOP-9 for toluene is high up to 1355 mg g−1 at the saturated vapor pressure (298 K). The adsorption performance of CPOP-9 can be comparable with that of the known porous organic polymers with ultrahigh specific surface area, such as PAF-1 and PNN-4, under the same conditions.

■

INTRODUCTION Owing to the special features such as high specific surface area, good chemical/thermal stability, and low skeleton density, porous organic polymers have been investigated for potential applications in the fields related to energy, environment, and catalysis.1,2 Versatile structural building units and proper polymerization methods have been used to smoothly furnish porous organic polymers with varying specific surface area via a template-free approach.3,4 However, pore size distribution (PSD) tuning is still a challenging work in porous polymers research. As a porous organic polymer with regular structure, covalent organic frameworks (COFs) are highly crystalline and assembled via dynamic covalent bonds,5 which is therefore advantageous to tailor the pore diameter from micropore size to mesopore size by tuning molecular structure of monomer.6,7 With respect to the amorphous conjugated porous polymer, both the phase separation process and the molecular structure of the polymers have great effects on PSD of materials.8 Cooper and co-workers have demonstrated the feasibility of systematically controlling the pore architecture and a general strategy of fine-tuning the surface area by copolymerization of monomers with different “strut lengths”.9 Liu, Yu, and co-workers also reported a series of porous polyphenylenes with tunable diameters ranging from 0.7 to 0.9 nm.10 To our best knowledge, for most of reported porous conjugated polymers, © 2014 American Chemical Society

their PSD and related tuning are in the range of micropore size. Reported examples of mesoporous conjugated polymer are very limited. Permanently mesoporous PPV-type network was obtained by Cooper and co-workers through Gilch coupling chemistry, its Brunauer−Emmett−Teller (BET) specific surface area is about 750 m2 g−1, and the microporosity (micropore volume/total pore volume) is around 11%.11 Zhou and coworkers reported a series of porous polymer networks (PPNs) with ultrahigh surface area have been synthesized with optimized Yamamoto homocoupling procedures; most of the pore sizes sit within the microporous/mesoporous range.12 We have reported a facile preparation of porous conjugated polycarbazoles through carbazole-based oxidative coupling polymerization promoted by FeCl3.13,14 Through a simple purification process, the metal catalyst can be easily and completely removed from the final materials. Considering that no other reactive groups participate in the coupling reaction, property and function based on the building blocks are probably to be fully kept, and structural characterization of the resulting materials is much easier. All previously obtained porous conjugated polycarbazoles are microporous materials, which show potential applications in gas storage/separation and Received: June 27, 2014 Revised: August 10, 2014 Published: August 27, 2014 5926

dx.doi.org/10.1021/ma501330v | Macromolecules 2014, 47, 5926−5931

Macromolecules

Article

heterogeneous catalysis.15 Herein, we reported mesoporous conjugated polycarbazole with high porosity obtained by the same method via tuning molecular structure of monomers. The material exhibits good adsorption performance for gas (hydrogen and carbon dioxide) and vapor (water and toluene), in which the related capacities can comparable with those of the known porous organic polymers with ultrahigh specific surface area, such as PAF-116 and PNN-4.12

■

ether/dichloromethane = 20/1) to produce a white solid 120 mg (33%). 1H NMR (CDCl3, 400 MHz) δ: 8.14 (d, 8H, J = 7.6 Hz), 7.58 (d, 8H, J = 8.4 Hz), 7.45 (t, 8H, J = 7.6 Hz), 7.41 (t, 2H, J = 2.0 Hz), 7.31 (t, 8H, J = 7.6 Hz), 7.17 (d, 4H, J = 2.4 Hz). 13C NMR (CDCl3, 100 MHz) δ: 142.8, 140.5, 140.3, 126.3, 125.0, 124.3, 123.7, 120.6, 120.5, 109.6. MS (MALDI-TOF): m/z calculated for C60H38N4: 814.31 [M]; found: 814.06 [M]. Synthesis of Cz-9. A mixture of compound 1 (1.0 g, 2.1 mmol) and BDBA (155 mg, about 0.90 mmol) in DMF (40 mL) was degassed by the freeze−pump−thaw cycles. After addition of an aqueous potassium carbonate solution (2.0 M, 10 mL) and tetrakis(triphenylphosphine)palladium(0) (50 mg, 55 μmol), the resulting solution was degassed and protected by nitrogen and then stirred at 120 °C for 24 h. When the mixture was cooled to room temperature and poured into water, the final solution was extracted with 2 × 50 mL of ethyl acetate. The combined extract was washed with water (20 mL), dried over Na2SO4, and evaporated under reduced pressure to afford the crude Cz-9. After purification by silica column chromatography (petroleum ether/dichloromethane = 8/1), pure Cz-9 was obtained as a white solid 850 mg (50%). 1H NMR (CDCl3, 400 MHz) δ: 8.19 (d, 8H, J = 8.0 Hz), 7.90 (d, 4H, J = 1.2 Hz), 7.84 (s, 6H), 7.64 (d, 8H, J = 8.0 Hz), 7.48 (t, 8H, J = 7.6 Hz),. 7.34 (t, 8H, J = 7.4 Hz). 13C NMR (CDCl3, 100 MHz) δ: 143.8, 140.6, 139.9, 139.3, 127.9, 126.3, 124.2, 124.1, 123.7, 120.5, 120.5, 109.7. MS (MALDI-TOF): m/z calculated for C66H42N4: 890.34 [M]; found: 890.38 [M]. Synthesis of Cz-10. Compound 2 (550 mg, 1.1 mmol) and 4,4′dibromobipenyl (170 mg, about 0.55 mmol) were dissolved in DMF (40 mL) and degassed by the freeze−pump−thaw cycles. To the mixture were added an aqueous solution of potassium carbonate (2.0 M, 10 mL) and tetrakis(triphenylphosphine)palladium(0) (50 mg, 55 μmol). The resulting solution was degassed, purged with nitrogen, and stirred at 120 °C for 24 h. When the mixture was cooled to room temperature, the final solution was poured into water and extracted with 2 × 50 mL of ethyl acetate. The extract was washed with water (20 mL), dried over Na2SO4, and evaporated under reduced pressure to afford the crude Cz-10. Purification by silica column chromatography (petroleum ether/dichloromethane = 20/1) gives pure Cz-10 as a white solid 180 mg (37%). 1H NMR (CDCl3, 400 MHz) δ: 8.18 (d, 8H, J = 7.6 Hz), 7.99 (d, 4H, J = 2.0 Hz), 7.83−7.80 (m, 8H, J = 7.6 Hz), 7.63 (d, 8H, J = 8.0 Hz), 7.47 (t, 8H, J = 7.6 Hz), 7.33 (t, 8H, J = 7.4 Hz). MS (MALDI-TOF): m/z calculated for C72H46N4: 996.37 [M]; found: 996.32 [M]. Synthesis of CPOP-8−10 by Carbazole-Based Oxidative Coupling Polymerization. A slightly modified procedure of carbazole-based oxidative coupling polymerization14 for preparation of CPOP-9 from Cz-9 is given as follows: a solution of Cz-9 (150 mg, 0.17 mmol) in anhydrous chloroform (15 mL) was transferred dropwise to a suspension of ferric chloride (655 mg, 4.0 mmol) in anhydrous chloroform (25 mL). The mixture was stirred overnight under nitrogen at room temperature, and then 50 mL of methanol was added to quench the reaction. The resulting mixture was kept stirring for another hour to dissolve the ferric chloride solid. The solid was collected by filtration and washed with methanol. The obtained crude CPOP-9 was stirred vigorously in hydrochloric acid solution (1.0 M) for 2 h and then filtered and washed with water and methanol. The material was further extracted in a Soxhlet extractor with methanol (24 h) and then with THF (24 h). The desired polymer CPOP-9 (yellowish solid) was collected and dried in vacuum oven at 110 °C overnight (yield: 98%). CPOP-8 and CPOP-10 can be obtained by the same procedure, when CZ-8 and Cz-10 are used as the monomer, respectively.

EXPERIMENTAL SECTION

Materials. All chemical reagents were commercially available and used as received unless otherwise stated. Benzene-1,4-diboronic acid (BDBA), 4,4′-dibromobipenyl, and tetrakis(triphenylphosphine)palladium(0) were purchased from Acros. 9,9′-(5-Bromo-1,3phenylene)bis(9H-carbazole) (1) was prepared according to the reported procedure.13 Structure Characterization and Analysis. The 1H and 13C NMR spectra of all organic compounds were obtained on a Bruker DMX400 NMR spectrometer. Solid-state cross-polarization magic angle spinning (CP/MAS) NMR spectra were obtained on a Bruker Avance III 400 NMR spectrometer. Mass spectra were obtained with a Microflex LRF MALDI-TOF mass spectrometer (Bruker Daltonics). Thermogravimetric analysis (TGA) was carried out on a Pyris Diamond thermogravimetric/differential thermal analyzer by heating (10 °C min−1) the samples to 800 °C under a nitrogen atmosphere. Scanning electron microscopy (SEM) observation was performed using a Hitachi S-4800 microscope (Hitachi Ltd., Japan) without sputter coating. The fluorescence spectrum was recorded using a PerkinElmer LS55 luminescence spectrometer. The ultraviolet−visible (UV−vis) spectrum was measured using a PerkinElmer Lamda 950 UV−vis−NIR spectrophotometer. Porosities Studies and Adsorption Measurements. Gas (nitrogen, carbon dioxide, and hydrogen) sorption isotherms under low pressure (0−1.13 bar) were recorded with Micromeritics TriStar II 3020 or Micromeritics ASAP 2020 M+C accelerated surface area and porosimetry analyzers at certain temperature (all the samples were degassed at 120 °C for 12 h before measurement). BET specific surface area and micropore surface area were evaluated based on the obtained adsorption−desorption isotherms. The PSD of materials was calculated from the related adsorption branch by the nonlocal density function theory (NLDFT) approach. Total pore volume was calculated from nitrogen adsorption−desorption isotherms at P/P0 = 0.99. The vapor (water and toluene) adsorption−desorption isotherms and gas (hydrogen and carbon dioxide) uptake capacities under high pressure (0−18.0 bar) were performed and measured on an IGA-100B intelligent gravimetric analyzer (Hiden Isochema Ltd., UK). Synthesis of Cz-8. To a stirred mixture of compound 1 (500 mg, 1.02 mmol) and 15 mL of dry tetrahydrofuran (THF) was added dropwise a solution of n-butyllithium (2.0 mL, 4.8 mmol) in hexane under nitrogen at −78 °C. The resulting suspension was stirred at −78 °C for 1 h. Tri-isopropyl borate (0.72 mL, 3.1 mmol) was added all at once, and the final mixture was stirred for 1 h at −78 °C and overnight at room temperature. The mixture was poured into 50 mL of 10% HCl solution. After stirring for 30 min, the product was extracted with 2 × 50 mL of ethyl acetate. The extract was washed with saturated aqueous sodium chloride solution (20 mL), dried over Na2SO4, and evaporated under reduced pressure to afford the boronic acid 2 as a crude solid. Without further purification, compound 1 (259 mg, 0.53 mmol) and the boronic acid 2 (200 mg, about 0.40 mmol) were dissolved in dimethylformamide (DMF, 40 mL), and the mixture was degassed by the freeze−pump−thaw cycles. After addition of an aqueous potassium carbonate solution (2.0 M, 10 mL) and tetrakis(triphenylphosphine)palladium(0) (50 mg, 55 μmol), the resulting solution was degassed and protected by nitrogen and then stirred at 120 °C for 24 h. When the mixture was cooled to room temperature, the final solution was poured into water and extracted with ethyl acetate (2 × 50 mL). The extract was washed with water (20 mL) and dried over Na2SO4. Solvent was removed under diminished pressure to give the crude Cz8, which was purified by silica column chromatography (petroleum

■

RESULTS AND DISCUSSION Since the building blocks show a great influence on the porosity, specific surface area, and gas adsorption capacity of porous conjugated polymers,17,18 design or selection of specific monomer is very important. It has been found that propellerlike building block 1,3,5-tri(9-carbazolyl)benzene13 and tetra5927

dx.doi.org/10.1021/ma501330v | Macromolecules 2014, 47, 5926−5931

Macromolecules

Article

carbazolyl-substituted monomers14 can afford porous conjugated polycarbzoles with high porosities. Therefore, we combined their structure features to design and synthesize three tetracarbazolyl-substituted monomers (Cz-8−10) with similar molecular structures (the related energy minimized 3-D structural model of monomers is shown in Figure S1 (Supporting Information)) in order to tune the porosity of the porous conjugated polycarbazoles. FeCl3-catalyzed oxidative coupling polymerization of corresponding monomers can smoothly afford polymers CPOP-8−10 (Scheme 1) at room temperature. Scheme 1. Preparation of Monomers Cz-8−10 and Porous Conjugated Polycarbazoles CPOP-8−10 Figure 1. 13C CP/MAS NMR spectra of CPOP-8−10.

The porosity studies of the polymers were carried out by nitrogen sorption analysis. Main porosity information on materials can be obtained from nitrogen adsorption− desorption isotherms of polymers CPOP-8−10 measured at 77 K (Figure 2a) and their corresponding PSD profiles (Figure 2b) calculated from the related adsorption branch of the isotherms by the NLDFT approach. Polymers CPOP-8 and CPOP-10 with dominant pore sizes centered at 0.63 nm exhibit

Similar to most of reported porous conjugated polymers, all the obtained polymers exhibit good chemical stability, even treated with dilute solution of HCl or NaOH. Thermogravimetric analysis indicates that the materials show a high thermal stability and 5% mass loss of all polymers was observed between 400 and 550 °C under a nitrogen atmosphere (Figure S2, Supporting Information). Owing to the cross-linking nature of network structures, there is no evidence for distinct glass transition for the materials below their thermal decomposition temperature.19 CPOP-10 exhibits a lower decomposition temperature (about 400 °C) at 5% mass loss than those of other two polymers (above 500 °C). The molecular structures of all the polymers were characterized and confirmed by the 13 C CP/MAS NMR spectrum. Owing to the similarity of the molecular structures, five broad peaks, approximately at 140, 132, 125, 120, and 109 ppm, were observed for the three obtained polymers derived from the similar repeating units shown in Figure 1. The SEM images of the obtained polymers are shown in Figures S3a-c (Supporting Information). For CPOP-8 and CPOP-9, similar morphology was observed to be solid submicrometer particles with different size between 80 and 300 nm. As to CPOP-10, its SEM image indicates the block-shaped and plate-like structures. Both 13C CP/MAS NMR spectra and SEM images of the obtained polymers are found to be similar to reported porous conjugated polycarbazoles14 due to the same category in chemical nature and the same preparative method.

Figure 2. (a) Nitrogen adsorption−desorption isotherms of CPOP8−10 measured at 77 K; the adsorption and desorption branches are labeled with solid and open symbols, respectively. (b) PSD profiles of CPOP-8−10 calculated by NLDFT. 5928

dx.doi.org/10.1021/ma501330v | Macromolecules 2014, 47, 5926−5931

Macromolecules

Article

microporous and hydrophobic nature of CPOP-8 and CPOP10, the two polymers show similarly low water uptake of 208 and 181 mg g−1 at water saturated vapor pressure, respectively. With regard to CPOP-9, as a mesoporous material, mesopore filling starts at relative pressures above 0.7, and uptake capacity for water increases steeply to 804 mg g−1 at water saturated vapor pressure. The much higher water uptake of CPOP-9 can be attributed to physisorption, swelling, and capillary condensation in the mesopores of the material. The water adsorption−desorption isotherms of CPOP-9 are similar to those of the reported mesoporous carbon materials.22 Mesopore filling is accompanied by hysteresis which might be caused by different mechanisms of adsorption/pore filling and desorption for hydrophobic porous materials.23 The key porous properties of the obtained polymers derived from the corresponding isotherm such as the BET specific surface area, pore volume, dominant pore size, and uptake performance are listed in Table 1. On the basis of the hydrogen (77 K) and carbon dioxide (273 K) physisorption isotherms of obtained polymers measured with a pressure up to 1.13 bar (Figures S4a and 4b, Supporting Information), we can find an increasing trend in gas uptake capacity with increasing specific surface area and pore volume. Polymer CPOP-9, possessing the highest BET specific surface area and total pore volume, exhibits the highest hydrogen uptake of 2.44 wt % (77 K) and carbon dioxide uptake of 18.0 wt % (273 K) at 1.0 bar among the obtained polymers. The hydrogen uptake capacity is relatively lower than that of CPOP-1 (2.80 wt %, SBET = 2220 m2 g−1) but still higher than most of reported porous polymers under the same conditions.24 Further test displays that CPOP-9 also shows high hydrogen uptake of 5.22 wt % (77 K) at 18.0 bar (Figure 4), which can be comparable with PAF-1 (about

a combination of type I and II nitrogen sorption isotherms according to the IUPAC classification,20 showing their microporous nature similar to most of reported conjugated microporous polymers. The BET specific surface area values of CPOP-8 and CPOP-10 are 1610 and 1110 m2 g−1, respectively. As for CPOP-9, its dominant pore sizes are located in mesoporous range between 2.5 and 5.0 nm, associated with 0.63 nm, which imply that CPOP-9 possesses mesoporous feature. The total pore volume at a relative pressure of 0.99 is calculated to be 2.04 cm3 g−1, and its micropore volume is 0.12 cm3 g−1 calculated using the t-plot method. Thus, the microporosity is around 6%, further indicating that CPOP-9 is predominantly mesoporous. The BET specific surface area of CPOP-9 is up to 2440 m2 g−1, which is the highest specific surface area among the reported porous conjugated polycarbazoles via the same method.13−15,21 The molecular structure feature of building blocks (Figure S1, Supporting Information) can give some clues to analyze and explain the porosities and PSD results of the obtained polymers. From CPOP-8 to CPOP-9, the length of repeating units increases, and the network with longer repeating units may exhibit the higher specific surface area and possess the larger pore sizes up to mesoporous range. Further increase in the length of repeating units (from CPOP-9 to CPOP-10) can induce its increased degree of conformational freedom, leading to greater intramolecular intercalation and entanglement of fragments as mentioned by Cooper.9 Therefore, the specific surface area of material decreases, and its dominant pore size is still located in the microporous range. The porous nature of the polymers can also be confirmed by measuring the water adsorption−desorption isotherms on CPOP-8−10 at 298 K. As shown in Figure 3, due to the

Figure 3. Water vapor adsorption−desorption isotherms of polymers CPOP-8−10 at 298 K.

Figure 4. Gas adsorption−desorption isotherms of CPOP-9 under high pressure: H2 at 77 K; CO2 at 298 K.

Table 1. Porosity Properties and Adsorption Performance of CPOP-8−10 polymers

SBETa (m2 g−1)

Smicrob (m2 g−1)

Vtotalc (cm3 g−1)

Dpored (nm)

H2 uptakee (wt %)

CO2 uptakef (wt %)

H2O uptakeg (mg g−1)

CPOP-8 CPOP-9 CPOP-10

1610 2440 1110

430 180 650

1.71 2.04 0.76

0.63 0.63, 2.5−5.0 0.63

1.92 2.44 1.38

16.5 18.2 14.8

208 804 181

a

Specific surface area calculated from the adsorption branch of the nitrogen adsorption−desorption isotherm using the BET method. bMicropore surface area calculated from the adsorption branch of the nitrogen adsorption−desorption isotherm using the t-plot method. cTotal pore volume at P/P0 = 0.99. dData calculated from nitrogen adsorption−desorption isotherms with the NLDFT method. eData were obtained at 1.0 bar and 77 K. f Data were obtained at 1.0 bar and 273 K. gData were obtained at water vapor saturated pressure of 298 K. 5929

dx.doi.org/10.1021/ma501330v | Macromolecules 2014, 47, 5926−5931

Macromolecules

Article

5.80 wt %, SBET = 5640 m2 g−1) under the same conditions. The carbon dioxide uptake capacity of CPOP-9 is 70.0 wt % at 298 K and 18.0 bar (Figure 4), possessing the similar adsorption performance with PPN-4 (about 75.0 wt % at 295 K, SBET = 6461 m2 g−1) under the same pressure. The isosteric heat of adsorption (Qst) for hydrogen was calculated from adsorption data collected at 77 and 87 K (Figure S5a, Supporting Information). At zero coverage, the Qst is 6.9 kJ mol−1 and shows a gradual drop as more hydrogen gets adsorbed (Figure S6a, Supporting Information). The Qst for CO2 is also calculated based on adsorption isotherms of CO2 at different temperatures (273 and 291 K, Figure S5b in the Supporting Information). We find that the isosteric heat of CPOP-9 is about 24.5 kJ mol−1 at zero coverage and decreases slowly to 22.3 kJ mol−1 when the uptake capacity reaches 2.5 mmol g−1 (Figure S6b, Supporting Information). Both the isosteric heat values are similar to those of other reported porous polymers.25 The sorption behavior of CPOP-9 for toluene was also measured at 298 K. As shown in Figure 5, the uptake amount

microporous polymers. As for CPOP-9, porosity analysis and adsorption performance indicate that the polymer is predominantly mesoporous. The BET specific surface area of CPOP-9 is up to 2440 m2 g−1, which is the highest specific surface area among the reported porous conjugated polycarbazoles by the same method. Further studies show that CPOP-9 exhibits high hydrogen uptake of 5.22 wt % (77 K) and carbon dioxide uptake of 70.0 wt % (298 K) at 18.0 bar. The uptake capacity of CPOP-9 for toluene is also high up to 1355 mg g−1 at the saturated vapor pressure (298 K). The adsorption performance of CPOP-9 can be comparable with that of the known porous organic polymers with ultrahigh specific surface area, such as PAF-1 and PNN-4, under the same conditions. According to the results of porosity and adsorption performance, mesoporous conjugated polycarbazole with high porosity can be obtained via molecular structure tuning.

■

ASSOCIATED CONTENT

* Supporting Information S

Energy minimized 3-D structural model of monomers Cz-8− 10; TGA plots and TEM images of CPOP-8−10, gas (H2 and CO2) adsorption isotherms of CPOP-8−10 with pressure up to 1.13 bar; H2 and CO2 adsorption isotherms of CPOP-9 at different temperatures; isosteric heat plots of H2 and CO2 adsorption for CPOP-9; optical spectra of CPOP-9 in solid state; 1H NMR, 13C NMR, and MS of monomers. This material is available free of charge via the Internet at http://pubs.acs.org.

■

AUTHOR INFORMATION

Corresponding Author

*Tel +86 10 8254 5576; e-mail [email protected] (B.-H.H.). Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The financial support of the Ministry of Science and Technology of China (Grant 2014CB932200) and National Science Foundation of China (Grants 21274033 and 21374024) is acknowledged.

Figure 5. Toluene vapor adsorption−desorption isotherms of polymer CPOP-9 at 298 K.

for toluene rises significantly at the lower relative pressure and becomes flat until the material reaches saturation. It is worth to note that the uptake capacity of CPOP-9 for toluene is high up to 1355 mg g−1 at the saturated vapor pressure, which is nearly same to that of PAF-1 (1357 mg g−1) under the same conditions. The high uptake capacity of CPOP-9 for toluene could be ascribed to its high porosity and strong affinity to the absorbent molecules, which would have potential use to eliminate harmful small aromatic molecules in the environment. The mesoporous polycarbazole CPOP-9 exhibits intrinsic photoluminescence property similar to other reported porous conjugated polycarbazoles.13,14 Its optical spectra in the solid state (Figure S7, Supporting Information) indicate the maximum emission wavelength of CPOP-9 is about 505 nm, which is ascribed to the π−π* transition of the conjugated network.

■

REFERENCES

(1) (a) 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 (10), 4239−4245. (b) Thomas, A.; Kuhn, P.; Weber, J.; Titirici, M.; Antonietti, M. Porous Polymers: Enabling Solutions for Energy Applications. Macromol. Rapid Commun. 2009, 30 (4−5), 221−236. (2) (a) Zhang, Y.; Riduan, S. N. Functional Porous Organic Polymers for Heterogeneous Catalysis. Chem. Soc. Rev. 2012, 41 (6), 2083− 2094. (b) Kaur, P.; Hupp, J. T.; Nguyen, S. B. T. Porous Organic Polymers in Catalysis: Opportunities and Challenges. ACS Catal. 2011, 1 (7), 819−835. (3) (a) McKeown, N. B.; Budd, P. M. Exploitation of Intrinsic Microporosity in Polymer-Based Materials. Macromolecules 2010, 43 (12), 5163−5176. (b) Wu, D.; Xu, F.; Sun, B.; Fu, R.; He, H.; Matyjaszewski, K. Design and Preparation of Porous Polymers. Chem. Rev. 2012, 112 (7), 3959−4015. (4) (a) Xu, Y.; Jin, S.; Xu, H.; Nagai, A.; Jiang, D. Conjugated Microporous Polymers: Design, Synthesis and Application. Chem. Soc. Rev. 2013, 42 (20), 8012−8031. (b) Dawson, R.; Cooper, A. I.; Adams, D. J. Nanoporous Organic Polymer Networks. Prog. Polym. Sci. 2012, 37 (4), 530−563. (5) (a) Feng, X.; Ding, X.; Jiang, D. Covalent Organic Frameworks. Chem. Soc. Rev. 2012, 41 (18), 6010−6022. (b) Ding, S.-Y.; Wang, W.

■

CONCLUSION In summary, three porous conjugated polycarbazoles (CPOP8−10) were prepared through FeCl3-promoted carbazole-based oxidative coupling polymerization of three tetracarbazolylsubstituted monomers (Cz-8−10) with similar molecular structures. Polymers CPOP-8 and CPOP-10 exhibit microporous nature similar to most of reported conjugated 5930

dx.doi.org/10.1021/ma501330v | Macromolecules 2014, 47, 5926−5931

Macromolecules

Article

Covalent Organic Frameworks (COFs): from Design to Applications. Chem. Soc. Rev. 2013, 42 (2), 548−568. (6) Côté, A. P.; El-Kaderi, H. M.; Furukawa, H.; Hunt, J. R.; Yaghi, O. M. Reticular Synthesis of Microporous and Mesoporous 2D Covalent Organic Frameworks. J. Am. Chem. Soc. 2007, 129 (43), 12914−12915. (7) (a) Tilford, R. W.; Mugavero, S. J., III; Pellechia, P. J.; Lavigne, J. J. Tailoring Microporosity in Covalent Organic Frameworks. Adv. Mater. 2008, 20 (14), 2741−2746. (b) Spitler, E. L.; Colson, J. W.; Uribe-Romo, F. J.; Woll, A. R.; Giovino, M. R.; Saldivar, A.; Dichtel, W. R. Lattice Expansion of Highly Oriented 2D Phthalocyanine Covalent Organic Framework Films. Angew. Chem., Int. Ed. 2012, 51 (11), 2623−2627. (8) 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 (45), 8574−8578. (9) Jiang, J. X.; Su, F.; Trewin, A.; Wood, C. D.; Niu, H.; Jones, J. T. A.; Khimyak, Y. Z.; Cooper, A. I. Synthetic Control of the Pore Dimension and Surface Area in Conjugated Microporous Polymer and Copolymer Networks. J. Am. Chem. Soc. 2008, 130 (24), 7710−7720. (10) Yuan, S.; Dorney, B.; White, D.; Kirklin, S.; Zapol, P.; Yu, L.; Liu, D. J. Microporous Polyphenylenes with Tunable Pore Size for Hydrogen Storage. Chem. Commun. 2010, 46 (25), 4547−4549. (11) Dawson, R.; Su, F.; Niu, H.; Wood, C. D.; Jones, J. T. A.; Khimyak, Y. Z.; Cooper, A. I. Mesoporous Poly(phenylenevinylene) Networks. Macromolecules 2008, 41 (5), 1591−1593. (12) Yuan, D.; Lu, W.; Zhao, D.; Zhou, H.-C. Highly Stable Porous Polymer Networks with Exceptionally High Gas-Uptake Capacities. Adv. Mater. 2011, 23 (32), 3723−3725. (13) Chen, Q.; Luo, M.; Hammershøj, P.; 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 (14), 6084−6087. (14) Chen, Q.; Liu, D.-P.; Luo, M.; Feng, L.-J.; Zhao, Y.-C.; Han, B.H. Nitrogen-Containing Microporous Conjugated Polymers via Carbazole-Based Oxidative Coupling Polymerization: Preparation, Porosity, and Gas Uptake. Small 2014, 10 (2), 308−315. (15) Feng, L.-J.; Chen, Q.; Zhu, J.-H.; Liu, D.-P.; Zhao, Y.-C.; Han, B.-H. Adsorption Performance and Catalytic Activity of Porous Conjugated Polyporphyrins via Carbazole-Based Oxidative Coupling Polymerization. Polym. Chem. 2014, 5 (8), 3081−3088. (16) Ben, T.; Rao, H.; Ma, S.; Cao, D.; Lan, J.; Jing, X.; Wang, W.; Xu, J.; Deng, F.; Simmons, J. M.; Qui, S.; Zhu, G. Targeted Synthesis of a Porous Aromatic Framework with High Stability and Exceptionally High Surface Area. Angew. Chem., Int. Ed. 2009, 48 (50), 9457− 9460. (17) Lu, W.; Yuan, D.; Zhao, D.; Schilling, C. I.; Plietzsch, O.; Muller, T.; Bräse, S.; Guenther, J.; Blümel, J.; Krishna, R.; Li, Z.; Zhou, H. C. Porous Polymer Networks: Synthesis, Porosity, and Applications in Gas Storage/Separation. Chem. Mater. 2010, 22 (21), 5964−5972. (18) Chen, Q.; Wang, J.-X.; Wang, Q.; Bian, N.; Li, Z.-H.; Han, B.-H. Spiro(fluorene-9,9′-xanthene)-Based Porous Organic Polymers: Preparation, Porosity and Exceptional Hydrogen Uptake at Low Pressure. Macromolecules 2011, 44 (20), 7987−7993. (19) Chen, Q.; Wang, J.-X.; Yang, F.; Zhou, D.; Bian, N.; Zhang, X.J.; Yan, C.-G.; Han, B.-H. Tetraphenylethylene-Based Fluorescent Porous Organic Polymers: Preparation, Gas Sorption Properties, and Photoluminescence Properties. J. Mater. Chem. 2011, 21 (35), 13554− 13560. (20) Sing, K. S. W.; Everett, D. H.; Haul, R. A. W.; Moscou, L.; Pierotti, R. A.; Rouquér ol, J.; Siemieniewska, T. Reporting Physisorption Date for Gas/Solid Systems with Special Reference to the Determination of Surface Area and Porosity. Pure Appl. Chem. 1985, 57 (4), 603−619. (21) Zhang, X.; Lu, J.; Zhang, J. Porosity Enhancement of Carbazolic Porous Organic Frameworks Using Dendritic Building Blocks for Gas Storage and Separation. Chem. Mater. 2014, 26 (13), 4024−4029.

(22) Morishige, K.; Kawai, T.; Kittaka, S. Capillary Condensation of Water in Mesoporous Carbon. J. Phys. Chem. C 2014, 118 (9), 4664− 4669. (23) Thommes, M.; Morell, J.; Cychosz, K. A.; Fröba, M. Combining Nitrogen, Argon, and Water Adsorption for Advanced Characterization of Ordered Mesoporous Carbons (CMKs) and Periodic Mesoporous Organosilicas (PMOs). Langmuir 2013, 29 (48), 14893− 14902. (24) (a) Ghanem, B. S.; Hashem, M.; Harris, K. D. M.; Msayib, K. J.; Xu, M.; Budd, P. M.; Chaukura, N.; Book, D.; Tedds, S.; Walton, A.; McKeown, N. B. Triptycene-Based Polymers of Intrinsic Microporosity: Organic Materials that Can Be Tailored for Gas Adsorption. Macromolecules 2010, 43 (12), 5287−5294. (b) Germain, J.; Frechét, J. M. J.; Svec, F. Nanoporous Polymers for Hydrogen Storage. Small 2009, 5 (10), 1098−1111. (25) (a) Rabbani, M. G.; El-Kaderi, H. M. Template-Free Synthesis of a Highly Porous Benzimidazole-Linked Polymer for CO2 Capture and H2 Storage. Chem. Mater. 2011, 23 (7), 1650−1653. (b) Zhu, Y.; Long, H.; Zhang, W. Imine-Linked Porous Polymer Frameworks with High Small Gas (H2, CO2, CH4, C2H2) Uptake and CO2/N2 Selectivity. Chem. Mater. 2013, 25 (9), 1630−1635.

5931

dx.doi.org/10.1021/ma501330v | Macromolecules 2014, 47, 5926−5931