Construction of Microporous Organic Nanotubes Based on Scholl

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C: Surfaces, Interfaces, Porous Materials, and Catalysis

Construction of Microporous Organic Nanotubes Based on Scholl Reaction Zidong He, Tianqi Wang, Yang Xu, Minghong Zhou, Wei Yu, Buyin Shi, and Kun Huang J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.8b00469 • Publication Date (Web): 05 Apr 2018 Downloaded from http://pubs.acs.org on April 11, 2018

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The Journal of Physical Chemistry

Construction of Microporous Organic Nanotubes Based on Scholl Reaction Zidong He, Tianqi Wang, Yang Xu, Minghong Zhou, Wei Yu, Buyin Shi and Kun Huang* School of Chemistry and Molecular Engineering, East China Normal University, 500 N, Dongchuan Road, Shanghai, 200241, P. R. China.

ABSTRACT:

Herein, we demonstrate a facile method for the preparation of microporous organic nanotubes (MONTs) based on a combination of hyper-crosslinking mediated self-assembling strategy and Scholl reaction by using polylactide-b-polystyrene diblock copolymers (PLA-b-PS) as precursors, in which the PS block forms the microporous organic frameworks of nanotubes through the C-C coupling reaction, while the PLA segment is completely degraded to produce the hollow mesoporous tubular structure. Owing to their high special surface area, robust organic framework and open-ended tubular structure, the obtained MONTs exhibit the outstanding adsorption capacity and efficiency for p-cresol and different organic vapors. Moreover, microporous carbon nanotubes (MCNTs) can be prepared by the further carbonization. The resultant MCNTs as electrode materials of a supercapacitor display excellent electrochemical performance with specific capacitances of up to 192 F g-1at 0.5 Ag-1, with capacitance retention of 97% even after 5000 cycles at 10 A g-1. The methodology provides a new route for fabrication

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of microporous organic nanotubes for various potential applications including energy storage, adsorption, separation and catalysis.

1. Introduction Microporous organic polymers (MOPs) with the same chemical composition can exhibit different properties by simply changing their nanostructure.1-7 As a typical example, microporous organic nanotubes (MONTs) not only possess intrinsic outstanding properties inherited from MOPs including of the high surface area, tunable chemical composition, exceptional chemical and thermal stability and easy chemical modification, but also have better mass transfer and higher active surface area ratio owing to the high aspect ratio compared with quasi-zerodimensional nano-spheres and other irregular MOPs. Therefore, MONTs have much potential applications in catalysis,8-9 drug release,10-11 separation,12 gas adsorption,13-14 template for metal oxide tubes15 or precursor for highly porous carbon nanotubes.16 To date, hard-template method as a major synthetic strategy with respective advantages and disadvantages is presented for making MONTs. In some typical works, Banerjee and Tan10, 17 used ZnO and silica nanorods as hard-templates to successfully prepare MONTs based on covalent organic frameworks (COFs) growth and hyper-crosslinking reaction, respectively. The biggest disadvantage of hard-template lies in the tedious template-removal process and sometimes utilization of harsh agent (e.g. HF). In addition, self-assemble method18-20 had recently been regarded as a kind of simple and effective method to one-step directly prepare MONTs through Sonogashira-Hagihara crosscoupling reaction or Friedel–Crafts hyper-crosslinking reaction, while this method also faced some challenges including precise monomer design and monomer concentration control. More recently, our group21-22 developed a novel method to fabricate well-controlled MONTs based on


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the intra/interbrush Fridel–Crafts hyper-crosslinking of the multi-component molecular bottlebrushes. However, the complicated preparation procedure of molecular bottlebrushes precursor limited their further application. Therefore, developing a facile method to address the above issues for preparation of MONTs still remains a scientific challenge. It is well-known that Scholl reaction as a typical C-C coupling reaction can be used to synthesize MOPs through eliminating two aryl-hydrogens between adjacent phenyl rings to form a new aryl-aryl bond.23-25 In this regard, the direct aryl-aryl coupling bond from a wide range of aromatic building blocks with different function or molecular geometry can render the obtained MOPs to possess a rigid and highly cross-linked network, which will lead to the generation of microporosity. However, the reported MOPs based on Scholl reaction always present an illdefined morphology. Utilizing Scholl reaction to prepare MOPs with special morphology is rare. Recently, our group developed a facile route to prepare hollow microporous organic nanospheres based on a combination of hyper-crosslinking mediated self-assembly strategy and Friedel-Crafts reaction by using polylactide-b-polystyrene (PLA-b-PS) diblock copolymers as precursors.26 Herein, we expanded this strategy to synthesize MONTs based on Scholl C-C coupling reaction in the presence of an anhydrous AlCl3 as catalyst and chloroform as solvent. In this work, a “nucleation-to-growth” model induced by hyper-crosslinking self-assembly process was proposed to describe the formation of MONTs. Owing to the high special surface area, robust organic framework and hierarchically porous structure, the synthesized MONTs displayed extraordinary capability for water treatment with outstanding adsorption capacities for organic vapors and p-cresol. Moreover, MONTs could be easily transformed into the microporous carbon nanotubes (MCNTs) by pyrolyzing progress, which showed the excellent electrochemical performance as electrode materials of a supercapacitor


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2. Experimental section 2.1 Materials All reagents were used as received unless stated otherwise. Styrene was passed through a basic alumina (Al2O3) column before using 2, 2-Azoisobutyronitrile (AIBN) and D, L-lactide (LA) were purified by recrystallization from methanol and ethyl acetate, respectively. PLA-b-PS diblock copolymers were synthesized according to literature procedures.26 S-1-Dodecyl-S’-(α,α’dimethyl-α”-acetic acid)trithiocarbonate (TC) was synthesized according to literature procedures.27 2.2 Measurements All 1HNMR spectra were recorded on a Bruker AVANCE IIITM 500 spectrometer (500 MHz) by using CDCl3 as a solvent. GPC data were obtained from Waters GPC system equipped with a Waters 2414 refractive index (RI) detector, a 1515 isocratic HPLC pump, and two Waters HPLC columns. THF (HPLC grade) was used as the solvent for polymers and eluent for GPC with a flow rate of 1mL/min at 30 oC. FT-IR analysis was carried out using Thermo NICOLET is50. TEM images were obtained using a Tecnai G2 F20 TEM instrument. Samples were prepared by dip-coating a 400 mesh carbon-coated copper grid from the dilute sample solution allowing the solvent to evaporate. SEM images were obtained using JEOL JSM-7800F Prime SEM instrument. The solid-state NMR spectra were recorded on a Bruker AVANCE III 400 WB spectrometer. A Quantachrome Autosorb IQ surface area and porosity analyzer was utilized to study the pore structure of the samples. Before measurements, the polymer samples were degassed for more than10 h at 110°C. The Brunauer-Emmett-Teller (BET) surface area and the micropore surface area were determined by the BET equation and the t-plot equation,


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respectively. The pore size distribution was analyzed by original density functional theory (DFT). The size distribution of micelles was determined by Nano series Nano-ZS (Malvern Instrument) Zetasizer and the experiment was carried out at 25oC. Raman spectra were collected on a ThermoDXR instrument with a λ=532 nm excitation laser. Thermogravimetric analysis (TGA) was conducted on LD12-HIRThermo Gravimetric Analyzer (NETZSCH, Germany) under a flowing N2 atmosphere and at a heating rate of 10 oC/min from 25 oC to 800oC. UV-Vis spectra were recorded using a SOPTOP UV2400 spectrophotometer. 2.3 Synthesis of Polylactide (PLA) Benzyl alcohol (30µL, 0.3 mmol), D, L-lactide(LA) (4.32 g, 30 mmol) and Sn(Oct)2 (60 mg, 0.15 mmol) were mixed in a dried round-bottomed flask. The flask was sealed and placed into 130 oC oil-bath for 3h. After the polymerization, the mixture was cooled to room temperature and dissolved in DCM, and precipitated three times in methanol. Finally, the white precipitate was collected and dried under vacuum for 24h. Yield = 3.6g (81%). GPC: Mn=15.3 kg/mol, Mw/Mn=1.25; 1H NMR: n(PLA)=156. 2.4 Synthesis of Polystyrene (PS) St (6.4 mL, 56 mmol), AIBN (2.25 mg, 0.014 mmol), and TC (50 mg, 0.14 mmol) were mixed in a reaction vessel and degassed by 3 freeze-pump-thaw cycles. The polymerization was then conducted at 80 oC for 5h. The polymer was precipitated from DCM into methanol 3 times and dried under vacuum for 24 h. Yield =1.5 g (25%). GPC: Mn=10.2 kg/mol, Mw/Mn=1.11; 1H NMR: n(St)=103.


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PLA-b-PS diblock copolymers with different molecule weight were synthesized according to our previous report.26 2.5 Preparation of MONTs PLA156-b-PS250 (50 mg) was placed in 50 ml flask and dissolved completely in 10 ml trichloromethane. Then, after purged by HCl gas, AlCl3 (184 mg) was added and stirred for 5 min. The flask was sealed and placed into 90 oC oil bath without stirring. 12 h later, the obtained product was washed by methanol/HCl (1:1), water and methanol sequentially. The resulted gray solid was further treated in a Soxhlet for 48h with ethanol followed by dried under vacuum at 60 o

C for 24h. Yiled = 40 mg.

2.6 Adsorption experiment The as-prepared product was used as the adsorbate. 10 mg adsorbates were added into 1 mL of pcresol aqueous solution with different initial concentration. The mixture was stirred at room temperature for 1 days. After adsorption, an aliquot was centrifuged at 3800 rpm for 4 min and the p-cresol concentration in the supernatant was determined using UV-Vis absorption spectroscopy. The wavelength for the detection is 273 nm for p-cresol. The adsorbed amount (W) and efficiency (E) can be calculated according to the following equation:

W=

E% =

V(C୭ − Cୣ୯ ) m

C୭ − Cୣ୯ × 100% C଴


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where Co (mg/ml) is initial concentration, Ceq (mg/ml) is adsorption equilibrium concentration, m (mg) is the amount of adsorbate, V (ml) is the volume of p-cresol aqueous solution. The adsorption kinetics tests were conducted with an initial analyte concentration of 8 mg/ml and the volume of analyte solution is 1 mL. 10 mg MONTs-PLA156-b-PS250 was immersed in the prepared analyte solution. The adsorption capacity was evaluated by UV-vis spectra in different adsorption times. 2.7 Organic vapor and water vapor experiments Typically, 50 mg sample was weighted and placed into small watch-glass, and then the watchglass was suspended beyond the organic reagents or water in a 500 ml sealed single neck flask. The mass of the sample was weighted after 24h, and the adsorption amount was calculated. 2.8 Electrochemical measurements The electrodes were prepared as follows: the carbon materials (80 wt %), carbon black (10 wt %) and polytetrafluoroethylene (10 wt %) were mixed sufficiency, and the mixture was pressed onto nickel foam. A three-electrode cell was used to measure the electrochemical properties of carbon materials. Platinum wire and mercury/mercury oxide were used as counter and reference electrodes, respectively. 6 M KOH solutions were used as electrolyte. Cyclic voltammetry and charge–discharge tests were conducted on a CHI660E electrochemical workstation. The capacitance was calculated on the basis of the galvanostatic charge and discharge curve according to the following equation

C=

I∆t m∆V


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where C (Fg-1)is the specific capacitance, I(A) is the discharging current, ∆t (s) is the discharging time, m (g) is the amount of the sample used for the preparation of the electrode, and ∆V (V) is the change of voltage during the discharging process. 3. Results and discussion The detailed synthetic procedure was illustrated in Scheme 1. Firstly, the PLA-b-PS diblock copolymers with different molecular compositions, that is, PLA60-b-PS65 (Mw/Mn= 1.18), PLA156-b-PS250 (Mw/Mn = 1.17) and PLA265-b-PS250 (Mw/Mn= 1.20) were prepared according to previous report and taken as raw materials to prepare MONTs. 1H NMR spectroscopy analyses and Gel Permeation Chromatography (GPC) were used to analyze the polymeric structure and molecular weight distributions, respectively (Figure S1 and S2). Subsequently, the synthesized PLA156-b-PS250 copolymers precursors as a typical example were dissolved in chloroform followed by the addition of AlCl3 catalyst. The reaction was conducted for 12h in a sealed flask at 90 oC without stirring. The prepared product was denoted as MONTs-PLAX-bPSY for convenience. The successful C-C coupling reaction was confirmed by 13C NMR analysis. (Figure S3) The resonance peak near 137 ppm was the evidence of the substituted aromatic carbons, while the peak of 127 ppm was ascribed to unsubstituted aromatic carbons. Besides, the broad peak near 36 ppm was attributed to the methylene carbons from PS skeleton.28-29 Simultaneously, PLA could be quickly degraded in the presence of AlCl3 and HCl.30-31 The disappearance of the characteristic PLA carbonyl stretch peak at 1758 cm-1 in the FT-IR spectra after reaction further confirmed the complete removal of PLA, while the peak at 1600 cm-1, 1500 cm-1, 1450 cm-1 ascribed to the vibrations of aromatic rings still remained (Figure S4). Meantime, the appearance of a new peak at 1690 cm-1 is assigned to hindered vibrations of carbon–carbon bonds in rigid framework.32 The existing characterization confirmed that the PS


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block has been successfully hyper-crosslinked based on Scholl reaction accompanied by the removal of degradable PLA block.

Scheme 1. (A) Schematic illustration of preparation of MONTs and MCNTs and (B) the typical Scholl cross-coupling reaction. The morphology of MONTs-PLA156-b-PS250 was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Figure 1A revealed that the hollow worm-liked nanotube networks with average 25 nm diameters and 9 nm thickness of wall can be observed. Especially, the open-end structure of nanotubes labeled with white circles in the TEM image is also found, which is very important to facilitate the mass transfer of the guest molecules through MONTs.The SEM image (Figure S5) also showed that the worm-liked rods with average diameter of 25 nm accumulate together, which is deeply consistent with TEM result. Importantly, the structure control of the methodology can be directly confirmed by the fact that the MONTs with different diameter at about 29 nm and 32 nm can be prepared by using different precursors of PLA60-b-PS65 and PLA265-b-PS250, respectively (Figure S6).


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Figure 1. The TEM image (A) and N2 adsorption-desorption isotherms (B) of MONTs-PLA156b-PS250 (the inset is the pore size distribution (PSD) curve).


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Table 1. Pore structure parameters of samples SBETa

Smicrob

Vmicroc

Vtotd

(m2g-1)

(m2g-1)

(m3g-1)

(m3g-1)

MONTs-PLA60-b-PS60

448

179

0.08

0.69

MONTs-PLA156-b-PS250

559

213

0.10

0.87

MONTs-PLA265-b-PS250

582

102

0.07

0.94

Samples

a) BET specific surface area from N2 adsorption; b) Microporous surface area calculated from tplots; c) DFT micropore volume; d)Total pore volume (p/p0=0.995). The textural information of the prepared MONTs-PLA156-b-PS250 was detected by nitrogen sorption measurement. As shown in Figure 1B, the distinct increase at low relative pressure in the adsorption isotherm and a pronounced hysteresis loop at high relative pressure in the desorption isotherm both indicate the present of microporous and mesoporous structure. There is no adsorption plateau appearing at high relative pressure in the isotherm, which indicates the existence of macropores. The Brunauer–Emmett–Teller (BET) surface area for MONTs-PLA156b-PS250 can reach 559 m2g-1, and the T-plot method gives the microporous area of 213 m2g-1 and micropore volume of 0.1 m3g-1 (Table 1). Calculated by density functional theory (DFT), the pore size distribution (PSD) curve shows that the size of micropore and mesopore has a maximum at about 1.3 and 5.3 nm, respectively (Figure 1B). The micropore fraction is originated from hyper-crosslinked PS wall, while the meso/macropores are resulted from the hollow tubular nanostructure and loose aggregation of nanotubes. Moreover, the MONTs-PLA60b-PS65 and MONTs-PLA265-b-PS250 also showed the similar BET surface area and PSD (Figure S6).


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Figure 2.TEM images of MONTs-PLA156-b-PS250 prepared by different time (A) 1h, (B) 6h, (C) 12h and (D) 24h.

Although the detailed formation mechanism of tubular structure was not extremely clear at present stage, inspired by our previous work,24 a “nucleation-to-growth” process was proposed to interpret the formation of the tubular nanostructure based on the hyper-crosslinking mediated self-assemble strategy. We speculated that the formation of hollow nanospheres can be referred as a nucleation process. The nucleation will occur at the beginning of hyper-crosslinking reaction, and then followed by growing in single or splitting direction to form single or branched nanotubes. In order to prove our hypothesis, the different reaction conditions had been explored to study the formation mechanism of tubular nanostructure. Firstly, the formation process of the tubular structure was monitored through the time-dependent experiments. As shown in Figure 2, in the initial first hour, hollow nanospheres were produced with uniform size accompanied by the presence of hollow rod structure with a short length. Notably, this initial state is similar to our


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previous work and also undergoes a hyper-crosslinking mediated self-assemble process. As time goes on, the hollow nanospheres gradually disappeared while lots of tubular nanostructure emerged in TEM images. The whole nucleation-to-growth process can be accomplished after about 12 h due to the exhaustion of free diblock copolymers that had not participated in nucleation process (hollow nanospheres). According to our hypothesis, the formation of hollow nanospheres would be also originated from the self-assembly behavior of PLA156-b-PS250 diblock copolymer in CHCl3 after acidified by extra HCl gas, which can be proved by dynamic lighting scattering (DLS) experiments. The DLS results show that a new strong peak of 142 nm with low size distribution appears after acidified by HCl gas except for the peak of PLA156-b-PS250 diblock copolymer unimer-micelle (Rh ≈ 10nm) (Figure S7), which means that a part of PLA156-b-PS250 unimer-micelle can take part in the nucleation process through self-assembled behavior, while a considerable amount of residual free PLA156-b-PS250 unimer-micelle in CHCl3 will be used as raw materials for the subsequent growth of nanotubes. Besides, we also found that the concentration of copolymer precursors had a great influence on the formation of nanotubes structure (Figure S8). For example, no nanotube could be obtained when the concentration was low to 1 mg/ml, which mainly because self-assembly process could not occur to form “nucleus” in this low concentration (Figure S8A). However, most of PLA156-b-PS250 unimer-micelle might tend to nucleate in a high concentration up to 20 mg/ml, which would directly result into scarcity of free unimer-micelle for the nucleation-to-growth process. Thus, only hollow nanospheres could be observed (Figure S8D). Interestingly, the experiment results proved that stirring was bad for the formation of MONTs, which means that the nucleation-to-growth was gradually conducted on the static environment (Figure S9C). What’s more, it was demonstrated that accelerating the nucleation process will be in favor of the formation of MONTs. For example,


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raising reaction temperature from 60 oC to 90 oC or purging with extra HCl gas as the promoter for self-assembling can both improve the regulation of the obtained MONTs rather than irregular chaotic structure (Figure S9A, B and D). As another controlled experiment, individual PS and PLA polymer were mixed to hyper-crosslinking. The chaotic structure was observed from TEM image (Figure S10), which demonstrated that molecular structure of PLA-b-PS diblock copolymer was another critical factor to the nucleation-to-growth process. Recently, MOPs have been recommended as emerging and cost-effective adsorbents for water treatment and air purification based on their high surface area and hierarchically porous structure. In addition, phenols are usually recognized as a kind of toxic substrates in industrial sewage. In this regard, the adsorption ability of MONTs for p-cresol from water was evaluated with different initial concentration (C0).The adsorption experiment was conducted by stirring the obtained MONTs in p-cresol aqueous solution for 1 day. When the adsorption equilibrium (Ceq) was achieved, the adsorbed amount (W) and adsorption efficiency (E) could be monitored and calculated from UV-vis spectra. As shown in Table 2, the adsorbed amount of MONTs-PLA156b-PS250 for p-cresol gradually increased with the growth of C0, while the corresponding adsorption efficiency decreased on the contrary. For example, the adsorbed amount (W) could reach to 670 mg g-1 even though the adsorption efficiency (E) was just as low as 45% for MONTs-PLA156-b-PS250 at C0=16 mgml-1. However, it is worth noting that the adsorption efficiency (E) could amazingly keep up above 91% at relatively low C0 below 1mgml-1 and get to 94% even at C0= 0.06 mgml-1. Actually, the most important thing is that the Ceq can be achieved after stirring over 5 min according to the adsorption kinetic experiment at C0= 8 mgml-1 (Figure S11). Besides, the prepared MONTs could be easily reused after simply washed by methanol and the adsorbed amount did not decrease even after 5 cycles (Figure S12). The


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prepared MONTs have impressive adsorption capacity, especially outstanding adsorption efficiency, for p-cresol compared to the recent reports,22, 33-36 and the outstanding performance might be attributed to the high surface area, open-ended nanotube structure and hydrophobic interactions between the p-cresol and the organic matrix. Next, we also performed the adsorption experiments of the MONTs for common organic vapors including toluene, methanol, dichloromethane, ethyl acetate, hexane and acetone, and water was used as a contrast. As shown in Figure 3, the adsorption capacities of the MONTs-PLA156-b-PS250 toward the six organic vapors at room temperature and at saturation vapor pressures are 1.19, 1.22, 2.18, 1.51, 1.80 and 1.11 gg-1, respectively. While MONTs-PLA156-b-PS250 only exhibited a low adsorption capacity of about 0.33 gg-1 for water vapor. Similarly, the reusability of the MONTs-PLA156-b-PS250 can be performed by removing the adsorbed organic vapor under vacuum. Utilizing toluene as a typical example, we found that the MONTs-PLA156-b-PS250 exhibited no significant loss of adsorption capacity over five cycles (Figure S13). The excellent adsorption performance of MONTs-PLA156-b-PS250 for organic vapors could be attributed to their hydrophobic organic frameworks and the hierarchically porous structure, which can potentially be used to clean poison solvents or gas in the field of water pollution and air-purifying respirator. Table 2. The adsorbed amount (W) and efficiency (E) of MONTs-PLA156-b-PS250 for p-cresol in different initial concentrations (C0). C0(mg/ml)

0.06

0.25

1

4

8

16

W (mg/g)

6

24

91

254

392

670

E (%)

94

95

91

64

49

45


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Figure 3. The adsorption capacities of MONTs-PLA156-b-PS250 toward six different organic vapors and water at room temperature and at saturation vapor pressures.

Owing to the rigid and conjugated structure, the obtained MONTs-PLA156-b-PS250 shows the good thermostability and has a yield of up to about 62 wt% even at 800 oC according to analysis of thermogravimetric analysis (TGA) (Figure S14). In fact, microporous carbon nanotubes (MCNTs) can be produced by simply pyrolyzing the prepared MONTs-PLA156-b-PS250 at 900oC with a heating rate of 2 oC/min under N2. TEM and SEM images showed that the obtained MCNTs-PLA156-b-PS250 have the hollow tubular morphology inherited from the precursor with the diameter of ~ 23 nm and wall thickness of ~ 7 nm (Figure 4A and S15). Compared to MONTs-PLA156-b-PS250 precursors, both the diameter and wall thickness of MCNTs-PLA156-bPS250 have a slight decrease because of framework shrinkage after carbonization. The XRD


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pattern of MCNTs-PLA156-b-PS250 shows two broad and low-intensity diffraction peaks (002) and (100) at 23.4o and 43.9o, respectively, indicating the presence of amorphous carbon (Figure S16). Raman spectrum also showed that MONTs-PLA156-b-PS250 has two characteristic peaks at about 1327 and 1587 cm-1, which are assigned to D(disorder) mode and G (graphitic) mode, respectively (Figure S17). The ID/IG intensity ratio ofMCNTs-PLA156-b-PS250 can reach to 1.22, demonstrating the generation of a large amount of defects, which is a strong evidence of the presence of micropores.37-39 Moreover, the high temperature treatment can prominently enhance the porosity. Therefore, the obtained MCNTs-PLA156-b-PS250 have a larger BET surface area of 1448 m2g-1, especially for microporous area of 908 m2g-1, compared to MONTs-PLA156-b-PS250 (Figure S18). Benefitting from the high BET surface area, the resultant MCNTs-PLA156-b-PS250 could be expected to possess the good electrochemical performance. As shown in Figure 4, the cyclic voltammetry (CV) curves exhibit nearly rectangular shapes and have no significant change even in the sweep rate arrange from 20 to 200 mV/s, which indicates the outstanding electrochemical capacitive performances of MCNTs-PLA156-b-PS250. Also, this excellent property is further confirmed by the galvanostatic charge−discharge curves that show the typical triangular profiles. In addition, the specific capacitance of MCNTs-PLA156-b-PS250 is 192 F g-1 at 0.5 A g-1 with a decrease to 133 F g-1 while 20 times increase of the current density. Even though the specific capacitance is not the highest but still better than some reported carbon materials such as MWCNT, Graphite oxide (GO), carbon aerogel and other porous carbons (Table S1). Besides, MCNTs-PLA156-b-PS250 exhibit very high cycle stability with capacitance retention of 97% at a current density of 10 A g-1 even after 5000 cycles. These excellent electrochemical performances mainly benefit from the unique microporous tubular nanostructure and high surface area. The abundant micropores in the carbon nanotube wall provide tremendous active


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sites to adsorb a large number of electrolyte irons for enhanced capacitance while the unique tubular frameworks can significantly decrease the ion diffusion length for fast charging and discharging.

Figure 4. (A)TEM image, (B) CV curves at different sweep rates and (C) galvanostatic charge discharge curves under various current densities for MCNTs-PLA156-b-PS250; (D) long-term cycle stability over 5000 cycles of at current density MCNTs-PLA156-b-PS250 of 10 A g−1.

4. Conclusions In conclusion, we developed a novel method for the preparation of microporous organic nanotubes (MONTs) based on Scholl coupling reaction using PLA-b-PS diblock copolymers as precursor. The fabricated MONTs have a high surface area, rigid crosslinking architecture and a hierarchically porous structure. What’s more, the product we synthesized not only shows an outstanding adsorbed capacity at high concentration and high adsorption efficiency at low


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concentration for p-cresol, but also displays excellent adsorption capacity for six different organic vapors at saturated vapor pressure. Furthermore, the MCNTs can be directly prepared by simple carbonization of MONTs and exhibit excellent electrochemical performance as electrode materials of supercapacitor. We hope that our methodology not only promote the development of MOPs with unique micro-structure, but also provide a new application direction of Scholl reaction and create a new class of MOPs for application including of water treatment, air purification and energy storage. Supporting Information. The Supporting Information is available free of charge on the ACS Publications website. GPC characterization, 1H NMR spectrum, Solid state

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C NMR spectrum, FT-IR spectra, TEM

images, SEM images, adsorption data, TGA data, XRD pattern, Raman analysis, N2 adsorptiondesorption isotherms, and pore size distributions. Corresponding Author * E-mail:[email protected]. Notes The authors declare no competing financial interest.

Acknowledgment The work is supported by National Natural Science Foundation of China grant 21574042, 51273066, Supported by large instruments Open Foundation of East China Normal University. References


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Scheme 1. (A) Schematic illustration of preparation of MONTs and MCNTs and (B) the typical Scholl crosscoupling reaction. 62x27mm (300 x 300 DPI)


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Figure 1. The TEM image (A) and N2 adsorption-desorption isotherms (B) of MONTs-PLA156-b-PS250 (the inset is the pore size distribution (PSD) curve). 36x53mm (300 x 300 DPI)



Figure 2.TEM images of MONTs-PLA156-b-PS250 prepared by different time (A)1h, (B) 6h, (C) 12h and (D) 24h. 16x11mm (300 x 300 DPI)


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Figure 3. The adsorption capacities of MONTs-PLA156-b-PS250 toward six different organic vapors and water at room temperature and at saturation vapor pressures. 289x200mm (150 x 150 DPI)



Figure 4. (A)TEM image, (B) CV curves at different sweep rates and (C) galvanostatic charge -discharge curves under various current densities for MCNTs-PLA156-b-PS250; (D) long-term cycle stability over 5000 cycles of at current density MCNTs-PLA156-b-PS250 of 10 A g−1. 18x13mm (300 x 300 DPI)


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37x22mm (300 x 300 DPI)


Construction of Microporous Organic Nanotubes Based on Scholl

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