Supporting Information

Amorphous-to-Crystalline Transformation toward

Controllable Synthesis of Fibrous Covalent Organic

Frameworks Enabling Promotion of Proton Transport

Weifu Kong,† Wei Jia,† Rong Wang, Yifan Gong, Changchun Wang, Peiyi Wu, Jia Guo*

State Key Laboratory of Molecular Engineering of Polymers, Department of

Macromolecular Science, Fudan University, Shanghai 200433, P. R. China

†These authors contributed equally.

*E-mail: guojia@fudan.edu.cn

Electronic Supplementary Material (ESI) for ChemComm.This journal is © The Royal Society of Chemistry 2018

1. Materials and methods

1.1 Materials

All starting materials and solvents were purchased from commercial sources and used

without further purification. Phloroglucinol was obtained from Adamas. Trimethyl 1,3,5-

benzenetricarboxylate was obtained from J&K Scientific. Benzidine (BD), 3,3'-

dimethoxybenzidine, anhydrous o-dichlorobenzene and n-butyl alcohol were purchased

from Aladdin. Acetic acid and acetone were purchased from Sinopharm Chemical Reagent

Co., Ltd. Nafion solution (5 wt%) was obtained from Dow-DuPont. 2,4,6-

triformylphloroglucinol (Tp) and 1,3,5-triformylbenzene (Tf) were synthesized according

to the procedures described in the literature.[1,2] Graphene oxide nanosheets were prepared

by the reported method.[3]

1.2 Synthesis of fibrous COFs

COF fibers were prepared by the two-step method of structural transformation as described

here. Typically, Tp (16.8 mg, 0.08 mmol) was dissolved in 15 mL of anhydrous ethanol,

and the solution was refluxed under magnetic stirring followed by the dropwise addition of

BD (22.1mg, 0.12mmol) in ethanol (3 mL) at rate of 12 mL/h. The reaction was allowed to

proceed for 24h. Afterwards, the solvent was removed by rotary evaporator to obtain the

yellow product PAMs. Next, PAM solids were transferred into a Pyrex tube with the mixed

solvent of o-DCB and n-butanol (0.9 mL/0.1mL). The 6M acetic acid (0.1 mL) was added

as catalyst. After three freeze-pump-thaw cycles, the tube was sealed off and the reaction

was kept at 120oC for 3d. The product was collected by filtration, washed with acetone and

dried at 45 oC under vacuum. The COF(TfBD) fibers were prepared under otherwise

identical conditions based on the monomers of Tf and BD.

1.3 Synthesis of spherical COFs

The spherical COF(TpBD) was prepared by the modified two-step method. Tp (16.8 mg,

0.08 mmol) and BD (22.1mg, 0.12mmol) were dissolved in 18 mL anhydrous ethanol, and

the solution was heated to reflux for 24 h under magnetic stirring. The yellow powders

were obtained by removing the solvent with rotary evaporator. Then the PAM solids were

transferred into a Pyrex tube with the mixed solvent of o-DCB and n-butanol (0.9

mL/0.1mL). The 6M acetic acid (0.1 mL) was added as catalyst. After three freeze-pump-

thaw cycles, the tube was sealed off and the reaction was allowed to proceed at 120 oC for

3 days. The products were collected by filtration, washed with acetone and dried at 45 oC

under vacuum.

1.4 Preparation of COF@Nafion/GO membranes

5 mg of COFs were dispersed in 30 mL of water and mixed with 1 mL of 5 wt.% Nafion

aqueous solution and 60 mL of 0.5 mg/mL GO dispersion. The mixture was treated with

ultrasonic for 0.5h and let stand for another 0.5h. Then the aqueous suspension was filtrated

to form the membrane under the pressure of 0.1 Mpa. After that, the membrane was peeled

off from the substrate and processed by 1 mol/L sulfuric acid at 80 oC for 2h to obtain the

resultant COF@Nafion/GO membrane.

1.5 Proton conduction measurement

The proton conductivity (σ) tests of the membranes were conducted under various

temperature and humidity conditions. The impedance spectra were collected on a CHI660E

electrochemical workstation with a four-electrode method. The temperature and humidity

were controlled via a temperature and humidity test chamber. The proton conductivity σ

was figured out with the following formula:

(1)𝜎=

𝐿𝑅𝑊𝑑

where L is the length of the proton exchange membrane between two reference electrodes;

R is the impedance of the proton exchange membrane, which is obtained from the

impedance spectra; W is the width of the proton exchange membrane; d is the thickness of

the proton exchange membrane.

1.6 Characterization

The morphology of the as-prepared samples were collected by high-resolution transmission

electron microscope (HR TEM, JEOL 2100F, Japan) and field emission scanning electron

microscope (FESEM, Ultra 55 Zeiss, Germany). Powder X-ray diffraction spectra (PXRD,

Bruker D8 Advance, Germany) were recorded with Cu-Ka radiation to characterize the

crystal phase structure. N2 isotherms were obtained at 77K using a TriStar II 3020

instrument. The samples were degassed at 120°C for 24 h before measurement. The

specific surface area was simulated by Brunauer-Emmett-Teller (BET) model and pore size

distribution was simulated by nonlocal density functional theory (NLDFT).

[1] J. H. Chong, M. Sauer, B. O. Patrick, M. J. MacLachlan, Org. Lett., 2003, 5, 3823.

[2] M. P. Castaldi, S. E. Gibson, M. Rudd, A. J. P. White, Chem. Eur. J., 2006, 12, 138.

[3] R. Cruz-Silva, A. Morelos-Gomez, H. Kim, H. Jang, F. Tristan, S. Vega-Diaz, L. P.

Rajukumar, A. L. Elías, N. Perea-Lopez, J. Suhr, M. Endo, M. Terrones, ACS Nano 2014, 8,

5959.

Figure S1. (a) TEM image of the fibrous PAM(TpBD) with the magnified view and (b)

statistic number of fiber’s width measured in the image (a).

Figure S2. TEM images of spherical PAM(TpBD) (a) and imine-linked COF(TpBD) (b)

synthesized by the two-step strategy of amorphous-to-crystalline transformation.

Figure S3. HR TEM images of the fibrous-COF(TpBD) (a) and the fibrous-COF(TfBD)

(b), respectively.

Figure S4. SEM image of the irregular COF(TpBD) solids synthesized by a direct

solvothermal route.

Figure S5. SEM images of the fibrous-COF[TfBD(OMe)2] (a) and the fibrous-

COF[TpBD(OMe)2] (b), respectively.

Figure S6. FT IR spectra of the fibrous-COF(TpBD) and the parent COF(TpBD) synthesized by a

direct solvothermal route. Through the comparison, there is no any difference between two

samples.

Figure S7. Solid-state 13C NMR spectrum of the fibrous-COF(TpBD).

Figure S8. TGA curves of the fibrous-COF(TpBD) and the parent COF(TpBD)

synthesized by a direct solvothermal route.

Figure S9. PXRD pattern of the COF(TpBD) synthesized by a direct solvothermal route.

Figure S10. PXRD patterns of fibrous and spherical COF(TpBD)s measured at 25oC and at 100oC,

respectively.

Figure S11. Pore-size distributions of fibrous COF(TpBD) and COF(TfBD), respectively.

Figure S12. Photographs of the repeated flexing membranes: (a) the intact fibrous-

COF(TpBD)@Nafion/GO membrane and (b) the broken Nafion/GO membrane; and as

immersed in water for over 3 days, (c) fibrous-COF(TpBD)@Nafion/GO membrane have

reserved well and (d) Nafion/GO membrane have been dissolved partially.

Figure S13. Arrhenius plots of the proton conductivity for the fibrous-

COF(TfBD)@Nafion/GO membrane and the Nafion membrane with increase of

measurement temperature from 40oC to 80oC at 40% RH of humidity.

Figure S14. Nyquist plot of the fibrous-COF(TfBD)@Nafion/GO membrane.

Figure S15. TEM image shows that the fibrous PAM(TpBD) can be etched by the aqueous

solution of Nafion.

Table S1. Surface areas and pore volumes of PAMs and COFs.

Sample SBET (m2/g) Smicro (m2/g) Sext (m2/g) Pore volume (cm3/g)

Fibrous-PAM(TpBD) 3.8 / / /

Spherical-COF(TpBD) 782 638 144 0.248

Fibrous-COF(TpBD) 295 185 110 0.072

Fibrous-COF(TfBD) 134 71 63 0.027

Fibrous-COF[TpBD(OMe)2] 163 84 79 0.033

Fibrous-COF[TfBD(OMe)2] 89 52 37 0.019

Table S2. Comparison of the proton conduction performances of the fibrous-COF-containing membranes with those of the reported COF systems under hydrous condition.

Sample Temperature (oC) Humidity (%)Proton Conductivity

(S/cm)Ref.

PA@Tp-Azo 60 98 9.9 ×10−4 [S1]

PA@TpBpy-MC 100 97 2.5 × 10−3 [S2]

EB-COF:PW12 25 97 3.32 × 10-3 [S3]

NUS-10(R)

@PVDF-5080 97 0.0158 [S4]

Nafion 80 95 0.13 This work

Fibrous-COF(TfBD)

@Nafion/GO80 95 0.30 This work

[S1] S. Chandra; T. Kundu, S. Kandambeth, R. BabaRao, Y. Marathe, S. Kunjir, R.

Banerjee, J. Am. Chem. Soc., 2014, 136, 6570.

[S2] D.B. Shinde, H.B. Aiyappa, M. Bhadra, B.P. Biswal, P. Wadge, S. Kandambeth, B.

Garai, T. Kundu, S. Kurungot, R. Banerjee, J. Mater. Chem. A, 2016, 4, 2682.

[S3] H. Ma, B. Liu, B. Li, L. Zhang, Y.-G. Li, H.-Q. Tan, H.-Y. Zang, G. Zhu, J. Am.

Chem. Soc. 2016, 138, 5897.

[S4] Y. Peng, G. Xu, Z. Hu, Y. Cheng, C. Chi, D. Yuan, H. Cheng, D. Zhao, ACS Appl.

Mater. Interfaces, 2016, 8, 18505.