S1

Supporting Information

Covalent Organic Framework based Microspheres as

Anode Material for Rechargeable Sodium Batteries

Bidhan Chandra Patra, a Sabuj Kanti Das, b, ‡ Arnab Ghosh,c, ‡ Anish Raj K, c, ‡ Parikshit

Moitra,d Matthew Addicoat,e Sagar Mitra,*, c Asim Bhaumik, *, b Santanu Bhattacharya *, a

and Anirban Pradhan *, a

aDirector’s Research Unit, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, INDIA. E-mail: msap5@iacs.res.in (A.P.), director@iacs.res.in (S.B.)bDepartment of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, INDIA. E-mail: msab@iacs.res.in (A.B.)cDepartment of Energy Science and engineering, Indian Institute of Technology, Bombay, Powai, Mumbai, Maharashtra 400076, INDIA. E-mail: sagar.mitra@iitb.ac.in (S.M.)dTechnical Research Centre, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, INDIA.eSchool of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham, NG11 8NS, UK.

Section Content

Section S1 General information

Section S2 Synthesis and characterization of TFPB-TAPT COF

Section S3 Computational details of powder X-ray diffraction for TFPB-TAPT COF

Section S4 SEM image and TGA plot of TFPB-TAPT COF

Section S5 Calculation of theoretical specific capacity for TFPB-TAPT COF

Section S6 Ex-situ HRTEM analyses of electrode materials after cycling

Section S7 Calculation of sodium-ion diffusion coefficient

Section S7 Performance of TFPB-TAPT COF anode in lithium batteries

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

S2

Section S1: General information

FT-IR spectra of the synthesized samples were recorded using a Nicolet MAGNA-FT IR 750

Spectrometer Series II. Solid state 13C CP MAS NMR spectrum of TFPB-TAPT was

recorded in a 500 MHz BrukerAvance III spectrometer at a MAS frequency of 10 kHz. X-

Ray diffraction patterns of the powder samples were obtained with a Bruker AXS D-8

Advanced SWAX diffractometer using Cu-K (0.15406 nm) radiation. The N2

adsorption/desorption isotherms of the sample was recorded using an Autosorb 1C

(Quantachrome, USA) at 77 K. The sample was first degassed at 120 oC for overnight and set

for measurement. Pore size distribution (PSD) was calculated by using NLDFT considering

the carbon/slit-cylindrical pore model. Scanning electron microscopic analysis was performed

with a JEOL JEM 6700F field-emission scanning electron microscope (FESEM). High

resolution Transmission electron microscopy (HR-TEM) images of the synthesized polymer

were obtained using a JEOL JEM 2010 transmission electron microscope operated at 200 kV.

The sample was dispersed in isopropanol and drop casted on the copper grid TEM window.

X-ray photoelectron spectroscopy (XPS) was performed on an Omicron nanotech operated at

15 kV and 20 mA. Thermal analyzer TA-SDT Q-600 was used for thermogravimetric (TG)

by heating the samples from room temperature to 800 oC with a heating rate of 10 oC min-1

under N2 atmosphere.

S3

Section S2: Synthesis and characterization of TFPB-TAPT COF

Synthesis of 1, 3, 5-tris (4-formyl phenyl) benzene (TFPB)

Br

Br Br

CHO

B(OH)2

CHO

CHOOHC

Pd(PPh3)4, 10mol%Na2CO3(15 eqv),

Tolune+EtOH+H2O(6:2:1)90 oc, 48hr

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.09.510.010.511.0f1 (ppm)

6.01

3.03

6.00

2.98

7.26

7.87

7.89

7.91

8.02

8.04

10.1

0

CHO

CHOOHC

7.857.907.958.008.058.10f1 (ppm)

6.00

2.98

6.03

7.87

7.89

7.91

8.02

8.04

Figure S1. 1H NMR of 1, 3, 5-tris (4 formyl phenyl) benzene (TFPB).

S4

0102030405060708090100110120130140150160170180190200f1 (ppm)

76.9

177

.16

77.4

2

126.

6212

8.13

130.

58

135.

94

141.

75

146.

44

191.

86

CHO

CHOOHC

Figure S2. 13C NMR of 1, 3, 5-tris (4 formyl phenyl) benzene (TFPB).

S5

Synthesis of 2, 4, 6-tris (4-aminophenyl)-1, 3, 5-triazine (TAPT)

CN

N

N

N

NH2

NH2H2N

TFA

0 oc to RT, 18hr

NH2

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.09.510.0f1 (ppm)

5.98

6.07

6.03

2.48

3.33

5.87

6.65

6.67

8.31

8.33

6.06.57.07.58.08.5f1 (ppm)

5.87

6.65

6.67

8.31

8.33

N

N

N

NH2

NH2H2N

Figure S3. 1H NMR of 2, 4, 6-tris (4-aminophenyl)-1, 3, 5-triazine (TAPT).

S6

0102030405060708090100110120130140150160170180190200f1 (ppm)

39.0

039

.16

39.3

339

.50

39.6

639

.83

40.0

0

113.

08

122.

94

130.

08

152.

90

169.

55

N

N

N

NH2

NH2H2N

Figure S4. 13C NMR of 2, 4, 6-tris (4-aminophenyl)-1, 3, 5-triazine (TAPT).

S7

Section S3: Computational details of powder X-ray diffraction for TFPB-

TAPT COF

Table S1. For the normal stacking structures

Interlayer

distance

(Å)

Total

Energy

(kcal/mole)

LJ energy

(a.u.)

Per layer

stabilization

(kcal/mole)

HOMO-

LUMO gap

(eV)

Monolayer -107.674677 0.4732 2.518

AA 3.49 -215.548056 0.7351 -62.34 2.179

SlipAA-x 3.56 -215.578028 0.7238 -71.75 2.474

SlipAA-xy 3.60 -215.576896 0.7217 -71.39 2.359

AB 3.12 -215.4608188 0.8367 -34.97 2.266

Slipp AA-x Slipp AA-xy

a b

Figure S5. Structure of Slipped AA-x and Slipped AA-xy of TFPB-TAPT COF.

S8

HOMO LUMO

Figure S6. HOMO-LUMO diagram of TFPB-TAPT COF.

Table S2. For the reverse stacked structures

Interlayer

distance

(Å)

Total Energy

(kcal/mole)

LJ

energy

(a.u.)

Per layer

stabilization

(kcal/mole)

HOMO-

LUMO gap

(eV)

Monolayer -107.674677 0.4732 2.518

AA 3.48 -215.554517 0.7351 -64.37 2.236

SlipAA-x 3.37 -215.561999 0.7344 -66.72 2.345

SlipAA-xy 3.54 -215.573835 0.7294 -70.43 2.414

AB 3.06 - 215.4563012 0.8404 -33.56 2.459

S9

Reverse AA Reverse AB

Rev. Slipp AA-x Rev. Slipp AA-xy

a b

c d

Figure S7. Crystal structure of TFPB-TAPT COF at different reverse mode.

Table S3. Fractional atomic coordinates for the unit cell of TFPB-TAPT

TFPB-TAPT; Triclinic; P1

a = 25.789001Å; b = 25.7835Å; c = 7.20107 Å

α = 77.628182, β = 90.907426, γ = 61.193553

Atom list x y zC1C2C3C4C5C6H1H2H3C7

0.869230.904910.881440.820440.782960.808130.951920.802190.779030.71788

0.271570.299220.358960.392320.367020.30640.274460.438160.286270.40487

0.984160.984120.006860.02410.017077.4E-40.961280.049550.998890.02024

S10

C8C9C10H4C11H5C12H6H7C13C14C15C16H8C17H9C18H10H11C19C20C21C22H12C23H13C24H14H15C25H16C26H17N1N2C27C28C29C30H18C31H19

0.683010.688570.621430.704280.627090.713790.592240.595190.605520.920270.897780.980550.933820.851440.016490.999740.993730.915550.063120.895710.859750.958290.884890.810890.983610.988460.947330.855450.032440.973470.940720.031410.076670.012360.030670.058270.027350.121480.059020.978240.152880.14581

0.379520.468330.415860.330490.504690.489770.479110.395040.55390.386390.44960.350220.475680.478990.376370.300810.439580.524980.347180.207330.182870.167530.121610.211940.10660.183780.082180.104060.076660.017720.001340.467120.43650.523860.983050.921020.889870.887980.827880.913830.825950.91182

0.101190.933760.093380.173990.926170.865620.004340.156940.855460.013230.935240.098750.944150.862880.109680.161840.032970.8820.179720.97030.92610.006530.92360.891298.1E-40.044110.961140.889380.030710.959310.943030.047310.136240.965010.975580.975790.946810.008160.953020.918430.013150.03131

S11

C32H20H21C33C34C35N3N4N5C36C37C38C39H22C40H23C41H24H25C42C43C44C45H26C46H27C47H28H29N6C48H30C49C50C51C52C53C54H31H32H33C55

0.122030.034870.202070.153650.240010.149160.120130.213760.209030.114

0.141830.052170.109320.189860.019140.030220.047570.131660.971170.305660.333690.34150.395620.305860.40350.320070.431370.416910.430570.493550.527280.508740.882530.918250.894130.832520.795190.820820.966080.813630.791470.72976

0.794910.803750.800730.729340.63940.643090.702770.698930.610240.612140.551110.642730.52090.527360.613130.690410.55140.473750.636930.603860.542220.630060.507670.52160.596010.677890.534370.459910.617040.497220.518190.567070.27820.305640.366250.40036

3/80.313970.279830.446850.294360.41309

0.986090.93060.039640.989147.8E-40.977670.976970.002630.987930.970280.955520.981340.955240.943290.979540.992860.970420.938870.992020.014120.005250.03830.020260.985890.051850.048060.0410.010330.07580.058270.987120.902970.490160.49530.510610.518660.508210.496370.483270.539290.489290.50396

S12

C56C57C58H34C59H35C60H36H37C61C62C63C64H38C65H39C66H40H41C67C68C69C70H42C71H43C72H44H45C73H46C74H47N7N8C75C76C77C78H48C79H49

0.694520.700640.632920.715490.639030.726170.604040.606390.617620.932810.910730.992640.946680.864740.028650.011320.006310.928610.074990.909270.873440.97190.898680.82450.997310.002130.961160.869250.046190.987340.954620.044070.088970.025530.044530.072050.04110.135270.072710.99199

1/60.15965

0.387760.476460.424180.33870.51290.497820.487430.403520.562070.393830.456760.358130.482980.485890.384310.309120.447230.532080.355390.21360.188710.173950.127540.217360.113010.190350.088390.109850.083290.024070.007670.474790.44450.531170.989520.927490.896330.894430.834360.92030.832380.91827

0.581250.416190.571670.653160.405670.349990.483050.633520.334630.518130.435710.608240.444180.360350.6170.677220.535570.378860.689910.479570.438090.514340.434550.405990.508640.550120.469590.401610.537240.465950.449690.548550.639960.46290.481050.481140.452840.513150.458870.42490.518350.53589

S13

C80H50H51C81C82C83N9N10N11C84C85C86C87H52C88H53C89H54H55C90C91C92C93H56C94H57C95H58H59N12C96H60

0.135720.048530.215830.167290.253520.162660.133730.227380.222510.12740.155180.065490.122550.203260.032370.043570.060780.144820.984360.319160.347170.354890.409030.319360.41680.333460.444530.430380.44390.506590.539070.51943

0.801380.810250.807170.735880.646

0.649820.709390.70550.616930.619080.558130.649870.528090.534330.62040.697550.558680.4810.64430.610420.548620.636880.514270.527760.603170.684740.541570.466430.62450.505180.52620.57452

0.491480.436680.544520.493580.503860.48040.481150.506060.490460.471120.45570.480720.453850.444110.477770.492260.468460.437020.489440.517130.509950.538840.522550.493680.548650.548310.537620.513560.568550.549240.467380.37662

S14

Section S4: SEM image and TGA plot of TFPB-TAPT COF

Figure S8. (a, c) SEM image of the TFPB-TAPT COF before and after cycling, respectively.

(b) TGA plot of the TFPB-TAPT COF (d) C1s XPS spectrum of TFPB-TAPT COF after

cycling. (e) Long-term cycling performance of TFPB-TAPT COF in sodium batteries.

0 200 400 600 80030

45

60

75

90

105

Mas

s lo

ss (%

)

Temperature (oC)

282 284 286 288 290 292

289.

2

286

Binding energy (eV)

C 1s-Post analysis284

a b

c d

e

S15

Section S5: Calculation of theoretical specific capacity for TFPB-TAPT

COF

Theoretical specific capacity of the TFPB-TAPT electrode was calculated by the following

formula:1,2

Ct mA h g‒1 unit. =

𝐹 × 1000𝑀 × 3600

Where, Ct= theoretical capacity, F = Faraday constant and M = molecular weight per active site.

M =

𝑀𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 𝑝𝑒𝑟 𝑚𝑜𝑙𝑒𝑁𝑜 𝑜𝑓 𝑎𝑐𝑡𝑖𝑣𝑒 𝑠𝑖𝑡𝑒 𝑓𝑜𝑟 𝑠𝑜𝑑𝑖𝑢𝑚 𝑖𝑜𝑛 𝑎𝑑𝑠𝑜𝑟𝑝𝑡𝑖𝑜𝑛

Molecular weight of per unit TFPB-TAPT COF is 1380 g mol-1.

Thus, M = g (considering 1 Na+ /–C=N bond) 1380

12= 115

Hence, the theoretical specific capacity (Ct) is 233.05 mA h g-1.

CNH

a

b c d

Na

Figure S9. Side view (a) and top view (b) of one unit cell of the sodium ion inserted TFPB-

TAPT COF Crystal, HOMO (c) and LUMO (d) of the TFPB-TAPT COF after sodium ion

insertion.

S16

Section S6: Ex-situ TEM analyses of electrode materials after cycling

Figure S10. HRTEM images of electrode materials stopping the cells at different voltages

during initial discharge and subsequent charge processes.

S17

Section S7: Calculation of sodium-ion diffusion coefficient

Figure S11. GITT profiles of the TFPB-TAPT COF anode in sodium batteries. Each

discharge step is composed of 5 minutes of galvanostatic discharge at the current rate of 50

mA g–1, followed by 15 minutes of relaxation time.

From the GITT experiment ion-diffusion coefficient can be calculated using the following

equation:

................. Eq. 1𝐷 =

4𝜋𝜏

(𝑛𝑀𝑉𝑀

𝑆 )2(∆𝐸𝑠

∆𝐸𝑡)2

Where, τ is the duration of the current pulse (in seconds); nM and VM are the molar mass (mol)

and volume (cm3/mol) of the active material; S is area of the electrode (cm2); ΔEs is the

steady-state voltage change due to the current pulse and ΔEt is the voltage change during the

S18

constant current pulse, eliminating the iR drop. The TFPB-TAPT COF anode is consisted of

spherical particles of radius Rs. So, the Eq. 1 may be written as

.................. Eq. 2𝐷 =

4𝜋𝜏

(𝑅𝑠

3 )2(∆𝐸𝑠

∆𝐸𝑡)2

The GITT profile of the TFPB-TAPT COF anode during discharge is shown in Figure S11.

Each discharge step is composed of 5 minutes of galvanostatic discharge, followed by 15

minutes of relaxation time. The first two discharge steps are chosen to estimate the value of

ion-diffusion coefficient (Figure S11, inset). The values of ΔEs and ΔEt were estimated to be

8.1 mV and 63.3 mV. Now, we can calculate the diffusion coefficient putting the values of

each parameter in Eq. 2.

τ (duration of the current pulse) = 300 sec,

Rs (radius of COF microsphere) = 285 nm or 2.85 × 10–5 cm,

ΔEs (steady-state voltage change due to the current pulse) = 8.1 mV,

ΔEt (voltage change during the constant current pulse) = 63.3 mV.

Hence, D = 6.275 × 10–15 cm2 s–1.

Section S8: Performance of TFPB-TAPT COF anode in lithium batteries

Cell assembly and electrochemical characterization

To investigate the electrochemical performances of TFPB-TAPT COF with respect to

lithium, CR2016 coin cells were assembled using lithium metal as counter/reference

electrode. Celgard 2400 soaked with 40 μL of electrolyte comprised of 1 M LiPF6 in 1:1 (v/v)

mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) was used as separator.

Cyclic voltammetry (CV) study was carried out at a scan rate of 0.02 mV s−1 within the

potential window 0.001-3.0 V (vs Li+/Li).The charge-discharge experiments were carried out

within the potential range 0.05-2.6 V (vs Li+/Li) at different current rates. The capacities were

evaluated based on the mass of active material present in the electrode (i.e., 1.65 mg cm-2).

All the electrochemical measurements were carried out at the constant temperature of 20 °C.

S19

Results and discussion

TFPB-TAPT COF exhibited a very good reversible redox behaviour with respect to lithium,

as revealed by cyclic voltammetry experiment. Figure S12a represents the first scan of cyclic

voltammetry study of TFPB-TAPT in the voltage range of 0.001-3.0 V versus Li+/Li redox

system at 0.02 mV s-1 scan rate. During first cathodic scan, a sharp peak at 1.7 V and a broad

peak located at the potential zone of 0.5-1.5 V were obtained. These two peaks are associated

with successive two steps of Li+ ion insertion into TFPB-TAPT COF. However, the broad

peak at the lower potential is also accompanied by insertion of Li+ ion into conductive super

P carbon additive as well as decomposition of electrolyte to form stable solid electrolyte

interphase (SEI). On the reverse scan, three peaks were observed, an intense broad peak at

1.05 V, a weak peak at 1.95 V and an intense sharp peak at 2.35 V; all are related to Li+ ion

de-intercalation processes. However, during second cycle onwards, the nearly identical nature

of CV curves (Figure S12b) implies excellent Li+ ion storage reversibility of TFPB-TAPT

COF. Charge-discharge cycling performance of TFPB-TAPT COF at the current rate of 30

mA g-1 is shown in Figure S12c. An irreversible capacity contribution was observed during

first discharge. This irreversible capacity contribution could be attributed to the rapid

decomposition of electrolyte and formation of solid electrolyte interphase (SEI) at lower

potential as observed from the first scan of cyclic voltammetry. The TFPB-TAPT COF

exhibited an initial reversible discharge capacity of 398 mA h g-1 at 3rd cycle with a

coulombic efficiency of 98% and an as much as high specific discharge capacity of 365 mA h

g–1 (91.7% capacity retention) was observed after 50 cycles. Since the theoretical capacity of

TFPB-TAPT COF is 233 mA h g-1, at least 165 mA h g-1 of capacity contributed from the

reversible insertion of Li+ ion into super P carbon additive3,4. Figure S12d reveals the rate

performance of TFPB-TAPT COF at the different current rates of 30, 50, 100 and 200 mA g-

1, respectively. The observed capacities at different current rates were found to be extremely

stable.

S20

Figure S12. Electrochemical performances of TFPB-TAPT COF with respect to Li+/Li – (a)

First cycle CV scan at the scan rate of 0.02 mV s-1. (b) 2nd to 10th cycle CV scans at the scan

rate of 0.02 mV s-1. (c) Charge-discharge cycling performance at 30 mA g-1. (d) Rate

performance at the current rates of 30, 50, 100, and 200 mA g-1.

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