linked polymers New Insights into carbon dioxide ... · New Insights into carbon dioxide interactions with benzimidazole-linked polymers Suha Altarawneh1, S. Behera2, Puru Jena2 and

Electronic Supporting Information

New Insights into carbon dioxide interactions with benzimidazole-linked polymers

Suha Altarawneh1, S. Behera2, Puru Jena2 and Hani M. El-Kaderi*1

Department of Chemistry, Department of Physics, Virginia Commonwealth University, Richmond, VA 23284-2006, USA. E-mail: [email protected]; Fax: +1 804 828 8599; Tel: +1

804 828 7505

Table of Contents

Section S1:

Section S2:

DFT modeling and CO2 interaction with BILPs

Synthesis of aryl-aldehyde and the BILPs

Section S3: Characterization of BILPs

TGA (Thermal gravimetric analysis)

Scanning Electron Microscopy Imaging (SEM)

XRD-pattern for BILPs

FT-IR Spectroscopy of Starting Materials and BILPs

Solid-state 13C CP-MAS NMR spectra for BILPs

Section S4: Low-Pressure (0 – 1.0 bar) Gas Adsorption Measurements for BILPs

Electronic Supplementary Material (ESI) for ChemComm.This journal is © The Royal Society of Chemistry 2014

Section S1: Computational Method for CO2 interaction with BILPs

Benzimidazole-linked polymers, BILP-15 and BILP-14, were modeled by their corresponding

benzimidzole-containing units biphenylimidazole (BILP-15) and benzimidazole (BILP-14) to

ease the computational demand. The binding affinities, Eb per CO2 were calculated by

determining the equilibrium geometries and corresponding total energies of these complexes.

We define Eb as,

Eb = {E[BILP-15@nCO2] – E[BILP-15] – n*E[CO2]}/n and

Eb = {E[BILP-14@nCO2] – E[BILP-14] – n*E[CO2]}/n; for n = 2,4

Where, E[BILP-15@nCO2] and E[BILP-14@nCO2] are the total energies of BILP-15 and BILP-

14 interacting with n number of CO2 molecules. E[BILP-15], E[BILP-14] and E[CO2] are the

total energies of BILP-15, BILP-14 and the CO2 molecule respectively.

2

Figure S1. CO2 interactions with BILP-14

(a)

(b)

(c)

3

Figure S2. CO2 interactions with BILP-15(a)

(b)

(c)

4

Section S2: Synthesis of the aryl-aldehyde and BILPs.

Synthesis of 1,2,4,5-Tetrakis-(4-formylphenyl)benzene (TFPB)

A mixture of 1,2,4,5-Tetrabromobenzene (1.5 g, 3.85 mmol), 4-formylphenylboronic acid (3.4 g,

22.7 mmol), palladium tetrakis(triphenylphosphine) (0.12 g, 0.10 mmol, 5.2 mol%), and

potassium carbonate (4.2 g, 30.4 mmol) in dry 1,4-Dioxane (50 mL) was stirred under nitrogen

for 3 days at 90 °C. The white suspension reaction mixture was poured into a slurry ice

containing 80 mL concentrated hydrochloric acid. The solid product was filtered and washed

with water and 2 M HCl three times. The final product was obtained after extraction of the crude

product with chloroform (4 × 50 mL). The extracted organic layer was dried over MgSO4,

filtered and evaporated under reduced pressure. The resultant solid was recrystallized from hot

ethylacetate to afford (TFPB) as a yellowish powder (1.3 g, 68%). Anal. Calcd for C34H22O4: C,

82.58%; H, 4.48%; O, 12.94% Found: C, 82.27%; H, 4.59%; O, 13.00%. 1H NMR (300 MHz,

CDCl3, δ (ppm)): (s, 4H, formyl H), (s, 4H, Ar H), (d, 8H, Ar H) and (d, 8H, Ar H).13C NMR

(CDCl3, 75 MHz) δ (ppm) 191.0, 146.0, 140.0, 136.0, 133.0, 130.0, 131.0.

Synthesis of BILP-14.

A 100 ml Schlenk flask was charged with (60 mg, 0.211 mmol) of 1,2,4,5-Benzenetetramine

tetrahydrochloride salt and 30 mL of anhydrous DMF. The solution was cooled to around -30

°C and a solution of 1,2,4,5-tetrakis(4-formylphenyl)benzene (50 mg, 0.10 mmol) in 25 mL

anhydrous DMF was added dropwise to the pervious charged solution. Temperature was

maintained around -30 °C until yellowish brown solid product formation completed and then

raised to RT and kept for overnight. The flask containing the reaction mixture was flashed with

air for 15 minutes and capped. The reaction

5

mixture was then heated in an oven at 130 °C (0.5 °C/min) for 3 days to afford a fluffy

brownish polymer which was isolated by filtration over a glass frit. The product was immersed

in DMF (20 ml overnight) and then in (20 ml) acetone. The product was dried under vacuum at

120 °C and 1.0 x 10-5 Torr for 20 hours to give BILP-14 as a brown fluffy solid (56 mg, 73%).

Anal. Calcd for C46H26N8.4H2O: C, 72.44%; H, 3.41%; N, 14.70 %. Found: C, 71.82%; H,

4.98%; N, 13.11%.

Synthesis of BILP-15.

This polymer was synthesized according to the polymerization conditions mentioned for BILP-

14 above using 3,3’-Diaminobenzidine tetrahydrochloride hydrate (65 mg, 0.181 mmol) and

1,2,4,5-tetrakis(4-formylphenyl)benzene (40 mg, 0.081 mmol). The 3,3’-Diaminobenzidine

tetrahydrochloride hydrate was used in excess due to the presence of 10% hydrate in the

building block. After activation the final product BILP-15 was obtained as a brownish fluffy

solid (60 mg, 81%). Anal. Calcd for C58H34N8.4H2O: C, 76.15%; H, 4.60%; N, 12.25%. Found:

C, 75.90%; H, 4.66%; N, 12.60%.

6

Section 3: Characterization of BILPs

Characterizations of aryl-aldehyde starting material and BILPs.

1H and 13C NMR spectral characterization of starting building units

Figure S3. 1H NMR for 1,2,4,5-tetrakis(4-formylphenyl)benzene (TFPB) in CDCl3.

7

a

bcd

O

O

O

OHC

OHC

CHO

CHO

ab

cd

Figure S4. 13C-NMR for 1,2,4,5-tetrakis(4-formylphenyl)benzene (TFPB) in CDCl3.

8

OHC

OHC

CHO

CHO

abc

d

f eg

Figure S5: SEM images of BILP-14 (A) and BILP-15 (B).

The samples were prepared by dispersing the material onto a sticky carbon surface attached to a flat aluminum sample holder. The samples were then coated with platinum at 1x10-5 mbar of pressure in a nitrogen atmosphere for 90 seconds before imaging. Images were taken on a Hitachi SU-70 Scanning Electron Microscope.

9

A

B

Figure S6: Thermal gravimetric profiles of BILP-14 and BILP-15,measured under N2. Thermogravimetric analysis (TGA) was carried out using a TA Instruments Q-5000IR series thermal gravimetric analyzer with samples held in 50 μL platinum pans under inert N2 air (heating rate 5 °C/min ).

10

0 100 200 300 400 500 60020

30

40

50

60

70

80

90

100

110

W

t %

Temparature oC

BILP-14 BILP-15

Figure S7: FT-IR spectra of BILP-14 and BILP-15 and their aryl-aldehydes starting building units.

The region from 2000-400 cm-1 is expanded to show the characteristic vibrations of imidazole ring and the consumption of the aldehyde C=O functional group. The vibrations at 1620, 1480 and 1435 cm-1 are attributed to the skeleton of the imidazole ring. The vibration band at 1700 cm-

1is corresponds to the carbonyl of the aldehyde building block, which disappeared completely upon condensation. The stretching at around 3425 cm-1 and 3220 cm-1 are assigned to free N-H and hydrogen bonded N-H or O-H respectively. The new band at 1640 cm-1 band is due to the N-H bending and the bands ranging from 2750-3030 cm-1 are due to aromatic CH stretching.

11

4500 4000 3500 3000 2500 2000 1500 1000 500

Wavenumber (cm-1)

TPFB BILP-14 BILP-15

2000 1500 1000 500

Wavenumber (cm-1)

TPFB BILP-14 BILP-15

Figure S8: Solid-state 13C CP-MAS NMR spectra of BILP-14 and BILP-15.

13C cross-polarization magic angle spinning (CP-MAS) NMR spectra for solid samples were

taken at Spectral Data Services, Inc. Spectra were obtained with samples on a Tecmag-based

NMR spectrometer, operating at a H-1 frequency of 363 MHz, using a contact time of 1 ms and a

delay of three seconds for the CPMAS experiment; samples were spun at 7.0 kHz

12

250 200 150 100 50 0

N

NH

12 3 456

78

N

HN

BILP-14

ppm

1

2345

67

8

250 200 150 100 50 0

N

NH

1

23

4 5 6

78

9

10 N

HN

1112

ppm

BILP-15

1

2, 3

4567

8, 910, 11

12

Figure S9: XRD profiles for BILP-14 and BILP-15 show the amorphous pattern of the polymers.

Powder X-ray diffraction data were collected on a Panalytical X’pert pro multipurpose diffractometer (MPD). Samples were mounted on a sample holder and measured using Cu Kα radiation with a 2θ range of 1.5-35.

13

5 10 15 20 25 30 35

2 Theta

BILP-14 BILP-15

Section 3: Low-Pressure (0 – 1.0 bar) Gas Adsorption Measurements for BILPs.

Activation of BILPs for gas adsorption measurements: A sample was loaded into a 9 mm

large bulb cell (from Quantachrome) of known weight and then hooked up to MasterPrep. The

sample was degassed at 120 °C for 20 hours. The degassed sample was weighed precisely and

then transferred back to the analyzer. The temperatures for adsorption measurements was

controlled by using refrigerated bath of liquid nitrogen (77 K) or liquid argon (87 K), and

temperature controlled water bath (273 K and 298 K). Adsorption measurements were performed

on an Autosorb-1 C (Quantachrome) volumetric analyzer using adsorbates of UHP grade.

14

Figure S10: Pore Size Distribution calculated from the Ar adsorption isotherms by the Non-

Local Density Functional Theory (NLDFT) method using a cylindrical pore model. The filled

symbols are adsorption points and the empty symbols are desorption points.

15

0 5 10 15 20 25 30 35 40 45 50 550.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

dV (w

)(cc/

A0 /g)

Pore Width / A0

BILP-14

0 5 10 15 20 25 30 35 40 45 50 55 600.00

0.02

0.04

0.06

0.08

0.10

dV (w

)(cc/A

0 /g)

Pore Width / A0

BILP-15

Figure S11: Experimental Ar adsorption isotherm (filled circles) for BILP-14, BILP-15 measured at 87 K. The calculated NLDFT isotherm is overlaid as open circle and the BET plots for BILP-14, BILP-15 calculated from the Ar adsorption isotherm at 87 K. The model was applied from P/Po = 0.05-0.16. The correlation factor is indicated. (W = Weight of gas absorbed at a relative pressure P/Po).

16

0.0 0.2 0.4 0.6 0.8 1.00

50

100

150

200

250

300

Original Fitted

Fitting error = 0.15 % Upta

ke (c

c/g)

P/P

BILP-15Ar uptake at 87K

0.0 0.2 0.4 0.6 0.8 1.00

100

200

300

400

500

Original Fitted

Fitting error =0.144 % Upta

ke (c

c/g)

P/P

BILP-14Ar uptake at 87K

0.04 0.06 0.08 0.10 0.12 0.14 0.16

0.10

0.15

0.20

0.25

0.30

0.35

1/(W

((Po/

P)-1

))

P/P0

BILP-14Ar at 87 KSABET=1005 m2/gR2=0.999685

0.04 0.06 0.08 0.10 0.12 0.14 0.16

0.2

0.3

0.4

0.5

0.6

0.7 BILP-15

Ar at 87 K AS BET = 448 m2/gR2 = 0.999994

1/ (W

((P0/P

)-1)

P/P0

Figure S12: Methane and Carbon dioxide uptake isotherms for BILP-14 and BILP-15 at 273 K, 288 K and 298 K. Adsorption filled, desorption (empty).

17

0.0 0.2 0.4 0.6 0.8 1.00

2040

6080

100120

140

160180

BILP-14 298 K BILP-15 298 K BILP-14 288 K BILP-15 288 K

BILP-14 273 K BILP-15 273 K

CO2 u

ptak

e (m

g/g)

P ( bar)

CO2 uptake isotherms

0.0 0.2 0.4 0.6 0.8 1.00

5

10

15

20

25

BILP-14 273 K BILP-15 273 K BILP-14 298 K BILP-15 298 K BILP-14 288 K BILP-15 288 K

CH4 u

ptak

e (m

g/g)

P ( bar)

CH4 uptake isotherms

Figure S13: Virial analysis of CH4 and CO2 adsorption data at 273, 298, and 288 K for BILP-14 and BILP-15.

18

0.0 0.5 1.0 1.5 2.0 2.5 3.0-2-1012345678

CO2 at 273 K CO2 at 298 K CO2 at 288 K Fitting

lnP

n (mmol g-1)

BILP-15

0.0 0.2 0.4 0.6 0.8 1.0 1.21

2

3

4

5

6

7

CH4 at 273 K CH4 at 298 K CH4 at 288 K Fitting

lnP

n (mmol g-1)

BILP-14

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0-2-1012345678

CO2 at 273 K CO2 at 298 K CO2 at 288 K Fitting

lnP

n (mmol g-1)

BILP-14

0.0 0.3 0.6 0.91

2

3

4

5

6

7

8

CH4 at 273 K CH4 at 298 K CH4 at 288 K Fitting

lnP

n (mmol g-1)

BILP-15

Figure S14: Adsorption selectivity of CO2 over N2 and CH4 for BILP-14 and BILP-15 from initial slope calculations.

19

0.00 0.02 0.04 0.06 0.08 0.100.0

0.1

0.2

0.3

0.4

0.5

CO2 ; 20.0 x -0.0 N2 ; 0.3 x - 0.0 CH4: 2.06x -.0.0

Upta

ke (m

mol

/g)

P (bar)

BILP-14 273 K

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.160.00

0.05

0.10

0.15

0.20

0.25

CO2 : 7.38x -0.0 N2 : 0.15x -0.0 CH4 : 0.915x - 0.0

Upta

ke (m

mol

/g)

P (bar)

BILP-14 298 K

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

CO2: 13.19x +0.003 N2 : 0.15x -0.0 CH4: 1.4621x -0.0126

Upta

ke (m

mol

/g)

P (bar)

BILP-15 273 K

0.00 0.02 0.04 0.06 0.08 0.10

0.00

0.02

0.04

0.06

0.08

0.10

0.12

CO2: 4.837x + 0.05482 N2 : 0.083x - 0.00 CH4 : 0.59x + 0.00788

Upta

ke (m

mol

/g)

P (bar)

BILP-15 298 K

Ideal adsorbed solution theory

The pure component isotherms of CO2 measured at 273 and 298 K were fitted with the dual-site Langmuir (DSL) model

𝑞 = 𝑞𝐴 + 𝑞𝐵 = 𝑞𝑠𝑎𝑡,𝐴𝑏𝐴𝑝

1 + 𝑏𝐴𝑝 + 𝑞𝑠𝑎𝑡,𝐵𝑏𝐵𝑝

1 + 𝑏𝐵𝑝

with T-dependent parameters and 𝑏𝐴 𝑏𝐵

𝑏𝐴 = 𝑏𝐴0 𝑒𝑥𝑝(𝐸𝐴𝑅𝑇), 𝑏𝐵 = 𝑏𝐵0 𝑒𝑥𝑝(𝐸𝐵

𝑅𝑇)where, is molar loading of adsorbate (mol kg-1), is saturation loading (mol kg-1) , is 𝑞 𝑞𝑠𝑎𝑡 𝑏parameter in the pure component Langmuir isotherm (Pa-1), is bulk gas phase pressure (Pa), 𝑝 ‒ 𝐸is heat of adsorption (J mol-1), is ideal gas constant (8.314 J mol-1 K-1), is absolute 𝑅 𝑇temperature (K), subscripts and refers to site and site , respectively.𝐴 𝐵 𝐴 𝐵

Since the pure component isotherms of CH4 and N2 do not show any inflection characteristic they were fitted with the single-site Langmuir (SSL) model

𝑞 = 𝑞𝑠𝑎𝑡,𝐴𝑏𝐴𝑝

1 + 𝑏𝐴𝑝

with T-dependent parameter 𝑏𝐴

𝑏𝐴 = 𝑏𝐴0 𝑒𝑥𝑝(𝐸𝐴𝑅𝑇)

Pure-component isotherm fitting parameters were then used for calculating Ideal Adsorbed Solution Theory (IAST)1 binary-gas adsorption selectivities, , defined as 𝑆𝑎𝑑𝑠

𝑆𝑎𝑑𝑠 =𝑞1 𝑞2𝑝1 𝑝2

20

Figure S15: IAST selectivities of CO2/ CH4 for 50/50 (A), and CO2/ N2 10/90 (B) binary mixtures at 298 K for BILP-14 and BILP-15.

Table 1S. Initial slope selectivity of BILP-14 and BILP-15 at 273 K (298 K), and the IAST selectivity of BILP-14 and BILP-15 at 298 K for the binary mixtures of (CO2/N2: 10:90) and (CO2/CH4: 50:50).

SelectivityInitial slope at 273 K(298 K) IAST at 298 K

BILP CO2/N2 CO2/CH4 CO2/N2 (10:90)

CO2/CH4(50:50)

BILP-14 56 (49) 10 (9) 52 8.6BILP-15 83 (63) 9 (8) 56 8.3

21

0.0 0.2 0.4 0.6 0.8 1.02

4

6

8

10

12CO2/CH4: 50/50 at 298 K (A)

BILP-15 BILP-14

Sele

ctiv

ity

P( bar)

0.0 0.2 0.4 0.6 0.8 1.010

20

30

40

50

60

70CO2/N2 : 10/90 at 298 K (B)

BILP-14 BILP-15

Sele

ctiv

ity

P (bar)