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1 Electronic Supplementary Information Pyrene-Directed Growth of Nanoporous Benzimidazole-Linked Nanofibers and their Application to Selective Capture and Separation Mohammad Gulam Rabbani, Ali Kemal Sekizkardes, Oussama M. El-Kadri, Bilal R. Kaafarani and Hani M. El-Kaderi* Mohammad Gulam Rabbani, Ali Kemal Sekizkardes, H. M. El-Kaderi* (Corresponding-Author) Department of Chemistry Virginia Commonwealth University 1001 W. Main St. Richmond, VA , US Tel.: (804) Prof. O. M. EL-Kadri Department of Biology, Chemistry, and Environmental Sciences Tel.: (971) American University of Sharjah PO Box 26666, Sharjah United Arab Emirates oelkadri@aus.edu Prof. B. R. Kaafarani Department of Chemistry American University of Beirut Beirut , Lebanon Tel.: (961) bilal.kaafarani@aub.edu.lb S1

2 Table of Contents Section S1 NMR Spectral Characterization of TFPPy 3 Section S2 Characterization of BILP-10 4 TGA Trace for BILP-10 4 PXRD Pattern for BILP-10 5 Scanning Electron Microscopy Imaging (SEM) 6 FT-IR Spectroscopy of Starting Materials and BILP-10 7 Solid-State 13 C CP-MAS NMR Spectrum for BILP-10 9 Section S3 Low Pressure (0 1.0 bar) Gas Adsorption Studies 10 Section S4 High-Pressure (0 40 bar) Gas Adsorption Studies 28 S2

3 Section S1: NMR Spectral Characterization of 1,3,6,8-tetrakis(4-formylphenyl)pyrene 1 H NMR spectra for 1,3,6,8-tetrakis(4-formylphenyl)pyrene (TFPPy) in CDCl 3 : Note that 13 C NMR spectrum could not be measured due to the low solubility of TFPPy. S3

4 Section S2: Characterization of BILP-10 Figure S1: TGA trace of BILP BILP Weigth (%) Temperature ( o C) S4

5 Figure S2: PXRD- pattern for BILP-10 indicating amorphous materials (degrees) S5

6 Figure S3: Scanning Electron Microscopy Imaging (SEM) for BILP μm S6

7 Figure S4: FT-IR spectra ( cm -1 ) of starting materials and BILP-10: 3412 cm -1 (N-H, free), 3205 cm -1 (N-H, hydrogen bonded), cm -1 (C-H), 1638 cm -1 (C=N), 1604 cm -1 (C=C), 1484 and 1435 cm -1 (benzimidazole ring), 1370 and 1275 cm -1 (C-N). TFPPy BTA BILP Wavenuber (cm -1 ) Wavenuber (cm -1 ) S7

8 Figure S5: 13 C NMR for 1,2,4,5-Benzenetetramine tetrahydrochloride (BTA) (in d 6 DMSO). H 2 N NH 2 a b NH 2 NH 2 4HCl S8

9 Figure S6: Solid state 13 C CP-MAS NMR spectrum of BILP-10. Asterisks denote spinning side bands H N N 1 10 N N H * * ppm S9

10 Section S3: Low-Pressure (0 1 bar) Gas Adsorption Measurements for BILP- 10 Low-pressure gas sorption experiments were performed for Ar, N 2, H 2, and CH 4. The surface properties, for example, surface areas, pore size distributions, pore volume etc. were evaluated from Ar (87 K) and N 2 (77 K) adsorption isotherms. Gas storage and selective adsorption properties were evaluated by measuring the adsorption isotherms for H 2 (77 K and 87 K), (273 K and 298 K), CH 4 (273 K and 298 K) and N 2 (273 K and 298 K). The binding affinity (isosteric heats of adsorption) for H 2,, and CH 4 was evaluated from singlecomponent adsorption isotherms using virial equation and/or Clausius-Clapeyron equation. Calculation of isosteric heats of adsorption for BILP-10 Virial Equation The virial equation was used to determine the binding affinity and isosteric heats of adsorption. The virial equation can be written in the form 1 N ln P A0 N A1 N A2 N.... (I) Where N is the amount adsorbed at pressure P and A 0, A 1, etc. are virial coefficients. A 0 is related to adsorbate-adsorbent interactions, whereas describes adsorbate-adsorbate interactions. Under condition of low surface coverage, the higher terms (A 2, etc.) in the virial equation can be neglected. A virial-type expression in the following form can also be used to fit the experimental isotherm data for a given material at different temperatures. 2 1 ln( P) ln( N) T m i0 a N i i n i0 b N i i (II) S10

11 Where N is the amount adsorbed at pressure P, T is the temperature, a i and b i are temperature independent empirical parameters, and m and n determine the number of terms required to adequately describe the isotherm. The resulting virial coefficients a 0 through a m can then be used to calculate the isosteric heats of adsorption as function of uptake: Q st R m i0 a i N i (III) Where R is the universal gas constant (8.314 J K -1 Mol -1 ) It follows that the zero-coverage isosteric heats of adsorption is given by Qst Ra 0 (IV) Isosteric heats of adsorption can also calculated from the Clausius-Clapeyron equation. 3 2 lnp Qst RT (V) T N Where T is the temperature, R is the universal gas constant and P is the pressure for given quantity of gas adsorbed (N). The temperature dependent experimental data are fit to model isotherms to obtain P for given N. Adsorption isotherms for and CH 4 collected at 273 K, 288 K and 298 K were fitted here using the Tóth equation. 4 Tóth equation has the advantage that it appears to satisfy both limits of the isotherm, at p 0 and p. It is given by, N N s * kp kp t1 t 1/t (VI) N = Gas adsorbed (mmol/g) at a given pressure N s = Gas adsorbed (mmol/g) at saturation P = Pressure (atm) k and t are constants. S11

12 Equation (VI) can be rearranged to the following form to calculate P for equation (V). P k 1 - N N s N N s t(vii)t1/ Q st was then obtained from the slope of ln(p) vs. 1/T plot in the following form of equation (V): ( lnp) N - st Q R1 T C (VIII) S12

13 Figure S7: N 2 adsorption isotherm for BILP-10 measured at 77K. The filled circles are adsorption points and the empty circles are desorption points BILP-10 N 2 uptake at 77K 400 Uptake (cc/g) P/P 0 S13

14 Figure S8: BET plot for BILP-10 calculated from the N 2 adsorption isotherm at 77 K. The model was applied from P/P 0 = The correlation factor is indicated. (W= Weight of gas absorbed at a relative pressure P/P 0 ). 1/[W(P/P 0 )-1] BILP-10 N 2 sorption SA BET = 832 m 2 /g R 2 = P/P 0 S14

15 Figure S9: Ar adsorption isotherm for BILP-10 measured at 87 K. The filled circles are adsorption points and the empty circles are desorption points BILP-10 Ar uptake at 87 K Uptake (cc/g) P/P 0 S15

16 Figure S10: BET plot for BILP-10 calculated from the Ar adsorption isotherm at 87 K. The model was applied from P/P 0 = The correlation factor is indicated. (W= Weight of gas absorbed at a relative pressure P/P 0 ) /[W(P/P 0 )-1] BILP-10 Ar sorption SA BET = 787 m 2 /g R 2 = P/P 0 S16

17 Figure S11: The Pore Size Distribution of BILP-10 was calculated from the Ar adsorption isotherm using oxygen (zeolite) model, spherical/cylindrical pore, NLDFT adsorption model (A) and from N 2 isotherm (B) using silica as adsorbent and cylindr./sphere. pore, NLDFT adsorption model. The use of N 2 to probe porosity leads to PSD ~12.6 Å and to a broad distribution of mesopores in the range of ~20 to 50 Å that contributes ~23% of the the cumulative pore volume. Pore Width (Mode) = 7.55 Å V(W) (cc/å/g) (A) Pore size dstribution from Ar isotherm Spherical/cylinderical pore NLDFT ads. model PSD = 7.6 Å Actual Fitting Error = % Cumul. Pore Volume (cc/g) Pore Volume = cc/g at P/P o = Pore Width (Å) V(W) (cc/å/g) (C) Pore size dstribution from N 2 isotherm Cylindr./sphere.pore, NLDFT ads. Model PSD = 12.6 Å Actual Fitting Error = % Pore Width (Å) Cumul. Pore Volume (cc/g) Pore Width (Mode) = 12.6 Å Pore Volume = cc/g at P/P o = 0.95 S17

18 Figure S12: Experimental Ar adsorption isotherm for BILP-10 measured at 87 K is shown as filled circle. The calculated NLDFT isotherm is overlaid as open circle. Note that a fitting error of less than 1% indicates the validity of using this method for assessing the porosity of BILP-10. The fitting error is indicated BILP-10 Ar uptake at 87 K Uptake (cc/g) Fitting Error = % Original Fitted P/P 0 S18

19 Figure S13: gas adsorption for BILP-10 at 273 K (A), 288 K (B), and 298 K (C). The continuous solid line corresponds to a Tóth isotherm fit to the experimental data. uptake (mmol/g) (A), at 273 K Expt. Fitting P (bar) uptake (mmol/g) (B), at 288 K Expt. Fitting P (bar) (C), at 298 K uptake (mmol/g) Expt. Fitting P (bar) S19

20 Figure S14: CH 4 gas adsorption for BILP-10 at 273 K (A), 288 K (B), and 298 K (C). The continuous solid line corresponds to a Tóth isotherm fit to the experimental data. CH 4 uptake (mmol/g) (A) CH 4, at 273 K Expt. Fitting P (bar) CH 4 uptake (mmol/g) (B) CH 4, at 288 K Expt. Fitting P (bar) (C) CH 4, at 298 K CH 4 uptake (mmol/g) Expt. Fitting P (bar) S20

21 Figure S15: Virial analysis of adsorption data (A) (circles: 273 K, squares: 298 K) and isosteric heats of adsorption (Q st ) (B) for BILP-10. a0 = , a1= , a2 = , a3 = , b0 = , b1 = Q st (kj/mole) (B) Q st for Q st from Virial method Q st from Clausius-Clapeyron equation uptake (mg/g) Q st for from Clausius-Clapeyron Equation: kj/mol Q st for from virial method: ~ kj/mol (0 ~ mg/g) S21

22 Figure S16: Virial analysis of H 2 adsorption data (A) (circles: 77 K, squares: 87 K) and isosteric heats of adsorption (Q st ) (B) for BILP-10. a0 = , a1= , a2 = , a3 = , a4 = , b0 = , b1 = , b2 = Q st (kj/mol) (B) Q st for H H 2 Uptake (mg/g) Q st for H 2 from virial method: 9.3 ~ 3.7 (0 ~ 15.8 mg/g) S22

23 Figure S17: Virial analysis of CH 4 adsorption data (A) (circles: 273 K, squares: 298 K) and isosteric heats of adsorption (Q st ) (B) for BILP-10. a0 = , a1= , a2 = , a3 = , b0 = , b1 = (B) Q st for CH Q st (kj/mol) Q st from Virial method Q st from Clausius-Clapeyron equation CH 4 uptake (mg/g) Q st for CH 4 from Clausius-Clapeyron Equation: kj/mol Q st for CH 4 from virial method: ~ (0 ~ 16.7 mg/g) S23

24 Figure S18: Proposed interaction sites of with imidazole moieties BILP-10. S24

25 Figure S19: Analysis of adsorption isotherms at 273 K and 298 K for BILP-10 using virial method (Equation I). At 273 K: A 0 = and A 1 = ; at 298 K: A 0 = and A 1 = ln(n/p) (ln(mol g -1 Pa -1 )) Expt. at 273 K Fitted at 273 K Expt. at 298 K Fitted at 298 K N (mol g -1 ) S25

26 Figure S20: Selective adsorption of over CH 4 and N 2 at 273 K and 298 K. Uptake (mmol/g) uptake CH 4 uptake N 2 uptake BILP-10, 273 K P (bar) Uptake (mmol/g) uptake CH 4 uptake N 2 uptake BILP-10, 298 K P (bar) S26

27 Figure S21: Adsorption selectivity of BILP-10 for over CH 4 and N 2 at 273 K and at 298 K from low-pressure data. Selectivity at 273 K: From initial slopes: S(CO /N ) 107 ; S CO / CH ) ( 2 4 From equation S = [q 1 /q 2 ]/[p 1 /p 2 ]: uptake at 0.15 bar = mmol/g N 2 uptake at 0.75 bar = mmol/g S CO / N ) 128 ( 2 2 uptake at 0.1 bar = mmol/g; CH 4 uptake at 1.9 bar = mmol/g S(CO 2/CH 4 ) 18 (It should be noted that CH 4 uptake at 1.9 bar was selected from high pressure experiment at 275 C and it was assumed that the data at 273 K and 275 K are very similar. Uptake (mmol/g) 0.24 BILP-10, Selectivity at 273 K , y = x CH 4, y = x N 2, y = x E P (bar) Selectivity at 298 K: From initial slopes: S CO / N ) 59 ; S CO / CH ) 7 ( 2 2 ( 2 4 From equation S = [q 1 /q 2 ]/[p 1 /p 2 ]: uptake at 0.15 bar = mmol/g N 2 uptake at 0.75 bar = mmol/g S CO / N ) 107 ( 2 2 Uptake (mmol/g) BILP-10, Selectivity at 298 K, y = x CH 4, y = x N 2, y = x E-5 uptake at 0.1 bar = mmol/g CH 4 uptake at 1.9 bar = mmol/g S(CO /CH ) P (bar) S27

28 Section S4: High-Pressure (0 40 bar) Gas Adsorption Measurements for BILP- 10. High pressure sorption isotherms were run using a VTI HPVA-100 volumetric analyzer. Ultrahigh purity helium (99.999%) was used to calibrate the free volume in the sample cell before each measurement. The skeletal density (d sk ) of BILP-10 was found in the course of analysis for appropriate density correction factorization. 5 High pressure data was collected using ultrahigh purity H 2 (99.999%), (99.99%) and CH 4 (99.999%) obtained from Airgas Inc. (Radnor, PA). Free space measurements were performed prior to data collection utilizing ultrahigh purity helium to establish the appropriate cold zone compensation factors. Absolute gas uptakes were calculated according to literature methods 6 using NIST Thermochemical Properties of Fluid Systems. 7 Bulk phase gas densities up to 40 bar were fit using a sixth-order polynomial, then multiplied by the pore volume obtained from the Ar isotherm. Although the surface excess adsorption and absolute adsorption are nearly identical under low pressure up to 1 bar, they are different under high pressure conditions because the void space of the pores of adsorbent can hold significant amount of compressed gas under high pressure. The absolute amount of adsorbed gas is then expressed as N abs = N exc + d gas V p Where N abs is the absolute adsorption in mg g -1 ; N exc is the excess adsorption which is experimentally measured; d gas is the density of the compressed gas at a given temperature and pressure in cm 3 g -1, 7 and V p is the pore volume in cm 3 g -1. The V p can be calculated from d sk and d bulk using the following expression 5 V p dsk d d d sk bulk bulk Where d sk is the skeletal density of the material obtained from He experiment and d bulk is the bulk density of the sample which is, typically, obtained from available crystallographic model. S28

29 Ideally, above calculated pore volume should be comparable to the pore volume obtained from low-pressure Ar or N 2 isotherms. However, they deviate each other in many cases even for crystalline materials due to the partial decomposition of crystals or the presence of any other impurities. 8 Consequently, it is more relevant to recalculate the d bulk, particularly for noncrystalline amorphous materials, using the experimental obtained V p and d sk. The volumetric density of adsorbed gas inside the sample can be obtained simply by multiplying the adsorbed quantity with the bulk density of the sample. N v = N g d bulk Where N v is the volumetric uptake in g L -1, and N g is the gravimetric uptake in mg g -1, and d bulk is the bulk density of the sample in g cm -3. S29

30 Figure S22: H 2 isotherms for BILP-10 measured at 77 (black) and 87 K (red). Circles and squares represent surface excess (N Exc ) and absolute adsorbed (N Abs ) amounts, respectively BILP-10, H 2 uptake at 77 K and 87 K 300 H 2 uptake (mg/g) N Exx at 77 K N Exc at 87 K N Abs at 77K N Abs at 87 K P (bar) H 2 uptake (v/v) S30

31 Figure S23: isotherms for BILP-10 measured at 275 (black) and 298 K (red). Circles and squares represent surface excess (N Exc ) and absolute adsorbed (N Abs ) amounts, respectively. uptake (mg/g) 1000 BILP-10, CO uptake at 275 K and 298 K N Exc at 275 K N Exc at 298 K 100 N Abs at 275K N Abs at 298 K P (bar) uptake (v/v) S31

32 Figure S24: CH 4 isotherms for BILP-10 measured at 275 (black) and 298 K (red). Circles and squares represent surface excess (N Exc ) and absolute adsorbed (N Abs ) amounts, respectively. CH 4 uptake (mg/g) 100 BILP-10, CH 90 4 uptake at 275 K and 298 K N Exc at 275 K N Exc at 298 K 10 N Abs at 275K N Abs at 298 K P (bar) CH 4 uptake (v/v) S32

33 High Pressure Gas Selectivity Studies Selectivity prediction using ideal adsorbed solution theory (IAST): Ideal adsorbed solution theory calculations were performed as has been previously reported. 9,10,11 According to Myers and Prausnitz, 9 the ideal adsorbed solution theory can be reduced to the mathematical integration: Py x 1 1 t0 2 x 2 Py F 1( t ) d lnt F ( t) d lnt In this equation, P is the total pressure, y i is the bulk phase molar ratio of gas i, x i is the adsorbed phase molar ratio of gas i, and the function, F i (t), is a fitting function for the pure component i based on the Langmuir-Freundlich model: t0 2 n a * b * p 1 b * p 1/c 1/c d * e * p 1 d * p 1/f 1/f In this equation, n is the gas uptake in mmol/g, p is the pressure in bar, and a, b, c, d, e, and f are the fitting parameters. Since x 1 = 1 x 2 and y 1 = 1 y 2, the integrated equation nets only three unknowns. Therefore, by specifying one value and varying a second, the third value can be calculated. Selectivity can then be calculated as: S 1,2 x1/y x /y S33

34 Figure S25: Pure component isotherms for (black circle), CH 4 (red square) and N 2 (blue diamond) at 298 K. The solid lines are the dual-site Langmuir-Freundlich fits for (black) CH 4 (red) and N 2 (blue). Gas uptake (mmol/g) expt CH 4 expt N 2 expt model CH 4 model N 2 model P (bar) S34

35 Figure S26: IAST selectivities of over CH 4 at 298 K, the low pressure region is expanded in the bottom figure. Selectivity ( /CH 4 ) Selectivity /CH 4, 298 K 8 Gas phase mole fraction ratios 6 for and CH : : : : : : P (bar) Selectvity ( /CH 4 ) 16 Selectivity 14 /CH 4, 298 K : : : : : : P (bar) S35

36 Figure S27: IAST selectivities of over N 2 at 298 K, low pressure region is expanded in the bottom figure. Selectivity ( /N 2 ) Selectivity /N 2, 298 K Gas phase mole fraction ratios for :N 2 0.5: : : : : : P (bar) Selectvity ( /N 2 ) Selectivity /N 2, 298 K 30 Gas phase mole fraction ratios for :N : : : : : : P (bar) S36

37 References 1. X. Zhao, S. Villar-Rodil, A. J. Fletcher and K. M. Thomas, J. Phys. Chem. B 2006, 110, J. L. C. Rowsell and O. M. Yaghi, J. Am. Chem. Soc., 2006, 128, P. Huanhua, J. A. Ritter and P. B. Balbuena, Langmuir 1998, 14, S. Tedds, A. Walton, D. P. Broom, and D. Book, Faraday Discuss., 2011, 151, M. Dincă, A. Dailly, Y. Liu, C. M. Brown, D. A. Neumann and J. Long, J. Am. Chem. Soc., 2006, 128, H. Furukawa, M. A. Miller and O. M. Yaghi, J. Mater. Chem., 2007, 17, NIST Chemistry WebBook (Thermophysical Properties of Fluid Systems): 8. H. Furukawa and O. M. Yaghi, J. Am. Chem. Soc., 2009, 131, A. L. Myers and J. M. Prausnitz, AIChE J., 1965, 11, Z. R. Herm, J. A. Swisher, B. Smit, R. Krishna and J. R. Long, J. Am. Chem. Soc., 2011, 133, T. E. Reich, S. Behera, K. T. Jackson, P. Jena and H. M. El-Kaderi, J. Mater. Chem., 2012, 22, S37