Separation of CO 2 from CH 4 using Mixed-Ligand Metal-Organic Frameworks

Transcription

1 Langmuir Supporting Information Separation of CO 2 from CH 4 using Mixed-Ligand Metal-Organic Frameworks Youn-Sang Bae, Karen L. Mulfort, %, Houston Frost, Patrick Ryan, Sudeep Punnathanam, Linda J. Broadbelt, Joseph T. Hupp, *,% and Randall Q. Snurr *, Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL " Department of Chemistry, Northwestern University, Evanston, IL Chemistry Division, Argonne National Laboratory, Argonne, IL 60439

2 Measurement of adsorption isotherms using a volumetric apparatus A volumetric-type apparatus (Figure S1) was used to measure the adsorption equilibria of CO 2 and CH 4 in 1-C and 1-M at 296 K and 0-18 atm. It was composed of an injection side, a sample side, a vacuum pump, and a pressure transducer. Both sides and all the lines were located in an environmental chamber to maintain a constant temperature. The volumes of the injection and sample sides were measured by He gas. Equilibrium pressures were measured with an MKS Baratron transducer 627B (accuracy ±0.12%). The pressure change was monitored in real time using LabVIEW software (version 7.1). After an adsorbate in the injection side was stabilized at constant T and P, the adsorbate was supplied from the injection side to the sample side. Then, the adsorption isotherms were measured by the stepwise pressure change. Figure S1. A high-pressure volumetric apparatus for the measurements of the adsorption isotherms at room temperature. Since the closed system consisted of an adsorbent and an adsorbate at a constant volume, the sum of the moles of adsorbate in the adsorbent and the gas phase was constant during each step. Hence, the adsorbed amounts per unit adsorbent mass were calculated by the mass balance for a pure gas in the injection and sample sides (equation S1) incorporated with the generalized virial-coefficient correlation (equation S2) [Bae and Lee, Carbon (2005) 43, 95]: PV zrt Moles of gas in the injection side before valve open + PV zrt Moles of gas in the sample side before valve open = PV zrt Moles of gas in the total system after valve open + M Mass of adsorbent q (S1) z P Pr = ) 1 (S2) T r 1 + (0.083 ) + ( T T r r Tr r The volumetric apparatus was tested to be leak-free using He gas. In addition, the accuracy of the system was proved by measuring CO 2 adsorption on NaY zeolite (CBV 100, Zeolyst), where the expected adsorption is known from prior reports in the literature.

3 Characterization Figure S2. Thermogravimetric analysis for (a) 1-C and (b) 1-M comparing as-synthesized and evacuated samples.

4 Figure S3. SEM images of (a) 1-C and (b) 1-M.

5 Figure S4. BET plots for (a) 1-C and (b) 1-M in the chosen range ( ). This range was chosen according to two major criteria established in Stud. Surf. Sci. Catal. 2007, 160,49-56 and J. Am. Chem. Soc., 2007, 129, : (1) The pressure range selected should have values of W(P 0 - P) increasing with P/P 0. (2) The y intercept of the linear region must be positive to yield a meaningful value of the c parameter, which should be greater than zero.

6 Figure S5. D-R plots for N 2 isotherms at 77K in (a) 1-C and (b) 1-M.

7 Volume adsorbed [cm 3 /g] C' 1-M' 0 1e-7 1e-6 1e-5 1e-4 1e-3 1e-2 1e-1 1e+0 P/P 0 Figure S6. Log-plot versions of N 2 isotherms at 77K in 1-C and 1-M. These plots show clearly that the micropores fill at very low relative pressures.

8 Table S1. Total pore volumes of 1-Cand 1-Mcalculated at various pressure points. P / P o pore volume (cm 3 /g) 1-C M

9 Isotherm Fitting Table S2. The R 2 values of several model fits for the pure isotherms of CO 2 and CH 4 in 1-C. Fitting models # of parameters R 2 (CH 4 isotherm) R 2 (CO 2 isotherm) Langmuir LF Toth Dual-Langmuir Dual-LF Table S3. The R 2 values of several model fits for the pure isotherms of CO 2 and CH 4 in 1-M. Fitting models # of parameters R 2 (CH 4 isotherm) R 2 (CO 2 isotherm) Langmuir LF Toth Dual-Langmuir Dual-LF

10 Table S4. The R 2 values of several model fits for the pure GCMC simulated isotherms of CO 2 and CH 4 in 1. Fitting models # of parameters R 2 (CH 4 isotherm) R 2 (CO 2 isotherm) Langmuir LF Toth Dual-Langmuir Dual-LF

11 Potential parameters for the GCMC simulations DPNI: Table S5. Atomic partial charges in the DPNI linker and zinc (unit of e) Nitrogen 1 Carbon 1 Hydrogen 1 Carbon 2 Hydrogen 2 Carbon 3 Nitrogen Carbon 4 Oxygen 1 Carbon 5 Carbon 6 Carbon 7 Hydrogen 3 Zinc (corner)

12 NDC: Table S6. Atomic partial charges in the NDC linker (unit of e) Oxygen 1 Carbon 1 Carbon 2 Carbon 3 Hydrogen Carbon 4 Hydrogen 2 Carbon 5 Carbon 6 Hydrogen

13 Table S7. Parameters for the gas molecules P Q (nm) Table S8. DREIDING parameters for the framework P Q (nm)