Supporting Information Core-Shell Type Ionic Liquid

Supporting Information Core-Shell Type Ionic Liquid-Metal Organic Framework Composite: An Exceptionally High CO 2/CH 4 Selectivity ∥

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Experimental SI-1

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Materials and Sample Preparation ZIF-8 (Basolite Z1200, 2-methylimidazole zinc salt), 1-(2-hydroxyethyl)-3-methylimidazolium dicyanamide ([HEMIM][DCA]), dimethylformamide (DMF) and acetone with the highest available purity available were obtained from Sigma-Aldrich and stored in an Ar-filled glovebox (Labconco). The composite sample was prepared by wet impregnation method. At first, ZIF-8 was activated by drying in a vacuum oven at 105 °C overnight to remove the moisture and other volatile impurities. To prepare the [HEMIM][DCA]/ZIF-8 composite, 0.4 g of [HEMIM][DCA] was first dissolved in approximately 30 mL of acetone and stirred for 1 h at room temperature followed by adding 0.6 g of activated ZIF-8 to the solution. The resultant mixture solution was continuously stirred for 6 h at 30 °C in an open atmosphere until the acetone was evaporated. The sample was dried overnight at 105 °C to remove any remaining solvent. 1 Washing Samples with DMF [HEMIM][DCA]/ZIF-8 was washed with 3 mL DMF at 50 °C three times and the filtrate was collected in a container. Approximately 100 mg of powder samples were used for washing. After washing the samples, the powder sample was dried in oven at 105 °C for two hours. Characterization X-ray Diffraction (XRD) The XRD pattern for ZIF-8 and [HEMIM][DCA]/ZIF-8 were obtained by a Bruker D8 advance X-ray Diffraction system with a Cu Kα1 radiation and wavelength 1.54 Å. The power rating of X-ray generator was set to 30 kV and 10 mA, and Lynxeye detector was used with a slit size of 1 mm. The diffraction patterns were obtained in the range of 2θ values of 5 to 45°, with a step size of 0.0204°. 2 SI-2

Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) The [HEMIM][DCA]/ZIF-8 sample was loaded onto a lacey carbon grid (SPI Supplies, lacey carbon coated 200 mesh copper grid), and examined by transmission electron microscopy. TEM images were obtained with an FEI Titan 80-300 kV Environmental Transmission Electron Microscope at Birck Nanotechnology Center, Purdue University. The microscope was equipped with a field emission gun and operated at 300 kV. The surface features and morphologies of the pristine ZIF-8 and composite samples were obtained by a Zeiss Ultra Plus field emission scanning electron microscope. For scanning the samples, a voltage of 2 kV was applied under vacuum while the working distance was adjusted to approximately 2.5 mm for each sample. Images were obtained at two different magnification (50 KX and 25 KX).1,3 Fourier Transform Infrared (FTIR) Spectroscopy The Fourier transform infrared spectra of the bulk IL, pristine ZIF-8, and composite samples were obtained by using a Thermo Scientific Nicolet iS50 model FTIR spectrometer with an attenuated total reflection cell. For background and sample measurements, the IR spectra were obtained in an absorbance mode between the range of 3200 to 400 cm -1 with 64 and 512 scans of background and sample scan, respectively, while the resolution was set to 2 cm -1. IR spectra peak assignments and deconvolution were performed using Fityk software.4 X-Ray Photoelectron Spectroscopy (XPS) Analysis XPS depth profile measurement of [HEMIM][DCA]/[ZIF-8] was performed by a Thermo Scientific K-Alpha spectrometer using an Aluminum anode (Al Kα= 1468.3 eV) at an electron take-off angle of 90° (between the sample surface and the axis of the analyzer lens). Depth profiling was done using 500 eV Ar-ion sputter beam. Powder sample was subjected to Ar-ion

SI-3

bombardment for 100 seconds in total to give 10 etching levels. The spectra were recorded using an Avantage 5.9 data system. The binding energy scale was calibrated by assigning the C 1s signal at 285 eV. Brunauer−Emmet−Teller (BET) Surface Area To determine the BET surface area, a Micromeritics ASAP 2020 physisorption analyzer was used. For each analysis, approximately 150 mg of sample was used. At first, the samples were activated at 125 °C under vacuum for overnight. After activation, free space measurement of samples was performed using He gas at 77 K. Volumetric adsorption of N 2 gas was obtained between 10-6 and 1 bar, and the pressure steps between 0.05 and 0.3 bar were fit to BET equation to estimate the surface areas of samples. The pore volume of the samples were derived using tplot method from N 2 adsorption isotherm measured at 77 K.1,2 Thermogravimetric Analysis (TGA) TGA was used to determine the thermal stability of the samples with a TA Instruments Q500 model thermogravimetric analyzer along with platinum pan. Approximately 15 mg of each sample was placed in the platinum pan after tarring the empty pan. At first, a constant heating rate of 5 °C/min was employed up to 120 °C followed by an isothermal treatment for 8 h at the same temperature. The temperature was then raised to 700 °C with a ramp rate of 2 °C/min under a continuous N 2 flow of 40 mL/min and 60 mL/min for balance and purge gases, respectively. The onset (Tonset) and derivative onset (T′onset) temperatures were determined from thermogravimetry (TG) and derivative gravimetric (DTG) curves for comparison of thermal decomposition temperatures. However, Tonset values generally overestimate the thermal decomposition temperature, therefore, in this study, we have considered to used (T′onset) values. 3

SI-4

Gas Adsorption Measurements

Adsorption isotherms of CO 2 and CH 4 were obtained for pristine ZIF-8 and composite samples with a Micromeritics (Particulate Systems) High-Pressure Volumetric Analyzer HPVA II-200. Approximately 400 mg of sample was weighed and loaded into a sample holder. Prior to the measurements, first, the sample was degassed at 125 °C under vacuum until the pressure reached to 10-6 bar. After the sample was degassed, the sample holder was connected to analysis port and the temperature was set to 25 °C. Before starting the measurements, all lines of the system were purged three times with He gas to clean and remove any unwanted residuals from previous experiment. The single-component gas adsorption isotherm of CO 2 and CH 4 were fitted to the dual-site Langmuir model. Ideal CO 2/CH 4 selectivities of the samples were calculated by dividing the CO 2 uptake values to the CH 4 uptake values at the same pressures. 1–3

Additional Data

SI-5

5

10

15

20

(044) (334) (244) (235)

(134)

(233)

(114)

(013) (222)

(022)

(002)

(112)

(011)

Normalized Intensity

ZIF-8 [HEMIM][DCA]/ZIF-8

25 30 2-Theta

Figure S1. XRD patterns of ZIF-8 and [HEMIM][DCA]/ZIF-8.

(a)

(b) SI-6

35

40

45

Figure S2. SEM images ZIF-8 (a and b) and [HEMIM][DCA]/ZIF-8 (c and d).

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ZIF-8 [HEMIM][DCA] [HEMIM][DCA]/ZIF-8

Normalized intensity

2132

2200

2126

2180

2160

2140

2120

2100

2080

-1

Normalized intensity

Wavenumber (cm )

1800

1600

1400

1200

1000

800

600

400

-1

Wavenumber (cm ) Figure S3. FTIR spectra of ZIF-8, bulk [HEMIM][DCA], and [HEMIM][DCA]/ZIF-8.

SI-8

(b)

Absorbance

Absorbance

(a)

ZIF-8 [HEMIM][DCA] Unwashed [HEMIM][DCA]/ZIF-8 Water washed [HEMIM][DCA]/ZIF-8

1600

1400

1200

1000

800

600

400

3200

3000

-1

2800

2600

2400

2200

2000

1800

-1

Wavenumber (cm )

Wavenumber (cm )

(c)

(d)

Absorbance

Absorbance

Water [HEMIM][DCA] FILTRATE

1600

1400

1200

1000

800

600

400

3200

-1

3000

2800

2600

2400

2200

2000

1800

-1

Wavenumber (cm )

Wavenumber (cm )

Figure S4. FTIR spectra of ZIF-8, bulk [HEMIM][DCA], and [HEMIM][DCA]/ZIF-8 prior and after washing with water in two different regions (400-1600 cm -1 and 1800-3200 cm -1): (a and b) Powder samples before and after washing with water, (c and d) filtrate (liquid samples).

SI-9

(b)

Absorbance

Absorbance

(a)

ZIF-8 [HEMIM][DCA] Unwashed [HEMIM][DCA]/ZIF-8 Toluene washed [HEMIM][DCA]/ZIF-8

1600

1400

1200

1000

800

600

400

3200

3000

-1

2800

2600

2400

2200

2000

1800

-1

Wavenumber (cm )

Wavenumber (cm ) (d)

(c)

Absorbance

Absorbance

Toluene [HEMIM][DCA] FILTRATE

1600

1400

1200

1000

800

600

400

3200

-1

3000

2800

2600

2400

2200

2000

1800

-1

Wavenumber (cm )

Wavenumber (cm )

Figure S5. FTIR spectra of ZIF-8, bulk [HEMIM][DCA], and [HEMIM][DCA]/ZIF-8 prior and after washing with toluene in two different regions (400-1600 cm -1 and 1800-3200 cm -1): (a and b) Powder samples before and after washing with toluene, (c and d) filtrate (liquid samples).

SI-10

(b)

Absorbance

Absorbance

(a)

ZIF-8 [HEMIM][DCA] Unwashed [HEMIM][DCA]/ZIF-8 Pentane washed [HEMIM][DCA]/ZIF-8

1600

1400

1200

1000

800

600

400

3200

3000

-1

2800

2600

2400

2200

2000

1800

-1

Wavenumber (cm )

Wavenumber (cm )

(c)

(d)

Absorbance

Absorbance

Pentane [HEMIM][DCA] FILTRATE

1600

1400

1200

1000

800

600

400

3200

-1

3000

2800

2600

2400

2200

2000

1800

-1

Wavenumber (cm )

Wavenumber (cm )

Figure S6. FTIR spectra of ZIF-8, bulk [HEMIM][DCA], and [HEMIM][DCA]/ZIF-8 prior and after washing with pentane (at room temperature) in two different regions (400-1600 cm -1 and 1800-3200 cm -1): (a and b) Powder samples before and after washing with pentane, (c and d) filtrate (liquid samples).

SI-11

ZIF-8 [HEMIM][DCA] [HEMIM][DCA]/ZIF-8

100

4

80

o

3

Derivative weight (wt%/ C)

90

Weight (%)

70 60 2 50 40 1 30 20 0

10 150

300

450

600 o

Temperature ( C)

Figure S7. TGA results of ZIF-8, bulk [HEMIM][DCA], and [HEMIM][DCA]/ZIF-8.

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CO2 Uptake (cc(STP)/g ZIF-8)

100

(a) st

1 Run nd 2 Run

10

1

0.1 1

10

100

1000

CH4 Uptake (cc(STP)/g ZIF-8)

Pressure (mbar) 10

(b) st

1 Run nd 2 Run

1

0.1

0.01

1E-3 1

10

100

1000

Pressure (mbar) Figure S8. Repeated isotherms for [HEMIM][DCA]/ZIF-8 for (a) CO 2 and (b) CH 4 at room temperature.

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Table S1. CO 2/CH 4 selectivity of different MOFs prepared by various postsynthesis modification.

MOF

Pressure (mbar)

Temperature (o C)

Gas Composition (CO2/CH4 )

CO2/CH4 Selectivity

Ideal 5/95 Ideal Ideal Ideal

3.5*5 19*6 4.97 47 3.57

Amine Functionalized NH2 -MIL-101(Al) pip-UiO-66-NH2 UiO-66-(OH) 2 UiO-66-NO2 UiO-66-(OH) 2-NO2

1000 1000 1000 1000 1000

25 25 25 25 25

Solvent/Ligand Functionalized [Zn2 (1) (py-CF3 )2]n

1000

25

50/50

6.5*8

UiO-66-AD4

1000

25

50/50

8.4*9

UiO-66-AD6

1000

25

50/50

10*9

UiO-66-AD8

1000

25

50/50

7.3*9

UiO-66-AD10

1000

25

50/50

9.3*9

BUT-10

1000

25

10/90

5.1*10

BUT-11

1000

25

10/90

9*10

Ideal Ideal Ideal Ideal 50/50

9.411 15.911 4.712 5.112 11.8*13

NJU-Bai7 NJU-Bai8 UiO-66(Zr)-Br UiO-66(Zr)-NO2 Porph(cl-1) @MOM-11(Mn2+)