SUPPLEMENTARY INFORMATION synthesis of … SUPPLEMENTARY INFORMATION In situ synthesis of thin zeolitic-imidazolate framework ZIF-8 membranes exhibiting exceptionally high propylene/propane

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SUPPLEMENTARY INFORMATION

In situ synthesis of thin zeolitic-imidazolate framework ZIF-8 membranes exhibiting

exceptionally high propylene/propane separation

Hyuk Taek Kwon1 and Hae-Kwon Jeong

1,2*

1Artie McFerrin Department of Chemical Engineering and

2Materials Science and

Engineering Program, Texas A&M University, 3122 TAMU, College Station, TX, USA.

*Author to whom correspondence should be addressed. Email: [email protected].

Tel: +1 979 862 4850 Fax: +1 979 845 6446.

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Figure S1. SEM images of ZIF-8 membranes grown for 2 min (a, b), 10 min (c, d), 30 min (e, f), 1 h (g,

h), 2 h (i, j), 3 h (k, l), and 4 h (m, n)

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

(j)

(k)

(l)

(m) (n)

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Figure S2. SEM images of ZIF-8 films synthesized by solvothermally treating a support soaked with a

ligand solution containing sodium formate in a metal solution (a) and by solvothermally treating a support

soaked with a metal solution in a ligand solution without sodium formate (b). Both films were prepared at

at 120ºC.

(b)

(a)

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Figure S3. SEM images of ZIF-8 films synthesized when a ligand solution is saturated inside of a support

and solvothermally treated in a metal solution; the addition of extra sodium formate of 0.35g in a metal

solution (a), and the addition of extra sodium formate of 0.35g and 0.5g in both of a metal solution and a

ligand solution, respectively (b). In a original recipe, a support saturated with a metal solution (0.98g of

ZnCl2 in 40 ml of methanol) is solvothermally treated in a ligand solution (5.19 g of 2-methylimidazole +

0.5g of sodium formate in 40 ml of methanol).

(a)

(b)

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Figure S4. XRD patterns of of ZIF-8 films synthesized when a ligand solution is saturated inside of a

support and solvothermally treated in a metal solution; the addition of extra sodium formate of 0.35g in a

metal solution (a), and the addition of extra sodium formate of 0.35g and 0.5g in both of a metal solution

and a ligand solution, respectively (b). In an original recipe, a support saturated with a metal solution

(0.98g of ZnCl2 in 40 ml of methanol) is solvothermally treated in a ligand solution (5.19 g of 2-

methylimidazole + 0.5g of sodium formate in 40 ml of methanol).

6 9 12 15 18 21 24

Simulated pattern

(b)

Intensity (a.u.)

2 theta (degree)

(a)

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Figure S5. Schematic diagram of gas permeation set-up (Wicke-Kallenbach technique).

Propylene

MFC

MFC

Ar

Propane

MFC

Vent

GC

Bubble flow

meter

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Figure. S6 SEM images of ZIF-8 membranes synthesized by conventional in-situ method1; top view (a)

and cross-section (b)

(a)

(b)

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Figure S7. Propylene/propane separation performance of ZIF-8 membranes grown for 4 h as a function of

temperature; binary (a) and single gas (b)

20 40 60 80 100 120 140 160

0

40

80

120

160

200

Perm

eance (x 10

-10 m

ol m

-2s-1 Pa

-1)

Temperature (oC)

0

25

50

75

100

Separation factor

Propane

C3H

6/C

3H

8 separation factor

Propylene

20 40 60 80 100 120 140 160

0

40

80

120

160

200

Propylene

Perm

eance (x 10

-10 m

ol m

-2s-1 Pa

-1)

Temperature (oC)

0

20

40

60

80

100

C3H

6/C

3H

8 id

eal selectivity

Ideal selectivity

Propane

(a)

(b)

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Figure S8. Schematic illustration of the defect healing process via the CD-based in situ method. The self-

limiting nature of the counter-diffusion concept enables the defective membranes to be identified since

crystals grow preferentially from defects or cracks where the separated metal ions and ligand molecules

are in contact.

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Figure S9. Digital photograph of a home-made counter diffusion cell. Note that the picture was taken

after the healing process was completed.

Membrane side Support side

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Figure S10. XRD patterns of ZIF-8 membranes; synthesized with a ligand solution recycled four times

(a), healed by a counter-diffusion-based in situ growth (b), and healed by a secondary growth (c)

5 10 15 20

(b)

(c)

Intensity (a.u.)

2 theta

(a)

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Table S1 Room-temperature propylene/propane separation performance of the ZIF-8 membranes after

being healed in a diffusion cell. The defective membranes showed no separation performance.

Membrane

Permeance of propylene

(10-10

mol/m2· s· pa)

Selectivity

(After healing)

Before healing After healing

M1 2496.94 406.35 8.77

M2 2139.47 392.02 9.43

M3 2385.11 407.75 9.78

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Figure S11. XRD patterns of ZIF-8 membranes synthesized in recycled solutions obtained after;

counter-diffusion-based in situ growth (a) and conventional in-situ method1 (b). R0 and R1 denote the

membranes prepared in a fresh precursor solution and in a solution recycled once, respectively.

6 9 12 15 18 21 24

R5

R4

R3

R2

R1

Intensity (a.u.)

2 theta (degree)

R0

6 9 12 15 18 21 24

X 1/5

R1

Intensity (a.u.)

2 theta (degree)

R0

(a)

(b)

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Table S2 Room-temperature propylene/propane separation performance of the ZIF-8 membranes

synthesized with recycled ligand solutions

# of recycling Permeance of propylene

Separation factor (10

-10 mol m

-2 s

-1 Pa

-1)

1st 231.87 ± 39.55 34.48 ± 5.25

2nd

200.40 ± 18.98 26.99 ± 4.70

3rd

285.50 ± 23.12 31.06 ± 4.87

4th Defective -

5th Defective -

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Figure S12. Binding strength of ZIF-8 membranes on a support measured by normalized (110)

peak intensity as a function of sonication time (a) and a SEM image of the ZIF-8 membrane after

sonication for 2 h (b)

0.0 0.5 1.0 1.5 2.00

20

40

60

80

100

I (110)/Io

(110) (%

)

Sonication time (h)

(a)

(b)

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Table S3 Propylene/propane separation performance of ZIF-8 membranes before and after 2 h of

sonication

Sonication time

(h)

Permeance

(x 10-10 mol m-2

s-1 Pa-1

) Separation factor

(C3H6/C3H8) C3H6 C3H8

0 192.88 ± 2.32 4.61 ± 0.63 43.25 ± 5.82

2 277.99 ± 12.19 7.67 ± 0.41 37.09 ± 2.66

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Synthesis of SIM-1 membranes

In a typical synthesis, 5 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O, 98%, Sigma-Aldrich)

was dissolved in 40 mL of ethanol (99.88%, Sigma-Aldrish), and 1 g of 4-methyl-5-

imidazolecarboxaldehyde (C5H6N2O, 95%, Santa Cruz Biotechnology) and 0.05 g of sodium

formate (HCOONa, 99%, Sigma-Aldrich) was dissolved in 40 mL of ethanol (solution B). A

home-made α-Al2O3 disk was soaked in the solution A for 1 hr. The disk saturated with the zinc

salt solution was positioned vertically in a Teflon-lined autoclave containing the solution B.

Then, the autoclave was subjected to solvothermal synthesis for 4 h at 85⁰C. After synthesis, the

membrane sample was rinsed with ethanol several times and immersed in ethanol for washing

under stirring for 1 day. Afterward, one side of the supported membranes was polished with sand

paper manually since films are formed on both sides of supports. Additional washing of 4 days

was conducted before drying at room temperature for 48 h.

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Synthesis of ZIF-7 membranes

In a typical synthesis, 3.06 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O, 98%, Sigma-

Aldrich) was dissolved in 40 mL of dimethylformamide (99.88%, Alfa Aesar, hereafter DMF),

and 1.62 g of benzimidazole (C7H6N2, 98%, Sigma-Aldrich, hereafter b-Im) and 0.01 g of

sodium formate (HCOONa, 99%, Sigma-Aldrich) was dissolved in 40 mL of DMF (solution B).

A home-made α-Al2O3 disk was soaked in the solution A for 1 hr. The disk saturated with the

zinc salt solution was positioned vertically in a Teflon-lined autoclave containing the solution B.

Then, the autoclave was subjected to solvothermal synthesis for 4 h at 85⁰C. After synthesis, the

membrane sample was rinsed with DMF and ethanol several times and immersed in ethanol for

solvent exchange under stirring for 1 day. Afterward, one side of the supported membranes was

polished with sand paper manually since films are formed on both sides of supports. Additional

solvent exchange of 4 days was conducted before drying at room temperature for 48 h.

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Figure S13. SEM images of a SIM-1 membrane (a, b) and a ZIF-7 membrane (c, d)

(a) (b)

(c) (d)

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Figure S14. XRD patterns of a SIM-1 membrane (a) and a ZIF-7 membrane (b)

* Due to the lack of the crystallographic information of SIM-1, SIM-1 powders were synthesized by

following the previous report2 and its XRD pattern is compared to confirm the SIM-1 phase.

5 10 15 20 25 30

Powders*

Intensity (a.u.)

2 theta (degree)

A SIM-1 membrane

α −Al2O

3

5 10 15 20 25 30

α −Al2O

3

Simulated pattern

A ZIF-7 membrane

Intensity (a.u.)

2 theta (degree)

(a)

(b)

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References

(1) Shah, M.; Kwon, H. T.; Tran, V.; Sachdeva, S.; Jeong, H.-K. Microporous Mesoporous Mater. 2013, 165,

63.

(2) Aguado, S.; Canivet, J.; Farrusseng, D. Chem. Commun. 2010, 46, 7999.