Supporting Information. Highly Water Stable Zirconium Metal-Organic Framework UiO-66 Membranes. Supported on Alumina Hollow Fibers for Desalination

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1 Supporting Information Highly Water Stable Zirconium Metal-Organic Framework UiO-66 Membranes Supported on Alumina Hollow Fibers for Desalination Xinlei Liu, Nilay Keser Demir, Zhentao Wu and Kang Li* Department of Chemical Engineering, Imperial College London, London SW7 2AZ, United Kingdom S1

2 Preparation: Preparation of alumina hollow fibers The alumina hollow fibers were fabricated by phase inversion method (Figure S14). Spinning and sintering parameters can be found in Figure S14 and more details of the hollow fiber spinning process can be found in our previous study. 1 The hollow fibers were thoroughly washed with acetone before use. Preparation of hollow fiber supported UiO-66 membranes The UiO-66 membranes were fabricated on the outer surface of porous alumina hollow fibers (O.D.: 2.1 mm, length: 60 mm) by an in-situ solvothermal synthesis method (Figure S7). The optimized recipe is: ZrCl 4 (>99.5%, Sigma Aldrich), 1,4-benzenedicarboxylic acid (BDC, 98%, Sigma Aldrich), and DI water (Analytic lab, ACEX, Imperial College) were dissolved in 60 ml N,N-Dimethylformamide (DMF, 99.8%, VWR) under stirring to give a molar composition: Zr 4+ /BDC/H 2 O/DMF=1:1:1:500. This clear solution was transferred into a Teflon-lined stainless steel autoclave (friendly supplied by DICP) in which an alumina hollow fiber was placed vertically with both ends sealed. Afterwards the autoclave was placed in a convective oven (UF30, Memmert) and heated at 120 o C for 3 days. After cooling, the membrane was washed with ethanol (99.85%, VWR) and dried at 25 o C overnight under vacuum (Fistreem Vacuum Oven). To guarantee a high reproducibility it should be noted that anhydrous chemicals and solvent should be kept fresh and handled with care to avoid deliquescence or moisture sorption. This is because the amount of water in the mother solution for membrane synthesis is critical to the nucleation and intergrowth of UiO-66 crystals. Preparation of UiO-66 powders The UiO-66 powders were collected from the mother solution in the above mentioned autoclave after membrane synthesis. The powders were washed by ethanol with the assistance of centrifuge (Thermo Scientific Legend X1R) for later use. S2

3 Characterization: XRD (x-ray diffraction) patterns were recorded on Panalytical Xpert XRD (using Cu Kα radiation, λ=0.154 nm at 40kV and 40mA). The SEM (Scanning Electron Microscope) images and EDXS (Energy-Dispersive X-ray Spectroscopy) were performed on a LEO Gemini 1525 instrument at an accelerating voltage 5kV and 20 kv, respectively. For pore size determination, the mercury intrusion data was collected on Micromeritics Autopore IV instrument assuming a mercury contact angle of 130 o at absolute pressures of between 0.10 to psi. For the UiO-66 powders stability test, each salt (0.20 g) was dissolved in DI water (99.8 g) separately. Afterwards, g of UiO-66 powders was immersed in each saline solution, and then sealed in glass bottles. The bottles were kept statically in a universal oven (Medline Scientific, OV-12) at 50 o C for 100 days. After test, the powders were washed with water before characterization. Nitrogen adsorption isotherms were measured at 77 K, on a Micromeritics Tristar Surface Area and Porosity Analyzer. Before test, the samples were dried at 120 o C under vacuum for 24 hours. The single gas permeance was measured by a soap-film flowmeter at 20 ± 2 o C under the pressure difference of 1.0 bar. The pressure of the permeate side was kept under ambient. The data was recorded until a constant permeance lasted at least 4 hours. Single gas permeation test is one of the best ways to assess the integrity of the polycrystalline membranes. An ideal selectivity (defined as the permeance ratio of gases A and B) for the small gas molecule over the large molecule much larger than the value of the Knudsen diffusion selectivity (ratio of the squared-root of the molecule weight) indicates good quality of the membrane prepared. 2 Desalination performance of the UiO-66 membrane was carried out in a dead-end system (Figure S11) at 20 ± 2 o C under a pressure of 10.0 bar towards saline solutions (0.20wt. %). Saline water feed solutions were filled into a stainless steel membrane cell (around 350 ml) and hollow fiber membrane samples with one end sealed were firstly glued on to sample holders, prior to being fully wetted by feed. The operating pressure (10.0 bar) was supplied by feeding N 2 into the feed vessel and was maintained constantly during the test. The pressure of the permeate side was kept under ambient. The permeate through the membrane was collected every 24 hours and measured. The system and the membrane S3

4 surface were flushed with DI water and dried when the feed was changed. The ion concentrations of the retentate and collected permeate samples were analyzed by conductivity meter (Hanna Instruments, HI-8733N). Rejection (R i ) of the ions was calculated by: R i =(C ir -C ip )*100%/C ir where C ir and C ip represent the ion concentrations in the retentate and permeate solutions, respectively. S4

5 Figure S1. Figure S1. (a) The structure of UiO-66 constructed with Zr 6 cluster and BDC ligand. (b) The structure of UiO-66 cavities and aperture. The size of cavities and aperture is estimated from the largest spheres which may fit them, respectively. This figure was made based on the UiO-66 structure reported by Lillerud et al. 3 S5

6 Figure S2. Figure S2. N 2 adsorption isotherms of UiO-66 powders as prepared (a) and after stability test (b). For stability test, the UiO-66 powders were immersed in 0.20 wt. % MgCl 2 solution at 50 o C for 100 days. S6

7 Figure S3. Figure S3. SEM images of UiO-66 powders as prepared (a) and after stability test (b-g represent H2O, KCl/ H2O, NaCl/ H2O, CaCl2/ H2O, MgCl2/ H2O and AlCl3/ H2O, respectively). For stability test, the UiO-66 powders were immersed in each 0.20 wt. % saline solution at 50 oc for 100 days. S7

8 Figure S4. Figure S4. EDXS data of UiO-66 powders as prepared (a) and after stability test (b-d represent H 2 O, KCl/ H 2 O, NaCl/ H 2 O, respectively). For stability test, the UiO-66 powders were immersed in each 0.20 wt. % saline solution at 50 o C for 100 days. In Figure S4c, 4d, the salt signals are marked where they would be oberseved. No ion exchange reactions occurred since no signals from the salts were identified in the element analysis images. S8

9 Figure S5. Figure S5. EDXS data of UiO-66 powders as prepared (a) and after stability test (b-d represent CaCl 2 / H 2 O, MgCl 2 / H 2 O and AlCl 3 / H 2 O, respectively). For stability test, the UiO-66 powders were immersed in each 0.20 wt. % saline solution at 50 o C for 100 days. In Figure S5b, 5c, 5d, the salt signals are marked where they would be oberseved. No ion exchange reactions occurred since no signals from the salts were identified in the element analysis images. S9

10 Figure S6. Figure S6. a) SEM image of the outer surface of the porous alumina hollow fiber. b) Pore size distribution of the outer (~ 0.18 µm) and inner (~ 0.56 µm) surfaces of the porous alumina hollow fiber. S10

11 Figure S7 Figure S7. Flow diagram of in-situ solvothermal method for UiO-66 membrane fabrication. Before preparation, both ends of the hollow fiber were sealed with the assistance of Teflon tapes and the hollow fiber was inserted in Teflon holders to keep it vertical during the synthesis. S11

12 Figure S8. Figure S8. The XRD patterns of UiO-66 powders and UiO-66 membranes supported on porous alumina hollow fiber and disc. The UiO-66 membrane supported on porous alumina disc was prepared by the same in-situ synthesis method. S12

13 Figure S9. Figure S9. Gas permeation performance of UiO-66 membrane. The single gas permeation was performed by a soap-film flowmeter at 20 ± 2 o C under the pressure difference of 1.0 bar. The order of the gas kinetic diameters is: H 2 (2.9 Å) < CO 2 (3.3 Å) < N 2 (3.6 Å) < CH 4 (3.8 Å). Based on these gas permeation results, no doubt, UiO-66 is a good membrane material for the purpose of H 2 purification and CO 2 capture as well. S13

14 Figure S10. Figure S10. Performance of the UiO-66 membrane and the upper bound correlation for gas separation.. The upper bound correlation for gas separation is cited from reference. 4 Permeability is calculated as the membrane permeance multiplied by the membrane thickness (1 Barrer = mol m / (m 2 s Pa)). The membrane thickness of UiO-66 membrane is about 2.0 µm as shown in the SEM image. S14

15 Figure S11 Figure S11. Schematic diagram of the dead end system for membrane desalination. S15

16 Figure S12. Figure S12. XRD patterns of the porous alumina hollow fiber supported UiO-66 membranes before and after desalination test. S16

17 Figure S13. S17

18 Figure S13. SEM images and EDXS data of the porous alumina hollow fiber supported UiO-66 membranes before (a, c) and after (b, d) desalination test. In Figure S13d, the salt signals are marked where they would be oberseved. S18

19 Figure S14 Figure S14. Schematic diagram of experimental set-up for spinning by phase inversion method and key parameters for fiber fabrication. S19

20 Table S1. Diameters of water and hydrated ions. 5 Water and ions Hydrated diameters (Å) H 2 O 2.76 K Cl Na Ca Mg Al S20

21 Table S2. Desalination performance of UiO-66 and commercial RO & NF membranes. Membranes Rejection (Mg 2+ ) Permeability (Lm -2 h -1 bar -1 µm) Membrane thickness (µm) Permeance (Lm -2 h -1 bar -1 ) References MOF UiO % This work Commercial RO > 98.0% Commercial RO > 99.6% Commercial RO % Commercial RO % Commercial RO & NF > 98.0% S21

22 References: (1) Lee, M.; Wu, Z.; Wang, R.; Li, K. J. Membr. Sci. 2014, 461, 39. (2) Lin, Y. S.; Kumakiri, I.; Nair, B. N.; Alsyouri, H. Sep. Purif. Methods 2002, 31, 229. (3) (a) Cavka, J. H.; Jakobsen, S.; Olsbye, U.; Guillou, N.; Lamberti, C.; Bordiga, S.; Lillerud, K. P. J. Am. Chem. Soc. 2008, 130, (b) Valenzano, L.; Civalleri, B.; Chavan, S.; Bordiga, S.; Nilsen, M. H.; Jakobsen, S.; Lillerud, K. P.; Lamberti, C. Chem. Mater. 2011, 23, (4) Robeson, L. M. J. Membr. Sci. 2008, 320, 390. (5) Nightingale Jr., E. R. J. Phys. Chem. 1959, 63, (6) Zhou, M.; Nemade, P. R.; Lu, X.; Zeng, X.; Hatakeyama, E. S.; Noble, R. D.; Gin, D. L. J. Am. Chem. Soc. 2007, 129, (7) Elimelech, M.; Phillip, W. A. Science 2011, 333, 712. (8) Greenlee, L. F.; Lawler, D. F.; Freeman, B. D.; Marrot, B.; Moulin, P. Water Res. 2009, 43, (9) Lee, K. P.; Aront, T. C.; Mattia, D. J. Membr. Sci. 2011, 370, 1. (10) Pendergast, M. M.; Hoek, E. M. V. Energy Environ. Sci. 2011, 4, S22