Transparent Metal-Organic Framework/Polymer Mixed Matrix ...
Supporting Information
Transparent Metal-Organic Framework/Polymer Mixed Matrix Membranes as Water Vapor Barriers Youn Jue Bae,†,‡,§ Eun Seon Cho,‡,§ Fen Qiu,‡ Daniel T. Sun,¶ Teresa E. Williams,‡,¥ Jeffrey J. Urban,‡,* and Wendy L. Queen¶,* †
Department of Chemistry, University of California, Berkeley, California 94720, United States,
‡
The Molecular Foundry, Materials Sciences Division, Lawrence Berkeley National Laboratory,
Berkeley, California 94720, United States, ¶Institut des Sciences et Ingénierie Chimiques, École Polytechnique Fédérale de Lausanne (EPFL) CH 1051 Sion, Switzerland, ¥Graduate Group in Applied Science & Technology, University of California, Berkeley, California 94720, United States. §These authors contributed equally to this work.
Corresponding author email: [email protected], [email protected]
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Experimental Details Preparation of Zr6O4(OH)4(fumarate)6 NCs. Fumaric acid (0.18 g, 4.3 mmol) and ZrOCl2•8H2O (0.5 g, 4.3 mmol) were dissolved in a water/formic acid mixture. For the 25 nm and 300 nm Zr6O4(OH)4(fumarate)6 NCs the ratio of water to formic acid were 12.5 mL/1.75 mL and 23.4 mL/5.86, respectively. The solution was then stirred at room temperature for 16 hours. The resulting white NCs were separated via centrifugation and subsequently washed three times with DMF (5 mL) to remove excess fumaric acid and methanol (5 mL). For samples activation, the solid sample was separated from the DMF solution, suspended in methanol (5 mL) for 24 hours, and subsequently dried under vacuum for 24 hours. Ligand exchange (LE). The resulting solid was suspended in ethanol (6 mL) with oleic acid (4.3 mmol, 1 eq to fumaric acid) and stirred at 50 °C for 1 day. The ligand-exchanged NCs were acquired via centrifugation and then washed with ethanol (5 mL) three times. The LE -MOF was then suspended in ethanol for 24 hours and then activated under vacuum for 24 hours. Preparation of COC and COC-MOF films. A mixture of COC (15 wt%) and MOF NCs (1 wt% or 2 wt%) was stirred in cyclohexane until the materials were well dispersed. The films were prepared by doctor-blading the COC (15 wt%) or the composite solution deposited onto a poly(ethylene terephthalate) (PET) substrate (Dupont Teijin ST504). The amount of MOF loaded into the resulting membranes is approximately 6.25 wt % and 11.8 wt % for COC-MOF (1) and COC-MOF (2), respectively. Characterization of MOF NCs. Fourier Transform Infrared (FT-IR) spectra were recorded on a PerkinElmer FT-IR spectrometer fitted with a Diffuse Reflectance Sampling accessory (DRIFT). Powder X-ray diffraction (PXRD) was measured at Advanced Light Source on Beamline 12.2.2. Field-emission (FE)-SEM images were taken on a ZEISS Ultra-55 scanning S-2
electron microscope with SE2 detector (working distance 7.5 mm; acceleration voltage 5 kV). It should be noted that the membrane sample for the SEM image was prepared on a Si wafer via doctor-blading resulting in films that were slightly thicker than those deposited on PET. Elemental microanalyses (EQ) were performed in the Microanalytincal Laboratory of the College of Chemistry at UC Berkeley using a PerkinElmer 2400 series II CHNS elemental analyzer. Low-pressure nitrogen gas adsorption isotherms were measured with Tristar from micromertics at 77 K. Water isotherm was measured on a Micromeritics ASAP2020 with vapor accessory. Prior to the water adsorption measurements, water was flash frozen under liquid nitrogen and evacuated under dynamic vacuum at least 3 times to remove any gases in the water reservoir. Characterization of COC and COC-MOF membrane films. The coated composite films were dried under vacuum at 60 ºC for 24 hours to remove residual solvent and to activate the MOF NCs. WVTR measurements were conducted at Mocon Inc, using Permatran 3/33 unit. The thickness of the film was measured via VEECO DEKTAK 150 Profilometer. The UV-vis measurement was performed using Cary-5000 UV-Vis. SEM images were recorded on a Zeiss Gemini Ultra-55 Analytical Scanning Electron Microscope using an accelerating voltage of 2 kV and a secondary electron detector. Samples were blade coated onto Si wafers, then coated with a few nanometers of amorphous carbon using an Electron Microscopy Sciences 150T ES high vacuum carbon evaporator prior to top-down imaging. Samples for cross-section were cut at room temperature and imaged without further manipulation. Thermal gravimetric analysis (TGA) was performed under air at a scan rate of 5 ºC/min using a TA Instruments Q5000IR.
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Decoupling WVTR values of the membrane films from the total system. The WVTR value of each sample film was decoupled from that of the total system, which represents the combination of the PET substrate and the sample film. Adapting the equation by Lahtinen et al1, individual WVTR values contributed from each layer in a multilayer system can be decoupled from the total WVTR value, based on the following equation. 1 1 1 1 = + + ⋯ In our study, the below equation was applied: 1 1 1 = + The WVTR values obtained from the composite films are presented in Table 1.
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Figure S1. SEM image of inter-grown Zr6O4(OH)4(fumarate)6 synthesized in DMF at 120 °C
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Figure S2. SEM images of (a) 179 nm (±127 nm) and (b) 44 nm (±10 nm) MOF NCs synthesized using 100 eq. and 50 eq. of formic acid (in 5 mL of water), respectively, and (c) 45 nm (±17 nm) and (d) 94 nm (±45 nm) MOF NCs synthesized using 8 mL and 5 mL of water (with 70 eq. of formic acid), respectively.
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Figure S3. Nitrogen isotherm results for (a) 25 m and (b) 300 nm Zr6O4(OH)4(fumarate)6 NCs collected at 77 K.
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Figure S4. UV-Vis spectra of COC and mixed-matrix membrane films that were stored in open air (with varying humidity levels) for 3 months, followed by an additional exposure to 85 % RH at 85 ºC for 3 days.
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Figure S5. TGA measurement of the mixed-matrix membrane film (COC + LE-300 nm MOF NCs (2)). For the saturated sample (red line), the film was exposed to open air (with varying humidity levels) for 3 months followed by an additional exposure to 85 % RH at 85 ºC for 3 days. The re-activated sample (blue line) refers to the TGA of the film after treatment under vacuum at 60ºC.
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Table S1. Elemental analysis of 25 nm and 300 nm MOF NCs before and after ligand exchange.
References 1.
Lahtinen, K.; Kuusipalo, J. Statistical Prediction Model for Water Vapor Barrier of Extrusion-Coated Paper. Tappi J 2008, 7, 8-15.
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Transparent Metal-Organic Framework/Polymer Mixed Matrix Membranes as Water Vapor Barriers Youn Jue Bae,†,‡,§ Eun Seon Cho,‡,§ Fen Qiu,‡ Daniel T. Sun,¶ Teresa E. Williams,‡,¥ Jeffrey J. Urban,‡,* and Wendy L. Queen¶,* †
Department of Chemistry, University of California, Berkeley, California 94720, United States,
‡
The Molecular Foundry, Materials Sciences Division, Lawrence Berkeley National Laboratory,
Berkeley, California 94720, United States, ¶Institut des Sciences et Ingénierie Chimiques, École Polytechnique Fédérale de Lausanne (EPFL) CH 1051 Sion, Switzerland, ¥Graduate Group in Applied Science & Technology, University of California, Berkeley, California 94720, United States. §These authors contributed equally to this work.
Corresponding author email: [email protected], [email protected]
S-1
Experimental Details Preparation of Zr6O4(OH)4(fumarate)6 NCs. Fumaric acid (0.18 g, 4.3 mmol) and ZrOCl2•8H2O (0.5 g, 4.3 mmol) were dissolved in a water/formic acid mixture. For the 25 nm and 300 nm Zr6O4(OH)4(fumarate)6 NCs the ratio of water to formic acid were 12.5 mL/1.75 mL and 23.4 mL/5.86, respectively. The solution was then stirred at room temperature for 16 hours. The resulting white NCs were separated via centrifugation and subsequently washed three times with DMF (5 mL) to remove excess fumaric acid and methanol (5 mL). For samples activation, the solid sample was separated from the DMF solution, suspended in methanol (5 mL) for 24 hours, and subsequently dried under vacuum for 24 hours. Ligand exchange (LE). The resulting solid was suspended in ethanol (6 mL) with oleic acid (4.3 mmol, 1 eq to fumaric acid) and stirred at 50 °C for 1 day. The ligand-exchanged NCs were acquired via centrifugation and then washed with ethanol (5 mL) three times. The LE -MOF was then suspended in ethanol for 24 hours and then activated under vacuum for 24 hours. Preparation of COC and COC-MOF films. A mixture of COC (15 wt%) and MOF NCs (1 wt% or 2 wt%) was stirred in cyclohexane until the materials were well dispersed. The films were prepared by doctor-blading the COC (15 wt%) or the composite solution deposited onto a poly(ethylene terephthalate) (PET) substrate (Dupont Teijin ST504). The amount of MOF loaded into the resulting membranes is approximately 6.25 wt % and 11.8 wt % for COC-MOF (1) and COC-MOF (2), respectively. Characterization of MOF NCs. Fourier Transform Infrared (FT-IR) spectra were recorded on a PerkinElmer FT-IR spectrometer fitted with a Diffuse Reflectance Sampling accessory (DRIFT). Powder X-ray diffraction (PXRD) was measured at Advanced Light Source on Beamline 12.2.2. Field-emission (FE)-SEM images were taken on a ZEISS Ultra-55 scanning S-2
electron microscope with SE2 detector (working distance 7.5 mm; acceleration voltage 5 kV). It should be noted that the membrane sample for the SEM image was prepared on a Si wafer via doctor-blading resulting in films that were slightly thicker than those deposited on PET. Elemental microanalyses (EQ) were performed in the Microanalytincal Laboratory of the College of Chemistry at UC Berkeley using a PerkinElmer 2400 series II CHNS elemental analyzer. Low-pressure nitrogen gas adsorption isotherms were measured with Tristar from micromertics at 77 K. Water isotherm was measured on a Micromeritics ASAP2020 with vapor accessory. Prior to the water adsorption measurements, water was flash frozen under liquid nitrogen and evacuated under dynamic vacuum at least 3 times to remove any gases in the water reservoir. Characterization of COC and COC-MOF membrane films. The coated composite films were dried under vacuum at 60 ºC for 24 hours to remove residual solvent and to activate the MOF NCs. WVTR measurements were conducted at Mocon Inc, using Permatran 3/33 unit. The thickness of the film was measured via VEECO DEKTAK 150 Profilometer. The UV-vis measurement was performed using Cary-5000 UV-Vis. SEM images were recorded on a Zeiss Gemini Ultra-55 Analytical Scanning Electron Microscope using an accelerating voltage of 2 kV and a secondary electron detector. Samples were blade coated onto Si wafers, then coated with a few nanometers of amorphous carbon using an Electron Microscopy Sciences 150T ES high vacuum carbon evaporator prior to top-down imaging. Samples for cross-section were cut at room temperature and imaged without further manipulation. Thermal gravimetric analysis (TGA) was performed under air at a scan rate of 5 ºC/min using a TA Instruments Q5000IR.
S-3
Decoupling WVTR values of the membrane films from the total system. The WVTR value of each sample film was decoupled from that of the total system, which represents the combination of the PET substrate and the sample film. Adapting the equation by Lahtinen et al1, individual WVTR values contributed from each layer in a multilayer system can be decoupled from the total WVTR value, based on the following equation. 1 1 1 1 = + + ⋯ In our study, the below equation was applied: 1 1 1 = + The WVTR values obtained from the composite films are presented in Table 1.
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Figure S1. SEM image of inter-grown Zr6O4(OH)4(fumarate)6 synthesized in DMF at 120 °C
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Figure S2. SEM images of (a) 179 nm (±127 nm) and (b) 44 nm (±10 nm) MOF NCs synthesized using 100 eq. and 50 eq. of formic acid (in 5 mL of water), respectively, and (c) 45 nm (±17 nm) and (d) 94 nm (±45 nm) MOF NCs synthesized using 8 mL and 5 mL of water (with 70 eq. of formic acid), respectively.
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Figure S3. Nitrogen isotherm results for (a) 25 m and (b) 300 nm Zr6O4(OH)4(fumarate)6 NCs collected at 77 K.
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Figure S4. UV-Vis spectra of COC and mixed-matrix membrane films that were stored in open air (with varying humidity levels) for 3 months, followed by an additional exposure to 85 % RH at 85 ºC for 3 days.
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Figure S5. TGA measurement of the mixed-matrix membrane film (COC + LE-300 nm MOF NCs (2)). For the saturated sample (red line), the film was exposed to open air (with varying humidity levels) for 3 months followed by an additional exposure to 85 % RH at 85 ºC for 3 days. The re-activated sample (blue line) refers to the TGA of the film after treatment under vacuum at 60ºC.
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Table S1. Elemental analysis of 25 nm and 300 nm MOF NCs before and after ligand exchange.
References 1.
Lahtinen, K.; Kuusipalo, J. Statistical Prediction Model for Water Vapor Barrier of Extrusion-Coated Paper. Tappi J 2008, 7, 8-15.
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