Introduction
Fig.1 (a) The unit cell of UiO-66 constructed with Zr6 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. (c) Possible tetravalent metal ions for preparing UiO-66 type MOFs. (d) Possible BDC type ligands for constructing UiO-66 type MOFs. Ligands labeled in blue indicate their corresponding MOFs have been reported. Reproduced from [28] and [29] with permission, copyright American Chemical Society, 2015 and Royal Chemical Society, 2015. |
Approaches for fabricating UiO-66 membranes
In situ synthesis
Fig.2 (a) Schematic diagram showing in situ synthesis of UiO-66 membranes on YSZ substrate. Scanning electron microscopy (SEM) images of UiO-66 membranes via in situ synthesis on α-alumina hollow fibers (b), YSZ hollow fibers (c), EDXS mapping image, C signal, yellow; Y signal, green), micropatterned YSZ sheets (d) and nanochanneled PET films (scale bar 100 nm) (e). Reproduced from [28,86–88] with permission, copyright John Wiley and Sons 2017, 2018; American Chemical Society, 2015; the American Association for the Advancement of Science, 2018. |
Secondary growth
Fig.3 (a) SEM images ((1) surface; (2) cross section) of the UiO-66 membrane prepared by secondary growth and scheme (3) of the octahedrons’ orientation within the UiO-66 membrane and their orientation to the substrate surface; (b) photograph (1) and SEM image (2) of 2D monolayer UiO-66 on a water surface and a silicon platform, respectively; cross-sectional SEM images (3) and the corresponding X-ray diffraction (XRD) patterns (4) of silicon platform-supported UiO-66 films comprising one, two, and three monolayers of microcrystals prepared by repetition of the transfer process using self-assembly; (c) SEM images (1) surface; (2) cross section) of UiO-66 film prepared by three repeated solvothermal syntheses and the corresponding XRD patterns (3). Reproduced from [95,105,117] with permission, copyright American Chemical Society, 2017; John Wiley and Sons 2013; Royal Chemical Society 2015. |
Biphase synthesis
Gas-phase deposition
Fig.5 Fabrication of UiO-66 related films via gas-phase deposition. (a) Deposition of UiO-66 films by all-gas phase process: (1) experimental setup for post-treatment of the hybrid films with acetic acid vapor; XRD patterns (2) and cross-sectional SEM images (3) of the UiO-66 film after the treatment with acetic acid. (b) Schematic diagram of the vapor-assisted conversion process for the fabrication of (111)-oriented UiO-66-NH2 films. ZrOCl2, BDC-NH2, and the modulator acetic acid (if desired) were dissolved in DMF giving the precursor solution on top of the substrate; a mixture of DMF and acetic acid giving the vapor source at the bottom of the vessel. Reproduced from [106,108] with permission, copyright Springer Nature, 2016 and American Chemical Society, 2018. |
Electrochemical deposition
Tab.1 Summary of UiO-66 type membranes in terms of substrates, synthetic approaches and applications |
Materials | Substrates | Synthetic approaches | Applications | Ref. |
---|---|---|---|---|
UiO-66 | α-Alumina hollow fibers | In situ synthesis (Zr4+/BDC/H2O/DMF= 1:1:1:500, 72 h, 120°C) | Nanofiltration (K+, Na+, Ca2+, Mg2+, Al3+, Cl–, H2O) Gas separation (H2, CO2, N2, CH4) | [28] |
UiO-66 | YSZ hollow fibers | In situ synthesis (Zr4+/BDC/H2O/DMF= 1:1:1:500, 48 h, 120°C) | Pervaporation (furfural, THF, acetone, i-butanol, n-butanol, propanol, ethanol, water) | [86] |
UiO-66 | Micro-patterned YSZ discs | In situ synthesis (Zr4+/BDC/H2O/DMF= 1:1:1:500, 48 h, 120°C) | Pervaporation (n-butanol, water) | [87] |
UiO-66 | Channeled PET | In situ synthesis (Zr4+/BDC/DMF= 1:1:500, 24 h, 100°C) | Electro-chemical ion separation (Li+, Na+, K+, Rb+) | [88] |
UiO-66-NH2 | ZrO2 modified alumina tubes | In situ synthesis (modified substrates) (Zr4+/BDC-NH2/H2O/CH3COOH/DMF= 1:1:1:150:500, 48 h, 120°C) | Pervaporation (thiophene, n-octane) | [90] |
UiO-66-NH2 | APTES modified α-alumina tubes | In situ synthesis (modified substrates) (Zr4+/BDC-NH2/H2O/DMF= 1:1:1:500, 24 h, 120°C) | Pervaporation (Na+, K+, Ca2+, Mg2+, NH4+, F–, Cl–, and NO3–, H2O) | [89] |
UiO-66 | α-alumina tubes | Secondary growth (Zr4+/BDC/H2O/CH3COOH/DMF= 1:1:1:500:x, x = 750, 1000, 1500, 24 h, 120°C, repeated three times) | Pervaporation (Methanol, ethanol, acetone, water, xylene, trimethylbenzene) Gas separation (H2, CO2, N2) | [91] |
UiO-66-CH3 | Porous Ni sheets | Secondary growth (Zr4+/BDC-CH3/CH3COOH/DMF= 1:1:30:430, 24 h, 120°C) | Gas separation (CO2, N2) | [92] |
UiO-66 | α-Alumina tubes | Secondary growth (Zr4+/BDC-NH2/H2O/CH3COOH/DMF= 1:1:1:150:500, 72 h, 120°C) | Pervaporation (methanol, methyl tert-butyl ether) | [93] |
UiO-66-(OH)2 | α-Alumina hollow fibers | Secondary growth (Zr4+/ODBDC/HCOOH/DMF= 1:1:100:500, 72 h, 120°C) | Nanofiltration (Fe3+, Cr3+, Zn2+, Mg2+, Na+, Cl–, H3BO3, methyl blue, H2O) | [94] |
UiO-66 | α-Alumina discs | Secondary growth (Zr4+/BDC/Benzoic acid/DMF= 1:1:20:100, 24 h, 180°C) | Gas separation (H2, CO2, N2, CH4, C2H6, C3H8) | [59,95] |
UiO-66 | Anodic aluminum oxide, AAO | Secondary growth (Zr4+/BDC/H2O/DMF= 1:1:1:500, 72 h, 120°C) | Gas separation (H2, CO2, N2, CH4) | [126] |
UiO-66 | α-Alumina discs | Biphase synthesis DMF phase: 15 mL, Zr/BDC/HCOOH/DMF= 1:0.5:125:130, and 1:0.7:125:130, Hexane phase: 1836 mg TEA in 15 mL hexane, 24 h, 120°C | Gas separation (CO2, N2) | [96] |
Tab.2 Summary of UiO-66 films in terms of substrates, synthetic approaches and applications |
Materials | Substrates | Synthetic approaches | Applications | Ref. |
---|---|---|---|---|
UiO-66 | BDC functionalized FTO glasses | In situ synthesis (modified substrate) (Zr4+/BDC/CH3COOH/DMF= 1:1:96:520, 24 h, 120°C) | Cyclic voltammetry ion separation (Ru(NH3)63+, Fe(phen)32+, Fe(CN)63+) | [99] |
UiO-66-SO3H-NH2 | PDA-coated PU foams | In situ synthesis (modified substrate) (Zr4+/BDC-SO3H/BDC-NH2/H2O/CH3COOH= 1:0.75:0.25:230:100) | Catalysis (from glucose to HMF) | [100] |
UiO-66 | ZrO2 fibrous mats | In situ synthesis (ZrO2/BDC/CH3COOH/H2O= 1:3.7:2.2:686) | Not reported | [101] |
UiO-66-NH2 | ATA modified PAN fibers | In situ synthesis (modified substrate) (Zr4+/BDC-NH2/acetone= 1:1:200) | Chlorine adsorption | [102] |
UiO-66 | Silanized a-alumina and ob-SiC foams | In situ synthesis (modified substrate) (Zr4+/BDC//DMF= 1:0.9:380, 24 h, 120°C) | Not reported | [103] |
UiO-66 | Stainless meshes | Secondary growth (Zirconium propoxide/BDC/DMF, 12 h, RT) | Oil-water separation (diesel, vegetable oil, pump oil, cyclohexane, water) | [104] |
UiO-66 | Si discs | Secondary growth (Zr4+/BDC/H2O/CH3COOH/DMF= 1:1:1:0/500:1500, 24 h, 120°C, repeated three times) | Not reported | [105] |
UiO-66 | Si discs | Gas-phase deposition (ZrCl4 (165°C), BDC (220°C), CH3COOH (RT), N2; post treatment: 160°C CH3COOH, 24 h) | Not reported | [106] |
UiO-66-NH2 | Si discs | Gas-phase deposition (ZrCl4 (165°C), BDC-NH2 (225°C), N2; post treatment: 160°C CH3COOH, 24 h) | Not reported | [107] |
UiO-66-NH2 (UiO-66) | Gold, Si discs | Vapor-assistant conversion (Precursor solution: ZrOCl2•8H2O+ BDC-NH2 (BDC) + CH3COOH+ DMF Vapor source: DMF+ CH3COOH, 100°C, 3 h) | Ethanol adsorption | [108] |
UiO-66 | FTO glasses | Electrophoretic deposition (10 mg UiO-66 particles in 20 mL toluene, DC voltage of 90 V) | Not reported | [109] |
UiO-66 | Zirconium foil | Electrochemical deposition (BDC:HNO3:H2O:CH3COOH:DMF= 1:2:4:5/10/50:130, 80 mA, 110°C) | Sorbent trap (Toluene) | [110] |
UiO-66 | Free-standing | Biphase synthesis DMF phase: 5 mL, Zr/BDC/HCOOH/DMF = 1:0.25:87.5:130, 1:0.25:100:130, 1:0.25:118:130, 1:0.4:125:130, 1:0.5:125:130, 1:0.7:125:130, 1:0.6:150:130, 1:0.84:150:130 Hexane phase: 612 mg TEA in 5 mL hexane, 120°C, 24 h | Not reported | [96] |
UiO-66 | Cellulose supports | Filtration (UiO-66 particles in water) | Nanofiltration (methylene blue, water) | [111] |
UiO-66 | Silicon wafers | Solution shearing (UiO-66 particles in DMF/H2O/MeOH) | Not reported | [112] |
UiO-66 | Silicon platform | Self-assembly (PVP modified UiO-66 in ethanol/water solution containing sodium dodecyl sulfate) | Not reported | [117] |
Applications of UiO-66 membranes
Gas separation
Fig.7 (a) Single component permeation data of UiO-66 membranes at 293 K with 1 bar pressure difference; (b) H2 mixed binary permeation data of (002) oriented UiO-66 membrane at 298 K and 1 bar (absolute pressure) in both feed and sweep sides. Reproduced from [28,95] with permission, copyright American Chemical Society, 2015 and 2017. |
Pervaporation
Fig.8 (a) Flow chart and pervaporative organic (n-butanol and furfural) dehydration performance of UiO-66 membranes during on-stream activation and stability test processes at 30°C with 5 wt-% water in the feed; (b) thiophene/n-octane separation performance of UiO-66-NH2 membrane and a comparison with polymers. Reproduced from [86,90] with permission, copyright John Wiley and Sons 2017, and Elsevier 2018. |
Nanofiltration
Fig.9 (a) Desalination performance of the UiO-66 membrane for KCl, NaCl, CaCl2, MgCl2 and AlCl3 aqueous solutions with a concentration of 0.20 wt-% at 20°C under a pressure difference of 10.0 bar; (b) separation performance of the UiO-66-(OH)2 membrane before and after PSDH under a pressure difference of 3 bar with 2000 ppm NaCl and 100 ppm methyl blue aqueous solutions; (c) scheme of PSDH by relinking. Reproduced from [28,94] with permission, copyright American Chemical Society, 2015 and 2017. |
Electrochemical ion separation
Fig.10 (a) Ion selectivity over the pore diameter of MOF and porous membranes; (b) cyclic voltammograms of Ru(NH3)63+/Fe(phen)32+ mixture in aqueous solutions on MOF-coated electrode treated with PDMS (red solid lines) and bare FTO electrode (black dashed lines). Reproduced from [88,99] with permission, copyright American Association for the Advancement of Science 2018, and John Wiley and Sons 2016. |