Efficient Separation of Ethanol–Methanol and Ethanol–Water Mixtures Using ZIF-8 Supported on a Hierarchical Porous Mixed-Oxide Substrate

Abstract

This work reports a new approach for the synthesis of a zeolitic imidazolate framework (ZIF-8) composite. It employs the direct growth of the crystalline ZIF-8 on a mixed-metal oxide support TiO2–SiO2 (TSO), which mimics the porous structure of Populus nigra. Using the natural leaf as a template, the TSO support was prepared using a sol–gel method. The growth of the ZIF-8 layer on the TSO support was carried out by the seeds and second growth method. This method facilitates the homogeneous dispersion of ZIF-8 crystals at the surface of the TSO composite. The ZIF-8@TSO composite adsorbs methanol selectively, mainly due to the hierarchical porous structure of the mixed oxide support. As compared with the as-synthesized ZIF-8, a 50% methanol uptake is achieved in the ZIF-8@TSO composite, with only 25 wt % ZIF-8 loading. IAST simulations show that the ZIF-8@TSO composite has a preferential adsorption toward methanol when using an equimolar methanol–ethanol mixture. An opposite behavior is observed for the as-synthesized ZIF-8. The results show that combining MOFs and mixed-oxide supports with bioinspired structures opens opportunities for synthesizing new materials with unique and enhanced adsorption and separation properties.

Water–Ethanol and Methanol–Ethanol Separations Using in Situ Confined Polymer Chains in a Metal–Organic Framework

“…49 Selectivities calculated with the IAST method using equimolar water–alcohol mixtures have been reported for both MOFs and MOF-based composites. Thus, DMOF ⊃ PNIPAM- 3 in this study has a higher methanol–ethanol selectivity than ZIF-8@TSO (up to 3.8), 50 ZIF-8 (up to 4.5), 50 TetZB (up to ∼1) 13 and [Cu 2 (tpt) 2 (CH 3 CN) 2 ](BF 4 ) 2 (up to 11). 51 It also has a higher water–ethanol selectivity as compared with ZIF-8@TSO (up to 1.8).…”

“…51 It also has a higher water–ethanol selectivity as compared with ZIF-8@TSO (up to 1.8). 50 The water–ethanol selectivity is lower as compared with ZIF-8 and TetZB as a result of the high hydrophobicity of these frameworks. [Cu 2 (tpt) 2 (CH 3 CN) 2 ](BF 4 ) 2 has a unique molecular length-selective effect which favors selective water adsorption.…”

“…[Cu 2 (tpt) 2 (CH 3 CN) 2 ](BF 4 ) 2 has a unique molecular length-selective effect which favors selective water adsorption. 13,50,51…”

Functional Metal Organic Framework/SiO2 Nanocomposites: From Versatile Synthesis to Advanced Applications

“…For water treatment, the addition of silica can improve the dispersion of MOFs in composite materials, which is extremely beneficial for the adsorption of pollutants in water and has great potential in the prevention and control of water pollution [147]. Han et al synthesized a series of SiO 2 @Al–MOF(MIL-68) composites with different silica contents, which showed ultrafast aniline adsorption and high recyclability [78].…”

Large Breathing Effect Induced by Water Sorption in the Exceptionally Stable Nonporous Non-MOF Crystalline Material

“…Metal-organic frameworks (MOFs) dominated the field of porous molecule-based materials due to their outstanding sorption characteristics 1,2 including the capture of small molecules (e.g. H2, CO2, CH4), [3][4][5][6][7] water, 8,9 alcohols [10][11][12][13] or compounds as large as aromatics 14,15 or proteins. 16,17 Some of the recent advancements in this field cover exceptional water harvesting applications [18][19][20][21][22] and the construction of adsorption-driven heat pumps.…”