Xiangyu Guo

Fabrication of mixed-matrix membrane containing metal–organic framework composite with task-specific ionic liquid for efficient CO2 separation

Mixed-matrix membranes (MMMs) have exhibited advantages in membrane-based gas separation in recent years, however, there is still intensive demand for the development of a proper method to design effective fillers to further enhance the gas separation performance of MMMs. In this work, a nanoporous material to selectively facilitate CO2 transport was proposed through the loading of a task-specific ionic liquid (TSIL) into a metal–organic framework (MOF). [C3NH2bim][Tf2N] and NH2-MIL-101(Cr) were selected as a demonstrative TSIL and MOF, respectively. The amine-containing TSIL worked as a selective CO2 transport carrier, which can be beneficial for the improvement of CO2 permeability and CO2/N2 selectivity. Simultaneously, NH2-MIL-101(Cr) is an appropriate porous host material that can control the good dispersion of TSIL and can effectively expose more active adsorption sites of the TSIL. Meanwhile, the amine-containing porous MOF is helpful for rapid CO2 transport and further increases the CO2 permeability. We further incorporated the porous composite into PIM-1 to fabricate MMMs with different loadings. The prepared TSIL@NH2-MIL-101(Cr)/PIM-1 membrane exhibits largely improved gas permeability and selectivity for CO2/N2 separation, with CO2 permeation values of 2979 Barrer and a CO2/N2 separation selectivity of 37 at 5 wt% loading. Compared with NH2-MIL-101(Cr)/PIM-1 and PIM-1 membranes, the CO2/N2 separation selectivity was increased by 116% and 119%, respectively, at the same loading.

Recovery of acetone from aqueous solution by ZIF-7/PDMS mixed matrix membranes

Metal–organic frameworks (MOFs) have exhibited promising applications in gas and liquid separation. As a subclass of MOFs, zeolitic imidazolate frameworks (ZIFs) are attracting more and more interest because of their unique thermal and chemical stability. One of the representative ZIFs, ZIF-7, has super-hydrophobic pores, making it a perfect filler in polymer membranes for recovering acetone from fermentation broths. In this study, mixed matrix membranes (MMMs) based on ZIF-7 and polydimethylsiloxane (PDMS) were prepared, which display improved acetone–water total flux and separation factors simultaneously compared with a pure PDMS membrane. The separation factor can reach up to 39.1 with a high flux of 1236.8 g m−2 h−1 at 333 K, which is the highest value among those reported up to now to the best of our knowledge.

Synthesis of MIL-88B(Fe)/Matrimid mixed-matrix membranes with high hydrogen permselectivity

A cheap and biocompatible metal–organic framework MIL-88B(Fe) (MIL = Material Institut Lavoisier) was synthesized and incorporated into Matrimid® 5218 to fabricate mixed-matrix membranes (MMMs) for gas separation. Separation performances of the MIL-88B(Fe)/Matrimid MMMs were tested for the single gas permeation of H2 and CH4 as well as the mixture gas separation of an equimolar binary H2–CH4 mixture. Due to the molecular sieving effect, the incorporation of MIL-88B(Fe) can enhance H2 permeability but hinder the transport of CH4 in MIL-88B(Fe)/Matrimid MMMs, thus resulting in enhanced separation selectivity of H2–CH4. At 298 K and ΔP = 3.0 bar, compared with those of a pure polymeric membrane, the H2 permeability and H2–CH4 mixture separation factor of MMMs with a MIL-88B(Fe) loading of 10% increased by 16% and 66%, respectively. In addition, the operation temperature has a significantly positive effect on the separation of a H2–CH4 mixture.