Gas Permeability Of Mixed Matrix Membranes Research Articles

Computational Investigation of Dual Filler-Incorporated Polymer Membranes for Efficient CO2 and H2 Separation: MOF/COF/Polymer Mixed Matrix Membranes.

Mixed matrix membranes (MMMs) composed of two different fillers such as metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs) embedded into polymers provide enhanced gas separation performance. Since it is not possible to experimentally consider all possible combinations of MOFs, COFs, and polymers, developing computational methods is urgent to identify the best performing MOF-COF pairs to be used as dual fillers in polymer membranes for target gas separations. With this motivation, we combined molecular simulations of gas adsorption and diffusion in MOFs and COFs with theoretical permeation models to calculate H2, N2, CH4, and CO2 permeabilities of almost a million types of MOF/COF/polymer MMMs. We focused on COF/polymer MMMs located below the upper bound due to their low gas selectivity for five industrially important gas separations, CO2/N2, CO2/CH4, H2/N2, H2/CH4, and H2/CO2. We further investigated whether these MMMs could exceed the upper bound when a second type of filler, a MOF, was introduced into the polymer. Many MOF/COF/polymer MMMs were found to exceed the upper bounds showing the promise of using two different fillers in polymers. Results showed that for polymers having a relatively high gas permeability (≥104 barrer) but low selectivity (≤2.5) such as PTMSP, addition of the MOF as the second filler can have a dramatic effect on the final gas permeability and selectivity of the MMM. Property-performance relations were analyzed to understand how the structural and chemical properties of the fillers affect the permeability of the resulting MMMs, and MOFs having Zn, Cu, and Cd metals were found to lead to the highest increase in gas permeability of MMMs. This work highlights the significant potential of using COF and MOF fillers in MMMs to achieve better gas separation performances than MMMs with one type of filler, especially for H2 purification and CO2 capture applications.

The Potential of Lipid-polymer Nanoparticle as Epigenetic and ROS Control Approaches for COPD

The fabrication of mixed matrix membranes (MMMs), with a view to using them for gas separation applications, such as the capturing and separating carbon dioxide, oxygen, or nitrogen from air, and natural gas separation, has been thoroughly explored. Here we report on MMMs containing surface-modified non-porous pearl-necklace nanoparticles (P-NP), which were synthesized by connecting together approximately six spherical nanoparticles. The gas permeability of MMMs containing P-NPs increased with increasing P-NP concentration, and the increase was associated with the formation of micro- and meso-pores, which were confirmed using the nitrogen-adsorption/desorption and 129Xe NMR measurements. The permeabilities of an MMM containing 50 wt% P-NP for CO2, O2, N2, and CH4 were 15200, 2850, 916, and 1340 Barrer, respectively. This MMM also had a CO2/N2 selectivity of 16.6, CO2/CH4 selectivity of 11.4 and O2/N2 selectivity of 3.1. The gas permeation data of the resulting MMM was above the 2008 Robeson upper bound line for CO2/N2, CO2/CH4, and O2/N2 gas pairs. This strategy, using anisotropic nanoparticles with a large gas permeable space, has the potential to be applied to the fabrication of MMMs for gas separation.

Mixed matrix membranes comprising a polymer of intrinsic microporosity loaded with surface-modified non-porous pearl-necklace nanoparticles

The fabrication of mixed matrix membranes (MMMs), with a view to using them for gas separation applications, such as the capturing and separating carbon dioxide, oxygen, or nitrogen from air, and natural gas separation, has been thoroughly explored. Here we report on MMMs containing surface-modified non-porous pearl-necklace nanoparticles (P-NP), which were synthesized by connecting together approximately six spherical nanoparticles. The gas permeability of MMMs containing P-NPs increased with increasing P-NP concentration, and the increase was associated with the formation of micro- and meso-pores, which were confirmed using the nitrogen-adsorption/desorption and 129Xe NMR measurements. The permeabilities of an MMM containing 50 wt% P-NP for CO2, O2, N2, and CH4 were 15200, 2850, 916, and 1340 Barrer, respectively. This MMM also had a CO2/N2 selectivity of 16.6, CO2/CH4 selectivity of 11.4 and O2/N2 selectivity of 3.1. The gas permeation data of the resulting MMM was above the 2008 Robeson upper bound line for CO2/N2, CO2/CH4, and O2/N2 gas pairs. This strategy, using anisotropic nanoparticles with a large gas permeable space, has the potential to be applied to the fabrication of MMMs for gas separation.

Mixed-matrix membranes incorporated with porous shape-persistent organic cages for gas separation

There has been much recent interest in the use of porous materials derived from self-assembling, shape-persistent organic cages due to their solubility and easy post-synthetic modification. Herein we report the preparation of novel mixed-matrix membranes (MMMs) employing the porous organic cage Noria and its derivatives Noria-Boc and Noria-COtBu as the fillers, and a fluorine containing polyimide, 6FDA-DAM, as the polymeric matrix. The physical structures and properties of Noria and its derivatives were measured and investigated. Noria with substituents of Boc (cleaved by thermal treatment during the process of membrane fabrication) and COtBu groups tend to show much better compatibility with polyimide than Noria itself, resulting in homogeneous dispersion of nanoaggregates and fine adhesion between the two phases in the derived Noria/6FDA-DAM and Noria-COtBu/6FDA-DAM MMMs. Gas permeation tests revealed that Noria and Noria-COtBu nanoparticles have different effect on gas separation performance of MMMs. The introduction of Noria into 6FDA-DAM tends to enhance CO2/CH4 selectivity and thus improve its gas separation properties, though a decrease in the observed permeability could be observed. In contrast, the introduction of Noria-COtBu with higher surface area and larger pores tends to increase the free volume and gas permeability of MMMs. These results show that both the morphology and the gas separation properties of MMMs could be tuned by tailoring the structures of porous organic cages.

The impact of water vapor on CO2 separation performance of mixed matrix membranes

A series of mixed matrix membranes (MMMs) using nanoparticles involving carbons, porous organic polymers and metal organic frameworks (MOFs) were prepared to investigate the impact of water vapor on CO2 separation performance. The water uptake of MMMs using hydrophilic MOFs increased relative to more hydrophobic particles such as the porous organic polymers and carbons and this trend was reflected in the water vapor permeability, which varied by a factor of three between the hydrophobic and hydrophilic MMMs. These changes in water vapor permeability were strongly correlated with the water solubility, indicating that it is this solubility that is the controlling parameter. The calculated water diffusivity was consistent with previously published results. The gas permeability of MMMs in the presence of water vapor was also strongly affected by the nanoparticle hydrophobicity, with membranes composed of hydrophobic fillers out-performing hydrophilic fillers of comparable porosity. However in general, the differences in performance between MMMs and the pure polymer narrowed in the presence of water vapor.

Post-treatment effect on gas separation property of mixed matrix membranes containing metal organic frameworks

In this work a series of mixed matrix membranes (MMMs) containing metal organic frameworks (MOFs) were fabricated to investigate the influence of post-treatment on their gas separation properties. It was revealed that gas permeabilities increased considerably as treatment temperature increased from 150°C to 180°C and remained almost unchanged after 200°C; gas permeability of MMMs from 200°C treatment was about 3 times higher when compared with MMMs treated at 150°C. From results of physical characterization including TGA, XRD, SEM, ATR-FTIR and nitrogen absorption it was inferred that higher temperature treatment induced gas permeability increase should be mainly attributed to more effective removal of residual solvent in micro-pores of MOFs; and gas permeation properties of MMMs with different treatment durations from 24h to 96h further confirmed our conclusion. This heat treatment induced permeability increase phenomenon was further verified by varying the polymer and MOF combinations. At the end Cu3(BTC)2/ODPA–TMPDA MMMs with different MOF loadings were prepared and the one with best performance appeared at 40wt% loading: a dramatic increase of CO2 permeability from 47.7Barrer to 260.7Barrer with almost unchanged CO2/CH4 selectivity from 29.26 to 27.75.