Enhanced Interfacial Interaction and CO₂ Separation Performance of Mixed Matrix Membrane by Incorporating Polyethylenimine-Decorated Metal–Organic Frameworks

Abstract

Polyethylenimine (PEI) was immobilized by MIL-101(Cr) (∼550 nm) via a facile vacuum-assisted method, and the obtained PEI@MIL-101(Cr) was then incorporated into sulfonated poly(ether ether ketone) (SPEEK) to fabricate mixed matrix membranes (MMMs). High loading and uniform dispersion of PEI in MIL-101(Cr) were achieved as demonstrated by ICP, FT-IR, XPS, and EDS-mapping. The PEI both in the pore channels and on the surface of MIL-101(Cr) improved the filler-polymer interface compatibility due to the electrostatic interaction and hydrogen bond between sulfonic acid group and PEI, and simultaneously rendered abundant amine carriers to facilitate the transport of CO2 through reversible reaction. MMMs were evaluated in terms of gas separation performance, thermal stability, and mechanical property. The as-prepared SPEEK/PEI@MIL-101(Cr) MMMs showed increased gas permeability and selectivity, and the highest ideal selectivities for CO2/CH4 and CO2/N2 were 71.8 and 80.0 (at a CO2 permeability of 2490 Barrer), respectively. Compared with the membranes doped with unfilled MIL-101(Cr), the ideal selectivities of CO2/CH4 and CO2/N2 for PEI@MIL-101(Cr)-doped membranes were increased by 128.1 and 102.4 %, respectively, at 40 wt % filler loading, surpassing the 2008 Robeson upper bound line. Moreover, the mechanical property and thermal stability of SPEEK/PEI@MIL-101(Cr) were enhanced.

Multifunctional metal–organic frameworks: from academia to industrial applications

“…[135][136][137][138][139][140] The Ag@MIL-101 porous material, with different Ag loadings, was prepared by Liu et al 134 via a simple impregnation-reduction methodology immobilizing Ag nanoparticles into the cages of MIL-101(Cr). This material exhibits outstanding bifunctionality: i) on the one hand, Ag@MIL-101 is capable to retain CO 2 in its porous structure; and ii) on the other hand, the CO 2 is converted into compounds with carboxylic acid groups through C-H bond activation of the terminal alkynes.…”

Physical aging in glassy mixed matrix membranes; tuning particle interaction for mechanically robust nanocomposite films

“…21,22 High additive loading generally causes severe embrittlement, though a few recent studies have reported stable MMM films through targeted polymer-additive interactions. 12,[23][24][25][26] Similarly, adsorption of polymer chains in super-porous additives have been used to stop age-related permselectivity loss in glassy MMM. 12,[27][28][29] To date, there is no complete model describing the complex polymer-additive interactions responsible for MMM properties and little is known about how additive incorporation affects the mechanical resilience of polymer nanocomposites with aging.…”

Mixed Matrix Membranes for Gas Separation Applications

“…15,20,21,26,32,37,69,[135][136][137][138] Essentially, these properties are determined by the interactions among gas molecules, polymers and fillers, which can be computed using molecular simulation with verified force fields accurately. Molecular modeling can reach tens of nanoseconds and nanometers at maximum, which is large enough to compute the gas transportation in the homogenous phases like pure polymer membranes and inorganic porous fillers.…”