High-Performance CO₂-Selective Hybrid Membranes by Exploiting MOF-Breathing Effects

Abstract

Conventional CO2 separation in the petrochemical industry via cryogenic distillation or aminebased absorber-stripper units is energy intensive and environmentally unfriendly. Membranebased gas separation technology, on the other hand, has contributed significantly to the development of energy-efficient systems for e.g. natural gas purification. The implementation of commercial polymeric membranes in gas separation processes is restricted by their permeabilityselectivity trade-off and by their insufficient thermal and chemical stability. Herein, we present the fabrication of Matrimid ® -based membrane loaded with a breathing metal-organic framework 2 (MOF) (NH2-MIL-53(Al)) which is capable of separating binary CO2/CH4 gas mixtures with high selectivities without sacrificing much of its CO2 permeabilities. NH2-MIL-53(Al) crystals were embedded in a polyimide (PI) matrix and the mixed-matrix membranes (MMMs) were treated at elevated temperatures (up to 350 °C) in air to trigger PI crosslinking and to create PI-MOF bonds at the interface to effectively seal the grain boundary. Most importantly, the MOF transitions from its narrow-pore form to the large-pore form during this treatment, allows the PI chains to partly penetrate the pores and crosslink with the amino functions at the pore mouth of the NH2-MIL-53(Al) and stabilizes the open-pore form of NH2-MIL-53(Al). This crosslinked MMM, with MOF pore entrances made more selective by the anchored PI-chains, achieves outstanding CO2/CH4 selectivities. This approach provides significant advancement towards the design of selective MMMs with enhanced thermal and chemical stabilities which could also be applicable for other potential applications, such as separation of hydrocarbons (olefin/paraffin or isomers), pervaporation and solvent resistant nanofiltration.

Rational Design of Halloysite Surface Chemistry for High Performance Nanotube–Thin Film Nanocomposite Gas Separation Membranes

“…Nowadays thin film composite (TFC) membranes that consist of a selective, thin polyamide (PA) top layer formed by interfacial polymerization (IP) of amine and acid chloride monomers on a porous substrate are receiving significant attention due to their advantages in different CO 2 separation and capture applications. − However, attention still needs to be paid to the well-known trade-off challenge between permeability and selectivity in TFC membranes. , …”

Light-responsive metal–organic framework sheets constructed smart membranes with tunable transport channels for efficient gas separation

“…[1][2][3][4] Hence, the exploration of new ways to separate air pollutants such as CO 2 and SO 2 is a challenging scientic and technical issue. [5][6][7] The emissions of CO 2 and SO 2 are mainly from the combustion of coal caused by industrial processes and heavy oil used by vehicles, respectively. [8][9][10] Membrane technology as one method for gas separation is promising, and has attracted the attention of researchers.…”

Molecular dynamics simulations of a hydrophilic MIL-160-based membrane demonstrate pressure-dependent selective uptake of industrially relevant greenhouse gases

“…The modular nature of MOFs with aperture size distributions of angstrom-level resolution 7,22,31 is envisioned to allow for high degrees of adsorption selectivity and permselectivity and improved process economics with reduced emissions. Previous studies showed that a mixed-matrix membrane (MMM) composed of a polyimide crosslinker and embedded with NH 2 -MIL-53, a surface-modified variant of an aluminum-based MOF, can be used for separating CH 4 from CO 2 -exhibiting increased CO 2 selectivity without significant loss of its permeability 33 . The improvements were realized in part by the presence of NH 2 groups that aided in regulating the MOF breathing mechanism and penetration of polyimide chains to provide configurational stability 33 .…”

“…Previous studies showed that a mixed-matrix membrane (MMM) composed of a polyimide crosslinker and embedded with NH 2 -MIL-53, a surface-modified variant of an aluminum-based MOF, can be used for separating CH 4 from CO 2 -exhibiting increased CO 2 selectivity without significant loss of its permeability 33 . The improvements were realized in part by the presence of NH 2 groups that aided in regulating the MOF breathing mechanism and penetration of polyimide chains to provide configurational stability 33 . Complementary, a new humidity-resistant MOF, JNU-2 has shown promise in separation of ethane (C 2 H 6 ) from ethylene (C 2 H 4 ), the single largest feedstock in the petrochemicals industry 22 .…”