title: Discriminative separation of gases by a "molecular trapdoor" mechanism in chabazite zeolites.
abstract: Separation of molecules based on molecular size in zeolites with appropriate pore aperture dimensions has given rise to the definition of "molecular sieves" and has been the basis for a variety of separation applications. We show here that for a class of chabazite zeolites, what appears to be "molecular sieving" based on dimension is actually separation based on a difference in ability of a guest molecule to induce temporary and reversible cation deviation from the center of pore apertures, allowing for exclusive admission of certain molecules. This new mechanism of discrimination permits "size-inverse" separation: we illustrate the case of admission of a larger molecule (CO) in preference to a smaller molecule (N(2)). Through a combination of experimental and computational approaches, we have uncovered the underlying mechanism and show that it is similar to a "molecular trapdoor". Our materials show the highest selectivity of CO(2) over CH(4) reported to date with important application to natural gas purification.
authors.affiliation: Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC), Melbourne, Australia.
authors.forename: Jin
authors.initials: J
authors.lastname: Shang
authors.forename: Gang
authors.initials: G
authors.lastname: Li
authors.forename: Ranjeet
authors.initials: R
authors.lastname: Singh
authors.forename: Qinfen
authors.initials: Q
authors.lastname: Gu
authors.forename: Kate M
authors.initials: KM
authors.lastname: Nairn
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Bastow
authors.forename: Nikhil
authors.initials: N
authors.lastname: Medhekar
authors.forename: Cara M
authors.initials: CM
authors.lastname: Doherty
authors.forename: Anita J
authors.initials: AJ
authors.lastname: Hill
authors.forename: Jefferson Z
authors.initials: JZ
authors.lastname: Liu
authors.forename: Paul A
authors.initials: PA
authors.lastname: Webley