title: Time-dependent CO2 sorption hysteresis in a one-dimensional microporous octahedral molecular sieve.
abstract: The development of sorbents for next-generation CO(2) mitigation technologies will require better understanding of CO(2)/sorbent interactions. Among the sorbents under consideration are shape-selective microporous molecular sieves with hierarchical pore morphologies of reduced dimensionality. We have characterized the non-equilibrium CO(2) sorption of OMS-2, a well-known one-dimensional microporous octahedral molecular sieve with manganese oxide framework. Remarkably, we find that the degree of CO(2) sorption hysteresis increases when the gas/sorbent system is allowed to equilibrate for longer times at each pressure step. Density functional theory calculations indicate a "gate-keeping" role of the cation in the tunnel, only allowing CO(2) molecules to enter fully into the tunnel via a highly unstable transient state when CO(2) loadings exceed 0.75 mmol/g. The energy barrier associated with the gate-keeping effect suggests an adsorption mechanism in which kinetic trapping of CO(2) is responsible for the observed hysteretic behavior.
authors.affiliation: Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA. laura.espinal@nist.gov
authors.forename: Laura
authors.initials: L
authors.lastname: Espinal
authors.forename: Winnie
authors.initials: W
authors.lastname: Wong-Ng
authors.forename: James A
authors.initials: JA
authors.lastname: Kaduk
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Allen
authors.forename: Chad R
authors.initials: CR
authors.lastname: Snyder
authors.forename: Chun
authors.initials: C
authors.lastname: Chiu
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Siderius
authors.forename: Lan
authors.initials: L
authors.lastname: Li
authors.forename: Eric
authors.initials: E
authors.lastname: Cockayne
authors.forename: Anais E
authors.initials: AE
authors.lastname: Espinal
authors.forename: Steven L
authors.initials: SL
authors.lastname: Suib