Time-Dependent CO2 Sorption Hysteresis in a One-Dimensional Microporous Octahedral Molecular Sieve

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• 作者：Laura Espinal ; Winnie Wong-Ng ; James A. Kaduk ; Andrew J. Allen ; Chad R. Snyder ; Chun Chiu ; Daniel W. Siderius ; Lan Li ; Eric Cockayne ; Anais E. Espinal ; Steven L. Suib
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：May 9, 2012
• 年：2012
• 卷：134
• 期：18
• 页码：7944-7951
• 全文大小：427K
• 年卷期：v.134,no.18(May 9, 2012)
• ISSN：1520-5126

文摘

The development of sorbents for next-generation CO₂ mitigation technologies will require better understanding of CO₂/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 CO₂ sorption of OMS-2, a well-known one-dimensional microporous octahedral molecular sieve with manganese oxide framework. Remarkably, we find that the degree of CO₂ 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 鈥済ate-keeping鈥?role of the cation in the tunnel, only allowing CO₂ molecules to enter fully into the tunnel via a highly unstable transient state when CO₂ loadings exceed 0.75 mmol/g. The energy barrier associated with the gate-keeping effect suggests an adsorption mechanism in which kinetic trapping of CO₂ is responsible for the observed hysteretic behavior.