Determination of Composition Range for 鈥淢olecular Trapdoor鈥?Effect in Chabazite Zeolite

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• 作者：Jin Shang ; Gang Li ; Ranjeet Singh ; Penny Xiao ; Jefferson Z. Liu ; Paul A. Webley
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：June 20, 2013
• 年：2013
• 卷：117
• 期：24
• 页码：12841-12847
• 全文大小：308K
• 年卷期：v.117,no.24(June 20, 2013)
• ISSN：1932-7455

文摘

Highly selective separation of small molecules, such as CO₂, N₂, and CH₄, is difficult to achieve if all of the molecules can access the internal surface so that the selectivity depends only on differences in interaction of these molecules with the surface. Recently, we reported on a 鈥渕olecular trapdoor鈥?mechanism (Shang, J.; et al. J. Am. Chem. Soc.2012, 134, 19246鈥?9253), which provides a record high selectivity through a guest-induced cation deviation process where the adsorbent exclusively admits 鈥渟trong鈥?molecules (e.g., CO₂ and CO) but excludes 鈥渨eak鈥?ones (e.g., N₂ and CH₄). In this study, we have investigated the range of zeolite compositions (varying Si/Al and cation type) for which a trapdoor effect is present and summarize this composition range with a simple 鈥渞ule of thumb鈥? Cation density and cation type are the controlling factors in achieving the molecular trapdoor effect on chabazites. Specifically, the 鈥渞ule鈥?requires every pore aperture connecting the supercages to accommodate one door-keeping cation of an appropriate type. This 鈥渞ule鈥?will help guide the synthesis of 鈥渢rapdoor鈥?chabazite adsorbents for the deployment of carbon capture as well as help the development of molecular trapdoor adsorbents/membranes for other small-pore zeolites, such as RHO, LTA, and other porous materials.