Post-synthetic Structural Processing in a Metal鈥揙rganic Framework Material as a Mechanism for Exceptional CO2/N2 Selectivity

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• 作者：Witold M. Bloch ; Ravichandar Babarao ; Matthew R. Hill ; Christian J. Doonan ; Christopher J. Sumby
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：July 17, 2013
• 年：2013
• 卷：135
• 期：28
• 页码：10441-10448
• 全文大小：493K
• 年卷期：v.135,no.28(July 17, 2013)
• ISSN：1520-5126

文摘

Here we report the synthesis and ceramic-like processing of a new metal鈥搊rganic framework (MOF) material, [Cu(bcppm)H₂O], that shows exceptionally selective separation for CO₂ over N₂ (ideal adsorbed solution theory, S_ads = 590). [Cu(bcppm)H₂O]路xS was synthesized in 82% yield by reaction of Cu(NO₃)₂路2.5H₂O with the link bis(4-(4-carboxyphenyl)-1H-pyrazolyl)methane (H₂bcppm) and shown to have a two-dimensional 4⁴-connected structure with an eclipsed arrangement of the layers. Activation of [Cu(bcppm)H₂O] generates a pore-constricted version of the material through concomitant trellis-type pore narrowing (b-axis expansion and c-axis contraction) and a 2D-to-3D transformation (a-axis contraction) to give the adsorbing form, [Cu(bcppm)H₂O]-ac. The pore contraction process and 2D-to-3D transformation were probed by single-crystal and powder X-ray diffraction experiments. The 3D network and shorter hydrogen-bonding contacts do not allow [Cu(bcppm)H₂O]-ac to expand under gas loading across the pressure ranges examined or following re-solvation. This exceptional separation performance is associated with a moderate adsorption enthalpy and therefore an expected low energy cost for regeneration.