Post-synthetic structural processing in a metal-organic framework material as a mechanism for exceptional CO2/N2 selectivity

Witold M Bloch, Ravichandar Babarao, Matthew Roland Hill, Christian J Doonan, Christopher James Sumby

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Here we report the synthesis and ceramic-like processing of a new metal-organic framework (MOF) material, [Cu(bcppm)H2O], that shows exceptionally selective separation for CO2 over N-2 (ideal adsorbed solution theory, S-ads = 590). [Cu(bcppm)H2O]center dot xS was synthesized in 82 yield by reaction of Cu(NO3)(2)center dot 2.5H(2)O with the link bis(4-(4-carboxyphenyl)-1H-pyrazolyl)methane (H(2)bcppm) and shown to have a two-dimensional 4(4)-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.
Original languageEnglish
Pages (from-to)10441 - 10448
Number of pages8
JournalJournal of the American Chemical Society
Issue number28
Publication statusPublished - 2013
Externally publishedYes

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