title: Post-synthetic structural processing in a metal-organic framework material as a mechanism for exceptional CO2/N2 selectivity.
abstract: 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 N2 (ideal adsorbed solution theory, S(ads) = 590). [Cu(bcppm)H2O]·xS was synthesized in 82% yield by reaction of Cu(NO3)2·2.5H2O with the link bis(4-(4-carboxyphenyl)-1H-pyrazolyl)methane (H2bcppm) 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.
authors.affiliation: School of Chemistry and Physics, The University of Adelaide, Adelaide, South Australia 5005, Australia.
authors.forename: Witold M
authors.initials: WM
authors.lastname: Bloch
authors.forename: Ravichandar
authors.initials: R
authors.lastname: Babarao
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Hill
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Doonan
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Sumby
mesh_terms: D002245:Carbon Dioxide / Q000302:isolation & purification*; D003300:Copper / Q000737:chemistry; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D015394:Molecular Structure; D009584:Nitrogen / Q000302:isolation & purification*; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D002245:Carbon Dioxide; D003300:Copper; D009584:Nitrogen