title: Analysis of high and selective uptake of CO2 in an oxamide-containing {Cu2(OOCR)4}-based metal-organic framework.
abstract: The porous framework [Cu2(H2O)2L]⋅4 H2O⋅2 DMA (H4L = oxalylbis(azanediyl)diisophthalic acid; DMA = N,N-dimethylacetamide), denoted NOTT-125, is formed by connection of {Cu2(RCOO)4} paddlewheels with the isophthalate linkers in L(4-). A single crystal structure determination reveals that NOTT-125 crystallises in monoclinic unit cell with a = 27.9161(6), b = 18.6627(4) and c = 32.3643(8) Å, β = 112.655(3)°, space group P2(1)/c. The structure of this material shows fof topology, which can be viewed as the packing of two types of cages (cage A and cage B) in three-dimensional space. Cage A is constructed from twelve {Cu2(OOCR)4} paddlewheels and six linkers to form an ellipsoid-shaped cavity approximately 24.0 Å along its long axis and 9.6 Å across its central diameter. Cage B consists of six {Cu2(OOCR)4} units and twelve linkers and has a spherical diameter of 12.7 Å taking into account the van der Waals radii of the atoms. NOTT-125 incorporates oxamide functionality within the pore walls, and this, combined with high porosity in desolvated NOTT-125a, is responsible for excellent CO2 uptake (40.1 wt % at 273 K and 1 bar) and selectivity for CO2 over CH4 or N2. Grand canonical Monte Carlo (GCMC) simulations show excellent agreement with the experimental gas isotherm data, and a computational study of the specific interactions and binding energies of both CO2 and CH4 with the linkers in NOTT-125 reveals a set of strong interactions between CO2 and the oxamide motif that are not possible with a single amide.
authors.affiliation: School of Chemistry, University of Nottingham, Nottingham NG7 2RD (UK).
authors.forename: Nada H
authors.initials: NH
authors.lastname: Alsmail
authors.forename: Mikhail
authors.initials: M
authors.lastname: Suyetin
authors.forename: Yong
authors.initials: Y
authors.lastname: Yan
authors.forename: Rafel
authors.initials: R
authors.lastname: Cabot
authors.forename: Cristina P
authors.initials: CP
authors.lastname: Krap
authors.forename: Jian
authors.initials: J
authors.lastname: Lü
authors.forename: Timothy L
authors.initials: TL
authors.lastname: Easun
authors.forename: Elena
authors.initials: E
authors.lastname: Bichoutskaia
authors.forename: William
authors.initials: W
authors.lastname: Lewis
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Blake
authors.forename: Martin
authors.initials: M
authors.lastname: Schröder
keywords: CO2; carboxylic acid; copper; isophthalate; metal-organic frameworks