Abstract Variable‐temperature in situ ATR‐FTIR spectra are presented for the porous spin‐crossover compounds [Fe(pyrazine)Ni(CN) 4 ] and [Fe(pyrazine)Pt(CN) 4 ] under CO 2 pressures of up to 8 bar. Significant shifts in the ν 3 and ν 2 IR absorption bands of adsorbed CO 2 are observed as the host materials undergo transition between low‐ and high‐spin states. Computational models used to determine the packing arrangement of CO 2 within the pore structures show a preferred orientation of one of the adsorbed CO 2 molecules with close O=C=O ··· H contacts with the pyrazine pillar ligands. The interaction is a consequence of the commensurate distance of the inter‐pyrazine separations and the length of the CO 2 molecule, which allows the adsorbed CO 2 to effectively bridge the pyrazine pillars in the structure. The models were used to assign the distinct shifts in the IR absorption bands of the adsorbed CO 2 that arise from changes in the O=C=O ··· H contacts that strengthen and weaken in correlation with changes in the Fe–N bond lengths as the spin state of Fe changes. The results indicate that spin‐crossover compounds can function as a unique type of flexible sorbent in which the pore contractions associated with spin transition can affect the strength of CO 2 –host interactions.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Reaction of an amphiphillic pentacyanoiron(III) complex with aqueous cobalt(II) ions at the air-water interface yielded a two-dimensional (2D) cobalt(II)-iron(III) cyanide network. The Langmuir monolayers were characterized by pressure vs. area isothenns. The cyanide-bridged networks were transferred to solid supports by the Langmuir-Blodgett technique. Multilayer films were structurally characterized by FT-IR and UV-VIS spectroscopies, X-ray diffraction and SQUID magnetometry.
Flexibilität sorgt für Selektivität: Die selektive Adsorption von CO2 aus Gasgemischen mit N2, CH4 und N2O in einem dynamischen porösen Koordinationspolymer (siehe Monomerstruktur) wurde durch ATR-FTIR-Spektroskopie, Gaschromatographie und Kleinwinkelröntgenstreuung untersucht. Alle drei Techniken bestätigen eine hoch selektive Adsorption von CO2 aus CO2/CH4- und CO2/N2-Gemischen bei 30 °C und keine Selektivität beim CO2/N2O-System. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
The structural and microstructural responses of a model metal–organic framework material, Ni(3-methyl-4,4′-bipyridine)[Ni(CN) 4 ] (Ni-BpyMe or PICNIC-21), to CO 2 adsorption and desorption are reported for in situ small-angle X-ray scattering and X-ray diffraction measurements under different gas pressure conditions for two technologically important cases. These conditions are single or dual gas flow (CO 2 with N 2 , CH 4 or H 2 at sub-critical CO 2 partial pressures and ambient temperatures) and supercritical CO 2 (with static pressures and temperatures adjusted to explore the gas, liquid and supercritical fluid regimes on the CO 2 phase diagram). The experimental results are compared with density functional theory calculations that seek to predict where CO 2 and other gas molecules are accommodated within the sorbent structure as a function of gas pressure conditions, and hence the degree of swelling and contraction in the associated structure spacings and void spaces. These predictions illustrate the insights that can be gained concerning how such sorbents can be designed or modified to optimize the desired gas sorption properties relevant to enhanced gas recovery or to addressing carbon dioxide reduction through carbon mitigation, or even direct air capture of CO 2 .
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