Effect of Spin-Crossover-Induced Pore Contraction on CO₂–Host Interactions in the Porous Coordination Polymers [Fe(pyrazine)M(CN)₄] (M = Ni, Pt)

Journal Article · Fri Feb 01 00:00:00 EST 2013 · European Journal of Inorganic Chemistry (Online)

DOI:https://doi.org/10.1002/ejic.201201265· OSTI ID:1129487

Culp, Jeffrey T; Chen, De-Li; Liu, Jinchen; Chirdon, Danielle; Kauffman, Kristi; Goodman, Angela; Johnson, J Karl

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 CO₂ pressures of up to 8 bar. Significant shifts in the ν₃ and ν₂ IR absorption bands of adsorbed CO₂ are observed as the host materials undergo transition between low- and high-spin states. Computational models used to determine the packing arrangement of CO₂ within the pore structures show a preferred orientation of one of the adsorbed CO₂ 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 CO₂ molecule, which allows the adsorbed CO₂ 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 CO₂ 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 CO₂–host interactions.

• Research Organization: National Energy Technology Lab. (NETL), Pittsburgh, PA, and Morgantown, WV (United States). In-house Research
• Sponsoring Organization: USDOE Office of Fossil Energy (FE)
• DOE Contract Number: DE-FE0004000
• OSTI ID: 1129487
• Report Number(s): A-CONTR-PUB-012
• Journal Information: European Journal of Inorganic Chemistry (Online), Vol. 2013, Issue 4; ISSN 1099-0682
• Publisher: ChemPubSoc Europe
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
carbon capture
CO2 Adsorption
flexible coordination polymer
metal organic framework
IR spectroscopy
computational chemistry
Metal–organic frameworks / Spin crossover / Density functional calculations / IR spectroscopy / Adsorption