title: Computational and variable-temperature infrared spectroscopic studies on carbon monoxide adsorption on zeolite Ca-A.
abstract: Carbon monoxide adsorption on LTA (Linde type 5A) zeolite Ca-A is studied by using a combination of variable-temperature infrared spectroscopy and computational methods involving periodic density functional calculations and the correlation between stretching frequency and bond length of adsorbed CO species (nu(CO)/r(CO) correlation). Based on the agreement between calculated and experimental results, the main adsorption species can be identified as bridged Ca(2+)...CO...Ca(2+) complexes formed on dual-cation sites constituted by a pair of nearby Ca(2+) cations. Two types of such species can be formed: One of them has the two Ca(2+) ions located on six-membered rings of the zeolite framework and is characterized by a C-O stretching frequency in the range of 2174-2179 cm(-1) and an adsorption enthalpy of -31 to -33 kJ mol(-1), whereas the other bridged CO species is formed between a Ca(2+) ion located on an eight-membered ring and another one on a nearby six-membered ring and is characterized by nu(CO) in the range 2183-2188 cm(-1) and an adsorption enthalpy of -46 to -50 kJ mol(-1). Ca(2+)...CO monocarbonyl complexes are also identified, and at a relatively high CO equilibrium pressure, dicarbonyl species can also be formed.
authors.affiliation: Center for Biomolecules and Complex Molecular Systems, Institute of Organic Chemistry and Biochemistry, Academy of Science of the Czech Republic, Flemingovo nám 2, 166 10 Praha 6, Czech Republic.
authors.forename: Angeles
authors.initials: A
authors.lastname: Pulido
authors.forename: Petr
authors.initials: P
authors.lastname: Nachtigall
authors.forename: Montserrat
authors.initials: M
authors.lastname: Rodríguez Delgado
authors.forename: Carlos
authors.initials: C
authors.lastname: Otero Areán
mesh_terms: D000327:Adsorption; D002248:Carbon Monoxide / Q000737:chemistry*; D003198:Computer Simulation; D008956:Models, Chemical; D013055:Spectrophotometry, Infrared; D013696:Temperature; D017641:Zeolites / Q000737:chemistry*
chemical_list: D017641:Zeolites; D002248:Carbon Monoxide