Hydrogen adsorption on the zeolite Ca-A: DFT and FT-IR investigation

• Published in: Chemical physics letters Vol. 477; no. 1; pp. 139 - 143
• Main Authors: Areán, C. Otero, Palomino, G. Turnes, Carayol, M.R. Llop, Pulido, A., Rubeš, M., Bludský, O., Nachtigall, P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 28-07-2009
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2009.06.058

H
2 adsorption in Ca-A takes place on Ca
2+ cations located in the six-member ring in the supercage.
Adsorption of H
2 on the zeolite Ca-A was investigated by a combination of variable temperature IR spectroscopy and calculations at the periodic DFT level. Calculations showed that adsorption complexes can be formed on two types of adsorption sites: Ca
2+ in the center of six-member rings and Ca
2+ in eight-member rings. Only the former adsorption complexes were experimentally observed in IR spectra; they are characterized by H–H stretching frequency of 4083
cm
−1 and Δ
H
0
=
−12
kJ/mol in agreement with calculated results. The most likely explanation for not observing the adsorption complex on Ca
2+ in 8-member rings is that the geometry of the complex does not render the H–H stretching mode IR active.