FTIR study of the low-temperature adsorption and co-adsorption of CO and N2 on NaY zeolite: evidence of simultaneous coordination of two molecules to one Na+ site

Na+ cations in SII positions in NaY zeolite are able, at 85 K, to coordinate two CO or N2 molecules as well as to form mixed Na+(CO)(N2) species. In all these complexes, the ligands behave as independent oscillators. The Na+(15N2)2 species (IR band at 2255.5 cm−1) are typical at equilibrium pressures >30 Pa, whereas the respective linear complexes (band at 2258.5 cm−1) prevail at lower pressures. The dicarbonyls (band at 2163 cm−1) are the principal complexes observed at CO pressures higher than ca. 0.1 Pa and evacuation converts them to linear carbonyls (band at 2174 cm−1). The mixed Na+(CO)(15N2) complexes [ν(C–O) at 2167 cm−1 and ν(15N–15N) at 2254 cm−1] are produced during CO and 15N2 co-adsorption and easily lose one 15N2 ligand, being thus converted to linear carbonyls.