FTIR spectroscopy of carbon dioxide adsorbed on sodium- and magnesium-exchanged ETS-10 molecular sieves

Abstract

The adsorption of carbon dioxide on sodium- and magnesium-exchanged ETS-10 molecular sieves was investigated by FTIR spectroscopy. CO₂ was found to adsorb reversibly onto the charge-balancing cations with formation of linear end-on adducts of the type M⋯OCO (with M = Na⁺ or Mg²⁺). Such adducts are characterised by intense ν₃ bands at 2353 and 2365 cm⁻¹, for CO₂ interacting with Na⁺ and Mg²⁺, respectively. More interestingly, carbon dioxide was also found to form different carbonate-like species upon adsorption on the Na-ETS-10 (and, to a minor extent, also on Mg-ETS-10), which are the origin of the activity of ETS-10 in heterogeneous base-catalysed processes.