Variable-temperature IR spectroscopic and theoretical studies on CO2 adsorbed in zeolite K-FER.

Adsorption of CO(2) in K-FER zeolite is investigated by a combination of variable-temperature IR spectroscopy and periodic DFT calculations augmented for description of dispersion interactions. Calculated adsorption enthalpies for CO(2) adsorption complexes on single extra-framework K(+) sites and on dual-cation sites where CO(2) interacts simultaneously with two extra-framework K(+) cations (-40 and -44 kJ mol(-1), respectively) are in excellent agreement with experimental values. The analysis of effects on the frequency of the asymmetric CO(2) stretching mode ν(3) shows that polarization of CO(2) by the K(+) cation leads to an increase in ν(3), while the interaction of CO(2) with the zeolite framework leads to a decrease in ν(3).