Abstract
Adsorption of CO2 in K-FER zeolite is investigated by a combination of variable-temperature IR spectroscopy and periodic DFT calculations. Calculated adsorption enthalpies for CO2 adsorption complexes on single extra-framework K+ sites and on dual-cation sites where CO2 interacts simultaneously with two extra-framework K+ cations (-40 and -44 kJ/mol, respectively) are in excellent agreement with experimental values.
The analysis of effects on the frequency of the asymmetric CO2 stretching mode nu3 shows that polarization of CO2 by the K+ cation leads to an increase in nu3, while the interaction of CO2 with the zeolite framework leads to a decrease in nu3. Calculations show that the dispersion interaction does not affect the vibrational frequency of adsorbed CO2.