Interaction of atmospheric gases with ETS-10: A DFT study

Abstract

Density functional theory (DFT) was used to optimize the geometries and calculate the enthalpies for the interactions between polar (H2O), quadrupolar (CO2 and N2), and apolar (H2 and CH4) atmospheric gases with a cluster model of the Engelhard titanosilicate ETS-10 having sodium extra framework cations (Na-ETS-10). The DFT calculations were performed with different exchange–correlation functionals and were corrected for the basis set superposition error with the counterpoise method. The calculated enthalpies for the interaction of the five gases with Na-ETS-10 decrease in the order H2O>CO2≫N2≈CH4>H2 and compare well with experimental data available in the literature. The enthalpies calculated at the M06-L/6-31++G(d,p) level of theory for the two extreme cases, i.e., strongest and weakest interactions, are −60.6kJ/mol (H2O) and −12.2kJ/mol (H2). Additionally, the calculated vibrational frequencies are in very good agreement, within the approximations of the method, with the characteristic vibrational modes of ETS-10 and of the interactions of gases with Na+ in the 12-membered channel in ETS-10.