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 N-2), and apolar (H-2 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 >> N-2 approximate to CH4 > H-2 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 60.6 kl/mol ((HO)-O-2) and 12.2 kJ/mol (H2O). 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. (C) 2014 Elsevier Inc. All rights reserved.