Adsorption of NO, NO2, CO, H2O and CO2 over isolated monovalent cations in faujasite zeolite: a periodic DFT investigation

Abstract

Using periodic density functional theory combined with advanced dispersion correction schemes, the adsorption of NO, NO2, CO, H2O and CO2 has been investigated for various cation-exchanged faujasite zeolites. In the context of preventing harmful releases from diesel engines in confined environment, our aim was to find a suitable material able to selectively trap NO, NO2 and CO toward H2O and CO2 which are also present in the exhaust gas and could inhibit adsorption of targeted species. In order to identify the most promising adsorbent materials, we have undertaken a full screening of monovalent cations which can be incorporated into the zeolite and find that Cu+ presents the best adsorption selectivity, followed by Ag+. However, the analysis of the bonds stretching upon adsorption revealed that Cu+, differently from Ag+, activates the N–O bonds in NO and NO2, which might lead to undesirable by-products during the adsorption process.