A thorough mechanistic study of ethanol, acetaldehyde, and ethylene adsorption on Cu-MOR via DFT analysis.

Abstract

A comprehensive study combining the density functional theory (DFT) and ab initio thermodynamic analysis was conducted to unravel the active sites and adsorption mechanisms of ethanol, acetaldehyde, and ethylene on various copper-modified mordenite (Cu-MOR) configurations, including Cu3/MOR, Cu3O3/MOR, and Cu6/MOR. This research involved an exhaustive exploration of structural and formation energies, revealing that the formation energies of these structures are temperature-dependent. Despite all three structures thermodynamically accommodating ethanol adsorption, their respective adsorption mechanisms differ significantly. In Cu3/MOR, weak van der Waals interactions predominate, while strong Cu-OOH interactions in Cu6/MOR facilitate ethanol dehydration. Conversely, Cu3O3/MOR exhibits pronounced Cu3O3-HOH interactions that favor ethanol dehydrogenation. Notably, Cu3O3/MOR displays robust ethylene adsorption, which enhances the potential for further ethylene activation. In-depth Bader charge and density of states analyses underscore the varying strengths and electronic characteristics of these interactions. This research provides a theoretical foundation for the design of highly efficient Cu-MOR catalysts tailored for the selective conversion of ethanol.