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–O_OH interactions in Cu₆/MOR facilitate ethanol dehydration. Conversely, Cu₃O₃/MOR exhibits pronounced Cu₃O₃–H_OH 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.