Ethanol Conversion on Cyclic (MO<sub>3</sub>)<sub>3</sub> (M = Mo, W) Clusters

The reactions of ethanol (CH<sub>3</sub>CH<sub>2</sub>OD) over cyclic (MO<sub>3</sub>)<sub>3</sub> (M = Mo, W) clusters were studied experimentally and computationally. The cyclic clusters were prepared by sublimation of MoO<sub>3</sub> and WO<sub>3</sub> powders in a vacuum. To evaluate the cluster activity in dehydration, dehydrogenation, and condensation reactions, they were suspended in an ethanol matrix on an inert substrate, graphene monolayer on Pt(111). The reaction products formed upon heating were followed and quantified using temperature-programmed desorption. The experimental results were corroborated using coupled cluster CCSD­(T) calculations at DFT optimized geometries that provide quantitative molecular-scale information on the reaction mechanisms. The dehydration and dehydrogenation of ethanol probe both the Lewis/Brønsted acid/base and redox properties of the metal centers. The overall conversion of the alcohol is governed by the Lewis acidity of the metal center, and product selectivities, as determined by the relative weights of dehydrogenation and dehydration, are governed by the reducibility of the metal center.