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van der Waals Interactions Determine Selectivity in Catalysis by Metallic Gold

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Department of Chemistry and Chemical Biology, and School of Engineering and Applied Sciences, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
Department of Industrial Chemical Engineering, Universidad de Ingeniería y Tecnología, Avenida Cascanueces 2221, Lima 43, Peru
§ Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195, Berlin, Germany
Cite this: J. Am. Chem. Soc. 2014, 136, 38, 13333–13340
Publication Date (Web):August 29, 2014
https://doi.org/10.1021/ja506447y
Copyright © 2014 American Chemical Society

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    Abstract

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    To achieve high selectivity for catalytic reactions between two or more reactants on a heterogeneous catalyst, the relative concentrations of the reactive intermediates on the surface must be optimized. If species compete for binding sites, their concentrations depend on their relative binding strengths to the surface. In this article we describe a general framework for predicting the relative stability of organic intermediates involved in oxygen-assisted reactions on metallic gold with broad relevance to catalysis by metals. Combining theory and experiment, we establish that van der Waals interactions between the reactive intermediates and the surface, although weak, determine relative stabilities and thereby dictate the conditions for optimum selectivity. The inclusion of these interactions is essential for predicting these trends. The concepts and methods employed here have broad applicability for determining the stability of intermediates on the surfaces of catalytic metals and specifically demonstrate the critical role of weak interactions in determining reaction selectivity among reactions of complex molecules.

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    Experimental details for crystal preparation and temperature-programmed reaction spectra including control of reactant dosing, figure of the competitive adsorption of methanol and acetylene, the data for all experiments done to establish the stability hierarchy in Table 2, and figures detailing calculated structural changes for other alkoxys. Analyses for relationship of ΔH for dissociative adsorption to displacement, displacement to relative binding energies, and entropy for adsorbates are also included. This material is available free of charge via the Internet at http://pubs.acs.org.

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