Noncovalent Bonding Controls Selectivity in Heterogeneous Catalysis: Coupling Reactions on Gold

Abstract

Enhancing the selectivity of catalytic processes has potential for substantially increasing the sustainability of chemical production. Herein, we establish relationships between reaction selectivity and molecular structure for a homologous series of key intermediates for oxidative coupling of alcohols on gold using a combination of experiment and theory. We establish a scale of binding for molecules with different alkyl structures and chain lengths and thereby demonstrate the critical nature of noncovalent van der Waals interactions in determining the selectivity by modulating the stability of key reaction intermediates bound to the surface. The binding hierarchy is the same for Au(111) and Au(110), which demonstrates a relative lack of sensitivity to the surface structure. The hierarchy of binding established in this work provides guiding principles for predicting how molecular structure affects the competition for binding sites more broadly. Besides the nature of the primary surface-molecule bonding, three additional factors that affect the stabilities of the reactive intermediates are clearly established: (1) the number of C atoms in the alkyl chain, (2) the presence of C-C bond unsaturation, and (3) the degree of branching of the alkyl group of the adsorbed molecules. We suggest that this is a fundamental principle that is generally applicable to a broad range of reactions on metal catalysts.

Identifying key descriptors in surface binding: interplay of surface anchoring and intermolecular interactions for carboxylates on Au(110)

“…The liquid organics were purified according to procedures described previously and the gas phase vapor was leaked in the chamber while monitoring the rise in pressure of the chamber. 31 , 32 Temperature programmed experiments were performed with each reactant to identify its signature products and displacement reactions were preformed to determine the relative binding stability of selected pairs of carboxylates as described in the (ESI † ). The quantitative analysis of the temperature programmed reaction data was performed as described in the ESI.…”

Effect of Frustrated Rotations on the Pre-Exponential Factor for Unimolecular Reactions on Surfaces: A Case Study of Alkoxy Dehydrogenation

“…The distance between the backbone of the species and the Cu surface increases when the vdW interactions were excluded, confirming the significant vdW effects on the structures. [26][27][28][29][30][31] The transition states for C-H bond breaking of 1-propoxy and 1-butoxy were reexamined with the updated adsorption structures. The NEB calculations suggested that the transition It is important to emphasize more generally the difficulty in finding the global minimum in the high-dimensional configuration space of adsorption for large molecules.…”

Stability of functionalized platform molecules on Au(111)

“…The decomposition of several molecules and the relative stabilities of intermediates in on-surface reactions on Au have recently been attributed to the strong van der Waals (vdW) interaction. [56][57][58][59][60] We therefore investigated the role of dispersion for dissociation II and III by calculating the related adsorption energies with and without inclusion of vdW interaction (Table II), namely, with the PBE + vdW functional and the pure PBE (Perdew-Burke-Ernzerhof) functional (see Appendix, Subsection 4). The adsorption energies of 1, 3, and 4 increase by ≈2.2 eV with PBE compared to PBE + vdW, reflecting strong dispersion interaction with Au(111) and its crucial role for the adsorption process.…”