Substrate-Specific Heterogeneous Catalysis of CeO2 by Entropic Effects via Multiple Interactions

Achieving complete substrate specificity through multiple interactions like an enzyme is one of the ultimate goals in catalytic studies. Herein, we demonstrate that multiple interactions between the CeO2 surface and substrates are the origin of substrate-specific hydration of nitriles in water by CeO2, which is exclusively applicable to the nitriles with a heteroatom (N or O) adjacent to the alpha-carbon of the CN group but is not applicable to the other nitriles. Kinetic studies reveal that CeO2 reduces the entropic barrier (T Delta S double dagger) for the reaction of the former reactive substrate, leading to 10(7)-fold rate enhancement compared with the latter substrate. Density functional theory (DFT) calculations confirmed multiple interaction of the reactive substrate with CeO2, as well as preferable approximation and alignment of the nitrile group of the substrate to the active OH group on CeO2 surface. This can lead to the reduction of the entropic barrier. This is the first example of an entropy-driven substrate-specific catalysis of a nonporous metal oxide surface, which will provide a new design strategy for enzyme-inspired synthetic catalysts.