Insight into the Selective Conversion via a Steered Adsorption and Protonation from Tantalates-based Solid Acid's Intrinsic Proton for Hydride-transfer Reduction

Bronsted solid acids have popularly been used as catalysts or supports for many hydrogenation reactions, while it is uncertain if their structural H species could significantly enhance velocity and reusability for these reactions. In this work, a series of tantalate-supported silver catalysts Ag/MxH2-xTa2O6 (M=H, Li, Na, K, Sr) were prepared, along with abundant solid acid catalysts (Ag/Al2O3, Ag/SiO2-Al2O3, Ag/ZrO2-SO42-, and Ag/heteropolyacid). By assessing activity of a model reaction from p-nitrophenol to the corresponding aniline together with an isotope comparative test (Ag/D2Ta2O6 and Ag/H2Ta2O6), a previously unknown route was uncovered, which involves that intrinsic proton H species of the Bronsted solid acid support directly participate in the formation of products. Meanwhile, Ag NPs could form an embedded distribution by exchanging with structural H species, responsible for the stabilization of catalytic active sites. The results reported here could give a deep understanding on proton chemistry of solid acids in construction of catalysts and/or supports in H-participating reactions.