We report the first case of amide hydrolysis on a rock-forming material, TiO₂, with insights into its surface activity. Amide hydrolysis at room temperature was achieved on TiO₂ with (001) surface, which is much lower than fluorine-modified (001) surface (>70 °C). The former surface follows the Lewis acid-catalyzed pathway, while the additional Brönsted acid sites induced by fluorine atoms on the latter one unexpectedly hindered the reaction.

Abstract

Amides are crucial components of biomolecules and are extensively used in polymer, pharmaceutical, and agrochemical production. Their direct hydrolysis offers great potential for exploring protein structures and producing valuable carboxylic acids in biological and industrial applications. Nevertheless, activating the resonance-stabilized C−N bond in amides poses a formidable challenge. Extensive research over the past decades has reported various transition metal-based complexes and solid catalysts that catalyze this reaction. These catalysts possess Lewis acid (LA) sites and exhibit enhanced activity when further combined with Brönsted acid (BA) sites. In this study, we present the first demonstration of amide hydrolysis on TiO₂, a rock-forming material, offering valuable insights into its surface activity. By using acetamide as the model compound, we observed that the thermodynamically stable (101) surface of TiO₂ remained inert up to 95 °C. Surprisingly, the high-energy (001) surface of TiO₂ activated amide hydrolysis at a temperature as low as 25 °C. Contrary to previous reports, the fluorine-modified (001) surface with additional BA sites required temperatures above 70 °C likely due to hydrogen bond stabilization by nearby fluorine atoms. These findings provide guidance for the development of cost-effective catalysts with improved activity.