FTIR study of adsorption and photochemistry of amide on powdered TiO2: Comparison of benzamide with acetamide

Abstract

FTIR has been used in situ to investigate the adsorption, thermal transformation, and photoreactions of benzamide on TiO₂. The reaction pathways are compared to the case of acetamide. Our reaction system is focused on the vapor–solid surface reactions, which are complementary to the reactions catalyzed in the solution phase. Benzamide is adsorbed molecularly or dissociatively to generate C₆H₅CONH by losing one amino hydrogen at 35 °C. Upon raising the TiO₂ surface temperature, C₆H₅CN and C₆H₅COO are produced. Under photoirradiation in O₂, adsorbed benzamide and C₆H₅CONH are transformed into surface species of NCO, C₆H₅COO, and C₆H₅CN and gaseous CO₂, revealing versatile photoreaction pathways. These surface intermediates were not found in a previous study of benzamide photodecomposition catalyzed by TiO₂ in the solution phase. Similar reaction pathways were found for acetamide on TiO₂. It is worthy of note that –CONH₂ on TiO₂ is transformed into –CN thermally and photochemically. –CN reacts reversibly with surface OH groups to form –CONH₂.