Photocatalyzed Direct Decarboxylation for Biobased Cadaverine Production under Mild Conditions

Abstract

The decarboxylation of bio-originated l-lysine to cadaverine provided a sustainable pathway for the production of bionylon 5X materials due to the low cost and overcapacity of l-lysine. A photocatalytic approach was designed to produce cadaverine using Pt/TiO₂ as an effective photocatalyst under mild conditions (UV light, 30 °C, and 0.1 MPa H₂). The Pt cocatalyst was utilized to promote the effective separation of photogenerated electrons and holes in the semiconductor TiO₂. After Pt doping, the bandgap width of TiO₂ was narrowed from 3.12 to 2.88 eV, promoting the generation of photogenerated electrons and holes. With the synergistic effect of Pt, TiO₂, and oxygen vacancies, the selectivity of cadaverine increased to 86% under optimal conditions. At a molecular level, FT-IR spectra showed that l-lysine was adsorbed vertically via the coordination of −COOH on Pt/TiO₂. It was then directed to be oxidized by photogenerated holes to form (NH₂)₂(CH₂)₄CH· radicals, as proven by the in situ FT-IR investigation. Alkyl radical intermediates formed on holes then readily coupled with hydrogen species to yield a high selectivity of cadaverine. This work sheds new light on the effective and green high-value conversion of biomass.