Phosphorus-doped carbon nitride with grafted sulfonic acid groups for efficient photocatalytic synthesis of xylonic acid

Abstract

The photocatalytic selective oxidation of biomass-derived feedstocks to high-value organic acids is promising and challenging, especially for the production of xylonic acid. Herein, novel phosphorus-doped carbon nitride with grafted sulfonic acid groups (P@CN-SO₃H) was prepared and successfully used in the photocatalytic-reforming of xylose to xylonic acid. The successful doping of phosphorus and grafting of sulfonic acid groups significantly extend the visible light adsorption range and decrease the photoluminescence intensity of the resulting carbon nitride, thereby enhancing its photocatalytic activity. P@CN-SO₃H can efficiently catalyze the synthesis of xylonic acid (88.1%) from xylose with excellent stability and reusability. Electron spin-resonance results indicate that the contents of h⁺, ˙OH, ·O₂⁻, and ¹O₂ increase with the irradiation time, facilitating the synthesis of xylonic acid, in which ˙O₂⁻ plays a primary role. The economic benefits and results of the present xylonic acid production system indicate its huge potential for industrial applications.