Simultaneous Photocatalytic Biomass Conversion and CO ₂ Reduction Over Highly Crystalline Oxygen-Doped Carbon Nitride

Abstract

Simultaneous photocatalytic biorefinery and CO₂ reduction to co-produce fuels and high value-added chemicals have recently attracted significant attention; however, comprehensive studies are still lacking. Herein, we report the preparation of highly crystalline oxygen-doped carbon nitride nanotubes (O-CNNTs-x) using an ammonium fluoride-assisted hydrothermal/calcination strategy. The hollow structure, high crystallinity, and O incorporation endowed the O-CNNTs-x with photocatalytic activity by considerably improving optical absorption and modulating the charge carrier motion. In O-CNNTs-2.0, the lactic acid yield (82.08%) and CO evolution rate (67.95 μmol g^-1 h^-1) were 1.57- and 7.37-fold higher than those of CN, respectively. Moreover, O-CNNTs-2.0 not only exhibits exceptional stability, but also can be effectively utilized in the co-production of lactic acid and CO from different biomass-derived monosaccharides. This study offers a facile approach for fabricating highly crystalline element-doped CN with a customizable morphology and electronic properties and demonstrates the viability of co-photocatalytic CO₂ reduction and biomass selective oxidation.

Keywords: Crystalline carbon nitride; Hollow morphology; CO2 reduction; Biorefinery; Photocatalysis