Simultaneous photocatalytic biomass conversion and CO₂ reduction over high crystalline oxygen-doped carbon nitride

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. The lactic acid yield and CO evolution rate over O-CNNTs-2.0 reached 82.08% and 67.95 μmol g^-1 h^-1, which are 1.57- and 7.37-fold times higher than those of CN, respectively. Moreover, ·OH plays a key role in the oxidation half-reaction. 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.