P- and F-co-doped Carbon Nitride Nanocatalysts for Photocatalytic CO₂ Reduction and Thermocatalytic Furanics Synthesis from Sugars

A new P- and F-co-doped amorphous carbon nitride (PFCN) has been synthesized via sol-gel-mediated thermal condensation of dicyandiamide. Such synthesized P- and F-co-doped carbon nitride displayed a well-defined mesoporous nanostructure and enhanced visible light absorption region up to infrared with higher BET surface area of 260.93 m² g⁻¹; the highest recorded value for phosphorus-doped carbon nitride materials. Moreover, the formation mechanism is delineated and the role of templates was found to be essential not only in increasing the surface area but also in facilitating the co-doping of P and F atoms. Co-doping helped to narrow the optical band gap to 1.8 eV, thus enabling an excellent photocatalytic activity for the aqueous reduction of carbon dioxide into methanol under visible-light irradiation, which is fifteen times higher (119.56 μmol g⁻¹ h⁻¹) than the bare carbon nitride. P doping introduced Brønsted acidity into the material, turning it into an acid-base bifunctional catalyst. Consequently, the material was also investigated for the thermal conversion of common carbohydrates into furanics.