P,N-Codoped Carbon for Efficient 2,5-Diformylfuran Production from Fructose

This study presents an approach for the “one-pot two-step” synthesis of 2,5-diformylfuran (DFF) from fructose using a metal-free phosphorus-doped carbon nitride (P-CN) catalyst. The bifunctional P-CN integrates P-O bonds for acid-catalyzed fructose dehydration to 5-hydroxymethylfurfural (HMF) and P-C/graphitic-N sites for selective aerobic HMF oxidation to DFF. The 10% P-CN catalyst achieved 91.5% DFF yield during the stepwise oxidation of isolated HMF under the mild conditions (1.5 MPa O2, 120 °C), while the “one-pot” cascade reaction yielded 63% DFF due to competing side reactions. Characterization revealed that P-doping enhanced porosity (883 m2/g surface area) and electronic properties, with graphitic-N facilitating O2 activation. P=O groups are hypothesized to mediate proton transfer from reactive substrates via hydrogen-bonding networks, thereby enhancing acid-catalyzed pathways. NH3-TPD and XPS confirmed tailored acid sites and P-N/C elemental synergism, while FT-IR demonstrated substrate adsorption via P=O/HMF-OH interactions. The catalyst retained stability over multiple cycles, demonstrating its practicality. This work advances biomass valorization by elucidating the dual-role design of nonmetallic catalysts, offering an eco-friendly alternative to conventional metal-based systems.