An eco-friendly acidic catalyst phosphorus-doped graphitic carbon nitride for efficient conversion of fructose to 5-Hydroxymethylfurfural

Abstract

An eco-friendly and stable metal-free acidic catalyst phosphorus-doped graphitic carbon nitride (P–UCN) synthesized for the highly efficient dehydration of fructose to 5-Hydroxymethylfurfural (HMF) was presented. The acidic sites (P sites) were introduced into the g-C3N4 structure via a simple thermal polycondensation of urea. A 91.7% HMF yield was achieved with optimal P–UCN catalyst under mild reaction conditions (160 °C, 3 h). XPS and NMR characterizations of P–UCN catalysts suggested that the P atoms may replace the corner and bay carbon sites, which could provide stable acidic sites for fructose dehydration into HMF. NH3-TPD analysis indicated that a moderate amount of P doped would provide higher catalytic activity for the dehydration reaction. Furthermore, the 1.0P–UCN (real content 1.83 wt%) catalyst was demonstrated high stability in the dehydration system and retained high reactivity after being recycled 5 times. The characterization results of recovered 1.0P–UCN further confirmed that the morphology and structure of the catalyst remained well after the dehydration reaction.