Leaf-derived sulfonated carbon dots: efficient and recoverable catalysts to synthesize 5-hydroxymethylfurfural from fructose

Sulfonated carbon dots (SCDs) were synthesized from plant leaves via continuously hydrothermal treatment by hydrogen peroxide and sulfuric acid, used as catalyst for converting fructose to 5-hydroxymethylfurfural (HMF). Owing to nanosize effect and moderate acidic intensity, SCDs could thoroughly distribute in the solvent with an improved interfacial compatibility and selectively convert fructose to HMF. Under the optimal condition, the yield of HMF was 92.6% along with a fructose conversion of 100%, benefiting from a low activation energy of 52.9 kJ/mol when dimethylsulfoxide was used as solvent. The SCDs catalyst can be recovered, after six recycles, the fructose conversion and HMF yield were remained 66.1% and 56.2% under condition with incompletely conversion of fructose, respectively. This work provides a sustainable route to prepare carbon dots with a superior catalytic performance for converting biomass to important biobased platform chemicals.