Porous nitrogen-doped carbons supporting Fe-porphyrins for the highly efficient catalytic oxidation of HMF to HMFCA

A series of FeTPP-N/C-X catalysts were successfully prepared by adsorption of Fe tetraphenylporphine (FeTPP) onto a porous nitrogen-doped carbon (N/C) support using an ultrasonication method. The FeTPP-N/C catalysts were then used for the preparation of 5-hydroxymethyl-2-furan acid (HMFCA) by catalytic oxidation of 5-hydroxymethylfurfural (HMF) at 80 °C. The effects of reaction temperature, NaOH dosage, reaction time, and oxygen pressure on HMF conversion and HMFCA yield were systematically investigated. Under optimized testing conditions, a FeTPP-N/C-1 catalyst prepared using equal masses of FeTPP and N/C delivered a HMF conversion in water of 92.4%, with a selectivity to HMFCA of 97.2% over 6 h at an oxygen pressure of 1.0 MPa. Further, the catalyst showed good stability in five consecutive HMF oxidation tests. Based on the catalytic tests, and detailed catalyst characterization studies before and after reaction, a probable reaction mechanism was proposed for the selective oxidation of HMF to HMFCA by the FeTPP-N/C catalysts. Graphical Abstract A series of FeTPP-N/C catalysts were successfully prepared by the adsorption of iron tetraphenylporphine (FeTPP) onto a porous nitrogen-doped carbon (N/C) support using an ultrasonication method. The FeTPP-N/C catalysts were then used for the catalytic aerobic oxidation of HMF to HMFCA. Under the optimized reaction conditions (temperature 80 °C, reaction time 6 h, O 2 pressure 1 MPa), a high HMF conversion of 92.4% and a remarkable HMFCA selectivity of 97.2% were obtained, suggesting that the developed noble-metal free catalyst has excellent promise for the synthesis of valuable HMFCA from HMF.