Insights into the catalytic mechanism of 5-hydroxymethfurfural to phthalic anhydride with MoO3/Cu(NO3)2 in one-pot

Abstract

Recently, we reported a synthetic approach to obtain renewable phthalic anhydride (PA) from 5-hydroxymethfurfural (HMF) with a yield of 63.2% using MoO₃/Cu(NO₃)₂ as a catalyst in one pot, for the first time. The reaction pathway has been elucidated in our previous study. Herein, the synergistic catalytic mechanism of MoO₃/Cu(NO₃)₂ for the oxidation of HMF to PA was investigated. The commercially available MoO₃ (c-MoO₃) with superior characteristics, including more lattice oxygen and better oxygen-donating capacity, provides higher activity for the oxidation of HMF to PA. More importantly, the synergy between c-MoO₃ and Cu(NO₃)₂ ensured the high yield of PA through the Mo⁶⁺/Mo⁴⁺ redox couple facilitated by the redox cycling of Cu²⁺/Cu⁺ with the assistance of oxygen.