Electrochemical reductive biomass conversion: direct conversion of 5-hydroxymethylfurfural (HMF) to 2,5-hexanedione (HD) via reductive ring-opening

2,5-Hexanedione (HD), which can be produced by reduction of 5-hydroxymethylfurfural (HMF), one of the most important biomass intermediates, can serve as a precursor to produce various biofuels and key building block chemicals. The conversion of HMF to HD requires reduction of both the alcohol and aldehyde groups to alkane groups as well as opening of the furan ring. In this study, a direct electrochemical conversion of HMF to HD at ambient pressure and temperature was demonstrated without using H-2 or precious metal catalysts. Water was used as the hydrogen source and zinc was used as the catalytic electrode, which enabled hydrogenolysis and Clemmensen reduction coupled with furan ring opening. Optimum conditions to achieve high Faradaic efficiency (FE) and selectivity for HD production were investigated and plausible mechanisms were proposed. The environmentally benign one-step procedure to produce HD reported in this study will serve as a new route to valorize biomass intermediates.