Electroreductive C-C Coupling of Furfural to Jet Fuel Precursors in Neutral Media via Synergistic Catalysis of the Polyoxotungstate and Cu Complex

The electrochemical coupling of biomass platform molecules to biofuels provides a promising method for addressing energy crises and environmental issues. However, achieving high yields of C-C coupling products under ambient conditions remains a challenge. Herein, we present a highly efficient electrocatalyst, [Cu(pz)]₃[PW₁₂O₄₀] (Cu-PW₁₂), fabricated by combining a Cu-pz complex (pz = pyrazine), a redox catalytic center, with Keggin-type PW₁₂O₄₀, and an electron sponge. Cu-PW₁₂ exhibits remarkable catalytic activity for the electroreductive C-C coupling of furfural (FF), a bulk and low-cost biomass platform chemical, to produce a jet fuel precursor, hydrofuroin (HDF). Under neutral and ambient conditions, over 99% of FF is converted and the selectivity of HDF reaches 91.2%. Furthermore, experimental and theoretical studies, including control experiments, kinetic isotope studies, electrochemical and spectral analyses, and DFT calculations, reveal a synergistic catalysis effect between Cu center and PW₁₂. The introduction of PW₁₂ not only facilitates electron transfer, improving FF conversion, but also changes the rate-determining step, favoring the formation of HDF. Under turnover conditions, the Cu-PW₁₂ catalyst is initially reduced and then FF is reduced by the Cu center to ketyl radical after protonation on the electrode surface. Finally, the self-coupling of two ketyl radicals in solution leads to the generation of HDF.