Selective hydrodeoxygenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran over NiFe alloy catalyst

Hydrodeoxygenation (HDO) is vital important for the valorization of oxygen-rich biomass derivatives into high-energy-density fuels and valuable chemicals by selective removal of oxygen-containing functional groups. Low-cost NiFe-based bimetallic catalysts, which integrated the excellent hydrogen activation ability of Ni with the selective adsorption and cleavage of oxygen-containing functional groups of Fe, were attractive in HDO of biomass. However, the limited insights into the coordination structures of active sites and the effects of heteroatom-doping hindered the in-depth understanding of structure−activity relationship in HDO. Herein, a highly selective Ni-280/Fe-N-C-800 catalyst was fabricated via two-step pyrolysis, which afforded 96.3% 2,5-dimethylfuran (DMF) selectivity and complete 5-hydroxymethylfurfural (HMF) conversion at 240 °C and 4 MPa H₂, comparable to state-of-the-art catalysts. More importantly, comprehensive characterizations and fruitful experimental results combined with DFT calculations confirmed that the Fe-N₄-assisted NiFe alloy nanoparticles (NPs) served as the core active sites, then promoting by metal (M)-N_x coordination structures. This work not only elucidated the structure−activity relationship between NiFe alloy catalysts and reactants, but also provided theoretical guidance for selectivity control in HDO process.