On the Role of Cu+ and CuNi Alloy Phases in Mesoporous CuNi Catalyst for Furfural Hydrogenation

Bimetallic catalysts display high reactivity in valorization of biomass-derived chemicals. In this work, KIT-6-templated mesoporous CuNiOx catalysts were synthesized and applied for the selective hydrogenation of furfural (FF) to furfuryl alcohol (FA) under relatively mild reaction conditions. A combination of experimental characterization and density functional theory calculations unveiled the critical role of Cu+ species in hydrogen activation and corroborated a direct experimental correlation between the Cu+ concentration and overall hydrogenation activities. Furthermore, a CuNi alloy phase was attributed as the active adsorption site for FF with a difference in adsorption configurations being responsible for a shift in product selectivity from furfuryl alcohol toward tetrahydrofurfuryl alcohol on Ni-rich phases. Thus, in contrast to pure Cu and Ni catalysts, a close interplay between Cu+ sites and a CuNi alloy phase is proposed to enhance activity of the CuNi catalysts in FF hydrogenation. The structure–activity relationships established in the work clarify the role of bimetallic CuNi catalysts in this important reaction and offer a rationale for similar catalytic systems involving hydrogenation of C═O or/and C═C groups.