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 CuNiO_x 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.