Tailoring Cu-SiO(2) Interaction through Nanocatalyst Architecture to Assemble Surface Sites for Furfural Aqueous-Phase Hydrogenation to Cycloketones.

In this contribution, nanocatalysts with rather diverse architectures were designed to promote different intimacy degrees between Cu and SiO(2) and consequently tune distinct Cu-SiO(2) interactions. Previously synthesized copper nanoparticles were deposited onto SiO(2) (NPCu/SiO(2)) in contrast to ordinarily prepared supported Cu/SiO(2). NPCu@SiO(2) and SiO(2)@Cu core-shell nanocatalysts were also synthesized, and they were all bulk and surface characterized by XRD, TGA, TEM/HRTEM, H(2)-TPR, XANES, and XPS. It was found that Cu(0) is the main copper phase in NPCu/SiO(2) while Cu(2+) rules the ordinary Cu/SiO(2) catalyst, and Cu(0) and electron-deficient Cu(δ+) species coexist in the core-shell nanocatalysts as a consequence of a deeper metal-support interaction. Catalytic performance could not be associated with the physical properties of the nanocatalysts derived from their architectures but was associated with the more refined chemical characteristics tuned by their design. Cu/SiO(2) and NPCu/SiO(2) catalysts led to the formation of furfuryl alcohol, evidencing that catalysts holding weak or no metal-support interaction have no significant impact on product distribution even in the aqueous phase. The establishment of such interactions through advanced catalyst architecture, allowing the formation of electron-deficient Cu(δ+) moieties, particularly Cu(2+) and Cu(+) as unveiled by spectroscopic investigations, is critical to promoting the hydrogenation-ring rearrangement cascade mechanism leading to cycloketones.