Aqueous-phase hydrogenation of d-glucose to d-sorbitol was systematically investigated over silica-supported Pt nanoparticles to elucidate structure–reactivity relations and mechanistic insight. d-Glucose hydrogenation over large Pt particles competes with its isomerization to d-fructose over low-coordination (electron-deficient) Pt sites; d-sorbitol production by the former process was structure insensitive for nanoparticles spanning 3–17 nm, whereas isomerization was favored by smaller particles, with both pathways independent of the choice of fumed silica or mesoporous SBA-15 support. While d-fructose was readily hydrogenated to d-mannitol under the same reaction conditions, the latter underwent minimal isomerization to d-sorbitol, which is, therefore, a direct product of d-glucose ring opening and subsequent hydrogenation of the aldose conformer. d-Sorbitol production was favored by low d-glucose concentrations (40 bar), and low reaction temperatures (<140 °C), which suppressed undesired polymerization side reactions.

Chemoselectivity is a cornerstone of catalysis, permitting the targeted modification of specific functional groups within complex starting materials. Here we elucidate key structural and electronic factors controlling the liquid phase hydrogenation of cinnamaldehyde and related benzylic aldehydes over Pt nanoparticles. Mechanistic insight from kinetic mapping reveals cinnamaldehyde hydrogenation is structure-insensitive over metallic platinum, proceeding with a common Turnover Frequency independent of precursor, particle size or support architecture. In contrast, selectivity to the desired cinnamyl alcohol product is highly structure sensitive, with large nanoparticles and high hydrogen pressures favoring C = O over C = C hydrogenation, attributed to molecular surface crowding and suppression of sterically-demanding adsorption modes. In situ vibrational spectroscopies highlight the role of support polarity in enhancing C = O hydrogenation (through cinnamaldehyde reorientation), a general phenomenon extending to alkyl-substituted benzaldehydes. Tuning nanoparticle size and support polarity affords a flexible means to control the chemoselective hydrogenation of aromatic aldehydes.

Hierarchical porous catalysts offer highly connected architectures for enhanced transport of bulky molecules and the sustainable manufacturing of bio-derived platform chemicals and fuels.