Year: 2026
Type: preprint
Abstract: Engineering metal–support interfaces through controlled surface functionalization offers a versatile route to tailor supported metal catalysts. Here, citrate-functionalized hydroxyapatite (HAp) serves as an inorganic–organic platform for the in-situ formation of Au nanoparticles, evaluated in the solvent-free aerobic oxidation of benzyl alcohol. A series of Au/(HAp)(Cit) catalysts (x = 0, 1, 2, 4) was prepared to correlate citrate loading with surface properties, Au dispersion, and catalytic performance. Multi-technique characterization (XRD, ATR-FTIR, N physisorption, XPS, SEM-EDX, HR-TEM, ICP-OES) reveals that citrate functionalization tunes HAp surface chemistry and texture while promoting a more homogeneous distribution of Au nanoparticles. Increasing citrate content modifies the electronic environment of surface Au, as evidenced by shifts in Au 4f binding energies and changes in the Au/Ca surface ratio. Catalytic activity increases with citrate loading, with Au/(HAp)(Cit) achieving 99% benzyl alcohol conversion under solvent-free conditions using O₂. This performance is accompanied by high process efficiency (95% mass productivity, E-factor 0.05, 99% carbon efficiency). Prolonged reaction times favor over-oxidation to benzoic acid, highlighting the activity–selectivity trade-off. The catalysts show good recyclability; long-term storage induces partial oxidation and restructuring of surface Au, but NaBH treatment substantially restores activity. These results establish citrate functionalization as an effective strategy to modulate Au–HAp interfacial properties and define structure–activity relationships for aerobic alcohol oxidation.
Source: Research Square
Authors: Afef Mehri, Mohamed Hassen Baouab
Institution: University of Monastir
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7214729147