Preparation of gold nanoparticles supported on microcrystalline cellulose by solid-mortar grinding and their...

A solid-grinding approach for transforming microcrystalline cellulose into less ordered matrices, followed by the deposition of a high density of gold nanoparticles (NPs) without employing environmentally toxic chemicals, solvents, or external reducing agents is reported. The generation of abundant chemically accessible active hydroxyl groups in the cellulose fibril of MCC, facilitated by mild mechanochemical forces during the manual solid grinding of MCC and HAuCl₄with NaOH, promotes the rapid deposition of gold NPs (2-5 nm) with loadings up to 4.6 wt% and increased dispersion within the MCC support. FTIR and XRD analyses reveal that gold chlorides substantially disrupt the intramolecular hydrogen bonding networks through metal-hydroxide interactions in the cellulose fibril structures of MCC, hence facilitating the efficient diffusion of gold NPs. The resulting MCC-supported gold NPs (Au/MCC) were evaluated as catalysts for oxidative homocoupling of phenylboronic acids (PBA) and aerobic oxidation of alcohols. The catalytic studies show that the active hydroxyl groups in the cellulose fibril not only coordinate with the gold, but also synergistically improve the rapid conversion of PBA into biphenyl and oxidation of alcohols into corresponding aldehydes and ketones with greater selectivity.