Bio‑Stabilized Copper Nanoclusters Enable Highly Selective Aerobic Alcohol Oxidation in Water

Water‑soluble bovine serum albumin‑stabilized copper nanoclusters (BSA–Cu NCs) were synthesized and fully characterized by FT‑IR, UV–Vis, TEM, XPS, photoluminescence spectroscopy, ICP, and TGA. The ultrasmall nanoclusters (1.7 ± 0.5 nm), predominantly containing Cu⁰ species, exhibited high structural stability and strong ligand‑to‑metal charge transfer features. The BSA–Cu NCs demonstrated excellent catalytic performance in the aerobic oxidation of a wide range of primary and secondary alcohols under mild conditions (25°C, water, air or O₂), affording the corresponding carbonyl compounds with > 99% selectivity. Studies on optimization showed that catalyst loading, oxygen flow rate, and isobutyraldehyde as a cocatalyst are all important for getting quantitative conversions in a short amount of time. Spectroscopic analyses and radical-trapping experiments substantiate a Cu(II)/Cu(I) redox-mediated radical pathway, while dismissing the generation of peroxo or superoxo copper species. The catalyst kept working over many cycles with very little damage to its structure. Compared with previously reported copper‑based systems, the BSA–Cu NCs offer a sustainable, efficient, and environmentally benign platform for aerobic alcohol oxidation in aqueous media.