Emergence of Visible‐Light Water Oxidation Upon Hexaniobate‐Ligand Entrapment of Quantum‐Confined Copper‐Oxide Cores

Abstract

The formation of small 1 to 3 nm organicligand free metal-oxide nanocrystals (NCs) is essential to utilization of their attractive size-dependent properties in electronic devices and catalysis. We now report that hexaniobate cluster-anions, [Nb 6 O 19 ] 8À , can arrest the growth of metal-oxide NCs and stabilize them as water-soluble complexes. This is exemplified by formation of hexaniobate-complexed 2.4-nm monoclinic-phase CuO NCs (1), whose ca. 350 Cu-atom cores feature quantum-confinement effects that impart an unprecedented ability to catalyze visible-light water oxidation with no added photosensitizers or applied potentials, and at rates exceeding those of hematite NCs. The findings point to polyoxoniobate-ligand entrapment as a potentially general method for harnessing the sizedependent properties of very small semiconductor NCs as the cores of versatile, entirely-inorganic complexes.

Entrapment of metastable nanocrystals by polyoxometalates

“…In this context, polyoxometalate cluster-anions (POMs) serve as ligands for metal-oxide, 16 -hydroxide 17 -oxyhydroxide, 18 and -chalcogenide 19 NCs, present as the cores of soluble macro-anion like complexes. Unlike organic ligands, the more-bulky POMs bind directly to a limited fraction of atoms at the NC surface, leaving numerous (reactive) sites exposed to solution.…”