Edge-rich atomic-layered BiOBr quantum dots for photocatalytic molecular oxygen activation

Photocatalytic molecular oxygen activation is severely restricted by poor charge separation and lack of absorption sites. Herein, BiOBr atomic-layered quantum dots (QDs) with abundant edge coordinatively unsaturated sites (CUS) was fabricated to tackle the aforementioned problems. The resulting BiOBr have a thickness equivalent to a single unit cell and have only 3–5 nm in width, which is the smallest value of all reported BiOBr materials. Our pioneering study discloses that the valence band minimum (VBM) and conduction band maximum (CBM) of atomic-layered BiOBr QDs are spatially separated. Therefore, on irradiation, holes are directly generated on the basal surfaces and electrons on the edge sites, leading to ultrafast charge separation. The edges expose a huge number of adsorption sites for oxygen molecules. As a results, the electrons on the edge sites are able to directly reduce the absorbed O2 molecules to exhibit strengthened photocatalytic O2− production. We also firstly demonstrate that BiOBr atomic-layered QDs are an excellent candidate for anticancer applications, which is attributed to enhanced O2− production activity. This study provides an in-depth understanding on the design of advanced photocatalysts via edge unsaturated coordinated sites engineering on the atomic scale.