Single-crystal oxygen-rich bismuth oxybromide nanosheets with highly exposed defective {10-1} facets for the selective oxidation of toluene under blue LED irradiation

Reactive radicals are crucial for activating inert and low-polarity C(sp3)-H bonds for the fabrication of high value-added products. Herein, novel single-crystal oxygen-rich bismuth oxybromide nanosheets (Bi4O5Br2 SCNs) with more than 85 % {10-1} facets exposure and oxygen defects were synthesized via a facile solvothermal route. The Bi4O5Br2 SCNs demonstrated excellent photocatalytic performance in the selective oxidation of toluene under blue light. The yield of benzaldehyde was 1876.66 mu mol g-1 h-1, with a selectivity of approximately 90 %. Compared to that of polycrystalline Bi4O5Br2 nanosheets (Bi4O5Br2 PCNs), the activity of Bi4O5Br2 SCNs exhibit a 21-fold increase. Experimental studies and density functional theory (DFT) calculations have demonstrated that the defect Bi4O5Br2 (10-1) facets exhibits exceptional adsorption properties for O2 molecules. In addition, the single-crystal structure in the presence of surface defects significantly increases the separation and transport of photogenerated carriers, resulting in the effective activation of adsorbed O2 into superoxide radicals (center dot O2-). Subsequently, the positively charged phenylmethyl H is readily linked to the negatively charged superoxide radical anion, thereby activating the C-H bond. This study offers a fresh perspective and valuable insights into the development of efficient molecular oxygen-activated photocatalysts and their application in the selective catalytic conversion of aromatic C(sp3)-H bonds.