Benzothiadiazole-functionalized Zr-MOF nanosheets enable visible-light mediated photocatalytic oxidation of sulfides in water

Abstract

Ultrathin metal-organic frameworks (MOFs) nanosheets incorporating photochromic units are highly efficient heterogeneous photocatalysts, thanks to their highly exposed catalytic sites, short diffusion pathways, and efficient separation of photo-generated carriers. Herein, we report on the solvothermal synthesis of photoactive benzothiadiazole (BTz) functionalized Zr-MOF nanosheets (Zr-BTDB-NS), which are constructed from Zr12 nodes linked by nine BTDB2− (BTDB = 4,4′-(benzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoate) ligands. The Zr-BTDB-NS exhibited superior photocatalytic activity towards the aerobic oxidation of a broad range of sulfides to their corresponding sulfoxides under visible light irradiation in water at room temperature, even in a gram-scale. The Zr-BTDB-NS can be efficiently recycled and reused for seven cycles without a decrease in conversion or selectivity. Detailed mechanism studies revealed that the Zr-BTDB-NS generates singlet oxygen (1O2) and superoxide radical (O2–) reactive oxygen species under visible light irradiation, which are responsible for the oxidation of sulfides into their corresponding sulfoxides. The simplicity of the synthetic approach as well as the diversity of photoactive organic units hold great promise for designing ultrathin, water-stable, and photoactive Zr-MOF nanosheets. This work will also be of added value for selective photooxidation of sulfides under green and mild conditions.