Selective C-Br bond activation for decabromodiphenyl ether photo-debromination via sulfur vacancies enriched zinc indium sulfides

Activation of carbon-halogen bonds is vital for realizing the degradation of halogenated pollutants. Herein, zinc indium sulfides Zn x In 2 S x+3 (x = 1, 2 and 3) with different sulfur vacancies concentration were constructed to achieve photocatalytic decabromodiphenyl ether (BDE209) debromination. Under irradiation, ZnIn 2 S 4 had the most outstanding degradation ability to BDE209, attributing to its abundant surface sulfur vacancies. The sulfur vacancies not only can narrow the forbidden band to increase light absorption and utilization, but more importantly, serve as active sites for the adsorption and activation of C-Br of BDE209. Interestingly, the removal of the first bromine atom from BDE209 on sulfur vacancies behaved as a meta- selective debromination process. The selectivity of meta- debromination is as high as 70%, superior to that on oxygen vacancies enriched photocatalyst. It can be ascribed to the larger vacancy space of sulfur to better accommodate bromine atoms in BDE209, which helps to stabilize the meta- bromine adsorption configuration of BDE209 on sulfur vacancies. Meanwhile, the intermediate configuration is further stabilized under the assistance of the S…Br halogen bond by surrounding sulfur atom at the catalytic interface. This work sheds light on the great potential of larger element vacancies to activate C-halogen bonds in photocatalytic treatment of halogenated pollutants.