Iodine vacancies enhanced C-Br bond activation and debromination of decabromodiphenyl ether over non-stoichiometric bismuth iodide homojunction

The activation of carbon-halogen bonds is of great significance to realize the breakdown of halogenated contaminants. Herein, a series of iodine vacancies enriched BiOI 1-x photocatalysts prepared by simple temperature regulation were successfully applied in photocatalytic debromination of decabromodiphenyl ether (BDE209) under irradiation (λ > 360 nm). The obtained BiOI-450℃ composed of Bi 7 O 9 I 3 /Bi 5 O 7 I homojunction with iodine vacancies exhibited the best photocatalytic capacity to debromine BDE209. The removal of the first bromine atom from BDE209 on BiOI-450℃ displayed strong position selectivity that meta-debromination is superior to para -debromination, with essentially no ortho -debromination products formed. The selectivity of meta -debromination on iodine vacancies is as high as 72 %, which is higher than the selectivity on oxygen vacancies and sulfur vacancies. The larger space of iodine vacancy is more conducive to accommodating the bromine atom, therefore stabilizing the meta- bromine atomic adsorption configuration of BDE209 and promoting the C-Br bond activation by O…Br halogen bond with the support of surrounding oxygen atoms. This work will provide a feasible strategy for efficient dehalogenation of halogenated persistent organic pollutants based on halogenated bond activation.