Surface Sulfate Modification Promoted Excitons Extraction of BiOBr Nanosheets for Efficient ¹ O ₂ Photosynthesis and Chlorophenols Dechlorination

ABSTRACT Photocatalytic molecular oxygen (O 2 ) activation provides a sustainable approach to produce singlet oxygen ( 1 O 2 ) for organic contaminants detoxification. However, the charge carriers‐involved pathway usually suffers from unsatisfactory 1 O 2 production efficiency owing to energy loss caused by photogenerated hole‐mediated superoxide species () oxidation. If the photoinduced species could be directly extracted onto photocatalysts surface rather than completely separated into electron and holes, traditional built‐in electric field‐triggering charge‐carriers extraction process might be circumvented, promoting the electroneutral excitons‐mediated 1 O 2 production. Herein, we demonstrate that introducing sulfate ions on bismuth oxybromide surface ([SO 4 ]‐BiOBr) using a facile photoetching‐coordination strategy can regulate its steric hindrance and surface excitonic states. Benefiting from the energy gradient from the bulk to surface excitonic states, [SO 4 ]‐BiOBr exhibits extremely high‐efficiency bulk exciton extraction performance. Different from the counterparts favoring the O 2 chemisorption via a side‐on mode, [SO 4 ]‐BiOBr with larger steric hindrance preferentially transfers the energy of long‐lived excitons to physically absorbed O 2 , resulting in the photocatalytically generated reactive oxygen species (ROS) switching from to 1 O 2 and thereby boosting the dechlorination and degradation of 4‐chlorophenol (4‐CP). This study reveals the pivotal effect of surface modification on regulating the excitonic processes of semiconductors for efficient 1 O 2 photosynthesis and subsequent wastewater purification.