TEOA‐Light‐Mediated In Situ Transformation of BiOX (X = Cl, Br, I) to Bi ₂ O ₂ CO ₃ for Synergistic CO ₂ Capture and Conversion

The removal and utilization of CO 2 are critical for addressing global energy and environmental challenges. Herein, a unique in situ transformation from BiOBr to Bi 2 O 2 CO 3 is developed, enabling integrated CO 2 capture and photocatalytic conversion. Under a CO 2 atmosphere and light irradiation, triethanolamine (TEOA) facilitates the formation of a flower‐like Bi 0 /Bi 2 O 2 CO 3 catalysts containing trace Br − species. This transformation is critically dependent on TEOA. Experimental characterizations and theoretical calculations confirm that TEOA promotes the formation of Bi 2 O 2 CO 3 , while light irradiation enhances its crystallinity and induces the generation of metallic Bi 0 . The formation of Bi 0 contributes to the high CO selectivity in photocatalytic CO 2 conversion. The resulting Bi 2 O 2 CO 3 exhibits outstanding photocatalytic activity, achieving CO and CH 4 evolution rates of 98.7 and 4.7 µmol g −1 h −1 , respectively, with a remarkable CO selectivity of 95.5%. Moreover, the in situ transition pathway is extendable to other BiOX (X═Cl, Br, I) systems, and the reversible transformation between BiOX (X═Cl, Br, I) and Bi 2 O 2 CO 3 enables efficient regeneration and stable cyclic performance. This work provides a dual‐function strategy for simultaneous CO 2 capture and photoreduction. This synergistic capture–conversion mechanism offers new insight into the rational design of multifunctional photocatalysts and goes beyond conventional “photoreduction‐only” approaches.