Flower-like TP-BiOI direct Z-scheme heterojunction for efficient visible-light photocatalytic removal of environmental pollutants

Compared with conventional heterojunctions, direct Z-scheme heterojunctions can retain strong redox potentials while effectively accelerating the separation of photogenerated charge carriers. Herein, we report a flower-like direct Z-scheme heterojunction constructed from tris(4-aminophenyl)amine-based polyimide (TP) and BiOI, and investigate its photocatalytic activity using Cr(VI) reduction and rhodamine B (RhB) degradation as the target reactions. Under visible light, TP-BiOI(45 %) exhibited excellent Cr(VI) reduction performance and RhB degradation activity, achieving an apparent rate constant of 2.3207 min⁻¹ for Cr(VI) reduction, approximately 4.6 and 4.3 times higher than those of pristine TP (0.5059 min⁻¹) and BiOI (0.5364 min⁻¹), respectively. Moreover, it still retained a certain degree of photocatalytic activity under 600 nm light irradiation. The enhanced performance is primarily attributed to the formation of the direct Z-scheme heterojunction, which significantly improves the separation efficiency of photogenerated charge carriers. Additionally, the flower-like morphology increases the specific surface area and number of active sites, further boosting catalytic performance. This study provides a green and simple method for preparing unique-shaped direct Z-scheme heterojunctions, which holds great promise for the removal of environmental pollutants under visible light.