Modulating the Photocatalytic Capability of Organic Small Molecule Semiconductors for the Degradation of Different Antibiotics via Self-Assembly and Inorganic Hybridization

This study introduces a perylene diimide (PDI) small molecule in the photocatalytic degradation of antibiotics for the first time. Initially, we optimized its photoelectric performance through self-assembly to obtain an n-type photocatalyst (SA-PDI). Subsequently, WO₃ and Cu₂O were incorporated using a facile one-step method to prepare n-n type and n-p type organic-inorganic hybrid photocatalysts (PDI-WO₃ and PDI-Cu₂O). This approach simultaneously achieved self-assembly, metal ion doping, and inorganic hybridization, further modulating the photocatalytic properties of the materials. Studies indicated that PDI-WO₃ operates via a type-II heterojunction mechanism, whereas PDI-Cu₂O follows an S-scheme heterojunction mechanism. SA-PDI demonstrated superior degradation efficiency toward tetracycline hydrochloride (TCH), while PDI-WO₃ exhibited enhanced activity for both TCH and doxycycline hydrochloride (DOX). In contrast, PDI-Cu₂O showed higher efficacy for ciprofloxacin (CIP) and norfloxacin (NOF). These differences in photocatalytic performance are attributed to the distinct active species generated by each catalyst, aligning with the degradation requirements of specific antibiotics. Moreover, since all three materials are based on the PDI molecule, they are inherently compatible. Consequently, we directly mixed these materials to prepare composite photocatalysts for the simultaneous photocatalytic degradation of multiple antibiotics. In a simulated wastewater system, we systematically investigated the effects of inorganic ions, humic acid, and pH on the effectiveness of the composite photocatalysts in treating mixed antibiotic solutions. Ultimately, this study provides novel design strategies for organic-inorganic hybrid materials and demonstrates promising potential for practical applications in mitigating antibiotic contamination in real wastewater systems.