Ligand and band engineering-induced covalent organic framework-embedded Ti32 Oxo-cluster gels-based Z-scheme heterojunction for boosting the photocatalytic degradation performance of tetracycline

Designing and synthesizing highly efficient photocatalysts with proper energy band structures, which can accelerate the degradation of antibiotics, is crucial and challenging. Herein, by introducing a simple ligand engineering strategy, we ingeniously developed a novel approach for facile synthesis of covalent organic framework (COF) embedded and oxygen vacancies (OV) in-situ doped Ti32 oxo-cluster gels-based Z-scheme heterojunction, COF@OV-Ti32-gels (CT-X). This strategy has led to a remarkable improvement in the photodegradation efficiency of tetracycline hydrochloride (TC), increasing from 15% (pure Ti32 crystals) to an impressive 93.7%. The heterojunctions, which possess modified bandgap structures due to the presence of oxygen defects, exhibit superior photo-induced charge separation efficiency compared to Ti32 without such defects. This enhanced utilization of sunlight results in highly efficient photocatalytic degradation of TC via a built-in electric field. Intriguingly, the CT-X photocatalysts, synthesized with a unique heterojunction structure, exhibit the ability to achieve full-time domain degradation of TC. Notably, CT-X can effectively degrade TC in the absence of light, and its degradation capability is significantly enhanced upon exposure to visible light. Furthermore, the superoxide radical (•O2¯) was evidenced to play a crucial role in the photocatalytic process, and the corresponding degradation mechanism was also depicted.