Preparation of Ti-based homologous heterojunction and its photocatalytic degradation properties of tetracycline in seawater

To address ion interference in photocatalytic antibiotic degradation within high-salt seawater, this study innovatively designed and synthesized a titanium-based metal–organic framework (MOF) heterojunction composite. Specifically, a solvothermal technique was used to create MIL-125(HAC)/TiO 2 (TAC) photocatalysts using commercial TiO 2 (P25) and MIL-125(Ti) that had been treated with acetic acid. Remarkably, under 60 min of visible-light irradiation, the optimized TAC-2 sample achieved 95.7 % tetracycline (TC) degradation in seawater (compared to 98.1 % in deionized water) and retained >85 % efficiency after four cycles. Critically, its degradation rate constant (k=0.0355 min −1 ) in seawater was 44.4 times higher than that of P25, demonstrating exceptional resistance to salt-ion interference and photocatalytic activity. Mechanistic studies revealed that the performance enhancement arises from three synergistic mechanisms: (1) A mesoporous structure mitigating ion interference and strengthening TC-selective adsorption; (2) A Type-II heterojunction enabling efficient charge separation; (3) •O 2 − and h + identified as dominant active species (confirmed by EPR and quenching tests). Collectively, this work establishes an effective MOF heterojunction engineering strategy for efficient antibiotic removal in saline environments, ultimately contributing to marine pollution remediation.