Acetic acid-modified MIL-125(Ti) photocatalysts for efficient degradation of tetracycline in seawater

Photocatalytic degradation of antibiotics in high-salinity seawater remains challenging due to salt ion interference and limited visible-light utilization. In this study, we developed a defect-rich titanium-based metal–organic framework (MIL-125(HAC)) through acetic acid modulation via a solvothermal method. The optimized MIL-125(HAC)-3 photocatalyst exhibited remarkable tetracycline (TC) degradation efficiency in seawater, reaching 90.9% after 60 min of visible-light irradiation (compared with 90.0% in deionized water) and maintaining over 85% efficiency after five cycles. This demonstrates its robust resistance to salt ion interference. Additionally, the degradation rate constant of MIL-125(HAC)-3 in seawater (0.0283 min −1 ) was 25 times higher than that of commercial TiO 2 , highlighting its superior photocatalytic performance. The enhanced performance is attributed to the introduction of acetic acid, which induced a rich mesoporous defect structure, facilitating selective TC adsorption and significantly broadening the visible light response range. Free radical trapping experiments and electron paramagnetic resonance (EPR) spectroscopy further revealed that superoxide radicals (•O 2 − ) and holes (h + ) serve as the primary active species in the degradation process. This work offers a scalable and effective strategy for designing marine-tolerant photocatalysts to remediate antibiotic pollution.