Synthesis of defect-rich UiO-66 using deep eutectic solvent: Enhanced photocatalytic degradation of tetracycline in water

In order to achieve more efficient and environmentally friendly removal of tetracycline (TC) from polluted water, this study innovatively utilizes a choline-based deep eutectic solvent (DES) as a substitute for the traditional toxic organic solvent DMF, and synthesizes a defect-rich chlorine-doped DES-UiO-66 photocatalyst under mild conditions, without the need for strong acids or bases. Under simulated solar illumination, DES-UiO-66 has a degradation efficiency of up to 97.49 % for 50 mg/L TC, which is better than most reported UiO-66-derived photocatalysts and nearly 3.3 times that of conventional DMF-UiO-66. By employing TGA analysis to quantify defects in the samples, a high defect content was observed in DES-UiO-66, demonstrating that DES serves not only as a solvent for material synthesis but also as a modulator of material defects, which results from the competitive coordination between choline chloride and terephthalic acid during the synthesis process. Through a series of characterizations, it is shown that DES-UiO-66 exhibits a greater specific surface area (1220.1242 m2/g) and pore volume (0.7491 m3/g), offering more active sites, higher photogenerated carrier density, and improved electron-hole pair separation efficiency, thus enhancing its photocatalytic performance. Furthermore, the stability and recyclability of DES-UiO-66 were proved by cyclic experiments, and the photodegradation mechanism of DES-UiO-66 as a photocatalyst and the degradation pathway of TC were determined by free radical capture experiments, EPR tests, and DART-MS detection. By integrating green synthesis with advanced material tuning, this work opens new avenues for enhancing photocatalytic performance and advancing the field of sustainable technology. [Display omitted] •UiO-66 was prepared with DES as both the solvent and structural directing agent.•The DES-UiO-66 is rich in Cl-doped defects, offering more active sites.•Larger surface area and better e−-h+ separation boost photocatalytic performance.•Under simulated light, DES-UiO-66 achieves 97.49 % degradation of 50 mg/L TC.•Photodegradation mechanisms and TC degradation pathways were investigated.