Fabrication of new MIL-53(Fe)@TiO2 visible-light responsive adsorptive photocatalysts for efficient elimination of tetracycline

Novel semiconductor–MOFs composites based on TiO2 and MIL-53(Fe) were constructed using a facile one-pot solvothermal process and acted as effective visible-light responsive adsorptive photocatalysts for the removal of tetracycline (TC). The resultant MIL-53(Fe)@TiO2 composites were characterized by comprehensive analyses, ESR, and photoelectrochemical measurements. Experimental results showed that the synthesized MIL-53(Fe)@TiO2 composites possessed enhanced adsorption and excellent photocatalytic activity for TC solution under visible light irradiation. Among all the composites, the MIL-53(Fe)@TiO2 = 1:2 exhibited optimal removal performance compared with pristine MIL-53(Fe) and TiO2. The results of UV–vis DRS verified the visible light absorption range of the prepared composite was improved, and the results of the Nyquist plot illustrated that the transfer ability of photo-generated charge carriers was boosted. More importantly, the ESR results showed that the •O2− and •OH active species played a crucial role in photocatalytic reactions. The enhanced photocatalytic ability was due to not only the fabrication of the n-n type heterojunction photocatalysts, which could provide more active species, but also the synergy between MIL-53(Fe) and TiO2 in the composites. A possible reaction mechanism was proposed to elucidate the reason for the photocatalytic performance enhancement. Our findings may open up a new field for Fe-MOF and semiconductor composite materials in removing TC in visible light.