Efficient degradation of tetracycline hydrochloride via Fe-MOF-Initiated Photo-Self-Fenton Catalysis

The photo-self-Fenton reaction, known for its in-situ generation of H2O2, has garnered significant attention in advanced oxidation processes. Among these, systems combining Fe2+ with oxygen (O2) reduction for H2O2 production (ORR-H2O2) represent a critical category of photo-self-Fenton reactions. However, in Fe2+/ORR-H2O2 systems, competing reactions such as oxygen reduction and Fe3+ reduction limit their efficiency and broader applicability. A promising alternative is the integration of two-electron water oxidation for H2O2 production (WOR-H2O2) with an accelerated Fe2+/Fe3+ redox cycle. Despite this, the direct use of metal-organic frameworks (MOFs) in photo-self-Fenton systems for organic pollutant degradation has not been extensively reported. In this study, two new Fe2+-MOFs, {[Fe2 (HL1) 2]& sdot;(H2O)}n (1) and {[Fe(HL2)(H2O)]} n (2), were successfully synthesized and directly employed in a photo-self-Fenton system to degrade tetracycline hydrochloride (TCH) via two-electron WOR-H2O2. The results revealed remarkable efficiency, achieving TCH degradation rates of 97 % and 86 % within 60 min under 10 W LED lamp irradiation (lambda = 420 nm) for MOFs 1 and 2, respectively. Density Functional Theory (DFT) calculations confirmed that the Fe centers in the MOFs served as the primary active sites for WOR-H2O2. Additionally, the degradation mechanism and pathway were comprehensively analyzed, highlighting hydroxyl radicals (center dot OH) as the dominant reactive species in the process. This study introduces a novel approach to leveraging Fe2+-MOFs for efficient photo-self-Fenton reactions, offering valuable insights for the treatment of recalcitrant pollutants in environmental applications.