Facile construction of type-I Fe-MOF@g-C3N4/BiOI heterojunctions for boosting photo-Fenton catalytic degradation of ofloxacin: performance, DFT calculations, pathway, toxicity assessment and mechanism

Abstract

Fe-MOF@g-C₃N₄/BiOI (FCN/BiOI) composites were fabricated via a simple hydrothermal synthesis method, and their performance in the photocatalytic degradation of ofloxacin (OFX) was systematically investigated to demonstrate the extraordinary capability of FCN/BiOI (with a g-C₃N₄ : Fe-MOF doping ratio of 1 : 2) for the treatment of OFX-contaminated water. The preparation of the composite resolves the inherent drawbacks of traditional single-phase photocatalytic materials, including weak visible light absorption capacity, low photon quantum yield, and poor separation efficiency of photogenerated electron–hole pairs. Photocatalytic degradation experiments revealed that the degradation efficiency of FCN/BiOI for OFX was 2.0 times higher than that of BiOI and 4.0 times higher than that of Fe-MOF. The enhanced photocatalytic activity of FCN/BiOI towards OFX degradation is attributed to the heterojunction constructed by doping graphitic carbon nitride (g-C₃N₄), which effectively modulates the band structure of MOFs to adapt to specific photoresponses. The catalyst exhibits excellent visible light harvesting and electron transfer properties, achieving a 97% removal efficiency of OFX within 45 min. This composite forms a type-I heterojunction and is applied for the photo-Fenton degradation of OFX under visible light, thereby enabling efficient antibiotic removal. Combined with experimental results and density functional theory (DFT) calculations, the synergistic photocatalytic mechanism of the synthesized material was systematically studied, and the toxicity of intermediates during the degradation process was also analyzed.