Improving synergistic effects within metal-organic framework by modulating structural interpenetration for boosted photocatalytic peroxydisulfate activation

Metal-organic frameworks (MOFs) have shown significant potential in the photocatalytic activation of peroxydisulfate (PDS). Although many MOFs have been investigated for their ability to activate PDS, the impact of structural interpenetration on this process remains underexplored. In this study, MIL-88D(Fe₂Ni) and MIL-126(Fe₂Ni) were selected to systematically study this effect. Both MOFs are composed of 4,4'-biphenyldicarboxylic acid and [Fe₂NiO(COO)₆] clusters (abbreviated as Fe₂Ni), while the framework of MIL-126(Fe₂Ni) can be considered as a two-fold interpenetrating MIL-88D(Fe₂Ni) networks. The study shows that interpenetration not only enhances the structural rigidity and stability, but also facilitates the exposure of active sites. The structural interpenetration reduces the distance between Fe₂Ni clusters to 0.6 nm, which is thermodynamically favorable for PDS activation. Consequently, the photocatalytic activation of PDS by MIL-126(Fe₂Ni) is significantly promoted. The MIL-126(Fe₂Ni)/PDS system achieved a 96.5 % removal efficiency of ofloxacin (OFL) within 30 min, with a high degradation rate constant (k) of 0.10 min^-1. In addition, the MIL-126(Fe₂Ni)/PDS system can effectively remove various organic pollutants from different water bodies, even under outdoor sunlight irradiation. Fascinatingly, MIL-126(Fe₂Ni)@polyurethane sponges also can remove 98.4 % of OFL in 60 min, highlighting its potential for practical applications.