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(FeNi) and MIL-126(FeNi) were selected to systematically study this effect. Both MOFs are composed of 4,4'-biphenyldicarboxylic acid and [FeNiO(COO)] clusters (abbreviated as FeNi), while the framework of MIL-126(FeNi) can be considered as a two-fold interpenetrating MIL-88D(FeNi) 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 FeNi clusters to 0.6 nm, which is thermodynamically favorable for PDS activation. Consequently, the photocatalytic activation of PDS by MIL-126(FeNi) is significantly promoted. The MIL-126(FeNi)/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. In addition, the MIL-126(FeNi)/PDS system can effectively remove various organic pollutants from different water bodies, even under outdoor sunlight irradiation. Fascinatingly, MIL-126(FeNi)@polyurethane sponges also can remove 98.4 % of OFL in 60 min, highlighting its potential for practical applications.