Water stable SiO2-coated Fe-MOF-74 for aqueous dimethyl phthalate degradation in PS activated medium

The poor water stability of metal-organic frameworks (MOFs) significantly hindered their catalytic application in advanced oxidation system. A protective outer layer was an effective strategy to solve this problem. However, the commonly used coating techniques are too complicated or too difficult to accurately control, thus, the applicability was relatively low. In this study, a water stable MOF core-SiO2 shell nanomaterial (Fe-MOF-74@SiO2) was synthesized by a facile hydrothermal method, and applied to activate persulfate (PS) for dimethyl phthalate (DMP) degradation. The catalyst water stability and DMP degradation in the system were investigated, suggesting that the SiO2-coated catalyst was more stable and exhibited higher DMP degradation efficiency over the pure MOF. It was found that pH had negligible effects on Fe-MOF-74@SiO2 + PS system, while, higher temperature facilitated the degradation of DMP. The activation mechanism was studied by quenching experiments combined with electron paramagnetic resonance, indicating that SO4 center dot- played a major role in the activation of PS with Fe-MOF-74@SiO2 for DMP removal, while (OH)-O-center dot also involved in the catalytic process. Finally, possible DMP degradation pathways were proposed. These findings indicated that the core-shell structured Fe-MOF-74@SiO2 showed promise for DMP degradation by PS advanced oxidation system.