Metal Organic Framework Derived Porous BiFeO₃/PVDF Composites for Synergistic Piezo-Photocatalytic Degradation of...

Photocatalysis and piezocatalysis rely on light energy and mechanical energy (via the piezoelectric effect) as driving forces, respectively. Both have been successfully applied to pollutant degradation and wastewater treatment as advanced oxidation processes. However, in this study, BiFeO₃ nanoparticles derived from MIL-101 were solidified in a flexible polyvinylidene fluoride (PVDF) porous structure, forming a dynamic synergistic effect between the piezoelectrically polarized electric field induced by mechanical agitation and the photogenerated carriers. Additionally, the hydrolytic inactivation of the material was inhibited by the chemical barrier effect of PVDF, while the charge separation at the heterojunction interface was directionally driven by the built-in electric field generated by the piezoelectric effect. The BiFeO₃/PVDF composite membrane degraded 97.1% of RhB after 60 min of treatment under the synergistic effect of stirring and light. Free radical trapping and electron spin resonance (ESR) analysis confirmed that ^•O₂^- and ^•OH were the key active species (contributing over 60%). Piezoresponse Force Microscopy (PFM) test revealed the mechanism behind the enhancement of the built-in electric field, and density functional theory (DFT) calculations combined with Fukui's function elucidated that the N4, N5, and C6 sites in the RhB molecule were the preferred targets for free radical attack. Plant growth experiments verified the environmental safety of the system. The BiFeO₃/PVDF porous composites with piezoelectric photocatalytic properties proposed in this study provide a promising solution for developing novel materials for efficient catalysis of organic pollutants in water.