Electrospun PVDF/Fe-BTC nanofibers for ultrasound-driven piezocatalytic degradation of methylene blue

Abstract Hybrid piezocatalytic membranes based on polyvinylidene fluoride (PVDF) and Fe-BTC metal–organic framework was fabricated by electrospinning at different applied voltages (20 and 50 kV) to investigate structure–property–function relationships under ultrasonic activation. The incorporation of Fe-BTC significantly reduced the fiber diameter from the micrometer to the nanometer range and resulted in the formation of uniform nanofibrous networks with embedded MOF aggregates. Structural characterization by SEM, FTIR, XPS and DSC confirmed successful integration of Fe-BTC into the PVDF matrix while preserving the electroactive β-phase. The membrane produced at 20 kV exhibited a narrower fiber diameter distribution (100–300 nm) and higher crystallinity (41.6%) compared to the 50 kV sample (36.9%). Piezocatalytic performance was evaluated in the degradation of methylene blue under ultrasound irradiation (40 kHz, 120 W). The PVDF/Fe-BTC-20 membrane achieved 90.6% degradation within 60 min with an apparent rate constant of 0.040 min −1 , significantly outperforming both the 50 kV membrane (k = 0.026 min −1 ) and sonolysis alone (k = 0.009 min −1 ). Radical trapping experiments revealed that hydroxyl radicals ( • OH) are the dominant reactive species, while electrons and holes also contribute to the process and superoxide radicals play a secondary role. Piezoelectric nanogenerator measurements demonstrated an open-circuit voltage up to 12.6 V for the 20 kV membrane, directly correlating enhanced piezoelectric output with higher catalytic efficiency. The improved performance is attributed to more efficient piezoelectric field generation, enhanced charge separation, and interfacial field modulation at the PVDF/Fe-BTC boundary. The developed MOF/polymer nanofibrous membranes represent a promising platform for ultrasound-driven water purification and expand the application scope of MOF-based composites into piezocatalysis.