Interfacial Coupling in Few-Layered Graphene and Metal Organic Framework-Incorporated Poly(vinylidene Fluoride) Nanocomposites Enabling Piezoelectric Energy Harvesting and Piezocatalytic Reduction of Hexavalent Chromium

This study reports the interfacial engineering of poly(vinylidene fluoride) (PVDF) nanocomposites using a hybrid nanofiller comprising few-layered graphene and a copper-based metal-organic framework (Cu-MOF) to simultaneously enhance piezoelectric energy harvesting and piezocatalytic activity. The nanocomposites were prepared via melt-mixing followed by solution-casting, enabling uniform hierarchical nanofiller dispersion and strong interfacial coupling with the PVDF matrix, as observed from detailed vibrational spectroscopy and microscopic analyses. FT-IR analysis revealed a remarkably high electroactive β/γ-phase content (∼97.2%) for 1.5 wt % hybrid nanofiller concentration, arising from synergistic dipole-dipole and ion-dipole interactions at the polymer-nanofiller interfaces. The corresponding piezoelectric nanogenerator delivered an open-circuit voltage of ∼58.3 V, a peak-to-peak voltage of ∼88.9 V, and a power density of ∼52.7 μW cm^-2. Beyond energy harvesting, the PGM-1.5 nanocomposite film exhibited efficient dark piezocatalytic reduction of toxic Cr(VI) to Cr(III) (∼50% removal) under ultrasonic excitation, driven by mechanically induced polarization rather than cavitation or adsorption. Broadband dielectric spectroscopy, ferroelectric studies, and postcatalytic film stability analyses further confirmed lower dielectric losses for PVDF hybrid nanocomposites compared to neat PVDF, rapid interfacial charge dynamics, and structural robustness. These findings establish the Cu-MOF/graphene-engineered PVDF nanocomposite as a multifunctional platform for mechanically driven energy and environmental applications.