Metal-organic frameworks-induced Self-Poling effect of polyvinylidene fluoride nanofibers for performance enhancement of triboelectric nanogenerator

Metal-organic frameworks (MOFs) exhibit various unique properties, but these properties have not been fully utilized for the performance enhancement of triboelectric nanogenerator (TENG). The MOFs with MIL-101(Cr) structure is a nanomaterial designed for extremely large pore structures than conventional MOF structures to absorb and desorb various solvents, which induces a new phenomenon, self-polling effect (SPE) in the organic materials. We verified and suggested the SPE mechanism of the N, N-dimethylformamide (DMF) solvent by the MIL-101(Cr) structured MOFs in the polyvinylidene fluoride (PVDF) nanofibers. Because of the SPE, the MOFs-based composite NFs showed enhanced TENG output performances by additionally induced β-phase in the PVDF NFs even after the electrospinning process. The composite PVDF NFs with optimal MOF content of 0.8 wt% showed an output power density of 568.8 µW/cm2, which is larger by 8.96 times compared to the pure PVDF NFs. After the SPE process, the output power density increased to 871.2 µW/cm2, which is 13.7 times larger than that of pure PVDF NFs. Different from the pure PVDF NFs, the MOFs-based composite PVDF NFs showed improved output powers after the SPE process regardless of MOF contents. Based on excellent performance, the TENG with the MOFs-based composite PVDF NFs was sufficiently utilized as a self-powered triggering sensor for smart home devices that can wirelessly operate various electronic devices.