Triboelectric Nanogenerators Based on Composites of Zeolitic Imidazolate Frameworks Functionalized with Halogenated Ligands for Contact and Rotational Mechanical Energy Harvesting.

Triboelectric nanogenerator (TENG) based on the coupling effect of triboelectrification and electrostatic induction can convert mechanical motions into electric energy. Recent studies have found that metal-organic framework materials are promising triboelectric materials due to their large surface area and excellent tunability. In this study, we incorporated isostructural zeolitic imidazolate frameworks, ZIF-8-X (X = CH, Br, Cl), into poly(vinylidene fluoride) (PVDF) electrospun fibers and assembled them in TENG devices to investigate the underlying relationship between functional group electronegativity (via varied imidazolate linkers) and triboelectric output performance. Results show that ZIF-8-Cl/PVDF composite fiber demonstrated the highest average voltage and current output of 312.4 ± 2.0 V and 4.90 ± 0.07 μA, respectively, which are 3.8 and 5.5 times higher than that of the pristine PVDF. The practicality of ZIF-8-X-based TENG was tested for harvesting energy from oscillatory motions to power up LEDs and capacitors. A freestanding mode TENG based on ZIF-8-Cl was also designed to harvest rotational energy without physical contact for wider applications. The working mechanism of ZIF-8-X-based TENG was also revealed through nanoscale-resolved chemical studies, providing valuable insights into the design of MOF materials for improved performance of TENGs.