Metal-Organic Frameworks as Multifunctional Materials for Triboelectric Nanogenerators Applied in Self-Charging Power...

The singular porous structures of metal-organic frameworks (MOFs), with metal ions or clusters as central nodes and organic compounds as ligands, offer a wide range of environmental and energy-based applications. In particular, for prototypes of triboelectric nanogenerators, the versatile role of MOFs enables their use as friction-layer nanofillers and a means to tune the dielectric constant of tribopairs, thereby improving surface charge activity for both tribopositive and tribonegative layers. The functionalization of MOFs with standard electron-donating and -withdrawing groups and the production of composites improve both tribopairs abilities and the device's performance under high-humidity and high-temperature conditions. Also, strategies for faster charge-transfer rates in self-charging power sources are discussed, with a view to integrating MOF-based supercapacitors into all MOF devices that leverage the outstanding properties of these structures. In this Review, a comprehensive evaluation of strategies for using MOFs and their composites as nanofillers in tribopairs is provided, with a focus on the potential-well interpretation of doping processes in tribopairs and their impact on the overall performance of energy-harvesting devices and the extension in the limit of operation at high relative humidity, characterizing a critical drawback in TENGs based on standard tribolayers and for integrated devices in which the power output at interfaces can be controlled.