Modulation mechanism of electron energy dissipation on superlubricity based on fluorinated 2D ZIFs

Electron energy dissipation is an important energy dissipation pathway that cannot be ignored in friction process. Two-dimensional zeolite imidazole frameworks (2D ZIFs) and fluorine doping strategies give 2D Zn-ZIF and 2D Co-ZIF unique electrical properties, making them ideal materials for studying electron energy dissipation mechanism. In this paper, based on the superlubricity modulation of 2D fluoridated ZIFs, the optimal tribological properties are obtained on the 2D F-Co-ZIF surface, with the friction coefficient as low as 0.0010. Electrical experiments, density functional theory (DFT) simulation, and fluorescence detection are used to explain the mechanism of fluorine doping regulation of tribological properties from the two stages, namely energy transfer and energy release. Specifically, the energy will transfer into the friction system through the generation of electron-hole pairs under an external excitation, and release by radiation and non-radiation energy dissipation channels. Fluorination reduces energy transfer by altering the electronic properties and band structures of ZIFs, and slows down the charge transfer by enhancing the shielding efficiency, thus slowing the non-radiative energy dissipation rate during the energy release stage. Our insights not only help us better understand the role of fluorine doping in improving tribological properties, but also provide a new way to further explore the electron energy dissipation pathway during friction.