Study on the sliding tribological behavior of ZIF-8 under lubricating grease conditions

ZIF-8 is widely applied in lubrication, adsorption, and catalysis owing to its unique physicochemical properties. Previous experimental studies have demonstrated its feasibility as a lubricant additive. In the present work, the lubricating performance of ZIF-8 as an additive to lithium-based grease is quantitatively and dynamically analyzed at the atomic scale using molecular dynamics simulations. Friction wear experiments are also conducted to elucidate the lubrication mechanism of ZIF-8. The simulation and experimental results indicate that the incorporation of ZIF-8 effectively enhances the antifriction and antiwear characteristics of lithium grease. The most significant improvement in the lubrication performance of the grease is obtained at a mass fraction of 2.0 wt. % ZIF-8, which reduces the friction factor μ of the grease by about 17.0% and the wear by ∼40.0%. Furthermore, the molecular dynamics simulations reveal that ZIF-8 primarily functions as a ball bearing under low-load conditions. However, under high-load conditions, ZIF-8 undergoes significant deformation and primarily acts as a filler. This explains the experimentally observed significant reduction in friction coefficient after the addition of ZIF-8. The results of this study provide a theoretical foundation for the development of new environmentally friendly grease additives.