Tribological Properties of Typical Zeolitic Imidazolate Frameworks as Grease-Based Lubricant Additives
In this study, three different zeolitic imidazolate framework (ZIF) materials of ZIF-8, ZIF-71, and MAF-6 were synthesized, and their tribological properties as base grease were evaluated. We demonstrate that the tribological properties of ZIFs are correlated with the framework density/pore volume and the substituted groups. Under 200 N, MAF-6 has the lowest wear volume value and ZIF-71 exhibits the lowest friction coefficient. As the load increased, MAF-6 maintained the best and most stable tribological performances among the three ZIFs additives; however, the properties of ZIF-71 worsened. Thus, MAF-6 exhibits the lowest density and largest solvent-accessible volume (SAV) and has the lowest elastic stiffness; it easily slides and adheres onto the wear surface, forming a tribofilm that reduces friction and prevents severe wear. ZIF-71 with chlorinated groups may enhance the tribological performance; as the load rises, its dense and stiff structure has an adverse effect. These results are expected to be helpful for designing future ZIFs with excellent lubrication properties.
Keywordsframework group lubricant additive tribological properties wear zeolitic imidazolate framework
This work was supported by the National Natural Science Foundation of China (Grant Nos. 21436008, 21503165, 21776198 and 21822808).
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