Garlic Oil-Functionalized Covalent Organic Frameworks as Efficient Lubricant Additives for Synergistically Improved Tribological Performance

In this study, a functionalized fluorinated covalent organic framework (COF-F) was successfully constructed through a two-step procedure involving solvothermal synthesis followed by surface modification. Initially, amine-terminated COF-F was prepared by a solvothermal method. Garlic oil (GO) was then grafted onto COF-F via ball milling, utilizing the aza-Michael reaction between the amine groups of COF-F and the C═C bonds in GO, thereby obtaining garlic oil-functionalized COF-F (GO@COF-F). Tribological evaluation revealed that incorporating 1.00 wt % GO@COF-F into the base oil PAO10 significantly enhances its lubrication performance, as evidenced by a reduction in the average friction coefficient from 0.18 to 0.101 and a drop in the wear volume from 1.0 × 10⁶ to 1.6 × 10⁵ μm³. The exceptional enhancement primarily arises from the mending effect of GO@COF-F and the generation of a protective tribofilm through a tribochemical reaction with oxygen and the iron substrate, which results in the separation of the friction pairs and the prevention of direct asperity contact. Additionally, the GO@COF-F nanoadditive lowers the friction coefficient by promoting a change from sliding to rolling friction.