Graphene/Trione Covalent-Organic-Frameworks Nanocomposite: Complementarity in Structure and Properties Improving Tribological Behaviors of PEG Base Oil

Native defects of a single nanomaterial in properties and structure inevitably cripple its lubrication performance, when served as lubricant additives. In this work, manipulating the content of graphene to prepare the graphene/trione covalent-organic-frameworks (Ton-COFs; GTCC) nanocomposites has first come true the complementarity in structure and properties to enhance lubrication performance. Specifically, we apply graphene layers as a template whereon the Ton-COFs could grow into even and integral sheets at a well-screened graphene content, and the balance between the rigidity of Ton-COFs and the flexibility of graphene is also achieved, which enables the GTCC nanoadditive to self-adapt and cover over the rubbing surface as shapable as possible, forming a protective lubrication film. Besides, the strong affinity to metal of the polar groups and electron-rich heterocycle in Ton-COFs further consolidates the binding of the lubrication film. Eventually, with the assistance of the high mechanical strength of graphene and the incommensurate effect of the heterostructure, the GTCC nanocomposite with the content of graphene (75 mg) as the additive exhibits the optimal tribological performance, reducing friction by 33% and decreasing the wear volume by 96%, compared to that of poly(ethylene glycol) 400 base oil. This finding provides a strategy to promote the application of COFs as nanoadditives in practical lubrication.