Graphene/Trione Covalent-Organic-Frameworks\nNanocomposite:\nComplementarity in Structure and Properties Improving Tribological\nBehaviors of PEG Base Oil

Native defects of a single nanomaterial in properties\nand structure\ninevitably cripple its lubrication performance, when served as lubricant\nadditives. In this work, manipulating the content of graphene to prepare\nthe graphene/trione covalent-organic-frameworks (Ton-COFs; GTCC) nanocomposites\nhas first come true the complementarity in structure and properties\nto enhance lubrication performance. Specifically, we apply graphene\nlayers as a template whereon the Ton-COFs could grow into even and\nintegral sheets at a well-screened graphene content, and the balance\nbetween the rigidity of Ton-COFs and the flexibility of graphene is\nalso achieved, which enables the GTCC nanoadditive to self-adapt and\ncover over the rubbing surface as shapable as possible, forming a\nprotective lubrication film. Besides, the strong affinity to metal\nof the polar groups and electron-rich heterocycle in Ton-COFs further\nconsolidates the binding of the lubrication film. Eventually, with\nthe assistance of the high mechanical strength of graphene and the\nincommensurate effect of the heterostructure, the GTCC nanocomposite\nwith the content of graphene (75 mg) as the additive exhibits the\noptimal tribological performance, reducing friction by 33% and decreasing\nthe wear volume by 96%, compared to that of poly(ethylene glycol)\n400 base oil. This finding provides a strategy to promote the application\nof COFs as nanoadditives in practical lubrication.