Two-Dimensional TpPa-1, TpPa-2, and TpBD Covalent Organic Frameworks as Novel Lubricant Additives for Friction and Wear Reduction

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Three two-dimensional Tp-based covalent organic frameworks, namely TpPa-1, TpPa-2, and TpBD, were synthesized and incorporated into Shell Helix H6 lubricating oil (SO) to investigate their potential as lubricant additives in commercial lubricating oils. Tribological tests demonstrated that all three Tp-based frameworks enhanced lubrication performance, with TpPa-1 exhibiting the best overall performance. Under a 5 N load, the coefficient of friction (μ) and wear rate decreased by 35.5% (to 0.091) and 55.9% (to 4.1 × 10−6 mm3/(N·m)), respectively. Under a 10 N load, μ and wear rate decreased by 38.3% (to 0.095) and 60.9% (to 4.8 × 10−6 mm3/(N·m)), respectively. The lubrication mechanism was attributed to interlayer sliding of the Tp-based framework nanosheets and the formation of a protective tribofilm containing iron oxides and deposited Tp-based frameworks, which filled wear pits and reduced wear volume.