Mechanochemical in-situ construction of ionic liquid-functionalized covalent organic frameworks for anti-wear and friction reduction

Herein, ionic liquid-functionalized covalent organic frameworks (COFs) were prepared via mechanochemical reaction. The rich-aldehyde terminated COFs (LZU1) was firstly synthesized via the excess aldehyde monomer and amino monomer. Then, the ionic liquid (NH₂-IL) with amino group can graft onto the aldehyde terminated-COFs through Schiff base reaction between amino and aldehyde group driven by ball milling, and then through anion-exchange with NTf₂^- resulting in the ionic liquid-functionalized COFs (LZU1-NH₂IL-NTf₂). The LZU1-NH₂IL-NTf₂ displays good lubricating performance as lubricant additive, the friction coefficient is maintained at 0.106 and the wear volume is reduced by 85.4% compared with 500SN. The remarkable lubrication performance is mainly due to the physical adsorption film promoted by ionic liquid and the robust protective film formed by tribochemical reaction.