Surface-functionalized nanoMOFs in oil for friction and wear reduction and antioxidation

Engineering the surface and interface of nanomaterials is critical for enhancing interfacial compatibility and dispersion stability in liquid. In this paper, we report dialkyldithiophosphate (DDP) functionalized zirconium-based metal organic frameworks (Zr-MOFs) nanoparticles as lubricating oil additives that can achieve friction and wear reduction and antioxidation. DDP molecules were coordinatively grafted onto the MOFs nanoparticles (nanoMOFs) using ultrasonication assisted self-assembly. Compared with pristine nanoMOFs, dispersity of the DDP-modified ones was significantly improved in both organic solvents and base oil. Reduction in both coefficient of friction and wear volume was achieved by adding Zr-MOFs@DDP in oil, and their oxidation induction time was expanded much longer than that of the base oil. Additionally, the lubricating and antioxidative performance of the Zr-MOFs@DDP in oil were correlated with their concentration and BET surface area respectively. Our results establish surface-functionalized nanoMOFs as oil additives that can support friction and wear reduction and improve the antioxidative performance.