Synergistic Engineering of UiO-66 Frameworks via Compositional Tuning and Surface Wettability toward Enhanced Tribological Performance

Engineering the surface and interfacial architectures of nanomaterials is fundamental to bridging the gap between dispersion stability and tribological efficiency. Metal–organic frameworks (MOFs), characterized by their structural diversity and programmable surface chemistries, represent a burgeoning class of organic–inorganic hybrids for next-generation lubricant additives. Herein, we systematically decipher the synergistic interplay between metal-node identity (M = Ce, Zr, Hf) and surface amphiphilicity in steering the tribological behavior of UiO-type frameworks. Through precise amidation-induced grafting of gradient alkyl chains (C4/C8), we achieved nuanced control over surface hydrophobicity while maintaining structural integrity. Notably, the octanoic-functionalized Zr-UiO-66-NH2 exhibits exceptional lubrication performance in 500SN base oil; at a low loading of 0.2 wt %, it yields a 27% reduction in the steady-state friction coefficient and a remarkable 81% suppression in wear volume. Advanced surface analysis reveals that the alkyl-chain functionalization promotes the enrichment of aliphatic and carbonyl moieties at the sliding interface, effectively lowering interfacial adhesion and shear resistance. Furthermore, XPS depth profiling identifies a robust, protective tribofilm composed of MOF-derived inorganic clusters and organic decomposition products, which significantly enhances oxidative stability. This work provides a versatile strategy for the molecular-level engineering of MOF-based additives to meet the demands of high-performance lubrication technologies.