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

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.