Size-Regulated Metal–Organic Frameworks with Mercaptobenzothiazole for Ga-Based Liquid Metal Encapsulation: A High Performance Oil-Based Additive

In this study, size-regulated MOFs (MZ) with high MBT loading were successfully synthesized by combining mercaptobenzothiazole (MBT), zinc salt, and 2-methylimidazole (2-MI). Subsequently, the MZ structure was utilized to encapsulate tannic acid-modified gallium-based liquid metal (GLM-TA), thereby acquiring a novel heterogeneous nanocomposite (GLM-TA@MZ). The results revealed that the as-prepared GLM-TA@MZ shows good antiwear and friction-reducing performance as an oil-based lubricant additive, the average friction coefficient was decreased to 0.091, and a wear volume was reduced to 0.95 × 10⁴ μm³, which corresponds to a decrease of 52.3 and 97.2% as compared to base oil PAO. The excellent tribological properties of GLM-TA@MZ can be attributed to physical adsorption on the friction pair, followed by tribochemical reactions. As a result, a thick friction protection film (thickness of about 100 nm) containing Ga, Zn, and S elements was formed, which effectively reduced the contact area between the friction pairs, resulting in improved tribological performance. This study provides insights into the design of MOF-based nanocomposites for lubricating applications.