Constructing MXene quantum dots decorated covalent organic frameworks as oil-based lubricant additive

Nanoadditives offer a promising way to reduce friction and wear. In this study, an organic–inorganic hybrid material composed of MXene quantum dots (MQDs) and cetyl trimethylammonium bromide decorated covalent organic frameworks (CNUS-2) is successfully constructed via an electrostatic self-assembly strategy. The combination of MQDs and CNUS-2 not only increases the interlayer spacing of NUS-2 but also mitigates the self-aggregation of MQDs, maximizing the advantages of their intrinsic characteristics. Owing to the synergistic lubrication effect of zero-dimensional MQDs and two-dimensional NUS-2, improved lubricity and interfacial bonding ability are realized. In addition, the relative slip between the CNUS-2@MQDs sheets can reduce friction and anti-wear. As expected, different levels of CNUS-2@MQDs effectively boost the tribological properties. The friction coefficient (0.097) and wear volume (1.48×10⁵ µm³) of PAO-10 oil are reduced by 46.7% and 92.6% respectively, after the introduction of the 3.0 wt% CNUS-2@MQDs nanocomposite. Furthermore, the abundant oxygen-containing functional groups in CNUS-2 can accelerate the formation of adsorption and tribochemical reaction films, whereas the MQDs can repair worn surfaces, resulting in superior lubrication performance under variable load, temperature, and frequency conditions. This work not only effectively improves lubrication performance by developing a unique CNUS-2@MQDs nanocomposite, but also provides a reference for the design of novel lubricant additives.