Boosting UHMWPE Self-Lubricating Performance via Embedding Porous Cobalt-Based Zeolitic Imidazolate Framework Oil-Nanocontainers

Zeolitic imidazolate frameworks (ZIFs) are ideal host materials in the adsorption and storage of lubricating oil due to their intrinsic features of high porosity, uniform pore size, and interconnected interior space, but they are much less exploited in oil-containing self-lubricating areas. Herein, an ultrahigh surface area cobalt-based ZIF material (ZIF-67) with periodic microporous channels is synthesized successfully and introduced as an oil-nanocontainer embedding in the UHMWPE matrix. The constructed composites not only produce an ultralow steady-state coefficient of friction of ∼0.03 in dry sliding but also present a significant enhancement in antiwear properties, which decreases by over 60% wear rate compared to pure UHMWPE. Combined tribological performance and wear track morphologies reveal that the stored poly-alpha olefin 6 (PAO6) can be squeezed out sustainably and steadily from the pore channels of ZIF-67 under frictional stress and forming liquid lubricating films in the frictional contact area, thus resulting in such a remarkable self-lubricating performance improvement. This study proposes a new guideline for the design of microporous framework materials applied in oil-containing self-lubricating areas.