The goal of net zero carbon emission is of a great concern to energy conservation and emission reduction. In aerospace and other industrial fields, one of main energy consumption forms is the friction between the motion pairs despite that energy consumption caused by equipment mass cannot be ignored. Therefore, ultra-low density self-lubricating composites with interpenetrating network (IPN) structure-liquid lubricant coupling mechanism is designed and prepared in this work to meet the pressing requirement of energy saving and emission reduction. The liquid lubricant is in situ locked into polyurethane acrylate (PUA) IPN structures (IPN-PUA structures). The thermodynamic, mechanical, and tribological properties, as well as the density-friction comprehensive properties of the material with IPN-PUA structures was studied. After locking the liquid lubricant into IPN-PUA structures, the material possesses not only excellent self-lubricating properties but also good micro-mechanical properties with the coefficient of friction (COF) of 0.0938, the wear rate of 6.58×10^-15 m³/(N•m) and nanoindentation modulus of 4.5 GPa. Such composite materials also possess an ultra-low density of 1.107g/cm³, which contributes to their excellent versatile self-lubrication and low-density characteristics when compared with other polymeric materials.

To expand the use of metal–organic frameworks (MOFs) based self-lubricating composite, flexible MOFs MIL-88D has been studied as a nanocontainer for loading lubricant. In this work, the mechanism of oleamine adsorption and desorption by MIL-88D was investigated through molecular simulations and experiments. Molecular simulations showed that the oleamines can be physically adsorbed into open MIL-88Ds with the Fe and O atoms of MIL-88D interacting with oleamine NH₂- group. Higher temperature can cause Ole@MIL-88D to release more oleamines, while higher pressure on Ole@MIL-88D caused less oleamines released. Moreover the Ole@MIL-88D was incorporated into epoxy resin (EP) for friction tests. The optimum mass ratio of MIL-88D to EP is 15 wt%, and the EP/Ole@MIL-88D prefers light load and high frequency friction. This work suggests that flexible MOFs can be used as a nanocontainer for loading lubricant, and can be used as a new self-lubricating composite.

To utilize Cu–benzene-1,3,5-tricarboxylate (Cu–BTC) adsorbed lubricant oils in the self-lubricating field, the adsorption properties of Cu–BTC on different 1-olefins must be clarified. In this work, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene were studied by the Monte Carlo method and experimentally. The adsorption limit of Cu–BTC for n-olefins was determined as 1-undecene by the adsorption isotherms. This suggested a limit for even straight-chain molecules to the adsorption of Cu–BTC. The maximum ratio of the olefin length of the largest pore diameter (L/D) of Cu–BTC was approximately 1.57. Furthermore, theoretical calculations (radial distribution function (RDF)) and experiments (infrared (IR) spectra) confirmed the interaction of n-olefin adsorbates and the Cu–BTC framework occurred between the –CH= of olefins and the Cu and O atoms of the Cu–BTC framework. This work adds to the understanding and investigation of the adsorption of liquid lubricants using Cu–BTC as a metal–organic framework (MOF).