The correlation between molecular structure and superlubricity in homojunctions of 2D materials

Despite the abundant structure of two-dimensional (2D) materials in superlubricity research, a comprehension of the underlying structure principles governing their performance remains elusive. This paper comprehensively investigated the interlayer sliding behavior of several representative 2D material homojunctions, and elucidated the influence mechanism of molecular structure on their superlubricating properties. The interlayer friction of 2D material homojunctions were experimentally investigated using an innovative technique based on the orientation and transfer of nanosheets. The simulated results not only validate the widely recognized mechanisms of maximum energy corrugation (E_c) for interlayer friction and maximum binding energy (Γ_b) for interlayer adhesion, but also propose an energy-based index, E_c/│Γ_b│, to track the experimental trend of friction coefficient (μ) in accordance with molecular friction theory. Furthermore, two interlayer friction mechanisms, potential barrier and potential well, are resolved and the intrinsic relationship between the structural form and mechanism manifestation is elucidated. The efficacy of hybridization in the structural design of superlubricating materials has been theoretically demonstrated, as experimentally evidenced by the exceptional performance exhibited by metal-organic frameworks (MOFs) (μ: 5.5*10⁻⁴).