Two-dimensional (2D) transition metal carbides or nitrides (MXenes) provide a versatile class of materials with tunable surface chemistry and distinctive mechanical and electronic functionalities. Among them, Mo₂TiC₂T_x, a representative dual transition metal MXene, is distinguished by its electrochemical activity and energy storage capability. Since the reliability of such devices is closely linked to the mechanical response of their smallest structural units, a clear understanding of the intrinsic mechanical properties and fracture behavior of monolayer Mo₂TiC₂T_x is required. Here, using a Push-to-Pull (PTP) device inside a scanning electron microscope (SEM), we directly measure a Young’s modulus of 563.09 ± 11.27 GPa for freestanding monolayer Mo₂TiC₂T_x, consistent with density functional theory (DFT) predictions for dual transition metal MXenes. DFT calculation further tracks bond-length evolution and charge-density redistribution during uniaxial tension, clarifying the microscopic origin of the exceptional stiffness and strength. This work elucidates the physical origin of the enhanced mechanical properties of bimetallic MXenes, demonstrates their potential in advanced energy and functional material systems, and provides key experimental and theoretical insights for improving structural reliability and failure prediction in other 2D materials.

Nanoscale confinement environments often affect the transport mechanisms of nanofluids. Understanding the dynamic behavior of molecules in two-dimensional (2D) confined channels is of great importance in the areas of sensing, catalysis and energy storage. As a popular candidate for a new type of gas sensing material, MXenes have the problem of nonselectivity towards polar gases with slow responses, which severely limits their applications. Here, we report a study on regulating the confinement effect of 2D channels between MXene layers through annealing treatment and ion (Na⁺) intercalation for high-performance ammonia (NH₃) sensing. Firstly, the annealing treatment accurately modulates the size of the 2D channels to effectively block the entry of large-size gas molecules and improve the selectivity for NH₃. Ab initio molecular dynamics (AIMD) also confirms that the modulated channel size has a special "nano-pumping effect", which can accelerate the dynamic behavior of NH₃ molecules in the 2D confined space. Moreover, the intercalation of Na⁺ ions increases the adsorption capacity of NH₃. Therefore, the "nano-pumping effect" and theintercalation of Na⁺ ions effectively enhance the response speed and sensitivity of MXene to NH₃, respectively. The experimental results show that the modified Ti₃C₂ exhibits high sensitivity (0.17), rapid response (181 s), excellent selectivity and stability towards NH₃.