Two-dimensional transition metal borides (MBenes), with orthorhombic crystals and wrinkled B-TM-B bonding networks, emerge as promising candidates for negative Poisson's ratio (NPR) materials. However, the electronic-structural synergy governing NPR in these metallic systems remains elusive. Here, using density functional theory calculations, we uncover an intrinsic strain-independent NPR in ${\mathrm{Ti}}_2{\mathrm{B}}_2$ MBene ($\nu =-0.10$ at $\theta ={45}^{\circ }$), maintaining across 0–30% strain—surpassing black phosphorus ($\nu =-0.027$) and graphene (strain-dependent $\mathrm{NPR}>18\%$). A mechanistic descriptor is established, quantifying NPR dependence on transition metal's electron affinity, electronegativity, and valence electron count. The NPR originates from synergistic wrinkle B-Ti-B bond-angle expansion and strong $p-d$ orbital hybridization. Remarkably, Cu doping further enhances the NPR of ${\mathrm{Ti}}_2{\mathrm{B}}_2$ to −0.25 via size effect and electronic modulation, enabling its potential applications for mechanically adaptive electronics and cyclic deformation-resistant Li-air battery electrodes.

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• Electronic structure
• Flexible electronics
• Mechanical deformation
• Mechanical properties of membranes
• Physics of computation
• 2-dimensional systems
• Density functional theory