Developing general design principles for two-dimensional (2D) high-$T_c$ superconductors remains a central challenge because reduced dimensionality fundamentally reshapes chemical bonding and electron-phonon interactions. Here, we identify a hybridization-based design principle for 2D hydrides, namely, strong $\sigma$-type hybridization between H $1s$ and transition-metal $e_g$ states that leaves the corresponding antibonding states partially occupied at the Fermi level. Guided by this principle, we show that monolayer ${\mathrm{NiH}}_3$, consisting of an edge-sharing ${\mathrm{NiH}}_6$ octahedral network, is a phonon-mediated superconductor with a predicted $T_c$ of 104 K. This high $T_c$ arises from strong coupling between the partially occupied Ni $e_g\text{−}\mathrm{H} 1s$ antibonding states near the Fermi level and Ni-dominated phonon modes. To demonstrate the generality of this principle, we further examine hole-doped ${\mathrm{CuH}}_3$ (0.1 hole/f.u.), which also exhibits superconductivity through the same hybridization mechanism, but with a reduced $T_c$ of 30 K because the Cu $e_g\text{−}\mathrm{H} 1s$ antibonding states are more fully occupied and thus contribute less to the density of states at the Fermi level and to the electron-phonon coupling. Our results provide a feasible route to enhancing electron-phonon coupling in 2D hydrides and highlight hybridization engineering as a promising strategy for designing high-$T_c$ superconductors.

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• Electron-phonon coupling
• Superconductivity
• Hydrides
• Monolayer films
• Density functional calculations