Two-dimensional (2D) boron-based materials are promising candidates for high-temperature superconductors. Authors of most studies have focused on stabilizing honeycomb and kagome boron layers by intercalating metals to tune σ- and π-electron states at the Fermi level. However, the specific roles of these electrons in superconductivity remain unclear. Here, we propose a structural resonance strategy to stabilize 2D boron-based materials, exemplified by ${\mathrm{B}}_6{X}_4$ ($X$ = S, Se, and Te) monolayers. These structures, composed of ${\mathrm{B}}_6$ hexagonal rings and ${\mathrm{B}}_3{X}_2$ trigonal bipyramidal units, enforce exclusive σ bonding within ${\mathrm{B}}_6$ rings due to the tetrahedral bonding configuration of boron. Meanwhile, variations in the electronegativity of $X$ elements modulate the electron occupancy of B–B bonds, thereby altering the Fermi-level electronic states. First-principles calculations confirm that these structures exhibit high cohesive energy and strong dynamical stability. Among them, ${\mathrm{B}}_6{\mathrm{S}}_4$, which has the largest B–B σ-orbital electron contribution at the Fermi level, displays the highest superconducting transition temperature ($T_{\mathrm{c}}\approx 33$ K). This sharply contrasts with the lower $T_{\mathrm{c}}$ values of ${\mathrm{B}}_6{\mathrm{Se}}_4$ (24 K) and ${\mathrm{B}}_6\mathrm{T}{\mathrm{e}}_4$ (1.71 K), which correspond to a reduced B–B σ-electron contribution. Additionally, ${\mathrm{B}}_6{\mathrm{S}}_4$ exhibits single-gap superconductivity dominated by B-B σ electrons, which is different from multigap boron-based superconductors that rely on both σ and π electrons. These findings highlight the critical role of B–B σ-orbital electrons in superconductivity and provide insights into the design of 2D boron-based superconductors with tunable electronic properties.

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• Superconductivity
• 2-dimensional systems
• Density functional theory
• First-principles calculations