Experimental studies have reported that nitrogen (N)-doped orthorhombic $\alpha \text{−}{\mathrm{Mo}}_2\mathrm{C}$ exhibits a significant enhancement in its superconducting transition temperature ($T_c$). To elucidate the underlying mechanisms, we conducted a systematic first-principles investigation of N-doped $\alpha \text{−}{\mathrm{Mo}}_2\mathrm{C}$, focusing on its structural stability, electronic structure, phonon dynamics, and superconductivity. The results show that the superconductivity originates from the electron-phonon coupling (EPC) between $\mathrm{Mo}\text{−}4d$ orbital electrons and low-frequency vibrational modes of Mo atoms. As the N content increases, the $T_c$ exhibits a dome-shaped variation, well-consistent with experimental observations. Notably, varying the N-doping concentration drives a Lifshitz transition and a trivial-nontrivial-trivial topological evolution, as confirmed by Wannier-based $Z_2$ invariants. These findings provide important insights into the superconductivity and topology in N-doped $\alpha \text{−}{\mathrm{Mo}}_2\mathrm{C}$, and offer valuable guidance for the design of high-performance superconducting and topological quantum materials.

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• Electronic structure
• Superconductivity
• Superconductors
• Eliashberg theory
• First-principles calculations
• Wannier function methods