Achieving structural stability and high critical temperature $\left(T_c\right)$ in hydrides under ambient conditions remains a major challenge. A feasible design strategy integrates the advantages of two material classes: (i) B-C–based clathrate superconductors, which exhibit excellent structural stability at ambient or relatively low pressures, and (ii) hydrogen-based unit, which possesses the potential for high $T_c$. Guided by this strategy, we theoretically predict a hypothetical compound ${\mathrm{NH}}_4{\mathrm{B}}_2{\mathrm{C}}_8$ by embedding hydrogenated units into a B-C clathrate framework. Using the stochastic self-consistent harmonic approximation combined with machine-learning-accelerated structural sampling, we assess the impact of anharmonicity on its superconducting properties. Anharmonic effects harden the dominant phonon modes 13–15, reducing the electron-phonon coupling constant $\lambda$ from 1.43 to 1.22 and lowering $T_{\text{c}}$ from 102 to 91 K. Furthermore, hole doping realized by ${\mathrm{NH}}_4$ vacancy engineering, which yields ${\left({\text{NH}}_4\right)}_3{\left({\text{B}}_2{\text{C}}_8\right)}_4$, is demonstrated to be ineffective in enhancing $T_c$ under anharmonic conditions. Our results highlight the synergistic role between hydrogen units and B-C frameworks in enhancing superconductivity, and underscore the importance of anharmonicity in the design of such superconductors.

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• Superconductivity
• Carbon-based materials
• High-temperature superconductors
• Eliashberg theory
• First-principles calculations