Heavy doping of H^- ion in 12CaO·7Al₂O ₃

12CaO·7Al₂O₃ (C12A7, mayenite), which has a nanoscale porous structure that can accommodate extraframework species such as hydride (H^-), oxide (O^2-), hydroxide (OH^-) ions, and electrons, has been doped with H^- ions to investigate its effects as dominant extraframework species. Chemical doping with CaH₂ enables the concentration of H^- ions to reach almost the theoretical maximum. The concentration of H^- ions is characterized by optical absorption intensity ascribed to photoionization of H^- ions, and ¹H magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. Persistent electron generation, which is accompanied by the formation of an F absorption band and electrical conductivity, by irradiation with ultraviolet light at room temperature increases as the H^- ion doping increases until it reaches half the theoretical maximum and then decreases as the H^- ion concentration increases further. This dependence indicates that both H^- and O^2- ions are necessary for the generation of persistent electrons.