A novel carbon-cage network was reported, denoted as C18, found to be a low energy structure by first principles particle swarm structure search. The compound exhibits high temperature electron–phonon ambient pressure superconductivity with Tc =79 K for elemental doping and can be raised to Tc =109 K by appropriate hole doping. Analyses of the phonon spectra, molecular dynamics simulations, and enthalpy differences relative to analogous structures synthesized experimentally all suggest that the hole-doped high-Tc structure is a viable candidate for experimental synthesis. Currently, synthesis studies combining high pressure and ion-beam irradiation are underway.