supplementary material

the computational methods used for hardness calculations; the mechanical stability criteria; the elastic constants of the porous carbon crystals proposed in this work; the convergence test of phonon calculations; atomic structures and phonon spectra of porous carbons; a schematic illustration of the experimental realization of the PC-O-5.6.8; and the partial band decomposed charge density of the valence band maximum and conduction band minimum for PC-O-5.8.12 and PC-O-5.8.