A porous polymer, poly-9,9′-spirobifluorene and its derivatives for storage of H2 are prepared through a chemical synthesis method. The porous polymers have high specific surface area and narrow pore size distribution. Hydrogen uptake measurements conducted for these polymers determined a higher hydrogen storage capacity at the ambient temperature over that of the benchmark materials. The method of preparing such polymers, includes oxidatively activating solids by CO2/steam oxidation and supercritical water treatment.