This paper discusses the synthesis of boron substituted carbon (B/C) materials by pyrolysis of two organic and polymeric precursors, which are prepared by chloroboration of phenylene acetylene and phenyl diacetylene, respectively. Some of the resulting B/C materials were evaluated in hydrogen physisorption from ambient to low temperatures under various hydrogen pressures. Evidently, through the precursor design it is possible to transform some B atoms in the precursor into B/C material by pyrolysis. Despite the dense structure (without significant porosity by SEM and BET), the B/C material with 1.6 wt% B content shows hydrogen adsorption 0.7 and 2.15 wt% at 25 and -78°C, respectively, under 1300 psi hydrogen pressure. The adsorption-desorption cycles were repeated many times without any detectable change. Apparently, the empty p-orbital in the substituted B atom increases the binding energy of hydrogen to the B/C surface of graphitic platelet, which is reversible by pressure and ambient temperature. copyright The Electrochemical Society.