TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: In the methods (M2), the catalyst comprises at least one member selected from rhenium, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium and/or platinum. In the method (M3), the catalyst comprises at least one member selected from rhenium, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium and/or platinum (preferably platinum/rhenium on alumina and platinum/iridium on alumina).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The releasing and subsequent storing of hydrogen involves: contacting at least one, at least partially hydrogenated extended pi-conjugated substrate under dehydrogenation conditions in the presence of at least one catalyst to release hydrogen from the substrate, where substrate comprises the at least one conformer, and is a liquid during the contacting; recovering the substrate; and contacting the substrate with hydrogen while in the presence of at least one hydrogenation catalyst to hydrogenate the substrate. In the process (M2), the modulus of the standard enthalpy change of hydrogenation of the substrate is less than about 15.0 kcal/mole H2. Preferred Components: In the method (M2), the substrate comprises perhydroindolo(3,2,1-jk)carbazole; at least one member selected from perhydrodibenzofuran and further comprises dodecahydrobiphenylene; perhydro-N,N'-diethyl-bis-indolymethane; perhydro-N-ethylcarbazole; 10-methyl-10H-phenoxazine; at least one higher energy non-equilibrium conformers; at least one member selected from 1,2-dimethylindole, 1-ethyl-2-methylindole, N-methylcarbazole, N-ethylcarbazole, N-n-propylcarbazole, dibenzolfuran and 4H-benzo(def)carbazole; or fluorene. In the method (M2), the substrate comprises at least one heteroatom selected from oxygen, boron and nitrogen. In the process (M4), the substrate comprises a fluorene. In the method (M3), the conformer comprises at least one non-equilibrium conformer of at least one member selected from perhydroindolo(3,2,1-jk)carbazole, perhydrodibenzofuran, dodecahydrobiphenylene, perhydro-N,N'-diethyl-bis-indolymethane, perhydro-N-ethylcarbazole, perhydro-N-methylcarbazole, and 10-methyl-10H-phenoxazine; and the conformer comprises at least two conformers. EXAMPLE - Dehydrogenation of liquid pyrene under 0.15 to 0.26 Bar Hydrogen Pressure was carried out as follows: A sample of substantially hydrogenated pyrene (0.4 g) (h-pyrene) and platinum on carbon catalyst (0.2 g) were placed in a high pressure reactor equipped with a customized grinding apparatus. Once the sample mixture and grinding balls were loaded into the reactor, the system was evacuated for 5 minutes and pressurized with helium to 700 psia and vented. Pressurization and venting with helium was repeated three times. The system was again evacuated and filled with a 15% hydrogen/85% helium mixture. The sample was dehydrogenated by grinding at 160degrees C under a 15% hydrogen/85% helium mixture for 24 hours, initially at 15 psia (1 bar) for a hydrogen partial pressure of 2.25 psia (0.1 bar) and, over the course of the heating and evolution of hydrogen from the dehydrogenation reaction, the pressure increased to 24 psia (1.7 bar) for a hydrogen partial pressure of about 3.6 psia (0.26 bar). After reaction, the reactor was quickly cooled to room temperature and vented. The sample mixture (dehydrogenated-pyrene) was removed from the reactor and separated from the catalyst by extraction with chloroform and filtering of the insoluble catalyst. The gravimetric hydrogen storage capacity of the hydrogenated pyrene+catalyst was 4.7 wt.% and after dehydrogenation the capacity was reduced to 3.7 wt.% hydrogen. This corresponded to approximately 21% of the stored hydrogen being released during dehydrogenation of hydrogenated-pyrene.