TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The extended pi-conjugated substrate is large polycyclic aromatic hydrocarbons, polycyclic aromatic hydrocarbons with nitrogen or oxygen heteroatoms polycyclic aromatic hydrocarbons with ketone groups in the ring structure, pl-conjugated aromatic molecules comprising 5-membered rings, pi-conjugated aromatic molecules comprising 6- and 5-membered rings with nitrogen or oxygen heteroatoms in the 5-membered ring structure, or pi-conjugated organic polymers and oligomers. It is preferably pyrene, perylene, chrysene, triphenylene, coronene, hexabenzocoronene, ovalene, picene, rubicene, fluorene, indene, acenanaphthylene, carbazole, 1,4,5,8,9,12-hexaazatriphenylene, phenanthroline, quinoline, acridine, dibenzofuran, polypyrrole, polyindole, poly(methylcarbazole), polyacenanaphthylene, polyaniline, polyindene, or poly (9-vinylcarbazole). The extended pi-conjugated substrate comprises a polycyclic aromatic hydrocarbon comprising a fused ring system having at least4 rings, where at least2 the rings of the fused ring system are represented as 6-membered aromatic sextet structures; a polycyclic aromatic hydrocarbon with at least2 fused carbon ring structures, where at least1 of the carbon ring structures comprises a ketone in the carbon ring structure and the carbon ring structure with the ketone is fused to at least1 carbon ring structure which is represented as an aromatic sextet; a polycyclic aromatic hydrocarbon additionally comprising a 6-membered aromatic sextet ring fused with a 5-membered ring structure; a polycyclic aromatic hydrocarbon comprising at least2 rings, where at least1 of the rings is a 6-membered aromatic sextet structure and at least1 ring contains a nitrogen or oxygen heteroatom; a polycyclic aromatic hydrocarbon additionally comprising nitrogen or oxygen heteroatoms within the ring structure; a mixture of at least2 different extended pi-conjugated substrates; an organic polymer or oligomer comprising at least2 repeat units containing aromatic sextet(s) of conjugated bonds; an organic polymer or oligomer comprising at least2 repeat units containing a 5-membered ring structure with two double bonds and a heteroatom from nitrogen, oxygen or sulfur; or an organic polymer or oligomer comprising at least2 repeat units containing 5- and 6-membered ring structures. The polycyclic aromatic hydrocarbon additionally comprises a ring substituent from alkyl, alkoxy, ether, or polyether. The repeat units comprise ring structures with ring heteroatoms from nitrogen or oxygen. The dehydrogenation catalyst comprises an acidic support from silica-alumina, gamma-alumina, zeolites in the proton-exchanged form, sulfonated zirconia, solid perfluorinated polymeric sulfonic acids, aluminum trifluoride, aluminum chlorofluorides, zinc chloride, aluminum chloride, tin chloride, copper trifluoromethane sulfonate, scandium trichloride, hexafluoroacetylacetonate of complexes of the members of the Lanthanide series of elements according to the Periodic Table according to the International Union of Pure and Applied Chemistry.    TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Process: The contacting steps are conducted within a single vessel. The hydrogenation catalyst also functions as the dehydrogenation catalyst. The extended pi-conjugated substrate in the first contacting step resides in the liquid state. The first contacting step is conducted in a first vessel. The partially hydrogenated extended pi-conjugated substrate in the second contacting step resides in the liquid state. The second contacting step is conducted in a second vessel. The partially hydrogenated extended pi-conjugated substrate has a melting point of below -10degreesC or below 100degreesC. The process further comprises removing the hydrogenation catalyst from the partially hydrogenated extended pi-conjugated substrate obtained from the first contacting step prior to the second contacting step. The second contacting step is conducted at a temperature below 250degreesC and at a hydrogen partial pressure greater than approximately 0.1 (preferably approximately 1) bar. The extended pi-conjugated substrate is subjected to the first contacting step while present in the mixture of at least2 different extended pi-conjugated substrates with a freezing point of less than 200degreesC. The process for the storage of hydrogen comprises contacting hydrogen gas with a solid extended pi-conjugated substrate in the presence of an amount of the hydrogenation catalyst under hydrogenation conditions to at least partially hydrogenate the extended pi-conjugated substrate. It may comprise contacting hydrogen gas at a hydrogen partial pressure greater than 6.7 bar and at 50-300degreesC with a solid extended pi-conjugated substrate in the presence of an amount of the hydrogenation catalyst to at least partially hydrogenate the extended pi-conjugated substrate. The extended pi-conjugated substrate in the first contacting step is contained within a natural pitch or a synthetic pitch. Preferred Component: The hydrogen released in the second contacting step is at least1 wt.% of the weight of the partially hydrogenated extended pi-conjugated substrate.Preferred Properties: The experimentally determined modulus of the standard enthalpy change of hydrogenation of the extended pi-conjugated substrate is less than 15.0 (preferably 15.6) kcal/mol hydrogen (H2). The extended pi-conjugated substrate has a normal freezing point above 200degreesC. The partially hydrogenated extended pi-conjugated substrate has a freezing point of less than 100 (preferably less than 10)degreesC.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The hydrogenation catalyst comprises a metal from groups 4, 5, 6, 8, 9, or 10 of the Period Table according to the International Union of Pure and Applied Chemistry. The metal is preferably titanium, zirconium, cobalt, niobium, tantalum, iron, molybdenum, tungsten, ruthenium, rhodium, iridium, nickel, palladium, or platinum.