A possible method of hydrogen storage may be the reversible chemisorption of hydrogen on adsorbents formed from immobilized aromatic molecules. Hydrogenation and dehydrogenation of mononuclear aromatic compounds such as benzene, toluene, p-xylene, mesitylene and the polynuclear aromatics naphthalene, anthracene and fullerene C-60, chemisorbed on silica-supported platinum have been investigated by infrared spectroscopy. The complexes of these compounds with platinum can be easily both hydrogenated under relatively low hydrogen pressures, less than 1 bar, and dehydrogenated by evacuation even at ambient temperatures. The complexes of these compounds with Pt are rather stable and can gain and lose hydrogen many times. The complexes of the methyl-substituted benzenes, polyaromatic compounds, and fullerene C-60 with Pt are more thermostable and are retained at higher temperatures, at least at 323-373 K. Such complexes can be hydrogenated and dehydrogenated many times at these temperatures. Evidence in the literature suggests that chemisorbed complexes of long-chain alkenes or alkynes with metals show similar properties on hydrogenation and dehydrogenation. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.