Simple 1-alkyl(aryl)-3-methylimidazolium N-bis(trifluoromethanesulfonyl)imidate salts that possess very low vapor pressure, high density, and thermal stability and are not inflammable can add reversibly 6-12 hydrogen atoms in the presence of classical Pd/C or Ir-0 nanoparticle catalysts and can be used as alternative materials for on-board hydrogen-storage devices. These salts can hold up to 30 g L-1 of hydrogen at atmospheric pressure, which is twice that compressed hydrogen gas can attain at 350 atm.