A method for the reversible chemical storage of hydrogen, the method comprising: 1) a hydrogenation step, which comprises contacting hydrogen with carbon dioxide in the presence of a hydrogenation catalyst to effect storage of hydrogen by forming at least formic acid; and 2) a dehydrogenation step, which comprises converting a mixture comprising or consisting of a C 1 -C 18 alcohol and formic acid into hydrogen and carbon dioxide in the presence of a base and a) a transition-metal hydride catalyst or precursor thereof, the transition-metal hydride catalyst comprising: a metal-ion selected from the group consisting of Ru, Ir, Mn, Co, Mo, Fe and Rh, at least one hydride ligand coordinated to the metal-ion, and i) a tridentate ligand coordinated to the metal-ion and selected from the group consisting of a PNP -chelating ligand, a PNN -chelating ligand, a PCP -chelating ligand, an NCN- chelating ligand, a PCN -chelating ligand, a PPP -chelating ligand and an NNN -chelating ligand, or ii) one or two a bidentate ligand coordinated to the metal-ion and selected from a PP- chelating ligand or an NN- chelating ligand, or iii) a tetradentate PPPP- chelating ligand coordinated to the metal-ion; or b) a heterogeneous transition-metal catalyst. 1) a hydrogenation step, which comprises contacting hydrogen with carbon dioxide in the presence of a hydrogenation catalyst to effect storage of hydrogen by forming at least formic acid; and 2) a dehydrogenation step, which comprises converting a mixture comprising or consisting of a C 1 -C 18 alcohol and formic acid into hydrogen and carbon dioxide in the presence of a base and a) a transition-metal hydride catalyst or precursor thereof, the transition-metal hydride catalyst comprising: a metal-ion selected from the group consisting of Ru, Ir, Mn, Co, Mo, Fe and Rh, at least one hydride ligand coordinated to the metal-ion, and i) a tridentate ligand coordinated to the metal-ion and selected from the group consisting of a PNP -chelating ligand, a PNN -chelating ligand, a PCP -chelating ligand, an NCN- chelating ligand, a PCN -chelating ligand, a PPP -chelating ligand and an NNN -chelating ligand, or ii) one or two a bidentate ligand coordinated to the metal-ion and selected from a PP- chelating ligand or an NN- chelating ligand, or iii) a tetradentate PPPP- chelating ligand coordinated to the metal-ion; or b) a heterogeneous transition-metal catalyst. a) a transition-metal hydride catalyst or precursor thereof, the transition-metal hydride catalyst comprising: a metal-ion selected from the group consisting of Ru, Ir, Mn, Co, Mo, Fe and Rh, at least one hydride ligand coordinated to the metal-ion, and i) a tridentate ligand coordinated to the metal-ion and selected from the group consisting of a PNP -chelating ligand, a PNN -chelating ligand, a PCP -chelating ligand, an NCN- chelating ligand, a PCN -chelating ligand, a PPP -chelating ligand and an NNN -chelating ligand, or ii) one or two a bidentate ligand coordinated to the metal-ion and selected from a PP- chelating ligand or an NN- chelating ligand, or iii) a tetradentate PPPP- chelating ligand coordinated to the metal-ion; or a metal-ion selected from the group consisting of Ru, Ir, Mn, Co, Mo, Fe and Rh, at least one hydride ligand coordinated to the metal-ion, and i) a tridentate ligand coordinated to the metal-ion and selected from the group consisting of a PNP -chelating ligand, a PNN -chelating ligand, a PCP -chelating ligand, an NCN- chelating ligand, a PCN -chelating ligand, a PPP -chelating ligand and an NNN -chelating ligand, or ii) one or two a bidentate ligand coordinated to the metal-ion and selected from a PP- chelating ligand or an NN- chelating ligand, or iii) a tetradentate PPPP- chelating ligand coordinated to the metal-ion; or i) a tridentate ligand coordinated to the metal-ion and selected from the group consisting of a PNP -chelating ligand, a PNN -chelating ligand, a PCP -chelating ligand, an NCN- chelating ligand, a PCN -chelating ligand, a PPP -chelating ligand and an NNN -chelating ligand, or ii) one or two a bidentate ligand coordinated to the metal-ion and selected from a PP- chelating ligand or an NN- chelating ligand, or iii) a tetradentate PPPP- chelating ligand coordinated to the metal-ion; or b) a heterogeneous transition-metal catalyst.