Catalytic hydrogenation and dehydrogenation reactions of n-alkyl-bis(Carbazole)-based hydrogen storage materials

Recently, there have been numerous efforts to develop hydrogen-rich organic materials because hydrogen energy is emerging as a renewable energy source. In this regard, we designed and prepared four new materials based on N-alkyl-bis(carbazole), 9,9^′-(2-methylpropane-1,3-diyl)bis(9H-carbazole) (MBC), 9,9^′-(2-ethylpropane-1,3-diyl)bis(9H-carbazole) (EBC), 9,9^′-(2-propylpropane-1,3-diyl)bis(9H-carbazole) (PBC), and 9,9^′-(2-butylpropane-1,3-diyl)bis(9H-carbazole) (BBC), to investi-gate their hydrogen adsorption/hydrogen desorption reactivity depending on the length of the alkyl chain. The gravimetric densities of MBC, EBC, PBC, and BBC were 5.86, 5.76, 5.49, and 5.31 H₂ wt %, respectively, again depending on the alkyl chain length. All materials showed complete hydrogenation reactions under ruthenium on an alumina catalyst at 190^◦C, and complete reverse reactions and dehydrogenation reactions were observed under palladium on an alumina catalyst at <280^◦C. At this temperature, all the prepared compounds were thermally stable, and no decomposition was observed.