Catalytic Hydrogenation and Dehydrogenation Reactions of N-alkyl-bis(carbazole)-Based Hydrogen Storage Materials

Abstract

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 investigate 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 H-2 wt %, respectively, again depending on the alkyl chain length. All materials showed complete hydrogenation reactions under ruthenium on an alumina catalyst at 190 degrees C, and complete reverse reactions and dehydrogenation reactions were observed under palladium on an alumina catalyst at <280 degrees C. At this temperature, all the prepared compounds were thermally stable, and no decomposition was observed.