Among heterocycles, N-ethyl carbazole (NEC) is perhaps the most prominent example that has been studied in the context of reversible dehydrogenation . NEC has a hydrogen carrying capacity of 5.8 wt.%, and a dehydrogenation enthalpy in the range 50-53 kJ/mol H 2 . Upon complete dehydrogenation, perhydro-NEC (or H12-NEC) releases 6 moles of hydrogen in three stages, with H8-NEC and H4-NEC as the most stable intermediates . The dehydrogenation reaction starts from the five-membered ring and subsequently proceeds in the two six-membered rings as shown in Fig. .