Mechanistic Insights in Acceptorless Dehydrogenation of N-Heterocycles Using Graphenes as Carbocatalysts

Catalytic dehydrogenation is a critical transformation in the chemical and energy sectors, particularly for reversible hydrogen storage systems. One of the most promising systems for hydrogen storage is the development of liquid organic hydrogen carriers (LOHCs), which have the potential capacity of storing and releasing hydrogen gas on demand. Catalytic direct dehydrogenation represents a greener, promising method to generate hydrogen in situ from these hydrogen-dense carriers. The catalytic activity of graphene materials as metal-free carbocatalysts in the acceptorless dehydrogenation of N-heterocycles has been explored. Herein, a detailed mechanistic investigation has been conducted through both experimental (stoichiometric and masking experiments) and DFT calculations on the reaction mechanism. The proposed mechanism identifies <i>o</i>-quinone groups as the active sites responsible for catalysis, involving the transformation of <i>o</i>-quinone groups into epoxide intermediates, which release molecular hydrogen and regenerate the <i>o</i>-quinone groups, completing the catalytic cycle. This work provides insight into the design of efficient metal-free catalysts for their use in LOHCs storage systems, paving the way for sustainable energy solutions.