MOF-derived Co/Zn single-atom catalysts for reversible hydrogenation and dehydrogenation of quinoline hydrogen carrier

Storage of hydrogen, particularly liquid organic hydrogen carrier (LOHC), has attracted much attention to address the problem of safe storage and transport of H2. N-heterocycles are promising hydrogen carriers for storing/releasing hydrogen through reversible catalytic hydrogenation/dehydrogenation cycles. Therefore, designing cost-effective, efficient, reusable single catalysts for both processes with high catalytic activity is currently of interest. Herein, we report the successful preparation of atomically dispersed Co/Zn single-atom catalysts on nitrogen-doped carbon by pyrolysis of bimetallic CoxZny-MOF-508@Melamine. The synthesized CoxZny-NC catalyst showed highly efficient catalytic activity for the reversible hydrogenation and dehydrogenation of quinoline derivatives in the same solvent. Catalytic reversible hydrogen storage/release was demonstrated for three consecutive cycles without losing efficiency. The main features of this work require low loading of catalysts compared to reported heterogeneous non-precious metal catalysts. A control experiment revealed that free N-H groups/N-atoms are essential for dehydrogenation/hydrogenation reactions, and a possible reaction mechanism was proposed.