Additive‐Free Formic Acid Dehydrogenation Catalyzed by a Cp*Ir Complex with Pyridyl‐Pyrazole Ligand: Long‐Term Hydrogen Generation and Impurity Effects

Hydrogen generation from formic acid (FA), as one of the most promising hydrogen carriers, has attracted significant attention due to the growing demand for renewable energy carriers. FA dehydrogenation (HCOOH → H₂ + CO₂) offers an efficient and environmentally friendly pathway but remains challenging, particularly regarding catalyst durability. While numerous studies have focused on enhancing catalytic activity, this article emphasizes catalyst design for improved durability, leading to the development of a novel catalyst that achieves both high activity and long-term stability. Ir complexes with pyridyl-pyrazole ligands with electron-donating substituents on the pyridine and pyrazole moieties completed the reaction without apparent degradation under reflux conditions and exhibited excellent durability. Moreover, FA dehydrogenation using this catalyst was sustained over an extended period by continuously pumping a formic acid solution, generating 3.3 m³ of gases over 43 days. The effects of impurities on the catalytic reaction were also examined, revealing that NaCl significantly inhibited the reaction. These findings provide valuable insights into the practical application of hydrogen generation through FA dehydrogenation.