Highly efficient additive-free dehydrogenation of neat formic acid

Formic acid (FA) is a promising hydrogen carrier that can play an instrumental role in the overall implementation of a hydrogen economy. In this regard, it is important to generate H₂ gas from neat FA without any solvent and/or additive, for which existing systems are scarce. Here we report the remarkable catalytic activity of a ruthenium 9H-acridine pincer complex for this process. The catalyst is unusually stable and robust in FA, even at high temperatures, and can catalyse neat FA dehydrogenation for over a month, with a total turnover number of 1,701,150. It can also generate high H₂/CO₂ gas pressures from neat FA (tested up to 100 bars). Mechanistic investigations and density functional theory studies are conducted to fully understand the molecular mechanism of the process. Overall, the high activity, stability, selectivity, simplicity and versatility of the system to generate a CO-free H₂/CO₂ gas stream and high pressure from neat FA makes it promising for large-scale implementation. [Figure not available: see fulltext.].