A prolific catalyst for dehydrogenation of neat formic acid

Abstract

Formic acid is a promising energy carrier for on-demand hydrogen generation. Because the reverse reaction is also feasible, formic acid is a form of stored hydrogen. Here we present a robust, reusable iridium catalyst that enables hydrogen gas release from neat formic acid. This catalysis works under mild conditions in the presence of air, is highly selective and affords millions of turnovers. While many catalysts exist for both formic acid dehydrogenation and carbon dioxide reduction, solutions to date on hydrogen gas release rely on volatile components that reduce the weight content of stored hydrogen and/or introduce fuel cell poisons. These are avoided here. The catalyst utilizes an interesting chemical mechanism, which is described on the basis of kinetic and synthetic experiments.

Manganese‐Mediated Formic Acid Dehydrogenation

“…Our own research into FA dehydrogenation was centered on generating two moles of gas per one mole of liquid (HCO 2 H conversion into CO 2 and H 2 ), employing the volume change as a method of performing mechanical work ( δ W= δ PV) from chemical reactivity . Iridium and ruthenium catalysts have shown the most promise for expedient dehydrogenation of FA, with iridium systems capable of handling either aqueous or, importantly, neat conditions. Our previous report of a base‐assisted ( t Bu PONOP)RuHCl ( 6 ) catalyst exhibited high TOFs, generating hundreds of PSI of pressure in the desired short reaction times ( t Bu PONOP=2,6‐bis(di‐ tert ‐butylphosphinito)pyridine) under high FA concentrations (Figure ) .…”

Formic Acid Dehydrogenation by Ruthenium Catalyst – Computational and Kinetic Analysis with the Energy Span Model

“…[7][8][9] Suppression of decarbonylation is often attributed only to homogeneous catalysts. [7][8][9] Suppression of decarbonylation is often attributed only to homogeneous catalysts.…”

An Update on Formic Acid Dehydrogenation by Homogeneous Catalysis

“…This can also directly produce high‐pressure H 2 under very acidic conditions. Williams's group described an iridium−NP complex 4 (Figure ), which can continue to work up to 4 months and provide a TON of 2,160,000 under the neat FA condition . Fischmeister and co‐workers also reported an iridium complex with Cp*(dipyridylamine) ligand to selective decompose aqueous and neat FA under the base‐free conditions to give TOF of 13,292 h −1 at 100 °C .…”