Reversible Hydrogenationof CO₂ to FormamidesUsing an Atomically Dispersed Ir/C₃N₄ Catalyst

Abstract

The utilization of different energy carriers to efficiently store and release energy plays a vital role in the pursuit of a renewable energy paradigm. In this context, we present an interesting system utilizing morpholine as a dual-functional agent in the reversible hydrogenation of CO₂ to formamides employing an atomically dispersed iridium (Ir) catalyst. Morpholine serves as a stabilizer during CO₂ hydrogenation and a CO₂ capture agent during dehydrogenation, enabling a carbon-neutral cycle for hydrogen storage. Notably, these reversible cycles could be facilitated by the same catalyst and maintained under identical temperature conditions by a simple H₂ pressure swing. The robustness of this system is underscored by its consistent performance across multiple charging–discharging cycles without a noticeable reduction in the storage capacity. Additionally, the Ir catalyst exhibits strong CO tolerance during hydrogenation, making it suitable for purifying crude hydrogen via the reversible process.