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Abstract Efficient hydrogen storage and release are essential for effective use of hydrogen as an energy carrier. In principle, formic acid could be used as a convenient hydrogen storage medium via reversible CO 2 hydrogenation. However, noble metal-based catalysts are currently needed to facilitate the (de)hydrogenation, and the CO 2 produced during hydrogen release is generally released, resulting in undesirable emissions. Here we report an α -amino acid-promoted system for reversible CO 2 hydrogenation to formic acid using a Mn-pincer complex as a homogeneous catalyst. We observe good stability and reusability of the catalyst and lysine as the amino acid at high productivities (CO 2 hydrogenation: total turnover number of 2,000,000; formic acid dehydrogenation: total turnover number of 600,000). Employing potassium lysinate, we achieve >80% H 2 evolution efficiency and >99.9% CO 2 retention in ten charge–discharge cycles, avoiding CO 2 re-loading steps between each cycle. This process was scaled up by a factor of 18 without obvious drop of the productivity.
Wei et al. (Thu,) studied this question.