CO₂-mediated hydrogen storage and release cycles realized by a bimetallic ruthenium complex in pure water

CO2-mediated liquid H2 storage is a promising technology; however, it typically requires additives such as bases, which increase both cost and energy consumption. Herein, a bimetallic Ru complex is fabricated that catalyzes reversible cycles of CO2 hydrogenation to formic acid (FA) and FA dehydrogenation in pure water without any additives. The H2 storage and release cycles are controlled simply by varying the H2 pressure at 80 degrees C. Moreover, the system maintains its activity over at least 15 cycles (240 h), achieving a cumulative H2 storage of nearly 2000 mu mol. Labeling experiments using 13CO2 and D2 confirm the origins of the C and H atoms in FA. This efficient, green, and mild system demonstrates potential for sustainable hydrogen energy applications.