Ruthenium Nanoparticles In article number 2206806 by Alexis Bordet, Walter Leitner, and co-workers, the aqueous phase hydrogenation of CO2 to formate using Ru nanoparticles immobilized on supported ionic liquid phases ([email protected]) is reported. A synergistic enhancement of catalyst activity and productivity is observed for sulfonic acid-functionalized [email protected](SO3H-X) materials, and rationalized by an accelerated desorption of the formate species from the Ru NPs promoted by the presence of ammonium sulfonate species on these catalysts.