Transition-Metal Nitroprussides Examined for Water Harvesting and Sorption Cooling

Transition-metal pentacyanonitrosylferrates, commonly known as nitroprussides, have a long and documented history. Here, we synthesize cobalt and nickel nitroprussides (NPs) in order to probe their use as sorbents for water and fluorocarbon uptake for potential water harvesting and cooling applications. These NPs show stable and reversible equilibrium sorption isotherms at room temperature with peak uptake values of ∼40 wt % for H₂O and ∼30 wt % for fluorocarbon R134a. At water harvesting conditions, working capacities of ∼19 wt % were obtained for NPs. At sorption cooling conditions, the working capacities favored nickel NP. Given the advantages of an easy, inexpensive, and scalable synthesis, this study demonstrates the potential for using nitroprussides for future water harvesting and adsorption cooling systems.