A family of new organometallic liquid absorbents have been invented and are being developed for heat pump and cryocooler applications. Both hydrogen absorbing “HySorb liquids” and nitrogen absorbing “NiSorb liquids” have been synthesized in the laboratory and their properties are being measured. Previous research has shown that some organometallic substances can absorb large amounts of hydrogen — up to several weight percent, but all of the previously reported materials are solids. The only reversible hydrogen or nitrogen absorbing organometallic materials known that are liquids are the HySorb and NiSorb liquids. These liquid absorbents are environmentally clean, have 1–13 wt.% gas uptake capacity and have ΔH/cp up to 15 times higher than that of ammonia/water or lithium bromide/water, so more compact, higher power density heat pumps are possible. These liquids are also non-corrosive, compatible with oils and may be readily pumped through conventional heat exchangers, absorbers and desorbers. Compressor driven and heat driven heat pumps and cryocoolers are described. Analysis of the NiSorb heat pump indicates that high efficiencies are possible.