Achieving Amphibious Superprotonic Conductivity in a Cu I Metal–Organic Framework by Strategic Pyrazinium Salt Impregnation

Treatment of a pyrazine (pz)‐impregnated Cu I metal–organic framework (MOF) ( [1⊃pz] ) with HCl vapor renders an interstitial pyrazinium chloride salt‐hybridized MOF ( [1⊃pz⋅6 HCl] ) that exhibits proton conductivity over 10 −2  S cm −1 both in anhydrous and under humid conditions. Framework [1⊃pz⋅6 HCl] features the highest anhydrous proton conductivity among the lesser‐known examples of MOF‐based materials exhibiting proton conductivity under both anhydrous and humid conditions. Moreover, [1⊃pz] and corresponding pyrazinium sulfate‐ and pyrazinium phosphate‐hybridized MOFs also exhibit superprotonic conductivity over 10 −2  S cm −1 under humid conditions. The impregnated pyrazinium ions play a crucial role in protonic conductivity, which occurs through a Grotthuss mechanism.