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

• Published in: Chemistry : a European journal Vol. 24; no. 4; pp. 872 - 880
• Main Authors: Khatua, Sajal, Bar, Arun Kumar, Sheikh, Javeed Ahmad, Clearfield, Abraham, Konar, Sanjit
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 19.01.2018
• Subjects: Chemistry; Conductivity; fuel cells; interpenetrated hosts; Metal-organic frameworks; porous metal–organic frameworks; proton carrier guests; Protons; Pyrazine; Sulfates; superprotonic conductivity
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.201704088

Treatment of a pyrazine (pz)‐impregnated CuI 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. Strategic single crystal to single crystal (SC–SC) transformation of a porous CuI metal–organic framework (MOF) resulted in a pyrazinium salt‐impregnated hybridized MOF featuring the first example of superprotonic conductivity both in anhydrous and under humid conditions.