Tuning Proton Conductivity by Interstitial Guest Change in Size‐Adjustable Nanopores of a Cu I ‐MOF: A Potential Platform for Versatile Proton Carriers

By exploiting the breathing behavior of nanopores, we have studied for the first time the dependency of the guest‐induced proton conductivity of an interpenetrated Cu I metal–organic framework (Cu I ‐MOF, [ 1 ]) on various guest molecules. Proton conductivities of over 10 −3  S cm −1 under humid conditions were induced by a series of guest molecules, namely N,N ‐dimethylformamide, dimethyl sulfoxide, diethylamine, 1,4‐dinitrobenzene, nitrobenzene, pyridine, and 1 H ‐1,2,4‐triazole. A detailed investigation of the guest‐incorporated complexes revealed that low‐energy proton conduction occurs under humid conditions through the Grotthuss mechanism in [ 1 ⊃NB] and through the vehicle mechanism in the rest of the complexes. Single‐point energy computations revealed considerable stabilization upon guest encapsulation. To the best of our knowledge, [ 1 ] represents the first example in which considerably high protonic conductivity is triggered upon the facile incorporation of small molecules of such a variety. The investigation portrayed herein may be a stepping stone towards the rational design of proton‐conducting materials for practical applications.