Superprotonic Conductivity of MOF‐808 Achieved by Controlling the Binding Mode of Grafted Sulfamate

Abstract A metal–organic framework (MOF) having superprotonic conductivity, MOF‐808, is prepared by modulating the binding mode of the sulfamate (SA) moieties grafted onto the metal clusters. The activation of the SA‐grafted MOF‐808 at 150 °C changes the binding mode of the grafted SA from monodentate to bridging bidentate, thus converting the neutral amido (‐S−NH 2 ) moiety of the grafted SA to the more acidic cationic sulfiliminium (‐S=NH 2 + ) moiety. Further, the acidic sulfiliminium moiety of MOF‐808‐4SA‐150 results in more efficient proton conduction than the amido moiety of MOF‐808‐4SA‐60. At 60 °C and 95 % relative humidity, MOF‐808‐4SA‐150 is found to have a proton conductivity of 7.89×10 −2 S cm −1 , which is more than 30‐times higher than that of MOF‐808‐4SA‐60. Moreover, this superprotonic conductivity is well maintained over 1000 cycles of conductivity measurements and for similar cyclic measurements each day for seven days.