Flexible zwitterionic arm post-modificated UiO-66 for high and ultra-fast proton conduction

Metal-organic frameworks (MOFs) based proton conductors, as a promising alternative to proton exchange membranes, are in urgent need of developing effective methods to enhance their proton conductivity. Here, we report the enhanced and ultra-fast proton conduction facilitated by the post-covalent bonding of the flexible zwitterionic arm (sulfobetaine methacrylate: SBMA) with UiO-66. A new zwitterionic MOF based proton conductor (UiO-66-SB) exhibits the higher proton conductivity of 0.1 × 10 −2 S·cm −1 but with the activation energy ( E a ) of only 5.8 kJ/mol at 85 °C and 90 % RH, indicating ultra-fast proton transport. This result was attributed to the continuous and shorter hydrogen bonded network formed by flexible zwitterionic arms, water molecules, and residual –NH 2 . This work also demonstrates that zwitterions are highly advantageous as proton carrier media for the post-modification of MOFs.