Enhanced Proton\nConductivity Promoted by Structural\nTransition in a 2D Interwoven Metal–Organic Framework

We report enhanced\nproton conductivity promoted by a\nstructural\nphase transition of MFM-504(Cu)-DMF to MFM-504(Cu)-MeOH and to MFM-504(Cu)-OH\nvia ligand substitution upon exposure to MeOH and H<sub>2</sub>O vapors,\nrespectively. MFM-504(Cu)-DMF can be synthesized by the solvothermal\nreaction of Cu(NO<sub>3</sub>)<sub>2</sub>·3H<sub>2</sub>O and\nthe flexible zwitterionic ligand, imidazolium-1,3-bis(methylenedicarboxylate)\n(imidc<sup>–</sup>), to afford a unique layered interwoven\nnetwork structure. MFM-504(Cu)-OH shows a proton conductivity of 5.01\n× 10<sup>–4</sup> S cm<sup>–1</sup> at 80 °C\nand 99% relative humidity (RH) with an activation energy (<i>E</i><sub>a</sub>) of 0.80 eV, indicating a vehicle mechanism\nwithin MFM-504(Cu)-OH.