Effect of Hydrogen-Bonding Networks in Water on Temperature and Relative Humidity Dependence of Proton Conductivity in Metal-Organic Frameworks
By Nguyen, My V.; Dong, Hieu C.; Nguyen-Manh, Duc; Vu, Nam H.; Trinh, Thuat T.; Phan, Thang B.
Published in Journal of Science: Advanced Materials and Devices
2021
Abstract
In this work, we study and discuss the proton conductivity properties of MOF-801. Specifically, MOF-801 possesses intrinsic proton carrier sites, μ3-OH groups, in clusters yielding the generation of hydrogen-bonding networks with guest water molecules at high relative humidity (RH), facilitating proton transport. Remarkably, this material has a high proton conductivity of 1.82 × 10-3 S cm-1 under 98% RH at 90 °C and maintains its performance over an extended time. Our investigations revealed that the increase in proton conductivity is correlated to numerous hydrogen bonds within the MOF structure. The activation energy of this process is low (Ea = 0.21 eV), showing that the protons hop through the membrane by the Grotthus mechanism. Interestingly, combining density functional theory (DFT) calculations with molecular dynamics (MD) simulations, it was shown that a water cluster mechanism dominates the proton conductivity in this material via the large number of hydrogen bonds formed at different temperatures and relative humilities.