Mechanism of proton transport in water clusters and the effect of electric fields: A DFT study

Proton transport inside metal organics frameworks (MOFs) plays an important role to understand and develop a new type of material for a high conductivity application. One of the possible pathways of this process is via water cluster which is confined inside the MOFs structure. In this work, the mechanism of proton transport is investigated within the Density Functional Theory (DFT) calculations. Different water clusters from dimer to pentamer and octamer, which are equivalent to water structures inside the tetrahedral and cubic cavities of MOF-801, respectively, were systematically considered. The results show that proton transfer inside the pentamer cluster has the lowest barrier around 16 kJ/mol. Moreover, the presence of electric fields has a strong effect on the mechanism and energy profile of the proton transfer in both pentamer and octamer cluster. Our DFT prediction of proton migration energies is supported by experimental data of high conducting MOFs such as MOF-801.