Imparting High Proton Conductivity to a Metal–Organic Framework Material by Controlled Acid Impregnation

The extensive implementation of hydrogen-powered technology today is limited by a number of fundamental problems related to materials research. Fuel-cell hydrogen conversion technology requires proton-conducting materials with high conductivity at intermediate temperatures up to 120 °C. The development of such materials remains challenging because the proton transport of many promising candidates is based on extended microstructures of water molecules, which deteriorate at temperatures above the boiling point. Here we show the impregnation of the mesoporous metal–organic framework (MOF) MIL-101 by nonvolatile acids H2SO4 and H3PO4. Such a simple approach affords solid materials with potent proton-conducting properties at moderate temperatures, which is critically important for the proper function of on-board automobile fuel cells. The proton conductivities of the H2SO4@MIL-101 and H3PO4@MIL-101 at T = 150 °C and low humidity outperform those of any other MOF-based materials and could be compared with the best proton conductors, such as Nafion.