Proton-conductive metal-organic frameworks

Abstract

Proton-conductive electrolytes are key materials in fuel cells. We introduced acidic functional groups into a porous coordination polymer (PCP), or metalorganic framework (MOF), and constructed proton-conductive PCP/MOFs. To achieve this, a novel synthetic method for introducing acidic groups in PCP/MOF was invented. The proton conductivities of various PCP/MOF materials were investigated by AC impedance spectroscopy, and some of the materials showed high proton conductivity up to 8 × 10-3 S cm-1 at ambient temperature. We also investigated the dependency of proton conductivity on functional groups and found a relationship between proton conductivity, the acidity of the functional groups, and the hydrogen-bond networks formed inside the pores of PCP/MOFs. These PCP/MOF materials have high crystallinity, and the frameworks and arrangement of guests in the inner pore were clearly determined by X-ray crystallographic analysis. The relationship between proton conductivity and hydrogen-bond networks was investigated. This study thus establishes a novel field for investigating highly proton-conductive materials.