Proton Conduction in a Phosphonate-Based Metal–Organic Framework Mediated by Intrinsic “Free Diffusion inside a Sphere”

Understanding the molecular mechanism
of proton conduction is crucial
for the design of new materials with improved conductivity. Quasi-elastic
neutron scattering (QENS) has been used to probe the mechanism of
proton diffusion within a new phosphonate-based metal–organic
framework (MOF) material, MFM-500­(Ni). QENS suggests that the proton
conductivity (4.5 × 10–4 S/cm at 98% relative
humidity and 25 °C) of MFM-500­(Ni) is mediated by intrinsic “free
diffusion inside a sphere”, representing the first example
of such a mechanism observed in MOFs.