To acquire more new crystalline proton
conductive materials, three
ferrocene-based phenyl carboxylate frameworks (FCFs), [FcCO(o-C6H4COOH)] (FCF 1)
(Fc = (η5-C5H5)Fe(η5-C5H4)), [m-FcC6H4COOH] (FCF 2), and [p-FcC6H4COOH] (FCF 3), supported
by hydrogen bonds and π···π interactions
were prepared. Their structures and phase purities are clarified by
single-crystal X-ray diffraction or powder X-ray diffraction (PXRD).
In addition, their high thermal and water stability were confirmed
by thermogravimetric analyses, PXRD, and scanning electron microscopy
determinations. Proton conductivity (σ) of 1–3 was studied under different relative humidities (RHs) and
temperatures, and it was found that their σ boosted with the
increase of humidity and temperature. Under 100 °C and 98% RH,
their optimal σ values are 0.77 × 10–3, 1.94 × 10–4, and 3.46 × 10–3 S·cm–1, respectively. Consequently, their
proton conductive mechanisms were proposed by means of activation
energy calculation and structural analysis. Note that they are good
proton conductive materials and are expected to be used in proton
exchange membrane fuel cells.