Loading Acid–Base Pairs into Periodic Mesoporous Organosilica for High Anhydrous Proton Conductivity over a Wide Operating Temperature Window

The design and fabrication of high proton conductors over a wide working temperature range are significant for the development of proton exchange membrane (PEM) fuel cells, as fuel cell vehicle technology requires solid electrolytes that should have the ability of conductivity at both high and subzero temperatures. Here, we demonstrated that biphenylene-bridged periodic-mesoporous-organosilica (PMO) and its sulfonated derivatives (s-PMO) are good hosts to load proton carrier imidazole for such sophisticated proton-conducting materials. With the acid–base pairs, the resulting material Im@s-PMO shows efficient proton conductivity over the temperature range from −40 °C (1.12 × 10–6 S/cm) to 180 °C (7.11 × 10–3 S/cm) under anhydrous conditions; the maximum value is significantly higher than that of Im@PMO (2.30 × 10–4 S/cm, 180 °C). The interaction between imidazole and the sulfonate group obviously affects the conductivity, which was confirmed by thermogravimetric analysis, MALDI-TOF mass spectrum, Fourier transform infrared spectroscopy, and 1H solid-state NMR. Our research shows a considerable advance based on periodic-mesoporous-organosilicas (PMOs) in the design of solid-state proton conductors that operate over a wide temperature range under anhydrous conditions.