Anhydrous proton conduction at 150 °C in a crystalline metal-organic framework

Metal organic frameworks (MOFs) are particularly exciting materials that couple porosity, diversity and crystallinity. But although they have been investigated for a wide range of applications, MOF chemistry focuses almost exclusively on properties intrinsic to the empty frameworks; the use of guest molecules to control functions has been essentially unexamined. Here we report Na-3(2,4,6-trihydroxy-1,3,5-benzenetrisulfonate) (named beta-PCMOF2), a MOF that conducts protons in regular one-dimensional pores lined with sulfonate groups. Proton conduction in beta-PCMOF2 was modulated by the controlled loading of 1H-1,2,4-triazole (Tz) guests within the pores and reached 5x10(-4) S cm(-1) at 150 degrees C in anhydrous H-2, as confirmed by electrical measurements in H-2 and D-2, and by solid-state NMR spectroscopy. To confirm its potential as a gas separator membrane, the partially loaded MOF (beta-PCMOF2(Tz)(0.45)) was also incorporated into a H-2/air membrane electrode assembly. The resulting membrane proved to be gas tight, and gave an open circuit voltage of 1.18 V at 100 degrees C.