Rationally tuning host-guest interactions to free hydroxide ions within intertrimerically cuprophilic metal-organic frameworks for high OH- conductivity

Hydroxide-anion-exchange membrane fuel cells (HEMFCs) are now considered as one of the most promising green energy-conversion technologies for stationary and mobile applications, showing high fuel conversion efficiency at high pH and low cost due to their ability to operate under basic conditions using non-precious metal catalysts. But one key impediment to commercialization is insufficient hydroxide ion (OH-) conductivity of the central HEM component. Here, we report the development of free OH- anion-containing metal-organic frameworks (FOMOFs) with rationally tunable host-guest interactions for HEMs with high OH- conductivity. Among three solids obtained by post-synthesis treatment of ultrastable MOF FJU-66 with various bases, free OH- anions are observed in FJU-66$ [EVIm] OH with strong host-guest interactions between the MOF backbone and guest cations. Despite the lowest OH- concentration, FJU-66$[EVIm] OH exhibits the highest OH- conductivity close to 0.1 S cm(-1). The high OH- conductivity achieved suggests the potential application of the FOMOFs for practical HEMs of fuel cells.