Ammonia as Proton Conducting Medium Confined in Porous Materials

<b></b><p>Molecular confinement within a limited space induces unique behaviour not seen in bulk systems. In particular, the proton diffusion in conducting medium under confined conditions is significantly affected by the surrounding environment.H<sub>2</sub>O, efficient conducting medium, confined in hydrophobic channels forms unique clusters allowing rapid diffusion, whereas confined NH<sub>3</sub>, having a similar degenerate system (Fig. 1a), has not been reported. Herein, we show NH<sub>3</sub>-mediated proton conduction in microporous metal–organic frameworks (MOFs), MIL-53(Al) functionalized with (-COOH)<sub>2</sub>, -NH<sub>2</sub>, -OH and -H. Anhydrous NH<sub>3 </sub>gas is trapped in the pore by proton donation of frameworks and forms hydrogen bonding networks exhibiting a remarkably enhanced proton conductivity. The crystallographic analysis and solid-state NMR clarify the veiled proton diffusion mechanism and unique dynamic behaviour of confined NH<sub>3</sub>.</p><br>