High proton conductivity in metalloring-cluster based metal-organic nanotubes

Two novel anionic single-walled metal-organic nanotubes (MONTs), [(CH 3 ) 2 NH 2 ][In(cdc)(thb)]•2DMF•9.5H 2 O ( FJU-105 ) and [(CH 3 ) 2 NH 2 ][In(cdc)(H-btc)]•2DMA•11H 2 O ( FJU-106 ) (H 2 cdc = 9H-carbazole-3,6-dicarboxylic acid, H 2 thb = 2,5-thiophene dicarboxylic acid, H 3 btc = 1,3,5-benzene tricarboxylic acid), are achieved by employing [In 6 (cdc) 6 ] 6+ metalloring cluster with largest diameter as the secondary building blocks (SBUs). The inner surface of FJU-106 is functionalized by uncoordinated -COOH groups of the H-btc linkers, leading to a higher proton conduction than FJU-105 . At 70 °C, FJU-106 displays the proton conduction performances among MONTs, up to 1.80 × 10- 2 S•cm -1 . And FJU-105 and FJU-106 are the first examples of MONT proton conductors operating at subzero temperature.