Correlation of Structures with Proton Conductivity of 1D Coordination Polymers: Higher Proton Conductivity Due to Synergy of Encapsulated Sulfate Ions and Water Molecules

Coordination polymers (CPs) have received great attention as promising proton-conducting materials because of easy functionalization and structural tunability. However, studies of proton-conducting CPs illustrating the structure–property correlation are limited. The present study is focused on the synthesis of two one-dimensional CPs of copper(II) and cadmium(II) with NO3– and SO42– anions, respectively. The former with nitrate anions shows interdigitated 1D chains with channels of disordered water molecules, while the crystal packing of the other shows 1D zigzag polymers with a network of coordinated water molecules and sulfate ions that provides a synergic effect to enhance the proton transport property. We have delineated the structure–property relationship by analyzing the effects of these structural differences on their proton conductivity.