Highly proton-conductive copper coordination polymer, H2dtoaCu (H2dtoa=dithiooxamide anion)

Room-temperature proton conductivity, coordination geometry, and pore-diameter distribution of the title Cu(II) coordination polymer have been investigated by AC conductivity, EXAFS, and N2 adsorption isotherm measurements. The AC proton conductivity (σp) obtained from Cole–Cole plot analysis under relative humidity of 75% and 300 K exhibits a considerable high value of 10−6 S cm−1 as a room-temperature σp. The mechanism of proton conduction seems to be similar to that of a proton-exchange membrane, Nafion, which contains much cluster of water molecules in the porous space of the polymer. The present Cu coordination polymer was revealed to possess porous space of about 6 Å, which includes much water molecules more than 10H2O per unit cell. The dimeric Cu(II) square-planar coordination geometry was confirmed by EXAFS analysis using synchrotron radiation source at SPring-8.