Proton conducting in a new vanadoborate with 3D structure through hydrogen bonding

Abstract A new vanadoborate [H3dien]2[V6B22O44(OH)10(H2O)0.5]·2H3O·12H2O (1, dien = diethylenetriamine) was synthesized under hydrothermal condition. One corner-shared hexa-nuclear {V6O18} ring was sandwiched by two raft-like {B11O19(OH)5} rings, giving rise to the [V6B22O44(OH)10(H2O)0.5]8- cluster. Besides, there are protonated H3dien3+, H3O+ cations balancing negative charge of the framework and some water molecules floating in the interclusters space. They are interacted with the V6B22 clusters through H-bonding networks and formed a three-dimensional (3D) structure. These structural features endow compound 1 a high proton conductivity of 1.3 × 10−3 S cm−1 at 55 °C under 100% humidity conditions, in addition, the activation energy of compound 1 is estimated to be 1.57 eV.