Construction of a unique 2-D layered vanadoborate with water-assisted proton conductivity†
Abstract
In the present work, a new two-dimensional layered vanadoborate Na4[V12B18O54(OH)6(H2O)]·(H2en)4·2(OH)·3H2O (1, en = ethylenediamine), based on a [V12B18O54(OH)6(H2O)]10− cluster unit, was hydrothermally obtained and characterized. In the structure, the [V12B18O54(OH)6(H2O)]10− clusters are linked by Na+ ions into the 2-D layers, which are further connected by water molecules or amine counterions to form 3-D vanadoborate architectures. The guest ions/molecules (i.e., Na+, H2en2+, and water) existing in 1 not only act as proton carriers, but also interact with the anions to form a continuous hydrogen-bonding network, thus providing a pathway for proton transport. The abovementioned characteristics make compound 1 an attractive candidate for a proton-conducting material. Complex impedance measurements on crystalline samples gave a proton conductivity of 2.55 × 10−4 S cm−1 at 333 K and 100% RH, indicating that the compound has a good prospect as a highly efficient proton conductor.