Efficient proton conductivity of a novel 3D open-framework vanadoborate with [V6B20] architectures

Abstract

A new three-dimensional (3-D) inorganic metal–oxygen network vanadoborate Na₃H₁₀[Ni(H₂O)₂(VO)₆(B₁₀O₂₂)₂]·NH₄·19H₂O (1) constructed from lantern-type {(VO)₆(B₁₀O₂₂)₂} clusters, NaO₆ polyhedra and NiO₆ octahedra, was successfully synthesized by a hydrothermal method. In the structure, the {V₆B₂₀} clusters are linked together through NiO₆ octahedral bridges, resulting in 1-D chains along the c-axis. The 1-D chains are further connected by NaO₆ polyhedra to give rise to a 3-D open-framework structure. Furthermore, lots of NH₄⁺ and H₂O molecules are accommodated in the void of the structure, and may interact with the [V₆B₂₀] system via N–H⋯O, O–H⋯O hydrogen bonds, constructing a complex hydrogen-bonding network system. Strikingly, compound 1 exhibited a high proton conductivity of 3.22 × 10⁻³ S cm⁻¹ at 50 °C under 100% RH with an activation energy of 1.66 eV.