Temperature-dependent transformation of decavanadate-type {V₁₀O₂₈}^6- clusters into {V₃O₇}^- layer structures mediated by 3-quinuclidinol as a structural templating agent: Crystal architectures and mechanism

In this study, two novel vanadate with different dimensions were prepared by hydrothermal synthesis using 3-quinuclidinol as the structural templating agent, namely, zero-dimensional decavanadate [(C₇H₁₄NO)₆(V₁₀O₂₈)]·2H₂O (1) and two-dimensional vanadate [C₇H₁₄NO][V₃O₇]·H₂O (2). At a low reaction temperature of 373 K, only crystal 1 is produced. As the reaction temperature is increased in the range of 393–473 K, {V₁₀O₂₈}^6- clusters can transform into {V₃O₇}^- layers and the ratio of the transformation gradually increases, resulting in the formation of crystal 2. To our knowledge, this is the first study to achieve a controllable transformation of the vanadium-oxygen anion structure with different dimensions solely through adjusting the reaction temperature, without changing the reactant type and feed ratio. The transformation mechanism also was investigated. The results show that the transformation is caused by the redox reaction between 3-quinuclidinol with {V₁₀O₂₈}^6- polyoxoanion. Moreover, 2 possesses a large layer spacing due to the large 3-quinuclidinol cations acting as the “pillar”, resulting in exhibiting good capacity performance (262.4 mAh g⁻¹ at 0.1 A g⁻¹) as the cathode material for aqueous zinc ion batteries. This study not only provides a viable approach for the temperature-tuned transformation of different dimensional vanadium-oxygen anion structures, but also proves that layered vanadate containing large cations are potential high-capacity cathode materials for AZIBs.