A Heart-Shaped Polyoxoniobate LiV₂Nb₃₀: Synthesis, Structure, and Chemiresistive Humidity Sensing

Trace humidity is a critical parameter in environmental monitoring and industrial production processes control, but traditional humidity sensing materials suffer from limited response humidity ranges and insufficient sensitivity. In this study, a novel polyoxoniobate (PONb), H₁₆K₈Li₃V₂Nb₃₀O₉₃·18H₂O (1), was successfully synthesized via a hydrothermal method by introducing vanadium into the niobium‑oxo cluster system. PONb 1 features a unique 33‑nuclear heart‑shaped cluster structure LiV₂Nb₃₀, which consists of a hollow V₂Nb₂₉ shell encapsulating a binuclear LiNb core, representing a new vanadium‑containing niobium-oxo clusters. Benefiting from its oxygen‑rich surface and the dense hydrogen‑bonding network formed between the cluster and lattice water molecules, PONb 1 exhibits sensitive chemiresistive humidity-sensing performance, achieving a high response for wide humidity ranges and a low detection limit of 176 ppm along with high cyclic stability, significantly surpassing most reported humidity‑sensing materials. This work not only enriches the structural diversity of PONb, but also provides new insights for the development of trace‑level chemiresistive humidity sensing.