Emerging Functionalized Lindqvist-Type Polyoxometalate-Based Compounds: Design, Synthesis, and Applications

This concept article highlights emerging potential of Lindqvist-type polyoxometalate (POM)-based compounds, focusing on their design, synthesis, and applications in catalysis, energy, and environmental fields. POMs are anionic metal-oxo clusters, broadly classified into isopolyoxometalates and heteropolyoxometalates. This article highlights Lindqvist-type POMs [M₆O₁₉]ⁿ⁻, a subset of isopolyoxometalates characterized by compact, highly symmetric octahedral structures, high negative charge densities, and multielectron transfer properties. These unique features have inspired studies on their organic modifications, utilizing the high reactivity of their surface oxygen atoms. It is now timely to revisit functionalized Lindqvist-type POM-based compounds, in both solution and solid states, particularly as catalysts. Recent advancements include stabilizing Lindqvist clusters through host–guest complexes enabling their use in aqueous environments. In the solid state, they have been utilized as structural units in inorganic–organic hybrid materials, demonstrating remarkable functionality. The promising potential of Lindqvist-type POM-based compounds encourages further research to establish systematic synthetic methods, moving beyond empirical approaches or serendipity, to address challenges in sustainability and energy production.