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Supramolecular functional materials can be used to overcome some of the most challenging tasks in materials science, where the dynamic nature of supramolecular interactions can be leveraged to fine‐tune the properties of the material for a given task. The Lindqvist hexavanadate family of polyoxometalates (POMs) have emerged as particularly interesting candidates to be used in supramolecular materials due to their redox and Lewis acid properties that enable their application in the fields of energy conversion/storage or catalysis. Despite their promising potential, hexavanadate clusters are underrepresented in the field of supramolecular materials, mainly due to the synthetic challenges related to their inherent reactivity. In this work, pillar[5]arene was successfully grafted onto a Lindqvist hexavanadate and the resulting structure was confirmed by single crystal X‐ray diffraction (SC‐XRD), presenting the first example of a crystal structure of a POMcovalently functionalized with a pillar[5]arene. By introducing a ditopic guest molecule that could interlink pillar[5]arene moieties, host–guest interactions were leveraged as the driving force for the formation of supramolecular assemblies incorporating hexavanadate clusters in a controlled manner. The enhanced catalytic performance of the resulting aggregates confirmed their potential application as functional catalytic materials. This novel approach for developing hexavanadate‐based catalysts reported here showcases the potential of using host–guest interactions as a means to introduce catalytically active metal‐oxo clusters into supramolecular frameworks. [ABSTRACT FROM AUTHOR]

The artificial microenvironments inside coordination cages have gained significant attention for performing enzyme‐like catalytic reactions by facilitating the formation of labile and complex molecules through a "ship‐in‐a‐bottle" approach. Despite many fascinating examples, this approach remains scarcely explored in the context of synthesizing metallic clusters such as polyoxometalates (POMs). The development of innovative approaches to control and influence the speciation of POMs in aqueous solutions would greatly advance their applicability and could ultimately lead to the formation of elusive clusters that cannot be synthesized by using traditional methods. In this study, we employ host–guest stabilization within a coordination cage to enable a novel cavity‐directed synthesis of labile POMs in aqueous solutions under mild conditions. The elusive Lindqvist [M6O19]2− (M=Mo or W) POMs were successfully synthesized at room temperature via the condensation of molybdate or tungstate building blocks within the confined cavity of a robust and water‐soluble Pt6L4(NO3)12 coordination cage. Importantly, the encapsulation of these POMs enhances their stability in water, rendering them efficient catalysts for environmentally friendly and selective sulfoxidation reactions using H2O2 as a green oxidant in a pure aqueous medium. The approach developed in this paper offers a means to synthesize and stabilize the otherwise unstable metal‐oxo clusters in water, which can broaden the scope of their applications. [ABSTRACT FROM AUTHOR]