POMzites: A Family of Zeolitic Polyoxometalate Frameworks from a Minimal Building Block Library

Abstract

We describe why the cyclic heteropolyanion [P8W48O184]40– (abbreviated as {P8W48}) is an ideal building block for the construction of intrinsically porous framework materials by classifying and analyzing >30 coordination polymers incorporating this polyoxometalate (POM) ligand. This analysis shows that the exocyclic coordination of first-row transition metals (TMs) to {P8W48} typically yields frameworks which extend through {W–O–TM–O–W} bridges in one, two, or three dimensions. However, despite the rich structural diversity of such compounds, the coordination of TMs to the {P8W48} ring is poorly understood, and therefore largely unpredictable, and had not until now been present with any structural classification that could allow rational design. Herein, not only do we present a new approach to understand and classify this new class of materials, we also present three {P8W48}-based frameworks which complement those frameworks which have previously been described. These new compounds help us postulate a new taxonomy of these materials. This is possible because the TM coordination sites of the {P8W48} ring are found, once fully mapped, to lead to well-defined classes of connectivity. Together, analysis provides insight into the nature of the building block connectivity within each framework, to facilitate comparisons between related structures, and to fundamentally unite this family of compounds. Hence we have tentatively named these compounds as “POMzites” to reflect the POM-based composition and zeolitic nature of each family member, although crucially, POMzites differ from zeolites in the modular manner of their preparation. As the synthesis of further POMzites is anticipated, the classification system and terminology introduced here will allow new compounds to be categorized and understood in the context of the established materials. A better understanding of TM coordination to the {P8W48} ring may allow the targeted synthesis of new frameworks rather than the reliance on serendipity apparent in current methods.

Beyond Charge Balance: Counter‐Cations in Polyoxometalate Chemistry

“…Kortz and co‐workers have explored the metal cation binding in the crown‐shaped [P 8 W 48 O 184 ] 40− (= {P 8 W 48 } ) and demonstrated that up to 20 Cu II ions as well as a wide range of other metal cations can be encapsulated at precise positions within the central pore (diameter ≈1 nm) of this species . The study laid the foundation for the use of {P 8 W 48 } as building block for porous frameworks: Cronin and co‐workers linked {P 8 W 48 } with metal cations (coordinated to external positions), producing a family of 3D porous frameworks with accessible pores suitable for cation uptake and release . These framework materials could conceptually bridge modular‐assembled frameworks such as metal–organic frameworks and inorganic porous materials such as zeolites.…”

“…[82] The study laid the foundation for the use of {P 8 W 48 } as building block for porous frameworks: Cronin and co-workers linked {P 8 W 48 } with metal cations (coordinated to external positions), producing a family of 3D porous frameworks with accessible pores suitable for cation uptake and release. [83,84] These framework materials could conceptually bridge modularassembled frameworks such as metal-organic frameworks and inorganic porous materials such as zeolites. The combination of inorganic metal-oxo building units and controllable structure assembly could lead to new reactivity and applications.…”

Jenseits von Ladungsausgleich: Gegenkationen in der Polyoxometallat‐Chemie

“…1 nm) gebunden werden können . Die Studie legte den Grundstein für die Verknüpfung von {P 8 W 48 } zu porösen Gerüsten: Cronin und Mitarbeiter verknüpften {P 8 W 48 } durch Metallkationen (koordiniert an peripheren Positionen) und erhielten eine Familie von porösen 3D‐Gerüsten mit zugänglichen Poren, die für Kationenaustausch nutzbar waren . Diese Gerüste können konzeptionell die Brücke zwischen modularen Gerüsten, wie Metall‐organischen Gerüsten, und anorganischen porösen Materialien, wie Zeolithen, bilden.…”

“…[77] Diese Gerüste mit offenen Poren zeigen eine grçßenselektive Aufnahme von kleinen Molekülen sowie Protonenleitfähigkeit und oxidationskatalytische Aktivität. [78] [83,84] Diese Gerüste kçnnen konzeptionell die Abbildung 3. Strukturdarstellung von Kation-POM-Gerüsten, beschrieben in den Abschnitten 2.2 und 2.3.…”

Controlling the Reactivity of the [P8W48O184]40− Inorganic Ring and Its Assembly into POMZite Inorganic Frameworks with Silver Ions

“…[4] Polyoxometalatebased framework materials,o rP OMzites,a re an emerging class of configurable all-inorganic porous materials. [5] Porous materials such as zeolites or metal-organic frameworks, MOFs,a re ordered networks whose building units are linked with strong interactions via ionic,c ovalent, and coordination bonds. [6] Silver ions are often used as af lexible linkers in coordination chemistry, [7] forinstance,silver-linked molybdenum oxide POMs are very stable,b oth in the solid and liquid phases.…”