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© 2021 American Chemical Society.We unveil the synthesis and initial application of a hybrid inorganic–organic architecture comprising two–dimensional, few nanometer–thick magnesium phyllo(organo)silicate nanosheets displaying an ordered array of covalently linked imidazolium functionalities. Accessible via a simple, one–pot ambient–temperature synthesis using a custom organosiloxane, these so–called polyionic nanoclays (PINCs) represent an emergent class of supported ionic liquid phase and hold a number of attractive features, including: (i) an extremely high ionic density (e.g., 3.8 mmol g–1 for the 1–methyl–3–propylimidazolium chloride PINC, roughly two–thirds the imidazolium cation density observed in the analogous free–flowing ionic liquid); (ii) the exchangeability of the associated counteranions to impart supplementary functionality or modulate solvent dispersibility; and (iii) the facility for tailoring the organic component, for example incorporating different (e.g., pyrrolidinium, pyridinium, phosphonium) or mixed onium moieties by employing the appropriate organosiloxane precursor(s). As a preliminary investigation of PINCs as nanocatalytic supports, we performed anion exchange with [AuCl4]–, followed by in situ reduction to generate small (<5 nm) gold nanoparticles (AuNPs) on the clay lamellae. The resulting nanosized gold–modified PINCs dispersed in water exhibited an astonishing turnover frequency of 25 000 h–1 for 4–nitrophenol reduction at room temperature, making this hybrid material the most active gold nanocatalyst reported for this model reaction. Most remarkably, AuNPs supported on the PINC showed a dramatically enhanced catalytic activity (4000% increase) compared to similar gold nanoparticles suspended in water (600 h–1), suggesting a major synergistic effect arising from the PINC support. Overall, the generality and flexibility of this route to lamellar hybrid nanoclays, coupled with the ability to accommodate a wide range of pendant organic ionic moieties suggests an auspicious future for PINCs in catalysis, ion exchange, energy storage, separations, (bio)sensing, imaging, and the construction of nanoscale assemblies.
