Nanowire Networks of Metal-Organosilicates as Reversible Pd(II) Reservoirs for Suzuki Coupling Reactions

Formation of metallic palladium nanoclusters is an issue that hampers effective utilization of this precious metal in Suzuki-Miyaura and other cross-coupling reactions. In this regard, reversibility of shuttling between oxidative-state precatalysts and metallic-state acting catalysts is considered as a key for the design of Pd-based nanocatalysts. Herein, three-dimensional (3D) copper-organosilicate (Cu-OS) nanowire networks derived from 3-aminopropyl trimethoxysilane precursors have been demonstrated as an effective, reversible Pd(II) reservoir for Suzuki coupling reactions. In particular, the Pd ion-exchanged 3D nanowire networks exhibit excellent reactivity, stability, and recyclability, with no detectable formation of palladium nanoclusters and no perceptible loss of catalytic activity throughout 10 reaction cycles. A reversible Pd(II)-Pd(0)-Pd(II) shuttling between the solid-phase reservoir and liquid-phase coupling reaction was recognized through our extensive mechanistic investigations and material characterizations. High-throughput studies suggest that besides the decent recyclability, outstanding catalytic performance was due to the structural and compositional merits of the 3D nanowire networks. The scale of the overall macroscopic framework is in the micrometer range, which facilitates facile catalyst recovery. Meanwhile, the nanometer-scale 1D constituents offer high openness and accessibility for effective Pd shuttling. Chemically, the relatively weak alkylamine ligands circumvent the over-coordination issue commonly encountered by strong ligands and effectively prevent the formation of Pd nanoclusters. Compared with a number of state-of-the-art Pd-based catalysts, our 3D nanowire networks manifest excellent performance and recyclability simultaneously.

Automated summary

The formation of metallic palladium nanoclusters hinders their effective utilization in Suzuki-Miyaura and other cross-coupling reactions. Reversibility of shuttling between oxidative-state precatalysts and metallic-state acting catalysts is crucial in designing Pd-based nanocatalysts. 3D copper-organosilicate nanowire networks derived from 3-aminopropyl trimethoxysilane precursors have been proven effective as a reversible Pd(II) reservoir for Suzuki coupling reactions, showing excellent reactivity, stability, and recyclability.