Palladium-Embedded Triptycene-Based Porous Organic Polymer: A Sustainable Catalyst for Suzuki-Miyaura Cross-Coupling Reactions

A knitted aryl network polymer (KAP) containing triptycene and triphenylphosphine was synthesized by a simple Friedel-Crafts reaction. The polymer (Tp_PPh3) exhibits good physicochemical stability with a high BET surface area (>960 m(2)/g). The triphenylphosphine groups were incorporated in order to anchor palladium species on the pristine KAP polymer backbone (Tp_PPh3). Consequently, metalation of Tp_PPh3 yielded Pd@Tp_PPh3, which showed catalytic behavior in the Suzuki-Miyaura cross-coupling reactions to yield targeted products in an aerobic environment, using water and ethanol as green solvents. This polymer-based heterogeneous catalyst is air/moisture stable and can be easily dispersed and reused for several cycles without any significant loss of catalytic activity. Even at low palladium loadings (13.8 wt %), Pd@Tp_PPh3 catalyzed rapid conversions. The catalyst is equally useful for gram-scale reactions. This strategy avoids aggregation and precipitation of Pd and simultaneously ensures a more sustainable use of the catalyst for Suzuki cross-coupling reactions. The application of Pd@Tp_PPh3 as a heterogeneous catalyst may be extended for other Pd-catalyzed reactions.