Pd(II)-Coordinated Porous Organic Polymer Anchoring Pd NPs: An Efficient Cooperative and Sustainable Catalyst for Suzuki-Miyaura Cross-coupling Reactions

Integrating homogeneous catalytically active components onto solid supports represents a primary strategy for the heterogenization of homogeneous catalysts. The purpose is to streamline catalyst separation and recovery processes while enhancing stability and reusability, all while retaining the inherent advantages of homogeneous catalysts. In this study, we synthesized immobilized Pd(II) complexes loaded with 3.5 nm palladium nanoparticles in a single step by incorporating imidazole precursors into porous organic polymer (POP) backbones through free radical polymerization. This process was conducted without resorting to complex synthetic conditions or toxic monomers, utilizing DMF as both solvent and reductant precursor. Pd NPs@POP-Pd was synthesized and thoroughly characterized by FT-IR, PXRD, ICP-OES, XPS, BET, TEM, EDX, and TGA studies. The Pd(0) and Pd(II) contained in the catalyst play a synergistic activating-stabilizing effect that enabled the Pd NPs@POP-Pd to exhibit excellent catalytic performance towards Suzuki reactions between phenylboronic acid and a wide range of aryl halides at an ultra-low Pd loading of 1.92 mmol%. Notably, this catalyst can be recycled 9 times in pure ethanol while maintaining efficient catalytic activity throughout its use.