Palladium Nanocrystals-embedded Covalent Organic Framework (Pd@COF) as Efficient Catalyst for Heck Cross-Coupling Reaction

Nanoparticles, such as noble metal nanoparticles and covalent organic frameworks (COFs), advance heterogeneous catalysis. Three COFs were synthesized via the solvothermal method using tricarboxylic acids (tricarboxylic benzene (2,4,6-tri-p-carboxyphenylpyridine (H3L2), 4,4',4''-tri carboxyl triphenylamine (H3L1), and trimesic acid (H3BTC)) and 1,3,5-Triazine-2,4,6-triamine moieties. The synthesized COFs were potentially used as supports for the in-situ growth of palladium nanocrystals (Pd NCs), offering a particle size of 1-5 nm. X-ray diffraction (XRD), Fourier transforms infrared (FT-IR), transmission electron microscopy (TEM), high-resolution TEM (HR-TEM), nitrogen adsorption-desorption isotherms, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) characterized the materials. Using Heck cross-coupling reaction, Pd NCs@COFs were used as catalysts to synthesize different organic molecules via carbon-carbon (C-C) formation. They exhibit complete conversion (100%) for vinyl derivatives and aryl halides (Bromo- and Chloro-derivatives) with good stability. Pd NCs@COFs maintain high catalytic activity over four consecutive cycles.