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Heterogeneous Catalysis by Covalent Organic Frameworks (COF): Pd(OAc)<inf>2</inf>@COF-300 in Cross-Coupling Reactions

Abstract:

COF-300, an imine-linked, crystalline, and microporous covalent organic framework, modified by coordination of Pd(OAc)2 to its walls, afforded a hybrid material, Pd(OAc)2@COF-300, which was used as an efficient heterogeneous catalyst for cross-coupling reactions. This material showed excellent catalytic activity for the phosphine-free Suzuki-Miyaura, Heck, and Sonogashira cross-coupling reactions with low palladium loadings (0.1mol % Pd). X-ray photoelectron spectroscopy analysis of the catalyst after the reaction showed that PdII is converted to Pd0, which is trapped within the COFs nanopores. This was confirmed by high-resolution transmission electron microscopy. Moreover, promising results were obtained using Pd(OAc)2@COF-300 under continuous-flow conditions for a Suzuki-Miyaura cross-coupling reaction.