Water-enabled palladium-free Sonogashira coupling over a pyridine-based COF hosting synergistic Ag/Cu nanoparticles

Abstract

The development of palladium-free catalytic green systems capable of promoting carbon–carbon cross-coupling reactions in environmentally benign media remains a significant challenge nowadays. Herein, a novel bimetallic nanocatalyst has been reported composed of synergistic Ag and Cu nanoparticles immobilized within a pyridinebased covalent organic framework (COF/AgCu NPs). The tailored COF scaffold, constructed from pyridine-2,6- dicarbaldehyde and p-phenylenediamine, provides well-defined high-porous channels and abundant nitrogen coordination sites, enabling the homogeneous nucleation, confinement and stabilization of Ag/Cu nanoparticles. The synthesized COF/AgCu nanocomposite exhibits outstanding potent catalytic activity toward the Sonogashira cross-coupling reaction in palladium-free conditions, using water as a eco-friendly and cheap solvent. Compared with monometallic COF-supported counterparts, the bimetallic system demonstrates a pronounced synergistic effect, delivering high product yields in low metal loadings and mild reaction conditions. A broad substrate scope (including aryl iodides, bromides, and even less reactive aryl chlorides) is efficiently accommodated without detectable alkyne homocoupling. Notably, the synthesized catalyst shows excellent structural robustness and recyclability, retaining up to 94% of its initial activity even after seven consecutive cycles. The enhanced performance is attributed to cooperative electronic interactions between Ag and Cu species and their strong coordination with the nitrogen-rich COF frameworks. This work highlights the potential of rationally designed COFsupported bimetallic nanocatalysts as sustainable and potent platforms for aqueous cross-coupling chemistry.