Unveiling the potential of Pd(II)‐covalent organic polyimide framework in Suzuki coupling reactions: A study on synthesis, characterization, and catalytic efficiency

Abstract

In this research, a highly effective heterogeneous Pd catalytic system was conceived by immobilizing Pd(II) onto a substrate composed of covalent organic polyimide frameworks (PI‐COF). The synthesized catalyst underwent comprehensive characterization using techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 adsorption analysis (Brunauer–Emmett–Teller [BET]), Fourier transform infrared (FT‐IR), thermogravimetric analysis (TGA), and inductively coupled plasma atomic emission spectroscopy (ICP‐AES). Subsequently, the catalytic activity of this immobilized Pd catalyst was explored in the context of the Suzuki reaction. The reactions at 70°C up to 1 h under a normal atmosphere in water result in biaryls at good to excellent yields (>90%). More importantly, the leaching of Pd(II) during the reaction process could be negligible (about 0.5 ppm), which is crucially important when preparing bioactive species. The loading of Pd(II) ions on the PI‐COF was 0.49 mmol/g. The catalyst exhibited exceptional performance, demonstrating remarkable efficacy in catalyzing a wide range of aryl halides (excluding aryl chlorides) when reacted with phenylboronic acid under environmentally friendly reaction conditions. Notably, the catalyst exhibited robust recyclability, retaining its catalytic activity throughout 5 reaction cycles without any significant decrease.