Microcapsules-supported Pd catalysts with ultralow ionic residues

Catalyst supports play an essential role in improving catalytic activity, preventing site loss, and promoting material diffusion . In this work, polyethyleneimine (PEI) microcapsules were prepared by interfacial crosslink polymerization on micro-droplets. The influence of reaction conditions on the formation of microcapsules was investigated in detail by combining the in-situ observation of optical microscope and kinetic modeling of interfacial polymerization. The obtained microcapsules can strongly absorb Pd 2+ with an adsorption capacity of up to 1000 mg/g. The microcapsules-supported Pd (Pd/MCs) presented good catalytic activity for the Suzuki coupling reaction. The apparent activation energy was 28.3 kJ/mol. In addition, the catalyst demonstrated good recycling characteristics. The leakage rate of the Pd ion was less than 0.016%, and the residual amount of Pd in the reaction solution was lower than 0.099 ppm. Moreover, after repeatedly being used 10 times, the conversion efficiency of bromobenzene was maintained above 94%.