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N-Formylation of Amines with CO2 and H2 Using Pd–Au Bimetallic Catalysts Supported on Polyaniline-Functionalized Carbon Nanotubes

Ju, Pengpeng, Chen, Jinzhu, Chen, Aibing, Chen, Limin, Yu, Yifeng
ACS sustainable chemistry 2017 v.5 no.3 pp. 2516-2528
X-ray diffraction, X-ray photoelectron spectroscopy, alloy nanoparticles, amines, carbon dioxide, carbon nanotubes, catalysts, catalytic activity, gold, hydrogen, hydrogenation, nitrogen, palladium, transmission electron microscopy
Bimetallic Pd–Au catalyst was prepared by depositing the Pd–Au alloy nanoparticles on polyaniline-functionalized carbon nanotubes (PANI-CNT) and the resulting Pd–Au/PANI-CNT catalyst exhibited excellent catalytic activity for the N-formylation of pyrrolidine using CO₂/H₂. The structural and electronic properties of the Pd–Au/PANI-CNT was characterized by X-ray powder diffraction (XRD), nitrogen adsorption–desorption, transmission electron microscopy (TEM), high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and X-ray photoelectron spectroscopy (XPS). Under optimized conditions, an N-formylpyrrolidine yield of 98.3% was obtained from pyrrolidine and CO₂/H₂ at 125 °C by using Pd–Au/PANI-CNT with a Pd/Au molar ratio of 1:1. Our research further reveals that Pd atoms should be the true active sites for the hydrogenation reaction and the N-formylation reaction might occur mainly over Pd atoms or over the interface between Pd atoms and Au atoms for the bimetallic Pd–Au/PANI-CNT catalyst. The enhanced catalytic performance of bimetallic Pd–Au/PANI-CNT is mainly related to beneficial interactions between Pd atoms and Au atoms, leading to changes of the electronic properties of the formed bimetallic Pd–Au nanoparticles.