Synthesis of polymer–copper(II) complexes in supercritical carbon dioxide

A polymer–metal complex containing poly(4-vinylpyridine) (4-VP) and copper(II) ions was investigated along with the catalytic properties of its products. The water-insoluble polymer–copper(II) complex was synthesized in supercritical carbon dioxide by using methanol as a cosolvent and N,N′-methylenebisacrylamide as a cross-linker. Fourier transform infrared spectroscopy and X-ray diffraction results reveal that the metal ion is coordinated via the nitrogen of 4-VP. The morphology and size of the products were characterized by scanning electron microscopy and ZetaSizer nano analysis. The results show that the spheres were about 200 nm in diameter when the pressure was 18 MPa. The maximum surface area (49.38 m2/g) was obtained via standard nitrogen adsorption analysis by using 3 mL of methanol. The polymer–copper(II) complex catalyst was used for the catalytic oxidation of phenol at room temperature and at atmospheric pressure by using H2O2 as an oxidant. As a result, an efficient catalytic performance was achieved, wherein the maximum phenol conversion was 78.3%. The current work presents a novel and simple method to prepare polymer–metal complexes.

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► A polymer–metal complex was synthesized through a clean route of stabilizer-free polymerization in supercritical carbon dioxide (scCO2).
► The polymer–copper(II) complex was synthesized in scCO2 holds more surface areas (49.38 m2/g) and higher yields (86.2%).
► The polymer–copper(II) showed a perfect catalysis effect for oxidation reaction of phenol. The conversion of the phenol was 78.3%.