Synthesis of cross-linked copolymers of the (3-(2-pyridyl) acrylic acid)–copper(ii) complex in supercritical carbon dioxide for the catalytic oxidation of benzyl alcohol

Abstract

The copper(II) complexes of poly[(3-(2-pyridyl) acrylic acid)-co-acrylic acid] {P(Pya-co-AA)} were prepared via precipitation polymerization in supercritical carbon dioxide. The complexes were synthesized using a simple and efficient method of using N,N′-methylenebisacrylamide (BIS) as a cross-linker and scCO₂ as the reaction solvent. The obtained products were characterized by Fourier transform infrared (FTIR) spectroscopy, UV-Visible spectroscopy, X-ray diffraction and X-ray photoelectron spectra (XPS) analysis. The results indicate that the metal ion was coordinated via the nitrogen and oxygen of Pya. In the method, the properties of the complexes were controlled by operating parameters such as the pressure of scCO₂, the ratio of copper, and cross-linker concentration in scCO₂. The catalytic activity of the polymer–metal complexes was evaluated for the oxidation of benzyl alcohol using hydrogen peroxide. The results revealed the complexes exhibit high catalytic efficiency and can be reused repeatedly in high yield.