Polymers with multiple ligand sites for metal extractions in dense-phase carbon dioxide

We have synthesized a series of CO2-soluble polymeric extractants with mult iple ligand sites for CO2-based metal extractions. The CO2-soluble polymers were prepared via free-radical copolymerization of a fluorinated acrylate with a series of acrylate- or styrene-based monomers functionalized with li gand sites or ligand precursors. These polymers have high solubility in CO2 ; up to 30 wt % of a polymer with 15 mol % of a ligand-based monomer can be solubilized in liquid CO2 at 25 degreesC at 140 bar. Copper and europium e xtractions have been performed with beta -diketone- and phosphonate-functio nalized polymers, respectively. Preliminary extractions with copper nitrate were carried out at ligand-to-metal ratios of 1:1 and 2.7:1, resulting in 25-37% and 59% efficiency, respectively, suggesting a ligand binding stoich iometry of 2 for efficient extraction. Europium luminescence studies demons trate that. europium is bound to the polymer along with four water molecule s in the inner coordination sphere.