G. Poisson (a), G. Canard (b), F. Fotiadu (a), J. Leclaire (a,c)
a) Laboratoire Chirosciences, CNRS, Aix Marseille Université, Centrale Marseille, iSm2 UMR 7313, avenue Escadrille Normandie-Niemen, 13397 Marseille Cedex 20, France.
b) Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France.
c) Equipe Chimie Supramoléculaire Appliquée (CSAp), Université Lyon 1 – CNRS 5246 ICBMS – Bâtiment CPE 43, bd du 11 novembre 1918-69622 Villeurbanne, Cedex, France
Corresponding author email: email@example.com
The global demand of rare earth elements (REEs) and other rarest metal is growing steadily due to their use in many high-tech and green technologies. In the near future, supply of REEs is likely to be disrupted if new sources of metal are not found quickly . Urban mining from technological waste containing REEs represents a potential solution to the supply, providing that innovative low-cost and green recycling methods can be developed.
The main issue in REE’s recycling resides in the chemical complexity of the waste products combined with a low content in target metals. Besides conventional static ligands that have been developed through decades for liquid-liquid extraction of REE, ammonium carbamates, spontaneous adducts between amines and CO2, are known to form stable complexes with lanthanides  and group (IIIA) metals . Their formation being reversible, a self-assembling capture process involving amines, CO2 and metals can be envisaged. The recent use of CO2 as organic tecton in dynamic combinatorial libraries has indeed offered the opportunity to generate in situ the functional groups devoted to metal binding . Thorough screenings of polyamine and polyaldehyde building blocks in the presence of CO2 generating multi-component dynamic combinatorial libraries have yielded hits which display some strong efficiency and selectivity in terms of metals incorporation.
These spontaneous capture experiments can repeatedly be carried out in mg scale with constant and unprecedented selectivities for the smallest metal cations of the series . Tuning finely the physical and chemical parameters of the assembling process provides reversible systems from which capture metals can simply be expelled through thermal CO2 release .
These multi-component reversible systems may ultimately pave the way toward kg scale recycling of metal from technological waste.
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 G. Poisson, J. Leclaire, F. Fotiadu, G. Canard, Brevet Français FR 13 54510
 G. Poisson, J. Leclaire, F. Fotiadu, G. Canard, PCT/FR2014/051172