[en] This work concerns the synthesis of hybrid organic-inorganic materials for the selective sequestration of uranium, americium, plutonium and rare earths. Its aim is then new selective separation techniques Ln³⁺/An³⁺ and Am³⁺/Pu⁴⁺ as well as the discrimination of metallic oxo-anions UO₂²⁺ and PuO₂²⁺ towards the cations Ln³⁺ and An³⁺. In order to reach the waited selectivity, the ligands and molecular materials studied are prepared considering the speciation and the redox effects of these metals which depend strongly of the concentration and of the pH. In taking into account of the high coordination number of the actinides at the +III and +IV oxidation degree, the chelating agents chosen are podant ligands constituted of a tri-nitrogen 'head' of diethylene-amine type, linear tetra-nitrogen or macrocyclic (cyclam) on which are grafted several coordinating arms having a 'hard' or 'soft' character. The ultimate aim is to incorporate the most promising candidates into an inorganic matrix with the sol-gel process and to control the stereochemistry of the immobilized receptors in making the molecular impression of model complexes. (O.M.)