MOFs of Uranium and the Actinides

Abstract

Although the transition d- or 4f-block elements are the most used metals for the construction of metal–organic frameworks (MOFs), actinide cations were also involved in the elaboration of various hybrid organic–inorganic assemblies. The actinide elements with progressively filled 5f orbitals are a unique series, not only due to their radioactivity, but also because most of them have varied oxidation states. Uranium as the most important actinide element was exploited primarily to manufacture nuclear weapons due to its ability of nuclear fission. Besides its nuclear physics, the rich chemical state of this element also realizes rich chemistry and the formation of various compounds with other elements. Among the uranyl–organic frameworks (UOFs), uranyl UO2 2+ with the oxidation state of +6 for the metal is the most common structural unit, considering its reactivity with the different types of carboxylic acids. The construction of UOFs is always based on the coordination of organic ligands on the bipyramidal polyhedral structures of UO2 2+ species as primary building units. To date, multidimensional extended uranium-bearing coordination complexes have been studied, and an important library of UOFs have been developed and well defined. In this chapter, we describe efforts to synthesize MOFs of uranium and other actinides with desired structures. The basic building units and the strategies to construct different UOFs are addressed here, especially for the impact of organic ligands, structure-direct agent, and incorporation of heterometal ions. Although most of the actinide–organic frameworks are based on the uranium element due to its coordination advantages and long research history, increasing other actinide–organic frameworks with different organic ligands and structures have been developed. The typical MOFs of other actinides (actinide oxalates, actinide carboxylate, and actinide carboxyphosphonate) are also reviewed in this chapter. This work may contribute to the understanding of MOFs with actinide cations and provide a valuable reference for the development of novel MOFs materials with advanced functions.