*Review* **Uranyl Ion Complexes of Polycarboxylates: Steps towards Isolated Photoactive Cavities**

**Jack Harrowfield 1,\* and Pierre Thuéry 2,\***


Received: 29 January 2020; Accepted: 18 February 2020; Published: 20 February 2020

**Abstract:** Consideration of the extensive family of known uranyl ion complexes of polycarboxylate ligands shows that there are quite numerous examples of crystalline solids containing capsular, closed oligomeric species with the potential for use as selective heterogeneous photo-oxidation catalysts. None of them have ye<sup>t</sup> been assessed for this purpose, and some have obvious deficiencies, although related framework species have been shown to have the necessary luminescence, porosity and, to some degree, selectivity. Aspects of ligand design and complex composition necessary for the synthesis of uranyl ion cages with appropriate luminescence and chemical properties for use in selective photo-oxidation catalysis have been analysed in relation to the characteristics of known capsules.

**Keywords:** uranium(VI); carboxylates; capsules; structure; luminescence
