Dependency of extraction behavior of inert platinum group metals (PGMs) like Ru­(III) and Rh­(III) on temperature has been investigated in a biphasic system consisting of HNO3(aq) and betainium bis­(trifluoromethylsulfonyl)­amide ([Hbet]­[Tf2N]) ionic liquid. The extraction reactions of Ru­(III) and Rh­(III) took 3.5 days and 113 days, respectively, at 298 K, while equilibrated within 1 and 3 h to reach 99.2% and 96.5% extraction at 353 K. Further mechanistic studies clarified that the complexation of these PGMs and [Hbet]+ is rate-determining in their extraction and that it is successfully accelerated and enhanced by elevating the temperature.

Double-headed 2-pyrrolidone derivatives (DHNRPs) were designed and synthesized as bridging ligands for the efficient and selective separation of UO from a HNO solution by precipitation. The building blocks, UO(NO) and DHNRPs, were successfully connected to form an infinite 1D coordination polymer. The solubility of [UO(NO)(DHNRP)] is no longer correlated to the hydrophobicity of the ligand but is exclusively governed by the ligand symmetry and packing efficiency. The newly designed DHNRP family can be used to establish a new spent nuclear fuel reprocessing scheme.

Hexanitratouranate(IV), [U(NO3)6]2−, has been crystallized with anhydrous H+‐involving hydrogen bond polymers connected by selected diamide building blocks. Thanks to the significant moderation of electrostatic interactions between the anions and cations, the molecular structure of [U(NO3)6]2− in these compounds is regularly Th‐symmetric. The f–f transitions stemming from 5f2 configuration of U4+ are strictly forbidden by the Laporte selection rule in such a centrosymmetric system, so that the obtained compounds are nearly colourless in contrast to other UIV species usually coloured in green.

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Centrosymmetric hexanitratoneptunate(iv) crystallizes with anhydrous proton countercations trapped in a hydrogen bonded polymer with diamide linker molecules to give colourless crystals.