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The confinement-dependent properties of solvents, particularly water, within nanoporous spaces impart unique physical and chemical behavior compared to those of the bulk. This has previously been demonstrated for a U(VI)-based metal organic nanotube that displays ice-like arrays of water molecules within the 1-D pore space and complete selectivity to H

Water contained within nanoporous spaces exhibits different chemical and physical properties to those that are observed in the bulk phase, and these differences are exploited in the natural world to impart specific functionalities to biologic and geologic systems. The goal of rational design is to take this inspiration from nature and develop an understanding of structure–function relationships to create materials with similar or improved level of control. In this highlight, we explore the similarities between water confined within synthetic metal organic nanotubular materials and natural systems. We focus first on water structure and unique hydrogen bonding nets and then move to the observed differences in water behavior between nanoconfined and bulk systems. Last, we discuss specific design principles that should be explored to control the structure and properties of water under confinement within metal organic nanotubular materials.

Uranyl peroxide compounds are important to the nuclear fuel cycle and are typically formed from the direct addition of hydrogen peroxide or through photochemical pathways that utilize a sacrificial solvent. In this study, we explore the use of THF as a peroxide forming solvent that could be used to promote the crystallization of uranyl peroxide materials. Compound 1 (Li(H2O)2(UO2)(C7H3NO4)(C4H5NO4)·2H2O) was originally crystallized after aging for 10 days at room temperature and was characterized by X-ray diffraction, elemental analysis, Raman spectroscopy, and UV/vis spectroscopy. Exposure to ambient light for one month led to the complete transformation of 1 to compound 2 ((C5NH6)2[(UO2)2(μ-O2)(H2O)2(C7NO4H3)2]·4H2O). Oxidation of the THF molecule was proposed as the major mechanism for the formation of the secondary uranyl peroxide compound, which was accelerated in the presence of the UO22+ cation and light. Presence of THF hydrogen peroxide was confirmed by spectral (NMR and Raman) analysis of the mo...

Through a combination of many analytical approaches, we show that a metal organic nanotube (UMON) displays selectivity for H2O over all types of heavy water (D2O, HDO, HTO). Water adsorption experiments combined with vibrational and radiochemical analyses reveal significant differences in uptake and suggest that surface adsorption processes may be a key driver in water uptake for this material.

A series of three new actinide tetrahalide coordination compounds containing 2,2′-bipyridinium (H2bpy) have been synthesized by room temperature evaporation and characterized via single crystal X-ray diffraction, Raman spectroscopy, and infrared spectroscopy. The solid-state compounds (Np1, U1, and U2) contain the AnO22+ cation coordinated to four halide (chloride or bromide) atoms to form the anionic tetrahalide molecular unit [AnO2X4]2− (X = Cl, Br) and are charge balanced by the 2,2′-bipyridinium cations that engage in electrostatic interactions with the actinyl complex. Np1 (N2C10H10)[NpO2Cl4] contains 2,2′-bipyridine in the cis conformation where both the nitrogen atoms are directed towards the [NpO2Cl4]2− monomer. Within U1 (N2C10H9)[UO2Cl4], the 2,2′-bipyridine is in a trans conformation, and found in the same orientation in the isomorphous structure U2 (N2C10H9)[UO2Br4]. The compounds were further characterized by vibrational spectroscopy with specific interest in the actinyl cation. Raman spectroscopy provided information on the actinyl symmetric stretch (ν1) whereas IR spectroscopy is used to determine the location of the asymmetric stretch (ν3). Spectral similarities are observed between the two isomorphous structures, but slight variations across the series of structures are found to be associated with bipyridine bands in the various conformations. Additional analysis of these vibrational features in U1 and U2 provided information on the actinyl force constants, allowing insight into the relative uranyl bond strength that was compared to similar tetrahalide compounds.