Fine‐Tuning X‐Ray Sensitivity in Organic–Inorganic Hybrids via an Unprecedented Mixed‐Ligand Strategy

Abstract Crystalline organic–inorganic hybrids, which exhibit colorimetric responses to ionizing radiation, have recently been recognized as promising alternatives to conventional X‐ray dosimeters. However, X‐ray‐responsive organic–inorganic hybrids are scarce and the strategy to fine‐tune their detection sensitivity remains elusive. Herein, an unprecedented mixed‐ligand strategy is reported to modulate the X‐ray detection efficacy of organic–inorganic hybrids. Deliberately blending the stimuli‐responsive terpyridine carboxylate ligand (tpc−) and the auxiliary pba− group with different ratios gives rise to two OD thorium‐bearing clusters (Th‐102 and Th‐103) and a 1D coordination polymer (Th‐104). Notably, distinct X‐ray sensitivity is evident as a function of molar ratio of the tpc− ligand, following the trend of Th‐102 > Th‐103 > Th‐104. Moreover, Th‐102, which is exclusively built from the tpc− ligands with the highest degree of π–π interactions, exhibits the most sensitive radiochromic and fluorochromic responses toward X‐ray with the lowest detection limit of 1.5 mGy. The study anticipates that this mixed‐ligand strategy will be a versatile approach to tune the X‐ray sensing efficacy of organic–inorganic hybrids

A cationic thorium-organic framework with triple single-crystal-to-single-crystal transformation peculiarities for ultrasensitive anion recognition

Single-crystal-to-single-crystal transformation of metal-organic frameworks has been met with great interest, as it allows for the creation of new materials in a stepwise manner and direct visualization of structural transitions when subjected to external stimuli. However, it remains a peculiarity among numerous metal-organic frameworks, particularly for the ones constructed from tetravalent metal cations. Herein, we present a cationic thorium-organic framework displaying unprecedented triple single-crystal-to-single-crystal transformations in organic solvents, water, and NaIO3 solution. Notably, both the interpenetration conversion and topological change driven by the SC-SC transformation have remained elusive for thorium-organic frameworks. Moreover, the single-crystal-to-single-crystal transition in NaIO3 solution can efficiently and selectively turn the ligand-based emission off, leading to the lowest limit of detection (0.107 μg kg-1) of iodate, one of the primary species of long-lived fission product 129I in aqueous medium, among all luminescent sensors.Published versionThis work was supported by the National Natural Science Foundation of China (22076196, 21906163, and 21876182), the Young Taishan Scholars Program (tsqn201909082), Natural Science Foundation of Shandong Province (ZR201910290031), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA21000000), and the K. C.Wong Education Foundation (GJTD-2018-10)

Two-Dimensional Inorganic Cationic Network of Thorium Iodate Chloride with Unique Halogen–Halogen Bonds

A unique two-dimensional inorganic cationic network with the formula [Th₃O₂(IO₃)₅(OH)₂]Cl was synthesized hydrothermally. Its crystal structure can best be described as positively charged slabs built with hexanuclear thorium clusters connected by iodate trigonal pyramids. Additional chloride anions are present in the interlayer spaces but surprisingly are not exchangeable, as demonstrated by a series of CrO₄^2– uptake experiments. This is because all chloride anions are trapped by multiple strong halogen–halogen interactions with short Cl–I bond lengths ranging from 3.134 to 3.333 Å, forming a special Cl-centered trigonal-pyramidal polyhedron as a newly observed coordination mode for halogen bonds. Density functional theory calculations clarified that electrons transformed from central Cl atoms to I atoms, generating a halogen–halogen interaction energy with a value of about −8.3 kcal mol^–1 per Cl···I pair as well as providing a total value of −57.9 kcal mol^–1 among delocalized halogen–halogen bonds, which is a new record value reported for a single halogen atom. Additional hydrogen-bonding interaction is also present between Cl and OH, and the interaction energy is predicted to be −8.1 kcal mol^–1, confirming the strong total interaction to lock the interlayer Cl anions

Two-Dimensional Inorganic Cationic Network of Thorium Iodate Chloride with Unique Halogen–Halogen Bonds

A unique two-dimensional inorganic cationic network with the formula [Th₃O₂(IO₃)₅(OH)₂]Cl was synthesized hydrothermally. Its crystal structure can best be described as positively charged slabs built with hexanuclear thorium clusters connected by iodate trigonal pyramids. Additional chloride anions are present in the interlayer spaces but surprisingly are not exchangeable, as demonstrated by a series of CrO₄^2– uptake experiments. This is because all chloride anions are trapped by multiple strong halogen–halogen interactions with short Cl–I bond lengths ranging from 3.134 to 3.333 Å, forming a special Cl-centered trigonal-pyramidal polyhedron as a newly observed coordination mode for halogen bonds. Density functional theory calculations clarified that electrons transformed from central Cl atoms to I atoms, generating a halogen–halogen interaction energy with a value of about −8.3 kcal mol^–1 per Cl···I pair as well as providing a total value of −57.9 kcal mol^–1 among delocalized halogen–halogen bonds, which is a new record value reported for a single halogen atom. Additional hydrogen-bonding interaction is also present between Cl and OH, and the interaction energy is predicted to be −8.1 kcal mol^–1, confirming the strong total interaction to lock the interlayer Cl anions

Facile and Efficient Decontamination of Thorium from Rare Earths Based on Selective Selenite Crystallization

The coexistence of radioactive contaminants (e.g., thorium, uranium, and their daughters) in rare earth minerals introduces significant environmental, economic, and technological hurdles in modern rare earth production. Efficient, low cost, and green decontamination strategies are therefore desired to ameliorate this problem. We report here a single-step and quantitative decontamination strategy of thorium from rare earths based on a unique periodic trend in the formation of crystalline selenite compounds across the lanthanide series, where Ce­(III) is fully oxidized in situ to Ce­(IV). This gives rise to a crystallization system that is highly selective to trap tetravalent f-blocks while all other trivalent lanthanides completely remain in solution when coexist. These results are bolstered by first-principles calculations of lattice energies and an examination of bonding in these compounds. This system is contrasted with typical natural and synthetic systems, where trivalent and tetravalent f-block elements often cocrystallize. The separation factors after one round of crystallization were determined from binary systems of Th­(IV)/La­(III), Th­(IV)/Eu­(III), and Th­(IV)/Yb­(III) to reach 2.1 × 10⁵, 1.2 × 10⁵, and 9 × 10⁴, respectively. Selective crystallization of thorium from a simulated monazite composite yields a separation factor of 1.9 × 10³ with nearly quantitative removal of thorium