Effective capture of radioactiveiodine is of paramount importance for the safe and long-term storage of fission products in the nuclear fuel cycle. Herein, as eries of functionalized Th-UiO-66 MOFs wase mployed as a model to investigate the effects of substituents on iodine adsorption in both solution and vapor states. Sorption studies revealed that the electro-donating amino group exhibits the most positive role on increasing the removal rate of iodine from cyclohexane and the uptake capacity of iodine vapor.P articularly,t he disubstituted Th-UiO-66-(NH 2) 2 can effectively remove 91.9 %o fi odine (300 mg L À1) from cyclohexane and capture 969 mg g À1 iodine vapor, significantly highert han 59.6 %a nd 334 mg g À1 of untagged Th-UiO-66,r espectively.I na ddition, the substituent effect on the radiolytic stability of MOFs was for the first time investigated, leadingt ot he unearthing of one of the most radioresistant MOFs Th-UiO-66-NH 2 reportedt od ate.
With solvent molecules participating in coordination systems, four new Mn II coordination polymers of the rigid ligand 2,3,5,6-tetrachloro-1,4-benzenedicarboxylic acid (H 2 BDC-Cl 4 ) have been obtained from different solvent media. Singlecrystal X-ray analysis indicates that the coordination arrays of 1-4 vary from 1D fishbone or zigzag chain for 1 or 2, 2D (4,4) layer for 3, to 3D SrAl 2 coordination network for 4, respectively. In {[Mn(BDC-Cl 4 )(py) 2 (H 2 O) 2 ](py) 2 } n (1) and {[Mn(BDC-Cl 4 )(MeOH) 3 ](MeOH)} n (2), pyridine/water (in 1) and MeOH (in 2) molecules act as the monodentate terminal ligands to fulfill the metal coordination spheres. In the case of {[Mn(BDC-Cl 4 )(dioxane)(H 2 O) 2 ](dioxane)} n (3), the aqua ligand is monodentate and the dioxane moiety displays unusual bridging bidentate mode, whereas for [Mn 5 (BDC-Cl 4 ) 5 (DMF) 5 ] n (4), three Mn II centers are connected by four BDC-Cl 4 ligands and two DMF molecules to constitute a trimeric unit. These secondary units are extended to the final 3D network with SrAl 2 (sra) topology. Significantly, the solvents play an essential role in the crystallization and construction of these coordination frameworks with distinct dimensionality and connectivity. The thermal and photoluminescence properties of complexes 1-4 in the solid state have also been discussed.
Although metal−organic frameworks (MOFs) have been reported as important porous materials for the potential utility in metal ion separation, coordinating the functionality, structure, and component of MOFs remains a great challenge. Herein, a series of anionic rare earth MOFs (RE-MOFs) were synthesized via a solvothermal template reaction and for the first time explored for uranium(VI) capture from an acidic medium. The unusually high extraction capacity of UO 2 2+ (e.g., 538 mg U per g of Y-MOF) was achieved through ion-exchange with the concomitant release of Me 2 NH 2 + , during which the uranium(VI) extraction in the series of isostructural RE-MOFs was found to be highly sensitive to the ionic radii of the metal nodes. That is, the uranium(VI) adsorption capacities continuously increased as the ionic radii decreased. In-depth mechanism insight was obtained from molecular dynamics simulations, suggesting that both the accessible pore volume of the MOFs and hydrogen-bonding interactions contribute to the strong periodic tendency of uranium(VI) extraction.
The rational design and synthesis of metal−organic frameworks with wellcontrolled interpenetration have been active research areas of inquiry, particularly for porosityrelated applications. Herein, we extend the use of the ligand steric modulation strategy to initiate the first study of the interpenetration control of thorium-based MOFs. The approximate "hardness" of the Th 4+ cation, which was conjugated with aromatic substitutions and delicately modified synthetic conditions, allows for the crystallization of single crystals of seven new Th-MOFs with five distinct topologies. Solvothermal reactions of Th(NO 3 ) 4 with the triphenyl H 2 TPDC ligand under variable conditions exclusively gave rise to an interpenetrated Th-MOF with a hex topology, namely Th-SINAP-16. Modifications of the ligand sterics with two pendant methyl groups to 2′,5′-Me 2 TPDC 2− and 2,2″-Me 2 TPDC 2− afforded two noninterpenetrated UiO-68-type Th-MOFs (Th-SINAP-17 and Th-SINAP-20, respectively) with record-high pore volumes (74.8% and 75.3%, respectively) among all the thorium MOFs. Moreover, another four Th-MOFs Th-SINAP-n (n = 18, 19, 21, and 22) with three different topologies were obtained by a simple synthetic modulation. Notably, Th-SINAP-16 and Th-SINAP-21 represent the second rare examples of interpenetrated Th-MOFs reported to date. These findings revealed the unprecedented structural complexity and synthetic accessibility of Th-MOFs among all tetravalent metal containing MOFs. Such features make Th-MOFs as an ideal platform to elucidate the structure−property relationship for various applications, e.g. iodine adsorption.
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