A series of Zr-based UiO-n MOF materials (n=66, 67, 68) have been studied for iodine capture. Gaseous iodine adsorption was collected kinetically from a home-made set-up allowing the continuous measurement of iodine content trapped within UiO-n compounds, with organic functionalities (-H, -CH3 , -Cl, -Br, -(OH)2 , -NO2 , -NH2 , (-NH2 )2 , -CH2 NH2 ) by in-situ UV-Vis spectroscopy. This study emphasizes the role of the amino groups attached to the aromatic rings of the ligands connecting the {Zr6 O4 (OH)4 } brick. In particular, the preferential interaction of iodine with lone-pair groups, such as amino functions, has been experimentally observed and is also based on DFT calculations. Indeed, higher iodine contents were systematically measured for amino-functionalized UiO-66 or UiO-67, compared to the pristine material (up to 1211 mg/g for UiO-67-(NH2 )2 ). However, DFT calculations revealed the highest computed interaction energies for alkylamine groups (-CH2 NH2 ) in UiO-67 (-128.5 kJ/mol for the octahedral cavity), and pointed out the influence of this specific functionality compared with that of an aromatic amine. The encapsulation of iodine within the pore system of UiO-n materials and their amino-derivatives has been analyzed by UV-Vis and Raman spectroscopy. We showed that a systematic conversion of molecular iodine (I2 ) species into anionic I- ones, stabilized as I- ⋅⋅⋅I2 or I3 - complexes within the MOF cavities, occurs when I2 @UiO-n samples are left in ambient light.

In the present work, we aim to investigate the ability of the zirconium-based MOF-type compound UiO-66-NH2, to immobilize molecular gaseous iodine under conditions analogous to those encountered in an operating Filtered Containment Venting System (FCVS) line. Typically, the UiO-66-NH2 particles were exposed to 131I (beta and gamma emitters) and submitted to air/steam at 120 °C, under gamma irradiation (1.9 kGy h-1). In parallel to this experiment under simulated accidental conditions, the stability of the binderless UiO-66-NH2 granules under steam and gamma irradiation was investigated. In order to fit with the specifications required by typical venting systems, and to compare the efficiency of the selected MOF to porous materials commonly used by the industry, scale-up syntheses and UiO-66-NH2 millimetric-size shaping were realized. For this task, we developed an original binderless method, in order to analyze solely the efficiency of the UiO-66-NH2 material. The shaped MOF particles were then submitted separately to gamma irradiation, steam and temperature, for confirming their viability in a venting process. Their structural, textural and mechanical behaviors were characterized by the means several techniques including gas sorption, powder X-ray diffraction, infrared spectroscopy and crushing tests. Promising results were obtained to trap gaseous molecular iodine in severe accidental conditions.

Crystallized powder of dihydroxide zirconium oxalate Zr(OH)2(C2O4) (ZrOx) was obtained by precipitation and the structure determined from powder X-ray data. The three-dimensional (3D) framework observed in (ZrOx) results from the interconnection of zirconium hydroxide chains 1∞[Zr(OH)2]2+ and zirconium oxalate chains 1∞[{Zr(C2O4)}2+]. Single crystals of (H11O5)2[Zr2(C2O4)5(H2O)4] (H2Zr2O5) were obtained by evaporation. The structure contains dimeric anions [Zr2(C2O4)5(H2O)4]2– connected through hydrogen bonds to hydroxonium ions (H11O5)+ to create a 3D supramolecular framework. The addition of ammonium or alkali nitrate led to the formation of single crystals of Na2[Zr(C2O4)3]·2H2O (Na2ZrOx3), M(H7O3)[Zr(C2O4)3]·H2O, M = K (KHZrOx3), M = NH4 (NH4HZrOx3), M(H5O2)0.5(H9O4)0.5[Zr(C2O4)3], M = Rb (RbHZrOx3), and M = Cs (CsHZrOx3). For the five compounds, the structure contains ribbons 1∞[{ZrOx3}2–] formed by entities Zr(C2O4)4 sharing two oxalates. In (Na2ZrOx3), the shared oxalates are in cis positions and the chain 1∞[Zr–Ox] is stepped with a Zr–Zr–Zr angle of 98.27(1)°. In the other compounds, the shared oxalates are in trans positions and the chains 1∞[Zr–Ox] are corrugated with Zr–Zr–Zr angles in the range 140.34(1)–141.07(1)°. In the compounds (MHZrOx3), the cohesion between the ribbons is ensured by the alkaline or ammonium cations and the hydroxonium ions (H7O3)+ for M = K, NH4, (H5O2)+, and (H9O4)+ for M = Rb and Cs. During the thermal decomposition of the alkaline-free zirconium oxalates (ZrOx), (H2Zr2Ox5), and (NH4HZrOx3), the formed amorphous zirconia is accompanied by carbon; the oxidation of carbon at about 540 °C to carbon dioxide is concomitant with the crystallization of the stabilized tetragonal zirconia.

A family of compounds with general chemical formula Ln2[(UO2)2V2O8]3·nH2O, where Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Er, Yb, Y has been hydrothermally synthesized and structurally characterized. The structures of all these compounds can be described as the stacking of carnotite-type uranyl vanadate layers pillared by lanthanide–oxygen polyhedra. Except for La, they are isostructural, and the crystal structure determination of Nd2[(UO2)2V2O8]3·22H2O and Y2[(UO2)2V2O8]3·20H2O shows that the ud/du/du geometrical isomers of the uranyl vanadate layers are pillared by Nd(Oyl)2(H2O)7 and Y(Oyl)2(H2O)6 polyhedra, respectively, through interactions between the lanthanide ion and the oxygens Oyl of two vanadyl ions forming V═Oyl–Ln–Oyl═V entities. In the La compound, the ud/du geometrical isomers of the uranyl vanadate layers are pillared by La(Oyl)2(H2O)8, through interactions between the lanthanum ion and the oxygens Oyl of one vanadyl and one uranyl ion, forming U═Oyl–La–Oyl═V entities. Thermogravimetric and high-temperature X-ray diffraction studies show that the dehydration of the La compound is also singular; while the dehydration of other compounds involves a regular decrease in the interlayer space, for La it is realized through structural transitions. Upon partial dehydration, the La crystalline material undergoes a single-crystal to single-crystal transition between the 20- and 6-hydrates. Despite very large variation of the unit cell parameters and volume (ΔV = −27.8%!), the crystal remained of sufficient quality to allow the crystal structure determination of the hexahydrate. The total dehydration is reversible.

In order to rationalize the production of porous Metal-Organic Frameworks (MOFs) in ionic liquids (ILs) as main solvent, we selected the archetype UiO-66(Zr) to analyze its precipitation in four commercial candidates of Its commonly used in the literature. We did the choice to investigate the reactivity of two hydrophobic salts, 1-ethy1-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][NTf2]) and 1-butyl-3-methylimidazolium hexafluorophosphate [Bumim][PF6]), as well as two other salts considered as hydrophilic, ([Omim)[Cl]) and 1-ethy1-3- methylimidazolium trifluoromethanesulfonate ([Emim][TFO]). Whereas the synthesis in hydrophilic gave rise to the crystallization of pure UiO-66(Zr), the solvo-thermal reaction (120 degrees C) performed in hydrophobic salts did not lead to the same results. In the case of [Bumim][PF6], we noted the precipitation of zirconium phosphate Zr(HPO4)(2) H2O, while the synthesis in [Emim][NTf2] favored the formation of distinct zirconium terephthalate called hcp UiO-66. These different phases have been characterized by powder X-ray diffraction, BET, IR and SEM.

The synthesis, characterization and thermal decomposition of the uranyl peroxide nanocluster (NH 4 ) 40 [(UO 2 ) 32 (O 2 ) 40 (OH) 24 ].nH 2 O, designated as U32R-NH 4 , are presented for a series of temperatures ranging from 20 to 800°C.The handlings and annealing were carried out under air and the post-treatment characterizations were managed back to room temperature.The identification of the intermediate compounds was achieved by chemical analysis, infrared spectroscopy and powder X-ray diffraction.The proposed decomposition scheme up to U 3 O 8 comprises three main steps; (i) the low temperature range, from room temperature to 190°C, is characterized by the loss of the molecular species, water molecules, ammonium and peroxo ions, (ii) the intermediate temperature range, from 190 to 590°C, involves mostly structural rearrangements and release of oxygen and nitrogen species, and (iii) the high temperature range, above 590°C, which is associated to the UO 3 -U 3 O 8 transition accompanied with O 2 release.The thermal treatment up to 800°C does not alter the morphological features of the initial powder suggesting a pseudomorphic decomposition.Upon ageing or heating, the starting compound, (NH 4 ) 40 [(UO 2 ) 32 (O 2 ) 40 (OH) 24 ].nH 2 O, readily loses its crystallinity.