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Ion-absorbed rare earth ores radioactive residues (IREORR) are a class of waste residue from the production of rare earth elements (REEs). Because of its radioactive dose, IREORR are usually stored in waste warehouses. IREORR are difficult to be disposed of. However, it contains relatively high concentrations of REEs, which can be considered as a valuable secondary resource. In this paper, a novel process is developed for the separation of thorium (Th) and recovery of REEs from IREORR hydrochloric acid leachate with primary amine N1923 and Cyanex® 572, respectively. The effects of sulfate concentration, extractant concentration and pH on N1923 extraction in hydrochloric acid solution were investigated in detail. The results show that the extraction capacity of N1923 can be improved by adding sulfate to the solution and increasing the concentration of N1923. Acidity has little effect on the extraction of Th when pH is higher than 1. As for the stripping, REEs are more easily stripped from loaded organic phase than Th, and nitric acid is a better stripping agent than hydrochloric acid. Combined with the extraction of Cyanex® 572 for REEs, a fractional extraction experiment for separating Th and enriching of REEs was performed. The yield of Th is higher than 99.9% and the concentration of REEs is enriched to 183.84 g/L.

In this paper, a series of high performance near-infrared reflective pigments based on Bi3YO6 doped with Fe2O3 and Tb4O7 were prepared by high-temperature calcination method. The pigments were characterized by some analytic techniques, such as XRD, Particle size analyzer, SEM, EDS, UV–vis–NIR spectrophotometer, CIE L*a*b* (1976) color space and infrared thermal imaging. Experimental results showed that the Fe2O3 doping in Bi3YO6 could change the color from bright yellow to ochre red. The substitution of Tb (IV)-doped pigments changed the color to dark orange. The doping of Fe (III) and Tb (IV) contributed to enriching the color diversities of pigments. Among the synthesized pigments, Bi3-xFexYO6 and Bi3Y1-xTbxO6+δ displayed a disordered defective fluorite-type structure. The effect of doping Fe (III) and Tb (IV) reduced the near-infrared reflectance of the pigment. Excepting for Bi3-xFexYO6 (x = 0.8), the near infrared reflectance of some other pigments were higher than the China National standard (CNs). Chemical resistance tests showed that the pigments had excellent acid and alkali resistance. Finally, the application practical of traditional iron oxide yellow pigment and three prepared pigments, i.e., Bi3YO6, Bi3-xFexYO6 (x = 0.4) and Bi3Y1-xTbxO6+δ (x = 0.05) were studied and compared by infrared thermal imaging. The test results showed that Bi3YO6 still had a strong near-infrared reflection effect after being painted. Compared with traditional iron yellow pigment, Bi3YO6 could reduce the surface temperature of galvanized sheet by 20 °C under the illumination of infrared light. The series of Fe (III) and Tb (IV) doped pigments prepared in this paper have revealed some promising application values.

Herein we report a new 4-fold interpenetrated metal–organic framework (MOF) functionalized with O− groups for selective Th(IV) capture, the activated samples 1a exhibited a high adsorption capacity for pure Th(IV) ions (Kd = 3.16 × 105 mL g−1) and the amount of metal ions adsorbed on the adsorbent was 165.61 mg g−1. A high removal efficiency of 99.75% was achieved within 10 min with an initial Th(IV) concentration of 100 mg L−1 and the adsorption data followed the pseudo-second-order model. In addition, the separation coefficient (S) of Th(IV) to metal ions with different valence states such as Th(IV)/La(III), Th(IV)/Sm(III), Th(IV)/Ho(III), Th(IV)/Cd(II) and Th(IV)/K(I) achieved values of 19.66, 26.83, 16.90, 11.26 and 255.79, respectively. Even given the fact that MOFs with O− groups showed high affinity for Pb(II) ions, our adsorption studies for compound 1a revealed a separation coefficient (STh(IV)/Pb(II)) of 4.36. Further, the adsorption of Th(IV) ions to compound 1a was investigated by FT-IR, SEM-EDS and XPS.

Herein we report a new 4-fold interpenetrated metal-organic framework (MOF) functionalized with O

To achieve improved properties such as lower biotoxicity and better biocatalytic performances, the preparation of low oxidation state (+3) vanadium (V)-organic framework compounds (VIII-OFCs) is an important research area. Additionally, the incorporation of VIII-OFCs into a polyoxometalate (POM) is challenging due to the high standard reduction potential of VIII ions and the POM's innate sensitivity to oxidation. A new targeted and redox-based synthetic strategy has been devised to generate a V(III)-oxyanion by reducing a precursor in a pH-value controlled redox step. The V(III)-oxyanion is designed to coordinate with organic ligands for further forming an intermediate in which the metal node V(III) connects both organic units and oxygen-atoms. By employing a suitable stepwise synthesis strategy, we successfully obtained an unprecedented Keggin-type tungstovanadophosphate, (H3DETA)3(DETA){Na{[VIII(DETA)]2[WVI8VIV4O36(PO4)]}2}·2H2O (abbreviated as VIII-POWV) (DETA = diethylenetriamine, C4H13N3), bi-capped by VIII-OFCs. Its structure has been further characterized by means of powder-XRD, EDS, elemental analysis, FT-IR, XPS, thermal analysis, and SQUID magnetic measurements, etc. The seven-coordination mode (VO4N3) of VIII in VIII-POWV is uncommon and interesting. The novel structural compound, which contains mixed-valence vanadium (VIII/VIV), has better thermostability than most of the common organic POMs and shows the expected paramagnetic properties, accompanying antiferromagnetic exchange interactions under higher temperatures.

An uncoordinated salen-containing metal-organic framework (MOF) obtained through postsynthesis removal of Mn(III) ions from a metallosalen-containing MOF material has been used for selective separation of Th(IV) ion from Ln(III) ions in methanol solutions for the first time. This material exhibited an adsorption capacity of 46.345 mg of Th/g. The separation factors (β) of Th(IV)/La(III), Th(IV)/Eu(III), and Th(IV)/Lu(III) were 10.7, 16.4, and 10.3, respectively.

In this article, a new family of rare earth (RE) complexes with formula of [RE2(EPOA)6(H2O)3]·H2O, where RE = La, Nd, Er, Y and the HEPOA = 4-ethyl phenoxyacetic acid was synthesized. Their structures were characterized by single-crystal X-ray diffraction, FT-IR, and elemental analysis. The four complexes are isostructural and consist of two-dimensional networks. The decrease in Ln–O bond lengths reflects the lanthanide contraction. The structures of HEPOA ligand, the resulting dimer formed by hydrogen bond and their hydrogen binding energy were studied by density functional theory (DFT). In addition, atoms in molecules (AIMs) analysis revealed the presence of partial closed shell interactions between REs and oxygen atoms of HEPOA ligand in the four complexes. The values of bond degree (BD) have been calculated to evaluate the strength of interactions, suggesting that HEPOA ligand interacts more strongly with La and Nd than Er and Y. Investigations of the complexation of REs with phenoxyacetic acid-relate...

Thorium (Th) is a promising element that can be converted to fissile uranium for nuclear energy. A large amount of slag containing Th need to be effectively treated and stacked in rare earth (RE) industry. It is of importance to develop some novel processes for separating Th from REs using solvent extraction. The amide group was considered to have good selectivity for Th separation from REs. In order to solve the problem of RE entrainment during Th separation together with primary amine (N1923, (CnH2n+1)2CHNH2 n = 9–11) does not extract Th in hydrochloric acid system, three oxamic acid type extractants have been designed and synthesized in this paper. Among the extractants, the separation performance of 2-(dibenzylamino)-2-oxoacetic acid (DBOA) was indicated to be the best. As for the effective separation, the electron affinity of Th was larger, it was more preferred to coordinate with the extractant. The hydrogen ions released by the extractant could inhibit the extraction of REs rather than Th. Accordingly, Th could be separated from REs. Saponification process of oxamic acid extractant could be omitted in this separation process. By extracting Th using a lower concentration of oxamic acid selectively, not only the loss of RE could be reduced, but also a higher purity of Th could be obtained. Using a simplified fractional extraction experiment, the purity of RE in aqueous phase was increased to be 99.92% or higher, and the purity of obtained Th after stripping from loaded organic phase was increased to be 99.5%.

An amine-containing non-interpenetrating pillar-layer framework, [Zn

Two new metal–organic frameworks (MOFs) with novel architectures, namely, [Co2(NDC)2(H2MDP)2][(Co(NDC)(H2MDP)] (1) and [Co(NDC)(H2MDP)0.5] (2) were synthesized through a one-pot reaction. The metal to ligand ratio was found to influence the formation of the two compounds, and their pure phases were successfully obtained only by adjusting the molar ratios of Co/H2NDC/H2MDP to be 1:1:1 and 2:2:1, respectively [H2NDC = 1,4-naphthalenedicarboxylic acid, H2MDP = methylenebis(3,5-dimethylpyrazole)]. X-ray crystallographic analyses showed that 1 crystallizes as a racemic twin and features an interesting threefold 3D/3D hetero-interpenetrating diamondoid framework with left-handed and right-handed helical chains, whereas 2 displays a 3D twofold homo-interpenetrating pcu network constructed from paddle-wheel secondary building units and H2MDP pillars in a trans conformation. The one-pot synthesis of two or more MOFs with hetero-interpenetration and homo-interpenetration has been rarely reported.

Two μ₂-tetrazolyl bridged metal complexes, ([CdI(PTZ)(H₂O)]·H₂O)ₙ1 and ([Cu(PTZ)₂]·H₂O)ₙ2 (HPTZ=5-(pyrazinyl) tetrazolate), were hydrothermally synthesized and fully characterized by X-ray crystallography, elemental analyses and spectrum techniques. In 1, cadmium ions are bridged by tridentate μ₂-κ²N2,N5:κ¹N1 chelating PTZ⁻ ligand and halide linkers into an infinite 1D chain, while in 2 copper ions are connected by tridentate μ₂-κ²N7,N12:κ¹N8 and bidentate μ₂-κ¹N1:κ¹N2 chelating-bridging PTZ⁻ ligands to form a 1D castellated chain structure. Compound 1 displays phosphorescence with a lifetime of ~7.74 ms in the visible region, and the origin of the luminescent emission is primary assigned to the combination of ligand-centered emission, metal-to-ligand charge transfer and ligand-to-ligand charge transfer, which has been probed by the density of states (DOS) calculations. Magnetic measurement reveals that compound 2 displays an anti-ferromagnetic ordering. - Graphical abstract: Two new complexes based on 5-(pyrazinyl) tertrazolate, namely ([CdI(PTZ)(H2O)]·H2O)n and ([Cu(PTZ)2]·H2O)n have been synthesized and characterized. Compound 1 exhibits interesting green luminescence. Compound 2 displays an anti-ferromagnetic ordering. Highlights: • We report two novel 1D μ₂-tetrazolyl bridged Cd(II) and Cu(II) compounds. • The cadmium(II) compound exhibits a green luminescence. • Theoretical calculations were conducted to elucidate the green luminescence. • The Cu(II) compound exhibits an anti-ferromagnetic ordering.

A novel tetranuclear cadmium complex {Cd2[(CH3)2PPDA]2(CH3OH)Cl4}2 (1) [(CH3)2PPDA = dimethyl esterification of H2PPDA], was prepared from CdCl2·2.5H2O with (2,3-f)-pyrazino(1,10)phenanthroline-2,3-dicarboxylic acid (H2PPDA) by solvothermal reaction in methanol, and characterized by single-crystal X-ray diffraction analysis, optical diffuse reflectance and photoluminescence. In 1, cadmium ions are bridged by Cl− ions into a tetranuclear oligomeric chain further connected into a 3D supramolecular network by intermolecular C H⋯Cl, O H⋯Cl, and C H⋯O hydrogen bonds. Compound 1 displays fluorescence with a lifetime value of ~ 5.88 ns in the visible region under visible-light excitation, and the origin of the luminescent emission is primary assigned to the combination of intraligand π–π* transition of (CH3)2PPDA ligand and ligand to ligand charge transfer from Cl− to (CH3)2PPDA which is probed by the density of state (DOS) calculations.

A novel inorganic–organic hybrid compound [Cu(Mo2O7)(H2MDP)] (1) has been hydrothermally synthesized from the self-assembly of CuI, H2MoO4 and H2MDP ([Methylenebis(3,5-dimethylpyrazole)]). Compound 1 is constructed from one-dimensional {Cu(Mo2O7)}n bimetallic oxide chains bridged by H2MDP ligands into a novel two-dimensional hybrid compound. There exist left- and right-handed Cu O Mo helical chains in the bimetallic oxide chains.

Using a flexible methylenebis(3,5-dimethylpyrazole) ligand (H2MDP) with different aromatic carboxylate ligands, six new complexes {[Cd(H2MDP)(OPh)](H2O)}n (1), {[Cd(H2MDP)(MPh)](H2O)(1/10)}n (2), {[Cd(H2MDP)(PPh)](H2O)(3/2)}n (3), {[Co(H2MDP)(OPh)](H2O)2}n (4), {Co(H2MDP)(MPh)}n (5), {Co(H2MDP)(HBTC)}n (6) (H2OPh = phthalic acid, H2MPh = isophthalic acid, H2PPh = terephthalic acid, H3BTC = benzene-1,3,5-tricarboxylic acid) have been isolated under hydrothermal conditions. The crystal structure analyses reveal that complexes 1 and 4 feature two-dimensional undulated sheets with 4(4)·6(2) topology. Both complexes 2 and 3 contain M2L2-type metallocyclic motifs composed of two H2MDP ligands and two metal atoms, while complex 2 features a two-dimensional 4(4)·6(2) network constructed from binuclear cadmium units as four connected nodes, and complex 3 shows a two-dimensional network with 6(3)-hcb topology. Complex 5 affords a one-dimensional chain structure, and complex 6 shows a two-dimensional (4,4) network further connected into a 3D supramolecular structure connected by intermolecular hydrogen bonds and by π-π interactions. In addition, the luminescent properties of complexes 2 and 3 as well as the magnetic properties of 4 and 5 were studied.

Six new coordination polymers, namely, [Co(Cl-BDC)(H2MDP)]·0.5H2O (1), [Cd(Cl-BDC)(H2MDP)] (2), [Cd(OH-ip)(H2MDP)2]·H2O (3), [Mn(NO2-ip)(H2MDP)(H2O)] (4), [Cu(BTEC)1/2(H2MDP)] (5), and [Co(BTEC)1/2(H2MDP)]·H2O (6) (H2MDP = methylenebis(3,5-dimethylpyrazole), Cl-H2BDC = 2,5-dichloroterephthalic acid, OH-H2ip = 5-hydroxy-1,3-benzenedicarboxylic acid, NO2-H2ip = 5-nitro-1,3-benzenedicarboxylic acid, H4BTEC = 1,2,4,5-benzenetetracarboxylic acid) have been hydrothermally synthesized by using H2MDP as the main ligand and varying aromatic acids as auxiliary ligands, and characterized by single-crystal X-ray structure determination, FT-IR, elemental analysis, and powder X-ray diffraction. It was found that in complexes 2, 3, 4, and 6 the H2MDP ligands adopt a cis-conformation and tend to form M2L2-type metallocyclic units (SBU-1). These metallocyclic units further serve as linkers to connect the {metal–aromatic carboxylate}n chains to form two-dimensional frameworks with different structural features and topologies, i.e. 2D 63-hcb network for 2, (4,4) net for 3, undulated 63-hcb layered framework for 4, and dual (3,4)-connected net for 6 with point (Schlafli) symbol of (4·62)2(42·62·82). In complexes 1 and 5, the H2MDP ligands adopt a trans-conformation, and tend to link {metal–aromatic carboxylate}n chains into a higher dimensional framework, i.e. 3D triply interpenetrated dia network for 1 and dual (4,4)-connected double-layered structure for 5 with point (Schlafli) symbol of (54·62)(55·81)2. Moreover, the magnetic properties of complexes 1 and 6, and photoluminescent properties of 3 have also been investigated.

Seven new metal–organic frameworks (MOFs), namely, {[Cd2(NDC)2(H2MDP)](H2O)} (1), [Cd(NDC)(H2MDP)] (2), {[Cd2(NDC)(HNDC)2(H2MDP)2](H2O)0.5} (3), [Cd(NH2–BDC)(H2MDP)2] (4), [Cd(NH2–BDC)(H2MDP)2] (5), [Cd(H2MDP)(Br–BDC)0.5(Br–HBDC)] (6), {[Co(H2MDP)(Br–BDC)](H2O)0.5} (7) (H2MDP = methylenebis(3,5-dimethylpyrazole), H2NDC = 1,4-naphthalenedicarboxylic acid, NH2–H2BDC = 2-amino-1,4-benzenedicarboxylic acid, Br–H2BDC = 2,5-dibromo-1,4-benzenedicarboxylic acid) have been controllably synthesized with H2MDP and different aromatic dicarboxylic acids by tuning metal-to-ligand molar ratios, temperature, solvents and metal ions. Compound 1 is a 3D 2-fold interpenetrated pcu framework of 412·63 topology constructed from paddle-wheel SBUs and trans-conformation H2MDP pillars, while compound 2 exhibits a 3D 3-fold interpenetrated diamondoid framework formed by single metal nodes via linear NDC2− and trans-conformation H2MDP ligands. Interestingly, compound 3 contains two different types of binuclear subunits formed by a pair of Cd(II) ions with partly deprotonated HNDC− ligands, and these subunits are further linked by completely deprotonated NDC2− and cis-conformation H2MDP ligands to form a 2D (4,4) network. Compounds 4 and 5 are solvent-induced structural isomers based on 2D (4,4) layers, and therefore have different solvent-accessible voids. Compounds 6 and 7, synthesized with different metal salts under similar solvothermal conditions, are characteristic of a 3D hydrogen-bonded supramolecular network, and a 3D 3-fold interpenetrated diamondoid network with equal number of left- and right-handed helical {Cd(H2MDP)}n chains further bridged together by linear Br–BDC2− ligands, respectively. In addition, the luminescent properties of solids 1–6 have been investigated at room temperature.