Uranyl Phosphonate Research Articles

Enhancing the uranium (VI) adsorption performance of phosphoric acid functionalized porous silica by controlled introduction of phosphoric acid group

The post-grafting of porous silica with organic group is a common method for the synthesis of organo-functionalized silica adsorbent. However, this method usually produces adsorbents with limited adsorption performances due to the pore blocking caused by the irregular introduction of organic group. In this work, we report the controllable synthesis of phosphoric acid functionalized porous silica adsorbent based on the co-condensation method for uranium (VI) adsorptive removal with enhanced adsorption performance. Characterizations of the obtained silica verify its porous structure and confirm the homogeneous distribution of phosphoric acid groups inside the silica. This silica is able to efficiently remove 98 % of uranium from a 100 mg/L uranium (VI) solution within 10 min at a dosage of 0.6 g/L and the maximum uranium (VI) adsorption amount reaches 509 mg/g. Both adsorption capacity and adsorption rate of this silica are superior than that of the silica synthesized based on conventional post-grafting method. Moreover, this silica can be reused for five times with uranium (VI) removal efficiency above 95 % and it is well applied in adsorption column for dynamically adsorptive removal of uranium (VI) from real nuclear wastewater. Mechanism-related investigations reveal that uranium (VI) adsorption on this silica proceeds by effective ion exchange of uranium (VI) ion with either phosphoric acid or silanol group and the formation of uranyl phosphonate or uranyl silicate complex. This work provides a feasible strategy to synthesize functionalized porous silica without significant pore blocking, and demonstrates the enhancement effect of regulating surface adsorption groups on the adsorption performances of porous silica. Besides, this work offers a promising adsorbent for efficient treatment of uranium-containing nuclear wastewater and reveals the mechanism of uranium adsorption on those silica adsorbent containing phosphoric acid, thiol or thioether group.

Unraveling the role of coordinated water in the capture of americium and toxic gases by an ultrastable uranyl phosphonate framework

The design and fabrication of uranium phosphonate frameworks (UPFs) pave a potential avenue to reduce the environmental risk of depleted uranium, transuranium waste, and toxic gases while adding to its waste to utility virtues. However, it remains unknown how the pervasive coordinated water of UPFs influences their performances in radionuclide and toxic gas separation. Toward this end, we prepared a new category of porous UPFs, namely UPF-205 with abundant coordinated water and resulting hydrogen bonding nanotraps. The coordinated water is synergistic in quantitatively removing trivalent f-elements (i.e., Am3+, Eu3+) from wide-ranging pH solutions together with proximal phosphonate groups at a low metal concentration. Most importantly, an unprecedented coordinated water-mediated Eu3+-UO22+ transmetalation had been verified at a relatively high metal concentration. The high-density open uranyl sites and optimal pore size triggered by the dehydration of coordinated water also contribute to the enhanced adsorption of toxic SO2 and NH3. Our work shows great relevance for the rational design of ultrastable UPFs as both depleted uranium waste forms and efficient adsorbents for radiological/nuclear protection.

Unique porous framework constructed by uranyl phosphonate with high structural stability and preferential ion exchange capacity

Unique porous framework constructed by uranyl phosphonate with high structural stability and preferential ion exchange capacity

Cation directed formation of uranyl phosphonocarboxylates frameworks comprised of cross-linked chains

Three new uranyl phosphonate frameworks with barium or lead were hydrothermally synthesized using phosphonoacetate and phosphonopropionate ligands. The first two frameworks are made up of cross-linked chains that are comprised of uranyl pentagonal bipyramids connected by the three oxygen atoms of the phosphonate tetrahedra. The carboxylates of the ligands bond to the uranyl ions of other chains to form the perpendicular rows that comprise the framework. The third framework is similar to the first, being comprised of interpenetrating chains. However, the longer carbon chain of the phosphonopropionate allows for a less strained packing of the chains. The crystallization of the barium uranyl phosphonate framework was investigated as a function of iron concentration using scanning electron microscopy. The use of iron to grow larger crystals of the phosphonoacetate lead framework is also described. The barium containing framework was found to disassociate in water with the chains disassociating from each other.

Reticular chemistry of uranyl phosphonates: synthesis, design, and beyond

The successful design strategy put reticular chemistry in uranyl phosphonate frameworks, which integrate multifunction to corresponding applications.

Regulating the Porosity of Uranyl Phosphonate Frameworks with Quaternary Ammonium: Structure, Characterization, and Fluorescent Temperature Sensors.

Regulating the porosity of metal phosphonate frameworks is still challenging, even though this is not an issue for carboxylate-based metal-organic frameworks (MOFs). Quaternary ammonium cations are common template reagents widely used for structure control. However, it is not successful for uranyl phosphonate frameworks (UPFs) because the large volume sizes of templates make it challenging to enter the channels constructed by phosphonate ligands with small pore sizes and low dimensions. In this work, three new porous three-dimensional UPFs were synthesized using the phosphonate ligand and template reagents with the same geometry, namely, (TEA)2(UO2)3(TppmH4)2·2H2O (UPF-106), (TPA)2(UO2)3(TppmH4)2 (UPF-107), and (TBA)2(UO2)5(TppmH2)2(H2O)2·4H2O (UPF-108). The porosity of the UPFs in this work showed a positive relation with the sizes of the template ammonium cations. Thermogravimetric analysis and infrared and ultraviolet spectroscopy were performed. The variable-temperature fluorescence spectra of the three compounds showed that the fluorescence intensity has an excellent relation to temperature with a potential application as fluorescence temperature sensors.

A 3D uranyl phosphonate framework: Structure, characterization, and fluorescence performance

A three-dimensional uranyl phosphonate framework [BTA][(UO2)3(TppmH)(H2O)3]•0.75H2O (UPF-109) (Tppm = tetrakis[4-(dihyroxyphosphoryl)phenyl]methane, BTA = benzyltriethylammonium chloride) has been synthesized using the hydrothermal method. The structure of UPF-109 shows that dimers and monomers are connected to give a two-dimensional layer, and Tppm ligands link the layers to give a 3D structure with two types of channels. To provide more detailed information, PXRD, TG, IR, UV-vis, and photoluminescence were performed. In addition, the relation between fluorescence intensity and temperature demonstrates the potential application of UPF-109 in fluorescence temperature sensors.

Layered Uranyl Phosphonates Encapsulating Co(II)/Mn(II)/Zn(II) Ions: Exfoliation into Nanosheets and Its Impact on Magnetic and Luminescent Properties.

Layered heterometallic 5f-3d uranyl phosphonates can exhibit unique luminescent and/or magnetic properties, but the fabrication and properties of their 2D counterparts have not been investigated. Herein we report three heterobimetallic uranyl phosphonates, namely, [(UO2 )3 M(2-pmbH)4 (H2 O)4 ] ⋅ 2H2 O [MU, M=Co(II), CoU; Mn(II), MnU; Zn(II), ZnU; 2-pmbH3 =2-(phosphonomethyl)benzoic acid]. They are isostructural and display two-dimensional layered structures where the M(II) centers are encapsulated inside the windows generated by the diamagnetic uranyl phosphonate layer. Each M(II) has an octahedral geometry filled with four water molecules in the equatorial positions and two phosphonate oxygen atoms in the axial positions. The uranium atoms adopt UO7 pentagonal bipyramidal and UO6 square bipyramidal geometries. The lattice and coordination water molecules can be released by thermal treatment and reabsorbed in a reversible manner, accompanied with changes of magnetic dynamics. Interestingly, the bulk samples of MU can be exfoliated in acetone via freezing and thawing processes forming nanosheets with single-layer or two-layer thickness (MU-ns). Magnetic studies revealed that the CoU and MnU systems exhibited field-induced slow magnetization relaxation at low temperature. Compared with crystalline CoU, the magnetic relaxation of the CoU-ns aggregates is significantly accelerated. Moreover, photoluminescence measured at 77 K showed slight red-shift of the five characteristic uranyl emission bands for ZnU-ns in comparison with those of the crystalline ZnU. This work gives the first examples of 2D materials based on 5f-3d heterometallic uranyl phosphonates and illustrates the impact of dimension reduction on their magnetic/optical properties.

A Multifunctional Porous Uranyl Phosphonate Framework for Cyclic Utilization: Salvages, Uranyl Leaking Prevention, and Fluorescent Sensing.

The material for managing and monitoring waste made from the waste itself is an excellent example of cyclic utilization, which could reduce issues and be more sustainable. A three-dimensional porous uranyl phosphonate MOF (UPF-105) was synthesized via a hydrothermal method. UPF-105 is stable in aqueous solution with pH in the range of 1-11 and maintains crystallinity below 215 °C. The uncoordinated phosphonate groups in the channels act as functional anchors to selectively capture uranyl ions, with a maximum uranium adsorption capacity of 170.23 mg g-1. The fluorescence of UPF-105 makes it a good candidate for a uranyl ion sensor in uranium-contaminated solutions with concentrations in the range of 5-90 ppm.

Lanthanide-uranyl phosphonates constructed from diethyl ((phenylsulfonyl)methyl)phosphonate.

Lanthanide-uranyl phosphonates possess intriguing crystal structures and huge application prospects, but the construction of these materials remains challenging. In this work, we demonstrate that new uranyl and lanthanide-uranyl sulfonylphosphonates with elegant crystal structures and photophysical properties can be assembled hydrothermally by employing the heterofunctional diethyl phosphonate (diethyl ((phenylsulfonyl)methyl)phosphonate, Et2L) as a precursor ligand, which provides an effective strategy for the construction of lanthanide-uranyl phosphonates.

Heterometallic uranyl-organic frameworks incorporating manganese and copper: Structures, ammonia sorption and magnetic properties

Incorporating transition metal ions into uranyl phosphonate frameworks can bring not only new structure types but also interesting physical or chemical properties. Herein we report two heterometallic uranyl carboxyphenylphosphonates, namely, [Cu2(UO2)3(2-pmbH)2(2-pmb)2(H2O)4]·2H2O (1) and [Mn3(UO2)6(2-pmb)6(H2O)8]·10H2O (2) [2-pmbH3 = 2-(phosphonomethyl)benzoic acid]. Compound 1 shows a two-dimensional layered structure in which uranyl-PO3 chains are linked by {Cu2O2} dimers. Within the uranyl-PO3 chain, {UO6} tetragonal bipyramids and edge-sharing dimers of {UO7} pentagonal bipyramids are connected by edge-sharing {PO3C} tetrahedra. Compound 2 possesses a unique 3D open framework structure, where the Mn-layers are pillared by uranyl-PO3 chains. The uranyl-PO3 chain in 2 is very different from that in 1, which contains trimers of edge-sharing {UO7} and {UO8} polyhedra and {PO3C} linkages. While the Mn-layer consists of chains of {MnO6} octahedra bridged alternatively by carboxylate and phosphonate groups, which are inter-connected by organic moieties of 2-pmb3-. The thermally activated sample of 2 displays strong adsorption capability toward NH3. Magnetic studies revealed dominant antiferromagnetic interactions between the metal centers in both compounds.

Uranyl phosphonates: crystalline materials and nanosheets for temperature sensing.

Ultrathin nanosheets of luminescent metal-organic frameworks or coordination polymers have been widely used for sensing ions, solvents and biomolecules but, as far as we are aware, not yet used for temperature sensing. Herein we report two luminescent uranyl phosphonates based on 2-(phosphonomethyl)benzoic acid (2-pmbH3), namely (UO2)(2-pmbH2)2 (1) and (H3O)[(UO2)2(2-pmb)(2-pmbH)] (2). The former has a supramolecular layer structure, composed of chains of corner-sharing {UO6} octahedra and {PO3C} tetrahedra which are connected by hydrogen bonds between phosphonate and carboxylic groups. Compound 2 possesses a unique 2D anionic framework structure, where the inorganic uranyl phosphonate chains made up of {UO7} and {PO3C} polyhedra are cross-linked by 2-pmb3- ligands. The carboxylic groups of 2-pmbH2- ligands are pendant on the two sides of the layers and form hydrogen bonds between the layers. Both compounds can be exfoliated in acetone via a top-down freeze-thaw method, resulting in nanosheets of two-layer thickness. Interestingly, the photoluminescence (PL) of 1 and 2 is highly temperature sensitive. Variable temperature PL studies revealed that compounds 1 and 2 can be used as thermometers in the temperature ranges 120-300 K and 100-280 K, respectively. By doping the nanosheets into polymer matrix, 1-ns@PMMA and 2-ns@PMMA were prepared. The PL intensity of 1-ns@PMMA is insensitive to temperature, unlike that of the bulk sample. While 2-ns@PMMA exhibits similar temperature-dependent luminescence behaviour to its bulk counterpart, thereby enabling its potential application as a thermometer in the temperature range 100-280 K.

The presence of mixed-valent silver in the uranyl phenylenediphosphonate framework

A 2-D silver uranyl phosphonate presents both Ag+ and Ag0 atoms in the free space between the adjacent layers and the incorporation of the mixed-valent silver sites results in the quenching of the fluorescent emission.

Reticular Chemistry of Uranyl Phosphonates: Sterically Hindered Phosphonate Ligand Method is Significant for Constructing Zero-Dimensional Secondary Building Units.

Designability is an attractive feature for metal-organic frameworks (MOFs) and essential for reticular chemistry, and many ideas are significantly useful in the carboxylate system. Bi-, tri-, and tetra-topic phosphonate ligands are used to achieve framework structures. However, an efficient method for designing phosphonate MOFs is still on the way, especially for uranyl phosphonates, owing to the complicated coordination modes of the phosphonate group. Uranyl phosphonates prefer layer or pillar-layered structures as the topology extension for uranyl units occurs in the plane perpendicular to the linear uranium-oxo bonds and phosphonate ligands favor the formation of compact structures. Therefore, an approach that can construct three-dimensional (3D) uranyl phosphonate MOFs is desired. In this paper, a sterically hindered phosphonate ligand method (SHPL) is described and is successfully used to achieve 3D framework structures of uranyl phosphonates. Four MOF compounds ([AMIM]2 (UO2 )(TppmH4 )⋅H2 O (UPF-101), [BMMIM]2 (UO2 )3 (TppmH4 )2 ⋅H2 O (UPF-102), [Py14]2 (UO2 )3 (TppmH4 )2 ⋅3 H2 O (UPF-103), and [BMIM](UO2 )3 (TppmH3 )F2 ⋅2 H2 O (UPF-104); [AMIM]=1-allyl-3-methylimidazolium, [BMMIM]=1-butyl-2,3-dimethylimidazolium, [Py14]=N-butyl-N-methylpyrrolidinium, and [BMIM]=1-butyl-3-methylimidazolium) are obtained by ionothermal synthesis, with zero-dimensional nodes of uranyl phosphonates linked by steric tetra-topic ligands, namely tetrakis[4-(dihyroxyphosphoryl)phenyl]methane (TppmH8 ), to give 3D framework structures. Characterization by PXRD, UV/Vis, IR, Raman spectroscopy, and thermogravimetry (TG) were also performed.

Structural Tuning and Sensitization of Uranyl Phosphonates by Incorporation of Countercations into the Framework.

By the introduction of terephthalic acid, tetramethylammonium chloride, and Zn2+ ions, three new uranyl triphosphonates with varying crystal structures, namely, [H3O][(UO2)2(HL)]·H2O (1), [NMe4][(UO2)2(HL)(H2O)]·H2O (2), and [(UO2)3Zn(H2L)2(H2O)2]·3H2O (3), where H6L = benzene-1,3,5-triyltris(methylene) triphosphonic acid, have been successfully synthesized and characterized by means of powder and single crystal XRD, IR, EA, TGA, UV-vis, and luminescence. These three compounds all possess three-dimensional framework structures with hydrium, tetramethylammonium, and Zn2+ as the respective countercations. The uranium(VI) center luminescence of compounds 1 and 2 is completely quenched. However, the incorporation of Zn2+ into the matrix of uranyl phosphonate in the case of compound 3 results in the emerging of the typical intense vibronic emissions of U(VI), demonstrating that zinc phosphonate can behave as sensitizer of uranyl phosphonates. The quenching and sensitization mechanism were also discussed.

A supramolecular uranyl phosphonate [BTEA]2[(UO2)2(1,3-pbpH2)2F2]: Synthesis, structure, and spectroscopic characterization

In this work, a uranyl phosphonate [BTEA]2[(UO2)2(1,3-pbpH2)2F2] (1) (1,3-pbp = 1,3-phenylenebis(phosphonic acid), BTEA = benzyltriethylammonium cation) has been synthesized hydrothermally and characterized by single crystal X-ray diffraction, showing one-dimensional chain structure of uranium phosphonate which is isolated by BTEA cations and achieve three-dimensional supramolecular architecture by non-covalent interactions. In addition, powder X-ray diffraction, thermal stability, UV absorption, temperature dependent fluorescence, Infrared, and Raman spectroscopies have been performed.

A uranyl phosphonate framework with a temperature-induced order–disorder transition and temperature-correlated photoluminescence

UPF-1 experiences a thermally induced order–disorder transition, leading to a negative linear correlation between the photoluminescence intensity and temperature, and may find application as a luminescent thermometer.

Fabrication of New Uranyl Phosphonates by Varying Quaternary Ammonium Cation: Synthesis, Structure, Luminescent Properties, and Single-Crystal to Single-Crystal Transformation.

Four new uranyl triphosphonates, namely, [N(CH4)4][UO2(H3L)][H2O] (1), [(UO2)1.5(H3L)(H2O)1.5][H2O] (2), [NBu4][(UO2)3.5(H2L)2][(H2O)4.5] (3), and [(UO2)1.5(H3L)(H2O)2.5][(H2O)2.5] (4), where H6L = benzene-1,3,5-triyltris(methylene)triphosphonic acid, were obtained from a triphosphonate ligand in the presence of different quaternary ammonium cations. The structural characterization revealed that the introduction of quaternary ammonium cation had a major impact on the structure formation of uranyl phosphonates. Compound 1 possesses a three-dimensional anionic framework structure. Tetramethylammonium cations are accommodated in the channels, serving as counterions and structure directing agents. Compound 2 also displays a three-dimensional framework structure but is neutral, because the tetrapropylammonium cations are not involved in the crystal structure. Compound 3 has an intercalation structure; between the layers are the tetrabutylammonium cations, balancing the charge and strengthening the supramolecular structure with C-H···O interactions. No obvious uptake of N2 and CO2 could be observed for compound 2 due to the shrinkage of the framework and structural transformation. Compound 2 undergoes single-crystal to single-crystal transformation under vacuum, leading to the formation of compound 4, which possesses a two-dimensional layer structure. The photophysical properties of these compounds were also investigated.

A new uranyl triphosphonate constructed from semi-rigid triphosphonate ligand: New method for the construction of higher dimensional uranyl phosponates

A new uranyl triphosphonate with three-dimensional crystal structure has been synthesized from a semi-rigid triphosphonate ligand using hydrothermal method. The employment of triphosphonate ligand may provide a new strategy for the construction of higher dimensional uranyl phosphonates. The thermal and luminescent properties were also investigated.

Construction of Uranyl Organic Hybrids by Phosphonate and in Situ Generated Carboxyphosphonate Ligands.

The hydrothermal reaction of uranyl ions with (5-methyl-1,3-phenylene)diphosphonic acid (H4MPDP) in the presence of additives such as nitric acid, N-bearing species, and heterometal ions yielded five new uranyl organic hybrids: (H3O)[(UO2)5(H2O)4(H3DPB)2(H2DPB)(HDPB)]·2H2O (1), (Hphen)(phen)[(UO2)3(H2DPB)(HDPB)] (2), (H2dipy)[(UO2)3(MPDP)2] (3), Zn(bipy)(UO2)(MPDP) (4), and Co(bipy)(UO2)(MPDP)·H2O (5) (H5DPB = 3,5-diphosphonobenzoic acid; phen = 1,10-phenanthroline; dipy = 4,4'-bipyridine; bipy = 2,2'-bipyridine). Single-crystal X-ray diffraction (XRD) demonstrates that 1 and 2 are 3D frameworks constructed of uranyl centers and carboxyphosphonate DPB ligands; the latter were formed via the in situ oxidation of H4MPDP. In the homometallic uranyl diphosphonate 3, less common UO6 square bipyramids connected by MPDP ligands were incorporated to form the 2D assembly. A further introduction of heterometal ions produced two heterobimetallic uranyl phosphonates 4 and 5. Both of them show layered structures, formed by UO6 square bipyramids linked by MPDP ligands with heterometal-centered polyhedra decorated on the sides of the layers. It is found that the pH and heterometal ions have significant effects on the structures of the complexes. In addition to the syntheses and XRD characterization, the spectroscopic properties of these uranyl complexes were also addressed. To complement the experimental results, density functional theory calculations were carried out on several model complexes that feature a homo- or heterobimetallic molecular skeleton. Geometrical/electronic structures, IR spectra, and electronic absorptions were discussed.