Cs Ions Research Articles

Construction of MIL-100(Fe)-DMA material for efficient adsorption of Sr and Cs ions from radioactive wastewater

A novel metal-organic framework (MOF) material, MIL-100(Fe)-DMA, was synthesized using the solvothermal method. The structure of the MOF was characterized using scanning electron microscopy-energy dispersive X-ray spectroscopy, N2 adsorption–desorption isotherms, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy. Batch adsorption experiments were performed to investigate the effects of initial Sr2+ and Cs+ concentrations, adsorption time, pH, and coexisting cations on the adsorption performance of the material. The adsorption mechanism was further elucidated using adsorption kinetics and isotherm models. The results indicated that the adsorption of Sr2+ and Cs+ does not significantly affect the MOF material structure. As reaction time and initial ion concentration increased, the adsorption capacity of MIL-100(Fe)-DMA for Sr2+ and Cs+ increased rapidly and then gradually reached equilibrium. Optimal adsorption occurred under alkaline conditions, with maximum adsorption capacity observed at pH = 8. The adsorption process for Sr2+ and Cs+ was well described by the pseudo-second-order kinetic model, the Weber–Morris model, and the Langmuir adsorption isothermal model. The adsorption process was mainly identified as monolayer chemical adsorption, influenced by multiple factors. Characterization combined with density functional theory calculations revealed that the unsaturated carboxylic acid groups on the surface of the MOFs play a crucial role in the interaction with Sr2+ and Cs+.

Sorption behavior of strontium ions by graphene oxide decorated with chitosan nanoparticles from aqueous solutions

This study provides and investigates the fabrication of graphene oxide (GO) sheets decorated with chitosan nanoparticles (CSNP) through the hybridizing of GO and CS, by the addition of tetraethyl orthosilicate (TEOS) as a cross-linker agent. The fabricated GO-CSNP composite was characterized using several advanced techniques. Furthermore, various parameters affect the sorption of Sr(II), such as contact time, pH, initial concentration, dosage, temperature, and coexisting ions. The experimental results were in accordance with the pseudo-second-order reaction. The interaction mechanism between Sr(II) and GO-CSNP composite was accurately described by the Langmuir isotherm model with a maximum adsorption capacity of 473.93 mg/g. The GO-CSNP composite demonstrated exceptional selectivity for the sorption of Sr(II) over Y(III) at a high concentration ratio of 10:1 for Sr2+ to Y3+, respectively. Furthermore, the GO-CSNP adsorbent demonstrated considerable potential as a highly effective sorbent for the adsorption of Sr(II), Mo(VI), Cd(II), and Cs(I) ions. The results revealed that the prepared composite was effectively capable of removing various fission products.

Dual ionotropic crosslinked biopolymer magnetic nanocomposites as 5‐Fluorouracil nanocarrier for potential colorectal cancer treatment

AbstractThis study aimed to synthesize dual‐crosslinked chitosan‐alginate nanocomposites (Cs‐Alg/IO NCs) using green‐synthesized iron oxide nanoparticles (IO, Fe3O4 NPs) for drug delivery application. The NCs, formed via ionotropic gelation with sodium tripolyphosphate (TPP) and calcium chloride (CaCl2) as crosslinking agents for Cs and Alg, respectively, and further characterized for physiochemical properties. The presence of Fe3O4 NPs and 5‐Fluorouracil (5FU) increased hydrodynamic size (153.12 ± 0.57 to 207.64 ± 3.59 nm). Morphological studies revealed NC agglomeration within nanoscales. 5FU‐loaded Cs‐Alg/IO NCs (Cs‐Alg/IO 5FU NCs) exhibited superparamagnetic behavior and sustained drug release under various pH conditions. Cytotoxicity assays on colon cancer cells (HCT116 and HT‐29) and normal colon cells (CCD‐112) indicated higher cancer cell selectivity (selectivity index, SI = 1.91) in 2D models. Elevated IC50 values in 3D models were linked to lower drug loading capacity (LC) and encapsulation efficiency (EE). Overall, the study highlights the potential of dual‐crosslinked biopolymer NCs with green‐synthesized Fe3O4 NPs for developing an anticancer drug delivery system in colorectal cancer treatment.Highlights Synthesis of 5FU‐loaded dual crosslinked Cs‐Alg/IO NCs and Cs‐Alg IPN. Physicochemical characterization of cross‐linked magnetic nanocarriers. Investigation of sustained drug release using superparamagnetic nanocarriers. Evaluation of selective cytotoxicity for Cs‐Alg/IO 5FU NCs.

Investigating the Role of Cs Species in the Toluene–Methanol Side Chain Alkylation Catalyzed by CsX Catalysts

The side chain alkylation of toluene with methanol was studied on a series of CsX catalysts prepared by varying the Cs species and ion exchange conditions. The effects of various parameters, such as the exchanging temperatures and times on the adsorption/activation properties of different CsX catalysts, were investigated by combining a variety of characterization means for understanding the role of Cs species in the side chain alkylation reaction. On the basis of the various characterization results and their related literature results, it can be proposed that the Cs ions located on the ion-exchanged sites of X zeolites could effectively adsorb and activate toluene molecularly through modifying the basicity of framework oxygen, whereas the cluster of cesium oxide (Cs2O) could ensure the effective conversion of methanol into formaldehyde. Additionally, Cs ions can promote the production of monodentate formate, which enhances the selectivity of styrene. However, too much Cs2O will lead to the excessive decomposition of methanol into CO2, CO, and H2, thus inhibiting the production of styrene. In summary, the presence of suitable amounts of Cs ions and Cs2O clusters plays a significant role in the formation of the side chain products of styrene and ethylbenzene.

Utilizing low-cost purple coneflower (Echniacea purpurea) marc for competitive sorption of 152+154Eu(III), 60Co(II) and 134Cs(I) radionuclides

Echinacea purpurea marc (EPM), a residual of echinacea herb after the extraction process, was used as a natural low-cost sorbent for competitive sorption of 152+154Eu(III), 60Co(II) and 134Cs(I) radionuclides. The EPM was ground to prepare it for use in the sorption process. The variables influencing the sorption process were assessed, including pH, contact time, concentrations of metal ions, and temperature. EPM was characterized by different analytical instruments such as FTIR, SEM, XRD, and DTA/TGA. pH 4.0 was selected as the ideal pH value for competitive sorption of the studied ions. Adsorption kinetics data found that the sorption followed a pseudo-second-order model. The adsorption isotherm data was significantly better suited by the Langmuir isotherms in the case of Eu(III) ions while following Freundlich in the case of Co(II) and Cs(I) ions. Positive ΔHo values confirm the endothermic character of metal ion sorption onto EPM. The loading efficiencies of Eu(III), Co(II), and Cs(I) ions in the EPM column were 66.67%, 9.59%, and 4.81%, respectively. The EPM is a cost-effective and efficient separation of Eu(III) ions more than Cs(I) and Co(II) ions. Therefore, in the future, it will be a starting point for the separation of trivalent elements of lanthanide ions.

SORBENTS BASED ON THE Ni,Fe-LAYERED DOUBLE HYDROXIDES AND ITS MAGNETIC NANOCOMPOSITES FOR DEACTIVATION AND PRECONCENTRATION OF Cs(I) AND Sr(II) IONS FROM AQUEOUS SOLUTIONS

The synthesis and comparative evaluation of the adsorption capacity in relation to Sr(II) and Cs(I) ions of the carbonate form of Ni(II)/­Fe(III)–layered double hydroxides (NiFe-LDH) and their nanocomposites was carried out. At first, Fe3O4 nanoparticles having a crystallite size of 20–50 nm were obtained by Fe(III) precursors. In the second step, Fe3O4 nanoparticles were embedded in NiFe-LDH matrix by the co-precipitation at hydrothermal conditions and subsequent condensation of the basic solution containing Fe3O4nanoparticles. The influence of the physicochemical parameters of the synthesized sorbents on the efficiency of magnetic solid phase extraction of these radionuclides from aqueous solutions was investigated. Their effectiveness in extracting Sr(II) and Cs(I) ions with a change in the pH of the aqueous medium was evaluated, as well as sorption isotherms on the obtained sorbents at pH0 4.5–5.0 were obtained, and their analysis and processing were carried out to establish the mechanism of sorption extraction at all le­vels of filling of the sorption layer with analytes. Equilibrium adsorption data were analyzed using Freundlich and Langmuir isotherm models. Of the models tested, Langmuir isotherm expressions were found to give better fit to the experimental data compared to the Freundlich model. The applicability of mathematical models for estimating the kinetic patterns of sorption of radionuclides on NiFe-LDH and their magnetic nanocomposites was analyzed. The adequacy of the Boyd and Morris – Weber diffusion models in the initial section (up to F = 0.4–0.6) of the kinetic curves is shown. Kinetically, the growth of effective diffusion coefficients and adsorption rate constants is observed in the series: Fe3O4<NiFe-LDH<Fe3O4@NiFe-LDH, and the pseudo-second-order kinetic model most accurately reflects the patterns of sorption of these radionuclides. Due to high sorption efficiency and manufacturability, the obtained sorbents are promising for water purification from radioactive pollutants.

New insights into the mechanism of cesium sorption on titanium hexacyanoferrate: Experimental findings and model development

This study aimed to provide new insights into the mechanism of Cs+ sorption on titanium hexacyanoferrate (Ti–Fe PBA) focusing on the influence of the structure and vacancies. Ti–Fe PBA was synthesized with specific vacancies using a coprecipitation synthesis method. The study successfully demonstrated the unique structure of Ti–Fe PBA and determined the ratio of vacancies within its framework through various characterization techniques, including X-ray diffraction, Fourier transform-infrared spectrometry, thermogravimetry, scanning electron microscopy, X-ray photoelectron spectroscopy and sodium hydroxide titration. The synthesized Ti–Fe PBA exhibited an impressive Cs+ sorption capacity of 3.53 mmol g−1 and demonstrated high selectivity, with a Kd value 1.5 × 106 for Cs+ sorption. In addition, Ti–Fe PBA displayed excellent stability, rapid uptake kinetics and maintained high selectivity, even in the presence of high concentrations of coexisting ions. Moreover, our new findings revealed that K–Cs ion exchange specifically occurring at the interstitial sites within the framework structure accounted for ∼35 % of the total Cs+ sorption. A sorption-surface complexation model utilizing a coupling technique that integrated PHREEQC with Python enabled in-depth analysis of titration, pH effects and sorption isotherms. The modelling results revealed that the strong ion exchange sites ≡SsOH and ≡SsONa on surfaces and vacancies contributed ∼65 % of the total Cs+ sorption.

Spongy porous CuFe Prussian blue deposited MXene nanosheets for quick removal of cesium ions from wastewater and seawater

The radioactive 137Cs is hazardous to human health and the environment once it is released into the environment due to its high radioactivity and solubility. Here, CuFe Prussian blue deposited MXene nanosheets (CuFe/MXene) was successfully prepared and used to capture Cs(I) ions from wastewater and seawater. Among them, spongy porous CuFe/MXene-2 can, not only facilitate the diffusion and adsorption of Cs(I) ions, but also avoid the stacking and agglomeration of CuFe, thus improving the effective utilization rate of CuFe. Consequently, CuFe/MXene-2 can remove up to 88.2% of Cs(I) ions within 3 min and reach the adsorption equilibrium of Cs(I) ions within 20 min with the maximum adsorption capacity (qmax) of 326.8 mg/g. Additionally, the removal rate of Cs(I) by CuFe/MXene-2 can reach up to 90% even in 0.5 M HNO3 solution and Cs(I) spiked seawater containing various competitive cations. More importantly, CuFe/MXene-2 can efficiently and selectively adsorb Cs(I) ions with excellent reusability.

Origin of Microstrain in FAPbI3 Perovskite and Its Effect on the Stability

Lattice strain is often regarded as an important factor affecting the stability of organic–inorganic hybrid perovskite solar cells, but the current understanding on the origin of the strain is still unclear. Herein, the microstructure of formamidinium perovskite is analyzed by the Rietveld refinement method to reveal the origin of its microstrain. It is found that there is a lattice mismatch between the α‐phase perovskite and the δ‐phase impurity during the fabrication process, which generates strong microstrain in perovskite film. Moreover, the strain also exacerbates the aging process of formamidinium perovskite. By introducing Cs ions, the lattice mismatch of α‐phase and δ‐phase perovskites is reduced, thereby reducing the microstrain of perovskites and improving the device performance.

Molecular dynamics study on structural characteristics and mechanical properties of sodium aluminosilicate hydrate with immobilized radioactive Cs and Sr ions

As a low-carbon, environment-friendly and economical resource for nuclear power generation, radionuclide emission and storage has received worldwide attention. Geopolymer concrete is a green and sustainable building material that can be used to immobilize radionuclides. In the present study, molecular dynamics simulations were conducted to investigate the structural and mechanical properties of sodium aluminosilicate hydrate (NASH) gel, the main component of geopolymer concrete, with/without immobilized radioactive Cs and Sr ions. The three-dimensional structure of NASH gel enabled good immobilization of both radioactive Cs and Sr ions owing to the large radius of Cs ions and high charge density of Sr ions. Addition of Cs ions reduced the strength of the gel and increased the fracture strain, whereas addition of Sr ions increased the strength and significantly increased the ductility. Addition of Sr ions increased the number of penta-coordinated Al in the structure. Consequently, breakage of these bonds required more energy to be absorbed from outside. The nanoscale molecular dynamics simulations provided a theoretical support at atomic level for understanding the structural and mechanical characteristics of geopolymers pertinent to the immobilization of nuclear waste.

Adsorption and migration of Cs and Na ions in geopolymers and zeolites

Geopolymers may provide a more sustainable alternative to Portland Cement for various possible applications. Geopolymers have attracted particular interest for the immobilization of pollutants, owing to their high adsorption capacity, high thermal and chemical resistance, and low leachability. However, practical implementation is currently hindered by a limited understanding of how adsorption processes occur in geopolymers, and how they can be engineered to optimize the incorporation of pollutants and avoid their release. In this work, Molecular Dynamics simulations provide insights into these processes at the atomic scale, studying the role of host material composition and structure in the immobilization of Na and Cs ions. The simulations reveal that the most stable configurations for these ions are near the center of 6- and 8-membered aluminosilicate rings, where the coordination with the geopolymer is maximum. Higher contents of Al and degrees of crystallinity are found to yield more stable configurations for Cs ions, with more favorable adsorption enthalpies and lower diffusion coefficients. The comparison of different crystalline zeolite structures reveals that the framework of sodalite, used as the baseline to develop model geopolymer structures, is the most suitable for the immobilization of Cs since there are no channels and it is formed by small 4- and 6-member, all preventing Cs ions from escaping the cavities.

High-stability lead-free tin(II)-perovskites by A-site cation engineering and surface-passivating engineering for high-performance hybrid bulk-heterojunction photodetectors

Tin-based perovskites have attracted more and more attention in recent years due to their non-toxic properties. However, the poor stability of Tin-based perovskites severely limits its further applications. In order to obtain more stable Tin-based perovskites, in this work, Cs ions are introduced as a precursor besides SnF2 during the synthesis of Tin-based perovskites. Further, poly(N-vinylcarbazole) (PVK) is introduced into the above perovskites to improve the separation rate of photogenerated carriers and to suppress both O2 and H2O diffusion into Tin-perovskites. Enhanced-performance Tin-based perovskite photodetectors with hybrid bulk-heterojunctions were obtained, and our experimental data showed that the responsivity and the specific detectivity of the photodetectors ITO/ZnO/FA0.9Cs0.1SnBr3:PVK/MoO3/Ag reached to 409.8 A/W and 1.23 × 1014 Jones, respectively, under 25.3 μW/cm2 405 nm illumination at − 0.2 V. In addition, the devices also show great stability, whose photocurrent decreases only slightly after its deposing in glove box for 14 days. Thus, such a kind of combing A-site cation engineering with surface-passivating engineering on hybrid bulk-heterojunction provides a facile method for high-performance Tin-perovskite photodetectors with high-stability.

Dielectric response and polarization mechanism of alkali silicate glasses in gigahertz to terahertz frequency range

AbstractOxide glasses are dielectric materials with potential applications in high‐frequency communications; hence, their dielectric properties in the gigahertz to terahertz frequency range should be investigated. In this study, the dielectric properties of silica glass and five single alkali silicate glasses were measured at 0.5–10 THz using terahertz time‐domain spectroscopy and far‐infrared spectroscopic ellipsometry. At 0.5–10 THz, the silica glass exhibited low dielectric dispersion with a low dielectric constant and loss. By contrast, the alkali silicate glasses exhibited high dielectric dispersion, and the dielectric constant and loss were higher than those of the silica glass. The shape of the dielectric dispersion profile depended on the alkali‐metal ions; it was broader for lighter ions such as Li ions and sharper for heavier ions such as Cs ions. The peak dielectric loss shifted toward a lower frequency as the weight of the alkali‐metal ions in the alkali‐silicate glass increased. To understand the dielectric dispersion, the complex permittivity was calculated using molecular dynamics simulations. The theoretical results qualitatively agreed with the experimental data. Ion dynamics analysis revealed that alkali‐metal ions vibrate and migrate under an applied electric field, which affects the dielectric constant and loss of alkali‐silicate glasses at gigahertz to terahertz frequencies. To fabricate filter devices at low temperatures, alkali metals should be added to silicate glass; therefore, a minimum amount of light alkali metals should be used to minimize the dielectric loss of the glass materials while maintaining productivity.

Effect of low energy cesium ion irradiation on vanadium oxide: Structural and spectroscopic study

Vanadium di-oxide (VO2) and vanadium tetra oxide (V2O4) powders are exposed to cesium (Cs) ion irradiation using Pelletron accelerator. The energy of the Cs ions ranges from 0.2 keV to 5 keV. Mass spectroscopic data from the accelerator is plotted for various energy ranges. Un-irradiated samples and Cs ion irradiated samples are characterized by using x-ray diffraction (XRD), scanning electron microscope (SEM), Raman spectroscopy and four-point probe method. XRD analysis showed improved VO2 crystallinity after ion irradiation. The V2O4 sample shows amorphous behavior after ion irradiation. Dislocation density and tolerance are calculated to explore structure distortion after ion irradiation. Raman spectroscopy reveals vibrational and rotational modes of bonding with oxygen and vanadium. SEM results explain the reduction in agglomeration after Cs ion irradiation. The resistivity of un-irradiated and irradiated (VO2 and V2O4) samples is calculated by four-point probe method. The resistivity of vanadium oxide is decreased after Cs ion irradiation to make it a potential candidate for optoelectrical applications.

Amorphous BaTiO3 Electron Transport Layer for Thermal Equilibrium‐Governed γ‐CsPbI3 Perovskite Solar Cell with High Power Conversion Efficiency of 19.96%

Compared to organic–inorganic hybrid perovskites, the cesium‐based all‐inorganic lead halide perovskite (CsPbI3) is a promising light absorber for perovskite solar cells owing to its higher resistance to thermal stress. Nonetheless, additional research is required to reduce the nonradiative recombination to realize the full potential of CsPbI3. Here, the diffusion of Cs ions participating in ion exchange is proposed to be an important factor responsible for the bulk defects in γ‐CsPbI3 perovskite. Calculations based on first‐principles density functional theory reveal that the [PbI6]4− octahedral tilt modifies the perovskite crystallographic properties in γ‐CsPbI3, leading to alterations in its bandgap and crystal strain. In addition, by substituting amorphous barium titanium oxide (a‐BaTiO3) for TiO2 as the electron transport layer, interfacial defects caused by imperfect energy levels between the electron transport layer and perovskite are reduced. High‐resolution transmission electron microscopy and electron energy loss spectroscopy demonstrate that a‐BaTiO3 forms entirely as a single phase, as opposed to Ba‐doped TiO2 hybrid nanoclusters or separate domains of TiO2 and BaTiO3 phases. Accordingly, inorganic perovskite solar cells based on the a‐BaTiO3 electron transport layer achieved a power conversion efficiency of 19.96%.

СОРБЦИОННАЯ СПОСОБНОСТЬ СЛОИСТЫХ ДВОЙНЫХ ГИДРОКСИДОВ Mg-Al ПО ОТНОШЕНИЮ К ИОНАМ Co (II), Cu (II), Sr (II) и Cs (I)

Mg-Al layered double hydroxides with a hydrotalcite structure have been synthesized. The sorption properties of the synthesized sample with respect to non-ferrous metal ions — Co2+, Cu2+, Sr2+ and Cs+ are investigated. The capacities of the adsorption monolayer of the Mg-Al layered hydroxide sample were calculated, amounting to 2.13, 2.21, 1.88 and 3.48 mmol/g with respect to Co(II), Cu(II), Sr(II) and Cs(I) ions, respectively. It is shown that the sorption process is described by a pseudo-second-order kinetic model and proceeds in a mixed diffusion mode.

Performance of molybdenum vanadate loaded on bentonite for retention of cesium-134 from aqueous solutions

This article studied the sorption behavior of Cs(I) ions from aqueous solutions onto molybdenum vanadate@bentonite (MoV@bentonite) composite. MoV@bentonite has been fabricated using the precipitation method and was characterized by different analytical tools including, FT-IR, XRD, and SEM attached with an EDX unit. The sorption studies applied on Cs(I) ions include the effect of contact time, pH, initial metal concentrations, ionic strength, desorption, and recycling. The experimental results revealed that in the adsorption process carried out after equilibrium time (300 min), saturation capacity has a value of 26.72 mg·g−1 and the sorption of Cs(I) ions is dependent on pH values and ionic strength. Sorption kinetic better fit with the pseudo-second-order model; sorption isotherms apply to Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. Data of thermodynamic parameters indicate that sorption is spontaneous and endothermic. Recycling experiments show that MoV@bentonite could be used for 7 cycles and the best eluant for the recovery of Cs(I) ions is 0.1 M HCl (76.9%). All the obtained data clarify that MoV@bentonite is considered a promising sorbent for the sorption of Cs(I) ions from aqueous solutions.

Equilibrium and Kinetic Characteristics of the Sorption of Co(II), Cu(II), Sr(II), and Cs(I) Ions on Layered Mg–Al Double Hydroxides

Equilibrium and Kinetic Characteristics of the Sorption of Co(II), Cu(II), Sr(II), and Cs(I) Ions on Layered Mg–Al Double Hydroxides

Unraveling the effect of CDI electrode characteristics on Cs removal from the perspective of ion transfer and energy composition

Capacitive deionization (CDI) is surprisingly efficient to remove the aqueous Cs ion due to its small hydrated size and low hydration energy. But current experimental techniques fail in investigating deeply into the influence of some key electrode characteristics due to the difficulty in experimentally fabricating the electrodes as desired. This work presents a dynamic transport model of salt ions in a flow-by CDI cell. By using this model, the electrode thickness, macro- and micro-porosity are investigated to evaluate Cs ion removal efficiency and energy efficiency particularly from the aspect of ion transfer by the approach of decomposing energy contribution. The results indicate that the thick electrode coupled with the high current could greatly improve the effluent quality, but reduce the salt adsorption capacity (SAC). The increasement of the current density from 3 A/m2 to 6 A/m2 greatly decreases the SAC from 4.0 mg/g to 0.8 mg/g. Lower current could prolong the charging period, leading to more ions stored in the micropore. Not all the electrical energy is consumed for separating ions from the feed as desired, but some are used for driving ions diffusing in the electrodes. Consequently charging efficiency will be reduced especially when the electrodes are characterized with high porosity. It is highlighted that future work is required to further consider the complex details of porous structure and pore connectivity.

Direct Separation of UO2 2+ by Coordination Sieve Effect via Spherical Coordination Traps.

Molecule sieve effect (MSE) can enable direct separation of target, thus overcoming two major scientific and industrial separation problems in traditional separation, coadsorption, and desorption. Inspired by this, herein, the concept of coordination sieve effect (CSE) for direct separation of UO2 2+ , different from the previously established two-step separation method, adsorption plus desorption is reported. The used adsorbent, polyhedron-based hydrogen-bond framework (P-HOF-1), made from a metal-organic framework (MOF) precursor through a two-step postmodification approach, afforded high uptake capacity (close to theoretical value) towards monovalent Cs+ , divalent Sr2+ , trivalent Eu3+ , and tetravalent Th4+ ions, but completely excluded UO2 2+ ion, suggesting excellent CSE. Direct separation of UO2 2+ can be achieved from a mixed solution containing Cs+ , Sr2+ , Eu3+ , Th4+ , and UO2 2+ ions, giving >99.9% removal efficiency for Cs+ , Sr2+ , Eu3+ , and Th4+ ions, but <1.2% removal efficiency for UO2 2+ , affording benchmark reverse selectivity (SM/U ) of >83 and direct generation of high purity UO2 2+ (>99.9%). The mechanism for such direct separation via CSE, as unveiled by both single crystal X-ray diffraction and density-functional theory (DFT) calculation, is due to the spherical coordination trap in P-HOF-1 that can exactly accommodate the spherical coordination ions of Cs+ , Sr2+ , Eu3+ , and Th4+ , but excludes the planar coordination UO2 2+ ion.