Synthesis,Crystal Structure and Iodine Capture of a Yttrium(Ⅲ) Coordination Polymer with 5-Aminonicotinic Acid

A new coordination polymer, [（C（18）H（16）N4O（18）Y2）（H2O）]n, has been hydrothermally synthesized by reacting yttrium（Ⅲ） nitrate with 5-aminonicotinic acid and ammonium oxalate at a molar ratio of 1：1：1, and its structure was determined by X-ray crystallography with the following data： monoclinic system, space group C2/c, a = 13.4507（10）, b = 11.5829（9）, c = 16.3448（9） ？, a= 89.983（6）, β = 109.056（6）, g = 90.047（6）°, Z = 4, V = 2406.92（14） ？~3, F（000） = 1536, Dc = 2.13079 g/cm^3, R = 0.0284（1695） and w R = 0.0787（2014）. In the asymmetric unit of the compound, each Y（Ⅲ） ion is bonded to eight oxygen atoms from 5-aminonicotinic acid and oxalate groups and terminal-coordinated water molecule, resembling a highly distorted tricapped trigonal geometry. Adjacent three yttrium atoms are bridged by three identically independent oxalate groups in a side-by-side manner to form brickwall-like 2D sheets, and these sheets are further linked through π-π stacking interactions to generate a 3D supramolecular network. The photoluminescent property of the complex was investigated and the iodine capture studies show that the porous frameworks have reversible absorption ability for iodine molecule.

Cation-π and electrostatic interactions co-driven assembly of two-dimensional heteropore supramolecular polymers with rapid iodine capture capability

Constructing two-dimensional(2D)supramolecular polymers with complicated hierarchical porosity significantly contributes to developing effective strategies to control delicate self-assembly architectures,thus facilitating the fabrication of advanced 2D organic functional materials.Here,we report utilizing cooperative cation-πand electrostatic interactions to construct a series of robust 2D heteropore supramolecular polymers(2D HPSPs)with hierarchical pore structures,in which hexagonal and rectangular pores are alternately and periodically arranged,and the pore sizes can be finely tuned.Remarkably,the as-prepared 2D HPSPs exhibit excellent iodine(I_(2))capture rate(a maximum K80%value is 2.25 g h^(-1)),and present a novel mechanism involving transport-adsorption spatiotemporal separation for rapid I_(2)capture.In this mechanism,the transport of free I_(2)is first conducted in large hexagonal pores,and then I_(2)can be preferentially adsorbed in small rectangular pores,thereby preventing the transfer channels from blocking and greatly improving the adsorption kinetics.

A large-scale screening of metal-organic frameworks for iodine capture combining molecular simulation and machine learning

We performed large-scale molecular simulation to screen and identify metal-organic framework materials for gaseous iodine capture,as part of our ongoing effort in addressing management and handling issues of various radionuclides in the grand scheme of spent nuclear fuel reprocessing.Starting from the computation-ready experimental(CoRE)metal-organic frameworks(MOFs)database,grand canonical Monte Carlo simulation was employed to predict the iodine uptake values of the MOFs.A ranking list of MOFs based on their iodine uptake capabilities was generated,with the Top 10 candidates identified and their respective adsorption sites visualized.Subsequently,machine learning was used to establish structure-property relationships to correlate MOFs’various structural and chemical features with their corresponding performances in iodine capture,yielding interpretable common features and design rules for viable MOF adsorbents.The research strategy and framework of the present study could aid the development of high-performing MOF adsorbents for capture and recovery of radioactive iodine,and moreover,other volatile environmentally hazardous species.

A Two-dimensional Dual-pore Covalent Organic Framework for Efficient Iodine Capture

Effectively capturing volatile radioiodine generated during the nuclear fission process is considered to be a safe way to the utilization of nuclear power. Here we report a new two-dimensional covalent organic framework(2D COF), ETTA-PyTTA-COF, as a highly efficient iodine adsorbent, which is constructed through the condensation reaction between 4,4’,4’’,4’’’-(ethene-1,1,2,2-tetrayl)-tetrabenzaldehyde(ETTA) and 1,3,6,8-tetrakis(4-aminophenyl)pyrene(PyTTA). The ETTA-PyTTA-COF possesses a permanent 1D channel porous structure with a high Brunauer-Emmet-Teller(BET) surface area of 1519 m2/g and excellent chemical and thermal stability. It shows ultrahigh iodine adsorption capability, which can reach up to 4.6 g/g in vapor owing to its high BET surface area, large π-conjugated structure and plenty of imine groups in the skeleton of the COF as effective iodine sorption sites.

Efficient gaseous iodine capture enhanced by charge-induced effect of covalent organic frameworks with dense tertiary-amine nodes

Based on the outstanding application advantages of nitrogen-rich materials with regular porous frameworks in the capture of gaseous radioactive iodine,a series of covalent organic frameworks(COFs)with dual channels and abundant tertiary-amine active sites were constructed herein via a unique multinitrogen node design.The high density of up-to-six nitrogen adsorption sites in a single structural unit of the products effectively improved the adsorption capacities of the materials for iodine.Moreover,the adsorption affinity of the active sites can be further regulated by charge-induced effect of different electrondonating groups introduced into the COFs.Adsorption experiments combined with DFT theoretical calculations confirmed that the introduction of electron-donating groups can effectively increase the electron density around the active sites and enhance the binding energy between the materials and iodine,and thus improve the iodine adsorption capacity to 5.54 g/g.The construction strategy of multi-nitrogen node and charge-induced effect proposed in this study provides an important guidance for the study of the structure-activity relationship of functional materials and the design and preparation of high-performance iodine adsorption materials.

Construction of Tetrathiafulvalene-based Covalent Organic Frameworks for Superior Iodine Capture

The effective capture of radioiodine species during nuclear fuel reprocessing and nuclear accidents is of primary importance but remains challenging for the sustainable development of nuclear energy.Herein,we report two newly designed two-dimensional(2D)and three-dimensional(3D)covalent organic frameworks by introducing tetrathiafulvalene functional groups into the building units for the simultaneous physisorption and chemisorption capture of iodine molecules.Remarkably,the obtained 3D TTF-TAPT-COF material exhibited a superior iodine vapor adsorption capacity of up to 5.02 g/g at 348 K and under ambient pressure and an adsorption kinetics of 0.515 g/(g∙h),surpassing most of other materials reported so far.The strong physiochemical interactions between iodine molecules and the frameworks of the obtained COFs were revealed by a set of experimental techniques.This study provides a feasible approach for the rational design and the construction of novel and effective COF-based adsorbents for iodine enrichment and related environmental remediation.

Efficient capture of iodine and methyl iodide using all-silica EMM-17 zeolite

Hydrophobic zeolites have been identified as suitable adsorbents for capturing radioactive iodine species from nuclear-powerplant off-gas because of their high stability and strong water resistance.However,only the most common zeolites have been investigated for the capture of molecular iodine to date.Herein,we demonstrate that the composition and pore structure of zeolites considerably affect their iodine adsorption performance.A novel all-silica ExxonMobil material-17(EMM-17)zeolite having a unique three-dimensional 10(12)×10(12)×11-ring channel system exhibits a high adsorption capacity for iodine and methyl iodide in the presence of water.EMM-17 outperforms previously reported zeolites in terms of gravimetric and volumetric adsorption capacity in dynamic adsorption measurements.The excellent iodine/methyl iodide capture properties are attributed to the combination of optimal pore size,high pore volume,strong hydrophobicity,suitable particle morphology.This study provides useful insights for designing efficient adsorbents for iodine capture.

Flake channels construction of hydroxyapatite/gelatin cryogel with excellent flame retardant properties for enhancing the capturing of iodine

Safe and efficient capturing of volatile radioiodine is of extremely important significance in the treatment of spent fuel.Herein,the flake channels in gelatin-hydroxyapatite(HAP@Ge)cryogel with excellent flame retardant properties were constructed by immobilizing hydroxyapatite nanorods(HAP)on Gelatin(Ge)cryogel for enhancing the capturing of iodine.The immobilization of HAP nanorods enhanced thermal stability,provided low rates of dynamic heat transfer and dissipation,and remarkably improved the flame retardant and smoke suppression properties of the Ge cryogel,which can effectively prevent the occurrence of safety incidents caused by further thermal degradation or combustion of this cryogel.More importantly,it was effective in improving the rapid enrichment of iodine,resulting in a high adsorption capacity.The maximum adsorption capacity of HAP@Ge cryogel for iodine vapor reached 2693 mg/g at equilibrium.The high adsorption capacity for iodine was attributed to the multi-scale porous structure in HAP@Ge cryogel,which offered effective channels for iodine diffusion,whereas the numerous complex and irregular flakes provided sufficient number of active sites for iodine capture.The adsorption process was chemical in nature and involved the-PO_(4)^(3-),-OH,-C=O,and-NHR groups on HAP@Ge cryogel.Moreover,the complex porous structure of HAP@Ge cryogel enhanced the physical capturing of iodine.These advantages,such as low-cost raw material,simple preparation method,good flame retardancy,and excellent capturing performance for iodine indicated that HAP@Ge cryogel is a potential candidate for the removal of radioactive iodine in the exhaust gas stream of post-treatment plants.

Loading single lanthanide ion into aluminum molecular rings:water-stable sodalite cage for removal of nuclear-industry anions

Based on our discovery of neutral aluminum molecular rings,we herein introduce rare earth ions into the center of the ring and reveal their structural adaptability.The resulting yoyo-like cationic macrocycles are highly adaptive to guests,creating unusual supramolecular assemblies.The first category is stacked with singly oriented rhombohedral channels,which exhibit fast and reversible solvent-triggered molecular motions and structural rearrangements.The second type of assembly is that yoyo macrocycles and guest molecules form a nested host-guest sodalite cage supramolecular structure.It is uncommon for guest molecules to be well-defined within cages although caged structures have been well-documented.Their host-guest interaction discussion reveals the self-adaptation and flexibility of the yoyo macrocycles.Considering their good water stability,we investigated their anion exchange properties.The results show that they have significant exchange capacity for KI/I_(2),ReO_(4)^(-),and MnO_(4)^(-),revealing their potential application in water purification and nuclear waste treatment.

Hexnut[12]arene and its derivatives: Synthesis, host-guest properties, and application as nonporous adaptive crystals

Hexnut[12]arene(HN[12])and its derivatives,a new class of sixfold macrocyclic arenes,were designed and synthesized in reasonable yield by a one-pot reaction at room temperature using dimethoxymethane as a methylene source.HN[12],which bears a large,symmetric,and rigid cavity,was easily functionalized at both the methylene bridges and the hydroquinone units.A water-soluble fluorescent HN[12]was synthesized and used as a host to encapsulate benzyl viologen dichloride in water with a high binding affinity of(3.4±0.2)×10^(6)M^(-1).The nonporous adaptive crystal(NAC)of HN[12]was found to capture not only inorganic molecules(iodine)but also trace amounts of large organic molecules(basic fuchsine)from water,which greatly expands the scope of NACs for adsorption.