A Two-dimensional Covalent Organic Framework for Iodine Adsorption

Radioactive iodine is a notorious pollutant in gas radioactive nuclear waste due to its radiation hazard, volatility, chemical toxicity, and high mobility. Therefore, developing a material with high efficiency-specific iodine capture is significant. Covalent organic framework(COF) has attracted significant attention as a new crystalline porous organic material. Due to its large specific surface and high chemical stability, it is an excellent alternative to adsorbents. Herein, we report a chemically stable two-dimensional COF(termed JUC-609) with specific adsorption of iodine. Adsorption experiments show that JUC-609 has an excellent iodine adsorption capacity as high as 5.9 g/g under 353 K and normal pressure condition, and iodine adsorption after multiple cycles is still maintained. Our study thus promotes the potential application of COFs in the field of environment-related applications.

Iodine Adsorption Studies of Dipalladium-based Supramolecular Cages

Four water-soluble cage-like hosts(1·4NO3^(-)_(2):{[(bpy)_(2)Pd_(2)]_(2)L^(1)_(2)}(NO_(3))_(4),2·4NO3^(-)_(2):{[(bpy)_(2)Pd_(2)]_(2)L^(2)_(2)}(NO_(3))_(4),3·6NO3^(-)_(2):{[(bpy)_(2)Pd_(2)]_(3)L^(3)_(2)}(NO_(3))_(6)and 4·6NO3^(-)_(2):{[(bpy)_(2)Pd_(2)]_(3)L^(4)_(2)}(NO_(3))_(6)have been successfully self-assembled by coordinating the flexible amide based polypyrazole ligands(H_(2)L^(1):N^(1),N^(4)-di(lH-pyrazol-5-yl)terephthalamide,H_(2)L^(2):N^(1),N^(4)-bis(3-methyl-1H-pyrazol-5-yl)-terephthalamide,H_(3)L^(4):N^(1),N^(3),N^(5)-tri(1H-pyrazol-5-yl)benzene-1,3,5-tricarboxamide and H^(3)L^(4):N^(1),N^(3),N^(5)-tris(3-methyl-lH-pyrazol-5-yl)benzene-1,3,5-tricarboxamide)with dipalladium comers([(bpy)_(2)Pd_(2)(N0_(3))_(2)](N0_(3))_(2),where bpy=2,2'-bipyridine)in aqueous solution.Their structures were characterized by^(1)H NMR,ESI-MS and single-crystal X-ray diffraction.Notably,all the four supramolecular assemblies are capable of adsorbing iodine molecules via halogen bonds and other supramolecular interactions.

A tetraaldehyde-derived porous organic cage and covalent organic frameworks:Syntheses,structures,and iodine vapor capture

Dynamic covalent imine reactions between 2,3-dimethoxy-[1,1:4,1-terphenyl]-3,3,5,5-tetracarbaldehyde(DMTT)and cyclohexanediamine,p-phenylenediamine,and benzidine,respectively,generate a porous organic cage(DMPOC)and two covalent organic frameworks(COFs),USTB-29,and USTB-30.DMPOC shows a[3+6]topological cage-like structure according to single crystal X-ray diffraction result.In contrast,both microcrystalline USTB-29 and USTB-30 exhibit two-dimensional monoporous structures in an eclipsed AA stacking style based on powder X-ray diffraction and theoretical simulations.In addition,DMPOC is capable of efficiently absorbing the iodine vapor with an outstanding uptake of 5.10 g/g,much higher than that of USTB-29(3.07 g/g)and USTB-30(3.16 g/g).Cage to COFs transformations have been realized from DMPOC to USTB-29 and USTB-30 via the imine bond exchange with slightly increased iodine vapor uptake.Mechanism investigations uncover that both nitrogen and oxygen atoms of POC and COFs contribute to iodine vapor capture due to the formation of charge transfer matter,and loose interaction introducing adaptive expanding voids of DMPOC is suggested to capture more iodine vapor than that of COFs with strongπ-πinteractions.

Phenolic Based Porous Carbon Fibers with Superior Surface Area and Adsorption Efficiency for Radioactive Protection

Radioactive iodine element mainly in CH3I is a key fission product of concern in the nuclear fuel cycle,which directly threat-ens human health if released into the environment.Effective capture of the I element is essential for human health protection.The iodine filter,consisting of an activated carbon inner core and cotton filter,is the most common radioactive iodine pro-tection product.Currently,the activated carbon inside the iodine filter suffers from the weak adsorption efficiency and high cost.Herein,a process based on a strong alkali activation method was developed to significantly improve iodine absorption and reduce the cost.A series of flexible porous carbon fibers with a high specific surface area(up to about 1,500~2,200 m^(2)/g)were prepared by carbonation of the phenolic resin fibers(PF,prepared through melt spinning and crosslink)followed by activation via KOH treatment.Meanwhile,the nitrogen-doped sp^(2)-heterogeneous carbon atoms were prepared by add-ing nitrogen sources such as urea which led to a high surface area nano-porous fibers with an average pore size of~2.4 nm.The nitrogen-doped porous carbon fibers exhibit very high adsorption for liquid iodine and iodine vapor.The liquid iodine adsorption capacity of nitrogen-doped porous carbon NDAC-4 prepared under 800°C reaches 2,120 mg/g,which is 2.1 times higher than that of the commercial iodine filter,and for iodine vapor the capacity can reach 5,330 mg/g.Meanwhile,the CH_(3)I adsorption capacity is 510 mg/g,which is 3.4 times higher than that of commercial unmodified viscose fibers and has greater stability and circularity.Importantly,the research has met the requirements of industrial production,and the fabrication of phenolic-fibers-based protection equipment can be widely used in the nuclear radiation industry.

A cationic nanotubular metal-organic framework for the removal of Cr_(2)O_(7)^(2-) and iodine

In this work,two new metal-organic frameworks(MOFs)based on a pyrazole-imidazole heterotopic ligand,namely,SCNU-Z8(Co)and SCNU-Z8(Ni),are constructed.They are isostructural,and the crystal structure of SCNU-Z8(Co)is further analyzed by single-crystal X-ray diffraction.They are 3D cationic frameworks with 1D tubular channels and possess a highly(3,9)-connected binodal gfy network topology.SCNU-Z8(Ni)can be syn-thesized in high yield with high phase purity;thus,it is selected to be further explored.A stability study shows that its framework is stable in water at different pH values and in many organic solvents.It can be applied to capture Cr_(2)O_(7)^(2-)anions in water with a moderate adsorption capacity of 130 mg/g via anion-exchanged process.Iodine molecules in vapour phase and cyclohexane solution can also be captured by SCNU-Z8(Ni).In the case of iodine vapours and iodine cyclohexane solution,the adsorption capacity reaches up to 4.1 g/g and 640 mg/g,respectively,which are among the best in MOFs.Most of the absorbed iodine molecules are stably captured in the framework and hard to release,which may be conducive to allow the permanent storage of radioactive iodine.

Experimental and theoretical insights into copper phthalocyanine-based covalent organic frameworks for highly efficien radioactive iodine capture

Exploring efficient materials for capturing radioactive iodine in nuclear waste is of great significance for the progress of nuclear energy as well as the protection of ecological environment.Covalent organic frameworks(COFs)have emerged as promising adsorbents because of their predesignable and functionalizable skeleton structures.However,it remains a grand challenge to achieve large scale preparation of COFs.In this work,we developed a mild and efficient microwave irradiation method instead of the traditional solvothermal method to prepare copper phthalocyanine-based covalent organic frameworks(Cu_(x)Pc-COFs)within only 15 min.The nitrogen-rich 1,2,4,5-tetracarbonitrilebenzene(TCNB)was selected as the solely organic ligand to construct copper phthalocyanine-based 2D conjugated COFs.The resultant Cu_(x)Pc-COFs exhibited excellent iodine enrichment with 2.99 g/g for volatile iodine and 492.27 mg/g for iodine-cyclohexane solution,respectively,outperforming that of many porous materials.As indicated by spectroscopic analysis and DFT calculations,this impressive adsorption performance can be attributed to the charge transfer arising from nitrogen-rich phthalocyanine structures and electron-richπ-conjugated systems with iodine molecules.Moreover,the strong electrostatic interaction between Cu(Ⅱ)on chelate centers and polyiodide anions(I_(x)^(-))also play an important role in the firmly trapping radioactive iodine.Therefore,this study provides a facile and intelligent approach to implement metal-based COFs for the remediation of toxic radioactive iodine.

Face-directed Strategy for the Construction of Polyoxovanadate-based Metal-Organic Tetrahedra

Polyoxometalate-based metal-organic polyhedra(MOPs)were of particular concern because of the various exquisite building blocks and the suitable constructional characteristics.To further understand the design and particularity of polyoxovanadate-based MOPs,(NH_(2)Me)_(8){[V_(6)O_(6)(OCH_(3))_(9)(C_(6)H_(5)PO_(3))]_(4)·(BPT)_(4)}·2DMF(HNU-74)and(NH_(2)Me)12{[V_(6)O_(6)(OCH_(3))_(9)(C_(6)H_(5)PO_(3))]4·(HBCBAIP)_(4)}(SO_(4))_(2)·MeOH·DMF(HNU-75)were constructed by a face-directed synthesis strategy.Both structures were assembled with four secondary building units as vertexes and four organic ligands served as faces.Different from HNU-74,HNU-75 showed a carboxyl group free during the coordination process,resulting in the pore channels being blocked and the free carboxyl group linking outwards,paving the way for the formation of the 3D structure.Due to the pore channels of HNU-74,the adsorption of I2 was studied and the adsorption capacity was 148 mg/g.