Two-dimensional assembly made up of ZIF-8 particles for the high-efficient capture of the iodine and dyes

Green conversion of waste alkaline battery material to zeolitic imidazolate framework-8 and its iodine capture mechanism

Zeolitic imidazolate framework-8 (ZIF-8) exhibits excellent performance in capturing iodine. However, the solvent-based procedures and raw materials for ZIF-8 synthesis often lead to secondary pollution. We developed a solvent-minimizing method for preparing ZIF-8 via ball milling of raw material obtained from spent alkaline batteries, and studied its iodine-capture performance and structural changes. Exposure of the ZIF-8 to iodine vapor for 60 min demonstrated that it exhibited industrially competitive iodine-capture performance (the adsorbed amount reaches to 1123 mg g-1 within 60 min). Spectroscopic studies showed that ZIF-8 underwent a structural transformation upon iodine loading. Iodine molecules were adsorbed onto the surface of ZIF-8 and also formed C-I bond with the methyl groups on the imidazole rings, reducing iodine release. This work represents a comprehensive revelation of long-range order and short-range order evolution of ZIF-8 during iodine vapor adsorption over time. Moreover, this green synthesis of ZIF-8 is of lower cost and generates fewer harmful by-products than existing methods, and the produced ZIF-8 effectively entraps toxic iodine vapor. Thus, this synthesis enables a sustainable and circular material flow for beneficial utilization of waste materials.

Ultrafast Synthesis of Graphene-Embedded Cyclodextrin-Metal-Organic Framework for Supramolecular Selective Absorbency and Supercapacitor Performance

Limited by preparation time and ligand solubility, synthetic protocols for cyclodextrin-based metal-organic framework (CD-MOF), as well as subsequent derived materials with improved stability and properties, still remains a challenge. Herein, an ultrafast, environmentally friendly, and cost-effective microwave method is proposed, which is induced by graphene oxide (GO) to design CD-MOF/GOs. This applicable technique can control the crystal size of CD-MOFs from macro- to nanocrystals. CD-MOF/GOs are investigated as a new type of supramolecular adsorbent. It can selectively adsorb the dye molecule methylene green (MG) owing to the synergistic effect between the hydrophobic nanocavity of CDs, and the abundant O-containing functional groups of GO in the composites. Following high temperature calcination, the resulting N, S co-doped porous carbons derived from CD-MOF/GOs exhibit a high capacitance of 501 F g-1 at 0.5 A g-1 , as well as stable cycling stability with 90.1% capacity retention after 5000 cycles. The porous carbon exhibits good electrochemical performance due to its porous surface containing numerous electrochemically active sites after dye adsorption and carbonization. The design strategy by supramolecular incorporating a variety of active molecules into CD-MOFs optimizes the properties of their derived materials, furthering development toward the fabrication of zeitgeisty and high-performance energy storage devices.

Fabrication of bimetallic-doped materials derived from a Cu-based complex for enhanced dye adsorption and iodine capture

In this work, we used Cu(II) ions, a bis-pyridyl-bis-amide ligand [N,N'-bis(4-pyridinecarboxamide)-1,2-cyclohexane (4-bpah)], and an aromatic dicarboxylic acid [1,4-cyclohexanedicarboxylic acid (H2CHDA)] to construct a 1D binuclear Cu-based complex, namely {[Cu3(4-bpah)(CHDA)3(H2O)]·2H2O}n (1). Moreover, we also developed a facile method to synthesize two monometallic/bimetallic-doped materials which were derived from the Cu complex (C-N-1 and C-V-1, which were doped with nitrogen and vanadium, respectively). The as-synthesized derived materials were fully characterized and the iodine sorption/release capabilities were investigated in detail. We performed iodine adsorption experiments on the two monometallic/bimetallic-doped materials and found that C-N-1 and C-V-1 possess highly efficient adsorption activities for the adsorption of iodine from solution. The C-N-1 and C-V-1 complexes exhibited remarkable adsorption capacities of 1141.60 and 1170.70 mg g-1, respectively, for iodine from a cyclohexane solution. Moreover, the dye adsorption properties of C-N-1 and C-V-1 were also investigated in detail. The obtained C-N-1 and C-V-1 exhibit effective dye uptake performances in water solution. The adsorption of Congo red (CR) on a single metal carbon material C-N-1 doped with heteroatoms reached equilibrium within 240 min and reached an adsorption capacity of 1357.00 mg g-1 and the adsorption capacities of C-V-1 for methylene blue (MB), gentian violet (GV), rhodamine B (RhB), and CR at room temperature were found to be 187.60, 190.60 and 108.10 and 1501.00 mg g-1 in 180 min, respectively. By comparison, we found that doping vanadium could play an important role in the adsorption processes. The adsorption capacity of C-V-1 (containing the vanadium in its structure) was relatively higher than that of C-N-1, which indicated that the introduction of non-noble metals may effectively tune the adsorption kinetics activity and the introduction of noble metals can change the surface electronegativity of porous carbon materials, thus leading to significantly improved adsorption capabilities.

Tesla valve-assisted biosensor for dual-mode and dual-target simultaneous determination of foodborne pathogens based on phage/DNAzyme co-modified zeolitic imidazolate framework-encoded probes

Sensitive and accurate detection of multiplex foodborne pathogens is crucial for food safety. In this work, a dual-mode and dual-target biosensor regulated by a Tesla valve was established for simultaneously determining Escherichia coli O157:H7 (E. coli) and Salmonella typhimurium (S. T). Two zeolitic imidazolate framework (ZIF-8) signal probes decorated with electroactive materials (ferrocene or methylene blue), DNAzyme, and different phages were synthesized to specifically recognize the targets and generate fluorescent/electrochemical dual-mode signals. In the presence of bacteria, they were captured and enriched on two individual working electrodes through the modified 4-mercaptophenylboric acid. The encoded signal probes added on different working electrodes could be conjugated with the corresponding target bacteria depending on the specificity of phages. Under the acidic condition, the DNAzyme could catalyze click chemistry for fluorescent signals. Simultaneously, the released ferrocene and methylene blue from ZIF-8 could generate electrochemical signals at different potentials. Benefiting from the flow regulation feature of the Tesla valve, the triggered fluorescent and electrochemical signals in the two individual electrodes would not influence each other, achieving simultaneous dual-mode and dual-target determination of foodborne pathogens. It depicted good linearity ranged 10-10⁷ CFU mL^-1. And the corresponding detection of limits were 5 CFU mL^-1 and 8 CFU mL^-1 for two bacteria, respectively. A low false positive was realized through the dual-mode strategy. The proposed biosensor can not only on-site, specifically, and sensitively determine E. coli and S. T, but also provide the wide prospect in rapid screening of other foodborne pathogens.

Facile synthesis of ZIF-8-lignosulfonate microspheres with ultra-high adsorption capacity for Congo red and tetracycline removal from water

Zeolitic imidazolate frameworks (ZIFs) can be used as adsorbent to efficiently adsorb organic pollutants. However, the hydrophobicity of the ZIFs may be easily to form ZIFs nanoparticles aggregates, hampering the effective and practical application in adsorption. In this study, novel spherical composites of ZIF-8 incorporated with lignosulfonate (LS) were synthesized by in-situ growth method. The effects of different mass ratios of LS and Zn in ZIF-8-LS composites were evaluated with respect to structural characteristics and adsorption properties. As an adsorbent for adsorptive removing Congo Red (CR) and tetracycline (TC) from water, the prepared ZIF-8-LS₄ shows the best adsorption capacity of 31.5 mg g^-1 and 48 mg g^-1, respectively. The spherical structure facilitates the contact between the ZIF-8 and the adsorbed substance, in addition to the H-bonding, electrostatic and π-π stacking interactions also contribute to the improvement of the adsorption performance of the ZIF-8-LS₄ composite. The outstanding adsorption capacity and good reusability of the ZIF-8-LS₄ composite provide a good prospect for the effective removal of other contaminants from water.

Highly efficient iodine capture and ultrafast fluorescent detection of heavy metals using PANI/LDH@CNT nanocomposite

Here, the hybrid material of polyaniline/layered double hydroxide@carbonnanotubes (PANI/LDH@CNT) is considered a multifunctional material. Instrumental methods, including FTIR, XRD, TEM, SEM, and TGA/DTA were utilized to characterize PANI/LDH@CNT. The polymerization method created PANI/LDH@CNT as an adsorbent to remove toxic iodine in hexane solution with a capture capacity of 303.20 mg g^-1 during 9 h. It is 900 mg g^-1 in the vapor phase within 24 h. After three cycles, the PANI/LDH@CNT could be regenerated while maintaining 91.90 % iodine adsorption efficiency. Due to the presence of free amine (-N) groups, OH^-, CO₂H, and π-π conjugated structures in the PANI/LDH@CNT, it is also explored for efficient iodine uptake. It was demonstrated that the pseudo-first-order (PFO) and Langmuir model had the optimum correlation with the kinetic and isotherm data, respectively. Moreover, the use of PANI/LDH@CNT is not only limited to iodine capture; it can also be utilized as a sensitive sensor that displays a fluorescence "turn-off" response for Mn⁷⁺ and Cr⁶⁺ ions and a fluorescence "turn-on" response in the case of Al³⁺ ions. The fluorescence intensity of the PANI/LDH@CNT was turned off in the presence of Mn⁷⁺ and Cr⁶⁺ because of the fluorescence inner filter effect (IFE) mechanism. In contrast, the fluorescence intensity was turned on in the case of Al³⁺, relying on the chelation-enhanced fluorescence (CHEF) effect mechanism. Under optimal conditions, the limit of detection (LOD) of 51, 59, and 81 nM for Mn⁷⁺, Cr^6+, and Al³⁺, respectively. According to the literature, this is probably the first example based on PANI/LDH@CNT as a multifunctional hybrid material employed as an adsorbent for capturing radioactive iodine and as a chemosensor for detecting heavy metal ions in aqueous solutions.

Simultaneous mitigation of arsenic and cadmium accumulation in rice grains by foliar inhibitor with ZIF-8@Ge-132

Simultaneous mitigation of Arsenic (As) and Cadmium (Cd) in rice grains is hardly achieved with conventional soil treatments due to their opposite chemical behaviors in paddy soils. This study evaluates the effectiveness of a novel foliar inhibitor with germanium (Ge) -modified zeolitic imidazolate framework (ZIF-8@Ge-132) in cooperative mitigation of As and Cd in rice grains in a As and Cd co-contaminated paddy field, and the effecting mechanisms are elucidated by a series of advanced techniques. The results showed that the grains inorganic As and Cd was remarkably decreased by 45 % and 66 % by the foliar spay of ZIF-8@Ge-132, respectively. ZIF-8@Ge-132 also reduced the As and Cd contents in rice tissues, except for Cd in leaves, where Cd content increased by 148 %. The image-based measurement of plant phenotypic traits and the elements of image analysis using Laser Ablation-ICP-MS (LA-ICP-MS) and Laser Scanning Confocal Microscopy (LSCM) revealed that the possible mechanisms for the reduction of As and Cd in rice grains were as follows: (i) the thickening of the xylem in roots significantly retarded As and Cd absorption by rice plants. (ii) co-accumulation of Ge and Cd in the leaf vascular system likely contributed to the high Cd retention in rice leaves. (iii) antagonistic effects of Zn suppressed the uptake and transport of As in roots/leaves, resulting a lower As accumulation in rice grains.

Two Facile Aniline-Based Hypercrosslinked Polymer Adsorbents for Highly Efficient Iodine Capture and Removal

Effective capture and safe disposal of radioactive iodine (¹²⁹I or ¹³¹I) during nuclear power generation processes have always been a worldwide environmental concern. Low-cost and high-efficiency iodine removal materials are urgently needed. In this study, we synthesized two aniline-based hypercrosslinked polymers (AHCPs), AHCP-1 and AHCP-2, for iodine capture in both aqueous and gaseous phases. They are obtained by aniline polymerization through Friedel-Crafts alkylation and Scholl coupling reaction, respectively, with high chemical and thermal stability. Notably, AHCP-1 exhibits record-high static iodine adsorption (250 wt%) in aqueous solution. In the iodine vapor adsorption, AHCP-2 presents an excellent total iodine capture (596 wt%), surpassing the most reported amorphous polymer adsorbents. The rich primary amine groups of AHCPs promote the rapid physical capture of iodine from iodine water and iodine vapor. Intrinsic features such as low-cost preparation, good recyclability, as well as excellent performance in iodine capture indicate that the AHCPs can be used as potential candidates for the removal of iodine from radioactive wastewater and gas mixtures.