Anion Selectivity Research Articles

New method for electrochemical ion separation (ElONS) for chloride/nitrate separation using Ag/AgCl electrodes with a cation exchange membrane

Electrochemical ion separation (EIONS) is attracting attention as a new ion separation technology because no by-products are generated during the process. However, conventional EIONS systems have lower selectivity for anions; it has limitations in its application to selective anion extraction. Therefore, it is necessary to develop a new EIONS system with high selectivity for specific anions. In this study, we introduce a highly selective EIONS for Cl- extraction from a mixed solution of Cl- and NO3- using silver/silver-chloride electrodes with a cation exchange membrane. This technique is based on the principle that Ag/AgCl electrodes starts to react with Cl- at a specific potential to remove Cl- from the mixture. As a result, this system removed Cl- with 80 times higher selectivity than its removal of NO3- even at the low cell voltage of 0.3 V. Furthermore, it was found that this system could be operated at a current density as high as 5 mA cm−2, suggesting for rapid extraction. We believe that this system can be feasible for separating Cl- and NO3- electrochemically.

Determination of a comprehensive set of drugs of abuse, metabolites and human biomarkers in wastewater using passive sampling followed by UHPLC-MS/MS analysis

Passive sampling of wastewater using polar organic chemical integrative samplers (POCIS) is an interesting and cost-effective strategy for the quantification of biomarkers of drugs of abuse consumption in epidemiological studies. Particularly when combined with sensitive analytical method as ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS), POCIS sampling allows the long-term and sensitive determination of a wide range of analytes. In this study, a comprehensive analytical method integrating POCIS sampling, selective solid-phase extraction (SPE) of POCIS extracts, and analysis by UHPLC-MS/MS was developed and successfully validated for 12 biomarkers of substance use, with potential use in wastewater-based epidemiology. Chromatographic separation was achieved in 11 min. The assay has a wide liner range, with lower limits of quantification of 5 ng g−1 of POCIS sorbent. The selective SPE procedure, combining both cation and anion exchange cartridges, resulted in low matrix effects (-19.3 to 22.8% for compounds with a deuterated analog internal standard and 33.4 to 42.5% for anhydroecgonine methyl ester) and high extraction yields (93.4 to 106.4%). The lab-made POCIS sampler with Oasis® HLB sorbent was adequately calibrated for 9 compounds (4 drugs of abuse, 4 drug metabolites, and 1 human non-drug lifestyle markers). The method was applied in a wastewater treatment plant in Brazil, with continuous monitoring for 392 days in 2020–2021. The highest calculated wastewater concentration among drugs of abuse and metabolites was found for benzoylecgonine (431.5 ± 190.6 ng L-1), followed by 11-nor-9-carboxy-Δ9-THC (58.3 ± 21.1 ng L-1). The assay described in this study can be used as an effective tool to monitor the presence of relevant drug consumption biomarkers in wastewater, a relevant epidemiologic strategy currently limited due to the sophisticated infrastructure needed for representative sampling.

2-Nitro- and 4-fluorocinnamaldehyde based receptors as naked-eye chemosensors to potential molecular keypad lock

New-generation chemosensors desire small organic molecules that are easy to synthesise and cost-effective. As a new interdisciplinary area of research, the integration of these chemosensors into keypad locks or other advanced communication protocols is becoming increasingly popular. Our lab has developed new chemosensor probes that contain 2-nitro- (1–3) and 4-fluoro-cinnamaldehyde (4–6) and applied them to the anion recognition and sensing process. Probes 1–6 are colorimetric sensors for naked-eye detection of AcO−/CN−/F−, while probes 4–6 could differentiate between F− and AcO−/CN− anions in acetonitrile. Using the density functional theory (DFT), it was found that probes 1–6 acted as effective chemosensors. By using Probe 5 as a chemosensor, we explored colorimetric recognition of multiple anions in more detail. Probe 5 was tested in combination with a combinatorial approach to demonstrate pattern-generation capability and its ability to distinguish among chemical inputs based on concentration. After pattern discrimination using principal component analysis (PCA), we examined anion selectivity using DFT computation. In our study, probe 5 demonstrates excellent performance as a chemosensor and shows promise as a future molecular-level keypad lock system.

Structural and Potential-Dependent Metal Anion Selectivity of Redox-Metallopolymer Electrosorbents

Selective electrochemically-mediated technologies for metal separations can be essential for materials recycling and environmental sustainability. Metal recovery not only requires selectivity of the target metal over the competing electrolyte, but also selectivity between metal ions of similar size and structure in order to sort metal ions for reuse and recycling. Ferrocene polymers have been shown to be highly selective for heavy metal oxyanions through charge transfer interactions.1 Using these polymers as electrosorbents provides the opportunity for highly tuned selectivity for different metal anions through modification of the polymer structure. We demonstrate a change in structure between a pendant group ferrocene polymer, polyvinylferrocene (PVF), and a main-chain ferrocene, polyferrocenylsilane (PFS), results in differential selectivity toward metal oxyanions.2 For example, almost an order of magnitude increase in separation factor for meta-vanadate over chromate (αVO3-,CrO42-) can be achieved by altering the polymer structure from PVF (αVO3-,CrO42- = 5.2) to PFS (αVO3-,CrO42- = 39) at 0.8 V vs Ag/AgCl. Through quantum chemical calculations, we elucidate how a trimethyl silane group attached to ferrocene affects charge transfer interactions between metal anions and ferrocene binding sites. In addition, we report that these ferrocene polymers exhibit potential dependent selectivity, and in some cases can even swap preference based on the applied potential, providing an additional process variable to tune selectivity that is orthogonal to structural modifications. The underlying cause of this potential dependent selectivity is undergoing further investigation. This work demonstrates the ability to tailor ferrocene polymer electrosorbents for the targeting of specific metal ions, and hints at potential applications in multicomponent separations, including metal valorization and environmental remediation. Su, X.; Kushima, A.; Halliday, C.; Zhou, J.; Li, J.; Hatton, T. A., Electrochemically-mediated selective capture of heavy metal chromium and arsenic oxyanions from water. Nature Communications 2018, 9 (1), 4701.Chen, R.; Feng, J.; Jeon, J.; Sheehan, T.; Rüttiger, C.; Gallei, M.; Shukla, D.; Su, X., Structure and Potential-Dependent Selectivity in Redox-Metallopolymers: Electrochemically Mediated Multicomponent Metal Separations. Advanced Functional Materials 2021, n/a (n/a), 2009307.

Highly Selective Anion Exchange Membrane Based on Quaternized Poly(triphenyl piperidine) for the Vanadium Redox Flow Battery

Highly Selective Anion Exchange Membrane Based on Quaternized Poly(triphenyl piperidine) for the Vanadium Redox Flow Battery

Electrode for selective bromide removal in membrane capacitive deionisation

Due to the shortage of freshwater around the world, seawater is becoming an important water source. However, seawater contains a high concentration of bromide that can form harmful disinfection by-products during water disinfection. Therefore, the current seawater reverse osmosis (SWRO) has to adopt two-pass reverse osmosis (RO) configuration for effective bromide removal, increasing the overall desalination cost. In this study, a bromide selective composite electrode was developed for membrane capacitive deionisation (MCDI). The composite electrode was developed by coating a mixture of bromide selective resin and anion exchange polymer on the surface of the commercial activated carbon electrode, and its performance was compared to that of conventional carbon electrode. The results demonstrated that the composite electrode has ten times better bromide selectivity than the conventional carbon electrode. The study shows the potential application of MCDI for the selective removal of target ions from water sources and the potential for resource recovery through basic modification of commercial electrode.

Modulating Chalcogen Bonding and Halogen Bonding Sigma-Hole Donor Atom Potency and Selectivity for Halide Anion Recognition.

A series of acyclic anion receptors containing chalcogen bond (ChB) and halogen bond (XB) donors integrated into a neutral 3,5‐bis‐triazole pyridine scaffold are described, in which systematic variation of the electronic‐withdrawing nature of the aryl substituents reveal a dramatic modulation in sigma‐hole donor atom potency for anion recognition. Incorporation of strongly electron‐withdrawing perfluorophenyl units appended to the triazole heterocycle telluro‐ or iodo‐ donor atoms, or directly linked to the tellurium donor atom dramatically enhances the anion binding potency of the sigma‐hole receptors, most notably for the ChB and XB receptors displaying over thirty‐fold and eight‐fold increase in chloride anion affinity, respectively, relative to unfluorinated analogues. Linear free energy relationships for a series of ChB based receptors reveal the halide anion recognition behaviour of the tellurium donor is highly sensitive to local electronic environments. This is especially the case for those directly appended to the Te centre (3⋅ChB), where a remarkable enhancement of strength of binding and selectivity for the lighter halides is observed as the electron‐withdrawing ability of the Te‐bonded aryl group increases, highlighting the exciting opportunity to fine‐tune anion affinity and selectivity in ChB‐based receptor systems.

Modulating Chalcogen Bonding and Halogen Bonding Sigma‐Hole Donor Atom Potency and Selectivity for Halide Anion Recognition

AbstractA series of acyclic anion receptors containing chalcogen bond (ChB) and halogen bond (XB) donors integrated into a neutral 3,5‐bis‐triazole pyridine scaffold are described, in which systematic variation of the electronic‐withdrawing nature of the aryl substituents reveal a dramatic modulation in sigma‐hole donor atom potency for anion recognition. Incorporation of strongly electron‐withdrawing perfluorophenyl units appended to the triazole heterocycle telluro‐ or iodo‐ donor atoms, or directly linked to the tellurium donor atom dramatically enhances the anion binding potency of the sigma‐hole receptors, most notably for the ChB and XB receptors displaying over thirty‐fold and eight‐fold increase in chloride anion affinity, respectively, relative to unfluorinated analogues. Linear free energy relationships for a series of ChB based receptors reveal the halide anion recognition behaviour of the tellurium donor is highly sensitive to local electronic environments. This is especially the case for those directly appended to the Te centre (3⋅ChB), where a remarkable enhancement of strength of binding and selectivity for the lighter halides is observed as the electron‐withdrawing ability of the Te‐bonded aryl group increases, highlighting the exciting opportunity to fine‐tune anion affinity and selectivity in ChB‐based receptor systems.

Novel Fluorescence Guanidine Molecules for Selective Sulfate Anion Detection in Water Complex Samples over a Wide pH Range.

Quantitative analysis of sulfate anions in water still remains an important challenge for the society. Among all the methodologies, the most successful one is based on optical supramolecular receptors because the presence of small concentrations of sulfate anion modifies the photophysical properties of the receptor. In this case, fluorescence anion sensors have been designed by the incorporation of guanidine motifs into fluorenyl cores. The photophysical behaviors of the new mono- (M) and bis-guanidine (B) derivatives were studied through pH dependence, solvent effects, and ion sensing on steady-state spectra and time-resolved fluorescence spectroscopy. In more detail, the results demonstrate that M is a highly selective and sensitive sulfate ion receptor in real water samples and, even more importantly, its function remains unchanged at different ranges of pH. The reason behind this resides on the fluorescence quenching produced by an internal charge-transfer process when the sulfate anion is complexed with M. It is worth noting that the global and partial affinity constants (1010 M-2 and 105 M-1, respectively) of complex formation are far above from the current sulfate sensors in water (104 M-1) which give an LOD of 0.10 μM in water with an analytical range of 2.5-10 μM. On the other hand, although it would seem, at first sight, that the B derivate will be the most promising one, the possibility of having two simultaneous protonation states reduces the complex formation and, therefore, its sensitivity to sulfate anions. The results presented here offer the possibility of using a new molecule in water environments, which opens the door to infinite applications such as the detection of trace amounts of sulfate ions in food or water.

Anionic covalent organic framework as an interlayer to fabricate negatively charged polyamide composite nanofiltration membrane featuring ions sieving

Ions sieving is significant but challengeable for seawater desalination, industrial water treatment and salts recovery. Traditional nanofiltration (NF) membranes suffer from undesirable ion selectivity and permeance due to uncontrolled aromatic polyamide (PA) nanofilm. Herein, we first reported an anionic covalent organic framework (TpPa-SO3Na) with abundant sulfonic acid groups as a mediating interlayer to fabricate PA composite membrane. The uniform and negatively charged TpPa-SO3Na spherical nanoparticles were in situ soldering on nylon substrate by liquid–liquid interfacial Schiff reaction. The TpPa-SO3Na interlayer assisted in creating a defect-free PA nanofilm through mediating the diffusion–reaction process of amine monomers. According to enhanced Donnan effect, the composite polyamide nanofiltration membrane showed an outstanding salt rejection ratio (Na2SO4, 99.6%), high single salt selectivity (NaCl/Na2SO4, 178.5) and mono/divalent anion selectivity (Cl−/SO42−, 312.6), superior to most reported NF membranes. This work shed light on strategies to synthesize emerging covalent organic framework materials and to effectively construct NF composite membranes with excellent solute retention and ions sieving capabilities.

Designing smart triple-network cationic cryogels with outstanding efficiency and selectivity for deep cleaning of phosphate

Phosphate is one of the most difficult pollutants in the wastewaters asking for deep cleaning before discharge into the environment. To address this stringent need, novel composite sponges consisting of triple-cationic networks (TN) with cross-linked chitosan (CS) as the first network, cross-linked low molar mass branched poly(ethylene imine) (b-PEI) as the second network, and either b-PEI (TN1) or poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) (TN2) as the third network were fabricated in this work by ice-templating technique as advanced sorbents equipped not only with enhanced performances in the reversible capture of phosphate but also with a high mechanical strength. The structural and morphological characterization and the main factors influencing the sorption performances for phosphate anions of the TN sponges were evaluated in detail. The maximum sorption capacity of TN sorbents was reached at pH 4. The equilibrium data and the sorption kinetics were well described by the Sips isotherm and pseudo-second-order kinetic model, respectively. The equilibrium constant given by the Sips isotherm was used for the evaluation of the thermodynamic parameters. The sorption of phosphate onto the TN composite cryogels was endothermic and spontaneous. The presence of PDMAEMA facilitated desorption of phosphate when the temperature was in the range 30–35 °C. Hydrated iron oxide (HFO) nanoparticles were generated into the pores of cryogels to enhance the selectivity for phosphate anions. The pH effect on the sorption capacity, the influence of interfering ions and the analysis of the FTIR spectra, and desorption conditions demonstrated that the sorption mechanism of phosphate was complex consisting of the Coulomb attraction and inner sphere complexation. A great stability and recyclability were found for TN cryogels up to five sorption/desorption cycles.

In Situ Mechanistic Studies of Two Divergent Synthesis Routes Forming the Heteroanionic BiOCuSe.

Heteroanionic materials are a burgeoning class of compounds that offer new properties via the targeted selection of anions. However, understanding the design principles and achieving successful syntheses of new materials in this class are in their infancy. To obtain mechanistic insight and a panoramic view of the reaction progression from beginning to end of the formation of a heteroanionic material, we selected BiOCuSe, a well-known thermoelectric compound, and utilized in situ synchrotron powder diffraction as a function of temperature and time. BiOCuSe is a layered material, which crystallizes in a common mixed anion structure type: ZrSiAsFe. Two reactions of starting materials (Bi2O2Se + Cu2Se and Bi2O3 + Bi + 3Cu + 3Se) were studied to determine the effect of precursors on the reaction pathway. Our in situ investigation shows that the ternary-binary Bi2O2Se + Cu2Se reaction proceeds without intermediates to directly form BiOCuSe, while the binary-elemental Bi2O3 + Bi + 3Cu + 3Se reaction generates many intermediates before the final product forms. These intermediates include CuSe, Bi3Se4, Bi2Se3, and Cu2Se. While the stoichiometric loading of the precursors necessarily dictates the identity of the first intermediates, kinetics also plays a contributing role in stabilizing unexpected intermediates such as CuSe and Bi3Se4. Understanding and establishing a link between the selection of precursors and the reaction pathways improves the potential for rational synthesis of heteroanionic materials and solid-state reactions in general.

Di-quaternized graphene oxide based multi-cationic cross-linked monovalent selective anion exchange membrane for electrodialysis

A series of monovalent anion selective membranes were synthesized by crosslinking of chloromethylated polysulfone with 1,4-diazabicyclo [2.2.2] octane functionalized graphene oxide (QGO). Cross-linking of QGO provides dense polymer matrix as well as additional functional sites to the membrane. The effect of QGO on physicochemical and electrochemical properties was studied in detail. The best optimized membrane, CrPSf-3 (3 wt% of nano cross-linker) showed 2.01 mmol·g−1 ion exchange capacity, 9.90% swelling ratio, 31.20% water uptake, 72 mS·cm−1 chloride ion conductivity and 0.95 counter ion transport number along with good mechanical and thermal stability. Electrodialysis performance of membrane permselectivity between Cl− and SO42− was studied in mixed salt solution of 0.05 mol·L-1 (NaCl + Na2SO4). The CrPSf-3 membrane showed 5.7 separation factor (SF) for Cl−/SO42− which is higher than pristine QPSf (1.7) and commercial FAB-PK-130 membrane (2.01). Furthermore, higher Cl− flux (2.97 mol·m-2h−1) was observed for CrPSf-3 membrane as compare to pristine QPSf (1.45 mol·m-2h−1) and commercial membrane (1.6 mol·m−2·h−1). To achieve monovalent anion selectivity, effective cross-linking is facile approach to control compactness of the membrane and ion transport channels. Reported cross-linked membrane possesses a potential candidate for water desalination, wastewater treatment, or other monovalent selective separation processes.

Effect of copper addition in carbon steel on biocorrosion by sulfate-reducing bacteria in solution

Purpose This paper aims to investigate the anti-biocorrosion performance and mechanism of the Cu-bearing carbon steel in the environment containing sulfate-reducing bacterial (SRB). Design/methodology/approach The biocorrosion behavior of specimens with Cu concentration of 0 Wt.%, 0.1 Wt.%, 0.3 Wt.% and 0.6 Wt.% were investigated by immersion test in SRB solution. By examining the prepared cross-section of the biofilm using focused ion beam microscopy, SRB distribution, bacterial morphology, biofilm structure and composition were determined. The ion selectivity of the biofilm was also obtained by membrane potential measurement. Moreover, the anti-biocorrosion performance of the Cu-bearing carbon steel pipeline was tested in a shale gas field in Chongqing, China. Findings Both the results of the laboratory test and shale gas field test indicate that Cu-bearing carbon steel possesses obvious resistance to microbiologically influenced corrosion (MIC). The SRB, corrosion rate and pitting depth decreased dramatically with Cu concentration in the substrate. The local acidification caused by hydrolyze of ferric ion coming from SRB metabolism and furtherly aggravated by anion selectivity biofilm promoted the pitting corrosion. Anti-biocorrosion of Cu-bearing carbon steel was attributed to the accumulation of Cu compounds in the biofilm and the weaker anion selectivity of the biofilm. This research results provide an approach to the development of economical antibacterial metallic material. Originality/value MIC occurs extensively and has become one of the most frequent reasons for corrosion-induced failure in the oil and gas industry. In this study, Cu-bearing carbon steel was obtained by Cu addition in carbon steel and possessed excellent anti-biocorrosion property both in the laboratory and shale gas field. This study provides an approach to the development of an economical antibacterial carbon steel pipeline to resist MIC.

Ion selective redox active anion exchange membrane: Improved performance of vanadium redox flow battery

In-sight understanding of synergetic and trade-off behaviour between chemical and structural properties of emerging redox active membrane separator for batteries is necessary for high performance and widespread adoption of technologies. Our aim is to provide sustainable solution such as stable membrane with fast ionic-transport (low resistivity), and impervious nature for redox active species that leads to deleterious capacity fade and materials underutilization. We report architecture of redox active anion exchange membranes (AEMs) by free radical polymerization using tert-butylmethaacrylate (tBuMA), vinylimidazole (VIm) and vinyl ferrocene (VFc). The VFc acts as redox responsive species (ferrocenium ion) due to protonation under operating conditions. These ion selective redox active membranes offer chemical modularity, high conductivity, stability, and prevents VO2+ cross-over, necessary for improved vanadium redox flow battery (VRFB) performance. The fundamental electrochemistry of redox active membranes is fascinating, due to redox peaks (Fc/Fc+) in voltammetry. Suitable redox-active membrane separator exhibits 98.0% current efficiency corresponding to 85.0% voltage efficiency at 60 mA cm−2 in VRFB operation. Therefore, AEMs with redox active functional moieties can open a new avenue for efficient VRFB and various electrochemical applications.

Functionalized biochar electrodes for asymmetrical capacitive deionization

Electrosorption-based capacitive deionization (CDI) has become a viable process for brackish water desalination. In this study, activated Douglas-fir biochar is used as a low-cost carbon-based alternative electrode with adsorption capacity comparable to activated carbon obtained from biomass precursors. Adding functional groups to the activated biochar enhanced salt removal capacity, providing cation and anion selectivity. The functionalized electrodes were prepared by Nafion and p-phenylenediamine treatment, respectively, which introduced sulfonate and amine functional groups to the electrode. These modification methods are versatile and can be easily performed without sophisticated laboratory environment. These modified biochar electrodes were characterized by SEM-EDX and XPS. Cyclic voltammetry and galvanostatic charge/discharge measurements were performed to analyze the electrochemical properties of both types of electrodes and the electrosorption capacity was evaluated in a 3D-printed capacitive deionization flow cell using a chloride ion-selective electrode. It was found that an asymmetrical cell with Nafion cathode and amine biochar anode increased removal capacity by 54% over the activated biochar symmetrical cell (identical anode and cathode), with 6.01 mg NaCl/g biochar at the symmetrical cell and 9.25 mg g−1 for the asymmetrical cell. This work shows that biochar can be engineered and explored broadly as an inexpensive sustainable electrode material for asymmetrical capacitive deionization.

The fluoride permeation pathway and anion recognition in Fluc family fluoride channels.

Fluc family fluoride channels protect microbes against ambient environmental fluoride by undermining the cytoplasmic accumulation of this toxic halide. These proteins are structurally idiosyncratic, and thus the permeation pathway and mechanism have no analogy in other known ion channels. Although fluoride-binding sites were identified in previous structural studies, it was not evident how these ions access aqueous solution, and the molecular determinants of anion recognition and selectivity have not been elucidated. Using x-ray crystallography, planar bilayer electrophysiology, and liposome-based assays, we identified additional binding sites along the permeation pathway. We used this information to develop an oriented system for planar lipid bilayer electrophysiology and observed anion block at one of these sites, revealing insights into the mechanism of anion recognition. We propose a permeation mechanism involving alternating occupancy of anion-binding sites that are fully assembled only as the substrate approaches.

From a eutectic mixture to a deep eutectic system via anion selection: Glutaric acid + tetraethylammonium halides.

In pursuit of understanding structure-property relationships for the melting point depression of binary eutectic mixtures, the influence of the anion on the solid-liquid (S-L) phase behavior was explored for mixtures of glutaric acid + tetraethylammonium chloride, bromide, and iodide. A detailed experimental evaluation of the S-L phase behavior revealed that the eutectic point is shifted toward lower temperatures and higher salt contents upon decreasing the ionic radius. The salt fusion properties were experimentally inaccessible owing to thermal decomposition. The data were inter- and extrapolated using various models for the Gibbs energy of mixing fitted to the glutaric-acid rich side only, which allowed for the assessment of the eutectic point. Fitting the experimental data to a two-parameter Redlich-Kister expansion with Flory entropy, the eutectic depth could be related to the ionic radius of the anion. The anion type, and in particular its size, can therefore be viewed as an important design parameter for the liquid window of other acid and salt-based deep eutectic solvents/systems.

Assessment of anion exchange membrane selectivity with ionic membrane conductivity, revised with Manning's theory or the Kohlrausch's law

The evaluation of anion exchange membrane (AEM) selectivity towards different anions requires facile characterization methods. The anion selectivity of membranes could principally, but practically not easy to, be extracted from the measured anion transport selectivity in electrodialysis (ED), which is a parameter closely related to the process conditions. According to the classical solution-diffusion model, the membrane anion selectivity could be decoupled into two parts: the partitioning selectivity factor of anions between the membrane and the solution phase; the mobility ratio of anions in the membrane. Alternatively, based on the relationship between the anion composition in the membrane and the mixed-ionic membrane conductivities, these two parts can be calculated from the volumetric swelling ratios and ionic conductivities when the AEMs are in pure and mixed-anion forms, respectively. This relationship is proved to be linear in two commercial AEMs (ASE and ACS) for the NO3−/Cl− and SO42−/Cl− pairs. Further, it is possible to obtain the anion selectivity directly for the ASE membrane from corresponding membrane ionic conductivities, with Manning's counter-ion condensation theory to account for the anion activity coefficients in the membrane. While for the NO3−/Cl− pair in the monovalent-anion selective ACS membrane, the selectivity thus calculated is very different from that obtained in ED. For the nonlinear anion composition-conductivity relationship observed in the commercial FAA membrane, the Kohlrausch's parameter (σ) is successfully introduced to describe the mutual influence of anions in the membrane. In this case, it is also possible to obtain the anion selectivity with the proposed approach. This work provides a different perspective to study the selectivity and conductivity of AEMs.

Highly Active Halogen Bonding and Chalcogen Bonding Chloride Transporters with Non-Protonophoric Activity.

Synthetic anion transporters show much promise as potential anti‐cancer agents and therapeutics for diseases associated with mis‐regulation of protein anion channels. In such applications high activity and anion selectivity are crucial to overcome competing proton or hydroxide transport which dissipates cellular pH gradients. Here, highly active bidentate halogen bonding and chalcogen bonding anion carriers based on electron deficient iodo‐ and telluromethyl−triazole derivatives are reported. Anion transport experiments in lipid bilayer vesicles reveal record nanomolar chloride transport activity for the bidentate halogen bonding anion carrier, and remarkably high chloride over proton/hydroxide selectivity for the chalcogen bonding anionophore. Computational studies provide further insight into the role of sigma‐hole mediated anion recognition and desolvation at the membrane interface. Comparison with hydrogen bonding analogues demonstrates the importance of employing sigma‐hole donor motifs in synthetic anionophores for achieving both high transport activity and selectivity.