Rationally synthesized framework polymer membranes enable high selectivity and barrierless anion conduction

Rationally synthesized framework polymer membranes enable high selectivity and barrierless anion conduction | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Rationally synthesized framework polymer membranes enable high selectivity and barrierless anion conduction Zhengjin Yang, Junkai Fang, Guozhen Zhang, Marc-Antoni Goulet, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4392718/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 06 Apr, 2025 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Abstract The understanding gleaned from studying ion transport within the interaction confinement regime enables the near-frictionless transport of cations ( e.g., Na + /K + ). However, anion transport ( e.g., Cl - ) is suppressed under confinement because of the different polarization of water molecules around cations and anions, also known as the charge asymmetry effect. Here we report the rational synthesis of anion-selective framework polymer membranes having similar densities of subnanometer-sized pores with nearly identical micropore size distributions, which overcome the charge asymmetry effect and promote barrierless anion conduction. We find that anion transport within the micropore free volume elements can be dramatically accelerated by regulating the pore chemistry, which lowers the energy barrier for anion transport, leading to an almost twofold increase in Cl - conductivity and barrierless F - diffusion. The resultant membrane enables an aqueous organic redox flow battery that utilizes Cl - ions as charge carriers to operate at extreme current densities and delivers competitive performance to counterparts where K + ions are charge carriers. These results may benefit broadly electrochemical devices and inspire single-species selectivity with separation membranes that exploit controlled or chemically gated ion/molecule transport. Physical sciences/Chemistry/Materials chemistry/Soft materials/Polymers Physical sciences/Engineering/Chemical engineering Physical sciences/Chemistry/Energy Figures Figure 1 Figure 2 Figure 3 Figure 4 Main Text Replicating the extreme selectivity and high permeability of biological ion channels is an enduring challenge for membrane scientists ( 1 – 3 ). Beyond the generally-accepted mechanisms of size exclusion and Coulombic repulsion, it is argued that the subtle interactions between ions and channel walls at atomic-scale confinement play a crucial role. These interactions were not clearly elucidated until the fabrication of angstrom-scale slits/capillaries/channels with atomic-scale precision ( 4 , 5 ). The spatial confinement of ion transport down to molecular-sized ion channels magnifies the impact of channel wall interactions and gives rise to exotic transport behavior. For example, hysteretic ion conduction occurs, resulting in an ion memory effect ( 6 , 7 ), while the formation of Bjerrum ion pairs causes ionic Coulombic blockade ( 8 ). These atypical ion motions are intimately related to the dramatically enhanced material-dependent interactions between hydrated ions and the confining channel walls ( e.g. , electrostatic, adsorption/desorption) ( 9 ). For chemically inert and atomically smooth graphite channel walls, K + demonstrates a mobility close to that of the value in bulk solutions ( 10 ). By applying a voltage bias on the graphite channel, the streaming mobility of K + is increased by up to 20 times ( 11 ) and this may be ascribed to the electronic structure change under an external voltage bias ( 12 ). It has also been demonstrated that by introducing Li + -coordinating functionality within the shape-persistent free volume elements of microporous polymer membranes, Li + diffusivity can be greatly enhanced ( 13 ). Similar improvements to Na + transport have also been achieved by exploiting the synergy between micropore confinement and ion-membrane interactions ( 14 ). Despite the considerable improvements in cation transport due to the confinement effect, it is notable that chloride (Cl − ) mobility experiences significant suppression under confinement. This charge asymmetry is likely due to the slightly different hydration shell configurations between Cl − and K + ( 10 ). The mobility of Cl − under confinement is three times less than that of K + , even though Cl − and K + have similar mobilities in bulk water (7.58×10 − 8 vs. 7.86×10 − 8 m 2 V − 1 s − 1 ) and hydrated diameters (6.64 Å vs. 6.62 Å) ( 15 , 16 ). For a more extreme case, Cs + and Cl − exhibit similar ion-core sizes and hydrated diameters, but Cl − exhibits more than three times lower mobility under Å-scale confinement (1.7×10 − 8 vs. 6.0×10 − 8 m 2 V − 1 s − 1 ) ( 16 ). For chloride salts of high valency cations, the overall Cl − mobility decreases to almost zero in single-digit-sized nanopores ( 17 ). A decrease in the mobility of other anions under confinement has also been observed ( 16 ). This phenomenon is echoed by the relatively high energy barrier associated with anion exchange membranes that transport chloride ions (see Supplementary Table S1 ). The transport and selectivity of anions are of critical relevance to applications such as direct seawater electrolysis ( 18 ), solid-state batteries ( 19 ) and redox flow batteries ( 20 – 25 ). Understanding and overcoming the charge asymmetry effect for anion transport under confinement is therefore essential for enabling these technologies. Here we report the design and synthesis of a series of positively charged (quaternary ammonium cations) covalent triazine framework (QCTF) membranes with nearly the same density of rigid micropores with almost identical pore size distributions. The QCTF membranes exhibit Coulombic repulsion-induced anion selectivity, with a chloride transference number t − of 0.95, and size exclusion-induced rejection of BTMAP-Vi (bis(3-trimethylammonio) propyl viologen tetrachloride) and FcNCl ((ferrocenylmethyl) trimethylammonium chloride), redox-active organic flow battery electrolytes. The cross-membrane BTMAP-Vi diffusion coefficient at 3.1×10 − 11 cm 2 s − 1 is over 20 times lower than that of commercial membranes. We demonstrate that through on-membrane modification, the charge distribution of the pristine QCTF membrane framework can be regulated by protonation (affording P-QCTF) and methylation (affording M-QCTF), which dramatically alters the interactions between anions and the membrane framework and helps lower the energy barrier for anion transport. The cross-membrane Cl − conductivity increased twofold from 13.2 mS cm − 1 for QCTF to 25.9 mS cm − 1 for M-QCTF at 30°C, and the activation energy for Cl − conduction decreased from 20.6 kJ mol − 1 to 13.1 kJ mol − 1 , lower than any value reported in the literature (see Supplementary Table S1 ). 19 F PFG-NMR revealed an increase in the F − diffusion coefficient from 0.63×10 − 9 m 2 s − 1 for QCTF and 0.93×10 − 9 m 2 s − 1 for P-QCTF, to 1.1×10 − 9 m 2 s − 1 for M-QCTF which is close to the value in bulk water (1.2×10 − 9 m 2 s − 1 ). The greater anion conductivity can dramatically improve device performance as exemplified here in an BTMAP-Vi- and FcNCl-based aqueous organic redox flow battery (AORFB) in pH-neutral solutions. The BTMAP-Vi/FcNCl cell configured with the M-QCTF membrane exhibited a high-frequency area-specific resistance (ASR) as low as 0.23 Ω·cm 2 , which enabled charging and discharging of the BTMAP-Vi/FcNCl cell at an extreme current density of 500 mA cm − 2 . The prolonged galvanostatic cell cycling at 400 mA cm − 2 maintained a Coulombic efficiency of > 99% and a stable energy efficiency of around 60% over the course of 1000 cycles. Notably, the achieved capacity utilization and efficiency with M-QCTF approaches similar values to those of alkaline AORFBs that leverage K + as charge-carrying ions, while in otherwise identical cells assembled with QCTF or P-QCTF, an almost 20% lower energy efficiency was observed. This is significant and can be attributed to a dramatic reduction in the contribution of membrane resistance to whole–cell resistance, e.g., from > 70% for the Selemion® AMV membrane to ~ 25% for M-QCTF (Supplementary Tables S2 and S3). The above results imply a breakthrough in the charge asymmetry effect. Results and Discussion Covalent triazine framework membranes with tunable pore chemistry Covalent triazine framework chemistry gives rise to a wide variety of microporous materials and offers enormous diversity in pore chemistry. We thus synthesized a stand-alone triazine framework membrane from 4,4'-biphenyldicarbonitrile and a derivative of 3-hydroxy-[1,1'-biphenyl]-4,4'-dicarbonitrile bearing a quaternary ammonium moiety via a superacid-catalyzed organic sol‒gel procedure (Fig. 1 a and Supplementary Figures S1 -S4) ( 26 ). The process yields a free-standing membrane (namely, QCTF) with a Young’s modulus and tensile strength of 0.91 GPa and 32.0 MPa, respectively (Supplementary Figure S5). The skeletal triazine rings of QCTF were subsequently protonated with HCl or methylated with CH 3 I, affording P-QCTF and M-QCTF, respectively. Overall, we constructed three covalent triazine framework polymers with similar molecular configurations and pore structures that can be processed into hydrophilic, uniform and robust ion-selective membranes via an organo-sol‒gel procedure (Supplementary Figures S6-S8, Supplementary Table S4), but with slightly different and deliberately tailored pore chemistries. Carbon dioxide (CO 2 ) adsorption experiments and molecular simulations were conducted to probe the micropore structure of the covalent triazine framework polymers. CO 2 sorption isotherms measured at 273 K revealed that powder samples of QCTF, P-QCTF, and M-QCTF had similar CO 2 uptake capacities of 16, 15.2, and 14.7 cm 3 g − 1 STP, respectively (Fig. 1 b). Notably, QCTF, P-QCTF, and M-QCTF exhibit almost identical pore size distributions, ranging from 0.3 nm to 0.9 nm, as derived from CO 2 adsorption isotherms based on density functional theory (DFT) calculations (Fig. 1 c). These experimental results are further supported by molecular simulations of the 3D framework structure and the computation of CO 2 distributions within the framework structures (Supplementary Figures S9 and S10). This again indicates that QCTF, P-QCTF, and M-QCTF have similar framework structures, interconnected micropores and pore size distributions. The amount of charged functional groups (quaternary ammonium groups) within the pristine QCTF membrane, characterized by the ion exchange capacity (IEC, in mmol g − 1 ), is 1.20 mmol g − 1 for QCTF (as-designed IEC value is ~ 1.00 mmol g − 1 ). During protonation, approximately 55% of the triazine rings were protonated and the same amount of triazine rings was methylated after methylation, as revealed by X-ray photoelectron spectroscopy (XPS, Fig. 1 d). This suggests that P-QCTF and M-QCTF should have identical IEC values, which was confirmed by titration and zeta potential measurements (Supplementary Figure S11). Ion Transport and Selectivity Despite the similar framework structure and almost identical pore size/size distributions, our experimental results reflect that cross-membrane ion transport is significantly affected by pore chemistry. We speculate that the difference is synergistically determined by Coulombic/steric effects and specific ion‒pore wall interactions, as shown in Fig. 2 a. The current‒voltage (I‒V) curves across the membranes, as measured in a two-compartment diffusional H-cell under a 10-fold concentration gradient KCl solution (Fig. 2 b), reveal a net anion flux, indicating anion selectivity. The anion transference number ( t − ) calculated for QCTF is 0.940, while the values for protonated QCTF (P-QCTF) and methylated QCTF (M-QCTF) are 0.947 and 0.953, respectively (Supplementary Figure S12). These values suggest the superior anion selectivity of the QCTF membranes compared to that of commercial anion exchange membranes (AEMs). This result is reasonable considering the Coulombic repulsion of the < 1 nm pore channel within the QCTF membranes. The measured transference numbers align with the cross-membrane permeation/diffusion rates for BTMAP-Vi (a redox-active organic cation) and Cl − (Fig. 2 c and 2 d, Supplementary Figures S13-S15, Supplementary Tables S5-S6), which are dramatically different in size. Compared with commercial AEMs (Fig. 2 c), all the QCTF membranes exhibited superior blocking capabilities toward BTMAP-Vi. The diffusion coefficients of BTMAP-Vi across the QCTF and the P-QCTF were determined to be 4.5×10 − 11 cm 2 s − 1 and 3.4×10 − 11 cm 2 s − 1 , respectively. These values are at least one order of magnitude smaller than those of commercial AEMs. Note that the value further decreases to 3.1×10 − 11 cm 2 s − 1 for M-QCTF, a value that is over 20 times smaller than that of Selemion® DSV. The diffusion coefficients of Cl − through the QCTF and P-QCTF are 1.8×10 − 7 cm 2 s − 1 and 2.6×10 − 7 cm 2 s − 1 , respectively. By contrast, commercial anion-selective membranes demonstrated Cl − diffusion coefficients at least one order of magnitude smaller than those of QCTF membranes. Surprisingly, the Cl − diffusion coefficient measured for M-QCTF reached 3.0×10 − 7 cm 2 s − 1 , which is nearly 2 times that for the QCTF membrane (Fig. 2 d). A comparison of the Cl − diffusion coefficients and the Cl − /BTMAP-Vi selectivity for QCTF membranes, commercial AEMs and previously reported membranes implies that these framework membranes can simultaneously deliver fast ion permeation and high selectivity, overcoming the usual tradeoff observed for many ion exchange membranes (Supplementary Figure S16 and Supplementary Table S6). The fast Cl − transport across the triazine framework membranes is further supported by the membrane conductivity measurements. Compared with commercial AEMs, triazine framework membranes show high Cl − conductivity at relatively low hydration numbers (Fig. 2 e, Supplementary Figure S17 and Supplementary Tables S7-S8). The Cl − conductivity of QCTF, as measured by four-point electrochemical impedance spectroscopy (EIS), is 13.2 mS cm − 1 at 30.0°C and approaches 42.0 mS cm − 1 at 80°C at low hydration numbers (3.5 at 30°C, 4.4 at 80°C). In comparison, the Cl − conductivity of P-QCTF is 20.0 mS cm − 1 at 30°C and increases to 48.4 mS cm − 1 at 80°C. We find that the Cl − conductivity of M-QCTF is 26.0 at 30.0°C, which is nearly twice that of QCTF, and reaches 53.0 mS cm − 1 at 80°C. The activation energy ( E a ) for Cl − conduction across the QCTF membrane is 20.6 kJ mol − 1 , as derived from the conductivities at various temperatures (Fig. 2 f and Supplementary Figure S18), contrasting an E a of 12.9 kJ mol − 1 for K + transport across an otherwise identical membrane with sulfonate functional groups (ref 14). Surprisingly, the E a value for M-QCTF is as low as 13.1 kJ mol − 1 , which is nearly half that of QCTF and lower than any value reported in the literature (Fig. 2 g and Supplementary Table S1 ). Considering the similar framework structure and almost identical pore size/size distributions, this significant result indicates that the methylation of triazine rings alters the transport energy barrier for Cl − ions. Due to the aforementioned results, we conclude that electrostatic interactions alone cannot explain the differences in Cl − diffusion coefficients, Cl − conductivity or activation energy for cross-membrane Cl − transport. To unravel why methylation of the triazine ring promotes fast Cl − conduction, compared to the protonated triazine ring in P-QCTF and the charge-neutral triazine ring in QCTF, the charge distribution and the Cl − transport routes within the matrix of the triazine framework membranes were portrayed based on molecular simulations, and the two-dimensional free-energy landscapes were computed according to current methodology ( 13 , 14 ). Our calculations show that the charge distributions of triazine framework membranes vary dramatically after protonation and methylation (Fig. 3 a, Supplementary Figure S19). The most even charge distribution is observed for M-QCTF. We speculate that the variation in charge distribution alters the interactions between anions and the membrane frameworks and helps establish low-energy-barrier pathways for anion transport. This is supported by free energy calculations for Cl − conduction (Fig. 3 b). The simulation results showed that Cl − can interact with quaternary ammonium (QA) groups (Fig. 3 c, Supplementary Figures S20 and S21) and lower the free energy, but an energy barrier must be overcome for Cl − ions to approach adjacent QA groups. The energy barrier for Cl − conduction is the highest for QCTF (Fig. 3 b, left panel) and decreases when the triazine ring is protonated (Fig. 3 b, middle panel), while methylation of the triazine ring in M-QCTF improves the diffusivity of Cl − within the framework and creates a Cl − diffusion pathway with the lowest energy barrier (Fig. 3 b, right panel). We suspect that the synergy of electrostatic interactions between Cl − and the methylated triazine ring and the change in electron density along the Cl − diffusion path after methylation may account for the emergence of the low-energy-barrier diffusion pathway. Molecular simulation results are further supported by measurements of transmembrane F − diffusion coefficients via 19 F pulsed-field gradient-stimulated-echo nuclear magnetic resonance ( 19 F PFG-NMR; 19 F was selected owing to its higher sensitivity compared with 35 Cl). 19 F PFG-NMR revealed two separate F − signals for Selemion® DSV and Selemion® AMV membranes (Fig. 3 d and Supplementary Figure S22), with the upfield signal corresponding to free F − in water (located at the same position as that in 0.1 M KF aqueous solution) and the downfield signal corresponding to associated F − within the membrane. In contrast, only the upfield signal was observed for all three triazine framework membranes (Fig. 3 d), which is an indication of freely exchangeable F − within the membrane, with slight variations in the 19 F chemical shifts. By fitting the echo profiles with the Stejskal‒Tanner equation (Supplementary Figure S23), the derived F − diffusion coefficients within the P-QCTF and QCTF are 0.93×10 − 9 m 2 s − 1 and 0.63×10 − 9 m 2 s − 1 , respectively (Fig. 3 e). The value reaches 1.1×10 − 9 m 2 s − 1 for M-QCTF, almost a twofold increase compared to that for QCTF. Notably, this value is 12.8 times that of Selemion® AMV and 10.8 times that of Selemion® DSV (Fig. 3 e and Supplementary Figure S23) and approaches the measured diffusion coefficient of F − in water (1.2×10 − 9 m 2 s − 1 ; Supplementary Figure S23). In summary, by tailoring the pore chemistry of framework membranes, intimate ion‒pore wall interactions provide a low-energy-barrier diffusion pathway for anions. Taken together with the Coulombic/steric exclusion by the charged framework micropores, the triazine framework membranes, particularly M-QCTF, will be of interest in applications demanding extremely fast and highly selective transport of anions. Triazine framework membrane powers fast-charging AORFBs The extremely fast and highly selective anion (particularly chloride ions) conduction through chemically tuned triazine framework membranes is desirable in electrochemical devices, such as aqueous organic redox flow batteries. As a proof of concept, we configured pH-neutral AORFBs with BTMAP-Vi/FcNCl as the redox-active organic electrolyte couple and triazine framework membranes as the ion-conducting membranes, while Cl − ions were transported back and forth as charge carriers (Fig. 4 a). At an electrolyte concentration of 0.1 M, EIS of the BTMAP-Vi/FcNCl cells assembled with QCTF or P-QCTF showed area-specific membrane resistances (ASRs) of 0.63 Ω cm 2 and 0.53 Ω cm 2 , respectively (Supplementary Figures S24-S25). An otherwise identical cell assembled with M-QCTF showed an ASR of 0.37 Ω cm 2 (Supplementary Figure S26), which is almost twofold lower than that of the QCTF membrane. This finding aligns with the high conductivity of M-QCTF (Fig. 2 e, 3 b), which enables charging of the BTMAP-Vi/FcNCl cells at extreme current densities. For example, at 200 mA cm − 2 , BTMAP-Vi/FcNCl with M-QCTF exhibited an energy efficiency (EE) of over 60% (Supplementary Figure S26). In contrast, the control BTMAP-Vi/FcNCl cells assembled with Selemion® DSV or Selemion® AMV could not operate at this current density due to the immediate voltage cutoff. At lower current densities ranging from 20 to 80 mA cm − 2 , the reported energy efficiency for the control cells drops from 89.4–65.9% for Selemion® DSV or from 80.0–26.6% for Selemion® AMV ( 27 ). At a higher electrolyte concentration of 0.5 M, BTMAP-Vi/FcNCl with M-QCTF demonstrated an even lower ASR of 0.23 Ω cm 2 (Fig. 4 b), a much lower value than that for Selemion® DSV or Selemion® AMV. The rate performance of the cell reveals an EE of 49.7% and a capacity utilization of 58.8% at an extreme current density of 500 mA cm − 2 (Fig. 4 c). Compared with the most recent report of an AEM (MTCP-50 membrane, with the optimal ratio 1:1 of m -terphenyl to p -terphenyl) for pH-neutral AORFBs at 0.5 M ( 21 ), M-QCTF achieved a much greater energy efficiency (76.9% vs. 60.1%) and capacity utilization (94.3% vs. 63.7%) at the same current density of 200 mA cm − 2 . Notably, alkaline AORFBs that utilize K + as charge-carrying ions assembled with a cation exchange membrane (SCTF-BP), which allows cation diffusion close to the value in bulk electrolyte, exhibit an EE of 50.4% and a capacity utilization of 62% at 500 mA cm − 2 . The current results demonstrate a similar efficiency for Cl − transport and therefore suggest a breakthrough in the charge asymmetry effect. Robust and exceptional cell performance was observed during long-term galvanostatic cycling of over 2000 cycles at 200 mA cm − 2 (0.1 M electrolyte concentration, Supplementary Figure S26) and over 1000 cycles at 400 mA cm − 2 (0.5 M electrolyte concentration, Fig. 4 d). Comparisons of the EE and capacity utilization against the current density shows consistently superior battery performance over multiple cell cycling experiments for the BTMAP-Vi/FcNCl cells with M-QCTF, compared to the pH-neutral AORFB with different membranes (Fig. 4 e, 4 f and Supplementary Table S10). This work demonstrates that chloride and fluoride anions traverse the M-QCTF membrane with a very low energy barrier, leading to exceptional flow battery performance. This significant development can be applied more broadly to designing anion exchange membranes for other technologies such as CO 2 electrolysers ( 28 ) and ion-capture electrodialysis ( 29 ). Although the anion diffusion constants within the developed membranes are approaching the theoretical limit of the bulk electrolyte solution, we expect further improvements in overall conductivity to be achievable by eliminating micropore tortuosity and creating perfectly aligned micropore channels with monodispersed pore size distributions. Declarations Acknowledgments This work was funded by the National Key R&D Program of China (2021YFB4000302) and the National Natural Science Foundation of China (Grant/Award No. U20A20127, 52021002). This work was partially carried out at the Instruments Center for Physical Science, University of Science and Technology of China. Competing interests The authors declare no competing interests. Data availability The authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials. Source data are available on reasonable request from the corresponding author. References D. A. Doyle et al. , The structure of the potassium channel: molecular basis of K + conduction and selectivity. Science 280 , 69 (1998). H. B. Park et al. , Maximizing the right stuff: the trade-off between membrane permeability and selectivity. Science 356 , eaab0530 (2017). Y. J. Lim et al. , The coming of age of water channels for separation membranes: from biological to biomimetic to synthetic. Chem. Soc. Rev. 51 , 4537-4582 (2022). B. Radha et al. , Molecular transport through capillaries made with atomic-scale precision. Nature 538 , 222-225 (2016). A. Bhardwaj et al. , Fabrication of angstrom-scale two-dimensional channels for mass transport. Nat. Protoc. 19 , 240-280 (2023). T. Xiong et al. , Neuromorphic functions with a polyelectrolyte-confined fluidic memristor. Science 379 , 156-161 (2023). P. Robin et al. , Long-term memory and synapse-like dynamics in two-dimensional nanofluidic channels. Science 379 , 161-167 (2023). N. Kavokine et al. , Ionic Coulomb blockade as a fractional Wien effect. Nat. Nanotechnol. 14 , 573-578 (2019). P. Robin et al. , Modeling of emergent memory and voltage spiking in ionic transport through angstrom-scale slits. Science 373 , 687-691 (2021). A. Esfandiar et al. , Size effect in ion transport through angstrom-scale slits. Science 358 , 511-513 (2017). T. Mouterde et al. , Molecular streaming and its voltage control in ångström-scale channels. Nature 567 , 87-90 (2019). F. Chen et al. , Inducing electric current in graphene using Ionic flow. Nano Lett. 23 , 4464-4470 (2023). M. J. Baran et al. , Diversity-oriented synthesis of polymer membranes with ion solvation cages. Nature 592 , 225-231 (2021). P. Zuo et al. , Near-frictionless ion transport within triazine framework membranes. Nature 617 , 299-305 (2023). Y. Zhao et al. , Differentiating solutes with precise nanofiltration for next generation environmental separations: a review. Environ. Sci. Technol. 55 , 1359-1376 (2021). S. Goutham et al. , Beyond steric selectivity of ions using ångström-scale capillaries. Nat. Nanotechnol. 18 , 596-601 (2023). J. Ma et al. , Multivalent ion transport through a nanopore. J. Phys. Chem. C 126 , 14661-14668 (2022). H. Xie et al. , A membrane-based seawater electrolyser for hydrogen generation. Nature 612 , 673-678 (2022). G. Karkera et al. , A structurally flexible halide solid electrolyte with high ionic conductivity and air processability. Adv. Energy Mater. 13 , 2300982 (2023). S. Pang et al. , Biomimetic amino acid functionalized phenazine flow batteries with long lifetime at near‐neutral pH. Angew. Chem. Int. Edit. 60 , 5289-5298 (2021). W. Song et al. , Upscaled production of an ultramicroporous anion-exchange membrane enables long-term operation in electrochemical energy devices. Nat. Commun. 14 , 2732 (2023). M. E. Carrington et al. , Associative pyridinium electrolytes for air-tolerant redox flow batteries. Nature 623 , 949-955 (2023). P. Xiong et al. , A chemistry and microstructure perspective on ion‐conducting membranes for redox flow batteries. Angew. Chem. Int. Edit. 60 , 24770-24798 (2021). B. Hu et al. , Long-cycling aqueous organic redox flow battery (AORFB) toward sustainable and safe energy storage. J. Am. Chem. Soc. 139 , 1207-1214 (2017). J. Luo et al. , A π‐conjugation extended viologen as a two‐electron storage anolyte for total organic aqueous redox flow batteries. Angew. Chem. Int. Edit. 57 , 231-235 (2017). X. Zhu et al. , A superacid-catalyzed synthesis of porous membranes based on triazine frameworks for CO 2 separation. J. Am. Chem. Soc. 134 , 10478-10484 (2012). H. Li et al. , Ultra-microporous anion conductive membranes for crossover-free pH-neutral aqueous organic flow batteries. J. Membr. Sci. 668 , 121195 (2023). D. A. Salvatore et al. , Designing anion exchange membranes for CO 2 electrolysers. Nat. Energy 6 , 339-348 (2021). A. A. Uliana et al. , Ion-capture electrodialysis using multifunctional adsorptive membranes. Science 372 , 296-299 (2021). Additional Declarations There is NO Competing Interest. Supplementary Files 03supplementarymaterials.docx Cite Share Download PDF Status: Published Journal Publication published 06 Apr, 2025 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4392718","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":312837599,"identity":"e870fe8a-55d1-4e14-8e23-6d6099f67f93","order_by":0,"name":"Zhengjin Yang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6klEQVRIie3RuwrCMBSA4RMKnYKuEayXN0gJVIfisyhCuxRnx4qDS3HWtygIzoEMXSpdO9ZFETroVicNKI6xo2B+CGQ4HxwSAJ3uZ8Ok03xfUViTuKwVvqbrEvAmMa9LaHIQl6otJrvcPxcVuFbMjVOhJOnMGxIs2D4P7EUEHou5OaBKwgOHUiwsSdASQMgNsUmUJCsdOsYC7Tb+UZJHDZIHrODY68dkbEvCv5NWXjoolI9M0tLeRnTKtsJ0lKSRBex2j+RXrvziWs1H1jpZnpSkx8EkKPrsKY+hmpd1QzCuUH2Z0ul0uv/uCW3zT4LL22c5AAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-0722-7908","institution":"University of Science and Technology of China","correspondingAuthor":true,"prefix":"","firstName":"Zhengjin","middleName":"","lastName":"Yang","suffix":""},{"id":312837600,"identity":"75d6fe8d-eade-457a-9e33-0dec8a59e274","order_by":1,"name":"Junkai Fang","email":"","orcid":"","institution":"University of Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Junkai","middleName":"","lastName":"Fang","suffix":""},{"id":312837601,"identity":"0f6a0aad-640d-49f5-807c-f2cc6d1831a8","order_by":2,"name":"Guozhen Zhang","email":"","orcid":"https://orcid.org/0000-0003-0125-9666","institution":"University of Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Guozhen","middleName":"","lastName":"Zhang","suffix":""},{"id":312837602,"identity":"2c693d1a-2851-4415-b840-974bb732cf90","order_by":3,"name":"Marc-Antoni Goulet","email":"","orcid":"https://orcid.org/0000-0002-9146-6759","institution":"Concordia University","correspondingAuthor":false,"prefix":"","firstName":"Marc-Antoni","middleName":"","lastName":"Goulet","suffix":""},{"id":312837603,"identity":"c0979062-3fbe-4e74-a929-8ee5de5fa314","order_by":4,"name":"Peipei Zuo","email":"","orcid":"https://orcid.org/0000-0001-5043-7188","institution":"University of Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Peipei","middleName":"","lastName":"Zuo","suffix":""},{"id":312837604,"identity":"9b6dc219-16e2-48ce-8f1a-c2af4fd1628a","order_by":5,"name":"Hui Li","email":"","orcid":"","institution":"University of Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Hui","middleName":"","lastName":"Li","suffix":""},{"id":312837605,"identity":"7aac6891-d085-4c48-8d90-433df4a83233","order_by":6,"name":"Jun Jiang","email":"","orcid":"https://orcid.org/0000-0002-6116-5605","institution":"University of Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Jun","middleName":"","lastName":"Jiang","suffix":""},{"id":312837606,"identity":"1e41d928-9652-4589-ab71-4681c66916e8","order_by":7,"name":"Michael Guiver","email":"","orcid":"https://orcid.org/0000-0003-2619-6809","institution":"Tianjin University","correspondingAuthor":false,"prefix":"","firstName":"Michael","middleName":"","lastName":"Guiver","suffix":""},{"id":312837607,"identity":"5ad51da1-0120-4b1b-93a6-89dafce86263","order_by":8,"name":"Tongwen Xu","email":"","orcid":"https://orcid.org/0000-0002-9221-5126","institution":"University of Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Tongwen","middleName":"","lastName":"Xu","suffix":""}],"badges":[],"createdAt":"2024-05-09 05:20:23","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4392718/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4392718/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41467-025-58638-0","type":"published","date":"2025-04-06T04:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":58119408,"identity":"eff6c598-34fb-46e5-ac84-112816458a04","added_by":"auto","created_at":"2024-06-11 11:41:13","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1096355,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSynthesis and characterization of microporous covalent triazine framework membranes. \u003c/strong\u003e(\u003cstrong\u003ea\u003c/strong\u003e) Left panel: schematic showing the 3D interconnected micropore free volume for anion transport. Right panel: Molecular structure and synthesis of the covalent triazine framework membrane QCTF and subsequent protonation or methylation of the triazine ring skeleton, affording P-QCTF and M-QCTF. Coulombic/steric exclusion and intimate ion‒pore wall interactions enable selective and fast anion transport. Red and blue spheres: fixed functional groups or charged triazine rings; green spheres: counterions or charge carrier ions; lightning: ion‒pore wall interactions. (\u003cstrong\u003eb\u003c/strong\u003e) CO\u003csub\u003e2\u003c/sub\u003e adsorption isotherms of QCTF, P-QCTF and M-QCTF at 273 K. (\u003cstrong\u003ec\u003c/strong\u003e) Pore size distributions of QCTF, P-QCTF and M-QCTF derived from CO\u003csub\u003e2\u003c/sub\u003e adsorption isotherms through density functional theory (DFT) calculations. (\u003cstrong\u003ed\u003c/strong\u003e) XPS (N1s) spectra of covalent triazine framework (CTF) membranes: QCTF (top), protonated QCTF (P-QCTF, middle), and methylated QCTF (M-QCTF, bottom).\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4392718/v1/1c9c4ca5b51528ef17e65cac.png"},{"id":58119410,"identity":"fc85c15c-9cfa-41dd-8c11-0814ace3a2fe","added_by":"auto","created_at":"2024-06-11 11:41:13","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":771330,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eIon selectivity and conductivity of microporous covalent triazine framework membranes. (a) \u003c/strong\u003eSchematic showing the transport of anions across rigid micropores within positively charged covalent triazine framework QCTF membranes. Coulombic/steric exclusion and intimate ion‒pore wall interactions enable selective and fast anion transport. Red and blue spheres: fixed functional groups or charged triazine rings; green spheres: counterions or charge carrier ions; blue and gray spheres: positively charged ions with large or small hydrated diameters. The dashed lines indicate ion‒pore wall interactions, while the arrowed lines suggest rejection or transport of ions. (\u003cstrong\u003eb)\u003c/strong\u003e Current‒voltage (\u003cem\u003eI‒V\u003c/em\u003e) curves of the M-QCTF, P-QCTF, QCTF, Selemion® DSV and Selemion®\u003csup\u003e \u003c/sup\u003eAMV membranes under a 10-fold concentration gradient in KCl solution. The intercept at 0 µA correlates to the transmembrane potential as a result of selective ion transport, from which the transference number \u003cem\u003et\u003c/em\u003e\u003csub\u003e\u003cem\u003e-\u003c/em\u003e\u003c/sub\u003e can then be deduced. The diffusion coefficient of BTMAP-Vi (\u003cstrong\u003ec\u003c/strong\u003e) and Cl\u003csup\u003e-\u003c/sup\u003e (\u003cstrong\u003ed\u003c/strong\u003e) across QCTF membranes and commercial membranes, as determined from a two-compartment diffusional H-cell. (\u003cstrong\u003ee) \u003c/strong\u003eCl\u003csup\u003e-\u003c/sup\u003e conductivity plotted as a function of hydration number for the M-QCTF, P-QCTF, QCTF, Selemion® DSV and Selemion® AMV membranes. The conductivity was measured via the four-probe EIS method. Each data point represents the Cl\u003csup\u003e-\u003c/sup\u003e conductivity at an individual temperature: from left to right (or from larger data points to smaller data points), 30‒80 °C, with a 10 °C increment. (\u003cstrong\u003ef\u003c/strong\u003e) The calculated activation energy for Cl\u003csup\u003e-\u003c/sup\u003e conduction (\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ea\u003c/em\u003e\u003c/sub\u003e) across the M-QCTF, P-QCTF, QCTF, Selemion® DSV and Selemion® AMV membranes, as derived from Arrhenius equations. (\u003cstrong\u003eg\u003c/strong\u003e) Comparison on activation energy for QCTF membranes, commercial membranes and those reported previously. The detailed values can be found in Supplementary Table S1.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4392718/v1/563918946e3041cf90d2d09c.png"},{"id":58119413,"identity":"eb45767b-1e25-4b25-9e30-710abe4ead5f","added_by":"auto","created_at":"2024-06-11 11:41:14","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":4791951,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eLow barrier anion transport enabled by ion‒pore wall interactions under confinement. \u003c/strong\u003e(\u003cstrong\u003ea\u003c/strong\u003e) Charge distributions of QCTF (left), P-QCTF (middle), and M-QCTF (right) from restrained electrostatic potential (RESP). The charge values shown can be found in Supplementary Table S9. (\u003cstrong\u003eb\u003c/strong\u003e)\u003cstrong\u003e \u003c/strong\u003eComputed free energy map for the\u003cstrong\u003e \u003c/strong\u003etransport of Cl\u003csup\u003e-\u003c/sup\u003e ions within the QCTF (left), P-QCTF (middle) and M-QCTF (right) membrane matrices. The black or white lines denote the Cl\u003csup\u003e-\u003c/sup\u003e ion transport pathways (1-1 or 1-2-1) with the lowest free energy barrier. (\u003cstrong\u003ec\u003c/strong\u003e) Snapshots taken during simulation, demonstrating the interactions between Cl\u003csup\u003e-\u003c/sup\u003e and the M-QCTF membrane pore walls. Insets denote the specific interactions at positions 1 and 2. The parameters (\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e) represent the distance between the Cl\u003csup\u003e-\u003c/sup\u003e ion and the geometric center of two quaternary ammonium (QA) groups. (\u003cstrong\u003ed\u003c/strong\u003e) \u003csup\u003e19\u003c/sup\u003eF PFG-NMR spectra recorded for membrane samples of Selemion® DSV, QCTF, P-QCTF and M-QCTF immersed in 0.1 M KF solutions. (\u003cstrong\u003ee\u003c/strong\u003e) F\u003csup\u003e-\u003c/sup\u003e self-diffusion coefficients derived from \u003csup\u003e19\u003c/sup\u003eF PFG-NMR spectra (\u003csup\u003e19\u003c/sup\u003eF\u003csup\u003e-\u003c/sup\u003e is used instead of \u003csup\u003e35\u003c/sup\u003eCl\u003csup\u003e-\u003c/sup\u003e because of its superior NMR sensitivity). Error bars are standard deviations derived from three measurements based on three separate membrane samples.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4392718/v1/f304172cd10f70e0c5de324c.png"},{"id":58119411,"identity":"4d10cfd3-ffd3-404f-8ffc-187fe9a86f4a","added_by":"auto","created_at":"2024-06-11 11:41:13","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":704730,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFast charging of pH-neutral AORFBs enabled by the M-QCTF membrane. \u003c/strong\u003e(\u003cstrong\u003ea\u003c/strong\u003e)\u003cstrong\u003e \u003c/strong\u003eSchematic illustration of a pH-neutral BTMAP-Vi/FcNCl AORFB assembled with an M-QCTF membrane. (\u003cstrong\u003eb\u003c/strong\u003e) EIS spectra measured in cells assembled with M-QCTF, Selemion® DSV and Selemion® AMV membranes. A control EIS spectrum was recorded in a cell without a membrane. (\u003cstrong\u003ec\u003c/strong\u003e) Coulombic efficiency (CE), energy efficiency (EE), and capacity of cells assembled with the M-QCTF membrane at various current densities. (\u003cstrong\u003ed\u003c/strong\u003e) Galvanostatic cycling of the BTMAP-Vi/FcNCl cell assembled with the M-QCTF membrane at 400 mA cm\u003csup\u003e-2\u003c/sup\u003e. The electrolyte compositions through \u003cstrong\u003eb\u003c/strong\u003e to \u003cstrong\u003ed\u003c/strong\u003e: the anolyte comprised 5 mL of 0.5 M BTMAP-Vi in 2 M KCl, while the catholyte comprised 10 mL of 0.5 M FcNCl in 2 M KCl. Capacity utilization (\u003cstrong\u003ee\u003c/strong\u003e) and energy efficiency (\u003cstrong\u003ef\u003c/strong\u003e) of pH-neutral AORFBs assembled with Selemion® DSV and Selemion® AMV, AME 115, PIM-TDQTB, or M-QCTF are plotted as a function of current density. Dashed lines and shades are visual guides. The detailed values can be found in Supplementary Table S10.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4392718/v1/30dce3e9e0ba2b5119d4d2fc.png"},{"id":79984721,"identity":"8cf0943d-6edb-4af4-9047-d39d6f840b0c","added_by":"auto","created_at":"2025-04-06 07:06:22","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":10613250,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4392718/v1/119636d1-06a1-4af0-85c1-301bdb6cf893.pdf"},{"id":58120049,"identity":"b3f60098-1d93-4a15-ac98-fed88b69028f","added_by":"auto","created_at":"2024-06-11 11:49:13","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":33161008,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"03supplementarymaterials.docx","url":"https://assets-eu.researchsquare.com/files/rs-4392718/v1/fdca744d6d7790d06986a868.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Rationally synthesized framework polymer membranes enable high selectivity and barrierless anion conduction","fulltext":[{"header":"Main Text","content":"\u003cp\u003eReplicating the extreme selectivity and high permeability of biological ion channels is an enduring challenge for membrane scientists (\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). Beyond the generally-accepted mechanisms of size exclusion and Coulombic repulsion, it is argued that the subtle interactions between ions and channel walls at atomic-scale confinement play a crucial role. These interactions were not clearly elucidated until the fabrication of angstrom-scale slits/capillaries/channels with atomic-scale precision (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe spatial confinement of ion transport down to molecular-sized ion channels magnifies the impact of channel wall interactions and gives rise to exotic transport behavior. For example, hysteretic ion conduction occurs, resulting in an ion memory effect (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e), while the formation of Bjerrum ion pairs causes ionic Coulombic blockade (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). These atypical ion motions are intimately related to the dramatically enhanced material-dependent interactions between hydrated ions and the confining channel walls (\u003cem\u003ee.g.\u003c/em\u003e, electrostatic, adsorption/desorption) (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). For chemically inert and atomically smooth graphite channel walls, K\u003csup\u003e+\u003c/sup\u003e demonstrates a mobility close to that of the value in bulk solutions (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). By applying a voltage bias on the graphite channel, the streaming mobility of K\u003csup\u003e+\u003c/sup\u003e is increased by up to 20 times (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e) and this may be ascribed to the electronic structure change under an external voltage bias (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). It has also been demonstrated that by introducing Li\u003csup\u003e+\u003c/sup\u003e-coordinating functionality within the shape-persistent free volume elements of microporous polymer membranes, Li\u003csup\u003e+\u003c/sup\u003e diffusivity can be greatly enhanced (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e). Similar improvements to Na\u003csup\u003e+\u003c/sup\u003e transport have also been achieved by exploiting the synergy between micropore confinement and ion-membrane interactions (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDespite the considerable improvements in cation transport due to the confinement effect, it is notable that chloride (Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e) mobility experiences significant suppression under confinement. This charge asymmetry is likely due to the slightly different hydration shell configurations between Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e and K\u003csup\u003e+\u003c/sup\u003e(\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). The mobility of Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e under confinement is three times less than that of K\u003csup\u003e+\u003c/sup\u003e, even though Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e and K\u003csup\u003e+\u003c/sup\u003e have similar mobilities in bulk water (7.58\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e vs. 7.86\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e m\u003csup\u003e2\u003c/sup\u003e V\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and hydrated diameters (6.64 \u0026Aring; vs. 6.62 \u0026Aring;) (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). For a more extreme case, Cs\u003csup\u003e+\u003c/sup\u003e and Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e exhibit similar ion-core sizes and hydrated diameters, but Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e exhibits more than three times lower mobility under \u0026Aring;-scale confinement (1.7\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e vs. 6.0\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e m\u003csup\u003e2\u003c/sup\u003e V\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). For chloride salts of high valency cations, the overall Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e mobility decreases to almost zero in single-digit-sized nanopores (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e). A decrease in the mobility of other anions under confinement has also been observed (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). This phenomenon is echoed by the relatively high energy barrier associated with anion exchange membranes that transport chloride ions (see Supplementary Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe transport and selectivity of anions are of critical relevance to applications such as direct seawater electrolysis (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e), solid-state batteries (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e) and redox flow batteries (\u003cspan additionalcitationids=\"CR21 CR22 CR23 CR24\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e). Understanding and overcoming the charge asymmetry effect for anion transport under confinement is therefore essential for enabling these technologies. Here we report the design and synthesis of a series of positively charged (quaternary ammonium cations) covalent triazine framework (QCTF) membranes with nearly the same density of rigid micropores with almost identical pore size distributions. The QCTF membranes exhibit Coulombic repulsion-induced anion selectivity, with a chloride transference number \u003cem\u003et\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u0026minus;\u003c/em\u003e\u003c/sub\u003e of 0.95, and size exclusion-induced rejection of BTMAP-Vi (bis(3-trimethylammonio) propyl viologen tetrachloride) and FcNCl ((ferrocenylmethyl) trimethylammonium chloride), redox-active organic flow battery electrolytes. The cross-membrane BTMAP-Vi diffusion coefficient at 3.1\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;11\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is over 20 times lower than that of commercial membranes. We demonstrate that through on-membrane modification, the charge distribution of the pristine QCTF membrane framework can be regulated by protonation (affording P-QCTF) and methylation (affording M-QCTF), which dramatically alters the interactions between anions and the membrane framework and helps lower the energy barrier for anion transport. The cross-membrane Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e conductivity increased twofold from 13.2 mS cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for QCTF to 25.9 mS cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for M-QCTF at 30\u0026deg;C, and the activation energy for Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e conduction decreased from 20.6 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 13.1 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, lower than any value reported in the literature (see Supplementary Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). \u003csup\u003e19\u003c/sup\u003eF PFG-NMR revealed an increase in the F\u003csup\u003e\u0026minus;\u003c/sup\u003e diffusion coefficient from 0.63\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e m\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for QCTF and 0.93\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e m\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for P-QCTF, to 1.1\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e m\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for M-QCTF which is close to the value in bulk water (1.2\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e m\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). The greater anion conductivity can dramatically improve device performance as exemplified here in an BTMAP-Vi- and FcNCl-based aqueous organic redox flow battery (AORFB) in pH-neutral solutions. The BTMAP-Vi/FcNCl cell configured with the M-QCTF membrane exhibited a high-frequency area-specific resistance (ASR) as low as 0.23 Ω\u0026middot;cm\u003csup\u003e2\u003c/sup\u003e, which enabled charging and discharging of the BTMAP-Vi/FcNCl cell at an extreme current density of 500 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. The prolonged galvanostatic cell cycling at 400 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e maintained a Coulombic efficiency of \u0026gt;\u0026thinsp;99% and a stable energy efficiency of around 60% over the course of 1000 cycles. Notably, the achieved capacity utilization and efficiency with M-QCTF approaches similar values to those of alkaline AORFBs that leverage K\u003csup\u003e+\u003c/sup\u003e as charge-carrying ions, while in otherwise identical cells assembled with QCTF or P-QCTF, an almost 20% lower energy efficiency was observed. This is significant and can be attributed to a dramatic reduction in the contribution of membrane resistance to whole\u0026ndash;cell resistance, e.g., from \u0026gt;\u0026thinsp;70% for the Selemion\u0026reg; AMV membrane to ~\u0026thinsp;25% for M-QCTF (Supplementary Tables S2 and S3). The above results imply a breakthrough in the charge asymmetry effect.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eCovalent triazine framework membranes with tunable pore chemistry\u003c/h2\u003e \u003cp\u003eCovalent triazine framework chemistry gives rise to a wide variety of microporous materials and offers enormous diversity in pore chemistry. We thus synthesized a stand-alone triazine framework membrane from 4,4'-biphenyldicarbonitrile and a derivative of 3-hydroxy-[1,1'-biphenyl]-4,4'-dicarbonitrile bearing a quaternary ammonium moiety via a superacid-catalyzed organic sol‒gel procedure (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea and Supplementary Figures \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e-S4) (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e). The process yields a free-standing membrane (namely, QCTF) with a Young\u0026rsquo;s modulus and tensile strength of 0.91 GPa and 32.0 MPa, respectively (Supplementary Figure S5). The skeletal triazine rings of QCTF were subsequently protonated with HCl or methylated with CH\u003csub\u003e3\u003c/sub\u003eI, affording P-QCTF and M-QCTF, respectively. Overall, we constructed three covalent triazine framework polymers with similar molecular configurations and pore structures that can be processed into hydrophilic, uniform and robust ion-selective membranes via an organo-sol‒gel procedure (Supplementary Figures S6-S8, Supplementary Table S4), but with slightly different and deliberately tailored pore chemistries.\u003c/p\u003e \u003cp\u003eCarbon dioxide (CO\u003csub\u003e2\u003c/sub\u003e) adsorption experiments and molecular simulations were conducted to probe the micropore structure of the covalent triazine framework polymers. CO\u003csub\u003e2\u003c/sub\u003e sorption isotherms measured at 273 K revealed that powder samples of QCTF, P-QCTF, and M-QCTF had similar CO\u003csub\u003e2\u003c/sub\u003e uptake capacities of 16, 15.2, and 14.7 cm\u003csup\u003e3\u003c/sup\u003e g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e STP, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). Notably, QCTF, P-QCTF, and M-QCTF exhibit almost identical pore size distributions, ranging from 0.3 nm to 0.9 nm, as derived from CO\u003csub\u003e2\u003c/sub\u003e adsorption isotherms based on density functional theory (DFT) calculations (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec). These experimental results are further supported by molecular simulations of the 3D framework structure and the computation of CO\u003csub\u003e2\u003c/sub\u003e distributions within the framework structures (Supplementary Figures S9 and S10). This again indicates that QCTF, P-QCTF, and M-QCTF have similar framework structures, interconnected micropores and pore size distributions.\u003c/p\u003e \u003cp\u003eThe amount of charged functional groups (quaternary ammonium groups) within the pristine QCTF membrane, characterized by the ion exchange capacity (IEC, in mmol g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), is 1.20 mmol g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for QCTF (as-designed IEC value is ~\u0026thinsp;1.00 mmol g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). During protonation, approximately 55% of the triazine rings were protonated and the same amount of triazine rings was methylated after methylation, as revealed by X-ray photoelectron spectroscopy (XPS, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). This suggests that P-QCTF and M-QCTF should have identical IEC values, which was confirmed by titration and zeta potential measurements (Supplementary Figure S11).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eIon Transport and Selectivity\u003c/h3\u003e\n\u003cp\u003eDespite the similar framework structure and almost identical pore size/size distributions, our experimental results reflect that cross-membrane ion transport is significantly affected by pore chemistry. We speculate that the difference is synergistically determined by Coulombic/steric effects and specific ion‒pore wall interactions, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea. The current‒voltage (I‒V) curves across the membranes, as measured in a two-compartment diffusional H-cell under a 10-fold concentration gradient KCl solution (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb), reveal a net anion flux, indicating anion selectivity. The anion transference number (\u003cem\u003et\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u0026minus;\u003c/em\u003e\u003c/sub\u003e) calculated for QCTF is 0.940, while the values for protonated QCTF (P-QCTF) and methylated QCTF (M-QCTF) are 0.947 and 0.953, respectively (Supplementary Figure S12). These values suggest the superior anion selectivity of the QCTF membranes compared to that of commercial anion exchange membranes (AEMs). This result is reasonable considering the Coulombic repulsion of the \u0026lt;\u0026thinsp;1 nm pore channel within the QCTF membranes.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe measured transference numbers align with the cross-membrane permeation/diffusion rates for BTMAP-Vi (a redox-active organic cation) and Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed, Supplementary Figures S13-S15, Supplementary Tables S5-S6), which are dramatically different in size. Compared with commercial AEMs (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec), all the QCTF membranes exhibited superior blocking capabilities toward BTMAP-Vi. The diffusion coefficients of BTMAP-Vi across the QCTF and the P-QCTF were determined to be 4.5\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;11\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 3.4\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;11\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. These values are at least one order of magnitude smaller than those of commercial AEMs. Note that the value further decreases to 3.1\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;11\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for M-QCTF, a value that is over 20 times smaller than that of Selemion\u0026reg; DSV. The diffusion coefficients of Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e through the QCTF and P-QCTF are 1.8\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 2.6\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. By contrast, commercial anion-selective membranes demonstrated Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e diffusion coefficients at least one order of magnitude smaller than those of QCTF membranes. Surprisingly, the Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e diffusion coefficient measured for M-QCTF reached 3.0\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which is nearly 2 times that for the QCTF membrane (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed). A comparison of the Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e diffusion coefficients and the Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e/BTMAP-Vi selectivity for QCTF membranes, commercial AEMs and previously reported membranes implies that these framework membranes can simultaneously deliver fast ion permeation and high selectivity, overcoming the usual tradeoff observed for many ion exchange membranes (Supplementary Figure S16 and Supplementary Table S6).\u003c/p\u003e \u003cp\u003eThe fast Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e transport across the triazine framework membranes is further supported by the membrane conductivity measurements. Compared with commercial AEMs, triazine framework membranes show high Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e conductivity at relatively low hydration numbers (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee, Supplementary Figure S17 and Supplementary Tables S7-S8). The Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e conductivity of QCTF, as measured by four-point electrochemical impedance spectroscopy (EIS), is 13.2 mS cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 30.0\u0026deg;C and approaches 42.0 mS cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 80\u0026deg;C at low hydration numbers (3.5 at 30\u0026deg;C, 4.4 at 80\u0026deg;C). In comparison, the Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e conductivity of P-QCTF is 20.0 mS cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 30\u0026deg;C and increases to 48.4 mS cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 80\u0026deg;C. We find that the Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e conductivity of M-QCTF is 26.0 at 30.0\u0026deg;C, which is nearly twice that of QCTF, and reaches 53.0 mS cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 80\u0026deg;C. The activation energy (\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ea\u003c/em\u003e\u003c/sub\u003e) for Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e conduction across the QCTF membrane is 20.6 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, as derived from the conductivities at various temperatures (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef and Supplementary Figure S18), contrasting an \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ea\u003c/em\u003e\u003c/sub\u003e of 12.9 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for K\u003csup\u003e+\u003c/sup\u003e transport across an otherwise identical membrane with sulfonate functional groups (ref 14). Surprisingly, the \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ea\u003c/em\u003e\u003c/sub\u003e value for M-QCTF is as low as 13.1 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which is nearly half that of QCTF and lower than any value reported in the literature (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eg and Supplementary Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). Considering the similar framework structure and almost identical pore size/size distributions, this significant result indicates that the methylation of triazine rings alters the transport energy barrier for Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e ions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eDue to the aforementioned results, we conclude that electrostatic interactions alone cannot explain the differences in Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e diffusion coefficients, Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e conductivity or activation energy for cross-membrane Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e transport. To unravel why methylation of the triazine ring promotes fast Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e conduction, compared to the protonated triazine ring in P-QCTF and the charge-neutral triazine ring in QCTF, the charge distribution and the Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e transport routes within the matrix of the triazine framework membranes were portrayed based on molecular simulations, and the two-dimensional free-energy landscapes were computed according to current methodology (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e). Our calculations show that the charge distributions of triazine framework membranes vary dramatically after protonation and methylation (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea, Supplementary Figure S19). The most even charge distribution is observed for M-QCTF. We speculate that the variation in charge distribution alters the interactions between anions and the membrane frameworks and helps establish low-energy-barrier pathways for anion transport. This is supported by free energy calculations for Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e conduction (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb). The simulation results showed that Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e can interact with quaternary ammonium (QA) groups (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec, Supplementary Figures S20 and S21) and lower the free energy, but an energy barrier must be overcome for Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e ions to approach adjacent QA groups. The energy barrier for Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e conduction is the highest for QCTF (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb, left panel) and decreases when the triazine ring is protonated (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb, middle panel), while methylation of the triazine ring in M-QCTF improves the diffusivity of Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e within the framework and creates a Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e diffusion pathway with the lowest energy barrier (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb, right panel). We suspect that the synergy of electrostatic interactions between Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e and the methylated triazine ring and the change in electron density along the Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e diffusion path after methylation may account for the emergence of the low-energy-barrier diffusion pathway.\u003c/p\u003e \u003cp\u003eMolecular simulation results are further supported by measurements of transmembrane F\u003csup\u003e\u0026minus;\u003c/sup\u003e diffusion coefficients via \u003csup\u003e19\u003c/sup\u003eF pulsed-field gradient-stimulated-echo nuclear magnetic resonance (\u003csup\u003e19\u003c/sup\u003eF PFG-NMR; \u003csup\u003e19\u003c/sup\u003eF was selected owing to its higher sensitivity compared with \u003csup\u003e35\u003c/sup\u003eCl).\u003csup\u003e19\u003c/sup\u003eF PFG-NMR revealed two separate F\u003csup\u003e\u0026minus;\u003c/sup\u003e signals for Selemion\u0026reg; DSV and Selemion\u0026reg; AMV membranes (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed and Supplementary Figure S22), with the upfield signal corresponding to free F\u003csup\u003e\u0026minus;\u003c/sup\u003e in water (located at the same position as that in 0.1 M KF aqueous solution) and the downfield signal corresponding to associated F\u003csup\u003e\u0026minus;\u003c/sup\u003e within the membrane. In contrast, only the upfield signal was observed for all three triazine framework membranes (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed), which is an indication of freely exchangeable F\u003csup\u003e\u0026minus;\u003c/sup\u003e within the membrane, with slight variations in the \u003csup\u003e19\u003c/sup\u003eF chemical shifts. By fitting the echo profiles with the Stejskal‒Tanner equation (Supplementary Figure S23), the derived F\u003csup\u003e\u0026minus;\u003c/sup\u003e diffusion coefficients within the P-QCTF and QCTF are 0.93\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e m\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 0.63\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e m\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee). The value reaches 1.1\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e m\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for M-QCTF, almost a twofold increase compared to that for QCTF. Notably, this value is 12.8 times that of Selemion\u0026reg; AMV and 10.8 times that of Selemion\u0026reg; DSV (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee and Supplementary Figure S23) and approaches the measured diffusion coefficient of F\u003csup\u003e\u0026minus;\u003c/sup\u003e in water (1.2\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e m\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; Supplementary Figure S23). In summary, by tailoring the pore chemistry of framework membranes, intimate ion‒pore wall interactions provide a low-energy-barrier diffusion pathway for anions. Taken together with the Coulombic/steric exclusion by the charged framework micropores, the triazine framework membranes, particularly M-QCTF, will be of interest in applications demanding extremely fast and highly selective transport of anions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eTriazine framework membrane powers fast-charging AORFBs\u003c/h3\u003e\n\u003cp\u003eThe extremely fast and highly selective anion (particularly chloride ions) conduction through chemically tuned triazine framework membranes is desirable in electrochemical devices, such as aqueous organic redox flow batteries. As a proof of concept, we configured pH-neutral AORFBs with BTMAP-Vi/FcNCl as the redox-active organic electrolyte couple and triazine framework membranes as the ion-conducting membranes, while Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e ions were transported back and forth as charge carriers (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). At an electrolyte concentration of 0.1 M, EIS of the BTMAP-Vi/FcNCl cells assembled with QCTF or P-QCTF showed area-specific membrane resistances (ASRs) of 0.63 Ω cm\u003csup\u003e2\u003c/sup\u003e and 0.53 Ω cm\u003csup\u003e2\u003c/sup\u003e, respectively (Supplementary Figures S24-S25). An otherwise identical cell assembled with M-QCTF showed an ASR of 0.37 Ω cm\u003csup\u003e2\u003c/sup\u003e (Supplementary Figure S26), which is almost twofold lower than that of the QCTF membrane. This finding aligns with the high conductivity of M-QCTF (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee, \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb), which enables charging of the BTMAP-Vi/FcNCl cells at extreme current densities. For example, at 200 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, BTMAP-Vi/FcNCl with M-QCTF exhibited an energy efficiency (EE) of over 60% (Supplementary Figure S26). In contrast, the control BTMAP-Vi/FcNCl cells assembled with Selemion\u0026reg; DSV or Selemion\u0026reg; AMV could not operate at this current density due to the immediate voltage cutoff. At lower current densities ranging from 20 to 80 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, the reported energy efficiency for the control cells drops from 89.4\u0026ndash;65.9% for Selemion\u0026reg; DSV or from 80.0\u0026ndash;26.6% for Selemion\u0026reg; AMV (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAt a higher electrolyte concentration of 0.5 M, BTMAP-Vi/FcNCl with M-QCTF demonstrated an even lower ASR of 0.23 Ω cm\u003csup\u003e2\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb), a much lower value than that for Selemion\u0026reg; DSV or Selemion\u0026reg; AMV. The rate performance of the cell reveals an EE of 49.7% and a capacity utilization of 58.8% at an extreme current density of 500 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec). Compared with the most recent report of an AEM (MTCP-50 membrane, with the optimal ratio 1:1 of \u003cem\u003em\u003c/em\u003e-terphenyl to \u003cem\u003ep\u003c/em\u003e-terphenyl) for pH-neutral AORFBs at 0.5 M (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e), M-QCTF achieved a much greater energy efficiency (76.9% vs. 60.1%) and capacity utilization (94.3% vs. 63.7%) at the same current density of 200 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. Notably, alkaline AORFBs that utilize K\u003csup\u003e+\u003c/sup\u003e as charge-carrying ions assembled with a cation exchange membrane (SCTF-BP), which allows cation diffusion close to the value in bulk electrolyte, exhibit an EE of 50.4% and a capacity utilization of 62% at 500 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. The current results demonstrate a similar efficiency for Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e transport and therefore suggest a breakthrough in the charge asymmetry effect.\u003c/p\u003e \u003cp\u003eRobust and exceptional cell performance was observed during long-term galvanostatic cycling of over 2000 cycles at 200 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e (0.1 M electrolyte concentration, Supplementary Figure S26) and over 1000 cycles at 400 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e (0.5 M electrolyte concentration, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed). Comparisons of the EE and capacity utilization against the current density shows consistently superior battery performance over multiple cell cycling experiments for the BTMAP-Vi/FcNCl cells with M-QCTF, compared to the pH-neutral AORFB with different membranes (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee, \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef and Supplementary Table S10).\u003c/p\u003e \u003cp\u003eThis work demonstrates that chloride and fluoride anions traverse the M-QCTF membrane with a very low energy barrier, leading to exceptional flow battery performance. This significant development can be applied more broadly to designing anion exchange membranes for other technologies such as CO\u003csub\u003e2\u003c/sub\u003e electrolysers (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e) and ion-capture electrodialysis (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e). Although the anion diffusion constants within the developed membranes are approaching the theoretical limit of the bulk electrolyte solution, we expect further improvements in overall conductivity to be achievable by eliminating micropore tortuosity and creating perfectly aligned micropore channels with monodispersed pore size distributions.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was funded by the National Key R\u0026amp;D Program of China (2021YFB4000302) and the National Natural Science Foundation of China (Grant/Award No. U20A20127, 52021002). This work was partially carried out at the Instruments Center for Physical Science, University of Science and Technology of China.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials. Source data are available on reasonable request from the corresponding author.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eD. A. Doyle\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, The structure of the potassium channel: molecular basis of K\u003csup\u003e+\u003c/sup\u003e conduction and selectivity. \u003cem\u003eScience\u003c/em\u003e \u003cstrong\u003e280\u003c/strong\u003e, 69 (1998).\u003c/li\u003e\n \u003cli\u003eH. B. Park\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Maximizing the right stuff: the trade-off between membrane permeability and selectivity. \u003cem\u003eScience\u003c/em\u003e \u003cstrong\u003e356\u003c/strong\u003e, eaab0530 (2017).\u003c/li\u003e\n \u003cli\u003eY. J. Lim\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, The coming of age of water channels for separation membranes: from biological to biomimetic to synthetic. \u003cem\u003eChem. Soc. Rev.\u003c/em\u003e \u003cstrong\u003e51\u003c/strong\u003e, 4537-4582 (2022).\u003c/li\u003e\n \u003cli\u003eB. Radha\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Molecular transport through capillaries made with atomic-scale precision. \u003cem\u003eNature\u003c/em\u003e \u003cstrong\u003e538\u003c/strong\u003e, 222-225 (2016).\u003c/li\u003e\n \u003cli\u003eA. Bhardwaj\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Fabrication of angstrom-scale two-dimensional channels for mass transport. \u003cem\u003eNat. Protoc.\u003c/em\u003e \u003cstrong\u003e19\u003c/strong\u003e, 240-280 (2023).\u003c/li\u003e\n \u003cli\u003eT. Xiong\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Neuromorphic functions with a polyelectrolyte-confined fluidic memristor. \u003cem\u003eScience\u003c/em\u003e \u003cstrong\u003e379\u003c/strong\u003e, 156-161 (2023).\u003c/li\u003e\n \u003cli\u003eP. Robin\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Long-term memory and synapse-like dynamics in two-dimensional nanofluidic channels. \u003cem\u003eScience\u003c/em\u003e \u003cstrong\u003e379\u003c/strong\u003e, 161-167 (2023).\u003c/li\u003e\n \u003cli\u003eN. Kavokine\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Ionic Coulomb blockade as a fractional Wien effect. \u003cem\u003eNat. Nanotechnol.\u003c/em\u003e \u003cstrong\u003e14\u003c/strong\u003e, 573-578 (2019).\u003c/li\u003e\n \u003cli\u003eP. Robin\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Modeling of emergent memory and voltage spiking in ionic transport through angstrom-scale slits. \u003cem\u003eScience\u003c/em\u003e \u003cstrong\u003e373\u003c/strong\u003e, 687-691 (2021).\u003c/li\u003e\n \u003cli\u003eA. Esfandiar\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Size effect in ion transport through angstrom-scale slits. \u003cem\u003eScience\u003c/em\u003e \u003cstrong\u003e358\u003c/strong\u003e, 511-513 (2017).\u003c/li\u003e\n \u003cli\u003eT. Mouterde\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Molecular streaming and its voltage control in \u0026aring;ngstr\u0026ouml;m-scale channels. \u003cem\u003eNature\u003c/em\u003e \u003cstrong\u003e567\u003c/strong\u003e, 87-90 (2019).\u003c/li\u003e\n \u003cli\u003eF. Chen\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Inducing electric current in graphene using Ionic flow. \u003cem\u003eNano Lett.\u003c/em\u003e \u003cstrong\u003e23\u003c/strong\u003e, 4464-4470 (2023).\u003c/li\u003e\n \u003cli\u003eM. J. Baran\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Diversity-oriented synthesis of polymer membranes with ion solvation cages. \u003cem\u003eNature\u003c/em\u003e \u003cstrong\u003e592\u003c/strong\u003e, 225-231 (2021).\u003c/li\u003e\n \u003cli\u003eP. Zuo\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Near-frictionless ion transport within triazine framework membranes. \u003cem\u003eNature\u003c/em\u003e \u003cstrong\u003e617\u003c/strong\u003e, 299-305 (2023).\u003c/li\u003e\n \u003cli\u003eY. Zhao\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Differentiating solutes with precise nanofiltration for next generation environmental separations: a review. \u003cem\u003eEnviron. Sci. Technol.\u003c/em\u003e \u003cstrong\u003e55\u003c/strong\u003e, 1359-1376 (2021).\u003c/li\u003e\n \u003cli\u003eS. Goutham\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Beyond steric selectivity of ions using \u0026aring;ngstr\u0026ouml;m-scale capillaries. \u003cem\u003eNat. Nanotechnol.\u003c/em\u003e \u003cstrong\u003e18\u003c/strong\u003e, 596-601 (2023).\u003c/li\u003e\n \u003cli\u003eJ. Ma\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Multivalent ion transport through a nanopore. \u003cem\u003eJ. Phys. Chem. C\u003c/em\u003e \u003cstrong\u003e126\u003c/strong\u003e, 14661-14668 (2022).\u003c/li\u003e\n \u003cli\u003eH. Xie\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, A membrane-based seawater electrolyser for hydrogen generation. \u003cem\u003eNature\u003c/em\u003e \u003cstrong\u003e612\u003c/strong\u003e, 673-678 (2022).\u003c/li\u003e\n \u003cli\u003eG. Karkera\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, A structurally flexible halide solid electrolyte with high ionic conductivity and air processability. \u003cem\u003eAdv. Energy Mater.\u0026nbsp;\u003c/em\u003e\u003cstrong\u003e13\u003c/strong\u003e, 2300982 (2023).\u003c/li\u003e\n \u003cli\u003eS. Pang\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Biomimetic amino acid functionalized phenazine flow batteries with long lifetime at near‐neutral pH. \u003cem\u003eAngew. Chem. Int. Edit.\u003c/em\u003e \u003cstrong\u003e60\u003c/strong\u003e, 5289-5298 (2021).\u003c/li\u003e\n \u003cli\u003eW. Song\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Upscaled production of an ultramicroporous anion-exchange membrane enables long-term operation in electrochemical energy devices. \u003cem\u003eNat. Commun.\u003c/em\u003e \u003cstrong\u003e14\u003c/strong\u003e, 2732 (2023).\u003c/li\u003e\n \u003cli\u003eM. E. Carrington\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Associative pyridinium electrolytes for air-tolerant redox flow batteries. \u003cem\u003eNature\u003c/em\u003e \u003cstrong\u003e623\u003c/strong\u003e, 949-955 (2023).\u003c/li\u003e\n \u003cli\u003eP. Xiong\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, A chemistry and microstructure perspective on ion‐conducting membranes for redox flow batteries. \u003cem\u003eAngew. Chem. Int. Edit.\u003c/em\u003e \u003cstrong\u003e60\u003c/strong\u003e, 24770-24798 (2021).\u003c/li\u003e\n \u003cli\u003eB. Hu\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Long-cycling aqueous organic redox flow battery (AORFB) toward sustainable and safe energy storage. \u003cem\u003eJ. Am. Chem. Soc.\u0026nbsp;\u003c/em\u003e\u003cstrong\u003e139\u003c/strong\u003e, 1207-1214 (2017).\u003c/li\u003e\n \u003cli\u003eJ. Luo\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, A \u0026pi;‐conjugation extended viologen as a two‐electron storage anolyte for total organic aqueous redox flow batteries. \u003cem\u003eAngew. Chem. Int. Edit.\u003c/em\u003e \u003cstrong\u003e57\u003c/strong\u003e, 231-235 (2017).\u003c/li\u003e\n \u003cli\u003eX. Zhu\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, A superacid-catalyzed synthesis of porous membranes based on triazine frameworks for CO\u003csub\u003e2\u003c/sub\u003e separation. \u003cem\u003eJ. Am. Chem. Soc.\u003c/em\u003e \u003cstrong\u003e134\u003c/strong\u003e, 10478-10484 (2012).\u003c/li\u003e\n \u003cli\u003eH. Li\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Ultra-microporous anion conductive membranes for crossover-free pH-neutral aqueous organic flow batteries. \u003cem\u003eJ. Membr. Sci.\u003c/em\u003e \u003cstrong\u003e668\u003c/strong\u003e, 121195 (2023).\u003c/li\u003e\n \u003cli\u003eD. A. Salvatore\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Designing anion exchange membranes for CO\u003csub\u003e2\u003c/sub\u003e electrolysers. \u003cem\u003eNat. Energy\u003c/em\u003e \u003cstrong\u003e6\u003c/strong\u003e, 339-348 (2021).\u003c/li\u003e\n \u003cli\u003eA. A. Uliana\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e, Ion-capture electrodialysis using multifunctional adsorptive membranes. \u003cem\u003eScience\u003c/em\u003e \u003cstrong\u003e372\u003c/strong\u003e, 296-299 (2021).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-4392718/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4392718/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe understanding gleaned from studying ion transport within the interaction confinement regime enables the near-frictionless transport of cations (\u003cem\u003ee.g.,\u003c/em\u003e Na\u003csup\u003e+\u003c/sup\u003e/K\u003csup\u003e+\u003c/sup\u003e). However, anion transport (\u003cem\u003ee.g.,\u003c/em\u003e Cl\u003csup\u003e-\u003c/sup\u003e) is suppressed under confinement because of the different polarization of water molecules around cations and anions, also known as the charge asymmetry effect. Here we report the rational synthesis of anion-selective framework polymer membranes having similar densities of subnanometer-sized pores with nearly identical micropore size distributions, which overcome the charge asymmetry effect and promote barrierless anion conduction. We find that anion transport within the micropore free volume elements can be dramatically accelerated by regulating the pore chemistry, which lowers the energy barrier for anion transport, leading to an almost twofold increase in Cl\u003csup\u003e-\u003c/sup\u003e conductivity and barrierless F\u003csup\u003e-\u003c/sup\u003e diffusion. The resultant membrane enables an aqueous organic redox flow battery that utilizes Cl\u003csup\u003e-\u003c/sup\u003e ions as charge carriers to operate at extreme current densities and delivers competitive performance to counterparts where K\u003csup\u003e+\u003c/sup\u003e ions are charge carriers. These results may benefit broadly electrochemical devices and inspire single-species selectivity with separation membranes that exploit controlled or chemically gated ion/molecule transport.\u003c/p\u003e","manuscriptTitle":"Rationally synthesized framework polymer membranes enable high selectivity and barrierless anion conduction","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-11 11:41:08","doi":"10.21203/rs.3.rs-4392718/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"b74a5ce3-ed6b-4f21-a84e-0018acabc6cb","owner":[],"postedDate":"June 11th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":33071475,"name":"Physical sciences/Chemistry/Materials chemistry/Soft materials/Polymers"},{"id":33071476,"name":"Physical sciences/Engineering/Chemical engineering"},{"id":33071477,"name":"Physical sciences/Chemistry/Energy"}],"tags":[],"updatedAt":"2025-04-06T07:06:07+00:00","versionOfRecord":{"articleIdentity":"rs-4392718","link":"https://doi.org/10.1038/s41467-025-58638-0","journal":{"identity":"nature-communications","isVorOnly":false,"title":"Nature Communications"},"publishedOn":"2025-04-06 04:00:00","publishedOnDateReadable":"April 6th, 2025"},"versionCreatedAt":"2024-06-11 11:41:08","video":"","vorDoi":"10.1038/s41467-025-58638-0","vorDoiUrl":"https://doi.org/10.1038/s41467-025-58638-0","workflowStages":[]},"version":"v1","identity":"rs-4392718","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4392718","identity":"rs-4392718","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}