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The idea of spatial confinement has gained widespread interest in myriad applications. Especially, the confined short hydrogen-bond (SHB) network could afford an attractive opportunity to enable proton transfer in a nearly barrierless manner, but its practical implementation has been challenging. Herein, we report a SHB network confined on the surface of ionic covalent organic framework (COF) membranes decorated by densely and uniformly distributed hydrophilic ligands. Combined experimental and theoretical evidences have pointed to the confinement of water molecules allocated to each ligand, achieving the local enrichment of hydronium ions and the concomitant formation of SHBs in water-hydronium domains. These overlapped water-hydronium domains create an interconnected SHB network, which yields an unprecedented ultrahigh proton conductivity of 1389 mS cm−1 at 90 °C, 100% relative humidity. When hydronium ions are enriched in confined water, short hydrogen bonds (SHBs) form due to the constrained space of excess protons between pairs of water molecules. Here authors demonstrate a SHB network confined on the surface of ionic COF membranes with tunable -SO3H groups, with proton conductivity of 1389 mS cm-1 at 90 oC. [ABSTRACT FROM AUTHOR]

Ionic covalent organic framework membranes (iCOFMs) hold great promise in ion conduction-relevant applications because the high content and monodispersed ionic groups could afford superior ion conduction. The key to push the upper limit of ion conductivity is to maximize the ion exchange capacity (IEC). Here, we explore iCOFMs with a superhigh ion exchange capacity of 4.6 mmol g−1, using a dual-activation interfacial polymerization strategy. Fukui function is employed as a descriptor of monomer reactivity. We use Brønsted acid to activate aldehyde monomers in organic phase and Brønsted base to activate ionic amine monomers in water phase. After the dual-activation, the reaction between aldehyde monomer and amine monomer at the water-organic interface is significantly accelerated, leading to iCOFMs with high crystallinity. The resultant iCOFMs display a prominent proton conductivity up to 0.66 S cm−1, holding great promise in ion transport and ionic separation applications. Covalent organic framework-based membranes are highly tunable materials with potential use in a variety of applications. Here the authors report a dual-activation interfacial polymerization strategy to prepare ionic covalent organic framework membranes with high ion exchange capacity. [ABSTRACT FROM AUTHOR]

Covalent organic framework (COF) membranes hold potential for widespread applicability, but scalable fabrication is challenging. Here, we demonstrate the disorder‐to‐order transformation from amorphous polymeric membrane to crystalline COF membrane via monomer exchange. Solution processing is used to prepare amorphous membrane and the replacing monomer is selected based on the chemical and thermodynamical stability of the final framework. Reversible imine bonds allow the extraneous monomers to replace the pristine monomers within amorphous membrane, driving the transformation from disordered network to ordered framework. Incorporation of intramolecular hydrogen bonds enables the crystalline COF to imprint the amorphous membrane morphology. The COF membranes harvest proton conductivity up to 0.53 S cm−1 at 80 °C. Our strategy bridges amorphous polymeric and crystalline COF membranes for large‐scale fabrication of COF membranes and affords guidance on materials processing. [ABSTRACT FROM AUTHOR]

Ionic covalent organic framework (iCOF) membranes are attractive for a myriad of applications. Here, we report a mechanochemistry-based solid-state synthesis method to fabricate iCOF membranes with simplicity, scalability and sustainability. Time-dependent experiments reveal that the iCOF membrane formation process includes the structural transformation from disorder to order and the morphology change to the dense structure formed by the restacking of nanosheet-like crystallites simultaneously. The obtained free-standing iCOF membranes demonstrate high ion exchange capacity, mechanical strength and comparable proton conductivity, benefiting from the rigid crystalline framework structure and one-dimensional channels decorated with abundant proton-conducting sites. This work paves the way for synthesis of iCOF membranes in a simple and environmentally friendly manner. [Display omitted] • Ionic COF membrane was obtained via mechanochemistry-based solid-state synthesis. • The COF membrane exhibits high mechanical strength and proton conductivity. • Time-dependent experiments were conducted to reveal the membrane formation process. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) with long-range ordered, rigid, and tailor-made nanochannels hold great promise for energy-related applications. Here, we fabricate COF membranes with one-dimensional charged nanochannels using ionic COF nanosheets decorated with sulfonic acid groups. The free-standing and robust COF membrane exhibits enhanced proton conductivity and suppressed methanol permeability compared to the benchmark Nafion membrane. More interestingly, the methanol permeability of the COF membrane remains almost constant in a wide range of methanol concentrations (5.35 × 10−7 cm2 s−1 for the 2 M methanol/water mixture and 5.44 × 10−7 cm2 s−1 for the neat methanol). All-atomistic dynamics simulations indicate that the diffusio-osmotic effect arising from the charged nanochannels can account for the low and nearly constant methanol permeability of the COF membranes. These findings suggest that the ionic COF membranes can find potential applications in direct methanol fuel cell with high methanol concentrations, and meanwhile shed light on the mass transport mechanism in the charged, rigid and ordered nanochannels. [Display omitted] ● Oriented COF membrane with charged, rigid and ordered nanochannels was fabricated. ● The ionic COF membrane exhibits a low and nearly constant methanol permeability. ● The proton conductivity of COF membrane is much higher than the benchmark membrane. ● Molecular dynamics simulation was conducted to reveal the mass transport mechanism. [ABSTRACT FROM AUTHOR]

The design of new types of proton-conductive materials with high proton conductivity has sparked tremendous interest. Covalent organic framework (COF), a new category of porous crystalline materials possessing well-defined porosity and tunable functionality, holds great potential as next-generation proton conductors. Here, triazole COF loaded with phosphotungstic acid (HPW@COF) has been incorporated into sulfonated poly(ether ether ketone) (SPEEK) matrix to fabricate SPEEK/HPW@COF composite membranes. The one-dimensional channels of COF lined with protonated triazole (triazolium cations) by hydroscopic HPW and neutral triazole as well as counter anions (PO 40 W 12 3−) could act as proton-donors and -acceptors forming interconnected hydrogen-bonding networks, thus greatly facilitating proton conduction via Grotthuss-type mechanism particularly under low RH. Accordingly, SPEEK/HPW@COF displayed 35.5 times higher proton conductivity than the plain SPEEK at 65 °C, 40% RH. Moreover, the proton conductivity of SPEEK/HPW@COF remained constant during soaking in water for 15 days, indicating the excellent immobilization of HPW due to the electrostatic interaction between basic nitrogen sites and HPW as well as the confinement effect of microporous COF channels. These results demonstrated that N-heterocycles functionalized COFs gave great promise as effective hosts to encapsulate proton carriers. Unlabelled Image • Triazole covalent organic framework was promising host to immobilize proton carriers. • The amphoteric triazole groups and hydroscopic phosphotungstic acid facilitated proton transport. • The composite membrane displayed enhanced proton conductivity under low relative humidity. [ABSTRACT FROM AUTHOR]

[Display omitted] • NUS-9 nanosheets with well-defined sulfonic acid groups possess intrinsic proton conductivity. • DNA with plentiful linear arranged phosphate groups provide extrinsic proton-conducting sites. • Synergism of orderly intrinsic and extrinsic proton-conducting sites facilitates the proton conduction. • DNA@COF-X membranes exhibit enhanced proton conductivity in different humidity. Development of high proton-conducting membranes is the major demand in energy conversion, sensing, and catalysis. The emerging ionic covalent organic frameworks (iCOFs) with abundant and well-arranged proton-conducting groups offer new materials for efficient proton conduction. However, the poor processability of iCOFs makes it difficult to fabricate defect-free membranes. Herein, we use the interfacial reaction method to synthesize high crystalline iCOF nanosheets (NUS-9) which are then processed into defect-free membranes by vacuum-assisted assembly method. The plenty of intrinsic orderly aligned sulfonic acid groups in the iCOF skeletons endows the nanosheets with intrinsic high proton conductivity. Furthermore, the deoxyribonucleic acid molecules (DNA) with sequential linear arranged phosphate groups are intercalated into the iCOF membrane. The synergetic effect of orderly intrinsic and extrinsic proton-conducting sites gives the resulting DNA@iCOF membranes high proton conductivity of up to 494.7 mS cm−1 (98% RH, 80 °C), which is among the highest values of the state-of-the-art COF-based proton conductors. Besides, it also retains high conductivity over a wide range of RH (40–100%) and temperature (30−80 °C). [ABSTRACT FROM AUTHOR]

A type of sulfonated covalent organic framework nanosheets (TpPa-SO 3 H) was synthesized via interfacial polymerization and incorporated into sulfonated poly (ether ether ketone) (SPEEK) matrix to prepare proton exchange membranes (PEMs). The densely and orderly arranged sulfonic acid groups in the rigid skeleton of the TpPa-SO 3 H nanosheets, together with their high-aspect-ratio and well-defined porous structure provide proton-conducting highways in the membrane. The doping of TpPa-SO 3 H nanosheets led to an increased ion exchange capacity up to 2.34 mmol g−1 but a 2-folds reduced swelling ratio, remarkably mitigating the trade-off between high IEC and excessive swelling ratio. Based on the high IEC and orderly arranged proton-conducting sites, the SPEEK/TpPa–SO 3 H–5 membrane exhibited the maximum proton conductivity of 0.346 S cm−1 at 80 °C, 1.91-folds higher than the pristine SPEEK membrane. The mechanical strength of the composite membrane was also improved by 2.05-folds–74.5 MPa. The single H 2 /O 2 fuel cell using the SPEEK/TpPa–SO 3 H–5 membrane presented favorable performance with an open voltage of 1.01 V and a power density of 86.54 mW cm−2. [Display omitted] • COF nanosheets with intrinsic proton conductivity are blended with SPEEK matrix. • Densely and orderly arranged –SO 3 H on COF nanosheets offer proton-conducting pathways. • Proton conductivity and mechanical strength of hybrid membranes are enhanced. [ABSTRACT FROM AUTHOR]

Developing sulfonated poly (ether ether ketone) (SPEEK)-based proton exchange membrane with both high proton conductivity and robust mechanical stability is desired for proton exchange membrane fuel cell (PEMFC). Here, a type of phosphoric acid porous organic polymer (PAPOP) with high‐density phosphoric acid (-PO 3 H 2) groups and microporous structure was synthesized and incorporated into SPEEK matrix. The porous skeleton bonding -PO 3 H 2 groups of PAPOP reduced the proton transfer activation energy by providing additional proton conduction pathways. The rigid backbone of PAPOP and its good compatibility with SPEEK increased the mechanical strength of the membrane. The hybrid membrane achieves greatly enhanced proton conductivity up to 417.0 mS cm−1 (80 °C, 100% RH) and high tensile strength of 120.6 MPa. The maximum power density of fuel cell with the hybrid membrane exhibits two times increase compared with the control membrane. [Display omitted] • Phosphoric acid porous organic polymer (PAPOP) was prepared. • PAPOP was incorporated into SPEEK matrix to prepare hybrid membranes. • PAPOP as extra proton carrier formed low-energy-barrier proton transfer pathways. • The membrane showed high proton conductivity of 417.0 mS cm−1 and tensile strength of 120.6 MPa. [ABSTRACT FROM AUTHOR]

Proton exchange membranes (PEMs) have triggered growing attention in energy-related applications due to their fundamental and technological significance. In this work, silica-based nanoscale ionic materials (NIMs-SiO 2) were synthesized and incorporated into sulfonated poly (ether-ether-ketone) (SPEEK) to prepare nanocomposite membranes. NIMs-SiO 2 could not only provide extra proton transfer sites, but also enhanced the hydrophilicity of the membranes, leading to decrease of the activation energy. The nano-scale size (7 nm) and the functional groups of the NIMs-SiO 2 lead to good interfacial adhesion with SPEEK, improving the mechanical properties of the membranes. Consequently, SPEEK/NIMs-SiO 2 (5) exhibited the highest proton conductivity and peak power density, which were 1.92 and 1.51 folds higher than the pristine SPEEK membranes, respectively. The results showed the nanocomposite membranes had potential as alternative proton exchange membranes for corresponding devices. Unlabelled Image • 7 nm silica-based nanoscale ionic materials were synthesized with multifunctionalization. • The nanocomposite membrane displayed remarkably enhanced proton conductivity. • The mechanical property had a significant promotion. [ABSTRACT FROM AUTHOR]