Phosphorylated Covalent Organic Framework Membranes Toward Ultrafast Single Lithium-Ion Transport.

Developing all-solid-state electrolytes, the chips for lithium-metal batteries, with superior electrochemical and mechanical properties awaits the disruptive materials. Herein, ionic covalent organic framework membranes are explored as solid-state electrolytes for single Li conduction. In the membrane, the anion groups act as Li transporter, determining Li binding capacity and releasing ability, whereas the oxygen-containing groups act as Li co-transporter, creating relay sites between adjacent Li transporters for rapid hopping.

Manipulation of Cationic Group Density in Covalent Organic Framework Membranes for Efficient Anion Transport.

Anion exchange membranes with high anion conductivity are highly desired for electrochemical applications. Increasing ion exchange capacity is a straightforward approach to enhancing anion conductivity but faces a challenge in dimensional stability. Herein, we report the design and preparation of three kinds of isoreticular covalent organic framework (COF) membranes bearing tunable quaternary ammonium group densities as anion conductors.

Covalent organic frameworks with flexible side chains in hybrid PEMs enable highly efficient proton conductivity.

Electrochemical hydrogen compression (EHC) is an emerging energy conversion technology. Proton exchange membranes (PEMs) with high proton conductivity and high mechanical strength are highly required to meet the practical requirements of EHC. Herein, ionic covalent organic frameworks (iCOFs) with tunable side chains were synthesized and introduced into the sulfonated poly (ether ether ketone) (SPEEK) matrix to fabricate hybrid PEMs.

3D covalent organic framework membrane with fast and selective ion transport.

3D ionic covalent organic framework (COF) membranes, which are envisioned to be able to break the trade-off between ion conductivity and ion selectivity, are waiting for exploitation. Herein, we report the fabrication of a 3D sulfonic acid-functionalized COF membrane (3D SCOF) for efficient and selective ion transport, using dual acid-mediated interfacial polymerization strategy. The 3D SCOF membranes possess highly interconnected ion transport channels, ultramicroporous pore sizes (0.

Spacer-Engineered Ionic Channels in Covalent Organic Framework Membranes toward Ultrafast Proton Transport.

Side-chain engineering of covalent organic frameworks as advanced ion conductors is a critical issue to be explored. Herein, ionic covalent organic framework membranes (iCOFMs) with spacer-engineered ionic channel are de novo designed and prepared. The ionic channels are decorated with side chains comprising spacers having different carbon chain lengths and the -SO H groups at the end.

Covalent organic framework membranes for efficient separation of monovalent cations.

Covalent organic frameworks (COF), with rigid, highly ordered and tunable structures, can actively manipulate the synergy of entropic selectivity and enthalpic selectivity, holding great potential as next-generation membrane materials for ion separations. Here, we demonstrated the efficient separation of monovalent cations by COF membrane. The channels of COF membrane are decorated with three different kinds of acid groups.

Short hydrogen-bond network confined on COF surfaces enables ultrahigh proton conductivity.

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.

Assembling covalent organic framework membranes with superior ion exchange capacity.

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.

Tight Covalent Organic Framework Membranes for Efficient Anion Transport via Molecular Precursor Engineering.

Fabricating covalent organic frameworks (COFs) membranes with tight structure, which can fully utilize well-defined framework structure and thus achieve superior conduction performance, remains a grand challenge. Herein, through molecular precursor engineering of COFs, we reported the fabrication of tight COFs membrane with the ever-reported highest hydroxide ion conductivity over 200 mS cm at 80 °C, 100 % RH. Six quaternary ammonium-functionalized COFs were synthesized by assembling functional hydrazides and different aldehyde precursors.

Scalable Fabrication of Crystalline COF Membranes from Amorphous Polymeric Membranes.

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.

Weakly Humidity-Dependent Proton-Conducting COF Membranes.

State-of-the-art proton exchange membranes (PEMs) often suffer from significantly reduced conductivity under low relative humidity, hampering their efficient application in fuel cells. Covalent organic frameworks (COFs) with pre-designable and well-defined structures hold promise to cope with the above challenge. However, fabricating defect-free, robust COF membranes proves an extremely difficult task due to the poor processability of COF materials.

Analogous Mixed Matrix Membranes with Self-Assembled Interface Pathways.

The implementation of mixed matrix membranes (MMMs) for sub-angstrom scale gas separations remains a grand challenge. Herein, a series of analogous mixed matrix membrane (AMMMs) were constructed via molecular-level hybridization by utilizing a reactive ionic liquid (RIL) as the continuous phase and graphene quantum dots (GQD) as nanofiller for sub-angstrom scale ethylene/ethane (0.416 nm/0.

De Novo Design of Covalent Organic Framework Membranes toward Ultrafast Anion Transport.

The emergence of all-organic frameworks is of fundamental significance, and designing such structures for anion conduction holds great promise in energy conversion and storage applications. Herein, inspired by the efficient anion transport within organisms, a de novo design of covalent organic frameworks (COFs) toward ultrafast anion transport is demonstrated. A phase-transfer polymerization process is developed to acquire dense and ordered alignment of quaternary ammonium-functionalized side chains along the channels within the frameworks.

Metal-Organic Nanogel with Sulfonated Three-Dimensional Continuous Channels as a Proton Conductor.

Developing novel proton conductors is crucial to the electrochemical technology for energy conversion and storage. Metal-organic frameworks (MOFs), with a highly ordered and controllable structure, have been widely explored to prepare high-performance proton conductors. Albeit the prominent merits and great potential of the MOF-based materials such as MOF pellets or composite polymer electrolytes, constructing well-defined proton-transfer channels with much lower grain boundary resistance and more homogeneous distribution deserves extensive explorations.

Two-dimensional nanochannel membranes for molecular and ionic separations.

Two-dimensional (2D) nanosheets have emerged as promising functional materials owing to their atomic thickness and unique physical/chemical properties. By using 2D nanosheets as building blocks, diverse kinds of two-dimensional nanochannel membranes (2DNCMs) are being actively explored, in which mass transport occurs in the through-plane and interlayer channels of 2D nanosheets. The rational construction and physical/chemical microenvironment regulation of nanochannels are of vital significance for translating these 2D nanosheets into molecular separation membranes and ionic separation membranes.

Supramolecular Calix[]arenes-Intercalated Graphene Oxide Membranes for Efficient Proton Conduction.

Graphene oxide (GO) membranes with 2D interlaminar channels have triggered intensive interest as ion conductors. Incorporating abundant ion-conducting sites into GO interlayers is recognized as an effective strategy to facilitate ion conduction. Herein, we designed supramolecular compounds, -sulphonato-calix[]arenes (-SC[]As), as versatile intercalators to acquire highly conductive and robust GO membranes.

Control of Edge/in-Plane Interactions toward Robust, Highly Proton Conductive Graphene Oxide Membranes.

Graphene oxide (GO) membrane, bearing well-aligned interlayer nanochannels and well-defined physicochemical properties, promises fast proton transport. However, the deficiency of proton donor groups on the basal plane of GO and weak interlamellar interactions between the adjacent nanosheets often cause low proton conduction capability and poor water stability. Herein, we incorporate sulfonated graphene quantum dots (SGQD) into  GO membrane to solve the above dilemma synergistically controlling the edge electrostatic interaction and in-plane π-π interaction of SGQD with GO nanosheets.

Hydroxide Conduction Enhancement of Chitosan Membranes by Functionalized MXene.

In this study, imidazolium brushes tethered by ⁻NH₂-containing ligands were grafted onto the surface of a 2D material, MXene, using precipitation polymerization followed by quaternization. Functionalized MXene was embedded into chitosan matrix to prepare a hybrid alkaline anion exchange membrane. Due to high interfacial compatibility, functionalized MXene was homogeneously dispersed in chitosan matrix, generating continuous ion conduction channels and then greatly enhancing OH conduction property (up to 172%).

Graphene Oxide Membranes with Conical Nanochannels for Ultrafast Water Transport.

Membrane-based separations have been increasingly utilized to address global energy crisis and water scarcity. However, the separation efficiency often suffers from the trade-off between membrane permeability and selectivity. Although great efforts have been devoted, a membrane with both high permeability and high selectivity remains a distant prospect.

A Regularly Channeled Lamellar Membrane for Unparalleled Water and Organics Permeation.

Lamellar membranes show exceptional molecular permeation properties of key importance for many applications. However, their design and development need the construction of regular and straight interlayer channels and the establishment of corresponding transport rate equation. The fabrication of a uniformly lamellar membrane is reported using double-layered Ti C T MXenes as rigid building blocks.