1D Nanochannels Research Articles

1D Crystallographic Etching of Few‐Layer WS2

AbstractLayer number‐dependent band structures and symmetry are vital for the electrical and optical characteristics of 2D transition metal dichalcogenides (TMDCs). Harvesting 2D TMDCs with tunable thickness and properties can be achieved through top‐down etching and bottom‐up growth strategies. In this study, a pioneering technique that utilizes the migration of in situ generated Na‐W‐S‐O droplets to etch out 1D nanotrenches in few‐layer WS2 is reported. 1D WS2 nanotrenches are successfully fabricated on the optically inert bilayer WS2, showing pronounced photoluminescence and second harmonic generation signals. Additionally, the modulation of inkjet‐printed Na2WO4‐Na2SO4 particles to switch between the etching and growth modes by manipulating the sulfur supply is demonstrated. This versatile approach enables the creation of 1D nanochannels on 2D TMDCs. The research presents exciting prospects for the top‐down and bottom‐up fabrication of 1D‐2D mixed‐dimensional TMDC nanostructures, expanding their use for electronic and optoelectronic applications.

Supramolecular Assembly of Fused Macrocycle-Cage Molecules for Fast Lithium-Ion Transport.

We report a new supramolecular porous crystal assembled from fused macrocycle-cage molecules. The molecule comprises a prismatic cage with three macrocycles radially attached. The molecules form a nanoporous crystal with one-dimensional (1D) nanochannels. The supramolecular porous crystal can take up lithium-ion electrolytes and achieve an ionic conductivity of up to 8.3 × 10-4 S/cm. Structural analysis and density functional theory calculations reveal that efficient Li-ion electrolyte uptake, the presence of 1D nanochannels, and weak interactions between lithium ions and the crystal enable fast lithium-ion transport. Our findings demonstrate the potential of fused macrocycle-cage molecules as a new design motif for ion-conducting molecular crystals.

One-Dimensional Covalent Organic Framework-Based Multilevel Memristors for Neuromorphic Computing.

Memristors are essential components of neuromorphic systems that mimic the synaptic plasticity observed in biological neurons. In this study, a novel approach employing one-dimensional covalent organic framework (1D COF) films was explored to enhance the performance of memristors. The unique structural and electronic properties of two 1D COF films (COF-4,4'-methylenedianiline (MDA) and COF-4,4'-oxydianiline (ODA)) offer advantages for multilevel resistive switching, which is a key feature in neuromorphic computing applications. By further introducing a TiO2 layer on the COF-ODA film, a built-in electric field between the COF-TiO2 interfaces could be generated, demonstrating the feasibility of utilizing COFs as a platform for constructing memristors with tunable resistive states. The 1D nanochannels of these COF structures contributed to the efficient modulation of electrical conductance, enabling precise control over synaptic weights in neuromorphic circuits. This study also investigated the potential of these COF-based memristors to achieve energy-efficient and high-density memory devices.

One‐Dimensional Covalent Organic Framework‐Based Multilevel Memristors for Neuromorphic Computing

AbstractMemristors are essential components of neuromorphic systems that mimic the synaptic plasticity observed in biological neurons. In this study, a novel approach employing one‐dimensional covalent organic framework (1D COF) films was explored to enhance the performance of memristors. The unique structural and electronic properties of two 1D COF films (COF‐4,4′‐methylenedianiline (MDA) and COF‐4,4′‐oxydianiline (ODA)) offer advantages for multilevel resistive switching, which is a key feature in neuromorphic computing applications. By further introducing a TiO2 layer on the COF‐ODA film, a built‐in electric field between the COF‐TiO2 interfaces could be generated, demonstrating the feasibility of utilizing COFs as a platform for constructing memristors with tunable resistive states. The 1D nanochannels of these COF structures contributed to the efficient modulation of electrical conductance, enabling precise control over synaptic weights in neuromorphic circuits. This study also investigated the potential of these COF‐based memristors to achieve energy‐efficient and high‐density memory devices.

An NMR study of hexamethylbenzene (HMB) incorporated in 2,4,6-tris(4-chlorophenoxy)-1,3,5-triazine (CLPOT) framework

Molecular motion of hexamethylbenzene (HMB) incorporated in 2,4,6-tris(4-chlorophenoxy)-1,3,5-triazine (CLPOT) was investigated by 1H NMR spin-lattice relaxation time T1 measurements. In the porous space of one-dimensional (1D) CLPOT nanochannels, HMB molecules reorientate more freely compared to bulk HMB crystals. With low concentrations x < 0.5 of CLPOT-(HMB)x, the distribution of HMB seems to be quite inhomogeneous in 1D nanochannel. The activation energy of the in-plane reorientation of HMB is 5 kJ mol−1 due to the interaction with nanochannel-wall and 10 - 18 kJ mol−1 depending on the separation distance when the interaction between the adjacent HMB molecules determines the activation energy.

Pore-in-Pore Engineering in a Covalent Organic Framework Membrane for Gas Separation

Covalent organic framework (COF) membranes have emerged as a promising candidate for energy-efficient separations, but the angstrom-precision control of the channel size in the subnanometer region remains a challenge that has so far restricted their potential for gas separation. Herein, we report an ultramicropore-in-nanopore concept of engineering matreshka-like pore-channels inside a COF membrane. In this concept, α-cyclodextrin (α-CD) is in situ encapsulated during the interfacial polymerization which presumably results in a linear assembly (LA) of α-CDs in the 1D nanochannels of COF. The LA-α-CD-in-TpPa-1 membrane shows a high H2 permeance (∼3000 GPU) together with an enhanced selectivity (>30) of H2 over CO2 and CH4 due to the formation of fast and selective H2-transport pathways. The overall performance for H2/CO2 and H2/CH4 separation transcends the Robeson upper bounds and ranks among the most powerful H2-selective membranes. The versatility of this strategy is demonstrated by synthesizing different types of LA-α-CD-in-COF membranes.

Molecular Bridge Engineering for Tuning Quantum Electronic Transport and Anisotropy in Nanoporous Graphene

Recent advances on surface-assisted synthesis have demonstrated that arrays of nanometer wide graphene nanoribbons can be laterally coupled with atomic precision to give rise to a highly anisotropic nanoporous graphene structure. Electronically, this graphene nanoarchitecture can be conceived as a set of weakly coupled semiconducting 1D nanochannels with electron propagation characterized by substantial interchannel quantum interferences. Here, we report the synthesis of a new nanoporous graphene structure where the interribbon electronic coupling can be controlled by the different degrees of freedom provided by phenylene bridges that couple the conducting channels. This versatility arises from the multiplicity of phenylene cross-coupling configurations, which provides a robust chemical knob, and from the interphenyl twist angle that acts as a fine-tunable knob. The twist angle is significantly altered by the interaction with the substrate, as confirmed by a combined bond-resolved scanning tunneling microscopy (STM) and ab initio analysis, and should accordingly be addressable by other external stimuli. Electron propagation simulations demonstrate the capability of either switching on/off or modulating the interribbon coupling by the corresponding use of the chemical or the conformational knob. Molecular bridges therefore emerge as efficient tools to engineer quantum transport and anisotropy in carbon-based 2D nanoarchitectures.

Pyrazine-Functionalized Donor-Acceptor Covalent Organic Frameworks for Enhanced Photocatalytic H2 Evolution with High Proton Transport.

The well-defined 2D or 3D structure of covalent organic frameworks (COFs) makes it have great potential in photoelectric conversion and ions conduction fields. Herein, a new donor-accepter (D-A) COF material, named PyPz-COF, constructed from electron donor 4,4',4″,4'″-(pyrene-1,3,6,8-tetrayl)tetraaniline and electron accepter 4,4'-(pyrazine-2,5-diyl)dibenzaldehyde with an ordered and stable π-conjugated structure is reported. Interestingly, the introduction of pyrazine ring endows the PyPz-COF a distinct optical, electrochemical, charge-transfer properties, and also brings plentiful CN groups that enrich the proton by hydrogen bonds to enhance the photocatalysis performance. Thus, PyPz-COF exhibits a significantly improved photocatalytic hydrogen generation performance up to 7542µmol g-1 h-1 with Pt as cocatalyst, also in clear contrast to that of PyTp-COF without pyrazine introduction (1714µmol g-1 h-1 ). Moreover, the abundant nitrogen sites of the pyrazine ring and the well-defined 1D nanochannels enable the as-prepared COFs to immobilize H3 PO4 proton carriers in COFs through hydrogen bond confinement. The resulting material has an impressive proton conduction up to 8.10 × 10-2 S cm-1 at 353 K, 98% RH. This work will inspire the design and synthesis of COF-based materials with both efficient photocatalysis and proton conduction performance in the future.

Intrinsic ion transport of highly charged sub-3-nm boron nitride nanotubes

Debate regarding the transport mechanisms of water and ions in highly charged one-dimensional (1D) nanochannel continues because of a lack of available experimental data. Here, we present a nanofluidic platform consisting of ≈2.7-nm-diameter boron nitride nanotubes (BNNTs) as a model system, and report the experimental ion transport in these sub-3-nm BNNTs. We elucidate that strong electrostatic interactions between the highly charged tube walls and ions, stemming from the high surface-charge density (378 mC/m2) of BNNTs, play important roles in defining the ion transport mechanism in BNNT pores. Experimental analysis of ion transports supported by numerical the Donnan steric pore model with dielectric exclusion (DSPM-DE) and Derjaguin–Landau–Verwey–Overbeek (DLVO) model elucidate the relationship of the ionic charge density and surface-charge density of the BNNT wall to electrostatic interaction, steric, and dielectric effects. We also demonstrate that BNNTs exhibit higher NaCl separation (≈90%) than commercial reverse-osmosis (≈80%) and nanofiltration (≈60%) membranes under the same experimental conditions, despite having a larger pore size. Our results establish design criteria for developing highly efficient ion-selective membranes for various practical applications.

Facile, Direct, De Novo Synthesis of an Alkyl Phosphoric Acid-Decorated Covalent Organic Framework.

The development and understanding of proton conductors based on phosphoric acid are critical for the field of chemistry, biology, and energy. Covalent organic frameworks (COFs), featuring highly crystalline structures and controllable pore sizes, are suitable for constructing phosphoric acid-based proton conductors. However, because of tedious and intricate synthesis, how to develop COFs based on phosphoric acid remains a substantial challenge. Herein, a side-chain decorated strategy is contributed to construct a phosphoric acid-functionalized, imine-linked COF by de novo synthesis. The phosphoric acid side chains with vigorous motion integrating with 1D nanochannels endow the resulting COF with intrinsic proton conductivity. This work expectantly provides a competitive alternative for producing phosphoric acid-functionalized COFs with high intrinsic proton conductivity.

Inter-Spin Interactions of 1D Chains of Different-Sized Nitroxide Radicals Incorporated in the Organic 1D Nanochannels of Tris(o-phenylenedioxy)cyclotriphosphazene

Abstract Variable-temperature electron spin resonance (ESR) was measured for one-dimensional (1D) molecular chains formed using different-sized organic radicals incorporated into the 1D nanochannels of tris(o-phenylenedioxy)cyclotriphosphazene (TPP). The ESR spectra for the molecular chains of 4-oxo-2,2,6,6-tetramethyl-1-piperidinyl-1-oxyl (TEMPONE) incorporated in the TPP nanochannels ([TPP-TEMPONE]) exhibited anisotropic three-dimensional (3D) spin diffusion at temperatures close to room temperature. In contrast, 1D spin diffusion was observed even at low temperatures indicating a longer rotational diffusion correlation time or the termination of molecular motion of the guest radicals dispersed in the TPP nanochannels. The temperature range for 1D spin diffusion in [TPP-TEMPONE] was higher and wider than that of TPP inclusion compounds incorporating smaller nitroxide radicals, such as di-t-butyl nitroxide (DTBN), or 2,2,6,6-tetramethyl-1-piperidinyl-1-oxyl (TEMPO) radicals, as previously reported. Thus, inter-spin interactions of the organic-radical 1D molecular chains formed in size-adjustable nanochannels, such as TPP, are influenced by the molecular size and dynamics of guest radicals, and temperature.

Second interfacial polymerization decorating defects of TFC NF membrane formed by 1D nanochannels for improving separation performance

Generating nanovoids/nanochannels in the polyamide rejection layer is an effective method to enhance the separation performance of thin-film composite (TFC) membranes. However, the excessive nanovoids/nanochannels formed in the rejection layer will cause defects and reduce the selectivity. Here we report a secondary interfacial polymerization (SIP) method to decorate the defects caused by one-dimensional (1D) nanochannels, which were generated by etching 1D copper hydroxide nanorods (CuNRs). The obtained SIP-1D NF membrane had a pure water permeability of 8.2 L·m−2·h−1 bar−1, while the divalent salts rejection was 92.0 ± 2.6% of Na2SO4, 91.3 ± 0.3% of MgCl2, and 91.8 ± 0.2% of MgSO4. Our work provides experimental basis for 1D nanochannels regulate the structures and properties of NF membrane.

Accumulation of Sulfonic Acid Groups Anchored in Covalent Organic Frameworks as an Intrinsic Proton-Conducting Electrolyte.

Covalent organic frameworks (COFs) are a novel class of crystalline porous polymers, which possess high porosity, excellent stability, and regular nanochannels. 2D COFs provide a 1D nanochannel to form the proton transport channels. The abovementioned features afford a powerful potential platform for designing materials as proton transportation carriers. Herein, the authors incorporate sulfonic acid groups on the pore walls as proton sources for enhancing proton transport conductivity in the 1D channel. Interestingly, the sulfonic acid COFs (S-COFs) electrolytes being binder free exhibit excellent proton conductivity of ≈1.5 × 10-2 S cm-1 at 25 ℃ and 95% relative humidity (RH), which rank the excellent performance in standard proton-conducting electrolytes. The S-COFs electrolytes keep the high proton conduction over the 24 h. The activation energy is estimated to be as low as 0.17eV, which is much lower than most reported COFs. This research opens a new window to evolve great potential of structural design for COFs as the high proton-conducting electrolytes.

Rational ion transport management mediated through membrane structures.

Unique membrane structures endow membranes with controlled ion transport properties in both biological and artificial systems, and they have shown broad application prospects from industrial production to biological interfaces. Herein, current advances in nanochannel-structured membranes for manipulating ion transport are reviewed from the perspective of membrane structures. First, the controllability of ion transport through ion selectivity, ion gating, ion rectification, and ion storage is introduced. Second, nanochannel-structured membranes are highlighted according to the nanochannel dimensions, including single-dimensional nanochannels (i.e., 1D, 2D, and 3D) functioning by the controllable geometrical parameters of 1D nanochannels, the adjustable interlayer spacing of 2D nanochannels, and the interconnected ion diffusion pathways of 3D nanochannels, and mixed-dimensional nanochannels (i.e., 1D/1D, 1D/2D, 1D/3D, 2D/2D, 2D/3D, and 3D/3D) tuned through asymmetric factors (e.g., components, geometric parameters, and interface properties). Then, ultrathin membranes with short ion transport distances and sandwich-like membranes with more delicate nanochannels and combination structures are reviewed, and stimulus-responsive nanochannels are discussed. Construction methods for nanochannel-structured membranes are briefly introduced, and a variety of applications of these membranes are summarized. Finally, future perspectives to developing nanochannel-structured membranes with unique structures (e.g., combinations of external macro/micro/nanostructures and the internal nanochannel arrangement) for mediating ion transport are presented.

Confinement Strategies for Precise Synthesis of Efficient Electrocatalysts from the Macroscopic to the Atomic Level

ConspectusTremendous efforts have shown that the precise control of the electrocatalyst structure and morphology can boost their catalytic performance toward diverse important reactions such as oxygen reduction/evolution reactions (ORR/OER), hydrogen oxidation/evolution reaction (HOR/HER), carbon dioxide/nitrogen reduction reactions (CO2RR/NRR), etc. The physical and chemical confined syntheses have witnessed the success in manipulating catalyst features from macroscopic to atomic level to deal with various application demands.In this Account, we summarize the recent innovative advances with an emphasis on our solutions in the precise synthesis of efficient electrocatalysts via the confinement strategies at various scales. By categorizing the confinement effects into the precursor self-confinement, nanospace confinement, and chemical binding atomic confinement with representative examples, we systematically introduced the confinement strategies in the synthesis of well-defined structures from the macroscopic to nanoscopic and atomic level. (1) Precursor self-confinement strategy. The electrode with a macroscopic hierarchical micro/nanoarray structure provides a large exposed surface area and structural merits for highly intensive electron transport and mass transfer as well as prompt gas release, which enables high-performance electrocatalytic energy devices. The self-confinement effect from the presynthesized precursors promises to rationally design and precisely fabricate such electrodes at the macroscopic level. (2) Nanospace confinement strategy. Metal clusters and nanoparticles (NPs) offer diverse surface sites for the adsorption, activation, and transformation of reactants/intermediates. The confinement from nanospaces such as 0D nanopores, 1D nanochannels, 2D interlayer spaces, and 3D interconnected nanochannels enables the synthesis of nanoclusters and NPs with controlled morphologies and structures at the nanoscopic level, allowing for investigating the collective activation of intermediates, interaction with support, size-dependent structure–performance relationship. etc. (3) Chemical binding atomic confinement strategy. The chemical binding confinement makes it possible to synthesize single atom catalysts (SACs) with the capability of delicately tailoring their electronic structure and chemical environment at the atomic level, providing opportunities for in-depth understanding the underlying catalytic processes and the structure–performance relationships. (4) Integrated confinement strategy. Taking all these confinement effects into account together is powerful to mitigate the challenges in the synthetic fields such as well-defined high-density SACs. With these insights, this Account proposes the remaining challenges and possible solutions for the precise synthesis of next-generation well-defined electrocatalysts from macroscopic to atomic level by exploring suitable confinement effects and integrating them with other techniques, which may open up opportunities for bridging the gap between the fundamental research and industrial applications.

Host-Guest Assembly of H-Bonding Networks in Covalent Organic Frameworks for Ultrafast and Anhydrous Proton Transfer.

An anhydrous proton conductor represents a key material for the manufacture of high-energy electrical devices. Incorporation of proton carriers into the vacancies of the porous solid provides an effective method for their preparation, but the weak or even no interactions between the ion carriers and the porous solids causing a serious leaking of ion carriers result in trade-off of long-term conductivity. In this term, we developed a host-guest supramolecular chemistry-induced strategy to assemble hydrogen bond networks along the 1D nanochannels of covalent organic frameworks (COFs) for ultrafast and anhydrous proton transfer (1.33 × 10-2 S cm-1 at 140 °C). Solid-state NMR was applied to explore guest interaction between protic ionic liquids (PILs) and the COFs to investigate the proton transport mechanism. This work presents an excellent example of accumulation of PILs into the nanochannels of COFs for anhydrous proton conduction at high temperature, demonstrating great advantages of COFs to serve as a supramolecular host for holding/transiting ions in the solid state.

TG-DTA of inclusion compound consisting of acetaminophen incorporated into 1D nanochannels of 2,4,6-tris(4-chlorophenoxy)-1,3,5-triazine

Inclusion compounds (ICs) have the potential to act as drug carriers. In this study, an IC consisting of acetaminophen incorporated into 2,4,6-tris(4-chlorophenoxy)-1,3,5-triazine (CLPOT) was synthesized ([CLPOT-acetaminophen]). Elemental analysis, 1H NMR spectroscopy and thermogravimetry-differential thermal analysis (TG-DTA), of the IC confirmed that ~0.1 acetaminophen molecules were included as guest molecules per CLPOT unit cell. The inclusion of acetaminophen in the 1D nanochannels of CLPOT was further confirmed by the DTA results of [CLPOT-acetaminophen], which showed the endothermal peak at 157 °C indicating the desorption of acetaminophen confined in the CLPOT nanochannels. These results suggest that CLPOT could be used as a stable microscopic carrier of biomaterials.

Covalent Organic Framework-Based Electrolytes for Fast Li+ Conduction and High-Temperature Solid-State Lithium-Ion Batteries

It has been a long-standing challenge to design and fabricate high Li+ conductive polymer electrolytes at the atomic level with superior thermal stability for solid-state lithium-ion batteries. Covalent organic frameworks (COFs) with tailor-made 1D nanochannels provide a potential pathway for fast ion transport, but it remains elusive. In this work, three crystalline thiophene-based imine-linked COFs were constructed and explored as Li+-conducting composite electrolytes by doping ionic liquids into their 1D nanochannels. The COF–IL composite electrolytes exhibited excellent thermal stability (up to 400 °C) and high Li+ conductivity (up to 2.60 × 10–3 S/cm at 120 °C, one of the highest values of doped porous organic materials). Furthermore, the COF–IL composite electrolytes exhibited stable cycling in a LiFePO4–Li full cell with a high initial discharge specific capacity of 140.8 mA·h/g at 100 °C, more stable than common poly(ethylene oxide)-based electrolytes, indicating great potential application under a high-temperature operation. This work opens a new avenue for the development of fast Li+-conducting COF-based electrolytes for high-temperature solid-state lithium-ion batteries.

Two-dimensional metal–organic framework with perpendicular one-dimensional nano-channel as precise polysulfide sieves for highly efficient lithium–sulfur batteries

When 2D CuBDC MOF sheets with perpendicular 1D nano-channels (5.2 Å) was were used as polysulfides sieves for Li–S batteries, suppressed “shuttle effect” and enhanced electrochemical performance were achieved.

Polyamide reverse osmosis membranes containing 1D nanochannels for enhanced water purification

Thin-film composite (TFC) reverse osmosis (RO) membrane is the gold-standard for desalination and water reuse. Recent literature highlights the importance of polyamide (PA) rejection layer containing nanovoids to manipulate the water permeability and salt rejection. In this study, a facile template-assisted approach was applied to generate one-dimensional (1D) nanochannels in the polyamide rejection layer of RO membranes by preloading copper nanorods inside the PA layer followed by acid etching. In addition, a TFC RO membrane containing 0D nanovoids was also fabricated to compare the dimensional effect of nanochannels on membrane morphologies and performances. Specifically, the TFC-0D membrane only exhibited 61% higher water permeability compared to that of the control TFC, while the TFC-1D membrane showed 126% higher water flux with similar NaCl rejection, probably due to the dimensional improvement of the nanochannels inside the rejection layer. This templates-assisted approach paves a feasible way for fabricating high-performance next-generation RO membranes.