Separation of Arylenevinylene Macrocycles with a Surface-Confined Two-Dimensional Covalent Organic Framework

Thickness-Driven Synthesis and Applications of Covalent Organic Framework Nanosheets

Covalent organic frameworks (COFs) are two-dimensional, crystalline porous framework materials with numerous scopes for tunability, such as porosity, functionality, stability and aspect ratio (thickness to length ratio). The manipulation of π-stacking in COFs results in truly 2D materials, namely covalent organic nanosheets (CONs), adds advantages in many applications. In this Minireview, we have discussed both top-down (COFs→CONs) and bottom-up (molecules→CONs) approaches with precise information on thickness and lateral growth. We have showcased the research progress on CONs in a few selected applications, such as batteries, catalysis, sensing and biomedical applications. This Minireview specifically highlights the reports where the authors compare the performance of CONs with COFs by demonstrating the impact of the thickness and lateral growth of the nanosheets. We have also provided the possible scope of exploration of CONs research in terms of inter-dimensional conversion, such as graphene to carbon nanotube and future technologies.

New Advances in Covalent Network Polymers via Dynamic Covalent Chemistry

Covalent network polymers, as materials composed of atoms interconnected by covalent bonds in a continuous network, are known for their thermal and chemical stability. Over the past two decades, these materials have undergone significant transformations, gaining properties such as malleability, environmental responsiveness, recyclability, crystallinity, and customizable porosity, enabled by the development and integration of dynamic covalent chemistry (DCvC). In this review, we explore the innovative realm of covalent network polymers by focusing on the recent advances achieved through the application of DCvC. We start by examining the history and fundamental principles of DCvC, detailing its inception and core concepts and noting its key role in reversible covalent bond formation. Then the reprocessability of covalent network polymers enabled by DCvC is thoroughly discussed, starting from the significant milestones that marked the evolution of these polymers and progressing to their current trends and applications. The influence of DCvC on the crystallinity of covalent network polymers is then reviewed, covering their bond diversity, synthesis techniques, and functionalities. In the concluding section, we address the current challenges faced in the field of covalent network polymers and speculates on potential future directions.

Raising the Asymmetric Catalytic Efficiency of Chiral Covalent Organic Frameworks by Tuning the Pore Environment

Chiral covalent organic frameworks (COFs) hold considerable promise in the realm of heterogeneous asymmetric catalysis. However, fine-tuning the pore environment to enhance both the activity and stereoselectivity of chiral COFs in such applications remains a formidable challenge. In this study, we have successfully designed and synthesized a series of clover-shaped, hydrazone-linked chiral COFs, each with a varying number of accessible chiral pyrrolidine catalytic sites. Remarkably, the catalytic efficiencies of these COFs in the asymmetric aldol reaction between cyclohexanone and 4-nitrobenzaldehyde correlate well with the number of accessible pyrrolidine sites within the frameworks. The COF featuring nearly one pyrrolidine moiety at each nodal point demonstrated excellent reaction yields and enantiomeric excess (ee) values, reaching up to 97 and 83%, respectively. The findings not only underscore the profound impact of a deliberately controlled chiral pore environment on the catalytic efficiencies of COFs but also offer a new perspective for the design and synthesis of advanced chiral COFs for efficient asymmetric catalysis.

Revolutionizing the structural design and determination of covalent-organic frameworks: principles, methods, and techniques

Covalent organic frameworks (COFs) represent an important class of crystalline porous materials with designable structures and functions. The interconnected organic monomers, featuring pre-designed symmetries and connectivities, dictate the structures of COFs, endowing them with high thermal and chemical stability, large surface area, and tunable micropores. Furthermore, by utilizing pre-functionalization or post-synthetic functionalization strategies, COFs can acquire multifunctionalities, leading to their versatile applications in gas separation/storage, catalysis, and optoelectronic devices. Our review provides a comprehensive account of the latest advancements in the principles, methods, and techniques for structural design and determination of COFs. These cutting-edge approaches enable the rational design and precise elucidation of COF structures, addressing fundamental physicochemical challenges associated with host-guest interactions, topological transformations, network interpenetration, and defect-mediated catalysis.

Emerging Robust Polymer Materials for High-Performance Two-Terminal Resistive Switching Memory

Facing the era of information explosion and the advent of artificial intelligence, there is a growing demand for information technologies with huge storage capacity and efficient computer processing. However, traditional silicon-based storage and computing technology will reach their limits and cannot meet the post-Moore information storage requirements of ultrasmall size, ultrahigh density, flexibility, biocompatibility, and recyclability. As a response to these concerns, polymer-based resistive memory materials have emerged as promising candidates for next-generation information storage and neuromorphic computing applications, with the advantages of easy molecular design, volatile and non-volatile storage, flexibility, and facile fabrication. Herein, we first summarize the memory device structures, memory effects, and memory mechanisms of polymers. Then, the recent advances in polymer resistive switching materials, including single-component polymers, polymer mixtures, 2D covalent polymers, and biomacromolecules for resistive memory devices, are highlighted. Finally, the challenges and future prospects of polymer memory materials and devices are discussed. Advances in polymer-based memristors will open new avenues in the design and integration of high-performance switching devices and facilitate their application in future information technology.

Reticular Synthesis of One-Dimensional Covalent Organic Frameworks with 4-c sql Topology for Enhanced Fluorescence Emission

Covalent organic frameworks (COFs) have been extensively investigated due to their unique structure, porosity, and functionality. However, at the topological level, COFs remain as two-dimensional (2D) or three-dimensional (3D) structures, while COFs with one-dimensional (1D) topology have not been systematically explored. In this work, we proposed a synthetic strategy for the construction of 1D-COFs based on non-linear edges and suitable high-symmetry vertices. Compared with their 2D-COFs counterparts, the 1D-COFs with AIEgens located at the vertex of the frame exhibited enhanced fluorescence. The density functional theory (DFT) calculations revealed that the dimensional-induced rotation restriction (DIRR) effect could spontaneously introduce additional non-covalent interactions between the strip frames, which could substantially diminish non-radiative transitions. This work also provides protocols for the design of 1D-COFs and a guidance scheme for the synthesis of emitting COFs.

Catalyst regulated interfacial synthesis of self-standing covalent organic framework membranes at room temperature for molecular separation

Covalent organic framework (COF) membranes have shown enormous potential for molecular separation due to their large surface areas and pre-designable structures. However, the mild and convenient preparation of COF membranes with high crystallinity has remained a significant challenge. In this work, we reported on a facile liquid-liquid interfacial polymerization method to fabricate self-standing imine-based COF membranes with excellent crystallinity and a tunable thickness at room temperature. Polymerization was confined at the immiscible organic solvent-water interface when the monomers in the dichloromethane met the catalyst aqueous solution. This unique design concept exploited the rapid formation of COF monolayers at the liquid-liquid interface to control catalyst diffusion and structural rearrangement, achieving high crystallinity of the COF membrane. Moreover, the thickness of the self-standing COF membranes could be regulated from 50 nm to 1 μm through the flexible regulation of the growth process. Benefiting from the large surface area of the COF membranes (378 m2/g) and the intensive π-π conjugate effect between the COFs and organic dyes, the obtained COF membranes exhibited high adsorption capacities toward Chrome Black T and Rose Bengal. This work may open a viable avenue to easily and mildly prepare COF membranes for water treatment.

On-Surface Synthesis toward Two-Dimensional Polymers

Two-dimensional (2D) polymers have garnered widespread interest because of their intriguing physicochemical properties. Envisaged applications in fields including nanodevices, solid-state chemistry, physical organic chemistry, and condensed matter physics, however, demand high-quality and large-scale production. In this perspective, we first introduce exotic band structures of organic frameworks holding honeycomb, kagome, and Lieb lattices. We further discuss how mesoscale ordered 2D polymers can be synthesized by means of choosing suitable monomers and optimizing growth conditions. We describe successful polymerization strategies to introducing a non-benzenoid subunit into a π-conjugated carbon lattice via delicately designed monomer precursors. Also, to obviate transfer and restore the intrinsic properties of π-conjugated polymers, new paradigms of aryl-aryl coupling on inert surfaces are discussed. Recent achievements in the photopolymerization demonstrate the need for monomer design. We conclude the potential applications of these organic networks and project the future possibilities in providing new insights into on-surface polymerization.

2D Covalent Organic Frameworks: From Synthetic Strategies to Advanced Optical-Electrical-Magnetic Functionalities

Covalent organic frameworks (COFs), an emerging class of organic crystalline polymers with highly oriented structures and permanent porosity, can adopt 2D or 3D architectures depending on the different topological diagrams of the monomers. Notably, 2D COFs have particularly gained much attention due to the extraordinary merits of their extended in-plane π-conjugation and topologically ordered columnar π-arrays. These properties together with high crystallinity, large surface area, and tunable porosity distinguish 2D COFs as an ideal candidate for the fabrication of functional materials. Herein, this review surveys the recent research advances in 2D COFs with special emphasis on the preparation of 2D COF powders, single crystals, and thin films, as well as their advanced optical, electrical, and magnetic functionalities. Some challenging issues and potential research outlook for 2D COFs are also provided for promoting their development in terms of structure, synthesis, and functionalities.

Controllable Synthesis and Performance Modulation of 2D Covalent-Organic Frameworks

Covalent-organic frameworks (COFs) are especially interesting and unique as their highly ordered topological structures entirely built from plentiful π-conjugated units through covalent bonds. Arranging tailorable organic building blocks into periodically reticular skeleton bestows predictable lattices and various properties upon COFs in respect of topology diagrams, pore size, properties of channel wall interfaces, etc. Indeed, these peculiar features in terms of crystallinity, conjugation degree, and topology diagrams fundamentally decide the applications of COFs including heterogeneous catalysis, energy conversion, proton conduction, light emission, and optoelectronic devices. Additionally, this research field has attracted widespread attention and is of importance with a major breakthrough in recent year. However, this research field is running with the lack of summaries about tailorable construction of 2D COFs for targeted functionalities. This review first covers some crucial polymeric strategies of preparing COFs, containing boron ester condensation, amine-aldehyde condensation, Knoevenagel condensation, trimerization reaction, Suzuki CC coupling reaction, and hybrid polycondensation. Subsequently, a summary is made of some representative building blocks, and then underlines how the electronic and molecular structures of building blocks can strongly influence the functional performance of COFs. Finally, conclusion and perspectives on 2D COFs for further study are proposed.

In Situ Construction of COF-Based Paper Serving as a Plasmonic Substrate for Enhanced PSI-MS Detection of Polycyclic Aromatic Hydrocarbons

Accurate detection, quantitation, and differentiation of polycyclic aromatic hydrocarbons (PAHs) and their isomers in diverse samples is elusive for paper spray ionization mass spectrometry (PSI-MS). To address these issues, herein, for the first time, we propose to fabricate a novel, flexible, and stable paper substrate based on covalent organic frameworks (COFs) via an in situ method under room temperature in air. After embedding gold nanoparticles (AuNPs), this paper substrate (COFs-paper) could further serve as a multifunctional plasmonic matrix (AuNPs-COFs-paper) for dual-wavelength laser-assisted PSI-MS detection of PAHs and feasible paper surface-enhanced Raman scattering (pSERS)-aided isomer discrimination. Taking advantage of the synergistic effect between the AuNPs and COFs present on the novel AuNP-embedded COFs-paper substrate, a satisfied LOD of 0.50 ng/μL for phenanthrene was realized, which improved almost 300 times compared with the naked-paper matrix, and the regression coefficient R² was up to 0.999. Real sample corn oil-containing PAHs can be efficiently detected and identified using this technique. The established platform has promising potential for on-site chemical analysis with portable PSI-MS and pSERS instruments.

Recent Progress in Nanoscale Covalent Organic Frameworks for Cancer Diagnosis and Therapy

Covalent organic frameworks (COFs) as a type of porous and crystalline covalent organic polymer are built up from covalently linked and periodically arranged organic molecules. Their precise assembly, well-defined coordination network, and tunable porosity endow COFs with diverse characteristics such as low density, high crystallinity, porous structure, and large specific-surface area, as well as versatile functions and active sites that can be tuned at molecular and atomic level. These unique properties make them excellent candidate materials for biomedical applications, such as drug delivery, diagnostic imaging, and disease therapy. To realize these functions, the components, dimensions, and guest molecule loading into COFs have a great influence on their performance in various applications. In this review, we first introduce the influence of dimensions, building blocks, and synthetic conditions on the chemical stability, pore structure, and chemical interaction with guest molecules of COFs. Next, the applications of COFs in cancer diagnosis and therapy are summarized. Finally, some challenges for COFs in cancer therapy are noted and the problems to be solved in the future are proposed.

Carbocatalysis with pristine graphite: on-surface nanochemistry assists solution-based catalysis

Carbocatalysis holds a privileged position as a sustainable alternative to metal-based catalysis. While the focus in solution-based catalytic processes generally lies on how the heterogeneous catalyst affects the solution composition, more attention has recently been given to the analysis of the carbon material itself. Various outstanding surface characterisation techniques, efficient in assessing the catalyst on-surface composition, are now available. These include high-resolution imaging tools such as scanning tunneling microscopy (STM), capable of bringing new insights into the processes determining rate and selectivity effects induced by carbocatalysts. In this regard, the use of self-assembly on graphite as a strategy to direct the outcome of chemical reactions has already shown great potential. This promising approach gives the scientific community the exciting prospect of rationalising selectivity in carbocatalysis with pristine graphite by linking in-solution and on-surface composition.

Boronic ester Sierpiński triangle fractals: from precursor design to on-surface synthesis and self-assembling superstructures

Herein, we designed and synthesized a precursor with a three-fold node and successfully constructed covalent Sierpiński triangle (ST) fractals with boronic ester linkages both at the liquid/solid interface at room temperature and by thermal annealing in a water atmosphere under ambient conditions. Remarkably, large-scale ordered superstructures of covalent STs are constructed by thermal annealing, which paves the way for property investigation of STs.

Fabrication of edge-curled petals-like covalent organic frameworks and their properties for extracting indole alkaloids from complex biological samples

In this study, a functionalized covalent-organic framework (COF) was first synthesized using porphyrin as the fabrication unit and showed an edge-curled, petal-like and well-ordered structure. The synthesized COF was then introduced to prepare porous organic polymer monolithic materials (POPMs). Two composite POPM/COF monolithic materials with rod shapes, referred to as sorbent A and sorbent B, were prepared in stainless steel tubes using different monomers. Sorbents A and B exhibited relatively uniform porous structures and enhanced specific surface areas of 153.14 m²/g and 80.01 m²/g, respectively. The prepared composite monoliths were used as in-tube solid-phase extraction (SPE) sorbents combined with HPLC for the on-line extraction and quantitative analytical systems. Indole alkaloids (from Catharanthus roseus G. Don and Uncaria rhynchophylla (Miq.) Miq. Ex Havil.) contained in mouse plasma were extracted and quantitatively analyzed using the online system. The two composite multifunctional monoliths showed excellent clean-up ability for complex biological matrices, as well as superior selectivity for target indole alkaloids. Method validation showed that the RSD values of the repeatability (n=6) were ≤ 3.46%, and the accuracy expressed by the spiked recoveries was in the ranges of 99.38%–100.91% and 96.39%–103.50% for vinca alkaloids and Uncaria alkaloids, respectively. Furthermore, sorbents A and B exhibited strong reusability, with RSD values ≤ 5.32%, which were based on the peak area of the corresponding alkaloids with more than 100 injections. These results indicate that the composite POPM/COF rod-shaped monoliths are promising media as SPE sorbents for extracting trace compounds in complex biological samples.

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Edge-curled petals-like COF was synthesized using porphyrin as the fabrication unit.

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In-tube monolithic POMP/COF composite SPE sorbents with rod-shape were fabricated.

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The in-tube sorbents were used to extract hence indole alkaloids from complex samples.

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The two homemade sorbents show strong reusability of more than 100 times.

Interfacial Synthesis of a Monolayered Fluorescent Two-Dimensional Polymer through Dynamic Imine Chemistry

A fluorescent monolayered two-dimensional polymer (2DP) containing both tetraphenylethylene (TPE) and imine linkages is synthesized at air-water interface using the Langmuir-Blodgett method. We designed TPE-based monomers with long distances between the TPE and the imine linkages to avoid the charge transfer and therefore keep the fluorescence. A monolayered 2DP provided with more than 104 μm2 in domain size and around 0.8 nm thickness was obtained through a successive Schiff base reaction at air-water interface. The nanostructures and fluorescent property of 2DP films were characterized by optical microscopy, SEM, TEM, AFM and fluorescence spectrum. Most importantly, the tip-enhanced Raman spectroscopy (TERS) was utilized here to confirm the success of the polycondensation of monolayered 2DP.

Covalent Organic Frameworks: Design, Synthesis, and Functions

Covalent organic frameworks (COFs) are a class of crystalline porous organic polymers with permanent porosity and highly ordered structures. Unlike other polymers, a significant feature of COFs is that they are structurally predesignable, synthetically controllable, and functionally manageable. In principle, the topological design diagram offers geometric guidance for the structural tiling of extended porous polygons, and the polycondensation reactions provide synthetic ways to construct the predesigned primary and high-order structures. Progress over the past decade in the chemistry of these two aspects undoubtedly established the base of the COF field. By virtue of the availability of organic units and the diversity of topologies and linkages, COFs have emerged as a new field of organic materials that offer a powerful molecular platform for complex structural design and tailor-made functional development. Here we target a comprehensive review of the COF field, provide a historic overview of the chemistry of the COF field, survey the advances in the topology design and synthetic reactions, illustrate the structural features and diversities, scrutinize the development and potential of various functions through elucidating structure-function correlations based on interactions with photons, electrons, holes, spins, ions, and molecules, discuss the key fundamental and challenging issues that need to be addressed, and predict the future directions from chemistry, physics, and materials perspectives.

Confined growth of ordered organic frameworks at an interface

This tutorial review covers the recent design, synthesis, characterization, and property study of COF thin films and covalent monolayers through interfacial polymerization.

Surface-confined single-layer covalent organic frameworks: design, synthesis and application

This review describes the state of the art of surface-confined single-layer covalent organic frameworks, focusing on reticular design, synthesis approaches, and exploring applications in host/guest chemistry.

A C-N Coupling Polymerization on Ice-Surface towards Decimeter-Sized 2D Covalent Materials with High Catalytic Activity for Water-Splitting

Compared to other solid templates (metal, ceramic, carbon, etc.), polymerization on ice-surface has many advantages. However, the popularity of this method has been impeded by the lack of appropriate polymerization reactions. To date, only few oxidation polymerizations have been reported to occur on ice-surface, and unfortunately they can only produce supramolecular films rather than fully covalent films. Herein for the first time, 2D covalent materials have been created on ice-surface even at -16 °C through a C-N coupling polymerization, and two free-standing 2D polyarylamines (2DPA)s were synthesized. Both 2DPAs have decimeter-size and nanometer thickness. This study provides the first polymerization reaction to synthesize 2D covalent materials on ice-surface, which can be used to fabricate materials/tools/robots with specific 2D structure by copying ice morphologies. Furthermore, both 2DPAs exhibit higher hydrogen evolution reaction activity than many metal-free catalysts and even some metal-based catalysts, so this study also provides further insight for the development of metal-free catalysts for water-splitting.

Nanopatterns of arylene-alkynylene squares on graphite: self-sorting and intercalation

Supramolecular nanopatterns of arylene–alkynylene squares with side chains of different lengths are investigated by scanning tunneling microscopy at the solid/liquid interface of highly oriented pyrolytic graphite and 1,2,4-trichlorobenzene. Self-sorting leads to the intermolecular interdigitation of alkoxy side chains of identical length. Voids inside and between the squares are occupied by intercalated solvent molecules, which numbers depend on the sizes and shapes of the nanopores. In addition, planar and non-planar coronoid polycyclic aromatic hydrocarbons (i.e., butyloxy-substituted kekulene and octulene derivatives) are found to be able to intercalate into the intramolecular nanopores.

On-Surface Crystallization Behaviors of H-Bond Donor-Acceptor Complexes at Liquid/Solid Interfaces

Two-dimensional (2D) crystallization behaviors of A-TPC _n ( n = 4, 6, 10), T3C₄, and hydrogen-bonded complexes T3C₄@TPC _n ( n = 4, 6, 10) are investigated by means of scanning tunneling microscope (STM) observations and density functional theory (DFT) calculations. The STM observations reveal that A-TPC₄, A-TPC₁₀, and T3C₄ self-organize into dumbbell-shaped structures, well-ordered bright arrays, and zigzag structures, respectively. Interestingly, T3C₄@TPC₁₀ fails to form the cage-ball structure, whereas T3C₄@TPC₄ and T3C₄@TPC₆ co-assemble into cage-ball structures with the same lattice parameters. The filling rates of the balls of these two kinds of cage-ball structures depend heavily on the deposition sequence. As a result, the filling rates of the cages in T3C₄/A-TPC _n ( n = 4, 6) with deposition of T3C₄ anterior to A-TPC _n are higher than those in A-TPC _n/T3C₄ ( n = 4, 6) with the opposite deposition sequence. Furthermore, lattice defects formed by T3C₄ coexist with the cage-ball structures. Moreover, the similar energy per unit area of lattice defects (-0.101 kcal mol^-1 Å^-2) and the two cage-ball networks (-0.194 and -0.208 kcal mol^-1 Å^-2, respectively), illustrating the similar stabilities of lattice defects and cage-ball networks, demonstrates the rationality of lattice defects. Combining STM investigations and DFT calculations, this work could provide a useful approach to investigate the 2D crystallization mechanisms of supramolecular liquid crystals on surfaces.

A Robust Nonvolatile Resistive Memory Device Based on a Freestanding Ultrathin 2D Imine Polymer Film

Here, the synthesis of a wafer-scale ultrathin 2D imine polymer (2DP) film with controllable thickness from simple benzene-1,3,5-tricarbaldehyde (BTA) and p-phenylenediamine (PDA) building blocks is reported using a Schiff base polycondensation reaction at the air-water interface. The synthesized freestanding 2DP films are porous, insulating, and more importantly, covalently linked, which is ideally suited for nonvolatile memristors that use a conductive filament mechanism. These devices exhibit excellent switching performance with high reliability and reproducibility, with on/off ratios in the range of 10² to 10⁵ depending on the thickness of the film. In addition, the endurance and data retention capability of 2DP-based nonvolatile resistive memristors are up to 200 cycles and 8 × 10⁴ s under constant voltage stress at 0.1 V. The intrinsic flexibility of the covalent organic polymer enables the fabrication of a flexible memory device on a polyimide film, which exhibits as reliable memory performance as that on the rigid substrate. Moreover, the 2DP-based memory device shows outstanding thermal stability and organic solvent resistance, which are desirable properties for applications in wearable devices.

Energy-storage covalent organic frameworks: improving performance via engineering polysulfide chains on walls

The aligned one-dimensional channels found in covalent organic frameworks offer a unique space for energy storage. However, physical isolation of sulfur in the channels is not sufficient to prevent the shuttle of lithium-sulfide intermediates that eventually results in a poor performance of lithium-sulfur energy storage. Herein, we report a strategy based on imine-linked frameworks for addressing this shuttle issue by covalently engineering polysulfide chains on the pore walls. The imine linkages can trigger the polymerization of sulfur to form polysulfide chains and anchor them on the channel walls. The immobilized polysulfide chains suppress the shuttle effect and are highly redox active. This structural evolution induces multifold positive effects on energy storage and achieves improved capacity, sulfur accessibility, rate capability and cycle stability. Our results suggest a porous platform achieved by pore wall engineering for tackling key issues in energy storage.

Two dimensional nanomaterial-based separation membranes

Two dimensional nanomaterials including graphene, hexagonal boron-nitride, molybdenum disulfide, etc., provide immense potentials for separation applications. However, the tradeoff between selectivity and permeability in choosing 2D nanomaterial-based membrane is inevitable, limiting the progress on separation efficiency for mass industrial applications. To target these issues, versatile strategies such as the rational design of predefined interlayer channels, membrane nanopores, and reasonable functionalization, as well as new mechanisms have been emerged. In this review, we introduce the recent progress on separation mechanisms of 2D nanomaterial-based membranes with different structures (including the interlayer channels type and the membrane nanopores type) and their inner surface functionalization. Moreover, the interface designs are discussed, in terms of employing dynamic liquid-liquid/liquid-gas interfaces, to advance the selectivity and permeability of the membranes. We further discuss the variety of separation applications based on 2D nanomaterial-based membranes. The authors hope this review will inspire the active interest of many scientists in the area of the development and application of membrane science.

A facilely synthesized glutathione-functionalized silver nanoparticle-grafted covalent organic framework for rapid and highly efficient enrichment of N-linked glycopeptides

The development of facilely synthetic materials for highly efficient enrichment of N-linked glycopeptides is essential in glycoproteome analysis. In this work, by utilizing the self-assembling of glutathione (GSH) on silver nanoparticles (Ag NPs), and the formation and dispersion of Ag NPs on a robust TpPa-1 substrate, a newly functionalized covalent organic framework (COF) called TpPa-1@Ag@GSH was synthesized via a simple two step post-synthetic modification. TpPa-1@Ag@GSH and intermediate products were confirmed and evaluated by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy-energy dispersive spectroscopy, Brunauer-Emmett-Teller and thermogravimetric analyses. Benefiting from the judicious selection of the substrate, the abundance of binding sites, relatively high affinity between GSH and N-linked glycopeptides, and the multivalent interactions between N-linked glycopeptides and unoccupied surfaces of Ag NPs, this porous material showed great performance in N-linked glycopeptide enrichment. By enriching N-linked glycopeptides in tryptic digests of human serum immunoglobulin G (human IgG) followed by mass spectrometry analysis, our method was proved to have good sensitivity (1 fmol), high selectivity (1 : 1500, human IgG to bovine serum albumin), high binding capacity (160 mg g-1, IgG/TpPa-1@Ag@GSH), ultra-fast capture ability (only 1 min incubation time), and good reusability (at least 5 times). It was also successfully applied to the enrichment of N-linked glycopeptides from complex biological samples. Our work improved the enrichment selectivity of COFs, reached the most rapid capture ability among off-column enrichment materials, and provided a very facile and easily popularized post-synthetic modification route for COFs in glycoproteome analysis.

Large-scale synthesis of azine-linked covalent organic frameworks in water and promoted by water

A hydrothermal procedure has been developed to synthesize covalent organic frameworks in water with the advantages of large-scale production, short reaction time, catalyst-free reaction, and improved product quality.

A gaseous hydrogen chloride chemosensor based on a 2D covalent organic framework

A tetraphenylethene-based 2D covalent organic framework (COF) has been synthesized. It exhibits a very fast response and high sensitivity to the presence of gaseous HCl by way of distinct changes in fluorescence emission and color, which makes the COF a good chemosensor for spectroscopic and naked-eye detection of gaseous HCl.

Unidirectional supramolecular self-assembly inside nanocorrals via in situ STM nanoshaving

Self-assembly of an alkylated diacetylene derivative is spatially confined via in situ scanning tunneling microscopy (STM) nanoshaving inside covalently modified highly ordered pyrolytic graphite (CM-HOPG). In contrast to unconstrained self-assembly that occurs randomly along three thermodynamically equivalent surface lattice directions, spatially confined assemblies are shown to form along chosen substrate orientations. Experimental statistics suggest two mechanisms for breaking the rotational degeneracy of the surface. First, the assembly orientation is biased via lateral confinement inside nanocorrals that do not match the substrate symmetry. Second, an interaction between the assembling molecules and the STM tip during nanoshaving guides 2D crystal nucleation and growth. The results presented here open new possibilities to regulate and orient self-assembled architectures via in situ nanomechanical manipulation techniques and provide mechanistic insights into the process.