Covalent Organic Frameworks Research Articles

Single Na- and K-Ion-Conducting Sulfonated -NH-Linked Covalent Organic Frameworks.

Highly ion-conductive solid electrolytes of nonlithium ions (sodium or potassium ions) are necessary for pursuing a more cost-effective and sustainable energy storage. Here, two classes of sulfonated -NH-linked covalent organic frameworks (COFs), specifically designed for sodium or potassium ion conduction (named i-COF-2 (Na or K) and i-COF-3 (Na or K)), were synthesized through a straightforward, one-step process using affordable starting materials. Remarkably, these COFs demonstrate high ionic conductivity at room temperature─3.17 × 10-4 and 1.02 × 10-4 S cm-1 for i-COF-2 (Na) and i-COF-2 (K) and 2.75 × 10-4 and 1.42 × 10-4 S cm-1 for i-COF-3 (Na) and i-COF-3 (K)─without the need for additional salt or solvent. This enhanced performance, including low activation energies of 0.21 eV for both i-COF-2 (Na) and i-COF-2 (K) and of 0.24 and 0.25 eV for i-COF-3 (Na) and i-COF-3 (K), is attributed to the strategic incorporation of sulfonate groups and the directional channels within the COF structure. The Na+ and K+ ion high conductivities, low cost, and intrinsic framework stability of i-COF-2 (Na or K) and i-COF-3 (Na or K) provide promising solid electrolyte candidates for the exploration of sustainable energy storage.

Gold-Modified Covalent Organic Frameworks-Assisted Laser Desorption/Ionization Mass Spectrometry for Analysis of Metabolites Induced by Triclosan Exposure.

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) holds great promise for the rapid and sensitive detection of biomolecules, but its precise detection of small molecule metabolites is hindered by severe background interference from the organic matrix in the low molecular weight range. To address this issue, nanomaterials have commonly been utilized as substrates in LDI-MS. Among them, covalent organic frameworks (COFs), known for their unique optical absorption and structural properties, have garnered significant attention. Despite these advantages, their low ionization efficiency remains a challenge. Herein, a composite material of COF-S@Au nanoparticles (NPs), by incorporating Au NPs into a sulfur-functionalized COF (COF-S) through postsynthetic modification, was designed and adopted as substrates. This hybrid material leverages the synergistic effects of COF-S and Au NPs to improve the desorption/ionization efficiency and minimize background interference. The COF-S@Au NPs demonstrated a 5-16-fold improvement in MS signals of small biomolecules along with a clean background and excellent resistance to salt and protein interference. Their corresponding limits of detection (LODs) were achieved at ∼pmol. Furthermore, the COF-S@Au NPs were applied to analyze metabolites in a triclosan (TCS)-exposed mouse model, successfully identifying 10 differential metabolites associated with TCS toxicity. This work provides a foundation for developing advanced LDI-MS materials for high-performance metabolic analysis and offers valuable insights into TCS metabolic toxicity with potential applications in environmental toxicology.

Insights into excitonic behavior in single-atom covalent organic frameworks for efficient photo-Fenton-like pollutant degradation

The generation of radicals through photo-Fenton-like reactions demonstrates significant potential for remediating emerging organic contaminants (EOCs) in complex aqueous environments. However, the excitonic effect, induced by Coulomb interactions between photoexcited electrons and holes, reduces carrier utilization efficiency in these systems. In this study, we develop Cu single-atom-loaded covalent organic frameworks (CuSA/COFs) as models to modulate excitonic effects. Temperature-dependent photoluminescence and ultrafast transient absorption spectra reveal that incorporating acenaphthene units into the linker (CuSA/Ace-COF) significantly reduces exciton binding energy (Eb). This modification not only enhances peroxymonosulfate adsorption at Cu active sites but also facilitates rapid electron transfer and promotes selective hydroxyl radical generation. Compared to CuSA/Obq-COF (Eb = 25.6 meV), CuSA/Ace-COF (Eb = 12.2 meV) shows a 39.5-fold increase in the pseudo-first-order rate constant for sulfamethoxazole degradation (0.434 min−1). This work provides insights into modulating excitonic behavior in single-atom catalysts via linker engineering for EOCs degradation.

Strategic Nitrogen Site Alignment in Covalent Organic Frameworks for Enhanced Performance in Aqueous Zinc-Iodide Batteries.

Aqueous zinc-iodine batteries (AZIBs) are gaining attention as next-generation energy storage systems due to their high theoretical capacity, enhanced safety, and cost-effectiveness. However, their practical application is hindered by challenges such as slow reaction kinetics and the persistent polyiodide shuttle effect. To address these limitations, we developed a novel class of covalent organic frameworks (COFs) featuring electron-rich nitrogen sites with varied density and distribution (N1-N4) along the pore walls. These nitrogen sites enhance iodine species confinement and mass transport. Our experimental and theoretical studies reveal that the continuous and optimized distribution of nitrogen sites within the COF structure significantly reduces internal resistance and boosts redox activity. Moreover, the N4-COF demonstrates superior performance compared to other porous materials, due to its high density and strategic alignment of active sites. The I2@N4-COF cathode achieves a remarkable specific capacity of 348 mAh g⁻¹ at 1 C, almost 1.8 times greater than that of the I2@N1-COF, while also maintaining excellent cycling stability. This integration of a porous framework with aligned nitrogen sites in the N4-COF structure not only enhances iodine redox behavior but also offers a promising design strategy for developing high-performance AZIB electrodes.

Efficient adsorption and detection of steroid hormones in foods through the combination of novel magnetic TAPB-COF materials with click isotope probes.

Matrix effects pose a significant challenge in food analysis for the quantitative analysis of complex food samples. Herein, a novel magnetic covalent organic framework nanocomposite and the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction-based stable isotope labeling (SIL) method were presented for highly selective and sensitive detection of steroid hormones in food samples using HPLC-MS/MS. The nanocomposite, Fe3O4@TAPB-COF, with acore-shell structure exhibited high adsorption capacities for steroid hormones. Combined with a SIL method based on the CuAAC click reaction, steroid hormones were accurately quantified in food samples with high sensitivity and selectivity. A pair of SIL agents, N-(2-azidoethyl)aniline (d0-NAEA) and d5-N-(2-azidoethyl)aniline (d5-NAEA), was synthesized to label steroid hormones in the samples and standard solutions, respectively. The labeling reaction is highly specific, and the formation of the derivatives is easily ionized by MS, thus overcoming matrix effects. More surprisingly, the ionization efficiency of steroid hormones increased by a factor of 4 to 56, with matrix effects ranging from 87.3 to 99.3%. Under optimal conditions, this method exhibited a low limit of detection (LOD) ranging from 0.1 to 2.6 μg L-1 and overcame the interference of matrix effects for trace-level steroid hormone analysis in foodstuffs.

Isoelectronic Organic Dye-Based Covalent Organic Framework with Varied Nitrogen Content for Tuning Optoelectronic Properties and Photocatalytic H2 Evolution

Isoelectronic Organic Dye-Based Covalent Organic Framework with Varied Nitrogen Content for Tuning Optoelectronic Properties and Photocatalytic H₂ Evolution

Strategic Nitrogen Site Alignment in Covalent Organic Frameworks for Enhanced Performance in Aqueous Zinc‐Iodide Batteries

Strategic Nitrogen Site Alignment in Covalent Organic Frameworks for Enhanced Performance in Aqueous Zinc‐Iodide Batteries

Customized Design of Covalent Organic Framework with Asymmetric Dual-Function Hybrid Linkages for Promoting H2O2 Photosynthesis in Air and Water.

Efficient sacrificial-agent-free photosynthesis of H2O2 from air and water represents the greenest, lowest-cost, most real-time avenue for H2O2 production but remains a challenging issue. Here, we show a general and effective approach through a structural design on covalent organic frameworks (COFs) with asymmetric dual-function hybrid linkages for boosting the H2O2 photosynthesis of the COFs. Through such design we can equip a COF with not only a catalytic active center but also a special function for isolating the D-A motif, which consequently endows the COF (CI-COF) built on asymmetric dual-function hybrid linkages with a significantly enhanced efficiency in the generation, transmission, and separation of photogenerated carriers, relative to the COF (II-COF and CC-COF) built on symmetric single-function single linkages. Correspondingly, the performance of H2O2 photosynthesis is enhanced by three or five times. Accompanied is the largely promoted O2 utilization and conversion efficiency from 36.6% to 99.9%. A rare dual-channel H2O2 photosynthesis is suggested for the CI-COF.

Electron Push-Pull Effect of Benzotrithiophene-Based Covalent Organic Frameworks on the Photocatalytic Degradation of Pharmaceuticals and Personal Care Products

A covalent organic framework (COF) has emerged as a promising photocatalyst for the removal of pharmaceutical and personal care product (PPCP) contaminants; however, high-performance COF photocatalysts are still scarce. In this study, three COF photocatalysts were successfully synthesized by the condensation of benzo[1,2-b:3,4-b′:5,6-b′′]trithiophene-2,5,8-tricarbaldehyde (BTT) with 4,4′,4′′-(1,3,5-triazine-2,4,6-triyl)trianiline (TAPT), 1,3,5-Tris(4-aminophenyl)benzene (TAPB), and 4,4′,4′′-nitrilotris(benzenamine) (TAPA), namely, BTT-TAPA, BTT-TAPB, and BTT-TAPT, respectively. The surface areas of BTT-TAPA, BTT-TAPB, and BTT-TAPT were found to be 800.46, 1203.60, and 1413.58 cm2∙g−1, respectively, providing abundant active sites for photocatalytic reactions. Under visible-light irradiation, BTT-TAPT exhibited the highest removal rate of tetracycline (TC), reaching 82.7% after 240 min. The superior photocatalytic performance of BTT-TAPT was attributed to its large specific surface area and the strong electron-acceptor properties of the triazine group. Electron paramagnetic resonance capture experiments and liquid chromatograph mass spectrometer analysis confirmed that superoxide radicals played a pivotal role in the degradation of TC and ciprofloxacin. Moreover, BTT-TAPT exhibited high stability and reproducibility during the photocatalytic degradation process. This study confirms that BTT-based COFs are a class of promising photocatalysts for the degradation of PPCPs in water, and their performance can be further optimized by tuning the structure and composition of the frameworks.

Supramolecularly Built Local Electric Field Microenvironment around Cobalt Phthalocyanine in Covalent Organic Frameworks for Enhanced Photocatalysis.

The local electric field (LEF) plays an important role in the catalytic process; however, the precise construction and manipulation of the electric field microenvironment around the active site remains a significant challenge. Here, we have developed a supramolecular strategy for the implementation of a LEF by introducing the host macrocycle 18-crown-6 (18C6) into a cobalt phthalocyanine (CoPc)-containing covalent organic framework (COF). Utilizing the supramolecular interaction between 18C6 and potassium ion (K+), a locally enhanced K+ concentration around CoPc can be built to generate a LEF microenvironment around the catalytically active Co site. The COF with this supramolecularly built LEF realizes an activity of up to 7.79 mmol mmolCo-1 h-1 in the photocatalytic CO2 reduction reaction (CO2RR), which is a 180% improvement compared to its counterpart without 18C6 units. The effect of LEF can be subtly controlled by fully harnessing the K+@18C6 interaction by changing the potassium salts with different counterions. In situ spectroscopy and density functional theory calculations show that the complexation of K+ by 18C6 creates a positive electric field that stabilizes the critical intermediate *COOH involved in CO2RR, which can be tuned by the halide ion-mediated K+@18C6 interaction and hydrogen-bonding interaction, consequently leading to improved catalytic performance to varying degrees.

Enhancing Photocatalytic CO2RR by Modulating the Active Sites of COF-Based Catalysts.

The catalytic conversion of CO2 into valuable chemicals using metalized covalent organic frameworks (COFs) as catalysts is a promising method for reducing atmospheric CO2 levels. Herein, a aldehyde-amine COF (TAPT-Tp) at room temperature and pressure and their metallized results is synthesized, Ni-TAPT-Tp and Ti-TAPT-Tp. The photocatalytic results indicate that the CO2 to CO reduction rate is 6182.5µmol g-1h-1 for Ni-TAPT-Tp, but only 1615.4µmol g-1h-1 for Ti-TAPT-Tp. Density functional theory (DFT) simulations further demonstrate that for intermediates *CO2, *COOH, and *CO, the energy of Ni-TAPT-Tp is consistently lower than that of Ti-TAPT-Tp, indicating that Ni-TAPT-Tp exhibits superior photocatalytic performance for CO2RR. This work provides a reference for optimizing the coordination structure of M-COFs to obtain highly active and selective CO2RR.

Photoenzyme Coupling System: Covalent Organic Frameworks In Situ Production of Hydrogen Peroxide Cascaded with Unspecific Peroxygenase to Achieve C-H Bonds Selective Activation.

As an efficient, sustainable, and environmentally friendly semiconductor material, covalent organic frameworks (COFs) can generate hydrogen peroxide (H2O2) by photocatalysis, attracting wide attention in recent years. Herein, the effects of hydroxyl, methoxyl, and vinyl groups of imide-linked two-dimensional (2D) COFs on the photocatalytic production of H2O2 were studied theoretically and experimentally. The introduction of vinyl groups greatly promotes the photogenerated charge separation and migration of COFs, providing more oxygen adsorption sites, stronger proton affinity, and lower intermediate binding energy, which effectively facilitates the rapid conversion of oxygen to H2O2. Further, we have integrated the properties of the photocatalytic in situ generation of H2O2 by COFs and the continuous consumption of H2O2 by unspecific peroxygenases (UPOs) to construct a mild and simple photoenzyme coupling system that can achieve selective activation of C-H bonds without the need of any external oxidants or sacrificial agents. This simple, stable, and compatible photoenzyme system avoids irreversible enzyme damage caused by excessive exogenous H2O2 and the utilization of sacrificial agents, thus providing an efficient and green pathway for fine chemical synthesis. This system not only breaks the restriction of continuous exogenous H2O2 supplementation on the UPO catalytic system but also provides a new practical application direction for semiconductor photocatalytic H2O2 production.

Spatiotemporal Spectroscopy of Fast Excited-State Diffusion in 2D Covalent Organic Framework Thin Films.

Covalent organic frameworks (COFs), crystalline and porous conjugated structures, are of great interest for sustainable energy applications. Organic building blocks in COFs with suitable electronic properties can feature strong optical absorption, whereas the extended crystalline network can establish a band structure enabling long-range coherent transport. This peculiar combination of both molecular and solid-state materials properties makes COFs an interesting platform to study and ultimately utilize photoexcited charge carrier diffusion. Herein, we investigated the charge carrier diffusion in a two-dimensional COF thin film generated through condensation of the building blocks benzodithiophene-dialdehyde (BDT) and N,N,N',N'-tetra(4-aminophenyl)benzene-1,4-diamine (W). We visualized the spatiotemporal evolution of photogenerated excited states in the 2D WBDT COF thin film using remote-detected time-resolved PL measurements (RDTR PL). Combined with optical pump terahertz probe (OPTP) studies, we identified two diffusive species dominating the process at different time scales. Initially, short-lived free charge carriers diffuse almost temperature-independently before relaxing into bound states at a rate of 0.7 ps-1. Supported by theoretical simulations, these long-lived bound states were identified as excitons. We directly accessed the lateral exciton diffusion within the oriented and crystalline film, revealing remarkably high diffusion coefficients of up to 4 cm2 s-1 (200 K) and diffusion lengths of several hundreds of nanometers and across grain boundaries. Temperature-dependent exciton transport analysis showed contributions from both incoherent hopping and coherent band-like transport. In the transport model developed based on these findings, we discuss the complex impact of order and disorder on charge carrier diffusion within the WBDT COF thin film.

An sp2 Carbon‐Conjugated Covalent Organic Framework for Fusing Lipid Droplets and Engineered Macrophage Therapy

Engineered immune cell therapy has proven to be a transformative cancer treatment despite the challenges of its prohibitive costs and manufacturing complexity. In this study, we propose a concise “lipid droplet fusion” strategy for engineering macrophages. Because of the integration of hydrophobic alkyl chains and π‐conjugated structures, the mildly synthesized sp2C‐conjugated covalent organic framework (COF) UM‐101 induced lipid droplet fusion and metabolic reprogramming of macrophages, thus promoting their antitumor classical activation. Intravenous injection of UM‐101–engineered macrophages effectively inhibited tumor progression. These results represent the first report of room‐temperature synthesis of sp2C‐conjugated COFs for engineered immune cell therapy, providing a new perspective for the development of therapeutic immune cells via organelle manipulation.

3D Covalent Organic Framework Membrane with Interactive Ion Nanochannels for Hydroxide Conduction.

Crystalline porous materials, known for their ordered structures, hold promise for efficient hydroxide conductivity in alkaline fuel cells with limited ionic densities. However, the rigid cross-linking of porous materials precludes their processing into membranes, while composite membranes diminish materials' conductivity advantage due to the interrupted phases. Here, we report a self-standing three-dimensional covalent organic framework (3D COF) membrane with efficient OH-transport through its interconnected 3D ionic nanochannels. The large-area, homogeneously connected COF membrane, with an 8 cm diameter and 20 μm thickness, was prepared using an interface polymerization strategy assisted by sacrificial templates of a polyacrylonitrile membrane. At the microscopic level, the introduction of imidazolium salt-building units resulted in a noninterpenetrated structure of 3D COF, creating a 3D interactive continuous hydrophilic channel for OH--conduction. The 3D COF membrane demonstrated high conductivity (169 mS/cm at 80 °C, 100% humidity) and achieved a peak power density of 160 mW/cm2 in H2/O2 single-cell tests. This COF interface polymerization strategy brings new possibilities to address the challenges of porous material membrane formation and is expected to advance their practical applications in the field of ion transport.

An sp2 Carbon-Conjugated Covalent Organic Framework for Fusing Lipid Droplets and Engineered Macrophage Therapy.

Engineered immune cell therapy has proven to be a transformative cancer treatment despite the challenges of its prohibitive costs and manufacturing complexity. In this study, we propose a concise "lipid droplet fusion" strategy for engineering macrophages. Because of the integration of hydrophobic alkyl chains and π-conjugated structures, the mildly synthesized sp2C-conjugated covalent organic framework (COF) UM-101 induced lipid droplet fusion and metabolic reprogramming of macrophages, thus promoting their antitumor classical activation. Intravenous injection of UM-101-engineered macrophages effectively inhibited tumor progression. These results represent the first report of room-temperature synthesis of sp2C-conjugated COFs for engineered immune cell therapy, providing a new perspective for the development of therapeutic immune cells via organelle manipulation.

Recent advances in nanoporous organic polymers (NPOPs) for hydrogen storage applications.

Nanoporous organic polymers (NPOPs) have emerged as versatile materials with robust thermal stability, large surface area (up to 2500 m2 g-1), and customizable porosity, making them ideal candidates for advanced hydrogen (H2) storage applications. This review provides a comprehensive analysis of various NPOPs, including covalent organic frameworks (COFs), hypercrosslinked polymers (HCLPs), conjugated microporous polymers (CMPs), and porous aromatic frameworks (POAFs). Notably, these materials demonstrate superior H2 storage capacities, achieving up to 10 wt% at cryogenic temperatures, which is essential for applying H2 as a clean energy carrier. The review also highlights recent advancements, such as integrating metal-organic frameworks (MOFs) into NPOPs, further enhancing storage capacities by up to 30%. Their multifaceted properties underpin various applications, from fuel storage and gas separation to water treatment and optical devices. This review explores the significance and versatility of NPOPs in H2 storage due to their unique properties and enhanced storage capacities. Additionally, recent advancements in utilizing NPOPs for H2 storage are highlighted with a detailed discussion of emerging trends and the synthesis of innovative NPOPs. The review concludes with a discussion of the advantages, applications, challenges, research, and future directions for research in this area.

Construction of Luminescent Three-Dimensional Covalent Organic Frameworks for Molecular Decoding of Wide Organic Compounds.

Constructing highly conjugated three-dimensional covalent organic frameworks (3D COFs), particularly those with luminescent features, remains a significant challenge. In this work, we successfully synthesized a 3D COF, named 3D-Py-SP-COF, using a rigid and orthogonal spirobifluorene building block for the spatial 3D structure construction and planar pyrene as luminescent units. The incorporation of the pyrene and the unique rigid 3D network structure endow 3D-Py-SP-COF with fluorescent properties. The successful formation of this 3D COF was verified by FT-IR, solid-state 13C CP-MAS NMR. Structural simulations based on the experimental powder X-ray diffraction analysis revealed that 3D-Py-SP-COF adopted a two-fold interpenetrated pts topology. The highly conjugated porous framework and fluorescent nature allow precise detection and localization of more than two dozen volatile organic compounds (VOCs), including aromatics, alcohols, and other commonly encountered industrial VOCs.

Visualizing stepwise evolution of carbon hybridization from sp3 to sp2 and to sp

Regulating carbon hybridization states lies at the heart of engineering carbon materials with tailored properties but orchestrating the sequential transition across three states has remained elusive. Here, we visiualize stepwise evolution in carbon hybridizations from sp³ to sp² and to sp states via dehydrogenation and elimination reactions of methylcyano-functionalized molecules on surfaces. Utilizing scanning probing microscopy, we distinguish three distinct carbon-carbon bond types within polymers induced by annealing at elevated temperatures. Density-functional-theory calculations unveil the pivotal role of the electron-withdrawing cyano group in activating neighboring methylene to form C(sp3)–C(sp3) bonds, and in facilitating subsequent stepwise HCN eliminations to realize the transformation across three carbon-carbon bond types. We also demonstrate the applicability of this strategy on one-dimensional molecular wires and two-dimensional covalent organic framework on different substrates. Our work expands the scope of carbon hybridization evolution and serves as an advance in flexibly engineering carbon-material by employing cyanomethyl-substituted molecules.

Crystalline porous frameworks based on double extension of metal–organic and covalent organic linkages

Abstract Reticular chemistry is a powerful strategy to design materials with fine-tuned chemical functionality and porosity, such as metal–organic frameworks (MOFs) and covalent organic frameworks (COFs). MOFs typically show high crystallinity due to their reversible coordinative bonds, and the organic backbone of COFs provides chemical stability. Here we synthesize metal–organic–covalent–organic frameworks (MOCOFs) that combine both crystallinity and stability in a single framework by the double extension of metal–organic and covalent organic linkages. Several MOCOFs are obtained by reaction between a cobalt aminoporphyrin and dialdehydes, which are interconnected by cobalt–amine coordination and imine condensation to form three-dimensional networks. The MOCOFs exhibit chiral topological nets, large surface areas, high crystallinities and high chemical stabilities due to the two types of extended linkages. Thus, MOCOFs present a reticular design strategy that further diversifies the chemical and structural space of porous solids.