Mesoporous Covalent Organic Framework Research Articles

Accurate HER2 determination in breast cancer: a prominent COF-immobilized enzyme-enhanced electrochemical aptasensor employing 4-acetamidophenol as an efficient mediator

An effective strategy for enzyme-enhanced electrochemical detection of human epidermal growth factor receptor 2 (HER2) is proposed for breast cancer diagnosis. This strategy utilizes a three-dimensional mesoporous covalent organic framework (COF), immobilized horseradish peroxidase (HRP), and a novel redox mediator, 4-acetamidophenol (APAP). The mesoporous structure, with encapsulation effect, and good biocompatibility of COF, makes the functionalized COF an efficient carrier for HRP immobilization (HRP-Ab-AuNPs@COF). It demonstrates superior catalytic activity, stability, and electrochemical performance compared to free HRP, thus making it an ideal probe for simultaneous target recognition and signal amplification. APAP is screened from four candidate phenolic compounds based on its high formal potential (0.32 V vs. Ag/AgCl), rapid electron transfer activity (kapp = 2.80 × 105 M− 1 s− 1), excellent solubility and stability. These properties prove significantly better than the conventional mediator hydroquinone (HQ), achieving a higher signal-to-background ratio. By integrating decorated multi-walled carbon nanotubes as substrate materials, the electrochemical aptasensor achieves a low HER2 detection limit (0.418 pg mL− 1) with high specificity. This method’s selectivity surpasses that of the HQ-mediated method by 59–73%. Moreover, the aptasensor can effectively distinguish breast cancer patients and healthy individuals, as well as patients at different stages of the disease with high accuracy (AUC = 0.928). This performance exceeds traditional biomarkers CEA and CA15-3. This work paves novel avenues for innovative applications of COF-immobilized enzymes and the novel mediator APAP in electrochemical biosensing, thus holding significant promise for individualized breast cancer diagnosis and treatment.

Three-Dimensional Mesoporous Covalent Organic Framework for Photocatalytic Oxidative Dehydrogenation to Quinoline.

Developing precious metal-free catalysts for organic reactions under mild conditions is urgent. Herein, we report a three-dimensional covalent organic framework (3D-COF) with high crystallinity and permanent pores, termed 3D-TABPA-COF, for the oxidation of tetrahydroquinoline to quinoline. The 3D-TABPA-COF assembled based on N4,N4-bis(4'-amino-[1,1'-biphenyl]-4-yl)-[1,1'-biphenyl]-4,4'-diamine (TABPA) is the catalytic active center for the conversion of tetrahydroquinoline. The triphenylamine in the structure is an effective photosensitizer, which not only enhances the light absorption capacity but also facilitates the rapid transfer of photogenerated electrons and ensures effective carrier separation. The obtained 3D-TABPA-COF has a high specific surface area (2745.06 m2 g-1) and mesopores of 3.57 nm. This is attributed to the fact that the bor topology is not easy to interpenetrate. It can oxidize tetrahydroquinoline to obtain quinoline efficiently under visible light irradiation. In addition, we also performed various photochemical characterizations combined with density functional theory calculations to elucidate the reaction mechanism from tetrahydroquinoline to quinoline. This work provides a feasible strategy for constructing 3D-COF to achieve efficient photocatalytic organic reactions.

Interweaving two dimensional mesoporous covalent organic frameworks for efficient removal of mercury from aqueous solution

The current study defines the ultrasound-assisted solvothermal synthesis of covalent organic frameworks (COFs) using a combination of 4,4′-diaminobiphenyl and trialdehyde (BDTA-COF). The X-ray diffraction (XRD) studies confirm the formation of COF, which aligns better with AA stacking than AB stacking. The morphology of the formed COFs is a flower-like structure. The Fourier transform infrared spectroscopic (FTIR) results show that imine linkages are forming and that the aldehayde and amine peaks are not present. The formed BDTA-COF was found to be mesoporous and exhibit 2.4 nm pore size with 472 m2g−1 surface area. BDTA-COF has been evaluated for the effective removal of Hg+ from an aqueous solution through adsorption. Maximum adsorption efficiency (99 %) was achieved by optimizing the parameters like selectivity of metal, concentration, pH, amount of adsorbent. The nitrogen atoms from the imine linkages and the oxygen atoms in BDTA-COF are the primary active sites for effective adsorption of Hg⁺. The adsorption kinetics control the chemisorption of Hg+ with the BDTA-COF's imine group since the results fit well with the pseudo-second-order model. Among the various isotherm models, the BDTA-COF/Hg+ system followed the Langmuir model and insists on the monolayer adsorption phenomena. After adsorption, the XRD shows a slight change in peak positions, and the SEM image indicates the deposition of micrometer-sized particles onto the BDTA-COF. After adsorption, FTIR and X-ray photoelectron spectroscopic (XPS) tests show the interaction of functional groups of BDTA-COF and Hg+. High surface area, covalency, porosity, ordered confinement, imine linkages and stability of COFs could be the reasons for good adsorption efficiency and need additional tuning for practical applications for adsorption removal of pollutants from water.

Fast Production of Covalent Organic Frameworks for Covalent Enzyme Immobilization with Boosted Enzymatic Catalysis by Solar‐Driven Photothermal Effect

AbstractDeveloping new enzyme‐immobilization systems to stabilize their dynamic structures and meanwhile enhance their catalytic activity is of great significance but very challenging. Herein, we design and fabricate a class of robust mesoporous covalent organic frameworks (COFs) via Michael addition‐elimination reaction. It is found that highly crystalline COFs can be produced in 10 min, which is attributed to the promoting effect of the intramolecular hydrogen bond activation. The COFs rich in hydroxyl groups can be facilely post‐modified by epibromohydrin to covalently immobilize enzymes with both high loading and activity. Furthermore, we create a solar‐driven photothermal‐promoted strategy by introducing photoactive azo groups to COF carriers, which can boost the enzyme catalytic performance (lipase) with much higher conversion of various racemic substrates and chiral resolution upon solar light irradiation. The heterogeneous biocatalysts also demonstrate exceptional reusability and stability. This work provides a green and energy‐efficient approach to facilitate the scale application of enzyme‐immobilized biocatalysts.

Fast Production of Covalent Organic Frameworks for Covalent Enzyme Immobilization with Boosted Enzymatic Catalysis by Solar-Driven Photothermal Effect.

Developing new enzyme-immobilization systems to stabilize their dynamic structures and meanwhile enhance their catalytic activity is of great significance but very challenging. Herein, we design and fabricate a class of robust mesoporous covalent organic frameworks (COFs) via Michael addition-elimination reaction. It is found that highly crystalline COFs can be produced in 10 min, which is attributed to the promoting effect of the intramolecular hydrogen bond activation. The COFs rich in hydroxyl groups can be facilely post-modified by epibromohydrin to covalently immobilize enzymes with both high loading and activity. Furthermore, we create a solar-driven photothermal-promoted strategy by introducing photoactive azo groups to COF carriers, which can boost the enzyme catalytic performance (lipase) with much higher conversion of various racemic substrates and chiral resolution upon solar light irradiation. The heterogeneous biocatalysts also demonstrate exceptional reusability and stability. This work provides a green and energy-efficient approach to facilitate the scale application of enzyme-immobilized biocatalysts.

Ultrasound-assisted rapid growth of chemically bonded bifunctional mesoporous covalent organic framework submicrospheres on a nickel-chromium alloy support for efficient solid-phase microextraction of bisphenols from water and milk samples

A layer-by-layer chemical bonding strategy was developed for fast in situ growth of bifunctional mesoporous covalent organic framework submicrospheres (COF SMSs) on the nickel-chromium alloy (Ni-Cr) fiber substrate via the ultrasound-assisted Schiff-base reaction for the first time. COF SMSs showed well-defined morphology, extraordinary high surface area (1211 m2·g−1) and narrow mesopore (2.50 nm) as well as excellent stability. Furthermore, the resulting Ni-Cr fiber presented outstanding adsorption capability and improved selectivity for bisphenols (BPs). Consequently, an attractive SPME-HPLC-UV approach with the Ni-Cr@Ni-Cr LDHs NSs@COF SMSs fiber was proposed for rapid preconcentration and sensitive determination of BPs. By optimizing adsorption parameters, the SPME-HPLC-UV method presented good linearity for five BPs in the ranges of 0.02–200 ng·mL−1 with coefficients of determination (R2) higher than 0.999. Limits of detection and limits of quantitation were obtained from 0.003 ng·mL−1 to 0.006 ng·mL−1 and from 0.010 to 0.019 ng·mL−1, respectively. Moreover, the intra-day and inter-day precision expressed as relative standard deviations (RSDs) was 1.57–3.52 % and 2.65–4.38 % for the proposed method with a single fiber, respectively. RSDs of the proposed method with different duplicate fibers were 3.25–6.72 %. The proposed SPME-HPLC-UV method was available for efficient preconcentration and sensitive detection of five BPs from real water and milk samples. The relative recoveries at three spiking levels of BPs were achieved in the range of 80.00–118.8 % with RSDs below 7.81 %. In addition, the prepared fiber still exhibited satisfactory adsorption performance after 120 adsorption-desorption cycles.

Exceptional Anhydrous Proton Conduction in Covalent Organic Frameworks.

Covalent organic frameworks (COFs) offer an irreplaceable platform for mass transport, as they provide aligned one-dimensional channels as pathways. Especially, proton conduction is of great scientific interest and technological importance. However, unlike proton conduction under humidity, anhydrous proton conduction remains a challenge, as it requires robust materials and proceeds under harsh conditions. Here, we report exceptional anhydrous proton conduction in stable crystalline porous COFs by integrating neat phosphoric acid into the channels to form extended hydrogen-bonding networks. The phosphoric acid networks in the pores are stabilized by hierarchical multipoint and multichain hydrogen-bonding interactions with the 3D channel walls. We synthesized five hexagonal COFs that possess different pore sizes, which are gradually tuned from micropores to mesopores. Remarkably, mesoporous COFs with a high pore volume exhibit an exceptional anhydrous proton conductivity of 0.31 S cm-1, which marks the highest conductivity among all examples reported for COFs. We observed that the proton conductivity is dependent on the pore volume, pore size, and content of phosphoric acid. Increasing the pore volume improves the proton conductivity in an exponential fashion. Remarkably, changing the pore volume from 0.41 to 1.60 cm3 g-1 increases the proton conductivity by 1150-fold. Interestingly, as the pore size increases, the activation energy barrier of proton conduction decreases in linear mode. The mesopores enable fast proton hopping across the channels, while the micropores follow sluggish vehicle conduction. Experiments on tuning phosphoric acid loading contents revealed that a well-developed hydrogen-bonding phosphoric acid network in the pores is critical for proton conduction.

Quaternary Ammonium-Functionalized Mesoporous Covalent Organic Frameworks for Effective Catalytic CO2 Cycloaddition

Quaternary Ammonium-Functionalized Mesoporous Covalent Organic Frameworks for Effective Catalytic CO₂ Cycloaddition

Facile room-temperature synthesis of a spherical mesoporous covalent organic framework for capillary electrochromatography

Herein, a spherical covalent organic framework COF TAPB-DMTP was facilely synthesized from 2,5-dimethoxyterephthalaldehyde (DMTP) and 1,3,5-tri-(4-aminophenyl)benzene (TAPB) as monomers. COF TAPB-DMTP with regular mesoporous and excellent mass transfer ability was first introduced into the capillary and immobilized on the inner wall of the capillary through a simple in situ growth method. Through various characterization results, COF TAPB-DMTP was successfully prepared and modified onto the capillary inner wall. The separation performance and potential of COF TAPB-DMTP modified capillary column was explored. The new developed COF modified column achieved a highly efficiency and selective separation between analytes with different properties, including halogeno benzenes, alkylbenzenes, phenols and sulfonamides. Satisfactory stability and reproducibility were observed on COF TAPB-DMTP modified columns. The intraday, interday and three batch columns relative standard deviations were all less than 1.85 % for the retention time. The separation performance of prepared column has no significant change after 90 continuous runs. Additionally, the COF TAPB-DMTP modified capillary column was successfully used for separation and detection of triazole antifungal drugs in human plasma, and the recoveries of three antifungal drugs (fluconazole, isavuconazole and posaconazole) in spiked samples were in the range of 98.6–100.8 %, 92.4–102.1 % and 99.9–107.5 %, respectively. This self-made column showed excellent application potential in chromatography separation science.

Design, Synthesis, and Applications of Mesoporous Covalent Organic Frameworks

Design, Synthesis, and Applications of Mesoporous Covalent Organic Frameworks

Melamine-based covalent organic frameworks intercalated montmorillonite for photocatalytic and antibacterial applications

In the present work, copper oxide materials such as cuprous oxide (Cu2O) and cupric oxide (CuO), as transition metal oxide was successfully included on montmorillonite (Mt)/Covalent organic frameworks (COFs) composite, have been constructed by a facile solvothermal method, and their monomer blocks subsequent assembled into mesoporous COFs, schiff base network-1 (SNW-1), that was intercalated into the montmorillonite layers of a novel nanocomposite (Mt/COF-CuO/Cu2O) for simultaneous antibacterial and heterogeneous photocatalyst performance to degradation of textile important industrially dye such as methyl green (MG) from wastewater. The structures and properties of the resulting materials were then systematically characterized using a series of analytical techniques. The XRD pattern of Mt/COF-CuO/Cu2O nanocomposite confirmed that the formation of CuO and Cu2O nanoparticles in the monoclinic and octahedral phase, respectively. The SEM images of Mt/COF nanocomposite displayed the interfacial connections between irregular spherical grains shape of COF and the layers flat montmorillonite. Mt/COF modified by CuO/Cu2O with plate-shaped morphology and an average width of 50 nm. The diffuse reflectance spectra showed the presence of both Cu2O and CuO nanoparticles in Mt/COF-CuO/Cu2O. The new synthesized photocatalyst showed excellent activity under visible light and was used for the photodegradation of methyl green as target cationic pollutant. The effects of COF incorporation and CuO/Cu2O on the photocatalytic performance have been discussed in detail. In this process, the effects of various parameters such as pH, weight of adsorbent, and concentration of the dye was optimized. The mechanism of separation of the photogenerated electrons and holes at the Mt/COF-CuO/Cu2O nanocomposite was discussed. The antibacterial testing results showed that antibacterial activity of Mt/COF-CuO/Cu2O nanocomposite was more than CuO nanoparticles and Mt/COF against Escherichia coli and Bacillus subtilis.

Tuning the exciton binding energy of covalent organic frameworks for efficient photocatalysis

Owing to the large exciton binding energy (>100 meV) of most organic materials, the process of exciton dissociation into free electrons and holes is seriously hindered, which plays a key role in the photocatalytic system. In this study, a series of chalcogen (S, Se)-substituted mesoporous covalent organic frameworks (COFs) have been synthesized for enhanced photocatalytic organic transformations. Photoelectrochemical measurements indicate that the introduction of semi-metallic Se atom and the enlargement of conjugation degree can not only reduce the exciton binding energy accelerating the charge separation, but also reduce the band gap of COFs. As a result, the COF-NUST-36 with the lowest exciton binding energy (39.5 meV) shows the highest photocatalytic performance for selective oxidation of amines (up to 98% Conv. and 97.5% Sel.). This work provides a feasible method for designing COFs with high photocatalytic activity by adjusting exciton binding energy.

Amino-Functionalized Ionic-Liquid-Grafted Covalent Organic Frameworks for High-Efficiency CO2Capture and Conversion

Rationally integrating desired functional components into a composite material can endow the tailored function to achieve the corresponding purpose. This is the first case where a series of [AeImBr]X%-TAPT-COFs (X = 0, 17, 33, 50, 67, 83, 100) were fabricated by chemically integrating the amino-functionalized imidazole ionic liquid (NH2-IL) onto channel walls of mesoporous covalent organic framework materials ([HO]X%-TAPT-COFs). By virtue of the polar groups (amino groups) and abundant imidazole cations of NH2-IL and its microporous nature, the obtained [AeImBr]X%-TAPT-COFs exhibit higher CO2 capture activity than [HO]X%-TAPT-COFs. Correspondingly, the CO2 equilibrium capture capacity increases from 62.6 to 117.4 mg/g, which is crucial to the storage of enough CO2 around the catalytic active sites. Additionally, the synergistic effect of -NH2 and Br- in NH2-IL can also improve the cycloaddition reaction rate. The characteristics of [AeImBr]X%-TAPT-COFs contribute to the efficient generation of cyclic carbonate through heterogeneously catalyzing CO2-epoxide cycloaddition without any solvents and cocatalysts. Specifically, [AeImBr]83%-TAPT-COF has a CO2 equilibrium capture capacity of 117.4 mg/g and cyclochloroallyl carbonate yield of 99.1%. As a result of the use of the chemical grafting method, [AeImBr]X%-TAPT-COFs possess excellent stability and cycle life. The equilibrium capture capacity and cyclochloroallyl carbonate yield reach 112.7 mg CO2/g adsorbent and 95.0% at the eighth cycle.

Design of Nacre-Inspired 2D-MoS2 Nanosheets Assembled with Mesoporous Covalent Organic Frameworks (COFs) for Smart Coatings.

High loading capacity and smart release of inhibitors are the first and foremost characteristics of nanocontainers, which play a pivotal role in metal active corrosion protection. The present work explores the development of novel protective nanocontainers based on recently emerged covalent organic frameworks (COFs). These highly porous frameworks with large surface area, outstanding thermomechanical properties, low density, and ease of functionalization are used as nanocontainers. On the other hand, molybdenum disulfide (MoS2), a state-of-the-art 2D layered compound with a sheetlike structure, was utilized thanks to its excellent barrier properties. However, these lamellar structures suffer a high agglomeration tendency in polymeric matrices. Therefore, we developed a novel hybrid nanocontainer, inspired by natural nacre, by an in situ growth of COF on MoS2 to improve the stability and provide a high inhibitor loading capacity. The porous and nitrogen-rich structure of COF made it a good carrier to adsorb europium cations as inorganic inhibitors and release them on demand by pH changes to suppress the electrochemical reactions. The as-synthesized nanoplatforms were used as pH-responsive fillers in the epoxy resin. The nanocomposite coatings showed almost 50 kΩ cm2 total resistance and high impedance values (1011 Ω cm2) even after 77 days of immersion. Moreover, salt spray analysis depicted the smallest amount of rust and corrosion product after 31 days in the filled nanocomposite coating. Cathodic delamination and pull-off outcomes denoted that the filled coatings with the as-synthesized nanofiller showed the smallest cathodic delamination radius (3.41 mm) and lowest adhesion loss (24%) compared to the neat epoxy (7.55 mm and 46.7%). As such, the highly porous modified MoS2 nanosheets are considered promising alternatives in a wide range of applications with anticorrosion properties.

In situ passivation and thiol-mediated anchoring of perovskite quantum dots in mesoporous covalent-organic frameworks

Metal halide perovskite quantum dots (PQDs) are considered as promising candidate for the next generation optoelectronic applications. However, their development is severely restricted by their poor stability. Here, we demonstrate the in situ growth of PQDs in the ordered channels of functionalized covalent-organic frameworks (COFs). The strong S-Pb chemical binding firmly anchors the PQDs in COF matrix, which prevent the aggregation of PQDs and eliminate the nonradiative trap centers of PQDs, leading to the high photoluminescence quantum yield (81.5 %) and remarkable stability. Femtosecond transient absorption spectroscopy reveal the elimination of nonradiative trap centers in PQD@COFs. Theoretical simulation results demonstrate the strong waveguide effect in PQD@COFs, which reduces the reabsorption loss. Further, the obtained white light-emitting diode exhibits ultrahigh luminous efficiency of 89.6 lm/W and excellent operating stability, which paves the way for the commercial application of PQDs.

Mesoporous covalent organic framework microspheres with dual-phase separation strategy for high-purity glycopeptide enrichment

High-performance porous materials and rational enrichment strategies are crucial during sample pretreatment process in glycoproteomics analysis. Herein, we report a dual-phase separation strategy based on hydrophobic and hydrophilic mesoporous covalent-organic framework (COF) microspheres for high-purity glycopeptide enrichment for the first time. The COF microspheres (about 1.8±0.5 μm) with hydrophobic mesopores (2.5 nm) were prepared by a facile method at room temperature. Through the post-synthesis modification strategy, hydrophilic mesopores were obtained by modifying the vinyl ligands with glutathione (GSH), and the hydrophilic properties of COF microspheres were further enhanced by the introduction of Au nanoparticles and GSH to obtain the hydrophilic COF microspheres (denoted as COF@Au-GSH). The low-abundance hydrophilic glycopeptides could be efficiently enriched by the hydrophilic COF@Au-GSH microspheres in low polar solutions after the high-abundance hydrophobic non-glycopeptides were removed with the hydrophobic COF microspheres in high polar solutions. With the help of dual-phase separation strategy and inherent properties of the COF structure, the as-prepared COF microspheres showed splendid enrichment performance for glycopeptides, including ultrahigh sensitivity (2 fmol, IgG digests), extremely high specificity (1:10000, IgG digests/BSA digests), excellent size selectivity (1:500:500, IgG digests/BSA/IgG), and large binding capacity (200 mg g−1, IgG digests). In addition, a total of 1993 glycopeptides could be enriched and identified from the rat liver digests after enrichment by the COF microspheres. As a proof of concept application, the proposed strategy was successfully used in sample pretreatment process for plasma glycoproteomic analysis.

Rational design of imine‐linked three‐dimensional mesoporous covalent organic frameworks with bor topology

AbstractThree‐dimensional (3D) covalent organic frameworks (COFs) possess great potential applications in various fields. Constructing 3D COFs with large pore sizes is extremely challenging due to the interpenetration and collapse. Herein, we report a series of crystalline imine‐linked 3D COFs (3D‐bor‐COF‐1, 3D‐bor‐COF‐2, 3D‐bor‐COF‐3) with mesoporous channels through rationally designing the topology configuration. These 3D‐bor‐COFs display permanent porosity and Brunauer–Emmett–Teller (BET) surfaces of 3205.5, 1752.7, and 2077.3 m2 g−1 (SLangmuir = 4277.7, 2480.3, and 2698.0 m2 g−1), respectively. The pore sizes of 3D‐bor‐COFs were confirmed by the lattice fringes from high‐resolution transmission electron microscopy, as well as structural simulation and nitrogen adsorption isotherm analysis. 3D‐bor‐COFs display large pore sizes (3.8 nm for 3D‐bor‐COF‐3), which is among the highest record of 3D COFs. Owing to the unstacked‐aromatic pore environment and high specific surface area, 3D‐bor‐COFs display excellent adsorption capacity for benzene vapor (1203.9 mg g−1 for 3D‐bor‐COF‐3) under 298 K, which is three times higher than that of the best‐reported 2D COF. This work not only provides inspiration for designing 3D mesoporous imine‐COFs, but also demonstrates a strategy for constructing aromatics adsorption materials.

Fine-tuned mesoporous covalent organic frameworks for highly efficient low molecular-weight proteins separation

Fine-tuned mesoporous covalent organic frameworks for highly efficient low molecular-weight proteins separation

In Situ Passivation and Thiol-Mediated Anchoring of Perovskite Quantum Dots in Mesoporous Covalent-Organic Frameworks

In Situ Passivation and Thiol-Mediated Anchoring of Perovskite Quantum Dots in Mesoporous Covalent-Organic Frameworks

Three-dimensional microporous and mesoporous covalent organic frameworks based on cubic building units

Covalent organic frameworks (COFs) have attracted extensive interest due to their unique structures and various applications. However, structural diversities are still limited, which greatly restricts the development of COF materials. Herein, we report two unusual cubic (8-connected) building units and their derived 3D imine-linked COFs with bcu nets, JUC-588 and JUC-589. Owing to these unique building blocks with different sizes, the obtained COFs can be tuned to be microporous or mesoporous structures with high surface areas (2728 m2 g−1 for JUC-588 and 2482 m2 g−1 for JUC-589) and promising thermal and chemical stabilities. Furthermore, the high selectivity of CO2/N2 and CO2/CH4, excellent H2 uptakes, and efficient dye adsorption are observed. This research thus provides a general strategy for constructing stable 3D COF architectures with adjustable pores via improving the valency of rigid building blocks.