Covalent Organic Frameworks Composites Research Articles

Pyrene-4,5,9,10-tetraone-based covalent organic framework/carbon nanotube composite as sodium-ion cathodes with high-rate capability

Covalent organic frameworks (COFs) have attracted significant interest in the field of rechargeable batteries on account of their unique properties, including robust frameworks, well-defined porosity, abundant redox-active sites, and flexible structure designability. However, the limited active site utilization and low electrical conductivity always bring about poor electrochemical performance, thereby hindering practical applications. Herein, we reported a pyrene-4,5,9,10-tetraone-based covalent organic framework composite (Tp-PTO-COF@CNTs) grown on multi-walled carbon nanotubes via in-situ polycondensation. The Tp-PTO-COF@CNTs with numerous active sites (C=O groups) and strong π-π interaction between CNTs and COFs could accommodate more Na-ions and boost structural stability. Moreover, the existence of 1D CNTs could improve electronic conductivity, which facilitates fast transport of electrons and enhances reaction kinetics. In view of the two synergistic effects, Tp- PTO-COF@CNTs cathode displays an outstanding sodium-ion storage property with high initial capacity of 223.2 mA h/g at 0.1 A/g, remarkable rate capability at as high as 20 A/g, and ultra-long cycling stability (163.0 mA h/g exceeding 5000 cycles at 5 A/g). Furthermore, the ex-situ measurements are proposed to better confirm the role of carbonyl groups as redox-active centers. Such ultra-stable structural advantage might inspire the development of COF cathode materials for sodium-ion batteries.

Vinyl-bearing sp2 carbon-conjugated covalent organic framework composites for enhanced electrochemical performance in hydrogen evolution reaction and lithium–sulfur batteries

Vinyl-bearing triazine-functionalized covalent organic frameworks (COFs) have emerged as promising materials for electrocatalysis and energy storage. Guided by density functional theory calculations, a vinyl-enriched COF (VCOF-1) featuring a donor–acceptor structure was synthesized based on the Knoevenagel reaction. Moreover, the VCOF-1@Ru without pyrolysis was obtained through chemical coordination interactions between VCOF-1 and RuCl3, exhibiting enhanced electrocatalytic performance in the hydrogen evolution reaction when exposed to 0.5 M H2SO4. The results demonstrated that the protonation of VCOF-1@Ru enhanced the electrical conductivity and accelerated the generation of H2 on the catalytically active site Ru. Additionally, VCOF-1@CNT with a tubular structure was prepared by uniformly wrapping VCOF-1 onto carbon nanotubes (CNTs) and using it as a cathode for lithium–sulfur batteries by chemically and physically encapsulating S. The enhanced performance of VCOF-1@CNT was attributed to the effective suppression of lithium polysulfide migration. This suppression was achieved through several mechanisms, including the inverse vulcanization of vinyl on VCOF-1@CNT, the enhancement of material conductivity, and the interaction between N in the materials and Li ions. This study demonstrated a strategy for enhancing material performance by precisely modulating the COF structure at the molecular level.

Preparation of Ni Nanowires Covalent Organic Framework Composites with High Electrochemical Stability and Supercapacitor Performance

Preparation of Ni Nanowires Covalent Organic Framework Composites with High Electrochemical Stability and Supercapacitor Performance

Magnetic covalent organic frameworks combined with HPLC for determination of alkylphenols

Alkylphenols are widely applied in the field of industry and agriculture, but their endocrine disrupting properties harm to human health. Moreover, alkylphenols often exhibit the low content in complex samples. Thus, we proposed magnetic covalent organic framework composites (Fe3O4@TatTpa) for efficient magnetic solid phase extraction (MSPE) of alkylphenols via hydrogen bonding, π-π and hydrophobic interactions. In combination with HPLC detection, good linearity (0.006–10 µg mL−1) with R2 (≥0.997) and low limit of detections (1.8–6 × 10−3 µg mL−1) were realized for alkylphenols. The proposed method was successfully employed to determine alkylphenols in soft drink, black oolong tea, and watermelon samples with satisfactory recoveries (86.1–118.5 %) and relative standard deviations (6.3–14.8 %).

Covalent Organic Framework Composites for Catalysis: Opportunities and Challenges

Covalent Organic Frameworks (COFs) on behalf of a novel category of porous substances that show interesting and promising properties in many applications due to their large surface areas, unique physicochemical properties, adjustable porosity, and flexible chemistry. The increasing demand for energy and the harm it does to the environment make the quest for a renewable clean energy source vital. Recently, photocatalysis—which converts solar energy to fuels like hydrogen and hydrocarbons or to degrade environmental contaminants—has emerged as a potential strategy for achieving this goal. In this work, synthesis, structure, and a list of design concepts and topologies are used to examine the opportunities and challenges for enhanced energy technologies employing COF-based materials. It is anticipated to drive the development of existing energy structures, inspire researchers from other fields, and increase the use of covalent organic structures in certain fields.

Crystalline porous materials for catalytic conversion of lignin‐related substances

AbstractThe conversion of the biomass into eco‐friendly fuels and chemicals has been extensively recognized as the essential pathway to achieve the sustainable economy and carbon neutral society. Lignin, as a kind of promising biomass energy, has been certified to produce the high‐valued chemicals and fuels. Numerous efforts have been made to develop various catalysts for lignin catalytic conversion. Both metal‐organic frameworks (MOFs) and covalent organic frameworks (COFs) belong to very important heterogeneous porous catalysts due to their regular porous structures, high specific surface area, and precisely tailored diversities. In the review, the first part focused on the catalytic conversion of lignin, lignin model compounds, and lignin derivatives using the pristine MOFs, functional MOF composites, and MOF‐derived materials. The second part summarized the catalytic conversion of lignin model compounds using pristine COFs and functional COF composites. The review here mainly concentrated on the design of the materials, screening of catalytic conditions, and explorations of the corresponded mechanisms. Specifically, (1) we summarized the MOF‐ and COF‐based materials for the effects on the catalytic transformation of lignin‐related substances; (2) we emphasized the catalytic mechanism of C–C and C–O bonds cleavage together with the structure–activity relationships; (3) we in‐depth realized the relationship between the chemical/electronic/structural properties of the MOF‐ and COF‐based catalysts and their catalytic performance for lignin‐related substances. Finally, the challenges and future perspectives were also discussed on the catalytic conversion of lignin‐related substances by MOF‐ and COF‐based catalysts.

Covalent organic frameworks and their composites for rechargeable batteries.

Covalent organic frameworks (COFs), characterized by well-ordered pores, large specific surface area, good stability, high precision, and flexible design, are a promising material for batteries and have received extensive attention from researchers in recent years. Compared with inorganic materials, COFs can construct elastic frameworks with better structural stability, and their chemical compositions and structures can be precisely adjusted and functionalized at the molecular level, providing an open pathway for the convenient transfer of ions. In this review, the energy storage mechanism and unique superiority of COFs and COF composites as electrodes, separators and electrolytes for rechargeable batteries are discussed in detail. Special emphasis is placed on the relationship between the establishment of COF structures and their electrochemical performance in different batteries. Finally, this review summarizes the challenges and prospects of COFs and COF composites in battery equipment.

An electrochemiluminescence sensor based on CsPbBr3 -zquantum dots and poly (3-thiophene acetic acid) cross-linked nanogold imprinted layer for the determination of benzo(a)pyrene in edible oils.

A novel quench molecularly imprinted electrochemiluminescence sensor (MIECLS) based on a covalent organic framework composite (COF-300-Au) with enhanced electrochemiluminescence (ECL) signal from CsPbBr3 quantum dots and cross-linked 3-thiopheneacetic acid functionalized AuNPs (3-TAA@AuNPs) was developed for the detection of the environmental pollutant benzo(a)pyrene (BaP). A composite material constructed of COF-300-Au with a large specific surface area served as the sensor's support substrate, providing more CsPbBr3 and imprint recognition sites. Electropolymerization was then employed to form an AuNPs three-dimensional imprinting layer with polythiophene cross-linked using BaP as a template and 3-TAA@AuNPs as a functional monomer. A specific cross-linked imprinting recognition effect was recorded on BaP along with the quenching effect of quinones. The density functional theory (DFT) evaluation of the binding mechanism between 3-TAA@AuNPs and BaP revealed powerful MIECLS toward the detection of BaP at concentrations ranging from 10-14 to 10-5M, with a detection limit of as low as 4.1×10-15 M.

Recent progress in advanced covalent organic framework composites for environmental remediation

Recent progress in advanced covalent organic framework composites for environmental remediation

Synthesis of magnetic covalent organic framework composites for effective extraction of benzimidazole fungicides from food samples

Benzimidazoles (BZDs) are widely applied and easily accumulated through the food chain and endanger human health. Effective sample pre-treatment technology is the key procedure for trace BZDs analysis. Herein, magnetic covalent organic frameworks (Fe3O4@TRITER) nanospheres, as magnetic solid-phase extraction (MSPE) adsorbent, were synthesized and well characterized. The efficient extraction of BZDs residues depended on large specific surface of COFs and π-π and hydrophobic interactions between TRITER shell and BZDs. Under the optimal MSPE conditions, the developed MSPE-HPLC based on Fe3O4@TRITER method for BZDs residues afforded good linearities (0.01–1 μg mL−1) with R2 (≥0.996) and low limit of detections (3 ng mL−1). The developed Fe3O4@TRITER based MSPE-HPLC method was evaluated and successfully applied to determine BZDs residues in orange juice, mixed juice drink and cucumber with satisfactory recoveries (76.9–117 %) and relative standard deviations (0.10–7.90 %).

Silica-based covalent organic framework composite for efficient separation and enrichment of palladium and its heterogeneous catalysis application

Considering the necessity and challenge in palladium recovery from high-level liquid waste and hydrogen energy development, the first attempt was made to adsorb Pd(II) from simulated high-level liquid waste firstly, then to achieve in situ reduction by a simple method and followed by using it directly for efficient hydrogen production through the catalytic decomposition of formic acid. In this work, a composite of covalent organic framework and SiO2 (Tp-Azo-COF/SiO2) was prepared by wet impregnation method using SiO2 as a carrier. The characteristics of the composite were examined by SEM, EDS, BET, TG, XRD, etc. The results showed that Tp-Azo-COF/SiO2 exhibited regular silicon-based spherical shapes in microscopic form and good heat resistance. In batch experiments, Tp-Azo-COF/SiO2 was demonstrated excellent adsorption and selectivity for Pd(II) at a wide range of HNO3 acidity (1–5 M), and the separation factor was as high as 2653 at 3 M HNO3. Tp-Azo-COF/SiO2 was able to reach a maximum adsorption capacity of 85.40 mg/g at 120 min at 298 K in 3 M HNO3. FT-IR and XPS analysis show that the adsorption mechanism of Pd(II) by the composite occurs mainly on the C-NH of Tp-Azo-COF, and NO3– is also involved in the coordination. In dynamic column experiments, Tp-Azo-COF/SiO2 was demonstrated a nearly complete separation and recovery of Pd(II) with good reusability, and the enrichment coefficients all maintained at about 30. Finally, an efficient and environmentally friendly process was proposed to achieve the in situ reduction of Pd(II)-loaded Tp-Azo-COF/SiO2. Pd-loaded Tp-Azo-COF/SiO2 was demonstrated better decomposition performance than commercial Pd-based catalysts hydrogen production by the catalytic decomposition formic acid.

Porphyrin-based covalent organic framework with self-accelerated M−N4 bimetallic active sites for enhanced electrochemical detection of trace hydrogen peroxide

The ultrasensitive detection of trace hydrogen peroxide (H2O2) has been a fascinating research topic owing to its significant application in environmental monitoring, food safety, and scientific research. In this study, bimetallic porphyrin-based covalent organic framework composites (MWCNTs@Mn/Fe-COF) was prepared by in situ polymerization of Mn porphyrin (MnPor) and Fe porphyrin (FePor) on multi-walled carbon nanotubes (MWCNTs), and a biomimetic enzyme electrochemical sensor was constructed for determination of trace H2O2. The unique topological structure features of COF and the high conductivity of MWCNTs not only ensured highly independent M−N4 electrochemical active sites, but also guaranteed efficient electron transfer pathways. Especially, the introduction of Mn sites formed a self-accelerated redox cycling between valence states, which significantly improved the electrocatalytic efficiency. Taking advantage of the above advantages, the MWCNTs@Mn/Fe-COF based sensor achieved ultrasensitive detection of H2O2 with a low detection limit of 2 nM. Moreover, the developed sensor has been successfully used to measure trace H2O2 induced by lab-equipped ultrasonic cleaners and in disinfector and apple juice. The constructed sensor in this study has potential application value in the rapid detection of trace H2O2 in real samples, which opened up a new way for the synthesis of bimetallic analog enzymes and the construction of ultra-sensitive electrochemical sensors.

Adsorption Performance of Magnetic Covalent Organic Framework Composites for Bisphenol A and Ibuprofen.

As typical environmental endocrine disruptors and nonsteroidal anti-inflammatory drugs, bisphenol A and ibuprofen in water supplies can cause great harm to the ecological environment and human health. In this study, magnetic covalent organic framework composites Fe3O4@COF-300 were synthesized by the hydrothermal method and used to remove bisphenol A and ibuprofen from water. Fe3O4@COF-300 could be rapidly separated from the matrix by external magnetic fields, and could selectively adsorb bisphenol A and ibuprofen in the presence of coexisting compounds such as phenol, Congo red, and amino black 10B. The removal efficiency of ibuprofen was 96.12-98.52% at pH in the range of 2-4 and that of bisphenol A was 92.18-95.62% at pH in the range of 2-10. The adsorption of bisphenol A and ibuprofen followed a pseudo-second-order kinetic and Langmuir model, and was a spontaneous endothermic process with the maximum adsorption amounts of 173.31 and 303.03 mg∙g-1, respectively. The material presented favorable stability and reusability, and the removal efficiency of bisphenol A and ibuprofen after 5 cycles was still over 92.15% and 89.29%, respectively. Therefore, the prepared composite Fe3O4@COF-300 exhibited good performance in the adsorption of bisphenol A and ibuprofen in water.

Proton Conduction Properties of Intrinsically Sulfonated Covalent Organic Framework Composites

The long–term stability of proton conductors is one of the most important factors in evaluating materials. Guest molecules can act as “bridges” for proton conduction channels and reside in the channels of covalent organic frameworks, but they are prone to leakage. Therefore, it is important to develop proton conductors with intrinsic proton conductivity. In this paper, we synthesized an intrinsically sulfonated covalent organic framework, TpPa–SO3H, which has a more stable proton conducting performance than that of TpPa@H2SO4 by loading guest molecules. Meanwhile, the proton conductivity of TpPa–SO3H was further improved by coating a superabsorbent polymer through an in situ reaction to obtain PANa@TpPa–SO3H (PANa: sodium polyacrylate). As a result, the modified composite exhibits an ultrahigh proton conductivity of 2.33 × 10−1 S cm−1 at 80 °C under 95% relative humidity (RH). The stability of PANa@TpPa–SO3H makes it an efficient proton transport platform with excellent proton conductivity and long–term durability.

Facile fabrication of hydrophilic covalent organic framework composites for highly selective enrichment of N-glycopeptides

The development of facilely synthetic materials acts an essential role in glycoproteome analysis, especially for the highly efficient enrichment of N-linked glycopeptides. In this work, a facile and timesaving route was introduced in which COFTP-TAPT served as a carrier and poly (ethylenimine) (PEI) and carrageenan (Carr) were successively coated on the surface via electrostatic interaction. The resultant COFTP-TAPT@PEI@Carr showed remarkable performance in glycopeptide enrichment with high sensitivity (2 fmol μL−1), high selectivity (1:800, molar ratio of human serum IgG to BSA digests), large loading capacity (300 mg g−1), satisfactory recovery (102.4 ± 6.0%) and reusability (at least eight times). Due to the brilliant hydrophilicity and electrostatic interactions between COFTP-TAPT@PEI@Carr and positively charged glycopeptides, the prepared materials could be applied in the identification and analysis in the human plasma of healthy subjects and patients with nasopharyngeal carcinoma. As a result, 113 N-glycopeptides with 141 glycosylation sites corresponding to 59 proteins and 144 N-glycopeptides with 177 glycosylation sites corresponding to 67 proteins were enriched from 2 μL plasma trypsin digests of the control groups and patients with nasopharyngeal carcinoma, respectively. 22 glycopeptides were identified only from the normal controls and 53 glycopeptides were detected only from the other set. The results demonstrated that this hydrophilic material was promising on a large scale and further N-glycoproteome research.

Construction of MOF@COF composite-based electrochemical aptasensor for detection of Staphylococcus aureus.

In this work, a biological metal-organic framework@conductive covalent organic framework composite (bio-MOF@con-COF, denoted as Zn-Glu@PTBD-COF, here, Glu indicates L-glutamic acid, PT indicates 1,10-phenanthroline-2,9-dicarbaldehyde, and BD indicates benzene-1,4-diamine) was prepared and used as sensing material to fabricate aptasensor for trace detection of Staphylococcus aureus (SA). The Zn-Glu@PTBD-COF integrates the mesoporous structure and abundant defects of the MOF framework, the excellent conductivity of the COF framework, and high stability of the composite, providing abundant active sites to effectively anchor aptamers. As a result, the Zn-Glu@PTBD-COF-based aptasensor shows high sensitivity to detect SA via specific recognition between aptamer and SA, as well as the formation of aptamer-SA complex. Low detection limits of 2.0 and 1.0CFU·mL-1 are deduced from the electrochemical impedance spectroscopy and differential pulse voltammetry within a wide linear range of 10-108CFU·mL-1 for SA, respectively. The Zn-Glu@PTBD-COF-based aptasensor also shows good selectivity, reproducibility, stability, regenerability, and applicability for real milk and honey samples. Therefore, the Zn-Glu@PTBD-COF-based aptasensor will be promising for fast screening of foodborne bacteria in food service industry. Zn-Glu@PTBD-COF composite was prepared and used as sensing material to fabricate aptasensor for trace detection of Staphylococcus aureus (SA). Low detection limits of 2.0 and 1.0CFU·mL-1 are deduced from the electrochemical impedance spectroscopy and differential pulse voltammetry within a wide linear range of 10-108CFU·mL-1 for SA, respectively. The Zn-Glu@PTBD-COF-based aptasensor also shows good selectivity, reproducibility, stability, regenerability, and applicability for real milk and honey samples.

Construction of magnetic COF composites for lead removal with fast dynamics and superior capacity

BackgroundThe removal of heavy metals is very important because of their nonbiodegradability and toxicity to the general population and environment. Adsorption is regarded as a promising approach for target pollutant removal due to its simplicity and economy. MethodsNovel magnetic covalent organic framework (COF) composites (Fe3O4@TpPa-NO2) consisting of a magnetic Fe3O4 core and a TpPa-NO2 COF shell are synthesized and developed as adsorbents for Pb(II) removal from aqueous solution. Significant findingsThe obtained composites exhibit superior adsorption performance (909.1 mg/g) and fast adsorption dynamics (adsorption equilibration time of less than 10 min) toward Pb(II). The experimental data for the adsorption of Pb(II) follow pseudo-second-order kinetic and Langmuir isotherm models. The superior performance of Fe3O4@TpPa-NO2 for Pb(II) elimination is attributed to electrostatic and coordination interactions between the metal ion and functional groups (nitrogen and oxygen) of magnetic COF composites. The Pb(II)-loaded Fe3O4@TpPa-NO2 can be easily regenerated by acid treatment. Furthermore, Fe3O4@TpPa-NO2 demonstrates excellent reusability and maintains a high removal efficiency throughout five consecutive adsorption-desorption processes. Various COF-based magnetic adsorbents can be fabricated for specific pollutants due to the diversity in the structure and pore size of the COFs, which present attractive prospects for high-efficiency removal of contaminants in water treatment.

One-step synthesis of magnetic covalent organic framework composite for the adsorption of marine toxin okadaic acid

One-step synthesis of a crystalline magnetic covalent organic framework composite is reported using a sub-stoichiometric amount of the diamino building block. The composite showed high efficiency for the removal of okadaic acid toxin from seawater.

Integrated carbon nanotube and triazine-based covalent organic framework composites for high capacitance performance.

As a rising class of crystallographic organic polymers, covalent-organic frameworks (COFs) have high specific surface areas, ordered pore structures, and designability, which exhibit broad application prospects in the energy storage sector. However, their low electrical conductivity hinders their potential use in supercapacitors. To improve the electrical conductivity, we introduced carboxylated multi-walled carbon nanotubes to obtain a series of carbon nanotube@COF composites by a facile one-pot method, in which 2D TFA-COFs are in situ grown on the surface of carboxylated multi-walled carbon nanotubes. Among them, the CNT@TFA-COF-3 composite exhibits good crystallinity, regular pores, excellent stability and a specific surface area of 1034 m2 g-1. As expected, as a capacitive electrode material, the CNT@TFA-COF composite shows improved electrochemical performance. Notably, the value of specific capacitance of the CNT@TFA-COF-3 composite (338 F g-1) is about 8.5, 4.9, and 7.5 times higher than those of TFA-COFs, CNTs, and the CNT/TFA-COF physically mixed complex at a current density of 1.0 A g-1, respectively. Furthermore, the CNT@TFA-COF-3 supercapacitor exhibits long-term cycle chemical stability and splendid rate capability even after 7000 charge-discharge cycles. The successful preparation of the CNT@TFA-COF-3 composite can provide new ideas for the construction of new COF-based composites and the development of new materials for energy storage.

An agaric-like covalent organic framework composite for efficient extraction of trace cytokinins in plant samples

Covalent organic framework composites have received great interest and regarded as new-generation porous materials in application of sample preparation. In this work, an agaric-like graphene oxide @ covalent organic framework (AGO@COF) composite was first synthesized and used as an ideal adsorbent for enrichment of trace cytokinins (CKs) due to its large specific surface area, rich in micro-mesopore and organic functional groups. The contact areas between AGO@COF composite and CKs were greatly increased due to the special agaric-like morphology, which would further improve the extraction efficiency. Hence, a rapid, simple and efficient AGO@COF-based dispersive solid-phase extraction method for detecting four CKs (N6-(delta 2-isopentenyl)-adenine, kinetin, DL-dihydrozeatin and 6-benzylaminopurine) was successfully established. The proposed method had low limits of detection (0.1−2.0 pg mL−1), good reproducibility (RSDs≤3.9%, n=5) and high recoveries (84.4−107.7%). With this method, N6-(delta 2-isopentenyl)-adenine and 6-benzylaminopurine in plants were successfully detected and quantified. Results showed that the developed AGO@COF composite possessed superior extraction performance and potential application in enrichment of trace targets from complex plant samples.