Sulfhydryl functionalized covalent organic framework as an efficient adsorbent for selective Pb (II) removal

Covalent organic frameworks derived Single-Atom cobalt catalysts for boosting oxygen reduction reaction in rechargeable Zn-Air batteries

The design and development of high-performance and long-life Pt-free catalysts for the oxygen reduction reaction (ORR) is of great important with respect to metal-air batteries and fuel cells. Herein, a new low-cost covalent organic frameworks (COFs)-derived CoNC single-atoms catalyst (SAC) is fabricated and compared with the engineered nanoparticle (NP) counterpart for ORR activity. The ORR performance of the SAC catalyst (CoSA@NC) surpasses the NP counterpart (CoNP-NC) under the same operation condition. CoSA@NC also achieves improved long-term durability and better methanol tolerance compared with the Pt/C. The zinc-air battery assembled by the CoSA@NC cathode delivers a higher power density and energy density than that of commercial Pt/C catalyst. Molecular dynamics (MD) is performed to explain the spontaneous evolution from clusters to single-atom metal configuration and density functional theory (DFT) calculations find that CoSA@NC possesses lower d-band center, resulting in weaker interaction between the surface and the O-containing intermediates. Consequently, the reductive desorption of OH*, the rate-determine step, is further accelerated.

Selective lead capture using amide-containing COFs: A novel strategy for efficient soil remediation

A critical consideration in the application of phytoremediation to remediate sludge soil contaminated with heavy metals is the potential for leaching risks that prevail prior to the efficient uptake of these metals by plants. The most cost-effective method is to use heavy metal stabilizers with selective adsorption. A novel amide-based COF material (COF-TH) has been synthesized as a heavy metal stabilizer for Pb. COF-TH exhibits significant selectivity for Pb in five-metal-mixed solutions, with a distribution coefficient KD as high as 3279 mL·g-1, which was more than 7.3 times that of other heavy metals. The maximum adsorption capacity of COF-TH for Pb was 189 mg·g-1. The adsorption fitted Langmuir model and intra-particle diffusion model, and satisfied pseudo-second-order kinetic model. The excellent selectivity and adsorption performance originate from the complexation between abundant amide groups and Pb ions. Pot experiments and leaching assays confirm that COF-TH decreased Pb leachate concentrations by 77.8 % without significantly decreasing total phytoextracted amounts of other heavy metals, due to the high selectivity of COF-TH to Pb. Additionally, its positive impact on plant growth and microbial diversity makes it a promising soil remediation agent. This investigation offers a novel approach to mitigate the leaching risk of a specific heavy metal Pb during sludge land application by integrating soil phytoremediation with stabilization techniques.

Bottom-up synthesis of a sulfhydryl-modified heteroporous covalent organic framework for ultrafast removal of trace Hg(Ⅱ) from water

The development of functionalized covalent organic frameworks (COFs) is crucial in expanding their potential for removing toxic heavy metals from drinking water. Here, a new sulfhydryl-modified heteroporous COF (COFDBD-BTA) was prepared using a "bottom-up" approach in which a direct amine-aldehyde dehydration condensation between 2,5-diamino-1,4-benzenedithiol dihydrochloride (DBD) and [1,1'-biphenyl]-3,3',5,5'-tetracarbaldehyde (BTA) was occurred. The COFDBD-BTA featured a hexagonal kagome (kgm) structure and a sheet-like morphology. Notably, COFDBD-BTA contained densely S atoms that provided high-density Hg(II) adsorption sites for efficient and selective trace Hg(II) removal. COFDBD-BTA exhibited excellent performance in rapidly removing trace Hg(II) from 30 μg L-1 to 0.71 μg L-1 within 10 s, below the World Health Organization's allowable limit of 1 μg L-1. Additionally, COFDBD-BTA exhibited a high Hg (Ⅱ) removal level from water, achieving adsorption capacity of 687.38 mg g-1. Furthermore, the adsorbent exhibited a wide range of applicability for low concentration (6-500 μg L-1) Hg (Ⅱ), a simple and feasible regeneration method, and strong Hg(II) removal ability in real tap water systems. The excellent adsorption efficiency, outstanding recyclability, and one-step room temperature synthesis make S-rich COFDBD-BTA a promising candidate for eliminating Hg (Ⅱ) from drinking water.

Synthesis of ultrathin hybrid membranes via the co-polymerization of acrylic acid, styrene and molybdenum disulfide and their high adsorption selectivity for lead(II) in the mixture of metal ions

Lead(II) is a potential carcinogen of heavy-metal ions (HIs). With the wide application of Pb-bearing products including lead alloy products, and new-energy lead-ion batteries, lead pollution has become a tricky problem. To solve such a difficulty, novel ultrathin MoS2-vinyl hybrid membranes (MVHMs) with a "spring" effect were synthesized via co-polymerization of acrylic acid, styrene and molybdenum disulfide (MoS2) and their adsorptions for HIs were explored. The "spring" effect derived from the interaction between the tendency of the short polyacrylic acid (PAA) chain connected with MoS2 to spread outward and the coulomb force between layers from MoS2 (s-MoS2), which enlarge the spacing of MoS2 layers without changing the number of layers after membrane formation, which changes the swelling membrane to a dense membrane and reduces the original thickness from 0.5 cm to 0.011 mm in the thickness direction. The adsorption experiment revealed that these MVHMs had super adsorption performance and high selectivity for Pb2+ by comparison with other five metal ions: Cu2+, Cd2+, Ni2+, Cr3+ and Zn2+. Especially, the adsorption quantity of MVHMs for Pb2+ could approach 2468 mg/g and the maximum adsorption ratio of qe[Pb2+]/qe[Cu2+] can reach 10.909. These values were much larger than the data obtained with the adsorbents reported in the last decade. A variety of models are applied to evaluate the effect of ionic groups. It was confirmed that -COOH plays a key role in adsorption of HIs and s-MoS2 also has a certain contribution. Conversely, ion exchange plays only a minor role during the period of adsorption process. Effective diffusion coefficient (Deff) of Pb(II) had the largest values among these metal ions. Hence, these hybrid membranes are promising adsorbents for the removal of Pb2+ from water containing various ions.

Chemoselectivity Strategy Based on B-Label Integrated with Tailored COF for Targeted Metabolomic Analysis of Short-Chain Fatty Acids by UHPLC-MS/MS

Chemoselective extraction strategy is an emerging and powerful means for targeted metabolomics analysis, which allows for the selective identification of biomarkers. Short-chain fatty acids (SCFAs) as functional metabolites for many diseases pose challenges in qualitative and quantitative analyses due to their high polarity and uneven abundance. In our study, we proposed the B-labeled method for the derivatization of SCFAs using easily available 3-aminobenzeneboronic acid as the derivatization reagent, which enables the introduction of recognition unit (boric acid groups). To analyze the B-labeled targeted metabolites accurately, cis-diol-based covalent organic framework (COF) was designed to specifically capture and release target compounds by pH-response borate affinity principle. The COF synthesized by the one-step Schiff base reaction possessed a large surface area (215.77 m2/g), excellent adsorption capacity (774.9 μmol/g), good selectivity, and strong regeneration ability (20 times). Combined with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analysis, our results indicated that the detection sensitivities of SCFAs increased by 1.2-2500 folds compared with unlabeled method, and the retention time and isomer separation were improved. Using this strategy, we determined twenty-six SCFAs in the serum and urine of rats in four groups about osteoporosis and identified important biomarkers related to the tricarboxylic acid cycle and fatty acid metabolism pathways. In summary, UHPLC-MS/MS based on B-labeled derivatization with tailored COF strategy shows its high selectivity, excellent sensitivity, and good chromatographic behavior and has remarkable application prospect in targeted metabolomics study of biospecimens.

Thiol-Ene Click Reaction Modified Triazinyl-Based Covalent Organic Framework for Pb(II) Ion Effective Removal

As a common water pollutant, Pb2+ has harmful effects on the nervous, hematopoietic, digestive, renal, cardiovascular, and endocrine systems. Due to the drawbacks of traditional adsorbents such as structural disorder, poor stability, and difficulty in introducing adsorption active sites, the adsorption capacity is low, and it is difficult to accurately study the adsorption mechanism. Herein, vinyl-functionalized covalent organic frameworks (COFs) were synthesized at room temperature, and sulfur-containing active groups were introduced by the click reaction. By precisely tuning the chemical structure of the sulfur-containing reactive groups through the click reaction, we found that the adsorption activity of the sulfhydryl group was higher than that of the sulfur atom in the thioether. Moreover, the incorporation of flexible linking groups was observed to enhance the adsorption activity at the active site. The maximum adsorption capacity of the postmodified COF TAVA-S-Et-SH for Pb(II) reached 303.0 mg/g, which is 2.9 times higher than that of the unmodified COF. This work not only demonstrates the remarkable potential of the "thiol-ene" click reaction for the customization of active adsorption sites but also demonstrates the remarkable potential of the "thiol-alkene" click reaction to explore the structure-effect relationship between the active adsorption sites and the metal ion adsorption capacity.

Three-Dimensional Printing of Cellulose/Covalent Organic Frameworks (CelloCOFs) for CO2 Adsorption and Water Treatment

The development of porous organic polymers, specifically covalent organic frameworks (COFs), has facilitated the advancement of numerous applications. Nevertheless, the limited availability of COFs solely in powder form imposes constraints on their potential applications. Furthermore, it is worth noting that COFs tend to undergo aggregation, leading to a decrease in the number of active sites available within the material. This work presents a comprehensive methodology for the transformation of a COF into three-dimensional (3D) scaffolds using the technique of 3D printing. As part of the 3D printing process, a composite material called CelloCOF was created by combining cellulose nanofibrils (CNF), sodium alginate, and COF materials (i.e., COF-1 and COF-2). The intervention successfully mitigated the agglomeration of the COF nanoparticles, resulting in the creation of abundant active sites that can be effectively utilized for adsorption purposes. The method of 3D printing can be described as a simple and basic procedure that can be adapted to accommodate hierarchical porous materials with distinct micro- and macropore regimes. This technology demonstrates versatility in its use across a range of COF materials. The adsorption capacities of 3D CelloCOF materials were evaluated for three different adsorbates: carbon dioxide (CO2), heavy metal ions, and perfluorooctanesulfonic acid (PFOS). The results showed that the materials exhibited adsorption capabilities of 19.9, 7.4-34, and 118.5-410.8 mg/g for CO2, PFOS, and heavy metals, respectively. The adsorption properties of the material were found to be outstanding, exhibiting a high degree of recyclability and exceptional selectivity. Based on our research findings, it is conceivable that the utilization of custom-designed composites based on COFs could present new opportunities in the realm of water and air purification.

Effective remediation of Pb2+ polluted environment by adsorption onto recyclable hydroxyl bearing covalent organic framework

The removal of heavy metal ions from wastewater has attracted considerable interest because of their toxicity. Adsorption is one of the most promising methods for the removal of heavy metal ions due to its simplicity and effectiveness. Recently, covalent organic frameworks (COFs) have become promising adsorbents for effective wastewater remediation. However, many building blocks have been developed, and the design of COFs with high adsorption efficiency remains a challenge. Here, a covalent organic framework (DHTP-TPB COF) decorated with hydroxyl groups was developed for the efficient removal of Pb²⁺ ions. The DHTP-TPB COF showed excellent performance in adsorbing Pb²⁺ from aqueous solution. More importantly, DHTP-TPB COF exhibited high selectivity for Pb²⁺ compared to other competing ions, capturing Pb²⁺ ions with a removal efficiency of over 96% at pH 4. The results show that the DHTP-TPB COF exhibits excellent adsorption capacity at pH 4 of up to 154.3 mg/g for Pb²⁺ ions; the value is comparable to many previously reported COFs. Moreover, the adsorbed Pb²⁺ ions could be easily eluted with a 0.1 M EDTA solution, and the DHTP-TPB COF can be reused for more than five adsorption-desorption cycles without significant loss of adsorption capacity. Moreover, the adsorption mechanism was revealed using XPS analysis, indicating the formation of strong coordination-bonding interactions between hydroxyl and Pb²⁺ ions. Therefore, the DHTP-TPB COF prepared herein has high potential for the treatment of Pb²⁺-contaminated wastewater and is promising for the adsorption of Pb²⁺ ions in practical applications.

Efficient adsorption and degradation of dyes from water using magnetic covalent organic frameworks with a pyridinic structure

Covalent organic frameworks (COFs) have promising applications in environmental remediation owing to their precise directional synthesis and superior adsorption ability. However, magnetic COFs with pyridinic N have not been studied as bifunctional materials for the adsorption and catalytic degradation of dyes. Therefore, in this study, a magnetic COF with a pyridinic structure (BiPy-MCOF) was successfully synthesized using a solvothermal method, which exhibited higher methyl orange (MO) removal than other common adsorbents. The best degradation efficiency via the Fenton-like reaction was obtained by pre-adsorbing MO for 3 h at pH 3.1. Both adsorption and catalytic degradation resulted in better removal of MO under acidic conditions. The introduction of pyridinic N improved MO adsorption and degradation on BiPy-MCOF. The electrostatic potential (ESP) showed that pyridinic N had a strong affinity for MO adsorption. Density functional theory calculations confirmed the potential sites on MO molecules that may be attacked by free radicals. Possible degradation pathways were proposed based on the experimental results. Moreover, BiPy-MCOF could effectively degrade MO at least four times, and a high degradation efficiency was obtained in other dyes applications. The coupling of adsorption and degradation demonstrated that the as-prepared BiPy-MCOF was an effective material for organic dyes removal from water.

Advanced Covalent Organic Framework-Based Membranes for Recovery of Ionic Resources

Membrane technology has shown a viable potential in conversion of liquid-waste or high-salt streams to fresh waters and resources. However, the non-adjustability pore size of traditional membranes limits the application of ion capture due to their low selectivity for target ions. Recently, covalent organic frameworks (COFs) have become a promising candidate for construction of advanced ion separation membranes for ion resource recovery due to their low density, large surface area, tunable channel structure, and tailored functionality. This tutorial review aims to analyze and summarize the progress in understanding ion capture mechanisms, preparation processes, and applications of COF-based membranes. First, the design principles for target ion selectivity are illustrated in terms of theoretical simulation of ions transport in COFs, and key properties for ion selectivity of COFs and COF-based membranes. Next, the fabrication methods of diverse COF-based membranes are classified into pure COF membranes, COF continuous membranes, and COF mixed matrix membranes. Finally, current applications of COF-based membranes are highlighted: desalination, extraction, removal of toxic metal ions, radionuclides and lithium, and acid recovery. This review presents promising approaches for design, preparation, and application of COF-based membranes in ion selectivity for recovery of ionic resources.

Covalent organic frameworks as promising adsorbent paradigm for environmental pollutants from aqueous matrices: Perspective and challenges

Covalent organic frameworks (COFs) are an emerging class of new porous crystalline polymers materials having robust framework, outstanding structural regularity, highly ordered aperture size, inherent porosity, and chemical stability with designer properties, making them an ideal material for adsorbing a variety of contaminants from water bodies. Presented study focusses on the current advances and progress of pristine COFs as well as COFs based composites as an emerging substitute for the adsorption and removal of a variety of pollutants including water desalination technique, heavy metals, pharmaceuticals, dyes and organic pollutants. The absorption capabilities of COFs-derived architecture are evaluated and equated with those of other commonly used adsorbents. The interaction between sorption ability and structural property as well as some regularly utilized ways to improve the adsorption performance of COFs-based materials are also reviewed. Finally, perspective and a summary about the challenges and opportunities of COFs and COFs-derived materials are discussed to deliver some exciting data for fabricating and designing of COFs and COFs-derived materials for remediation of environmental pollutants.

Adsorption and Removal of Mercury(II) by a Crosslinked Hyperbranched Polymer Modified via Sulfhydryl

In this study, the highly crosslinked hyperbranched polyamide-amines (H-PAMAMs) were first prepared via one-pot methods and then modified with thiourea to synthesize a novel adsorbent containing sulfhydryl groups (CHAP-SH), which was used to adsorb Hg(II) ions from aqueous solutions. The adsorption characteristics and mechanism of CHAP-SH for Hg(II) ions were systematically studied. As expected, CHAP-SH exhibited a rapid removal performance toward Hg(II), and the maximum adsorption capacity was 282.74 mg/g at 318 K and pH = 4.5. The whole adsorption behavior could be well described by the pseudo-second-order kinetic model and Langmuir and Redlich-Peterson adsorption isotherm models, which reflected that the adsorption process was mainly monolayer chemisorption. Meanwhile, CHAP-SH had strong selectivity for Hg(II) in the presence of multimetal ions, and it had excellent recoverability after five cycles. In order to further elucidate the adsorption mechanism, the adsorbents before and after adsorption were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and energy-dispersive X-ray spectroscopy, and the results showed that the nitrogen-containing, oxygen-containing, and sulfur-containing groups in the adsorbent molecule had synergistic complexation with Hg(II). These results indicated that the adsorbents had great potential in the future treatment of aqueous solutions containing Hg(II).

A Perspective on the Application of Covalent Organic Frameworks for Detection and Water Treatment

Global population growth and water resource scarcity are significant social problems currently being studied by many researchers focusing on finding new materials for water treatment. The aim is to obtain quality water suitable for drinking and industrial consumption. In this sense, an emergent class of crystalline porous materials known as Covalent-Organic Frameworks (COFs) offers a wide range of possibilities since their structures can be designed on demand for specific applications. Indeed, in the last decade, many efforts have been made for their use in water treatment. This perspective article aims to overview the state-of-the-art COFs collecting the most recent results in the field for water detection of pollutants and water treatment. After the introduction, where we overview the classical design strategies on COF design and synthesis for obtaining chemically stable COFs, we summarize the different experimental methodologies used for COFs processing in the form of supported and free-standing membranes and colloids. Finally, we describe the use of COFs in processes involving the detection of pollutants in water and wastewater treatment, such as the capture of organic compounds, heavy metals, and dyes, the degradation of organic pollutants, as well as in desalination processes. Finally, we provide a perspective on the field and the potential technological use of these novel materials.

Recent Advances in Covalent Organic Frameworks for Heavy Metal Removal Applications

Covalent organic frameworks comprise a unique class of functional materials that has recently emerged as a versatile tool for energy-related, photocatalytic, environmental, and electrochromic device applications. A plethora of structures can be designed and implemented through a careful selection of ligands and functional units. On the other hand, porous materials for heavy metal absorption are constantly on the forefront of materials science due to the significant health issues that arise from the release of the latter to aquatic environments. In this critical review, we provide insights on the correlation between the structure of functional covalent organic frameworks and their heavy metal absorption. The elements we selected were Pb, Hg, Cr, Cd, and As metal ions, as well as radioactive elements, and we focused on their removal with functional networks. Finally, we outline their advantages and disadvantages compared to other competitive systems such as zeolites and metal organic frameworks (MOFs), we analyze the potential drawbacks for industrial scale applications, and we provide our outlook on the future of this emerging field.

Covalent organic frameworks as robust materials for mitigation of environmental pollutants

Today, one of the main leading global problems is the presence of different pollutants in the environment. These pollutants not only affect human health but also overshadow the life of other creatures. Thus, pollutant treatment has become a challenging issue among the researchers and the scientific community. Different adsorbents and catalysts have been applied to the removal of pollutants. However, the associated limitations like poor chemical and physical stability, low surface area and low binding capacity revived researchers' attention to exploring alternative materials. Covalent organic frameworks (COFs) are versatile materials created based on the strong covalent interactions between blocked monomers. Unique features, including high specific surface area, high chemical-physical stability and crystallinity render COFs an intriguing sorbent and catalyst in treating pollutants. This review spotlights the applications of COFs as distinguished adsorbents to remove hazardous pollutants from the environment. At first, COFs and their properties as alternative materials were introduced. Then, different synthesis approaches of COFs and their advantages and disadvantages were discussed. Furthermore, the applications of COFs outlined to remove a wide variety of pollutants based on adsorption and degradation. Finally, the prospects of COFs for the treatment of pollutants were evaluated.

Covalent Organic Frameworks: Synthesis, Properties and Applications-An Overview

Covalent Organic Frameworks (COFs) are an exciting new class of microporous polymers with unprecedented properties in organic material chemistry. They are generally built from rigid, geometrically defined organic building blocks resulting in robust, covalently bonded crystalline networks that extend in two or three dimensions. By strategically combining monomers with specific structures and properties, synthesized COF materials can be fine-tuned and controlled at the atomic level, with unparalleled precision on intrapore chemical environment; moreover, the unusually high pore accessibility allows for easy post-synthetic pore wall modification after the COF is synthesized. Overall, COFs combine high, permanent porosity and surface area with high thermal and chemical stability, crystallinity and customizability, making them ideal candidates for a myriad of promising new solutions in a vast number of scientific fields, with widely varying applications such as gas adsorption and storage, pollutant removal, degradation and separation, advanced filtration, heterogeneous catalysis, chemical sensing, biomedical applications, energy storage and production and a vast array of optoelectronic solutions. This review attempts to give a brief insight on COF history, the overall strategies and techniques for rational COF synthesis and post-synthetic functionalization, as well as a glance at the exponentially growing field of COF research, summarizing their main properties and introducing the numerous technological and industrial state of the art applications, with noteworthy examples found in the literature.

Orderly Porous Covalent Organic Frameworks-based Materials: Superior Adsorbents for Pollutants Removal from Aqueous Solutions

Covalent organic frameworks (COFs) are a new type of crystalline porous polymers known for chemical stability, excellent structural regularity, robust framework, and inherent porosity, making them promising materials for capturing various types of pollutants from aqueous solutions. This review thoroughly presents the recent progress and advances of COFs and COF-based materials as superior adsorbents for the efficient removal of toxic heavy metal ions, radionuclides, and organic pollutants. Information about the interaction mechanisms between various pollutants and COF-based materials are summarized from the macroscopic and microscopic standpoints, including batch experiments, theoretical calculations, and advanced spectroscopy analysis. The adsorption properties of various COF-based materials are assessed and compared with other widely used adsorbents. Several commonly used strategies to enhance COF-based materials’ adsorption performance and the relationship between structural property and sorption ability are also discussed. Finally, a summary and perspective on the opportunities and challenges of COFs and COF-based materials are proposed to provide some inspiring information on designing and fabricating COFs and COF-based materials for environmental pollution management.

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Covalent organic frameworks (COFs) are a new type of crystalline porous materials known for chemical stability, high specific surface area, and orderly porous channels.With the rapid growth of industrialization, water pollutants remain a serious issue of public health and environmental protection

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COFs as superior adsorbents for the efficient removal of toxic heavy metal ions, radionuclides, and organic pollutants in water is becoming a hot topic

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Information about the interaction mechanisms between various pollutants and COFs materials are summarized.The perspectives and challenges are proposed to provide some useful inspiration for the application of COFs in environmental pollution management

Synthesis methods of microporous organic polymeric adsorbents: a review

MOPs can be synthesized in a large variety of ways, which affect their pores and surface area. Variation in synthesis and porosity has a significant effect on their adsorption properties.

Nanomotor-based adsorbent for blood Lead(II) removal in vitro and in pig models

Blood lead (Pb(II)) removal is very important but challenging. The main difficulty of blood Pb(II) removal currently lies in the fact that blood Pb(II) is mainly complexed with hemoglobin (Hb) inside the red blood cells (RBCs). Traditional blood Pb(II) removers are mostly passive particles that do not have the motion ability, thus the efficiency of the contact between the adsorbent and the Pb(II)-contaminated Hb is relatively low. Herein, a kind of magnetic nanomotor adsorbent with movement ability under alternating magnetic field based on Fe₃O₄ nanoparticle modified with meso-2, 3-dimercaptosuccinic acid (DMSA) was prepared and a blood Pb(II) removal strategy was further proposed. During the removal process, the nanomotor adsorbent can enter the RBCs, then the contact probability between the nanomotor adsorbent and the Pb(II)-contaminated Hb can be increased by the active movement of nanomotor. Through the strong coordination of functional groups in DMSA, the nanomotor adsorbent can adsorb Pb(II), and finally be separated from blood by permanent magnetic field. The in vivo extracorporeal blood circulation experiment verifies the ability of the adsorbent to remove blood Pb(II) in pig models, which may provide innovative ideas for blood heavy metal removal in the future.