High-performance removal of mercury ions (II) and mercury vapor by SO3−-anchored covalent organic framework

Facile green preparation of single- and two-component modified activated carbon fibers for efficient trace heavy metals removal from drinking water

Trace heavy metals exist in drinking water, having great adverse effects on human health and making it a huge challenge to remove. Herein, novel materials have been prepared by a simple and green method using single- (polydopamine (PDA) or 2,3-dimercaptopropanesulfonic sodium (DMPS)) (PDA-OACF or DMPS-OACF) and two-component (PDA and DMPS) (DMPS-PDA-OACF) functionalized activated carbon fibers pretreated by hydrogen peroxide for the removal of trace heavy metals. The as-prepared DMPS-OACF (7.5,20) under DMPS addition of 7.5 mg and sonication time of 20 min retained large specific surface area, micro-mesoporous structure and rich functional groups and showed better adsorption performance for trace lead and mercury. It also exhibited wide applicable ranges of pH (3.50-10.50) and concentration (50-1136 μg L^-1), rapid adsorption kinetics, and excellently selective removal performance for trace lead. The maximum lead adsorption capacity reached 16.03 mg g^-1 when the effluent lead concentration met World Health Organization (WHO) standard and the adsorbent can be regenerated by EDTA solution. The fitting results of adsorption kinetics and isotherm models revealed that the lead adsorption process was multi-site adsorption on heterogeneous surfaces and chemical adsorption. The excellent adsorption properties for trace heavy metals were attributed that the sulfur/oxygen/nitrogen-containing functional groups boosted diffusion and adsorption by electrostatic attraction and coordination, suggesting that DMPS-OACF (7.5,20) has great application potential in the removal of trace heavy metals.

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.

Covalent organic frameworks-based smart materials for mitigation of pharmaceutical pollutants from aqueous solution

Covalent organic frameworks (COFs) are an emergent group of crystalline porous materials that have gained incredible interest in recent years. With foreseeable controllable functionalities and structural configurations, the constructions and catalytic properties of these organic polymeric materials can be controlled to fabricate targeted materials. The specified monomer linkers and pre-designed architecture of COFs facilitate the post-synthetic modifications for introducing novel functions and useful properties. By virtue of inherent porosity, robust framework, well-ordered geometry, functionality, higher stability, and amenability to functionalization, COFs and COFs-based composites are regarded as prospective nanomaterials for environmental clean-up and remediation. This report spotlights the state-of-the-art advances and progress in COFs-based materials to efficiently mitigate pharmaceutical-based environmental pollutants from aqueous solutions. Synthesis approaches, structure, functionalization, and sustainability aspects of COFs are discussed. Moreover, the adsorptive and photocatalytic potential of COFs and their derived nanocomposites for removal and degradation of pharmaceuticals are thoroughly vetted. In addition to deciphering adsorption mechanism/isotherms, the stability, regeneratability and reproducibility are also delineated. Lastly, the outcomes are summed up, and new directions are proposed to widen the promise of COF-based smart materials in diverse fields.

Study on the efficiency of a covalent organic framework as adsorbent for the screening of pharmaceuticals in estuary waters

Herein, we demonstrate, for the first time, that covalent organic frameworks (COFs) can be efficient adsorbents for the screening of pharmaceuticals in real water samples, obtaining highly representative data on their occurrence and avoiding the cost of carrying high volume samples and tedious and costly clean-up and preconcentration steps. Of the 23 pharmaceuticals found present in the water samples from the Tagus river estuary using state-of-the-art solid-phase extraction (SPE), 22 were also detected (adsorbed and recovered for analysis) using a COF as the adsorbent material with adsorption efficiency of over 80% for nearly all compounds. In specific cases, acidification of the water samples was identified to lead to a dramatic loss of adsorption efficiency, underlining the effect of sample pre-treatment on the results. The COF efficiently adsorbed (>80%) 19 pharmaceuticals without acid treatment of the sample, highlighting the potential of this class of materials for representative in situ passive adsorption of pharmaceuticals, making this material suitable for being used in water monitoring programs as a simple and cost-efficient sample preparation procedure. In the case of α-hydroxyalprazolam and diclofenac, the COF outperformed the SPE procedure in the recovery efficiency. Although further efforts should be made in tailoring the desorption of the pharmaceuticals from the COF by using different solvents or solvent mixtures, we propose COFs as convenient adsorbent for broad-scope screening and as an efficient adsorbent material to target specific classes of pharmaceuticals. To the best of our knowledge, this is the first study on the use of COFs for contaminant screening in real, naturally contaminated water samples.

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.

A sulfur, nitrogen dual-doped porous graphene nanohybrid for ultraselective Hg(ii) separation over Pb(ii) and Cu(ii)

Two-dimensional (2D) porous graphene is attractive as a high-permeability membrane for ionic and molecular separation. Here, we propose a sulfur, nitrogen dual-doped 2D porous graphene (SNPG) nanohybrid by adopting a facile one-step process. The resulting sandwich-like porous nanohybrid features uniform ion-gated nanopores for efficient transport of target heavy metal ions while blocking undesired ions, as well as abundant multi-binding ligands for selectively chelating permeated heavy metal ions. We show from systematic experiments that this SNPG nanohybrid exhibits outstanding selectivity and ability to separate Hg(ii) ions in mixtures with eight other metal ions. An excellent uptake capability (803 mg g^-1) and high removal ability (>99%) within the entire pH range of 2-10 can be obtained. Given the specific 2D porous nanostructure and specific binding ligands, SNPG exhibits an ultrahigh separation factor towards Hg(ii) that is up to four orders of magnitude higher than those of Pb(ii), Cd(ii) and Cu(ii) ions, significantly higher than those of most reported adsorbents. These findings provide a new opportunity to develop selective materials and devices for applications such as efficient recognition, extraction and separation of target metal ions in complex aqueous environments.

Preparation, characterization and application of activated carbon from corn cob by KOH activation for removal of Hg(II) from aqueous solution

In the present study, activated carbon was prepared from corn cob. Corn cob by potassium hydroxide activation. SEM, BET, Raman, FTIR and XPS analysis methods were used to characterize the physical and chemical properties of activated carbon. The effects of adsorbent dosage, adsorption time, pH and initial Hg(II) concentration on mercury ion removal rate were studied. The specific surface area of this material is 1054.2 m2 g-1. The Langmuir and Freundlich adsorption models were used to verify the adsorption isotherms. The adsorption isotherms were simulated well by the Langmuir model, which implied that it is a monolayer adsorption process. The kinetic data conformed to the pseudo-second-order model, which implied that the predominant process is chemisorption.