Highly selective capture of phosphate ions from water by a water stable metal-organic framework modified with polyethyleneimine

Core-shell design of UiO66-Fe3O4 configured with EDTA-assisted washing for rapid adsorption and simple recovery of heavy metal pollutants from soil

The coupling of washing with adsorption process can be adopted for the treatment of soils contaminated with heavy metals pollution. However, the complex environment of soil and the competitive behavior of leaching chemicals considerably restrain adsorption capacity of adsorbent material during washing process, which demands a higher resistance of the adsorbents to interference. In this study, we synthesized strongly magnetic, high specific surface area (573.49 m2/g) UiO66 composites (i.e., UiO66-Fe3O4) using hydrothermal process. The UiO66-Fe3O4 was applied as an adsorbent during the ethylene diamine tetraacetic acid (EDTA)-assisted washing process of contaminated soil. The incorporation of UiO66-Fe3O4 results in rapid heavy metal removal and recovery from the soil under low concentrations of washing agent (0.001 mol/L) with reduced residual heavy metal mobility of soil after remediation. Furthermore, UiO66-Fe3O4 can quickly recollect by an external magnet, which offers a simple and inexpensive recovery method for heavy metals from contaminated soil. Overall, UiO66-Fe3O4 configuration with EDTA-assisted washing process showed opportunities for heavy metals contaminated sites.

Harnessing the Chemical Functionality of Metal-Organic Frameworks Toward Removal of Aqueous Pollutants

Wastewater treatment has been bestowed with a plethora of materials; among them, metal-organic frameworks (MOFs) are one such kind with exceptional properties. Besides their application in gas adsorption and storage, they are applied in many fields. In orientation toward wastewater treatment, MOFs have been and are being successfully employed to capture a variety of aqueous pollutants, including both organic and inorganic ones. This review sheds light on the postsynthetic modifications (PSMs) performed over MOFs to adsorb and degrade recalcitrant. Modifications performed on the metal nodes and the linkers have been explained with reference to some widely used chemical modifications like alkylation, amination, thiol addition, tandem modifications, and coordinate modifications. The boost in pollutant removal efficacy, reaction rate, adsorption capacity, and selectivity for the modified MOFs is highlighted. The rationale and the robustness of micromotor MOFs, i.e., MOFs with motor activity, and their potential application in the capture of toxic pollutants are also presented for readers. This review also discusses the challenges and future recommendations to be considered in performing PSM over a MOF concerning wastewater treatment.

Phosphorus removal from water by the metal-organic frameworks (MOFs)-based adsorbents: A review for structure, mechanism, and current progress

Efficacious phosphate removal is essential for mitigating eutrophication in aquatic ecosystems and complying with increasingly stringent phosphate emission regulations. Chemical adsorption, characterized by simplicity, prominent treatment efficiency, and convenient recovery, is extensively employed for profound phosphorus removal. Metal-organic frameworks (MOFs)-derived metal/carbon composites, surpassing the limitations of separate components, exhibit synergistic effects, rendering them tremendously promising for environmental remediation. This comprehensive review systematically summarizes MOFs-based materials' properties and their structure-property relationships tailored for phosphate adsorption, thereby enhancing specificity towards phosphate. Furthermore, it elucidates the primary mechanisms influencing phosphate adsorption by MOFs-based composites. Additionally, the review introduces strategies for designing and synthesizing efficacious phosphorus capture and regeneration materials. Lastly, it discusses and illuminates future research challenges and prospects in this field. This summary provides novel insights for future research on superlative MOFs-based adsorbents for phosphate removal.

A review on adsorption of heavy metals from wastewater using carbon nanotube and graphene-based nanomaterials

The rampant rise in world population, industrialization, and urbanization expedite the contamination of water sources. The presence of the non-biodegradable character of heavy metals in waterways badly affects the ecological balance. In this modern era, the unavailability of getting clear water as well as the downturn in water quality is a major concern. Therefore, the effective removal of heavy metals has become much more important than before. In recent years, the attention to better wastewater remediation was directed towards adsorption techniques with novel adsorbents such as carbon nanomaterials. This review paper primarily emphasizes the fundamental concepts, structures, and unique surface properties of novel adsorbents, the harmful effects of various heavy metals, and the adsorption mechanism. This review will give an insight into the current status of research in the realm of sustainable wastewater treatment, applications of carbon nanomaterials, different types of functionalized carbon nanotubes, graphene, graphene oxide, and their adsorption capacity. The importance of MD simulations and density functional theory (DFT) in the elimination of heavy metals from aqueous media is also discussed. In addition to that, the effect of factors on heavy metal adsorption such as electric field and pressure is addressed.

Phosphate adsorption by metal organic frameworks: Insights from a systematic review, meta-analysis, and predictive modelling with artificial neural networks

This comprehensive study analysed 55 articles published between 2011 and 2022 on the use of metal organic frameworks (MOFs) for phosphate adsorption. The study found that the performance of MOFs in phosphate adsorption is influenced by various factors such as the type of MOF, synthesis method, modification/alteration, and operational conditions (initial concentration, adsorbent dose, pH, contact time, and temperature). Most of the MOFs have a wide range of theoretical maximum adsorption capacity for phosphate, but their long-term use in phosphorus recovery may be limited due to the adsorption mechanisms being dominated by inner sphere complexation. The study employed machine learning to construct artificial neural network (ANN) models for predicting phosphate adsorption capacity based on input features from operation and synthesis procedures. The initial phosphate concentration was the most important input from the operational features, while the modulator agent was consistently relevant during MOF synthesis. The models showed strong fitting for most MOF types recorded for the study, such as UIO-66, MIL-100, ZIF-8, Al-MOFs, La-MOFs, and Ce-MOFs. Overall, this study provides valuable insights for the design of MOF adsorbents for phosphate adsorption and offers guidance for future research in this area.

Metal-Organic Frameworks Nanocarriers for Functional Nucleic Acid Delivery in Biomedical Applications

Metal-organic frameworks (MOFs), a distinctive funtionalmaterials which is constructed by various metal ions and organic molecules, have gradually attracted researchers' attention from they were founded. In the last decade, MOFs emerge as a biomedical material with potential applications due to their unique properties. However, the MOFs performed as nanocarriers for functional nucleic acid delivery in biomedical applications rarely summarized. In this review, we introduce recent developments of MOFs for nucleic acid delivery in various biologically relevant applications, with special emphasis on cancer therapy (including siRNA, ASO, DNAzyme, miRNA and CpG oligodeoxynucleotides), bioimaging, biosensors and separation of biomolecules. We expect the accomplishment of this review could benefit certain researchers in biomedical field to develop novel sophisticated nanocarriers for functional nucleic acid delivery based on the promising material of MOFs.

Phosphorus removal and recovery: state of the science and challenges

Phosphorus is one of the main nutrients required for all life. Phosphorus as phosphate form plays an important role in different cellular processes. Entrance of phosphorus in the environment leads to serious ecological problems including water quality problems and soil pollution. Furthermore, it may cause eutrophication as well as harmful algae blooms (HABs) in aquatic environments. Several physical, chemical, and biological methods have been presented for phosphorus removal and recovery. In this review, there is an overview of phosphorus role in nature provided, available removal processes are discussed, and each of them is explained in detail. Chemical precipitation, ion exchange, membrane separation, and adsorption can be listed as the most used methods. Identifying advantages of these technologies will allow the performance of phosphorus removal systems to be updated, optimized, evaluate the treatment cost and benefits, and support select directions for further action. Two main applications of biochar and nanoscale materials are recommended.

Preparation of PAMAM modified PVDF membrane and its adsorption performance for copper ions

As one of the main pollutants of water pollution, the potential toxicity of heavy metal ions always threatens the safety of human and nature. Therefore, how to effectively remove heavy metal ions has become an important research topic in environmental protection. In the existing research, adsorption method is outstanding from many methods because of its high adsorption efficiency and easy operation. In this study, different generations of hyperbranched polyamide-amine (PAMAM) were grafted onto PVDF membrane to obtain the membrane with high adsorption capacity for heavy metal ions. The structure and physicochemical properties of the membranes were evaluated by means of fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (FE-SEM), element analyzer and X-ray photoelectron spectroscopy (EDX). At the same time, various factors affecting the adsorption process were studied, and it was found that the adsorption behavior of copper ion (Cu²⁺) on the membrane conformed to the pseudo-first-order kinetic model and Langmuir isotherm model. Moreover, after comparing the adsorption effect of the modified membranes grafted with different generations of PAMAM, it was found that the membrane grafted with the third generation PAMAM had the best adsorption when the solution pH was 5, and its maximum adsorption capacity could reach 153.8 mg/g. After five adsorption-desorption cycles, its adsorption capacity can reach 72.83% of the first test, indicating that it has good recycling performance. The results show that the adsorption membrane has good application potential and research value.

Postsynthetic Modification of the Magnetic Zirconium-Organic Framework for Efficient and Rapid Solid-Phase Extraction of DNA

In recent years, several approaches have been applied to modify metal-organic frameworks (MOFs) owing to their excellent structural tunability such as higher extraction efficiency than that of primitive crystals. Herein, Zr-based MOFs (UiO-66-NH₂) with a suitable size modulated by acetic acid were successfully synthesized for effective DNA extraction. The bonding conformations and adsorption mechanism indicated a high affinity between UiO-66-NH₂ and the DNA molecules. Furthermore, Fe₃O₄ nanoparticles were immobilized on the UiO-66-NH₂ surface to allow MOFs with magnetism. The magnetic zirconium-organic framework (MZMOF) retained the intact structure of MOFs and simplified subsequent extraction operations. In the DNA recovery investigation, MZMOF showed high recovery efficiency for both short-stranded DNA (90.4%) and pseudovirus DNA (95.1%). In addition, it showed superior DNA extraction efficiency from plasma (57.6%) and swab preservation solution (86.5%). The prepared MZMOF was employed for highly specific extraction of viral DNA and cfDNA from samples. To further simplify the extraction process, MZMOF was applied to immiscible phase filtration assisted by a surface tension (IFAST) chip for facilitating rapid DNA extraction with sensitive point-of-care testing. The developed MZMOF-based extraction method has significant potential for increasing the demand for rapid and efficient nucleic acid extraction.

Exploring the Mechanisms of Selectivity for Environmentally Significant Oxo-Anion Removal during Water Treatment: A Review of Common Competing Oxo-Anions and Tools for Quantifying Selective Adsorption

Development of novel adsorbents often neglects the competitive adsorption between co-occurring oxo-anions, overestimating realistic pollutant removal potentials, and overlooking the need to improve selectivity of materials. This critical review focuses on adsorptive competition between commonly co-occurring oxo-anions in water and mechanistic approaches for the design and development of selective adsorbents. Six "target" oxo-anion pollutants (arsenate, arsenite, selenate, selenite, chromate, and perchlorate) were selected for study. Five "competing" co-occurring oxo-anions (phosphate, sulfate, bicarbonate, silicate, and nitrate) were selected due to their potential to compete with target oxo-anions for sorption sites resulting in decreased removal of the target oxo-anions. First, a comprehensive review of competition between target and competitor oxo-anions to sorb on commonly used, nonselective, metal (hydr)oxide materials is presented, and the strength of competition between each target and competitive oxo-anion pair is classified. This is followed by a critical discussion of the different equations and models used to quantify selectivity. Next, four mechanisms that have been successfully utilized in the development of selective adsorbents are reviewed: variation in surface complexation, Lewis acid/base hardness, steric hindrance, and electrostatic interactions. For each mechanism, the oxo-anions, both target and competitors, are ranked in terms of adsorptive attraction and technologies that exploit this mechanism are reviewed. Third, given the significant effort to evaluate these systems empirically, the potential to use computational quantum techniques, such as density functional theory (DFT), for modeling and prediction is explored. Finally, areas within the field of selective adsorption requiring further research are detailed with guidance on priorities for screening and defining selective adsorbents.

Influence of coexisting calcium and magnesium ions on phosphate adsorption onto hydrous iron oxide

Removal of phosphorus (P) from municipal wastewater is of vital importance to the control of eutrophication in receiving freshwater bodies. Typical cations such as Ca²⁺ and Mg²⁺ generally exist in municipal wastewater, and they may affect the sorption behavior and mechanism of iron oxide-based materials for aqueous phosphate (H_xPO₄^x - 3, x = 0, 1, 2, or 3 depending on solution pH). To better apply iron oxide-containing materials as adsorbents to eliminate H_xPO₄^x - 3 in municipal wastewater, a hydrous ferric oxide (HFEO) was prepared and characterized at first and then the impact of coexisting Ca²⁺ and Mg²⁺ on the uptake of H_xPO₄^x - 3 by HFEO was studied. The results showed that, without coexisting Ca²⁺ and Mg²⁺, the kinetic data for H_xPO₄^x - 3 sorption onto HFEO were better described by the Elovich model (R² = 0.953) than the pseudo-second-order (R² = 0.838) and pseudo-first-order (R² = 0.641) models, and the isotherm data were fitted better with the Dubinin-Radushkevich (R² = 0.966) and Freundlich (R² = 0.953) models than with the Langmuir (R² = 0.924) model. The ligand exchange of the Fe-bound hydroxyl group with H_xPO₄^x - 3 and the generation of Fe-O-P bonding played a key role in the uptake of H_xPO₄^x - 3 by HFEO in the absence of Ca²⁺ and Mg²⁺. Coexisting Ca²⁺ and Mg²⁺ greatly improved the adsorptive removal of H_xPO₄^x - 3 by HFEO, including the adsorption capacity and initial adsorption rate. According to the Langmuir isotherm equation, the predicted maximum H_xPO₄^x - 3 adsorption capacity for HFEO at pH 7 in the presence of 2 mmol/L Ca²⁺ (24.7 mg P/g) or 2 mmol/L Mg²⁺ (18.4 mg P/g) was much larger than that without coexisting Ca²⁺ and Mg²⁺ (10.7 mg P/g). The formation of aqueous CaHPO₄⁰ and MgHPO₄⁰ species firstly and then the adsorption of the formed CaHPO₄⁰ and MgHPO₄⁰ species on the HFEO surface to generate the HPO₄^2--bridged ternary complexes (i.e., Fe(OPO₃H)Ca⁺ and Fe(OPO₃H)Mg⁺) had an important role in the improvement of H_xPO₄^x - 3 adsorption onto HFEO by coexisting Ca²⁺ and Mg²⁺.

Smart Metal-Organic Framework-Based Nanoplatforms for Imaging-Guided Precise Chemotherapy

Good biocompatibility, active tumor targeting, and stimulus-responsive release offer great opportunity for precise imaging-guided tumor treatment. However, the current strategies for the fabrication of smart theranostic platforms suffer from tedious synthesis processes. Here, we propose a universal and facile strategy for the fabrication of smart nanoscale metal-organic framework (NMOF)-based nanoplatforms for imaging-guided precise chemotherapy. As a proof of concept, 5-boronobenzene-1,3-dicarboxylic acid (BBDC), as a versatile ligand, was employed for the first time with Gd³⁺ as metal nodes to prepare a smart magnetic resonance (MR) imaging-guided drug-delivery system. Specific reversible diol-borate condensation enables effortless coating of glucose on the NMOFs to improve their biocompatibility. The specific interaction between glucose and glucose-transported protein ensures active tumor-targeting ability. Moreover, the glucose layer, as a pH-responsive diol-borate gatekeeper, prevents the premature leakage of drugs. The proposed smart theranostic nanoplatform was well used in MR imaging-guided tumor-targeted precise chemotherapy. This strategy is simply extended to the design of other MOF-glucose composites for diverse applications, such as X-ray computed tomography imaging of gastrointestinal tract with Yb-MOFs-Glu. BBDC, as a functional ligand, provides a simple and universal way to fabricate smart NMOF theranostic platforms with multifunction as "three birds with one stone". The facile and universal strategy lays down a new way to develop multifunctional nanoagents for precision medicine.

Performance of metal–organic frameworks for the adsorptive removal of potentially toxic elements in a water system: a critical review

Elevated levels of potentially toxic elements (PTEs) in aqueous environments have drawn attention recently due to their presence and toxicity to living beings. There have been numerous attempts to remove PTEs from aqueous media. The potential of metal–organic frameworks (MOFs) in removing PTEs from aqueous media has been recognized due to their distinctive advantages (e.g., increased removal capability, large surface area, adjustable porosity, and recyclability). Because of the poor stability of MOFs in water, pre and post synthetic modification and functionalization of MOFs have also been developed for water treatment investigations. This review addresses the performance and mechanisms of PTE removal in various modified MOFs in detail. In order to compare the performance of MOFs, here we used partition coefficient (PC) instead of maximum adsorption capacity, which is sensitively influenced by initial loading concentrations. Therefore, the PC of each material was used to evaluate the adsorption performance of different MOFs and to compare with other sorbents. Furthermore, it discusses the scale-up issues and forthcoming pathway for the research and development needs of MOFs for effective PTE removal. This review further elucidates the main removal mechanisms of PTEs by MOFs. Commercial or domestic water treatment systems or water filters can utilize engineered MOFs to treat water by adsorptive removal. However, marketable products have yet to be investigated thoroughly due to limitations of the large-scale synthesis of MOFs.

This review examines the performance of metal–organic frameworks based on partition coefficient data over the classic maximum adsorption capacities.