High Performance of UiO-66 Metal–Organic Framework Modified with Melamine for Uptaking of Lead and Cadmium from Aqueous Solutions

Design and application of metal organic frameworks for heavy metals adsorption in water: a review

The growing apprehension surrounding heavy metal pollution in both environmental and industrial contexts has spurred extensive research into adsorption materials aimed at efficient remediation. Among these materials, Metal-Organic Frameworks (MOFs) have risen as versatile and promising contenders due to their adjustable properties, expansive surface areas, and sustainable characteristics, compared to traditional options like activated carbon and zeolites. This exhaustive review delves into the synthesis techniques, structural diversity, and adsorption capabilities of MOFs for the effective removal of heavy metals. The article explores the evolution of MOF design and fabrication methods, highlighting pivotal parameters influencing their adsorption performance, such as pore size, surface area, and the presence of functional groups. In this perspective review, a thorough analysis of various MOFs is presented, emphasizing the crucial role of ligands and metal nodes in adapting MOF properties for heavy metal removal. Moreover, the review delves into recent advancements in MOF-based composites and hybrid materials, shedding light on their heightened adsorption capacities, recyclability, and potential for regeneration. Challenges for optimization, regeneration efficiency and minimizing costs for large-scale applications are discussed.

A novel synergistic enzyme-antibiotic therapy with immobilization of mycobacteriophage Lysin B enzyme onto Rif@UiO-66 nanocomposite for enhanced inhaled anti-TB therapy; Nanoenzybiotics approach

The emergence of antibiotic-resistant and phage-resistant strains of Mycobacterium tuberculosis (M. tuberculosis) necessitates improving new therapeutic plans. The objective of the current work was to ensure the effectiveness of rifampicin and the mycobacteriophage LysB D29 (LysB)enzyme in the treatment of multi-drug resistant tuberculosis (MDR-TB) infection, where new and safe metal-organic framework (MOF) nanoparticles were used in combination. UiO-66 nanoparticles were synthesized under mild conditions in which the antimycobacterial agent (rifampicin) was loaded (Rif@UiO-66) and LysB D29 enzyme immobilized onto Rif@UiO-66, which were further characterized. Subsequently, the antibacterial activity of different ratios of Rif@UiO-66 and LysB/Rif@uio-66 against the nonpathogenic tuberculosis model Mycobacterium smegmatis (M. smegmatis) was evaluated by minimum inhibitory concentration (MIC) tests. Impressively, the MIC of LysB/Rif@uio-66 was 16-fold lower than that of pure rifampicin. In vitro and in vivo toxicity studies proved that LysB/Rif@UiO-66 is a highly biocompatible therapy for pulmonary infection. A biodistribution assay showed that LysB/Rif@UiO-66 showed a 5.31-fold higher drug concentration in the lungs than free rifampicin. A synergistic interaction between UiO-66, rifampicin and the mycobacteriophage lysB D29 enzyme was shown in the computational method (docking). Therefore, all results indicated that the LysB/Rif@UiO-66 nanocomposite exhibited promising innovative enzyme-antibiotic therapy for tuberculosis treatment.

Remediation of multifarious metal ions and molecular docking assessment for pathogenic microbe disinfection in aqueous solution by waste-derived Ca-MOF

The present study demonstrates an eco-friendly and cost-effective synthesis of calcium terephthalate metal-organic frameworks (Ca-MOF). The Ca-MOF were composed of metal ions (Ca2+) and organic ligands (terephthalic acid; TPA); the former was obtained from egg shells, and the latter was obtained from processing waste plastic bottles. Detailed characterization using standard techniques confirmed the synthesis of Ca-MOF with an average particle size of 461.9 ± 15 nm. The synthesized Ca-MOF was screened for its ability to remove multiple metal ions from an aqueous solution. Based on the maximum sorption capacity, Pb2+, Cd2+, and Cu2+ ions were selected for individual parametric batch studies. The obtained results were interpreted using standard isotherms and kinetic models. The maximum sorption capacity (qm) obtained from the Langmuir model was found to be 644.07 ± 47, 391.4 ± 26, and 260.5 ± 14 mg g-1 for Pb2+, Cd2+, and Cu2+, respectively. Moreover, Ca-MOF also showed an excellent ability to remove all three metal ions simultaneously from a mixed solution. The metal nodes and bonded TPA from Ca-MOF were dissociated by the acid dissolution method, which protonated and isolated TPA for reuse. Further, the crystal structure of Ca-MOF was prepared and docked with protein targets of selected pathogenic water-borne microbes, which showed its disinfection potential. Overall, multiple metal sorption capability, regeneration studies, and broad-spectrum antimicrobial activity confirmed the versatility of synthesized Ca-MOF for industrial wastewater treatment.

Evaluating the Role of Functional Groups in the Selective Capture of Ag(I) onto UiO-66-Type Metal-Organic Frameworks

UiO-66-type metal-organic frameworks have been considered as promising adsorbents for capturing Ag(I) from wastewater. However, uncertainties persist regarding the specific absorptivity of individual functional groups to the UiO-66 framework structure. In this study, UiO-66-type metal-organic frameworks (UiO-66-X), featuring diverse functional groups (X = -(OH)2, -(COOH)2, -NO2, -NH2, -SO3H, -(SH)2), were synthesized in situ for Ag(I) capture. The findings revealed that functionalization significantly enhanced the adsorption capacity of Ag(I). Notably, quantitative analysis showed that 1 mol of -SH functional group onto the UiO-66 framework structure can adsorb 0.73 mol of Ag(I) ions, surpassing those of -COOH, -OH, -NH2, -SO3H, and -NO2 by 2.4-, 3.5-, 3.8-, 9.1-, and 24.3-fold, respectively. This represents the first assessment of the adsorption capacity of functionalized UiO-66 for Ag(I) based on each effective functional group, addressing limitations in traditional unit mass calculations. Further, the adsorption mechanism of UiO-66-X for selectively capturing Ag(I) was elucidated through experimental and theoretical analyses. Additionally, selectivity and practical applications confirm that UiO-66-(SH)2 exhibits strong anti-interference ability, whether in natural water bodies with complex compositions or in industrial wastewater under harsh conditions. We anticipate that this study will enhance our understanding of structure-performance dependencies of multivariate MOFs for designing novel adsorbents for Ag(I) capture.

Silk nanofibrils-MOF composite membranes for pollutant removal from water

Membrane separation technology is considered an effective strategy to remove pollutants in sewage. However, it remains a significant challenge to fabricate inexpensive membranes with high purification efficiency. Therefore, the present study proposes the integration of silk nanofibrils (SNFs) and polydopamine⊂metal-organic framework (PDA⊂MOF) nanoparticles to prepare self-supporting membranes, which can effectively intercept nanoparticle pollutants through the size exclusion effect and can strongly adsorb organic dyes and metal ions by SNF. In addition, PDA⊂MOF enables these membranes to adsorb small molecules and heavy metal ions during the filtration process, thereby effectively removing various pollutants from sewage. The integration of size-exclusion and adsorption capabilities enables the SNF/PDA⊂MOF membrane to remove nanoparticles, small-molecule dyes, heavy metal ions, and radioactive elements. This work provides a rational approach for the design and development of the next generation of water treatment membranes and is expected to be used in environmental, food-related, and biomedical fields.

Functional MOF-Based Materials for Environmental and Biomedical Applications: A Critical Review

Over the last ten years, there has been a growing interest in metal-organic frameworks (MOFs), which are a unique category of porous materials that combine organic and inorganic components. MOFs have garnered significant attention due to their highly favorable characteristics, such as environmentally friendly nature, enhanced surface area and pore volume, hierarchical arrangements, and adjustable properties, as well as their versatile applications in fields such as chemical engineering, materials science, and the environmental and biomedical sectors. This article centers on examining the advancements in using MOFs for environmental remediation purposes. Additionally, it discusses the latest developments in employing MOFs as potential tools for disease diagnosis and drug delivery across various ailments, including cancer, diabetes, neurological disorders, and ocular diseases. Firstly, a concise overview of MOF evolution and the synthetic techniques employed for creating MOFs are provided, presenting their advantages and limitations. Subsequently, the challenges, potential avenues, and perspectives for future advancements in the utilization of MOFs in the respective application domains are addressed. Lastly, a comprehensive comparison of the materials presently employed in these applications is conducted.

Synthesis, characterization, and application of pristine and clay-templated carbon xerogel microspheres for removing diclofenac and heavy metals from water solution

Organic xerogel microspheres (SX) were synthesized by inverse emulsion sol-gel polymerization and carbonized to obtain carbon xerogel spheres (SXCs). The catalyst was K₂CO₃ or Fe(C₂H₃O₂)₂, and the clay sodium sepiolite (SNa) or exfoliated vermiculite (V_exf) was added during the synthesis. Depending on the catalyst and clays, the SXCs were designated SXC-K, SXC-Fe, V_exf-K, V_exf-Fe, SNa-Fe, and SNa-K. At pH = 7 and T = 25 °C, the SXCs' adsorption capacities towards diclofenac (DCF) in water increased as follows: SXC-K < V_exf-Fe < SXC-Fe < SNa-Fe < SNa-K < V_exf-K and this order is associated with the SXCs' surface area and mesopore volume. The V_exf-K displayed the highest capacity for DCF due to its optimal textural and chemical properties, and the DCF maximum uptake was 560 mg/g at pH = 6 and T = 35 °C. The adsorption capacity towards Cd²⁺ and Pb²⁺ decreased as SX-K > SX-Fe > SXC-K > SXC-Fe, indicating that the non-carbonized materials (SX) presented higher adsorption capacity than the SXCs because the SXs had a higher acidic site content. Adding SNa or V_exf to SXs enhanced the adsorption capacity towards Cd(II), and SNa-SX-K presented an exceptionally high capacity of 182.7 mg/g. This synergistic effect revealed that the Cd²⁺ was adsorbed on the SX-K acidic sites and by cation exchange on the SNa.

Recent progress on adsorption of cadmium ions from water systems using metal-organic frameworks (MOFs) as an efficient class of porous materials

Various articles have been written about MOFs, which are organic-inorganic polymer structures that are unique in three-dimensional porosity, crystalline structure, and their ability to adsorb cadmium ion pollutants from aqueous solutions. These materials possess active metal sites, highly porous structures, high specific surfaces, high chemical functionality, and porous topologies. It is necessary to study adsorption kinetics, isotherms, and mechanisms in order to better understand the adsorption process. Adsorption kinetics can provide information about the adsorption rate and reaction pathway of adsorbents. Adsorption isotherms analyze the possibility of absorbances based on the Gibbs equation and thermodynamic theories. Moreover, in practical applications, knowledge of the adsorption mechanism is essential for predicting adsorption reactions and designing MOFs structures. In this review, the latest suggested adsorption mechanisms, kinetics, and isotherms of MOFs-based materials for removing cadmium ions are presented. A comparison is then conducted between different MOFs and the mechanisms of cadmium ion removal. We also discuss the future role of MOFs in removing environmental contaminants. Lastly, we discuss the gap in research and limitations of MOFs as adsorbents in actual applications, and probable technology development for the development of cost-efficient and sustainable MOFs for metal ion removal.