Two dimensional (2D) molecular frameworks for rapid and selective adsorption of hazardous aromatic dyes from aqueous phase

Lanthanum hydroxide@cellulose membranes with tunable pore sizes for selective removal of dyes with the same charges

Adsorptive membranes for the efficient separation of dyes with the same charges are quite desirable. Herein, a novel membrane of lanthanum hydroxide/cellulose hydrogel coated filter paper (LC) was prepared through a facile strategy of dip-coating followed by freeze-shaping. With the aid of cellulose gel, the generated La(OH)3 achieved fine dispersion. In addition, the pore size of LC membrane could be regulated by altering the cellulose concentration or the lanthanum chloride dosage, which was crucial for its water flux. In particular, the obtained membrane possessed a high water flux (128.4 L m-2 h-1) and a high dye rejection (97.2 %) for anionic Congo red (CR) only driven by the gravity, which outperformed many previously reported membranes. More intriguingly, its dye rejection for anionic methyl orange (MO) was only 0.9 %, exhibiting high selectivity for dyes with the same charges. Single-solute adsorption experiments indicated that the CR adsorption on the membrane was best fitted by the pseudo-first-order kinetic model, and it followed the Langmuir monolayer adsorption mechanism.

Recent Advances in Metal-Organic Frameworks and Their Derivatives for Adsorption of Radioactive Iodine

Radioactive iodine (131I) with a short half-life of ~8.02 days is one of the most commonly used nuclides in nuclear medicine. However, 131I easily poses a significant risk to human health and ecological environment. Therefore, there is an urgent need to develop a secure and efficient strategy to capture and store radioactive iodine. Metal-organic frameworks (MOFs) are a new generation of sorbents with outstanding physical and chemical properties, rendering them attractive candidates for the adsorption and immobilization of iodine. This review focuses on recent research advancements in mechanisms underlying iodine adsorption over MOFs and their derivatives, including van der Waals interactions, complexing interactions, and chemical precipitation. Furthermore, this review concludes by outlining the challenges and opportunities for the safe disposal of radioactive iodine from the perspective of the material design and system evaluation based on our knowledge. Thus, this paper aims to offer necessary information regarding the large-scale production of MOFs for iodine adsorption.

2-[(E)-(2-carboxybenzylidene) amino] ethan ammonium-like amino acid zwitterions: crystal structure, functional studies and its molecular dynamic simulation study with drug target receptors

The novel synthetic amino acid-like zwitterion containing imine bond ionic compound 2-[(E)-(2-carboxy benzylidene) amino] ethan ammonium salt, C10H12N2O2, was synthesized. Computational functional characterization is now being used to predict novel compounds. Here, we report on a titled combination that has been crystallizing in orthorhombic space group Pcc2 with Z = 4. The zwitterions form centrosymmetric dimers to polymeric supramolecular network via intermolecular N-H… O hydrogen bonds between the carboxylate groups and ammonium ion. The components are linked by ionic (N+-H-O-) and hydrogen bonds (N+-H-O), forming a complex three-dimensional supramolecular network. Further, molecular computational docking characterization study was performed with compound against multi-disease drug target biomolecule of anticancer target molecule of HDAC8 (PDB ID 1T69) receptor and antiviral molecular target protease (PDB ID 6LU7) to evaluate the interaction stability, conformational changes and to get insights into the natural dynamics on different timescales in solution. HighlightsThe novel zwitter ionic amino acid compound 2-[(E)-(2-carboxybenzylidene) amino] ethan ammonium salt, C10H12N2O2.The crystal structure determined for this compound illustrates the presence of intermolecular ionic N+-H-O- and N+-H-O hydrogen bonds between the carboxylate groups and ammonium ion, which influence the formation of a complex three-dimensional supramolecular polymeric network.Molecular docking studies helps to understand the conformational stability and interaction stabilityThe novel molecule can be considered for anticancer treatment.

Recent Development of Metal-Organic Frameworks for Water Purification

Water contamination is an increasing concern to mankind because of the increasing amount of pollutants in aquatic ecosystems. To purify the polluted water, various techniques have been used to remove hazardous components. Unfortunately, traditional cleanup techniques with a low uptake capacity are unable to achieve water purification. Metal-organic frameworks (MOFs) have recently shown potential in effective water pollutant isolation in terms of selectivity and adsorption capacity over traditional porous materials. The high surface area and versatile functionality of MOFs allow for the development of new adsorbents. The development of MOFs in a range of water treatments in the recent five years will be highlighted in this review, along with assessments of the adsorption performance relevant to the particular task. Moreover, the outlook on future opportunities for water purification using MOFs is also provided.

Optimization of hydrothermal synthesis conditions of Bidens pilosa-derived NiFe2O4@AC for dye adsorption using response surface methodology and Box-Behnken design

The presence of stable and hazardous organic dyes in industrial effluents poses significant risks to both public health and the environment. Activated carbons and biochars are widely used adsorbents for removal of these pollutants, but they often have several disadvantages such as poor recoverability and inseparability from water in the post-adsorption process. Incorporating a magnetic component into activated carbons can address these drawbacks. This study aims to optimizing the production of NiFe2O4-loaded activated carbon (NiFe2O4@AC) derived from a Bidens pilosa biomass source through a hydrothermal method for the adsorption of Rhodamine B (RhB), methyl orange (MO), and methyl red (MR) dyes. Response surface methodology (RSM) and Box-Behnken design (BBD) were applied to analyze the key synthesis factors such as NiFe2O4 loading percentage (10-50%), hydrothermal temperature (120-180 °C), and reaction time (6-18 h). The optimized condition was found at a NiFe2O4 loading of 19.93%, a temperature of 135.55 °C, and a reaction time of 16.54 h. The optimum NiFe2O4@AC demonstrated excellent sorption efficiencies of higher than 92.98-97.10% against all three dyes. This adsorbent was characterized, exhibiting a well-developed porous structure with a high surface area of 973.5 m2 g-1. Kinetic and isotherm were studied with the best fit of pseudo-second-order, and Freundlich or Temkin. Qmax values were determined to be 204.07, 266.16, and 177.70 mg g-1 for RhB, MO, and MR, respectively. By selecting HCl as an elution, NiFe2O4@AC could be efficiently reused for at least 4 cycles. Thus, the Bidens pilosa-derived NiFe2O4@AC can be a promising material for effective and recyclable removal of dye pollutants from wastewater.

Synergetic enhancement effect of two-dimensional MoS2 nanosheets and metal organic framework-derived porous ZnO nanorods for photodegradation performance

Two-dimensional transition metal dichalcogenides and semiconductor metal oxides have shown great potential in photocatalysis. However, their stability and efficiency need to be further improved. In this paper, porous ZnO nanorods with high specific surface area were prepared from metal-organic framework ZIF-8 by a simple hydrothermal method. A MoS2/ZnO composite was constructed by loading MoS2 onto the surface of porous ZnO nanorods. Compared with ZnO materials prepared by other methods, MoS2/ZnO prepared in this paper exhibits superior photocatalytic performance. The enhanced photocatalytic activity of the MoS2/ZnO composite can be attributed to the formation of heterojunctions and strong interaction between them, which greatly facilitate the separation of electrons and holes at the contact interface. In addition, due to the wide absorption region of the visible spectrum, MoS2 can greatly broaden the light absorption range of the material after the formation of the composite material, increase the utilization rate of visible light, and reduce the combination of electrons and holes. This study provides a new way to prepare cheap and efficient photocatalysts.

Structural and Theoretical Study of Copper(II)-5-fluoro Uracil Acetate Coordination Compounds: Single-Crystal to Single-Crystal Transformation as Possible Humidity Sensor

This paper describes the synthesis and characterization of seven different copper(II) coordination compounds, as well as the formation of a protonated ligand involving all compounds from the same reaction. Their synthesis required hydrothermal conditions, causing the partial in situ transformation of 5-fluoro uracil-1-acetic acid (5-FUA) into an oxalate ion (ox), as well as the protonation of the 4,4'-bipyridine (bipy) ligand through a catalytic process resulting from the presence of Cu(II) within the reaction. These initial conditions allowed obtaining the new coordination compounds [Cu₂(5-FUA)₂(ox)(bipy)]_n·2n H₂O (CP2), [Cu(5-FUA)₂(H₂O)(bipy)]_n·2n H₂O (CP3), as well as the ionic pair [(H₂bipy)⁺² 2NO₃^-] (1). The mother liquor evolved rapidly at room temperature and atmospheric pressure, due to the change in concentration of the initial reagents and the presence of the new chemical species generated in the reaction process, yielding CPs [Cu(5-FUA)₂(bipy)]_n·3.5n H₂O, [Cu₃(ox)₃(bipy)₄]_n and [Cu(ox)(bipy)]_n. The molecular compound [Cu(5-FUA)₂(H₂O)₄]·4H₂O (more thermodynamically stable) ended up in the mother liquor after filtration at longer reaction times at 25 °C and 1 atm., cohabiting in the medium with the other crystalline solids in different proportions. In addition, the evaporation of H₂O caused the single-crystal to single-crystal transformation (SCSC) of [Cu(5-FUA)₂(H₂O)(bipy)]_n·2n H₂O (CP3) into [Cu(5-FUA)₂(bipy)]_n·2n H₂O (CP4). A theoretical study was performed to analyze the thermodynamic stability of the phases. The observed SCSC transformation also involved a perceptible color change, highlighting this compound as a possible water sensor.

Synthesis of 2D Metal-Organic Nanosheets (MONs) by Liquid Phase Exfoliation: Applications in Effective Delivery of Antiulcer Drugs and Selective Adsorption and Removal of Cationic Dyes

Nowadays, the fabrication of 2D metal-organic nanosheets (2D MONs) has entered the research arena fascinating researchers worldwide. However, a lack of efficient and facile methods has remained a bottleneck for the manufacturing of these 2D MONs. Herein, a 2D metal-organic framework (MOF), i.e., 2D Cu-MOF, was synthesized using a facile and convenient stirring method by using 4,4'-trimethylenedipyridine (TMDP) as an organic linker. The as-prepared MOF was characterized in detail and based on single crystal X-ray diffraction analysis, it was established that tangled layers in the 2D Cu-MOF are interconnected to produce thick strands. These tangled layers could be easily separated via ultrasonication-induced liquid phase exfoliation (UILPE) to give the 2D Cu-MON as illustrated through Tyndall light scattering and exhaustive microscopic exploration such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The application of this 2D Cu-MON was assessed in the field of drug delivery revealing exceptional drug loading for the drug lansoprazole (LPZ) by 2D Cu-MONs as well as drug release in the acidic and neutral medium demonstrating that the 2D Cu-MON is an excellent carrier for antiulcer drug delivery. For environmental protection, the application of 2D Cu-MON was also examined toward the removal of various cationic and anionic dyes with excellent selectivity toward cationic dye removal. The plausible mechanism for dye removal indicated the involvement of cation-π and π-π interactions, for the effective adsorption of cationic dyes as well as a increase in the surface area of 2D Cu-MON by UILPE. Remarkably, the high drug loading and dye removal are imputed to the increase in surface area by UILPE. In a nutshell, the developed 2D Cu-MON will prove to be beneficial for application in the field of drug delivery as well as for wastewater treatment.

Series of Dual Functional Two-Dimensional RE-OFs for Nitrophenol Reduction and Dye Separation

The rational design and preparation of stable and multifunctional metal-organic frameworks (MOFs) with excellent catalysis and adsorption properties are desirable but are great challenges. The nitrophenol (NP) reduction to aminophenols (APs) by using the catalyst Pd@MOFs is an effective strategy, which has attracted extensive attention in recent years. Here, we report four stable isostructural two-dimensional (2D) rare earth metal-organic frameworks [RE₄(AAPA)₆(DMA)₂ (H₂O)₄][DMA]₃[H₂O]₈ (namely LCUH-101, RE = Eu, Gd, Tb, Y; AAPA^2- = 5-[(anthracen-9-yl-methyl)-amino]-1,3-isophthalate), which feature a 2D layer structure with sql topology of point symbol {4⁴·6²} and exhibit excellent chemical stability and thermostability. The as-synthesized Pd@LCUH-101 was utilized for the catalytic reduction of 2/3/4-nitrophenol, which indicates high catalytic activity and recyclability attributed to the synergistic effect between Pd nanoparticles and the 2D layered structure. Of note, the turnover frequency (TOF), the reaction rate constant (k), and the activation energy (E_a) of Pd@LCUH-101 (Eu) in the reduction of 4-NP, respectively, are 1.09 s^-1, 2.17 min^-1, and 50.2 kJ·mol^-1, which show that it has superior catalytic activity. Remarkably, LCUH-101 (Eu, Gd, Tb, and Y) are multifunctional MOFs that can effectively absorb and separate mixed dyes. The appropriate interlayer spacing enables them to efficiently adsorb methylene blue (MB) and rhodamine B (RhB) in aqueous solution, with adsorption capacities of 0.97 and 0.41 g·g^-1, respectively, which is one of the highest values among those of the reported MOF-based adsorbers. Meanwhile, LCUH-101 (Eu) can be used for the separation of the dye mixture MB/MO and RhB/MO, and the excellent reusability enables LCUH-101 (Eu) to be used as chromatographic column filters to quickly separate and recover dyes. Therefore, this work provides a new strategy for the exploitation of stable and efficient catalysts for NP reduction and adsorbents for dyes.

Water stable MOFs as emerging class of porous materials for potential environmental applications

Metal-organic frameworks (MOFs) are extensively recognized for their wide applications in a variety of fields such as water purification, adsorption, sensing, catalysis and drug delivery. The fundamental characteristics of the majority of MOFs, such as their structure and shape, are known to be sensitively impacted by water or moisture. As a result, a thorough evaluation of the stability of MOFs in respect to factors linked to these property changes is required. It is quite rare for MOFs in their early stages to have strong water-stability, which is necessary for the commercialization and development of wider applications of this interesting material. Also, numerous applications in presence of water have progressed considerably as a "proof of concept" stage in the past and a growing number of water-stable MOFs (WSMOFs) have been discovered in recent years. This review discusses the variables and processes that affect the aqueous stability of several MOFs, including imidazolate and carboxylate frameworks. Accordingly, this article will assist researchers in accurately evaluating how water affects the stability of MOFs so that effective techniques can be identified for the advancement of water-stable metal-organic frameworks (WSMOFs) and for their effective applications toward a variety of fields.

A hydrostable CuII coordination network prepared hydrothermally as a "turn-on" fluorescent sensor for S2- and a selective adsorbent for methylene blue

The effective monitoring of water pollution and further purification are pressing yet challenging issues for guaranteeing the health of human beings and the stabilization of ecological systems. For this purpose, the development of efficient sensing and adsorption materials as a result of supramolecular interactions, including coordination and H-bonding etc., have been attracting increasing attention. With the aid of a coordination-driven self-assembly strategy, a new nonporous 2D CuII coordination network, [Cu2L(H2O)2]n (donated as CuCP), based on H4L, where H4L = 4-(4-(3,5-di-carboxy-pyridin-4-yl)phenyl)pyridine-2,6-dicarboxylic acid, was afforded hydrothermally. Structural analysis indicated that CuCP featured a wrinkled network similar to the ancient Chinese folding screens and constructed by the fully deprotonated ligand L4- with the coordination mode of bis(μ2-η1:η1:η2) and penta-coordinated Cu2+, which could be further upgraded to a supramolecular 3D framework as a result of the synergism of multiple C-H⋯O hydrogen bonds. The hydrostability of CuCP could be maintained within a wide pH range from 2 to 12 as verified by PXRD determination, endowing it with potential environmental applications. Thanks to the combination of the soft Lewis acidity of Cu2+ and its large conjugated structure, CuCP could be used as a turn-on fluorescence sensor for S2- and exhibited a different fluorescence response when Na2S, (NH4)2S or H2S were incorporated, even in actual water samples. The sensing mechanisms were disclosed in detail by the combination of experiments and density functional theory (DFT) calculations. Furthermore, CuCP was shown to be a selective and recoverable adsorbent with a maximum adsorption capacity of 379 mg g-1 in 60 minutes for methylene blue (MB). The adsorption mechanism could be a combination of π⋯π stacking, n⋯π interaction, aggregation effects and Soft and Hard Acid-Base theory (HSAB). The results presented herein open up new perspectives for CuII species in environmental applications.

Nano chromium embedded in f-CNT supported CoBi-LDH nanocomposites for selective adsorption of Pb2+and hazardous organic dyes

Transition metal-doped carbon-coated layered double hydroxides for the removal of lead (II) and hazardous organic dyes have attracted increasing attention for wastewater treatment in recent years. In this work, nanostructured CoBi-LDH/Cr@CNT composites were successfully synthesized by hydrothermal route. The CoBi-LDH/Cr@CNT was characterized by instrumental techniques such as XRD, FTIR, TEM, SEM, XPS and TGA/DTA. Adsorption of Pb²⁺ and organic dyes, i.e.,Rose Bengal (RB) and Congo red (CR) by CoBi-LDH/Cr@CNT was performed by batch experiment.The effect of several parameters including contact time, adsorbent dose, pH, temperature, and concentration was also investigated. Under optimum conditions, the adsorption capacity of CoBi-LDH/Cr@CNT for RB, CR and Pb²⁺ pollutants were (278.4 mg g^-1), (164.6 mg g^-1) and (503.2 mg g^-1) and the removal efficiency achieved is 98.2%, 95.0% and 100% respectively. The selectivity of CoBi-LDH/Cr@CNT nanocomposite towards Pb²⁺ has been studied using ICP-AES.The isothermal results were analyzed using Freundlich and Langmuir models. Adsorption isotherm for Pb²⁺(R² = 0.975), RB (R² = 0.997) and CR (R² = 0.992) agrees with the Langmuir model indicating monolayer adsorption. The sorption kinetics data well fitted pseudo-first-order model for Pb²⁺ (R² = 0.975), RB (R² = 0.996), and CR (R² = 0.995).The results demonstrated that the synthesized CoBi-LDH/Cr@CNT nanocomposite can be used as an effective sorbent for the removal of pollutants from wastewater.

Four Anderson-type [TeMo6O24]6−-based metal–organic complexes with a new bis(pyrimidine)-bis(amide): multifunctional electrochemical and adsorption performances

Four isostructural Anderson-type POM-based metal–organic complexes derived from a new bis(pyrimidine)-bis(amide) ligand were synthesized, showing multifunctional electrochemical sensing activities and good adsorption performances for organic dyes.

Significant photodegradation of carcinogenic organic dyes by a 1D supramolecular heteroleptic Cu(ii) complex under sunlight irradiation

The crucial role of supramolecular interactions in the self-assembly and architecture of the heteroleptic Cu(II) coordination polymer has been investigated and its ability to degrade organic molecules using sunlight.

Applications of water-stable metal-organic frameworks in the removal of water pollutants: A review

Because the pollutants produced by human activities have destroyed the ecological balance of natural water environment, and caused severe impact on human life safety and environmental security. Hence the task of water environment restoration is imminent. Metal-organic frameworks (MOFs), structured from organic ligands and inorganic metal ions, are notable for their outstanding crystallinity, diverse structures, large surface areas, adsorption performance, and excellent component tunability. The water stability of MOFs is a key requisite for their possible actual applications in separation, catalysis, adsorption, and other water environment remediation areas because it is necessary to safeguard the integrity of the material structure during utilization. In this article, we comprehensively review state-of-the-art research progress on the promising potential of MOFs as excellent nanomaterials to remove contaminants from the water environment. Firstly, the fundamental characteristics and preparation methods of several typical water-stable MOFs include UiO, MIL, and ZIF are introduced. Then, the removal property and mechanism of heavy metal ions, radionuclide contaminants, drugs, and organic dyes by different MOFs were compared. Finally, the application prospect of MOFs in pollutant remediation prospected. In this review, the synthesis methods and application in water pollutant removal are explored, which provide ways toward the effective use of water-stable MOFs in materials design and environmental remediation.

Efficient removal of anionic, cationic textile dyes and salt mixture using a novel CS/MIL-100 (Fe) based nanofiltration membrane

The purification of hazardous textile dyeing wastewater has exhibited many challenges because it consists of a complex mixture, including dyestuff, additives, and salts. It is necessary to fabricate membranes with enhanced permeability, fouling resistance, stability, and superior dyes and salts removal from wastewater. Incorporating a highly water stable metal-organic framework (MOFs) into membranes would meet the requirements for the efficient purification of textile wastewater. In this study, nanofiltration (NF) membranes are fabricated by incorporating MIL-100 (Fe) into the chitosan (CS) through film casting technique. The effect of MIL-100 (Fe) loadings on chitosan characterized by FT-IR, XRD, contact angle measurement, FESEM-EDS, XPS, zeta potential, and surface roughness analysis. The membrane characterization confirmed the enhanced surface roughness, pore size, surface charge, and hydrophilicity. The CS/MIL-100 (Fe) membrane exhibited an improved pure water flux from 5 to 52 L/m²h as well as 99% rejection efficiency for cationic methylene blue (MB) and anionic methyl orange (MO). We obtained the rejection efficiency trend for the MB mixed salts in the order of MgSO₄ (Mg²⁺ - 51.6%, SO₄^2- - 52.5%) > Na₂SO₄ (Na⁺ - 26.3%, SO₄^2- - 29.3%) > CaCl₂ (Ca²⁺ - 21.4%, Cl^- - 23.8%) > NaCl (Na⁺ - 16.8%, Cl^- - 19.2%). In addition, the CS/MIL-100 (Fe) composite membrane showed excellent rejection efficiency and antifouling performances with high recycling stability. These stunning results evidenced that the CS/MIL-100 (Fe) nanofiltration membrane is a promising candidate for removing toxic pollutants in the textile dyeing wastewater.

Synthesis of a 2D copper(II)-carboxylate framework having ultrafast adsorption of organic dyes

Two-dimensional (2D) coordination polymers are very interesting materials for their attractive applications. A novel 2D metal-organic framework (MOF) was derived from copper(II) and amino benzoic acid under both room temperature and solvothermal reaction conditions using different solvents. From both of the synthesis methods, an identical MOF was crystalized with monoclinic crystal system having P2₁/c space group. Hirshfeld surface analysis is carried out to explore the non-covalent interactions obtained from single crystal XRD investigation in terms of percentage contribution of each interatomic contact involved in packing of molecules into MOF structure. The microstructure analysis and surface morphology studies revealed the 2D layered regular pattern of rhombus disks of ~5 μm thickness throng together via clustering of these rhombic shaped flakes as flowers (ranging 50-100 μm in size) having uniform elemental composition. This 2D MOF efficiently adsorbed organic dyes (methylene blue, methyl orange, and methyl red) from their aqueous solutions. The 2D copper-carboxylate framework (1.2 g/L) exhibited high adsorption rates for organic dyes (0.15-0.19 mM), and >90% of these dyes could be captured as soon as they are exposed to MOF suspension (1 min) in each case. The dye removal efficiency is credited to synergy among structure, ionic strength, shapes and dimensions of dyes with respect to MOF structure. The microstructure of MOF along with electronic interactions like electrostatic, hydrogen bonding, π-π interactions and coordination to open metal sites, might contribute to the ultrafast dye adsorption process by MOF. The adsorption phenomenon is spontaneous and followed the pseudo-second order kinetic mechanism. DFT calculations revealed important electronic parameters of the dyes and model MOF systems, and novel insights with respect to possible dye-MOF interactions. The MOF remained quite stable during the dye adsorption and was regenerated easily for the successful subsequent use.

2D MOFs-based Materials for the Application of Water Pollutants Removing: Fundamentals and Prospects

Water quality can have serious impacts on human health. One crucial issue of water pollution seriously affects our safety due to the continually emerging of discovered anthropogenic pollutants. The water treatment technologies are persistent improvement to adapt such new contaminants, which accelerates the evolution of materials science to explore solving the problems. Metal-organic Frameworks (MOFs) as the significant porous and multi-dimensional networks has been concerned for toxic pollutant elimination, especially probed the applications of outstanding layered 2D skeletons MOFs-based materials. The emphases of this review highlight the 2D MOFs-based materials used in water remediation and treatment strategies including adsorption and catalysis methods. Further, the prospects and challenges of 2D MOFs-based materials for water treatments applications would be surveyed meticulously for the future research and development.

Adsorptive and Coagulative Removal of Trace Metals from Water Using Surface Modified Sawdust-Based Cellulose Nanocrystals

The presence of toxic metals in surface and natural waters, even at trace levels, poses a great danger to humans and the ecosystem. Although the combination of adsorption and coagulation techniques has the potential to eradicate this problem, the use of inappropriate media remains a major drawback. This study reports on the application of NaNO2/NaHCO3 modified sawdust-based cellulose nanocrystals (MCNC) as both coagulant and adsorbent for the removal of Cu, Fe and Pb from aqueous solution. The surface modified coagulants, prepared by electrostatic interactions, were characterized using Fourier transform infrared, X-ray diffraction (XRD), and scanning electron microscopy/energy-dispersive spectrometry (SEM/EDS). The amount of coagulated/adsorbed trace metals was then analysed using inductively coupled plasma atomic emission spectroscopy (ICP-AES). SEM analysis revealed the patchy and distributed floccules on Fe-flocs, which was an indication of multiple mechanisms responsible for Fe removal onto MCNC. A shift in the peak position attributed to C2H192N64O16 from 2θ = 30 to 24.5° occurred in the XRD pattern of both Pb- and Cu-flocs. Different process variables, including initial metal ions concentration (10–200 mg/L), solution pH (2–10), and temperature (25–45 °C) were studied in order to investigate how they affect the reaction process. Both Cu and Pb adsorption followed the Langmuir isotherm with a maximum adsorption capacity of 111.1 and 2.82 mg/g, respectively, whereas the adsorption of Fe was suggestive of a multilayer adsorption process; however, Fe Langmuir maximum adsorption capacity was found to be 81.96 mg/g. The sequence of trace metals removal followed the order: Cu > Fe > Pb. The utilization of this product in different water matrices is an effective way to establish their robustness.

Deployment of metal-organic frameworks as robust materials for sustainable catalysis and remediation of pollutants in environmental settings

From metal-organic chemistry, metal-organic frameworks (MOFs) are of supreme interest for catalysis and environmental settings. Owing to anthropogenic sources and booming industrial practices, the most challenging issue is increased water pollution and environmental insecurity. For instance, several types of synthetic dyes are toxic up to a certain extent, as emerging organic contaminants (EOCs) pose adverse environmental and potential health consequences. A gradual increase in the contamination sources and unpredictable environmental changes in terms of anthropogenic pollution severely affect both water availability and distribution. Therefore, the treatment of dyes containing wastewater matrices for water resource generation is one of the most important tasks, which must be addressed effectively. With structural tunability, MOFs have been appearing as a robust tool for remediating toxic pollutants from wastewater matrices. Moreover, the promising functionality, structural tunability, robust catalytic attributes, compatibility, large surface area, stability in water, and ease in surface functionalization make MOFs one of the considerable materials of interest. This review work spotlights the present-day progress related to MOFs and their catalytic and adsorptive chemistry for a sustainable environment. Following a brief introduction, the characteristic rendering MOFs, as adsorbents, are given with prominent examples. Next, several synthesis routes as a roadmap to engineer MOFs are discussed. From the applied perspective, the adsorptive and catalytic potentialities of MOFs as given by addressing sustainable mitigation of toxic dyes. The last section of the work illustrates key challenging issues and future directions by considering the suiting importance of MOFs.

Structure, DFT studies and evaluation of catechol oxidase (CO) mimic activity of mononuclear Co(II) complexes derived from aminoalcohols: an experimental and theoretical approach

The impetus to modeling of enzyme mimics comes from their potential to provide insight to the alternate mechanistic pathways of the native enzymes. The present study demonstrates the syntheses and characterization of two different cobalt(II) complexes, [Co(pdm)(Phen)Cl]Cl·H₂O (1) and [Co(pmmH)₂(SCN)₂] (2) with the aminoalcohol ligands such as pyridine-2,6-dimethanol (pdmH₂) or 2-pyridinemonomethanol (pmmH) and their assessment as catechol oxidase (CO) enzyme mimic. Single Crystal X-ray diffraction and powder X-ray diffraction data suggest the octahedral environment around the Co(II) ion and the complexes form extensive 1D or 2D propagating network as a result of non-covalent interactions (O···H and C-H···π). TD-DFT calculations were used to explain the spectral bands obtained during the UV-Vis absorption studies and it is ascertained that the transitions were mainly of the intra-ligand charge transfer (ILCT) type. The catecholase biomimetic catalytic activity of the synthesized complexes has been investigated in detail and the kinetics is also performed. The results obtained show that both the complexes catalyze the aerobic oxidation of catechol to the corresponding o-quinone. The K_cat value for 1 is 106.99 h^‒1 and for 2 is 90.32 h^‒1 in methanol. It may be mentioned here that 1 and 2 are effective catalysts, with the order of activity being 1 > 2. The order of enzymatic activity is well justified by CV and DFT studies.Communicated by Ramaswamy H. Sarma.

Recent advances in metal-organic frameworks as adsorbent materials for hazardous dye molecules

Water is vital for the sustenance of all forms of life. Hence, water pollution is a universal crisis for the survival for all forms of life and a hurdle in sustainable development. Textile industry is one of the anthropogenic activities that severely pollutes water bodies. Inefficient dyeing processes result in thousands of tons of synthetic dyes being dumped in water bodies every year. Therefore, the efficient removal of synthetic dyes from wastewater has become a challenging research field. Owing to their tuneable structure-property aspects, metal-organic frameworks (MOFs) have emerged as promising adsorbents for the adsorptive removal of dyes from wastewater and textile effluents. In this perspective, we highlight recent studies involving the application of MOFs for the adsorptive removal of hazardous dye molecules. We also classify the developed MOFs into cationic, anionic, and neutral framework categories to comprehend their suitability for the removal of a given class of dyes.

Zeolite modification with cellulose nanofiber/magnetic nanoparticles for the elimination of reactive red 198

In this paper for the first time, a cost-effective reinforced zeolite with cellulose nanofibers and magnetic nanoparticles (MZeo/Cellulose nanofiber) was used for the elimination of reactive red 198 (RR198) dye. The fabricated sorbent was characterized by SEM, FTIR, and XRD. The effect of operational parameters, including pH, RR198 concentration, the mass ratios of zeolite to cellulose nanofiber and zeolite coated cellulose to Fe₃O₄ nanoparticles, contact time, agitation speed, sorbent dosage, and temperature were studied. The prepared sorbent exhibited the maximum removal efficiency of 99% for RR198 removal at 30 °C. The presence of other dyes along with the target dye did not negatively affect the adsorption process and RR198 removal efficiency from actual water samples seemed satisfactory and rational. Equilibrium studies confirmed that both Langmuir and Freundlich models described the RR198 adsorption on MZeo/Cellulose nanofiber indicating physical and chemical interactions between the sorbent and RR198 molecules. Kinetic studies demonstrated that pseudo-second-order fitted best with experimental data. Also, thermodynamic studies showed the endothermic nature of the adsorption process. Compared to zeolite, MZeo/Cellulose nanofiber represented a promising removal efficiency for the elimination of RR198 dye from contaminated water.

M, Shahid M, AlDamen MA, Khalid M, Akram M. Cationic dye adsorption and separation at discrete molecular level: first example of an iron cluster with rapid and selective adsorption of methylene blue from aqueous system

A novel Fe₆ cluster was designed as a rare example of any discrete molecule as a highly efficient, selective and rapid functional material for the adsorption of cationic dyes, i.e. methylene blue (MB), from contaminated water bodies.

Characteristics of transmission light in tetracycline hydrochloride polluted wastewater and the response of g-C3N4 under different transmission spectral range during the photodegradation process

The purification efficiency of the contaminants in the process of photocatalysis is influenced by the co-function of catalytic activity of materials, aquatic environment conditions and characteristics of transmission light. Here, tetracycline hydrochloride (TC-HCl) was introduced as the target pollutant, and the effects of different depths and TC-HCl concentrations on the transmission light intensity and spectral distribution were explored. The results show that incident light decreases with the increase of depth and pollutant concentration. The increase of depth influences the irradiance greatly, however, increase of concentration mainly lead to the narrow of transmission spectral range in the underwater field. The coupling relationship among pollutants, transmission spectral characteristics and photocatalytic reaction efficiency was discussed. Results show that the reduction of the underwater spectral range will reduce the effective response area of the material significantly, which directly leads to the reduction of pollutant removal efficiency in the degradation process. Aiming at different aquatic environment, photocatalytic materials with appropriate response spectral range should be selected to improve the light absorption ability, so that the removal efficiency can be improved significantly.

M, Rawat P, Singh RN, Shahid M, Trivedi S, Gautam A, Zeeshan M. A new Zn(ii) MOF assembled from metal–organic cubes (MOCs) as a highly efficient adsorbent for cationic dyes

A new MOC [Zn₃(Tz)₂(tpa)₂(DMSO)₄] was synthesized. The cluster representation reveals an interwoven pcu 6/4/c1 sqc1 topological type. The MOC exhibits excellent water stability, recyclability, adsorption and separation abilities toward selected dyes.