Performance of ionic liquid functionalized metal organic frameworks in the adsorption process of phenol derivatives.

The growth of industrial activities has produced a significant increase in the release of toxic organic pollutants (OPs) to the environment from industrial wastewater. On this premise, this study reports the use of metal organic frameworks (MOFs) impregnated with various ionic liquids (ILs) in the adsorption of phenol derivatives, i.e., 2,6-dimethylphenol and 4,4'-dihydroxybiphenyl. MOFs were prepared starting from 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) with divalent (Co, Ni, Cu) and trivalent (Ce) metal salts in mild hydrothermal conditions using water as a green solvent. Imidazolium base ionic liquids, namely 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium nitrate, 1-butyl-3-methylimidazolium chloride, and 1-hexyl-3-methyl-imidazolium chloride, were used to modify MOFs, leading to composite materials (IL@MOF), which show the structural characteristics of MOFs, and complement the advantages of ILs. SEM, EDX images, and TG data indicate that the IL is just attached on the surface of the adsorbent material, with no changes in crystal size or morphology, but with slightly altered thermal stabilities of IL@MOF composites compared to the original ILs and MOFs, pointing to some interionic interaction between IL and MOF. This research consists of equilibrium experiments, studying the effect of the initial concentration of OPs on the adsorption efficiency of the as-prepared MOFs and IL@MOF, in order to determine the influence of the nature of the adsorbent on its developed adsorption capacity and to investigate the performance of both ILs and MOFs. To determine the maximum adsorption capacity, several empirical isotherms were used: Langmuir, Freundlich, Redlich-Peterson, and Dubinin-Radushkevich. The characteristic parameters for each isotherm and the correlation coefficient (R2) were identified. The IL modification of MOFs increased the adsorption capacity of IL@MOF for the removal of phenol derivatives from aqueous solution. The adsorption capacity function of the MOF structure follows the trend CeHEDP > CoHEDP > NiHEDP > CuHEDP. The best performance was achieved by adsorbent materials based on Ce.

Hybrid Coordination Networks for Removal of Pollutants from Wastewater.

The adsorption properties of two coordination polymers, resulting from the reaction of divalent metal (Ca2+ or Co2+) salts with (2-carboxyethyl)(phenyl)phosphinic acid, are presented in this paper. The structural and textural characterization before and after adsorption experiments is presented. The adsorbent materials were prepared using the hydrothermal procedure. The compound Ca[O2P(CH2CH2COOH)(C6H5)]2 (CaCEPPA) has a layered topology, with the phenyl groups oriented into the interlayer space and crystallizes in the monoclinic system. Compound Co2[(O2P(CH2CH2COO)(C6H5)(H2O)]2·2H2O (CoCEPPA) has a 1D structure composed of zig-zag chains. The adsorption performances of CaCEPPA and CoCEPPA materials were tested in the removal of cadmium and lead from aqueous solutions. The optimum pH of ions adsorption was found to be five for both adsorbent materials. Pseudo-first and second-order kinetic models were used for fitting kinetic experimental data, and Langmuir and Freundlich isotherms were used for modeling the equilibrium experimental data. The pseudo-second-order kinetic model and Langmuir isotherm best described the adsorption of Cd and Pb ions onto the studied materials, judging from the results of the error function (correlation coefficient, sum of square error, chi-square test, and average relative error) analysis. The studied materials present a higher affinity for Cd ions compared with the adsorption capacity developed for the removal of Pb ions from aqueous solutions. CoCEPPA showed the highest adsorption performance in the removal process of metal ions from aqueous solutions compared with CaCEPPA (qm = 54.9 mg Cd2+/g of CoCEPPA, qm = 36.5 mg Cd2+/g of CaCEPPA).

Applications of Metal-Organic Frameworks as Drug Delivery Systems.

In the last decade, metal organic frameworks (MOFs) have shown great prospective as new drug delivery systems (DDSs) due to their unique properties: these materials exhibit fascinating architectures, surfaces, composition, and a rich chemistry of these compounds. The DSSs allow the release of the active pharmaceutical ingredient to accomplish a desired therapeutic response. Over the past few decades, there has been exponential growth of many new classes of coordination polymers, and MOFs have gained popularity over other identified systems due to their higher biocompatibility and versatile loading capabilities. This review presents and assesses the most recent research, findings, and challenges associated with the use of MOFs as DDSs. Among the most commonly used MOFs for investigated-purpose MOFs, coordination polymers and metal complexes based on synthetic and natural polymers, are well known. Specific attention is given to the stimuli- and multistimuli-responsive MOFs-based DDSs. Of great interest in the COVID-19 pandemic is the use of MOFs for combination therapy and multimodal systems.

Chemical Modification of Chitosan for Removal of Pb(II) Ions from Aqueous Solutions.

Biomacromolecule have a significant contribution to the adsorption of metal ions. Moreover, chitosan is one of the most studied biomacromolecule, which has shown a good performance in the field of wastewater treatment. In this context, a new adsorbent of the aminophosphonic modified chitosan-supported Ni(II) ions type was prepared from the naturally biopolymer, chitosan. In the first step, modified chitosan with aminophosphonic acid groups was prepared using the "one-pot" Kabachnik-Fields reaction. It was characterized by different techniques: FTIR, SEM/EDAX, TGA, and 31P-NMR. In the second step, the modified chitosan with aminophosphonic acid was impregnated with Ni(II) ions using the hydrothermal reaction at different values of pH (5, 6 and 7). The physical-chemical characteristics of final products (modified chitosan carrying aminophosphonic groups and Ni(II) ions) were investigated using FTIR, SEM images, EDAX spectra and thermogravimetric analysis. In this work, the most important objective was the investigation of the adsorbent performance of the chitosan modified with aminophosphonic groups and Ni(II) ions in the process of removing Pb(II) ions from aqueous solutions by studying the effect of pH, contact time, and Pb(II) ions concentration. For removal of Pb(II) ions from the aqueous solution, the batch adsorption method was used.

Synthesis and electrochemical properties of metal(ii)-carboxyethylphenylphosphinates.

We report herein the synthesis, structural characterization and electrocatalytic properties of three new coordination polymers, resulting from the combination of divalent metal (Ca2+, Cd2+ or Co2+) salts with (2-carboxyethyl)(phenyl)phosphinic acid. In addition to the usual hydrothermal procedure, the Co2+ derivative could also be prepared by microwave-assisted synthesis, in much shorter times. The crystal structures were solved by ab initio calculations, from powder diffraction data. Compounds MII[O2P(CH2CH2COOH)(C6H5)]2 {M = Cd (1) or Ca (2)} crystallize in the monoclinic system and display a layered topology, with the phenyl groups pointing toward the interlayer space in a interdigitated fashion. Compound Co2[(O2P(CH2CH2COO)(C6H5)(H2O)]2·2H2O (3) presents a 1D structure composed of zig-zag chains, formed by edge-sharing cobalt octahedra, with the phenyl groups pointing outside. Packing of these chains is favored by hydrogen bond interactions via lattice water molecules. In addition, H-bonds along the chains are established with the participation of the water molecules and the hydrophilic groups from the ligand. However, the solid exhibits a low proton conductivity, attributed to the isolation of the hydrophilic regions caused by the arrangement of hydrophobic phenyl groups. Preliminary studies on the electrocatalytic performance for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) have been conducted for compound 3 and its pyrolytic derivatives, which were previously thoroughly characterized. By comparison, another Co2+ phosphinate, 4, obtained by microwave-assisted synthesis, but with distinct stoichiometry and a known structure was also tested. For the OER, the best performance was achieved with a derivative of 3, prepared by heating this compound in N2 at 200 °C. This derivative showed overpotential (339 mV, at a current density of 10 mA cm-2) and Tafel slope (51.7 mV dec-1) values comparable to those of other Co2+ related materials.

New Efficient Adsorbent Materials for the Removal of Cd(II) from Aqueous Solutions.

The rapid increase of industrial activities leads to serious environmental pollution, especially, in aqueous systems and particularly with heavy metals. Cadmium, one of the most poisonous elements, is rapidly accumulated in the human body, therefore, the efficient removal of cadmium ions from wastewater is an urgent need. Coordination networks (CNs) and its subdivision metal-organic frameworks (MOFs), are structured porous composites which present various special properties. In this work two CNs were used as adsorbent materials for the removal of Cd(II) ions from aqueous solutions. By the reaction of CoSO4·7H2O and NiSO4·7H2O with N,N-bis(phosphonomethyl)glycine (Gly) in hydrothermal conditions two CNs-Co-Gly and Ni-Gly- were synthesized, respectively. Cadmium adsorption onto the studied CNs was conducted in batch mode, and the effect of pH, initial concentration, contact time, temperature and sorbent weight on the sorption process were investigated. Parametric Method 3 (PM3)semi-empirical analyses of the CNs' structural properties were performed in order to predict the adsorption properties. For this reason, two octahedral models were calculated and computational predictions were compared with the experimental results. Both computational and experimental adsorption studies found that Ni-Gly presents higher affinity for cadmium ions. Moreover, the adsorbent materials can be readily regenerated and recycled without significant loss of cadmium uptake capacity.

Combined Experimental and Theoretical Insights into the Corrosion Inhibition Activity on Carbon Steel Iron of Phosphonic Acids.

The inhibition effect of N,N'-phosphonomethylglycine (PMG) and vinyl phosphonic acid (VPA) on the 3% NaCl acidic solution corrosion of carbon steel iron was studied at different immersion times by potentiodynamic polarization, electrochemical impedance spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and computational methods. It is found from the polarization studies that PMG and VPA behave as mixed-type inhibitors in NaCl. Values of charge transfer resistance (Rct) and double layer capacitance (Cdl) in the absence and presence of inhibitors are determined. The PMG and VPA inhibitors were capable of inhibiting the corrosion process up to ≈91% and ≈85%, respectively. In the presence of PMG, the synergic effect of chlorine ions was observed. Density functional theory (DFT) was engaged to establish the adsorption site of PMG, VPA, and their deprotonated states. For studied compounds, the resulted values of ELUMO, EHOMO, energy gap (∆E), dipole moment (µ), electronic hardness (η), global softness (σ), electrophilic index (ω), and the electronic potential map are in concordance with the experimental data results regarding their corrosion inhibition behavior and adsorption on the metal surface.

Structure simulation into a lamellar supramolecular network and calculation of the metal ions/ligands ratio.

BACKGROUND: Research interest in phosphonates metal organic frameworks (MOF) has increased extremely in the last two decades, because of theirs fascinating and complex topology and structural flexibility. In this paper we present a mathematical model for ligand/metal ion ratio of an octahedral (Oh) network of cobalt vinylphosphonate (Co(vP)·H2O). RESULTS: A recurrent relationship of the ratio between the number of ligands and the number of metal ions in a lamellar octahedral (Oh) network Co(vP)·H2O, has been deducted by building the 3D network step by step using HyperChem 7.52 package. The mathematical relationship has been validated using X ray analysis, experimental thermogravimetric and elemental analysis data. CONCLUSIONS: Based on deducted recurrence relationship, we can conclude prior to perform X ray analysis, that in the case of a thermogravimetric analysis pointing a ratio between the number of metal ions and ligands number around 1, the 3D network will have a central metal ion that corresponds to a single ligand. This relation is valid for every type of supramolecular network with divalent metal central ion Oh coordinated and bring valuable information with low effort and cost.

Divalent metal vinylphosphonate layered materials: compositional variability, structural peculiarities, dehydration behavior, and photoluminescent properties.

A family of M-VP (M = Ni, Co, Cd, Mn, Zn, Fe, Cu, Pb; VP = vinylphosphonate) and M-PVP (M = Co, Cd; PVP = phenylvinylphosphonate) materials have been synthesized by hydrothermal methods and characterized by FT-IR, elemental analysis, and thermogravimetric analysis (TGA). Their structures were determined either by single crystal X-ray crystallography or from laboratory X-ray powder diffraction data. The crystal structure of some M-VP and M-PVP materials is two-dimensional (2D) layered, with the organic groups (vinyl or phenylvinyl) protruding into the interlamellar space. However, the Pb-VP and Cu-VP materials show dramatically different structural features. The porous, three-dimensional (3D) structure of Pb-VP contains the Pb center in a pentagonal pyramid. A Cu-VP variant of the common 2D layered structure shows a very peculiar structure. The structure of the material is 2D with the layers based upon three crystallographically distinct Cu atoms; an octahedrally coordinated Cu(2+) atom, a square planar Cu(2+) atom and a Cu(+) atom. The latter has an unusual co-ordination environment as it is 3-coordinated to two oxygen atoms with the third bond across the double bond of the vinyl group. Metal-coordinated water loss was studied by TGA and thermodiffractometry. The rehydration of the anhydrous phases to give the initial phase takes place rapidly for Cd-PVP but it takes several days for Co-PVP. The M-VP materials exhibit variable dehydration-rehydration behavior, with most of them losing crystallinity during the process.