A Microporous Anionic Metal-Organic Framework for Sensing Luminescence of Lanthanide(III) Ions and Selective Absorption of Dyes by Ionic Exchange

High-Performance enrichment and sensitive analysis of bisphenol and its analogues in water and milk using a novel Ni-Based cationic Metal-Organic framework

A novel cationic metal-organic framework (iMOF-Ni) was designed and synthesized by a solvothermal method. It was fabricated as a solid-phase extraction (SPE) cartridge and exhibited high adsorption performance for Bisphenols (BPs). The theoretical simulation demonstrated that the adsorption mechanism between iMOF-Ni and BPs was attributed to cation-π bonding, π-π interaction, and electrostatic interactions. Under optimized SPE, a method for analyzing BPs was established by combining high-performance liquid chromatography-diode array detection (HPLC-DAD). The developed method has good linearity (R2 ≥ 0.994), low detection limits (0.07-0.16 ng/mL), and good reproducibility (1.72-6.35 %, n = 6). The applicability of the method was further evaluated by analyzing water and milk samples. Recoveries of four BPs in spiked samples were from 72.2 % to 96.6 %.

Ionic metal-organic frameworks (iMOFs): progress and prospects as ionic functional materials

Metal-organic frameworks (MOFs) have been a research hotspot for the last two decades, witnessing an extraordinary upsurge across various domains in materials chemistry. Ionic MOFs (both anionic and cationic MOFs) have emerged as next-generation ionic functional materials and are an important subclass of MOFs owing to their ability to generate strong electrostatic interactions between their charged framework and guest molecules. Furthermore, the presence of extra-framework counter-ions in their confined nanospaces can serve as additional functionality in these materials, which endows them a significant advantage in specific host-guest interactions and ion-exchange-based applications. In the present review, we summarize the progress and future prospects of iMOFs both in terms of fundamental developments and potential applications. Furthermore, the design principles of ionic MOFs and their state-of-the-art ion exchange performances are discussed in detail and the future perspectives of these promising ionic materials are proposed.

From a Dense Structure to Open Frameworks: The Structural Plethora of Alkali Metal Iron Fluorophosphates

By employing the pyridinium hexafluorophosphate task-specific ionic liquids 1-butyl-4-methylpyridinium hexafluorophosphate ([C₄mpyr][PF₆]) and 1-ethylpyridinium hexafluorophosphate ([C₂pyr][PF₆]) as the reaction medium, mineralizer, structure-directing agent, and, in the case of the smaller pyridinium cation, even a structural component, it was possible to obtain five new alkali metal iron phosphates featuring interconnected FeX₆ octahedra and PX₄ (X = F, O, or OH) tetrahedra. NaFe(PO₃F)₂ (1) is a dense 3D structure, RbFe(PO₃F)(PO₂(OH)F)(PO₂(OH)₂) (2) features 1D strands, (C₂pyr)LiFe(PO₃F)₃(PO₂F₂)F (3) has 2D layers, and LiFe(PO₃F)(PO₂F₂)F (4) as well as Cs_0.75Fe(PO_2.75(OH)_0.25F)(PO₂F₂)₂ (5) are 3D open frameworks. While in 1–2 as well as in 4 and 5, FeX₆ octahedra and PX₄ (X = F, O, or OH) tetrahedra alternate, 3 features octahedra dimers, Fe₂X₁₁ (X = F, O, or OH). The magnetic behavior of all compounds is governed by antiferromagnetic interactions. Interestingly, 3 exhibits a broad maximum in the temperature dependence of the magnetic susceptibility, characteristic of a low-dimensional magnetic system consistent with the presence of Fe–Fe dimers in its crystal structure.

Application of ionic liquids as the reaction medium, structure templates, and mineralizer led to a series of active-metal-iron phosphates with structural motifs of varied dimensionality and, ultimately, an open-framework structure.

Two Coordination Polymers Synthesized from Various N-Donor Clusters Spaced by Terephthalic Acid for Efficient Photocatalytic Degradation of Ibuprofen in Water under Solar and Artificial Irradiation

Two coordination polymers CP1 {[Zn(II)(BIPY)(Pht)] _n } and CP2 {[Zn(HYD)(Pht)] _n } (BIPY = 4,4'-bipyridine, Pht = terephthalic acid, and HYD = 8-hydroxyquinoline) have been successfully synthesized by a hydrothermal process using zinc aqueous solution. The so-prepared compounds were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-visible spectroscopy, thermogravimetric analysis (TGA), and cyclic voltammetry. XRD pointed to a crystalline phase for CP1, while CP2 required recrystallization, FTIR spectroscopy established the presence of characteristic bands for all the ligands, and TGA showed thermal stability up to 100 °C. The electrochemical study showed a good charge transfer between the ligands and Zn metal for both materials. The UV-vis spectra displayed a strong absorption band spreading over a wide wavelength range, encompassing UV and visible light, with a band gap of 2.69 eV for CP1 and 2.56 eV for CP2, both of which are smaller than that of ZnO. This provides an advantageous alternative to using ZnO. The 5 × 10^-5 mol L^-1 ibuprofen decomposition kinetics under solar and UV light were studied under different irradiation conditions. Good photocatalytic properties were observed due to their high surface area.

Mixed-Linker Strategy for the Construction of Metal-Organic Framework Combined with Dyes toward Alcohol Detection

Herein, a N-rich metal-organic framework (MOF) with four kinds of cages, Zn₄(ade)₂(TCA)₂(H₂O) (NENU-1000, Hade = adenine, H₃TCA = 4,4',4″-tricarboxytriphenylamine, NENU = Northeast Normal University), was prepared by the mixed-ligand strategy. Cationic dyes can be selectively absorbed by NENU-1000 at proper concentrations, but not neutral and anionic dyes, which perhaps can be assigned to the N-rich neutral framework of NENU-1000. When NENU-1000 was introduced to a relatively lower concentration of cationic dye solutions (e.g., rhodamine B or basic red 2), the colors of these systems faded quickly. Furthermore, the faded solutions can be used for the detection of methanol and other small alcohol molecules with either the naked eye or common UV-vis spectra. The effect of the length of carbon chain, the position of the -OH group, and the number of the hydroxyl group of the alcohols was explored for the color development rate. In addition, the performance of NENU-1000 in iodine sorption and release was also studied.

A microporous anionic metal–organic framework for aqueous encapsulation and highly reversible sensitization of light-emitting Tb3+ ions

An anionic porous material can serve as both a host and an antenna for protecting and sensitizing extra-framework light-emitting Eu3+/Tb3+ ions. The Tb3+ uptake and release is a reversible process and the cationic Tb3+ can be gradually released.

Two mesoporous anionic metal-organic frameworks for selective and efficient adsorption of a cationic organic dye

Anionic metal-organic frameworks (MOFs) are beginning to have a great impact in the field of absorption and separation of ionic organic molecules due to the enhanced electrostatic interactions between their anionic frameworks and counter-ionic guests. Herein, the rational design and synthesis of two mesoporous anionic MOFs, [Zn₃(ITTC)₃](Me₂ NH₂)₃·3DMF·H₂O (1) and [Cd₂(ITTC)₃](Me₂NH₂)₅·2DMF (2), where H₃ITTC = 4,4',4''-(1H-imidazole-2,4,5-triyl) tribenzoic acid, is reported. Structural analysis revealed that both materials are anionic MOFs with a 2-fold interpenetrating three dimensional (3D) framework. The cross sectional area of the open one-dimensional rectangular channels is 31.7 Å × 15.6 Å for 1, of which the architecture is indicative of an unprecedented (3,3,4,5)-connection topology. For 2, the diameter of the open one-dimensional regular hexagonal channel is about 34.1 Å, decorated with uncoordinated carboxyl O atoms, and the framework exhibits a (3,4)-connected fcu network. Due to their anionic frameworks and bulky pore window sizes, both MOFs can be employed for absorbing and separating the cationic organic dye methylene blue (MB). The results reveal that both MOFs have better dye adsorption selectivity for MB, than for MO and SDI, because of charge and size-matching effects, enabling them to be potential candidates for use in environmental cleaning. By comparison, 2 presents superior selectivity and adsorptivity for cationic MB which depends on the presence of a basic functionalized pore surface.

Lanthanide-Aromatic Iminodiacetate Frameworks with Helical Tubes: Structure, Properties, and Low-Temperature Heat Capacity

A series of lanthanide coordination polymers [LnL(H₂O)₂] _n [Ln = Pr (1), Nd (2), Sm (3), Eu (4), and Gd (5), H₃L = N-(4-carboxy-benzyl)iminodiacetic acid] was hydrothermally prepared and structurally characterized. All the five compounds have been confirmed as 3D Ln-CPs with one-dimensional helical tunnels composed of four helical chains, although there are different coordination geometries around Ln³⁺. Enantiomeric helixes in 1-3, and absolute left-handed and right-handed helical chains in 4 and 5, respectively, lead to different tunnel spaces. Their conformations can also be featured by different space groups and unit cell dimensions. Photoluminescence measurement on 3 and 4 show characteristic emission peaks of Sm³⁺ and Eu³⁺ ions, respectively. The low-temperature heat capacity of 1-4 has been investigated in the temperature range of 1.9-300 K. Their heat capacity values are nearly equal below 10 K and display a crossover with the value order C _p,m(2) > C _p,m(1) ≈ C _p,m(4) > C _p,m(3) above 10 K. The measured heat capacities have been fitted, and the corresponding thermodynamic functions were consequently calculated based on the fitting parameters. The standard molar entropies at 298.15 K have been determined to be (415.71 ± 4.16), (451.32 ± 4.51), (308.53 ± 3.09), and (407.62 ± 4.08) J·mol^-1·K^-1 for 1, 2, 3, and 4, respectively.

Defective Hierarchical Pore Engineering of a Zn-Ni MOF by Labile Coordination Bonding Modulation

The construction and modulation of hierarchical pore structure in metal-organic frameworks (MOFs) has become a hot topic owing to the advantages of hierarchical pore MOFs (HP-MOFs) in matter storage and mass transfer related applications. Herein, we report the engineering of crystalline defect in a bimetallic MOF for the construction and tuning of HP-MOF. A microporous MOF system showing metal-center-dependent water stability, namely, {[M₃F(bdc)₃ tpt] (solvents)}_n (M = Zn²⁺ and Ni²⁺, H₂bdc = 1,4-benzenedicarboxylic acid, tpt = 2,4,6-tris(4-pyridyl)triazine), was utilized as a platform for the construction of HP-MOF. By tuning the Zn²⁺/Ni²⁺ ratio in the reactant, a bimetallic MOF with a highly tunable Zn²⁺/Ni²⁺ ratio could be obtained. The relatively labile Zn²⁺-based coordination bonding in the bimetallic MOF could be readily and targeted broken through water treatment for the engineering of crystalline defects-based hierarchical pore structure. The resultant HP-MOF reveals a dramatically increased pore volume with the presence of mesopore and macropore. In addition, the anionic framework of HP-MOF could be utilized for the selective adsorption of a cationic dye methylene blue, and a relatively high capacity (250 mg·g^-1, five times compared with the pristine microporous MOF) could be achieved.

A porous anionic zinc(ii) metal–organic framework for gas adsorption, selective uptake of dyes and sensing of Fe3+ by Tb3+ ion encapsulation

A 3D anionic, porous MOF exhibits selective adsorption of cationic dyes and can be used as a fast-response fluorescence sensor for the detection of Fe3+ ions by Tb3+ ion encapsulation.

Self-assembly and photocatalytic property of a new inorganic-organic hybrid material based on 1,4-bis(4-pyridylthio)butane

A new hybrid compound consisting of 1,4-bis(4-pyridylthio)butane ([Bpytb]) ligand, namely {[Bpytb]Ag2I3}n (1), has been prepared and characterized by IR spectroscopy, solid UV-visible diffuse reflectance spectrum, X-ray Powder Diffraction (PXRD) and TG. Compound 1 consists of 1D anion chain structure. Crystal system: Monoclinic, Space group: P2/c, a = 4.5092(3), b = 11.1895(9), c = 21.3893(14), α= 90°, β= 92.907(2)°, γ= 90°, V = 1077.82(13) Å3, Z = 2, Dcalc = 2.693 g cm–3. The photocatalytic property of compound 1 was also studied and it exhibits a better degradation effect on organic dye MB.

Selective Adsorption of Cationic Dyes for Stable Metal-Organic Framework ZJU-48

A cationic metal-organic framework (MOF) ZJU-48 with one-dimensional pores of about 9.1 × 9.1 Ų has been prepared from zinc ions, adenine, and carboxyl ligands. ZJU-48 displays excellent water stability for about one week, exhibiting its potential application for adsorption and separation of dyes. Cationic and anionic dyes with similar sizes are adopted to study the adsorbing and separating properties of ZJU-48. Cationic dyes are adsorbed better than anionic dyes because of the negatively charged zeta potential of the material surface, implying its selective adsorption to cationic dyes, and it is charge-based adsorption. Meanwhile, the adsorption ability of the MOF to cationic dyes with different sizes is also investigated. We find that the adsorbed amount decreases with increase in the size of organics ,indicating that it is size-based adsorption. Furthermore, the cationic dye methylene blue (MB) is employed and focused on for its suitable charge and fitting size to evaluate the maximum adsorption capacity and desorption progress of ZJU-48. The results show that the maximum loaded amount of MOF toward MB reaches 582.44 mg/g, and about 90% of loaded dyes can be released from frameworks in N,N-dimethylformamide with NaCl over 6 h, exhibiting satisfactory adsorptive property and possibility as a reusable adsorbent.

Two-Dimensional Materials and Composites as Potential Water Splitting Photocatalysts: A Review

Hydrogen production via water dissociation under exposure to sunlight has emanated as an environmentally friendly, highly productive and expedient process to overcome the energy production and consumption gap, while evading the challenges of fossil fuel depletion and ecological contamination. Various classes of materials are being explored as viable photocatalysts to achieve this purpose, among which, the two-dimensional materials have emerged as prominent candidates, having the intrinsic advantages of visible light sensitivity; structural and chemical tuneability; extensively exposed surface area; and flexibility to form composites and heterostructures. In an abridged manner, the common types of 2D photocatalysts, their position as potential contenders in photocatalytic processes, their derivatives and their modifications are described herein, as it all applies to achieving the coveted chemical and physical properties by fine-tuning the synthesis techniques, precursor ingredients and nano-structural alterations.

Cr2O72− inside Zr/Hf-based metal–organic frameworks: highly sensitive and selective detection and crystallographic evidence

The (4,8)-connected Zr/Hf-MOFs exhibit excellent performances in the detection of Cr₂O₇²⁻ and the exact location and configuration of Cr₂O₇²⁻ inside the MOFs were revealed by single-crystal X-ray diffraction studies for the first time.

Metal–organic frameworks as acid- and/or base-functionalized catalysts for tandem reactions

In this article, we have reviewed the development of MOFs anchored with acidic and/or basic sites as heterogeneous catalysts for tandem/cascade (domino) reactions over the past five years.

Mixed-Metal MOFs: Unique Opportunities in Metal-Organic Framework (MOF) Functionality and Design

Mixed-metal metal-organic frameworks (MM-MOFs) can be considered to be those MOFs having two different metals anywhere in the structure. Herein we summarize the various strategies for the preparation of MM-MOFs and some of their applications in adsorption, gas separation, and catalysis. It is shown that compared to homometallic MOFs, MM-MOFs bring about the opportunity to take advantage of the complexity and the synergism derived from the presence of different metal ions in the structure of MOFs. This is reflected in a superior performance and even stability of MM-MOFs respect to related single-metal MOFs. Emphasis is made on the use of MM-MOFs as catalysts for tandem reactions.

Assembly and Adsorption Properties of Seven Supramolecular Compounds with Heteromacrocycle Imidazolium

Seven supramolecular compounds comprising multivalent imidazolium macrocycles and metal halides, {[MC-IM][Ag₂I₄]} _n (1), {[PC-IM]₂[Ag₇I₁₁]} _n (2), {[ODC-IM][Ag₃I₇]} (3), {[ODC-IM][Bi₂I₁₀]} (4), {[MDC-IM][Bi₂I₁₀]} (5), {[PDC-IM][Bi₂I₁₀]} (6), and {[MDC-IM][HgI₄]} (7), have been synthesized by solvothermal reactions and structurally characterized by IR spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. Notably, the three tetravalent imidazolium macrocycles were introduced for the first time and the extended anion structures are featured with three-dimensional coordination networks, one-dimensional chains, or zero-dimensional oligomers. This new study attempts to not only fill the gap in this supramolecular hybrid area that has been neglected but also enrich the type of imidazolium cyclophane. It is important that good efforts were devoted to study the adsorption properties of supramolecular compounds. Compound 5 exhibited great adsorption performance for organic dyes methylene blue, methyl orange, and rhodamine B (RhB) and can be evaluated as a potential candidate for industrial wastewater treatment.

Amino functionalized Zn/Cd-metal-organic frameworks for selective CO2 adsorption and Knoevenagel condensation reactions

Two amino functionalized Metal-Organic Frameworks (MOFs), {[Zn(Py2TTz)(2-NH2-BDC)]·(DMF)}n (1) and {[Cd(Py2TTz)(2-NH2-BDC)]·(DMF)·0.5(H2O)}n (2) (where Py2TTz = 2,5-bis(4-pyridyl)thiazolo[5,4-d]thiazole, 2-NH2-BDC = 2-amino-1,4-benzenedicarboxylate, and DMF = N,N-dimethylformamide), were synthesized and characterized using the primary ligand 2-amino-1,4-benzenedicarboxylic acid (2-NH2-H2BDC) and the auxiliary ligand 2,5-bis(4-pyridyl)thiazolo[5,4-d]thiazole (Py2TTz). They possess similar 2-fold interpenetrated three-dimensional bipillared-layer framework structures composed of typical binuclear metal nodes, 2-NH2-BDC two-dimensional layers and Py2TTz bipillars. Notably, thiazole nitrogen atoms and pendant -NH2 groups are present in channels in the two frameworks. Given their good chemical stabilities, high thermal stabilities, and exposed nitrogen sites, gas adsorption and catalytic experiments of the two MOFs were performed. The results demonstrate that MOF 2 can selectively adsorb carbon dioxide gas; moreover, the two MOFs can be employed as recyclable heterogeneous catalysts for Knoevenagel condensation reactions under solvent-free conditions.

Two metal–organic zeolites for highly sensitive and selective sensing of Tb3+

Two metal–organic zeolites can sensitize the luminescence of the Tb³⁺ ion by energy transfer between the host frameworks and the guest Tb³⁺ ion, thus serving as Tb³⁺ ion sensors.

Selective CO2 adsorption and theoretical simulation of a stable Co(ii)-based metal–organic framework with tunable crystal size

A stable Co(ii)-MOF shows selective CO₂ adsorption and high H₂ uptake. The simulations of sorption confirm this reasonable design approach.

A series of flexible bis(pyridyl)bis(tetrazole)-modulated coordination polymers: construction, electrochemical properties, dye adsorption and magnetic properties

Four new coordination polymers based on three bis(pyridyl)bis(tetrazole) ligands and 4,4′,4′′-benzene-1,3,5-triyltribenzoic acid were synthesized showing electrocatalytic, dye adsorption and antiferromagnetism properties.

Fabrication of a dual-emitting dye-encapsulated metal–organic framework as a stable fluorescent sensor for metal ion detection

The encapsulation of fluorescein dye into porous zinc–adenine metal–organic framework (bio-MOF-1) crystals has been studied for metal cation sensing.

Ultra-highly selective trapping of perrhenate/pertechnetate by a flexible cationic coordination framework

This work presents a 3D cationic coordination framework, showing ultra-highly selective trapping of perrhenate/pertechnetate in the presence of sulfate 20 000 times in excess.

Crystal structure of poly-{diaqua-bis[(μ2-3-nitrobenzenesulfonylglycine-κ3 N:O:O′)(4,4′-bipyridine)manganese(II)]}-dimethylformamide (1/1), C39H35Mn2N9O15S2

C39H35Mn2N9O15S2, orthorhombic, Pna21 (no. 33), a = 17.2427(6) Å, b = 11.7453(3) Å, c = 21.1828(7) Å, V = 4290.0(2) Å3, Z = 4, R gt(F) = 0.0366, wR ref(F 2) = 0.0960, T = 293(2) K.

Influence of different metal ions on the assembly, structures, and properties of two complexes based on the semi-rigid bis(pyridyl)-bis(amide) ligand and 4,4′-oxybis(benzoic acid)

Two transitional metal complexes, [Zn(oba)(3-bpcd)] n (1) and [Cd(oba)(3-bpcd)0.5] n (2) [H2oba= 4,4′-oxybis(benzoic acid), 3-bpcd=N,N′-bis(pyridin-3-yl)cyclohexane-1,4-dicarboxamide], have been hydrothermally synthesized and structurally characterized by elemental analyses, infrared spectra, powder X-ray diffraction, thermogravimetric and single-crystal X-ray diffraction. Complex 1 possesses a three-fold interpenetrating network based on layers with a 4-connected sql topology. Complex 2 is a layered framework constructed by the oba anions and 3-bpcd ligands, which represents a binodal (3,4)-connected {62.10}{6} topology. The adjacent layers of complex 2 are further linked by hydrogen bonding interactions to build a three-dimensional supramolecular architecture. The differences of metal ions in coordination modes show a significant effect on the final structures of the Zn(II)/Cd(II) complexes. The photocatalytic activities and the fluorescence sensing properties of complexes 1 and 2 were investigated.

Recent advancements in bioremediation of dye: Current status and challenges

The rampant industrialization and unchecked growth of modern textile production facilities coupled with the lack of proper treatment facilities have proliferated the discharge of effluents enriched with toxic, baleful, and carcinogenic pollutants including dyes, heavy metals, volatile organic compounds, odorants, and other hazardous materials. Therefore, the development of cost-effective and efficient control measures against such pollution is imperative to safeguard ecosystems and natural resources. In this regard, recent advances in biotechnology and microbiology have propelled bioremediation as a prospective alternative to traditional treatment methods. This review was organized to address bioremediation as a practical option for the treatment of dyes by evaluating its performance and typical attributes. It further highlights the current hurdles and future prospects for the abatement of dyes via biotechnology-based remediation techniques.

Temperature-induced self-assembly of two kinds Zn(ii)-based coordination polymers with luminescence properties for application in sensing and adsorption

Temperature-induced self-assembly of coordination polymers (CPs) is of great importance for structural tunability and is quite necessary for further research on structure–property relationships.

Synthesis of nanoporous cobalt/carbon materials by a carbonized zeolitic imidazolate framework-9 and adsorption of dyes

The cobalt/carbon material Z9-600 exhibits a high adsorption capacity for methylene green and a high regeneration efficiency after 4 cycles of use and reuse.

An anionic single-walled metal–organic nanotube with an armchair (3,3) topology as an extremely smart adsorbent for the effective and selective adsorption of cationic carcinogenic dyes

A novel discrete single-walled MONT with a rare armchair (3,3) CNT topology and mesoporous channels is synthesized, which exhibits exclusive and remarkable ability to adsorb cationic carcinogens BR9 and BV14.