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.

Recent developments in MOF and MOF based composite as potential adsorbents for removal of aqueous environmental contaminants

With the growth of globalization which has been the primary cause of water pollution, it is utmost necessary for us living being to have access to clean water for the purpose of drinking, washing and various other useful applications. With the purpose of future security and to restore our ecological balance, it is essential to give much significance towards the removal of unwanted toxic contaminants from our water resources. In this regard adsorptive removal of toxic pollutants from wastewater with porous adsorbent is regarded as one of the most promising way for water decontamination process. Metal organic frameworks (MOFs) comprising of uniformly arranged pores, abundant active sites and containing an easily tunable structure has aroused as a promising material for adsorbent to remove the unwanted contaminants from water sources. The adsorption of pollutants by the different MOFs surface are driven by various interactions including π-π, acid-base, electrostatic and H-bonding etc. On the other hand, the removal of various contaminants by MOFs is influenced by various factors including pH, temperature and initial concentration. In this review we will specifically discuss the adsorptive removal of different organic and inorganic pollutants present in our water systems with the use of MOFs as adsorbent along with the various factors and interaction mechanism manipulating the adsorption behaviour.

Metal-Organic Frameworks for Liquid Phase Applications

In the last two decades, metal-organic frameworks (MOFs) have attracted overwhelming attention. With readily tunable structures and functionalities, MOFs offer an unprecedentedly vast degree of design flexibility from enormous number of inorganic and organic building blocks or via postsynthetic modification to produce functional nanoporous materials. A large extent of experimental and computational studies of MOFs have been focused on gas phase applications, particularly the storage of low-carbon footprint energy carriers and the separation of CO2-containing gas mixtures. With progressive success in the synthesis of water- and solvent-resistant MOFs over the past several years, the increasingly active exploration of MOFs has been witnessed for widespread liquid phase applications such as liquid fuel purification, aromatics separation, water treatment, solvent recovery, chemical sensing, chiral separation, drug delivery, biomolecule encapsulation and separation. At this juncture, the recent experimental and computational studies are summarized herein for these multifaceted liquid phase applications to demonstrate the rapid advance in this burgeoning field. The challenges and opportunities moving from laboratory scale towards practical applications are discussed.

3D semiconducting Co–MOFs based on 5-(hydroxymethyl)isophthalic acid and imidazole derivatives: syntheses and crystal structures

Two three-dimensional cobalt-based metal–organic frameworks with 5-(hydroxymethyl)isophthalic acid (H2HIPA), namely poly[[μ2-1,4-bis(2-methyl-1H-imidazol-1-yl)benzene-κ2 N 3:N 3′][μ2-5-(hydroxymethyl)isophthalato-κ2 O 1:O 3]cobalt(II)], [Co(C9H6O5)(C14H14N4)] n (1), and poly[tris[μ2-1,4-bis(1H-imidazol-1-yl)benzene-κ2 N 3:N 3′]bis[μ3-5-(hydroxymethyl)isophthalato-κ2 O 1:O 3:O 5]dicobalt(II)], [Co2(C9H6O5)2(C12H10N4)3] n (2), were synthesized under similar hydrothermal conditions. Single-crystal X-ray diffraction analyses revealed that 5-(hydroxymethyl)isophthalate (HIPA2−) and 1,4-bis(2-methyl-1H-imidazol-1-yl)benzene (1,4-BMIB) are simple linkers connecting cobalt centres to build a fourfold interpenetration dia framework in complex 1. However, complex 2 is a pillared-layer framework with a (3,6)-connected network constructed by 1,4-bis(1H-imidazol-1-yl)benzene (1,4-DIB) linkers, 3-connected HIPA2− ligands and 6-connected CoII centres. The above significant structural differences can be ascribed to the introduction of the different auxiliary N-donor ligands. Moreover, UV–Vis spectroscopy and Mott–Schottky measurements confirmed that complexes 1 and 2 are typical n-type semiconductors.

Binary mixed molybdenum cobalt sulfide nanosheets decorated on rGO as a high-performance supercapacitor electrode

This work represents the production of MoS₂/CoS₂ hybridized with rGO as a material for high-performance supercapacitors. The hydrothermal method is used for the synthesis. The as-prepared material is characterized by x-ray diffraction spectroscopy, x-ray photoelectron spectroscopy, and electron microscopy. The size of the nanoparticles is estimated at 80 nm, and their uniform dispersion on rGO is observed from electron microscopy images. A high-specific capacitance of 190 mF cm^-2 obtains for MoS₂/CoS₂/rGO at the current density of 0.5 mA cm^-2 in 2 M KOH. The cyclic stability over 5000 cycles at a scan rate of 100 mV s^-1 shows that the MoS₂/CoS₂/rGO electrode is stable, and 88.6% of its initial capacitance sustains at the end of 5000 cycles. This excellent performance is assigned to the synergistic effect of rGO and MoS₂/CoS₂. This electrode with excellent stability and capacitance could be a potential candidate for supercapacitor electrode materials.

MOF-Polymer Hybrid Materials: From Simple Composites to Tailored Architectures

Metal-organic frameworks (MOFs) are inherently crystalline, brittle porous solids. Conversely, polymers are flexible, malleable, and processable solids that are used for a broad range of commonly used technologies. The stark differences between the nature of MOFs and polymers has motivated efforts to hybridize crystalline MOFs and flexible polymers to produce composites that retain the desired properties of these disparate materials. Importantly, studies have shown that MOFs can be used to influence polymer structure, and polymers can be used to modulate MOF growth and characteristics. In this Review, we highlight the development and recent advances in the synthesis of MOF-polymer mixed-matrix membranes (MMMs) and applications of these MMMs in gas and liquid separations and purifications, including aqueous applications such as dye removal, toxic heavy metal sequestration, and desalination. Other elegant ways of synthesizing MOF-polymer hybrid materials, such as grafting polymers to and from MOFs, polymerization of polymers within MOFs, using polymers to template MOFs, and the bottom-up synthesis of polyMOFs and polyMOPs are also discussed. This review highlights recent papers in the advancement of MOF-polymer hybrid materials, as well as seminal reports that significantly advanced the field.

A water-stable 3D Eu-MOF based on a metallacyclodimeric secondary building unit for sensitive fluorescent detection of acetone molecules

A Eu-MOF with high water stability constructed using a systematic metallacyclodimeric motif as a potential chemical sensor for acetone is reported.

A pillar-layer strategy to construct 2D polycatenated coordination polymers for luminescence detection of Cr2O72− and CrO42− in aqueous solution

Six polycatenated coordination polymers 1–6 based on the pillar-layer strategy have been designed and synthesized. Compound 6 exhibited strong fluorescence that was selectively quenched by Cr^VI ions in aqueous solution at low concentrations.

A Zn(ii) metal–organic framework constructed by a mixed-ligand strategy for CO2 capture and gas separation

A microporous Zn(ii) metal–organic framework has been assembled using a mixed-ligand strategy, and it exhibits high capture ability for CO₂ and good selectivity for CO₂/CH₄, C₂H₆/CH₄ and C₃H₈/CH₄.

From 2D → 3D interpenetration to packing: N coligand-driven structural assembly and tuning of luminescent sensing activities towards Fe3+ and Cr2O72− ions

Three complexes were hydrothermally synthesized and exhibited excellent selectivity towards Fe³⁺ and Cr₂O₇²⁻.

Structure modulation from unstable to stable MOFs by regulating secondary N-donor ligands

Four new Cd/Zn(ii) MOFs have been synthesized and structurally modulated from unstable to stable by regulating secondary N-donor ligands. Furthermore, YZ-10 shows excellent CO₂ selective uptake over CH₄ and N₂ and uncommon H₂ selective uptake over N₂ at 77 K.

High-Efficiency Co/CoxSy@S,N-Codoped Porous Carbon Electrocatalysts Fabricated from Controllably Grown Sulfur- and Nitrogen-Including Cobalt-Based MOFs for Rechargeable Zinc-Air Batteries

Developing bifunctional oxygen electrocatalysts with superior catalytic activities of oxygen reduction reaction (ORR) and oxygen revolution reaction (OER) is crucial to their practical energy storage and conversion applications. In this work, we report the fabrication of Co/Co_xS_y@S,N-codoped porous carbon structures with various morphologies, specific surface areas, and pore structures, derived from controllably grown Co-based metal-organic frameworks with S- and N-containing organic ligands (thiophene-2,5-dicarboxylate, Tdc; and 4,4'-bipyridine, bpy) utilizing solvent effect (e.g., water and methanol) under room temperature and hydrothermal conditions. The results demonstrate that Co/Co_xS_y@S,N-codoped carbon fibers fabricated at a pyrolytic temperature of 800 °C (Co/Co_xS_y@SNCF-800) from Co-MOFs fibers fabricated in methanol under hydrothermal conditions as electrocatalysts exhibit superior bifunctional ORR and OER activities in alkaline media, endowing them as air cathodic catalysts in rechargeable zinc-air batteries with high power density and good durability.

Facile synthesis of MOFs with uncoordinated carboxyl groups for selective CO2 capture via postsynthetic covalent modification

A facile strategy involving dual-acyl chloride has been developed to introduce uncoordinated carboxyl groups into amine containing metal–organic frameworks.

Crystal structure of catena-poly-{aqua-[μ2-1,2-bis((1H-imidazol-1-yl)methyl)benzene-κ2N:N′]-[μ2-4,4′-(dimethylsilanediyl)dibenzato-κ3O,O′:O′]nickel(II)}, C30H30N4NiO5Si

C30H30N4NiO5Si, triclinic, P1̅ (no. 2), a = 8.6296(4) Å, b = 12.9969(6) Å, c = 14.8944(6) Å, α = 114.8630(10)°, β = 90.8960(10)°, γ = 105.3700(10)°, V = 1445.98(11) Å3, Z = 2, Rgt(F) = 0.0272, wRref(F2) = 0.0735, T = 293 K.

A luminescent metal organic framework with high sensitivity for detecting and removing copper ions from simulated biological fluids

Cd-MOF-74shows high sensitivity and efficiency in the detection and removal of copper ions from water and simulated biological fluids.

Crystal structure of poly-{[μ2-(E)-1,4-di(1H-imidazol-1-yl)but-2-ene-κ2N:N′][μ2-cyclohexane-1,4-dicarboxylato-κ4O,O′:O′′,O′′′]nickel(II)}, C18H22N4NiO4

C18H22N4NiO4, orthorhombic, Pna21 (no. 33), a = 8.9924(5) Å, b = 17.1818(10) Å, c = 12.1009(7) Å, V = 1869.66(19) Å3, Z = 4, Rgt(F) = 0.0328, wRref(F2) = 0.0798, T = 293 K.

Crystal structure of poly-[bis{μ2-N-(4-(1H-imidazol-1-yl)phenyl)-4-(1H-imidazol-1-yl)-N-phenylaniline-κ2N:N′)}-(μ2-naphthalene-2,6-dicarboxylato)-(μ4-naphthalene-2,6-dicarboxylato)dicadmium(II)], C36H25N5O4Cd

C36H25N5O4Cd, monoclinic, P1̅ (No. 2), a = 9.708(5) Å, b = 10.954(5) Å, c = 15.014(5) Å, α = 97.858(5)°, β = 98.584(5)°, γ = 104.798(5)°, V = 1500.6(11) Å3, Z = 2, Rgt(F) = 0.0297, wRref(F2) = 0.0904, T = 293(2) K.

Crystal structure of dichlorido{bis(2-hydroxyethyl)-5′-([2,2′:6′,2′′-terpyridin]-4′-yl)-[1,1′:3′,1′′-terphenyl]-4,4′′-dicarboxylate-κ3N,N′,N′′}zinc(II), C39H31Cl2N3O6Zn

C39H31Cl2N3O6Zn, monoclinic, C2/c (no. 15), a = 20.7170(16) Å, b = 14.4553(11) Å, c = 11.2717(8) Å, β = 90.072(2)°, V = 3375.5(4) Å3, Z = 4, Rgt(F) = 0.0489, wRref(F2) = 0.1469, T = 293(2) K.

Turn-on and Ratiometric Luminescent Sensing of Hydrogen Sulfide Based on Metal-Organic Frameworks

The sensing of hydrogen sulfide (H₂S) has become a long-time challenging task. In this work, we developed a general strategy for sensing of H₂S utilizing postsynthetic modification of a nano metal-organic frameworks (MOF) UiO-66-(COOH)₂ with Eu³⁺ and Cu²⁺ ions. The nano MOF Eu³⁺/Cu²⁺@UiO-66-(COOH)₂ displays the characteristic Eu³⁺ sharp emissions and the broad ligand-centered (LC) emission simultaneously. Because H₂S can strongly increase the fluorescence of Eu³⁺ and quench the broad LC emission through its superior affinity for Cu²⁺ ions, the MOF Eu³⁺/Cu²⁺@UiO-66-(COOH)₂ exhibits highly sensitive turn-on sensing of H₂S over other environmentally and biologically relevant species under physiological conditions. Furthermore, this approach for fluorescent turn-on sensing of H₂S is expected to extend to other water-stable MOFs containing uncoordinated -COOH.

A regenerative metal-organic framework for reversible uptake of Cd(ii): from effective adsorption to in situ detection

An extraordinary metal-organic framework FJI-H9 with high adsorption and selectivity for the reversible uptake of Cd(ii) has been developed. Further research indicates that such high absorption results from an unusual synergy from active sites and the confined cavity. In addition, fast detection of Cd(ii) at low concentrations down to 10 ppm and in situ reconstruction of the used framework into a fresh one have also been successfully achieved.

Crystal structure of dichlorido[bis(2-hydroxyethyl)5′-([2,2′:6′,2′′-terpyridin]-4′-yl)-[1,1′:3′,1′′-terphenyl]-4,4′′-dicarboxylato]zinc(II), C39H31Cl2N3O6Zn

C39H31Cl2N3O6Zn, monoclinic, C2/c, a = 20.7287(17) Å, b = 14.4602(11) Å, c = 11.2765(9) Å, β = 90.0°, V = 3380.0(5) Å3, Z = 4, R gt (F) = 0.0487, wR ref (F 2 ) = 0.1334, T = 293 K.

Crystal structure of poly[(μ 2-1,4-bis((1H-imidiazol-1-yl)methyl)benzene-κ 2 N:N′)-(μ 2-4,4′-(1,2-phenylenebis(oxy)dibenzoato-κ 4 O,O′:O′′,O′′′)nickel(II)], C34H26O6N4Ni

C34H26O6N4Ni, monoclinic, P2 1 /c, a = 11.4709(19) Å, b = 13.328(2) Å, c = 20.062(3) Å, β = 94.305(3)°, V = 3058.5(9) Å3, Z = 4, R gt (F) = 0.0393, wR ref (F 2 ) = 0.0868, T = 293 K.

Crystal structure of poly[bis(μ4-4,4′-(1,2-phenylenebis(oxy))dibenzoato-κ4 O:O′:O′′:O′′′)bis(μ3-4,4′-(1,2-phenylenebis(oxy))dibenzoato–κ3 O:O′:O′′)(μ2-1-(4-((1H-imidazol-1-yl)methyl)benzyl)-1H-imidazole-κ2 N:N′)tetracobalt(II)], C94H62O24N4Co4

C94H62O24N4Co4, triclinic, P1̅, a = 9.3604(11) Å, b = 11.7945(14) Å, c = 19.805(2) Å, α = 94.227(2)°, β = 98.390(2)°, γ = 98.965(2)°, V = 2126.2(4) Å3, Z = 1, R gt (F) = 0.0540, wR ref (F 2 ) = 0.1163, T = 293 K.

Applications of water stable metal–organic frameworks

A comprehensive review is given on the applications of water stable metal–organic frameworks in areas of adsorption, membrane separation, sensing, catalysis, and proton conduction.

The construction, structures, and functions of pillared layer metal–organic frameworks

Pillared layer metal–organic frameworks (PL-MOFs), belonging to one representative of porous materials, have witnessed major advances in the past few years.

Experimental investigation on the water stability of amino-modified indium metal–organic frameworks

The water stability of MIL-68(In)–NH₂ was first investigated detailedly in this study.

Syntheses, crystal structures and properties of metal–organic rotaxane frameworks with cucurbit[6]uril

Five new cucurbit[6]uril-based MORFs are hydrothermally synthesized by the mixed ligand strategy and their fluorescence properties have been investigated.

An efficient and sensitive fluorescent pH sensor based on amino functional metal–organic frameworks in aqueous environment

In this work, an amino group functionalized MOF (Al-MIL-101-NH₂), which shows strong blue luminescence, is used as pH sensor. Due to the protonated amino group, the fluorescence intensity of Al-MIL-101-NH₂almost increases with increasing pH and gives a good linear relationship (R²= 0.99688) with the pH value.

Selective removal of transition metal ions from aqueous solution by metal–organic frameworks

Carboxyl groups in adjacent ligands in UiO-66(Zr)–2COOH exhibit specific capture performance for Cu²⁺, resulting in high separation selectivity for Cu²⁺/Ni²⁺.