Metal-organic Frameworks Research Articles

Gas adsorption and separation applications of MOF materials

Abstract. Low-carbon hydrocarbons (C1-C4) are really important raw materials used in making different kinds of big molecules and stuff in industries. Before, people mostly used super cold cooling and a method where stuff gets soaked up. But these ways need big machines and use a lot of energy. So, scientists are trying to make new ways to separate things that don't use as much energy. One great idea is using how different gases stick to things to separate them. This idea could be a brilliant way to replace the old methods. The most important part of this idea is making things that can stick to the gases. There's this special material called metal-organic frameworks (MOFs) that's a mix of things from nature and chemicals. It has tiny holes and places that can do special things, and it's being studied a lot for separating gases. Traditional porous materials like activated carbon, silica gel, and molecular sieves have been widely used in industries, which has greatly contributed to industrial growth and people's living standards. MOFs have changeable structures and spots that can do special things. By changing the metal bits or the organic parts, we can control the size of the holes in MOFs, the special spots, and how much surface they have. These things make MOFs useful for storing gases, separating stuff by sticking and making reactions happen in fields like chemistry [1-3]. This paper explores the categories of MOF applications.

Steering diffusion selectivity of chemical isomers within aligned nanochannels of metal-organic framework thin film

The movement of molecules (i.e. diffusion) within angstrom-scale pores of porous materials such as metal-organic frameworks (MOFs) and zeolites is influenced by multiple complex factors that can be challenging to assess and manipulate. Nevertheless, understanding and controlling this diffusion phenomenon is crucial for advancing energy-economic membrane-based chemical separation technologies, as well as for heterogeneous catalysis and sensing applications. Through precise assessment of the factors influencing diffusion within a porous metal-organic framework (MOF) thin film, we have developed a chemical strategy to manipulate and reverse chemical isomer diffusion selectivity. In the process of cognizing the molecular diffusion within oriented, angstrom-scale channels of MOF thin film, we have unveiled a dynamic chemical interaction between the adsorbate (chemical isomers) and the MOF using a combination of kinetic mass uptake experiments and molecular simulation. Leveraging the dynamic chemical interactions, we have reversed the haloalkane (positional) isomer diffusion selectivity, forging a chemical pathway to elevate the overall efficacy of membrane-based chemical separation and selective catalytic reactions.

Recent advances and future perspectives of metal-organic frameworks as efficient electrocatalysts for CO2 reduction

AbstractThe conversion of carbon dioxide (CO2) to the reduced chemical compounds offers substantial environmental benefits through minimizing the emission of greenhouse gas and fostering sustainable practices. Recently, the unique properties of metal-organic frameworks (MOFs) make them attractive candidates for electrocatalytic CO2 reduction reaction (CO2RR), providing many opportunities to develop efficient, selective, and environmentally sustainable processes for mitigating CO2 emissions and utilizing CO2 as a valuable raw material for the synthesis of fuels and chemicals. Here, the recent advances in MOFs as efficient catalysts for electrocatalytic CO2RR are summarized. The detailed characteristics, electrocatalytic mechanisms, and practical approaches for improving the electrocatalytic efficiency, selectivity, and durability of MOFs under realistic reaction conditions are also clarified. Furthermore, the outlooks on the prospects of MOF-based electrocatalysts in CO2RR are provided.

Perylene- and Perylene Diimide-based Framework Materials Constructed through Metal Coordination.

Metal-organic frameworks (MOFs) are a class of materials composed by coordinative interactions between metal ions and organic linkers, encompassing two-dimensional (2D), and three-dimensional (3D) architectures. Metal-organic cages (MOCs), a special case of these species, are discrete molecular "capsules" with zero-dimensional (0D) structures. Over the last two decades, MOFs and MOCs composed of organic perylene (P) and perylene diimide (PDI) linkers have gained much attention due to their versatile properties, which can be further enhanced after incorporation into the frameworks. This minireview highlights recent progress in the construction and application of P/PDI-based coordination framework materials. The text offers an overview of the synthesis of P/PDI organic linkers, proceeds to their integration into coordination frameworks of different dimensionalities - 2D and 3D MOFs, and 0D MOCs, and then explores potential applications. These include sensing, photocatalysis, electrochemical devices as well as photothermal conversion and focus on the apparent structure-property relationships. Finally, the challenges and future prospects of P/PDI-derived coordination frameworks will be addressed.

Metal–Organic Framework and Biopolymer-Based Composite Hydrogel for Enhanced Encapsulation of Anticancer Drugs: A New Age Transdermal Drug Delivery Vehicle

Metal–Organic Framework and Biopolymer-Based Composite Hydrogel for Enhanced Encapsulation of Anticancer Drugs: A New Age Transdermal Drug Delivery Vehicle

The Throttle Effect in Metal-Organic Frameworks for Distinguishing Water Isotopes.

Metal-organic frameworks (MOFs) have been widely used for separation, but amplifying subtle differences between similar molecules to achieve effective separation remains a great challenge. In this study, we utilize the fluorescent molecule uranine (Ura) to modulate the pores of zeolitic-imidazolate framework 8 (ZIF8), creating an unusual throttle effect. By monitoring fluorescence intensity changes in Ura, the transport diffusion process could be quantified to reveal the diffusion constant of solvents. When we pushed the Ura occupancy to its limit (from 59% to 76% and 98%), the diffusion rate decreases by 2 orders of magnitude. Most importantly, there is a significant dissymmetry between the two-way exchange rates of solvents, and the rates of H2O and D2O became distinguishable. Such unusual throttle effects disappear at low Ura occupancy of 59% and 76%. We believe that the throttle effect with small-molecule loading could provide a universal design principle for MOF-based applications, especially for isotope separation.

Chemical warfare agents: Structure, properties, decontamination (part 1)

The review is aimed at summarizing and systematizing information on various methods of deactivation of chemical warfare agents required on the battlefield, in laboratories, research institutions, production facilities, as well as information on storage and destruction of poisonous substances. The review provides data on warfare poisons with different tactical and physiological characteristics and outlines the main directions of their neutralization, which are the most effective under the conditions of their real use. In the first part of this review, the methods of deactivation of warfare poisonous substances using functionalized metal-organic framework materials, on which reactions of their transformation into low-toxic products take place, are considered in detail. In addition, metal-organic frameworks are porous crystalline structures that have many areas of application and can be used as adsorbents and catalysts. The above material shows the importance of general knowledge about the physical and chemical properties of chemical warfare agents, the rate of their decomposition, the advantages and disadvantages of certain available technologies for their application. This review can be useful for finding new and improving known methods of decontamination of chemical warfare agents and other ecotoxicants, for environmental protection.

A Flexible Phosphonate Metal-Organic Framework for Enhanced Cooperative Ammonia Capture.

Ammonia (NH3) production in 2023 reached 150 million tons and is associated with potential concomitant production of up to 500 million tons of CO2 each year. Efforts to produce green NH3 are compromised since it is difficult to separate using conventional condensation chillers, but in situ separation with minimal cooling is challenging. While metal-organic framework materials offer some potential, they are often unstable and decompose in the presence of caustic and corrosive NH3. Here, we address these challenges by developing a pore-expansion strategy utilizing the flexible phosphonate framework, STA-12(Ni), which shows exceptional stability and capture of NH3 at ppm levels at elevated temperatures (100-220 °C) even under humid conditions. A remarkable NH3 uptake of 4.76 mmol g-1 at 100 μbar (equivalent to 100 ppm) is observed, and in situ neutron powder diffraction, inelastic neutron scattering, and infrared microspectroscopy, coupled with modeling, reveal a pore expansion from triclinic to a rhombohedral structure on cooperative binding of NH3 to unsaturated Ni(II) sites and phosphonate groups. STA-12(Ni) can be readily engineered into pellets or monoliths without losing adsorption capacity, underscoring its practical potential.

Cooperative lattice theory for CO2 adsorption in diamine-appended metal-organic framework at humid direct air capture conditions.

The effect of humidity on the cooperative adsorption of CO2 from the air on amine-appended metal-organic frameworks is studied both experimentally and theoretically. Breakthrough experiments show that, at low relative humidities, there is an anomalous induction effect, where the kinetics at short times are slower than kinetics at long times. The induction effect gradually vanishes as relative humidity is increased, corresponding to an increase in CO2 adsorption rate. A new theory is proposed based on the lattice kinetic theory (LKT), which explains these experimental results. LKT can accurately represent the measured data over the full range of humidities by postulating that the presence of adsorbed water shifts the equilibrium clusters from cooperatively bound chains to non-cooperatively bound CO2. A consequence of this transition is that CO2 exhibits step adsorption isotherm in dry air and a standard Langmuir adsorption isotherm in high humidity air.

A new 3D Cd(II)-based metal-organic framework as dual-function luminescent sensor to ions and antibiotic: Mechanism and theoretical studies

A new Cd(II) metal-organic framework (Cd-MOF), namely [Cd2(L)(H2O)3·3·4H2O]n (1) (H4L = (3-(2,4-dicarboxylphenyl)-2,6-dicarboxylpyridine)) was effectively produced. 1 shows a new 3D 3,5-connected network with gra topology built by the multi-carboxylate linker through (κ2)-(κ1)-μ2, (κ1)-(κ1)-μ1 and (κ0)-(κ1)-μ1 coordination modes. The sensing results showed that 1 would be a viable possibility for developing luminous sensors to sensitively probe nitrofurazone (NFZ), Fe3+, and CrO42-. The limits of detection (LODs) for Fe3+, CrO42−and NFZ were calculated to be 1.17 × 10–7 M-1, 1.63 × 10–7 M-1 and 7.03 × 10–8M-1, respectively. Density functional theory (DFT), UV–vis spectroscopy, and PXRD research have reinforced the understanding of luminescence sensing mechanisms.

Recent Advances in High-Performance Membrane Materials for Fuel Cells

Fuel cells have emerged as a key technology for clean energy production, with proton exchange membrane (PEM) fuel cells being one of the most promising types due to their high efficiency and low emissions. A critical component of PEM fuel cells is the membrane, which plays a crucial role in ion transport and overall system performance. Recent advances in membrane materials have focused on improving proton conductivity, chemical stability, and durability while reducing production costs. This review discusses recent developments in high-performance membrane materials, including polymer blends, hybrid membranes, and metal-organic frameworks (MOFs). These innovative materials have shown significant potential in overcoming the limitations of traditional membranes like Nafion®. Advances in acid-base membranes, such as polybenzimidazole (PBI)-based systems, have demonstrated improvements in high-temperature performance. Enhanced cross-linking techniques, the use of antioxidant additives, and nanofillers have further contributed to improved membrane durability. Despite these advancements, challenges remain in scaling up production and reducing costs. Future research must focus on addressing these issues to enable the widespread commercial use of fuel cells. The progress in membrane material technology is critical to realizing the potential of fuel cells as a viable solution for sustainable energy.

CO2 Fixation via epoxide cycloaddition with a highly active and stable MOF-808/GO composite catalyst

The CO2 cycloaddition reaction effectively mitigates the greenhouse effect while producing high-value cyclic carbonates. Metal-organic frameworks (MOFs) have shown promise for CO2 cycloaddition with epoxides; however, the aggregation of MOFs due to high surface energy hinders mass transfer and catalytic performance. By pre-coordinating graphene oxide (GO) to regulate the dispersion of MOF-808, the resulting MOF-808/GO-100 composite catalyst exhibits twice the activity of pristine MOF-808, achieving 92.6% conversion of epichlorohydrin (ECH) with 98.2% selectivity to ECH carbonate without adding any co-catalysts. The incorporation of GO introduces numerous hydroxyl groups on the catalyst surface, serving as hydrogen bonding donors. The oxygen-containing groups on GO can compete with ligands for Zr coordination, generating defective Zr sites. The synergistic effect between defective Zr sites and hydrogen bonding donors collectively promotes epoxide opening. Notably, GO correspondingly enhances the dispersion of MOF-808 and induces mesopore formation through its stacking effect at the interface with MOF-808. Across various epoxide cycloaddition reactions, MOF-808/GO-100 consistently demonstrated optimal performance and maintained high stability over multiple reaction cycles.

Tunable double emission of Sb3+/Mn2+ doping stabilized organic-inorganic hybrid zinc-based halides

Low-dimensional organic-inorganic hybrid metal halides (OIHMHs) have attracted much attention lately in contrast to all-inorganic metal halides because of their excellent photophysical properties and tunable emission wavelengths. Zn-based metal halides have the following advantages: simplicity of synthesis, wide bandgap, and excellent chemical stability. Therefore, they are well-suited as host materials for photoluminescence by cation ion doping. We have successfully synthesized intrinsically non-emissive 0D (PPZ)ZnCl4 [PPZ (1-phenylpiperazine) = C10H14N2], and by mono/co-doping with Mn2+ and Sb3+, interesting luminescence phenomena have been produced. Single-doped Mn2+ / Sb3+ shows distinctive green and single orange emission, respectively. However, the co-doped Mn2+ and Sb3+ appeared as dynamic double emission peaks at 530 nm and 670 nm. Therefore, the co-doped crystals showed luminescence from two different luminescence centers ([MnCl4]2- and [SbCl4]-). We used DFT to calculate the DOS (density of states) of co-doped crystals, which results in energy transfer between Mn2+ and Sb3+. All of the above samples showed high stability after being left for two months. In addition, two different luminescence centers can be produced by the adjustment of the excitation of the co-doped (PPZ)ZnCl4: Sb0.12Mn0.08 samples, which is a distinguishable and obvious photoluminescence phenomenon having great potential preparation of advanced anti-counterfeiting materials in the future.

Realizing pure white light emission by adjusting the molar ratio of Eu3+/Tb3+ in two new Ln-based metal-organic frameworks

Two Ln-based Metal-Organic Frameworks (MOFs), Eu-BCTC and Tb-BCTC, were synthesized using the ligand [9,9′-bicarbazole]-3,3′,6,6′-tetracarboxylic acid (H4BCTC) via a solvothermal method. They emit green or red light, respectively. By adjusting the molar ratio of Eu3+/Tb3+ of LMOFs, a single-phase white light emitter, Eu0.075Tb0.925-BCTC, was successfully synthesized. This compound exhibits an ideal CIE coordinate of (0.33, 0.33), internal quantum yield (IQY) at 8.37 % and a color temperature of 5623 K. Moreover, it has excellent performance in detecting Fe3+, Cr2O72− and CrO42−, with limit of detections (LODs) at 7.403 × 10−5 M, 1.487 × 10−5 M and 3.053 × 10−5 M, respectively. This advancement marks a significant contribution to the field of MOF-based white-light-emitting phosphors and fluorescence probes.

Spatiotemporal Encapsulation of Tandem Enzymes in Hierarchical Metal-Organic Frameworks for Cofactor-Dependent Photoenzymatic CO2 Conversion.

The photo-enzyme coupling system (PECS) holds immense potential in "green" biomanufacturing, encompassing the realms of pharmaceuticals, fuels, and carbon sequestration. Nevertheless, the intricate nature of enzymes' structures significantly impedes the seamless integration of multiple enzymes in a precise, tandem fashion, with exact control over their distribution, posing a formidable challenge. Herein, it has devised a mesoporous csq-type metal organic framework (Zr-MOF) from meso-tetrakis-(4-((phenyl)ethynyl)benzoate)porphyrin (Por-PTP) and Zr6(μ3-O)4(μ3-OH)4(OH)4(H2O)4) nodes (Zr6clusters), featuring intricate hierarchical hexagonal (5.8nm) and triangular (2.9nm) channels, enabling the simultaneous encapsulation of Formate dehydrogenase from Candida boidinii (CbFDH)and ferredoxin-NADP+ reductase (FNR) via a spatiotemporally controlled strategy for cofactor-dependent photoenzymatic carbon dioxide (CO2) conversion. Upon illumination, photoexcited electrons originating from the Zr-MOF frameworks migrate to the adjacent FNR for cofactor NADH regeneration, which is then harnessed by proximal CbFDH for CO2 fixation. Concurrently, the resulting holes are neutralized by AA for system recovery. The results demonstrated the confinement of tandem enzymes within MOF channels significantly enhanced the performance of multi-enzyme cascade pathways as well as augmenting the local NAD+/NADH, which leading to a further improvement in the efficiency of tandem biocatalytic formic acid generation (55mm) from CO2. Crucially, the photo-enzyme-coupled factories exhibited remarkable stability alongside exceptional recyclability, attributed to the preservation of MOF skeletons.

The Structure and Optical Properties of Luminescent Terbium Terephthalate Metal–Organic Frameworks Doped with Yttrium, Gadolinium, and Lanthanum Ions

The structural features and luminescent properties of heterometallic Tb–Gd, Tb–La, and Tb–Y terephthalate metal–organic frameworks, namely (TbxM1−x)2(1,4-bdc)3∙4H2O (M = Gd, La, Y), were studied in detail in a wide concentration range (x = 0.001–1). The crystalline phase of synthesized compounds corresponds to Ln2(1,4-bdc)3·4H2O. The lifetime of 5D4 decreased with increased Tb3+ concentration, but PLQY depends non-linearly on the Tb3+ concentration. The 50% substitution of Tb3+ for Y3+, Gd3+, or La3+ ions result in the significant enhancement of photoluminescence quantum yield, up to 1.6 times. The morphology, thermal stability, and vibrational structure of the selected homo- and bi-metallic materials is reported as well.

Unexpected Photodriven Linker-to-Node Hole Transfer in a Zirconium-Based Metal-Organic Framework.

Zr6(μ3-O)4(μ3-OH)4 node cores are indispensable building blocks for almost all zirconium-based metal-organic frameworks. Consistent with the insulating nature of zirconia, they are generally considered electronically inert. Contrasting this viewpoint, we present spectral measurements and calculations indicating that emission from photoexcited NU-601, a six-connected Zr-based MOF, comes from both linker-centric locally excited and linker-to-node charge-transfer (CT) states. The CT state originates from a hole transfer process enabled by favorable energy alignment of the HOMOs of the node and linker. This alignment can be manipulated by changing the pH of the medium, which alters the protonation state of multiple oxy groups on the Zr-node. Thus, the acid-base chemistry of the node has a direct effect on the photophysics of the MOF following linker-localized electronic excitation. These new findings open opportunities to understand and exploit, for energy conversion, unconventional mechanisms of exciton formation and transport in MOFs.

Merged-nets enumeration for the systematic design of multicomponent reticular structures.

Rational design of intricate multicomponent reticular structures is often hindered by the lack of suitable blueprint nets. We established the merged-net approach, proffering optimal balance between designability and complexity, as a systematic solution for the rational assembly of multicomponent structures. In this work, by methodically mapping node-net relationships among 53 basic edge-transitive nets, we conceived a signature net map to identify merging net pairs, resulting in the enumeration of 53 merged nets. We developed a practical design algorithm and proposed more than 100 multicomponent metal-organic framework platforms. The effectiveness of this approach is commended by the successful synthesis of four classes of materials, which is based on merging three-periodic nets with the four possible net periodicities. The construction of multicomponent materials based on derived nets of merged nets highlights the potential of the merged-net approach in accelerating the discovery of intricate reticular materials.

Incorporation of Zirconium-Based Metal-Organic Framework on Kaolin for Boosting Rhodamine-B Adsorption

This research was focused on the use of a zirconium-based metal-organic framework (UiO-66) supported kaolin composite (UiO-66@kaolin) for rhodamine-b (RB) adsorption. The proposed composite was prepared via solvothermal method, and the functional groups were characterized by FT-IR analysis. The adsorption performances of kaolin and UiO-66@kaolin were compared by equilibrium experiments and the maximum monolayer adsorption capacities calculated from the Langmuir model were found to be 2.10 mg g⁻¹ and 17.22 mg g⁻¹, respectively. It was observed that the adsorption capacity of pristine kaolin was significantly increased by UiO-66 support. Besides, kaolin mineral was fitted to the monolayer Langmuir isotherm model, while the isotherm character of the composite adsorbent was described by the multilayer model Freundlich. The equilibrium time for UiO-66@kaolin was obtained as 240 min and the adsorption process was identified to occur via chemisorption with pseudo-second-order model fitting. It was observed that RB removal rate decreased with decreasing pH and solution pH had a major effect on adsorption. The parameters gathered from thermodynamic data demonstrated that RB adsorption was exothermic and spontaneous. The effective removal of RB dye from wastewater systems using the prepared UiO-66@kaolin composite adsorbent was confirmed by extensive adsorption studies. The reported findings may inspire further potential investigations.

Benchmark Investigation of SCC-DFTB Against Standard DFT to Model Phononic Properties in Two-Dimensional MOFs for Thermoelectric Applications.

Despite the importance of modeling lattice thermal conductivity in predicting thermoelectric (TE) properties, computational data on heat transport, especially from first-principles, in 2D metal-organic frameworks (MOFs) remain limited due to the high computational cost. To address this, we provide a benchmark of the performance of semiempirical self-consistent-charge density functional tight-binding (SCC-DFTB) methods against density functional theory (DFT) for monolayer, serrated, AA-stacked and/or AB-stacked Zn3C6O6, Cd3C6O6, Zn-NH-MOF, and Ni3(HITP)2 MOFs. Harmonic lattice dynamics calculations, including partial atomic contributions to phonon dispersions, are evaluated with both SCC-DFTB and DFT, whereas anharmonic transport (i.e., thermal conductivity) is evaluated with SCC-DFTB only. Our findings further suggest that unlike the other stacking geometries modeled, serrated Zn3C6O6, serrated Zn-NH-MOF, and wavy serrated Ni3(HITP)2 represent stable geometries. While Zn3C6O6 and Zn-NH-MOF exhibit a higher power factor than Ni3(HITP)2 (as found in our previous work), Zn-NH-MOF shows lower thermal conductivity, resulting in the highest thermoelectric figure of merit (ZT) among the studied MOFs.