Fine-Tuning the Pore Environment of the Microporous Cu-MOF for High Propylene Storage and Efficient Separation of Light Hydrocarbons

A Stable Layered Microporous MOF Assembled with Y-O Chains for Separation of MTO Products

Benefiting from highly tunable pore environments, some metal-organic frameworks (MOFs) have recently shown promising prospects in the separation of methanol-to-olefin (MTO) products (mainly C3H6 and C2H4). However, the "trade-off" between gas storage capacity and selectivity always results in inefficient separation. In addition, poor stability of MOFs also limits practical separation applications. Herein, we have successfully assembled a layered Y-MOF (FJI-W9) with bent diisophthalate ligands (H4L), Y-O chains, and 2-fluorobenzoic acids. As expected, FJI-W9 not only exhibits good chemical stability but also shows significant potential for C3H6/C2H4 separation. For FJI-W9, the C3H6 uptake at 298 K and 10 kPa is 63 cm3/g, and the IAST selectivity of FJI-W9 for C3H6/C2H4 (V/V = 50/50) is calculated to be 20.5. To the best of our knowledge, both C3H6 uptake and selectivity of FJI-W9 surpass most porous materials. GCMC simulation indicates that the special supramolecular binding sites in FJI-W9 have much stronger interactions with C3H6 than C2H4 molecules. More importantly, practical breakthrough experiments demonstrate that FJI-W9 can effectively separate C3H6/C2H4 (50/50) mixtures, thus obtaining high-purity C2H4 and C3H6, respectively.

Palladium(II) Modulation Enhances the Water Stability and Aqueous 99TcO4-/ReO4- Removal Performance of Metal-Organic Frameworks

Improving the water stability of metal-organic frameworks (MOFs) is essential for their use in water pollution treatment and environmental remediation, though it remains technically challenging. Herein, we report a novel cationic MOF constructed with [Th6O4(OH)4(COO)12] units and [CoN4·Cl2] units possessing a ftw-type topology (denoted as 1-Th-Co). 1-Th-Co itself exhibited poor water stability but excellent stability following a palladium(II) modulation strategy. Experimental studies reveal that Co(II) ions in 1-Th-Co were replaced by Pd(II) ions through cation exchange in N,N-diethylformamide (yielding 1-Th-Pd). The planar PdN4 units in 1-Th-Pd were responsible for improving the water stability of the framework. As a result, 1-Th-Pd offered excellent stability, fast adsorption kinetics, and high removal ratios for 99TcO4- and ReO4- (as a 99TcO4- surrogate) in contaminated water. When used in packed columns, 1-Th-Pd can dynamically capture ReO4- from groundwater. This work provides a new avenue for improving the water stability of MOFs, offering new vistas for the decontamination of aqueous solutions containing 99TcO4- and ReO4-.

Tailorable Multi-Modular Pore-Space-Partitioned Vanadium Metal-Organic Frameworks for Gas Separation

Currently, few porous vanadium metal-organic frameworks (V-MOFs) are known and even fewer are obtainable as single crystals, resulting in limited information on their structures and properties. Here this work demonstrates remarkable promise of V-MOFs by presenting an extensible family of V-MOFs with tailorable pore geometry and properties. The synthesis leverages inter-modular synergy on a tri-modular pore-partitioned platform. New V-MOFs show a broad range of structural features and sorption properties suitable for gas storage and separation applications for C2H2/CO2, C2H6/C2H4, and C3H8/C3H6. The c/a ratio of the hexagonal cell, a measure of pore shape, is tunable from 0.612 to 1.258. Other tunable properties include pore size from 5.0 to 10.9 Å and surface area from 820 to 2964 m2 g-1. With C2H2/CO2 selectivity from 3.3 to 11 and high uptake capacity for C2H2 from 65.2 to 182 cm3 g-1 (298K, 1 bar), an efficient separation is confirmed by breakthrough experiments. The near-record high uptake for C2H6 (166.8 cm3 g-1) contributes to the promise for C2H6-selective separation of C2H6/C2H4. The multi-module pore expansion enables transition from C3H6-selective to more desirable C3H8-selective separation with extraordinarily high C3H8 uptake (254.9 cm3 g-1) and high separation potential (1.25 mmol g-1) for C3H8/C3H6 (50:50 v/v) mixture.

Antibacterial efficacy of copper-based metal-organic frameworks against Escherichia coli and Lactobacillus

The widespread and excessive use of antimicrobial drugs has resulted in a concerning rise in bacterial resistance, leading to a risk of untreatable infections. The aim of this study was to formulate a robust and efficient antibacterial treatment to address this challenge. Previous work focused on the effectiveness of the Cu-BTC metal-organic framework (MOF; BTC stands for 1,3,5-benzenetricarboxylate) in combatting various bacterial strains. Herein, we compare the antibacterial properties of Cu-BTC with our newly designed Cu-GA MOF, consisting of copper ions bridged by deprotonated gallate ligands (H2gal2-), against Escherichia coli (E. coli) and Lactobacillus bacteria. Cu-GA was synthesized hydrothermally from copper salt and naturally derived gallic acid (H4gal) and characterized for antibacterial evaluation. The gradual breakdown of Cu(H2gal) resulted in a significant antibacterial effect that is due to the release of copper ions and gallate ligands from the framework. Both copper MOFs were nontoxic to bacteria at low concentrations and growth was completely inhibited at high concentrations when treated with Cu-BTC (1500 μg for E. coli and 1700 μg for Lactobacillus) and Cu-GA (2000 μg for both bacterial strains). Furthermore, our agarose gel electrophoresis results indicate that both MOFs could disrupt bacterial cell membranes, hindering the synthesis of DNA. These findings confirm the antibacterial properties of Cu-BTC and the successful internalization of Cu2+ ions and gallic acid by bacteria from the Cu-GA MOF framework, suggesting the potential for a sustained and effective therapeutic approach against pathogenic microorganisms.

Flow Channel with Wrinkles and Calcium Sites in a Ca-MOF for Direct One-Step Ethylene Purification from C2 Gases and MTO Products Separation

The strategy of flow channel with wrinkles and calcium sites for single-step C2H4 purification from C2 gases and methanol-to-olefins (MTO) products separation was realized in FJI-Y9. The adsorption amounts showed a total reversal order of C3H6 > C2H6 > C2H2 > C2H4 at 298 K. Modeling indicated that the wrinkles and Ca2+ facilitated the full contact of C3H6 and C2H6. Breakthrough experiments illustrated that FJI-Y9 could yield pure C2H4 in a single step with a productivity of 0.78 mmol g-1. In a lone adsorption/desorption cycle for MTO product separation, the productivities of C3H6 and C2H4 were 1.96 and 1.29 mol g-1, standing as the highest recorded values.

Scalable Synthesis of Robust MOF for Challenging Ethylene Purification and Propylene Recovery with Record Productivity

Ethylene (C2H4) purification and propylene (C3H6) recovery are highly relevant in polymer synthesis, yet developing physisorbents for these industrial separation faces the challenges of merging easy scalability, economic feasibility, high moisture stability with great separation efficiency. Herein, we reported a robust and scalable MOF (MAC-4) for simultaneous recovery of C3H6 and C2H4. Through creating nonpolar pores decorated by accessible N/O sites, MAC-4 displays top-tier uptakes and selectivities for C2H6 and C3H6 over C2H4 at ambient conditions. Molecular modelling combined with infrared spectroscopy revealed that C2H6 and C3H6 molecules were trapped in the framework with stronger contacts relative to C2H4. Breakthrough experiments demonstrated exceptional separation performance for binary C2H6/C2H4 and C3H6/C2H4 as well as ternary C3H6/C2H6/C2H4 mixtures, simultaneously affording record productivities of 27.4 and 36.2 L kg-1 for high-purity C2H4 (≥99.9 %) and C3H6 (≥99.5 %). MAC-4 was facilely prepared at deckgram-scale under reflux condition within 3 hours, making it as a smart MOF to address challenging gas separations.

CYCU-3: an Al(III)-based MOF for SO2 capture and detection

The Al(III)-based MOF CYCU-3 exhibits a relevant SO2 adsorption performance with a total uptake of 11.03 mmol g-1 at 1 bar and 298 K. CYCU-3 displays high chemical stability towards dry and wet SO2 exposure. DRIFTS experiments and computational calculations demonstrated that hydrogen bonding between SO2 molecules and bridging Al(III)-OH groups are the preferential adsorption sites. In addition, photoluminescence experiments demonstrated the relevance of CYCU-3 for application in SO2 detection with good selectivity for SO2 over CO2 and H2O. The change in fluorescence performance demonstrates a clear turn-on effect after SO2 interaction. Finally, the suppression of ligand-metal energy transfer along with the enhancement of ligand-centered π* → π electronic transition was proposed as a plausible fluorescence mechanism.

Water-Stable Microporous Bipyrazole-Based Framework for Efficient Separation of MTO Products

Recently, methanol-to-olefins (MTO) technology has been widely used. The development of new adsorbents to separate MTO products and obtain high-purity ethylene (C2H4) and propylene (C3H6) has become an urgent task. Herein, an exceptionally highly water-stable metal-organic framework (MOF), [Cu3(OH)2(Me2BPZ)2]·(solvent)x (1) (H2Me2BPZ = 3,3'-dimethyl-1H,1'H-4,4'-bipyrazole) with hexagonal pores, has been elaborately designed and constructed. After being soaked in water for 7 days, it still maintains its structure, and the uptake of N2 at 77 K is unchanged. The adsorption capacity of C3H6 can reach 138 cm3 g-1, while the uptake of C2H4 is only 52 cm3 g-1 at 298 K and 1 bar. The dynamic breakthrough experiments show that the mixture of C3H6/C2H4 (50/50, v/v) can be efficiently separated in one step. High-purity C2H4 and C3H6 can be obtained through an adsorption and desorption cycle and the yields of C2H4 (purity ≥ 99.95%) and C3H6 (purity ≥ 99%) are 84 and 48 L kg-1, respectively. Surprisingly, when the flow rate is increased, the separation performance has no obvious change. Additionally, humidity has no effect on the separation performance. Finally, theoretical simulations indicate that there are stronger interactions between the C3H6 molecule and the framework, which are beneficial to capturing C3H6 over C2H4.

Electrochemiluminescence Properties and Sensing Application of Zn(II)-Metal-Organic Frameworks Constructed by Mixed Ligands of Para Dicarboxylic Acids and 1,10-Phenanthroline

Four metal-organic frameworks (MOFs) were designed and prepared through a mixed-ligand strategy by controlling the combination of various dicarboxylic acid ligands with invariant center metal and o-phenanthroline heterocyclic ligand. The regulatory effects of ligand electronic band and crystal structure on the electrochemiluminescence (ECL) characteristics of MOFs were verified by experimental results and density functional theory (DFT) calculations. The flexible chain structure of MOF-2 promotes electron transfer between MOF electroactive free radicals and the co-reactant, making it show outstanding ECL characteristics among all of the four MOFs with the luminescence quantum efficiency 8.37 times that of tris(bipyridine)-ruthenium(II) ([Ru(bpy)3]2+). Meanwhile, a new ECL mechanism for MOF luminescent crystal materials with reactive oxygen species in solvents as a co-reactant in the aqueous aerobic environment has been proposed. MOF-2 was selected to construct an ECL sensor for the determination of glucose in human urine samples. This study provides a useful idea for the development and design of new luminescent molecular crystal materials.

Porous MOF Featuring 2D Intersecting Channels Based on a Pentanuclear Mn5(COO)10CO3 Cluster with Upgrading of Pipeline Natural Gas

Natural gas plays a crucial role in daily and industrial production, but the impurities contained in natural gas limit its further use. It is very important to develop adsorbents that can separate CH4 from multicomponent mixtures, but there are still many challenges and problems. Herein, a novel porous MOF {[Mn5(pbdia)2(CO3)(H2O)2] ↔ 5H2O ↔ 2DMF}n (pbdia = 2,2'-(5-carboxy-1,3-phenylene)bis(oxy) diterephthalic acid) was successfully synthesized based on a flexible pentacarboxylic acid ligand and a unique pentanuclear Mn5(COO)10CO3 cluster. The MOF reveals a 3D porous structure with 2D intersecting channels, which shows high C3H8, C2H6, and CO2 adsorption capacities and affinities over CH4. Moreover, the ideal adsorption solution theory selectivities of C3H8/CH4, C2H6/CH4, and CO2/CH4 can reach 263.0, 27.0, and 7.7, respectively, suggesting a potential for removing the low content of C3H8, C2H6, and CO2 from pipeline natural gas, which was further confirmed by breakthrough curves and GCMC simulations.

Multi-Modular Design of Stable Pore-Space-Partitioned Metal-Organic Frameworks for Gas Separation Applications

Pore space partition (PSP) is an effective materials design method for developing high-performance small-pore materials for storage and separation of gas molecules. The continued success of PSP depends on broad availability and judicious choice of pore-partition ligands and better understanding of each structural module on stability and sorption properties. Here, by using substructural bioisosteric strategy (sub-BIS), a dramatic expansion of pore-partitioned materials is targeted by using ditopic dipyridyl ligands with non-aromatic cores or extenders, as well as by expanding heterometallic clusters to uncommon nickel-vanadium and nickel-indium clusters rarely known before in porous materials. The dual-module iterative refinement of pore-partition ligands and trimers leads to remarkable enhancement of chemical stability and porosity. Here a family of 23 pore-partitioned materials synthesized from five pore-partition ligands and seven types of trimeric clusters is reported. New materials with such compositionally and structurally diverse framework modules reveal key factors that dictate stability, porosity, and gas separation properties. Among these, materials based on heterometallic vanadium-nickel trimeric clusters give rise to the highest long-term hydrolytic stability and remarkable uptake capacity for CO2 , C2 H2 /C2 H4 /C2 H6 , and C3 H6 /C3 H8 hydrocarbon gases. The breakthrough experiment shows the potential application of new materials for separating gas mixtures such as C2 H2 /CO2 .

An ethynyl-modified interpenetrated metal-organic framework for highly efficient selective gas adsorption

An ethynyl-modified interpenetrated MOF material with lvt topology, [Cu2(BTEB)(NMF)2]·NMF·8H2O (compound 1, H4BTEB = 4,4',4'',4'''-(benzene-1,2,4,5-tetrayltetrakis(ethyne-2,1-diyl))tetrabenzoic acid, NMF = N-Methylformamide), was successfully synthesized by using an alkynyl-functionalized H4BTEB organic ligand under solvothermal conditions. Structural analysis shows that compound 1, consisting of a tetradentate carboxylic acid ligand and classical [Cu2(CO2)4] paddle-wheel structure building units, has a rare 4-connected lvt topology with dual interpenetrating structure, which can improve the framework stability, as well as the gas adsorption capacity and selectivity due to the restricted pore channel. According to the study of gas adsorption performance, compound 1 with a larger surface area, boasts a superior adsorption capacity for small gas molecules. Also, ideal adsorption solution theory (IAST) computational simulation shows that compound 1 has good gas adsorption selectivity for C3H8/CH4, indicating its potential application in gas separation.

Active Sites Decorated Nonpolar Pore-Based MOF for One-step Acquisition of C2 H4 and Recovery of C3 H6

Herein, a 2-fold interpenetrated metal-organic framework (MOF) Zn-BPZ-TATB with accessible N/O active sites in nonpolar pore surfaces was reported for one-step C2 H4 purification from C2 H6 or C3 H6 mixtures as well as recovery of C3 H6 from C2 H6 /C3 H6 /C2 H4 mixtures. The MOF exhibits the favorable C2 H6 and C3 H6 uptakes (>100 cm3  g-1 at 298 K under 100 kPa) as well as selective adsorption of C2 H6 and C3 H6 over C2 H4 . The C3 H6 - and C2 H6 -selective feature were investigated detailedly by experimental tests as well as sorption kinetic studyies. Molecular modelling revealed the multiple interactions between C3 H6 or C2 H6 molecules and methyl groups as well as triazine rings in pores. Zn-BPZ-TATB not only can directly generate 323.4 L kg-1 and 15.4 L kg-1 of high-purity (≥99.9 %) C2 H4 from C3 H6 /C2 H4 and C2 H6 /C2 H4 mixtures, but also provide a large high-purity (≥99.5 %) C3 H6 recovery capacity of 60.1 L kg-1 from C3 H6 /C2 H4 mixtures. More importantly, the high-purity C3 H6 (≥99.5 %) and C2 H4 (≥99.9 %) with the productivities of 38.2 and 12.7 L kg-1 can be simultaneously obtained from C2 H6 /C3 H6 /C2 H4 mixtures through a single adsorption/desorption cycle.

Development of a Mixed Multinuclear Cluster Strategy in Metal-Organic Frameworks for Methane Purification and Storage

Metal-organic frameworks (MOFs) have attracted extensive attention in methane (CH4) purification and storage. Specially, multinuclear cluster-based MOFs usually have prominent performance because of large cluster size and abundant open metal sites. However, compared to diverse combinations of organic linkers, one MOF with two or more multinuclear clusters is difficult to achieve. In this paper, we demonstrate a mixed multinuclear cluster strategy, which successfully led to three new heterometallic MOFs (SNNU-328-330) with the same common H3TATB [2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine] tritopic linker and six types of multinuclear clusters ([YCd(COO)4(μ2-H2O)], [YCd2(COO)8], [In3(COO)6(μ3-OH)], [In3Eu2(COO)9(μ3-OH)3(μ4-O)], [Y9(COO)12(μ3-OH)14] and [Y2Cd8(COO)16(μ2-H2O)4(μ3-OH)8]). Three MOF adsorbents all show great potentials to remove the impurities (CO2 and C2-hydrocarbons) in natural gas and show prominent high-pressure methane storage capacity. Among them, the ideal adsorbed solution theory separation ratios of equimolar C2H2/CH4, C2H4/CH4, C2H6/CH4, and CO2/CH4 at 298 K for SNNU-328 reach to 29.7-16.0, 19.1-8.2, 33.2-10.3, and 74.3-8.5, which have surpassed many famous MOF adsorbents. Dynamic breakthrough experiments conducted at 273 and 298 K showed that SNNU-330 can separate CH4 from C2H2/CH4, C2H4/CH4, C2H6/CH4, and CO2/CH4 mixtures with the breakthrough interval times of about 48.2, 17.9, 37.2, and 17.1 min g-1 (273 K, 1 bar, v/v = 50/50, 2 mL min-1), respectively. Remarkably, SNNU-329 exhibits extremely high methane storage performance at 298 K with the total uptake and working capacity of 192 cm3 cm-3 (95 bar) and 171 cm3 cm-3 (65 bar) due to the synergistic effects of high surface area, suitable pore sizes, and multiple open metal sites.

A Microporous Zn(bdc)(ted)0.5 with Super High Ethane Uptake for Efficient Selective Adsorption and Separation of Light Hydrocarbons

Separating light hydrocarbons (C2H6, C3H8, and C4H10) from CH4 is challenging but important for natural gas upgrading. A microporous metal-organic framework, Zn(bdc)(ted)0.5, based on terephthalic acid (bdc) and 1,4-diazabicyclo[2.2.2]octane (ted) ligands, is synthesized and characterized through various techniques, including powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and porosity analysis. The adsorption isotherms of light hydrocarbons on the material are measured and the isosteric adsorption heats of CH4, C2H6, C3H8, and C4H10 are calculated. The prediction of C2-4/C1 adsorption selectivities is accomplished using ideal adsorbed solution theory (IAST). The results indicate that the material exhibits exceptional characteristics, including a Brunauer-Emmett-Teller (BET) surface area of 1904 m2/g and a pore volume of 0.73 cm3/g. Notably, the material demonstrates remarkable C2H6 adsorption capacities (4.9 mmol/g), while CH4 uptake remains minimal at 0.4 mmol/g at 298 K and 100 kPa. These findings surpass those of most reported MOFs, highlighting the material's outstanding performance. The isosteric adsorption heats of C2H6, C3H8, and C4H10 on the Zn(bdc)(ted)0.5 are higher than CH4, suggesting a stronger interaction between C2H6, C3H8, and C4H10 molecules and Zn(bdc)(ted)0.5. The molecular simulation reveals that Zn(bdc)(ted)0.5 prefers to adsorb hydrocarbon molecules with richer C-H bonds and larger polarizability, which results in a stronger dispersion force generated by an adsorbent-adsorbate induced polarization effect. Therefore, the selectivity of C4H10/CH4 is up to 180 at 100 kPa, C3H8/CH4 selectivity is 67, and the selectivity of C2H6/CH4 is 13, showing a great potential for separating C2-4 over methane.

Cu-MOFs with Rich Open Metal and F Sites for Separation of C2H2 from CO2 and CH4

Herein, we used the 4-fluoro-[1,1'-biphenyl]-3,4',5-tricarboxylic acid (H₃fbptc) ligand to design and construct a new metal-organic framework (MOF), [Cu₃(fbptc)₂(H₂O)₃]·3NMP (1), which possesses rich accessible metal sites and F functional groups in the porous walls and shows high uptake for C₂H₂ (119.3 cm³ g^-1) and significant adsorption selectivity for C₂H₂ over CH₄ (14.4) and CO₂ (3.6) at 298 K and 100 kPa. In particular, for the gas mixtures of C₂H₂-CH₄ and C₂H₂-CO₂, the MOF reveals large breakthrough time ratios (C₂H₂/CH₄ = 13, C₂H₂/CO₂ = 5.9), which are particularly prominent in dynamic breakthrough experiments, also confirming the excellent potential for the practical separation of C₂H₂ from two-component mixtures (C₂H₂-CH₄ and C₂H₂-CO₂) and even three-component mixtures (C₂H₂-CO₂-CH₄).

Latest insights on separation and storage of carbon compounds in buildings towards sustainable environment: Recent innovations, challenges, future perspectives and application of machine learning

Throughout the past few decades, scientific agencies have paid a lot of attention to environmental issues such as acid rain, water poisoning, and global warming. In order to solve these environmental problems, metal-organic frameworks (MOFs), which are made up of metal ions and/or clusters attached to organic ligands, have shown some promise. With a focus on the usage of MOFs, this paper examines the most recent developments, difficulties, and potential future directions in the separation and storage of carbon compounds in buildings for a sustainable environment. The importance of using MOFs in decarbonizing water systems and lowering environmental concerns in buildings is highlighted in the research. It addresses the most recent developments in the use of MOFs for renewable energy, such as the elimination of dangerous gases like CO2 and CH4 from water systems. The article also looks at how MOFs might be used to decarbonize water systems in structures, with a focus on how carbon-containing compounds are stored chemically and physically using artificial neural network models. MOFs are a potential solution for renewable energy and environmental remediation in buildings because they have special physical and chemical characteristics like adjustable pores, high porosity, and tiny pore size. The report offers insights into existing treatments and invites academics to investigate MOFs' potential for resolving environmental problems in order to create a sustainable environment in buildings.

Construction of defective zirconium-based metal-organic frameworks for enhanced removal of toxic selenite: performance and mechanism studies

The development of effective adsorbents for the adsorption and removal of toxic selenite (SeO₃^2-) from wastewater is urgently required but challenging. Herein, formic acid (FA), a monocarboxylic acid, was used as a template to construct serial defective Zr-Fumarate (Fum) -FA based on a green and facile preparation method. Physicochemical characterization shows that the defect degree of Zr-Fum-FA can be flexibly controlled by regulating the amount of FA to be added. Owing to rich defect units, the diffusion and mass transfer of guest SeO₃^2- into the channel can be boosted. Particularly, Zr-Fum-FA-6 with the most defects exhibits superior adsorption capacity (519.6 mg g^-1) and rapid adsorption equilibrium (∼200 min). The adsorption isotherms and kinetics can be well described by the Langmuir and pseudo-second-order kinetic models. Moreover, this adsorbent possesses excellent resistance towards co-existing ions, high chemical stability and good applicability in a broad pH range of 3-10. Thus, our study provides a promising adsorbent for SeO₃^2-, and more importantly, it proposes a strategy for rationally tailoring the adsorption behavior of adsorbents via defect construction.

Developing Water-Stable Pore-Partitioned Metal-Organic Frameworks with Multi-Level Symmetry for High-Performance Sorption Applications

A new perspective is proposed in the design of pore-space-partitioned MOFs that is focused on ligand symmetry properties sub-divided here into three hierarchical levels: 1) overall ligand, 2) ligand substructure such as backbone or core, and 3) the substituent groups. Different combinations of the above symmetry properties exist. Given the close correlation between nature of chemical moiety and its symmetry, such a unique perspective into ligand symmetry and sub-symmetry in MOF design translates into the influences on MOF properties. Five new MOFs have been prepared that exhibit excellent hydrothermal stability and high-performance adsorption properties with potential applications such as C₃ H₆ /C₂ H₄ and C₂ H₂ /CO₂ selective adsorption. The combination of high stability with high benzene/cyclohexane selectivity of ≈13.7 is also of particular interest.

Enhanced Visible-Light-Responsive Photocatalytic Degradation of Ciprofloxacin by the CuxO/Metal-Organic Framework Hybrid Nanocomposite

Ciprofloxacin (CIP) is a commonly used antibiotic, however, once in the environment, it is highly toxic with a poor biodegradability. Given these attributes, an effective strategy for the removal of CIP is urgently needed for the protection of water resources. Herein, a novel copper metal-organic framework (CuxO/MOF) multifunctional material has been produced, in this work, by the calcination of Cu-MOF urea at 300 °C, in the presence of a 5% H2 atmosphere. The morphological, structural, and thermal properties of the prepared CuxO/MOF were determined through various techniques, and its photocatalytic behavior was investigated for the degradation of CIP under visible-light irradiation. The prepared CuxO/MOF bifunctional material is presented as a graphitic carbon-layered structure with a particle size of 9.2 ± 2.1 nm. The existence of CuO-Cu2O-C, which was found on the CuxO/MOF surface, enhanced the adsorption efficiency and increased the photosensitivity of CuxO/MOF, towards the degradation of CIP in aqueous solutions. The tailored CuxO/MOF, not only shows an excellent CIP degradation efficiency of up to 92% with a constant kinetic rate (kobs) of 0.048 min−1 under visible light, but it can also retain the stable photodegradation efficiency of >85%, for at least six cycles. In addition, CuxO/MOF has an excellent adsorption capacity at pH 6.0 of the maximum Langmuir adsorption capacity of 34.5 mg g−1 for CIP. The results obtained in this study demonstrate that CuxO/MOF is a reliable integrated material and serves as an adsorbent and photocatalyst, which can open a new pathway for the preparation of visible-light-responsive photocatalysts, for the removal of antibiotics and other emerging pollutants.

MIL-101-Cr/Fe/Fe-NH2 for Efficient Separation of CH4 and C3H8 from Simulated Natural Gas

Adsorptive separation based on porous solid adsorbents has emerged as an excellent effective alternative to energy-intensive conventional separation methods in a low energy cost and high working capacity manner. However, there are few stable mesoporous metal-organic frameworks (MOFs) for efficient purification of methane from other light hydrocarbons in natural gas. Herein, we report a series of stable mesoporous MOFs, MIL-101-Cr/Fe/Fe-NH2, for efficient separation of CH4 and C3H8 from a ternary mixture CH4/C2H6/C3H8. Experimental results show that all three MOFs possess excellent thermal, acid/basic, and hydrothermal stability. Single-component adsorption suggested that they have high C3H8 adsorption capacity and commendable selectivity for C3H8 and C2H6 over CH4. Transient breakthrough experiments further certified the ability of direct separation of CH4 from simulated natural gas and indirect recovery of C3H8 from the packing column. Theoretical calculations illustrated that the van der Waals force proportional to the molecular weight is the key factor and that the structural integrity and defect can impact separation performances.

Fluorinated metal-organic frameworks for gas separation

Fluorinated metal-organic frameworks (F-MOFs) as fast-growing porous materials have revolutionized the field of gas separation due to their tunable pore apertures, appealing chemical features, and excellent stability. A deep understanding of their structure-performance relationships is critical for the synthesis and development of new F-MOFs. This critical review has focused on several strategies for the precise design and synthesis of new F-MOFs with structures tuned for specific gas separation purposes. First, the basic principles and concepts of F-MOFs as well as their structure, synthesis and modification and their structure to property relationships are studied. Then, applications of F-MOFs in adsorption and membrane gas separation are discussed. A detailed account of the design and capabilities of F-MOFs for the adsorption of various gases and the governing principles is provided. In addition, the exceptional characteristics of highly stable F-MOFs with engineered pore size and tuned structures are put into perspective to fabricate selective membranes for gas separation. Systematic analysis of the position of F-MOFs in gas separation revealed that F-MOFs are benchmark materials in most of the challenging gas separations. The outlook and future directions of the science and engineering of F-MOFs and their challenges are highlighted to tackle the issues of overcoming the trade-off between capacity/permeability and selectivity for a serious move towards industrialization.

Tandem Reactions over Zeolite-Based Catalysts in Syngas Conversion

Syngas conversion can play a vital role in providing energy and chemical supplies while meeting environmental requirements as the world gradually shifts toward a net-zero. While prospects of this process cannot be doubted, there is a lingering challenge in distinct product selectivity over the bulk transitional metal catalysts. To advance research in this respect, composite catalysts comprising traditional metal catalysts and zeolites have been deployed to distinct product selectivity while suppressing side reactions. Zeolites are common but highly efficient materials used in the chemical industry for hydroprocessing. Combining the advantages of zeolites and some transition metal catalysts has promoted the catalytic production of various hydrocarbons (e.g., light olefins, aromatics, and liquid fuels) and oxygenates (e.g., methanol, dimethyl ether, formic acid, and higher alcohols) from syngas. In this outlook, a thorough revelation on recent progress in syngas conversion to various products over metal-zeolite composite catalysts is validated. The strategies adopted to couple the metal species and zeolite material into a composite as well as the consequential morphologies for specific product selectivity are highlighted. The key zeolite descriptors that influence catalytic performance, such as framework topologies, proximity and confinement effects, acidities and cations, pore systems, and particle sizes are discussed to provide a deep understanding of the significance of zeolites in syngas conversion. Finally, an outlook regarding challenges and opportunities for syngas conversion using zeolite-based catalysts to meet emerging energy and environmental demands is also presented.

Tunable rare-earth metal-organic frameworks for ultra-high selenite capture

Linkers and clusters with various conformations present challenges for the design and prediction of highly porous and stable rare-earth metal-organic frameworks (RE-MOFs) for trapping toxic ions in aqueous solutions. Herein, we designed and synthesized a series of RE-MOFs based on a malleable ligand to explore the effects of ligands, clusters, and configurations on structural stability. The results showed that the nonanuclear high-connected UPC-183 exhibited better stability than the hexanuclear low-connected RE-MOF (UPC-181/182 series). Due to the syngenetic effect of chemi- and physisorption, the adsorption capacity of UPC-183-Eu for selenite (SeO₃^2-) is as high as 308.39 mg/g, recorded one of the highest ever reported for MOFs. Furthermore, we accurately analyzed the adsorption site of UPC-183-Eu for SeO₃^2- through single-crystal structure and theoretical simulation. The ultra-high selenite adsorption capacity and removal efficiency endow UPC-183-Eu an excellent porous adsorbent for removing pollutants.

Efficient Separation of Trace SO2 from SO2/CO2/N2 Mixtures in a Th-Based MOF

The emission of sulfur dioxide (SO₂) from flue gases is harmful since trace SO₂ impairs human health and the natural environment. Therefore, developing new metal organic frameworks (MOFs) to capture this toxic molecule is of great importance in flue gas desulfurization. In this work, we synthesized a new MOF, namely, ECUT-Th-60, which consists of two distinct channels (3.0 Å × 4.1 Å and 2.3 Å × 4.8 Å). It shows SO₂ uptakes of around 2.5 mmol/g at 0.1 kPa and 3.35 mmol/g at 1 bar, which are higher than those of CO₂ and N₂ under identical conditions. Both simulated and experimental breakthrough tests proved that ECUT-Th-60 can separate trace SO₂ from SO₂/CO₂ mixtures. Impressively, complete separation of SO₂ from SO₂/CO₂/N₂ mixtures under both dry and humid conditions was also proved in ECUT-Th-60, predicting its potential application in flue gas desulfurization.

Pore-Window Partitions in Metal-Organic Frameworks for Highly Efficient Reversed Ethylene/Ethane Separations

The development of paraffin-selective adsorbents is desirable but extremely challenging because adsorbents usually prefer olefin over paraffin. Herein, a new pore-window-partition strategy is proposed for the rational design of highly efficient paraffin-preferred metal-organic framework (MOF) adsorbents. The power of this strategy is demonstrated by stepwise installations of linear bidentate N-donor linkers into a prototype MOF (SNNU-201) to produce a series of partitional MOF adsorbents (SNNU-202-204). With continuous pore-window partitions from SNNU-201 to SNNU-204, the isosteric heat of adsorption can be tuned from -34.4 to -19.4 kJ mol^-1 for ethylene and from -25.5 to -20.7 kJ mol^-1 for ethane. Accordingly, partitional MOFs exhibit much higher ethane adsorption capacities, especially for SNNU-204 (104.6 cm³ g^-1), representing nearly 4 times as much ethane as the prototypical counterpart (SNNU-201; 27.5 cm³ g^-1) under ambient conditions. The C₂H₆/C₂H₄ ideal adsorbed solution theory selectivity, dynamic breakthrough experiments, and theoretical simulations further indicate that pore-window partition is a promising and universal strategy for the exploration of highly efficient paraffin-selective MOF adsorbents.

Syntheses of Covalent Organic Frameworks via a One-Pot Suzuki Coupling and Schiff's Base Reaction for C2 H4 /C3 H6 Separation

Covalent organic frameworks (COFs) featuring permanent porosity, designable topologies, and tailorable functionalities have attracted great interest in the past two decades. Developing efficient modular approaches to rationally constructing COFs from a set of molecules via covalent linking has been long pursued. Herein, we report a facile one-pot strategy to prepare COFs via an irreversible Suzuki coupling reaction followed by a reversible Schiff's base reaction without the need for intermediate isolation. Gram-scale ordered frameworks with kgm topology and rich porosities can be obtained by using diamino-aryl halide and dialdehyde aryl-borate compounds as monomers. The resultant microporous CR-COFs were used for efficient C₂ H₄ /C₃ H₆ separation. This strategy reduces the waste generated and efforts consumed by stepwise reactions and relative purification processes, making the large-scale syntheses of stable COFs feasible. Moreover, it offers a novel modular approach to designing COF materials.

A stable and highly luminescent 3D Eu(III)-organic framework for the detection of colchicine in aqueous environment

The metal-organic framework materials have an important application as sensors. In this work, a microporous three-dimensional (3D) Eu(III)-organic framework (Eu-MOF), [Eu₂(3,5-bct)(phen)₂(ox)₂(H₂O)]·H₂O, was constructed from 3,5-bis(3'-carboxyphenyl)-1,2,4-triazole (3,5-H₂bct), oxalate (ox) and 1,10-phenanthroline (phen) as a luminescent sensor. The free volume was found to be 15.7% per unit volume ignoring the free water molecules. The Eu-MOF showed bright red light due to the emission at 622 nm (⁵D₀ → ⁷F₂ transition) of the Eu(III) with high quantum yield (QY, 52.51%). The Eu-MOF exerted high luminescence stability in common organic solvents as well as aqueous solutions within a wide pH range from 4 to 11. Based on the luminescent Eu-MOF, the sensing behavior for colchicine in the aqueous environment was studied. Highly selective and sensitive detection (LOD = 2.43 × 10^-5 mol L^-1) of colchicine was observed by the Eu-MOF even in the presence of potential interfering components. The sensing mechanism for colchicine was investigated by experimental and theoretical results. It is worth noting that a film (Film@Eu-MOF) prepared by loading Eu-MOF showed intense characteristic red light emission under UV light. The luminescence color changed immediately from red to colorless when the Film@Eu-MOF came in contact with colchicine. Highly sensitive and rapid detection of colchicine in wastewater was achieved using this Film@Eu-MOF, which could be identified by the naked eye. The experimental results suggest that the synthesized Eu-MOF has potential application as a luminescent sensing material for pollutants in the environmental system.

Multistimuli-Responsive Materials Based on Zn(II)-Viologen Coordination Polymers and Their Applications in Inkless Print and Anticounterfeiting

Recently, stimuli-responsive materials have attracted great attention, while most of them respond to single or two stimuli. Thus, it is essential to design multifunctional stimuli-responsive materials and develop their applications. The strategy that constructing high-dimensional coordination polymers facilitates the application scope of a viologen-based photochromic system is put forward and confirmed for the first time. Herein, a novel multistimuli-responsive viologen-based Zn-MOF with a two-dimensional framework has been successfully designed and synthesized. Complex 1 exhibits chromic behavior under a variety of external stimuli such as 365 nm UV, X-rays, heat, electricity, and ethylamine. More interestingly, the crystal state of complex 1 displays dual fluorescence and room-temperature phosphorescence (RTP) emission and emits a yellow afterglow when turning off the UV lamp. In addition, Eu(III)-functionalized hybrids, Eu³⁺@Zn-MOF, were prepared by coordinated postsynthetic modification based on viologen complexes for the first time. The sample of Eu³⁺@Zn-MOF inherits the photochromic characteristics of the viologen complexes and gives the distinctive fluorescence of the europium ions. Based on the multicolor switching of 1 and Eu³⁺@Zn-MOF, their possible practical utilization was successfully developed in the fields of inkless, erasable print media, electrochromic information tag printing, information encryption, and anticounterfeiting.

Simultaneous Control of Pore-Space Partition and Charge Distribution in Multi-Modular Metal-Organic Frameworks

We report here a strategy for making anionic pacs type porous materials by combining pore space partition with charge reallocation. The method uses the first negatively charged pore partition ligand (2,5,8-tri-(4-pyridyl)-1,3,4,6,7,9-hexaazaphenalene, H-tph) that simultaneously enables pore partition and charge reallocation. Over two dozen anionic pacs materials have been made to demonstrate their excellent chemical stability and a high degree of tunability. Notably, Ni₃ -bdt-tph (bdt=1,4-benzeneditetrazolate) exhibits month-long water stability, while CoV-bdt-tph sets a new benchmark for C₂ H₂ storage capacity under ambient conditions for ionic MOFs. In addition to tunable in-framework modules, we show feasibility to tune the type and concentration of extra-framework counter cations and their influence on both stability and capability to separate industrial C₃ H₈ /C₃ H₆ and C₆ H₆ /C₆ H₁₂ mixtures.

Identifying UiO-67 Metal-Organic Framework Defects and Binding Sites through Ammonia Adsorption

Ammonia is a widely used toxic industrial chemical that can cause severe respiratory ailments. Therefore, understanding and developing materials for its efficient capture and controlled release is necessary. One such class of materials is 3D porous metal-organic frameworks (MOFs) with exceptional surface areas and robust structures, ideal for gas storage/transport applications. Herein, interactions between ammonia and UiO-67-X (X: H, NH₂ , CH₃ ) zirconium MOFs were studied under cryogenic, ultrahigh vacuum (UHV) conditions using temperature-programmed desorption mass spectrometry (TPD-MS) and in-situ temperature-programmed infrared (TP-IR) spectroscopy. Ammonia was observed to interact with μ₃ -OH groups present on the secondary building unit of UiO-67-X MOFs via hydrogen bonding. TP-IR studies revealed that under cryogenic UHV conditions, UiO-67-X MOFs are stable towards ammonia sorption. Interestingly, an increase in the intensity of the C-H stretching mode of the MOF linkers was detected upon ammonia exposure, attributed to NH-π interactions with linkers. These same binding interactions were observed in grand canonical Monte Carlo simulations. Based on TPD-MS, binding strength of ammonia to three MOFs was determined to be approximately 60 kJ mol^-1 , suggesting physisorption of ammonia to UiO-67-X. In addition, missing linker defect sites, consisting of H₂ O coordinated to Zr⁴⁺ sites, were detected through the formation of nNH₃ ⋅H₂ O clusters, characterized through in-situ IR spectroscopy. Structures consistent with these assignments were identified through density functional theory calculations. Tracking these bands through adsorption on thermally activated MOFs gave insight into the dehydroxylation process of UiO-67 MOFs. This highlights an advantage of using NH₃ for the structural analysis of MOFs and developing an understanding of interactions between ammonia and UiO-67-X zirconium MOFs, while also providing directions for the development of stable materials for efficient toxic gas sorption.

Luminescent binuclear Zinc(II) organic framework as bifunctional water-stable chemosensor for efficient detection of antibiotics and Cr(VI) anions in water

To achieve the ultrastable LMOFs with predominant luminescent sensing performances, the aromatic π-electron mixed ligands strategy was introduced, and the ternary LMOF of {[Zn₂(HDDB)(bib)_1.5]·3H₂O}_n (1), was fabricated based on 3,5-di(2',4'-dicarboxylphenyl)benozoic acid (H₅DDB) and the N-donor of meta-bis(imidazol-1-yl)benzene (bib) under mixed solvothermal condition. LMOF 1 features the first reported 3D 3,4,4-c {6².8³.10}{6².8}₂{6³.8².10}₂ framework with 21.2 % porosity as well as high thermal and chemical stability. Further luminescent sensing showed that LMOF 1 as a bifunctional chemosensor possessing predominant detectability for sensitive detect the hexavalent chromates and nitroimidazoles/nitrofurans antibiotics in water through strong luminescent quenching effects, with excellent reusability as well as trace detection limits. Moreover, luminescent quenching mechanisms were further investigated from electron transfer and energy transfer viewpoints.

Enhanced Sieving of C2-Hydrocarbon from Methane by Fluoro-Functionalization of In-MOF with Robust Stability

Developing efficient adsorbent materials is crucial for adsorption and separation to realize the purification of energy source and raw chemicals. Here, we report a novel and robust 3D In-based MOF built up with fluorine-functionalized ligands, QMOF-2F, with improved separation properties of C2-light hydrocarbons over methane at room temperature respect isoreticular non-fluorinated MOF. QMOF-2F shows a remarkable chemical stability in different solvents, including water, and pH (2-12). DFT calculations support the key role of fluorine-functionalization on the improved performance of QMOF-2F.

Lanthanide-based metal-organic framework materials as bifunctional fluorescence sensors toward acetylacetone and aspartic acid

A family of novel lanthanide-based metal-organic frameworks (Ln-MOFs) with bifunctional fluorescence sensing, namely {[(CH3)2NH2]5[Ln5(TBAPy)5]•solvent}n (Ln = Gd (1), Tb (2), and Dy (3), H4TBAPy = 1,3,5,7-tetra(4-carboxybenzene)pyrene), have been synthesized and...

Recent advances in the applications of porous organic cages

Porous organic cages (POCs) have emerged as a new sub-class of porous materials that stand out by virtue of their tunability, modularity, and processibility. Similar to other porous materials such...

Acetylene Separation by a Ca-MOF Containing Accessible Sites of Open Metal Centers and Organic Groups

Efficient separation of acetylene from a ternary acetylene-containing mixture is an important and vital task in petrochemical industry, which is difficult to achieve using a single material. Herein, a new Ca²⁺-based metal-organic framework (MOF) [Ca(dtztp)_0.5(DMA)]·2H₂O (1) was constructed using the N,O-donor ligand 2,5-di(2H-tetrazol-5-yl)terephthalic acid and the less-studied alkaline earth Ca²⁺ ions. The MOF shows a 3D honeycomb framework based on unique metal-carboxylate-azolate rod secondary building units. Owing to the presence of high-density organic hydrogen-bonding acceptors and open metal sites (OMSs), the activated MOF shows high adsorption capacity for C₂H₂ and selectivity for C₂H₂ over CO₂, C₂H₄, C₂H₆, and CH₄. Dynamic breakthrough experiments indicated the actual C₂H₂ separation potential of the MOF from binary (C₂H₂-C₂H₄ and C₂H₂-CO₂) and ternary (C₂H₂-C₂H₄-CO₂ and C₂H₂-C₂H₄-C₂H₆) mixtures. Simulations revealed that the synergistic interactions between the OMSs and N atoms in MOF and C₂H₂ molecules play an important role in the separation of C₂H₂.

Advanced strategies in Metal-Organic Frameworks for CO2 Capture and Separation

The continuous carbon dioxide (CO₂ ) gas emissions associated with fossil fuel production, valorization, and utilization are serious challenges to the global environment. Therefore, several developments of CO₂ capture, separation, transportation, storage, and valorization have been explored. Consequently, we documented a comprehensive review of the most advanced strategies adopted in metal-organic frameworks (MOFs) for CO₂ capture and separation. The enhancements in CO₂ capture and separation are generally achieved due to the chemistry of MOFs by controlling pore window, pore size, open-metal sites, acidity, chemical doping, post or pre-synthetic modifications. The chemistry of defects engineering, breathing in MOFs, functionalization in MOFs, hydrophobicity, and topology are the salient advanced strategies, recently reported in MOFs for CO₂ capture and separation. Therefore, this review summarizes MOF materials' advancement explaining different strategies and their role in the CO₂ mitigations. The study also provided useful insights into key areas for further investigations.