Metal-organic frameworks for separations

Highly-Controlled Soft-Templating Synthesis of Hollow ZIF-8 Nanospheres for Selective CO2 Separation and Storage

Global warming is an ever-rising environmental concern, and carbon dioxide (CO2) is among its major causes. Different technologies, including adsorption, cryogenic separation, and sequestration, have been developed for CO2 separation and storage/utilization. Among these, carbon capture using nano-adsorbents has the advantages of excellent CO2 separation and storage performance as well as superior heat- and mass-transfer characteristics due to their large surface area and pore volume. In this work, an environmentally friendly, facile, bottom-up synthesis of ZIF-8 hollow nanospheres (with reduced chemical consumption) was developed for selective CO2 separation and storage. During this soft-templating synthesis, a combined effect of ultra-sonication and low-temperature hydrothermal synthesis showed better control over an oil-in-water microemulsion formation and the subsequent growth of large-surface-area hollow ZIF-8 nanospheres having excellent particle size distribution. Systematic studies on the synthesis parameters were also performed to achieve fine-tuning of the ZIF-8 crystallinity, hollow structures, and sphere size. The optimized hollow ZIF-8 nanosphere sample having uniform size distribution exhibited remarkable CO2 adsorption capability (∼2.24 mmol g-1 at 0 °C and 1.75 bar), a CO2/N2 separation selectivity of 12.15, a good CO2 storage capacity (1.5-1.75 wt %), and an excellent cyclic adsorption/desorption performance (up to four CO2 adsorption/desorption cycles) at 25 °C. In addition, the samples showed exceptional structural stability with only ∼15% of overall weight loss up to 600 °C under a nitrogen environment. Therefore, the hollow ZIF-8 nanospheres as well as their highly controlled soft-templating synthesis method reported in this work are useful in the course of the development of nanomaterials with optimized properties for future CO2 capture technologies.

Temperature-dependent rearrangement of gas molecules in ultramicroporous materials for tunable adsorption of CO2 and C2H2

The interactions between adsorbed gas molecules within porous metal-organic frameworks are crucial to gas selectivity but remain poorly explored. Here, we report the modulation of packing geometries of CO₂ and C₂H₂ clusters within the ultramicroporous CUK-1 material as a function of temperature. In-situ synchrotron X-ray diffraction reveals a unique temperature-dependent reversal of CO₂ and C₂H₂ adsorption affinities on CUK-1, which is validated by gas sorption and dynamic breakthrough experiments, affording high-purity C₂H₂ (99.95%) from the equimolar mixture of C₂H₂/CO₂ via a one-step purification process. At low temperatures (<253 K), CUK-1 preferentially adsorbs CO₂ with both high selectivity (>10) and capacity (170 cm³ g^-1) owing to the formation of CO₂ tetramers that simultaneously maximize the guest-guest and host-guest interactions. At room temperature, conventionally selective adsorption of C₂H₂ is observed. The selectivity reversal, structural robustness, and facile regeneration of CUK-1 suggest its potential for producing high-purity C₂H₂ by temperature-swing sorption.

Molecular adsorption and self-diffusion of NO2, SO2, and their binary mixture in MIL-47(V) material

The loading dependence of self-diffusion coefficients (Ds) of NO2, SO2, and their equimolar binary mixture in MIL-47(V) have been investigated by using classical molecular dynamics (MD) simulations. The Ds of NO2 are found to be two orders of magnitude greater than SO2 at low loadings and temperatures, and its Ds decreases monotonically with loading. The Ds of SO2 exhibit two diffusion patterns, indicating the specific interaction between the gas molecules and the MIL-47(V) lattice. The maximum activation energy (Ea) in the pure component and in the mixture for SO2 are 16.43 and 18.35 kJ mol-1, and for NO2 are 2.69 and 1.89 kJ mol-1, respectively. It is shown that SO2 requires more amount of energy than NO2 to increase the diffusion rate. The radial distribution functions (RDFs) of gas-gas and gas-lattice indicate that the Oh of MIL-47(V) are preferential adsorption site for both NO2 and SO2 molecules. However, the presence of the hydrogen bonding (HB) interaction between the O of SO2 and the H of MIL-47(V) and also their binding angle (θ(OHC)) of 120° with the linkers of lattice indicate a stronger binding interaction between the SO2 and the MIL-47(V), but it does not occur with NO2. The jump-diffusion of SO2 between adsorption sites within the lattice has been confirmed by the 2D density distribution plots. Moreover, the extraordinarily high Sdiff for NO2/SO2 of 623.4 shows that NO2 can diffuse through the MIL-47(V) significantly faster than SO2, especially at low loading and temperature.

Near-infrared metal agents assisting precision medicine: from strategic design to bioimaging and therapeutic applications

Metal agents have made incredible strides in preclinical research and clinical applications in recent years, but their short emission/absorption wavelengths continue to be a barrier to their distribution, therapeutic action, visual tracking, and efficacy evaluation. Nowadays, the near-infrared window (NIR, 650-1700 nm) provides a more accurate imaging and treatment option. Thus, there has been ongoing research focusing on developing multifunctional NIR metal agents for imaging and therapy that have deeper tissue penetration. The design, characteristics, bioimaging, and therapy of NIR metal agents are covered in this overview of papers and reports published to date. To start with, we focus on describing the structure, design strategies, and photophysical properties of metal agents from the NIR-I (650-1000 nm) to NIR-II (1000-1700 nm) region, in order of molecular metal complexes (MMCs), metal-organic complexes (MOCs), and metal-organic frameworks (MOFs). Next, the biomedical applications brought by these superior photophysical and chemical properties for more accurate imaging and therapy are discussed. Finally, we explore the challenges and prospects of each type of NIR metal agent for future biomedical research and clinical translation.

Reticular Chemistry in Its Chiral Form: Axially Chiral Zr(IV)-Spiro Metal-Organic Framework as a Case Study

The interplay of primary organic ligands and inorganic secondary building units (SBUs) has led to a continual boom of reticular chemistry, particularly metal-organic frameworks (MOFs). Subtle variations of organic ligands can have a significant impact on the ultimate structural topology and consequently, the material's function. However, the role of ligand chirality in reticular chemistry has rarely been explored. In this work, we report the organic ligand chirality-controlled synthesis of two zirconium-based MOFs (Spiro-1 and Spiro-3) with distinct topological structures as well as a temperature-controlled formation of a kinetically stable phase (Spiro-4) based on the carboxylate-functionalized inherently axially chiral 1,1'-spirobiindane-7,7'-phosphoric acid ligand. Specifically, Spiro-1 is a homochiral framework comprising only enantiopure S-spiro ligands and has a unique 4,8-connected sjt topology with large 3D interconnected cavities, while Spiro-3 contains equal amounts of S- and R-spiro ligands, resulting in a racemic framework of 6,12-connected edge-transitive alb topology with narrow channels. Interestingly, the kinetic product Spiro-4 obtained with racemic spiro ligands is built of both hexa- and nona-nuclear zirconium clusters acting as 9- and 6-connected nodes, respectively, giving rise to a newly discovered azs net. Notably, the preinstalled highly hydrophilic phosphoric acid groups combined with large cavity, high porosity, and outstanding chemical stability endow Spiro-1 with remarkable water vapor sorption performance, whereas Spiro-3 and Spiro-4 show poor performances due to inappropriate pore systems and structural fragility upon the water adsorption/desorption process. This work highlights the important role of ligand chirality in manipulating the framework topology and function and would further enrich the development of reticular chemistry.

DigiMOF: A Database of Metal-Organic Framework Synthesis Information Generated via Text Mining

The vastness of materials space, particularly that which is concerned with metal-organic frameworks (MOFs), creates the critical problem of performing efficient identification of promising materials for specific applications. Although high-throughput computational approaches, including the use of machine learning, have been useful in rapid screening and rational design of MOFs, they tend to neglect descriptors related to their synthesis. One way to improve the efficiency of MOF discovery is to data-mine published MOF papers to extract the materials informatics knowledge contained within journal articles. Here, by adapting the chemistry-aware natural language processing tool, ChemDataExtractor (CDE), we generated an open-source database of MOFs focused on their synthetic properties: the DigiMOF database. Using the CDE web scraping package alongside the Cambridge Structural Database (CSD) MOF subset, we automatically downloaded 43,281 unique MOF journal articles, extracted 15,501 unique MOF materials, and text-mined over 52,680 associated properties including the synthesis method, solvent, organic linker, metal precursor, and topology. Additionally, we developed an alternative data extraction technique to obtain and transform the chemical names assigned to each CSD entry in order to determine linker types for each structure in the CSD MOF subset. This data enabled us to match MOFs to a list of known linkers provided by Tokyo Chemical Industry UK Ltd. (TCI) and analyze the cost of these important chemicals. This centralized, structured database reveals the MOF synthetic data embedded within thousands of MOF publications and contains further topology, metal type, accessible surface area, largest cavity diameter, pore limiting diameter, open metal sites, and density calculations for all 3D MOFs in the CSD MOF subset. The DigiMOF database and associated software are publicly available for other researchers to rapidly search for MOFs with specific properties, conduct further analysis of alternative MOF production pathways, and create additional parsers to search for additional desirable properties.

An approach to MOFaxanes by threading ultralong polymers through metal-organic framework microcrystals

Mechanically interlocked architecture has inspired the fabrication of numerous molecular systems, such as rotaxanes, catenanes, molecular knots, and their polymeric analogues. However, to date, the studies in this field have only focused on the molecular-scale integrity and topology of its unique penetrating structure. Thus, the topological material design of such architectures has not been fully explored from the nano- to the macroscopic scale. Here, we propose a supramolecular interlocked system, MOFaxane, comprised of long chain molecules penetrating a microcrystal of metal-organic framework (MOF). In this study, we describe the synthesis of polypseudoMOFaxane that is one of the MOFaxane family. This has a polythreaded structure in which multiple polymer chains thread a single MOF microcrystal, forming a topological network in the bulk state. The topological crosslinking architecture is obtained by simply mixing polymers and MOFs, and displays characteristics distinct from those of conventional polyrotaxane materials, including suppression of unthreading reactions.

Advances in surface-modified nanometal-organic frameworks for drug delivery

Nanometal-organic frameworks (NMOFs) are porous network structures composed of metal ions or metal clusters through self-assembly. NMOFs have been considered as a promising nano-drug delivery system due to their unique properties such as pore and flexible structures, large specific surface areas, surface modifiability, non-toxic and degradable properties. However, NMOFs face a series complex environment during in vivo delivery. Therefore, surface functionalization of NMOFs is vital to ensure that the structure of NMOFs remain stable during delivery, and can overcome physiological barriers to deliver drugs more accurately to specific sites, and achieve controllable release. In this review, the first part summarizes the physiological barriers that NMOFs faced during drug delivery after intravenous injection and oral administration. The second part summarizes the current main ways to load drugs into NMOFs, mainly including pore adsorption, surface attachment, formation of covalent/coordination bonds between drug molecules and NMOFs, and in situ encapsulation. The third part is the main review part of this paper, which summarizes the surface modification methods of NMOFs used in recent years to overcome the physiological barriers and achieve effective drug delivery and disease therapy, which are mainly divided into physical modifications and chemical modifications. Finally, the full text is summarized and prospected, with the hope to provide ideas for the future development of NMOFs as drug delivery.

Solvent-dependent strategy to construct mesoporous Zr-based metal-organic frameworks for high-efficient adsorption of tetracycline

The accumulated antibiotics in the aquatic environment pose great threat to human and ecological health, boosting the development of porous materials for antibiotic removal. Mesoporous metal-organic frameworks (MOFs) have shown great promise in adsorption, which, however, usually need supramolecular design or cooperative template strategy for synthesis. Here we report the successful construction of mesoporous zirconium based metal-organic frameworks (Zr-MOFs) via a simple solvent-dependent strategy. Regulation of the ratio of water to N, N-dimethylacetamide during synthesis determined the porous structure of the synthesized MOFs. Systematic characterizations including SEM, FTIR, XRD and nitrogen sorption isotherm were carried out for structure analysis of the MOFs. With water fraction of 20% (v/v), the obtained Zr-MOF exhibited the highest adsorption capacity (Q_max of 337.0 mg⋅g^-1) towards tetracycline (TC). The adsorption kinetics fitted the pseudo-second-order kinetics, and the adsorption isotherms fitted the Freundlich model well. Adsorption mechanism investigation revealed that the abundant Zr-OH groups stemming from coordination defects mainly accounted for TC adsorption. The hydrogen bonding interaction between TC and Zr-MOF and the generated mesopores contributed to the satisfactory adsorption capacity. This work is anticipated to provide insights on facile synthesis of mesoporous MOFs and application in environmental remediation.

Highly Productive C3H4/C3H6 Trace Separation by a Packing Polymorph of a Layered Hybrid Ultramicroporous Material

Ultramicroporous materials can be highly effective at trace gas separations when they offer a high density of selective binding sites. Herein, we report that sql-NbOFFIVE-bpe-Cu, a new variant of a previously reported ultramicroporous square lattice, sql, topology material, sql-SIFSIX-bpe-Zn, can exist in two polymorphs. These polymorphs, sql-NbOFFIVE-bpe-Cu-AA (AA) and sql-NbOFFIVE-bpe-Cu-AB (AB), exhibit AAAA and ABAB packing of the sql layers, respectively. Whereas NbOFFIVE-bpe-Cu-AA (AA) is isostructural with sql-SIFSIX-bpe-Zn, each exhibiting intrinsic 1D channels, sql-NbOFFIVE-bpe-Cu-AB (AB) has two types of channels, the intrinsic channels and extrinsic channels between the sql networks. Gas and temperature induced transformations of the two polymorphs of sql-NbOFFIVE-bpe-Cu were investigated by pure gas sorption, single-crystal X-ray diffraction (SCXRD), variable temperature powder X-ray diffraction (VT-PXRD), and synchrotron PXRD. We observed that the extrinsic pore structure of AB resulted in properties with potential for selective C3H4/C3H6 separation. Subsequent dynamic gas breakthrough measurements revealed exceptional experimental C3H4/C3H6 selectivity (270) and a new benchmark for productivity (118 mmol g-1) of polymer grade C3H6 (purity >99.99%) from a 1:99 C3H4/C3H6 mixture. Structural analysis, gas sorption studies, and gas adsorption kinetics enabled us to determine that a binding "sweet spot" for C3H4 in the extrinsic pores is behind the benchmark separation performance. Density-functional theory (DFT) calculations and Canonical Monte Carlo (CMC) simulations provided further insight into the binding sites of C3H4 and C3H6 molecules within these two hybrid ultramicroporous materials, HUMs. These results highlight, to our knowledge for the first time, how pore engineering through the study of packing polymorphism in layered materials can dramatically change the separation performance of a physisorbent.

Carbonic Anhydrase-Embedded ZIF-8 Electrospun PVA Fibers as an Excellent Biocatalyst Candidate

There is a growing concern that the increasing concentration of CO₂ in the atmosphere contributes to a potential negative impact on global climate change. To deal with this problem, developing a set of innovative, practical technologies is essential. In the present study, maximizing the CO₂ utilization and precipitation as CaCO₃ was evaluated. In this manner, bovine carbonic anhydrase (BCA) was embedded into the microporous zeolite imidazolate framework, ZIF-8, via physical absorption and encapsulation. Running as crystal seeds, these nanocomposites (enzyme-embedded MOFs) were in situ grown on the cross-linked electrospun polyvinyl alcohol (CPVA). The prepared composites displayed much higher stability against denaturants, high temperatures, and acidic media than free BCA, and BCA immobilized into or on ZIF-8. During 37 days of storage period study, BCA@ZIF-8/CPVA and BCA/ZIF-8/CPVA maintained more than 99 and 75% of their initial activity, respectively. The composition of BCA@ZIF-8 and BCA/ZIF-8 with CPVA improved stability for consecutive usage in recovery reactions, recycling easiness, and greater control over the catalytic process. The amounts of calcium carbonate obtained by one mg each of fresh BCA@ZIF-8/CPVA and BCA/ZIF-8/CPVA were 55.45 and 49.15 mg, respectively. The precipitated calcium carbonate by BCA@ZIF-8/CPVA reached 64.8% of the initial run, while this amount was 43.6% for BCA/ZIF-8/CPVA after eight cycles. These results indicated that the BCA@ZIF-8/CPVA and BCA/ZIF-8/CPVA fibers could be efficiently applied to CO₂ sequestration.

Ortho Effects of Tricarboxylate Linkers in Regulating Topologies of Rare-Earth Metal-Organic Frameworks

A linker design strategy is developed to attain novel polynuclear rare-earth (RE) metal-organic frameworks (MOFs) with unprecedented topologies. We uncover the critical role of ortho-functionalized tricarboxylate ligands in directing the construction of highly connected RE MOFs. The acidity and conformation of the tricarboxylate linkers were altered by substituting with diverse functional groups at the ortho position of the carboxyl groups. For instance, the acidity difference between carboxylate moieties resulted in forming three hexanuclear RE MOFs with novel (3,3,3,10,10)-c wxl, (3,12)-c gmx, and (3,3,3,12)-c joe topologies, respectively. In addition, when a bulky methyl group was introduced, the incompatibility between the net topology and ligand conformation guided the co-appearance of hexanuclear and tetranuclear clusters, generating a novel 3-periodic MOF with a (3,3,8,10)-c kyw net. Interestingly, a fluoro-functionalized linker prompted the formation of two unusual trinuclear clusters and produced a MOF with a fascinating (3,8,10)-c lfg topology, which could be gradually replaced by a more stable tetranuclear MOF with a new (3,12)-c lee topology with extended reaction time. This work enriches the polynuclear clusters library of RE MOFs and unveils new opportunities to construct MOFs with unprecedented structural complexity and vast application potential.

Exclusive Recognition of CO2 from Hydrocarbons by Aluminum Formate with Hydrogen-Confined Pore Cavities

Exclusive capture of carbon dioxide (CO₂) from hydrocarbons via adsorptive separation is an important technology in the petrochemical industry, especially for acetylene (C₂H₂) production. However, the physicochemical similarities between CO₂ and C₂H₂ hamper the development of CO₂-preferential sorbents, and CO₂ is mainly discerned via C recognition with low efficiency. Here, we report that the ultramicroporous material Al(HCOO)₃, ALF, can exclusively capture CO₂ from hydrocarbon mixtures, including those containing C₂H₂ and CH₄. ALF shows a remarkable CO₂ capacity of 86.2 cm³ g^-1 and record-high CO₂/C₂H₂ and CO₂/CH₄ uptake ratios. The inverse CO₂/C₂H₂ separation and exclusive CO₂ capture performance from hydrocarbons are validated via adsorption isotherms and dynamic breakthrough experiments. Notably, the hydrogen-confined pore cavities with appropriate dimensional size provide an ideal pore chemistry to specifically match CO₂ via a hydrogen bonding mechanism, with all hydrocarbons rejected. This molecular recognition mechanism is unveiled by in situ Fourier-transform infrared spectroscopy, X-ray diffraction studies, and molecular simulations.

Effect of Functional Groups on Low-Concentration Carbon Dioxide Capture in -Type Metal-Organic Frameworks

The selective capture of low-concentration CO₂ from air or confined spaces remains a great challenge. In this study, various functional groups were introduced into UiO-66 to generate functionalized derivatives (UiO-66-R, R = NO₂, NH₂, OH, and CH₃), aiming at significantly enhancing CO₂ adsorption and separation efficiency. More significantly, UiO-66-NO₂ and UiO-66-NH₂ with high polarity exhibit exceptional CO₂ affinity and optimal separation characteristics in mixed CO₂/O₂/N₂ (1:21:78). In addition, the impressive stability of UiO-66-NO₂ and UiO-66-NH₂ endows them with excellent recycling stability. The effective adsorption and separation performances demonstrated by these two functional materials suggest their potential as promising physical adsorbents for capturing low-concentration CO₂.

ZIF-62 glass foam self-supported membranes to address CH4/N2 separations

Membranes with ultrahigh permeance and practical selectivity could greatly decrease the cost of difficult industrial gas separations, such as CH₄/N₂ separation. Advanced membranes made from porous materials, such as metal-organic frameworks, can achieve a good gas separation performance, although they are typically formed on support layers or mixed with polymeric matrices, placing limitations on gas permeance. Here an amorphous glass foam, a_gfZIF-62, wherein a, g and f denote amorphous, glass and foam, respectively, was synthesized by a polymer-thermal-decomposition-assisted melting strategy, starting from a crystalline zeolitic imidazolate framework, ZIF-62. The thermal decomposition of incorporated low-molecular-weight polyethyleneimine evolves CO₂, NH₃ and H₂O gases, creating a large number and variety of pores. This greatly increases pore interconnectivity but maintains the crystalline ZIF-62 ultramicropores, allowing ultrahigh gas permeance and good selectivity. A self-supported circular a_gfZIF-62 with a thickness of 200-330 µm and area of 8.55 cm² was used for membrane separation. The membranes perform well, showing a CH₄ permeance of 30,000-50,000 gas permeance units, approximately two orders of magnitude higher than that of other reported membranes, with good CH₄/N₂ selectivity (4-6).

Nanoscale Adsorption, Assembly, and Deionization Dynamics Recorded by Optical Fiber Sensors

Capacitive deionization in environmental decontamination has been widely studied and now requires intensive development to support large-scale deployment. Porous nanomaterials have been demonstrated to play pivotal roles in determining decontamination efficiency and manipulating nanomaterials to form functional architecture has been one of the most exciting challenges. Such nanostructure engineering and environmental applications highlight the importance of observing, recording, and studying basically electrical-assisted charge/ion/particle adsorption and assembly behaviors localized at charged interfaces. In addition, it is generally desirable to increase the sorption capacity and reduce the energy cost, which increase the requirement for recording collective dynamic and performance properties that stem from nanoscale deionization dynamics. Herein, we show how a single optical fiber can serve as an in situ and multifunctional opto-electrochemical platform for addressing these issues. The surface plasmon resonance signals allow the in situ spectral observation of nanoscale dynamic behaviors at the electrode-electrolyte interface. The parallel and complementary optical-electrical sensing signals enable the single probe but multifunctional recording of electrokinetic phenomena and electrosorption processes. As a proof of concept, we experimentally decipher the interfacial adsorption and assembly behaviors of anisotropic metal-organic framework nanoparticles at a charged surface and decouple the interfacial capacitive deionization within an assembled metal-organic framework nanocoating by visualizing its dynamic and energy consumption properties, including the adsorptive capacity, removal efficiency, kinetic properties, charge, specific energy consumption, and charge efficiency. This simple "all-in-fiber" opto-electrochemical platform offers intriguing opportunities to provide in situ and multidimensional insights into interfacial adsorption, assembly, and deionization dynamics information, which may contribute to understanding the underlying assembly rules and the exploring structure-deionization performance correlations for the development of tailor-made nanohybrid electrode coatings for deionization applications.

Solid-phase extraction and separation of indium with P2O4-UiO-66-MOFs (di-2-ethylhexyl phosphoric acid-UiO-66-metal-organic frameworks)

Compared with the traditional liquid-liquid extraction method, solid-phase extraction agents are of great significance for the recovery of indium metal due to their convenience, free of organic solvents, and fully exposed activity. In this study, P₂O₄ (di-2-ethylhexyl phosphoric acid) was chemically modified by using UiO-66 to form the solid-phase extraction agent P₂O₄-UiO-66-MOFs (di-2-ethylhexyl phosphoric acid-UiO-66-metal-organic frameworks) to adsorb In(III). The results show that the Zr of UiO-66 bonds with the P-OH of P₂O₄ to form a composite P₂O₄-UiO-66-MOF, which was confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The adsorption process of indium on P₂O₄-UiO-66-MOFs followed pseudo first-order kinetics, and the adsorption isotherms fit the Langmuir adsorption isotherm model. The adsorption capabilities can reach 192.8 mg/g. After five consecutive cycles of adsorption-desorption-regeneration, the indium adsorption capacity by P₂O₄-UiO-66-MOFs remained above 99%. The adsorption mechanism analysis showed that the P=O and P-OH of P₂O₄ molecules coated on the surface of P₂O₄-UiO-66-MOFs participated in the adsorption reaction of indium. In this paper, the extractant P₂O₄ was modified into solid P₂O₄-UiO-66-MOFs for the first time. This work provides a new idea for the development of solid-phase extractants for the recovery of indium.

Chiral metal-organic frameworks and their composites as stationary phases for liquid chromatography chiral separation: A minireview

Chiral metal organic frameworks (CMOFs) are a kind of crystal porous framework material that has attracted increasing attention due to the customizable combination of metal nodes and organic ligands. In particular, the highly ordered crystal structure and rich adjustable chiral structure make it a promising material for developing new chiral separation material systems. In this review, the progress of CMOFs and their different types of composites used as chiral stationary phases (CSPs) in liquid chromatography for enantioseparation are discussed. The characteristics of CMOFs and their composites are summarized, aiming to provide new ideas for the development of CMOFs with better performance and further promote the application of CMOFs materials in enantioselective high-performance liquid chromatography (HPLC).

Quinoid-Based Three-Dimensional Metal-Organic Framework Fe2(dhbq)3: Porosity, Electrical Conductivity, and Solid-State Redox Properties

We report the synthesis, characterization, and electronic properties of the quinoid-based three-dimensional metal-organic framework [Fe₂(dhbq)₃]. The MOF was synthesized without using cations as a template, unlike other reported X₂dhbq₃-based coordination polymers, and the crystal structure was determined by using single-crystal X-ray diffraction. The crystal structure was entirely different from the other reported [Fe₂(X₂dhbq₃)]^2-; three independent 3D polymers were interpenetrated to give the overall structure. The absence of cations led to a microporous structure, investigated by N₂ adsorption isotherms. Temperature dependence of electrical conductivity data revealed that it exhibited a relatively high electrical conductivity of 1.2 × 10^-2 S cm^-1 (E_a = 212 meV) due to extended d-π conjugation in a three-dimensional network. Thermoelectromotive force measurement revealed that it is an n-type semiconductor with electrons as the majority of charge carriers. Structural characterization and spectroscopic analyses, including SXRD, Mössbauer, UV-vis-NIR, IR, and XANES measurements, evidenced the occurrence of no mixed valency based on the metal and the ligand. [Fe₂(dhbq)₃] upon incorporating as a cathode material for lithium-ion batteries engendered an initial discharge capacity of 322 mAh/g.

Post-Synthetic Cyano-ferrate(II) Functionalization of a Metal-Organic Framework, NU-1000

Starting with ferrocyanide ions in acidic aqueous solution, cyano-ferrate(II) species are post-synthetically grafted to the nodes of a mesoporous zirconium-based MOF, NU-1000. As indicated by single-crystal X-ray crystallography, grafting occurs by substitution of cyanide ligands by node-based hydroxo and oxo ligands rather than by substitution of node aqua ligands by cyanide ligands as bridges between Fe(II) and Zr(IV). The installed moieties yield a broad absorption band that is tentatively ascribed to iron-to-zirconium charge transfer. Consistent with Fe(III/II) redox activity, a modest fraction of the installed iron complexes are directly electrochemically addressable.

Integrating Self-Partitioned Pore Space and Amine Functionality into an Aromatic-Rich Coordination Framework with Ph Stability for Effective Purification of C2 Hydrocarbons

A great demand for high-purity C₂ hydrocarbons calls for the development of chemically stable porous materials for the effective isolation of C₂ hydrocarbons from CH₄ and CO₂. However, such separations are challenged by their similar physiochemical parameters and have not been systematically studied to date. In this work, we reported a cadmium-based rod-packing coordination framework compound ZJNU-140 of a new 5,6,7-c topology built up from a custom-designed tricarboxylate ligand. The metal-organic framework (MOF) features an aromatic-abundant pore surface, uncoordinated amine functionality, and self-partitioned pore space of suitable size. These structural characteristics act synergistically to provide the MOF with both selective recognition ability and the confinement effect toward C₂ hydrocarbons. As a result, the MOF displays promising potential for adsorptive separation of C₂-CH₄ and C₂-CO₂ mixtures. The IAST-predicted C₂/CH₄ and C₂/CO₂ adsorption selectivities, respectively, fall in the ranges of 7.3-10.2 and 2.1-2.9 at 298 K and 109 kPa. The real separation performance was also confirmed by dynamic breakthrough experiments. In addition, the MOF can maintain skeleton intactness in aqueous solutions with a wide pH range of 3-11, as confirmed by powder X-ray diffraction (PXRD) and isotherm measurements, showing no loss of framework integrity and porosity. The excellent hydrostability, considerable uptake capacity, impressive adsorption selectivity, and mild regeneration make ZJNU-140 a promising adsorbent material applied for the separation and purification of C₂ hydrocarbons.

Engineering Metal-Organic Frameworks for Selective Separation of Hexane Isomers Using 3-Dimensional Linkers

Metal-organic frameworks (MOFs) are highly tunable materials with potential for use as porous media in non-thermal adsorption or membrane-based separations. However, many separations target molecules with sub-angstrom differences in size, requiring precise control over the pore size. Herein, we demonstrate that this precise control can be achieved by installing a three-dimensional linker in an MOF with one-dimensional channels. Specifically, we synthesized single crystals and bulk powder of NU-2002, an isostructural framework to MIL-53 with bicyclo[1.1.1]pentane-1,3-dicarboxylic acid as the organic linker component. Using variable-temperature X-ray diffraction studies, we show that increasing linker dimensionality limits structural breathing relative to MIL-53. Furthermore, single-component adsorption isotherms demonstrate the efficacy of this material for separating hexane isomers based on the different sizes and shapes of these isomers.

Ratiometric luminescent sensing of a biomarker for sugar consumption in an aqueous medium using a Cu(II) coordination polymer

An innovative [Cu(Hadp)₂(Bimb)]_n (KA@CP-S3) coordination polymer expands its dimensionality from a 1D chain to a 2D network. The topological analysis reveals that KA@CP-S3 has 2-connected uninodal 2D 2C1 topology. KA@CP-S3 has capable luminescent sensing for volatile organic compounds (VOCs), nitroaromatics, heavy metal ions, anions, disposed antibiotics (nitrofurantoin and tetracycline) and biomarkers. Intriguingly, KA@CP-S3 exhibits outstanding selective quenching of about 90.7% and 90.5% for the 125 mg dl^-1 and 150 mg dl^-1 strengths of sucrose, respectively, in aqueous solution along with other ranges in between. The photocatalytic degradation efficiency of KA@CP-S3 for the potentially harmful organic dye Bromophenol Blue displays 95.4%, which is the highest among the 13 dyes that were evaluated.

Sintering Metal-Organic Framework Gels for Application as Structural Adhesives

Metal-organic frameworks (MOFs)/coordination polymers are promising materials for gas separation, fuel storage, catalysis, and biopharmaceuticals. However, most applied research on MOFs is limited to these functional materials thus far. This study focuses on the potential of MOFs as structural adhesives. A sintering technique is applied to a zeolitic imidazolate framework-67 (ZIF-67) gel that enables the joining of Cu substrates, resulting in a shear strength of over 30 MPa, which is comparable to that of conventional structural adhesives. Additionally, systematic experiments are performed to evaluate the effects of temperature and pressure on adhesion, indicating that the removal of excess 2-methylimidazole and the by-product (acetic acid) from the sintered material by vaporization results in a microstructure composed of large spherical ZIF-67 crystals that are densely aggregated, which is essential for achieving a high shear strength.

Formation of Gold Nanoclusters from Goldcarbonyl Chloride inside the Metal-Organic Framework HKUST-1

Gas-phase infiltration of the carbonylchloridogold(I), Au(CO)Cl precursor into the pores of HKUST-1 ([Cu3(BTC)2(H2O)2], Cu-BTC) SURMOFs (surface-mounted metal-organic frameworks; BTC = benzene-1,3,5-tricarboxylate) leads to Au(CO)Cl decomposition within the MOF through hydrolysis with the aqua ligands on Cu. Small Aux clusters with an average atom number of x ≈ 5 are formed in the medium-sized pores of the HKUST-1 matrix. These gold nanoclusters are homogeneously distributed and crystallographically ordered, which was supported by simulations of the powder X-ray diffractometric characterization. Aux@HKUST-1 was further characterized by scanning electron microscopy (SEM) and infrared reflection absorption (IRRA) as well as Raman spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma optical emission spectroscopy (ICP-OES).

Computational design of the novel building blocks for the metal-organic frameworks based on the organic ligand protected Cu4 cluster

Metal-organic frameworks (MOFs) are tunable porous network compounds composed of inorganic nodes bound by various organic linkers. Here we report the density functional theory (DFT) study of the MOF novel building blocks made of the Cu4 clusters protected by four organic ligands having two phenyl rings and terminated either with Cl or Br atom (precursors 1 and 2, respectively). The research was performed both in the gas phase and with the implicit effects of acetonitrile included, with two functionals, B3LYP and PBE, both with and without the second-order dispersion correction. We analyzed the structural features of the precursors 1 and 2, their electronic structures, molecular electrostatic potential (MEP) distribution, and global reactivity parameters (GRPs). Both functionals resulted in the singlets of the precursors 1 and 2 as the most stable species. The precursor structures optimized with the hybrid functional were found to be quite similar for both halogens, both containing somewhat distorted from planarity Cu4 cluster, with the outer phenyls of the ligands rotated relative to the inner phenyls. With both halogens and both DFT approaches, the frontier molecular orbitals (FMOs) of the precursors 1 and 2 were shown to have quite similar compositions. The change of the substituent from Br to Cl was found to cause slight stabilizations or destabilizations of the HOMOs and LUMOs. The central parts and especially the inner phenyl ring parts of the precursors 1 and 2 were suggested to play a role of nucleophile in various chemical reactions due to the significant accumulation of negative electrostatic potential. Also, weak intermolecular interactions might exist between the ligands of neighboring precursor molecules. Finally, with both substituents the precursors 1 and 2 should be relatively unreactive and demonstrate thermodynamic stability. Further, the precursors 1 and 2 should be quite stable in oxidation reactions and more active in reduction processes. Generally, the substituent nature was shown not to affect significantly the reactivity of the precursors 1 and 2, as well as their other properties.

Scalable Green Synthesis of Robust Ultra-Microporous Hofmann Clathrate Material with Record C3 H6 Storage Density for Efficient C3 H6 /C3 H8 Separation

Developing porous materials for C₃ H₆ /C₃ H₈ separation faces the challenge of merging excellent separation performance with high stability and easy scalability of synthesis. Herein, we report a robust Hofmann clathrate material (ZJU-75a), featuring high-density strong binding sites to achieve all the above requirements. ZJU-75a adsorbs large amount of C₃ H₆ with a record high storage density of 0.818 g mL^-1 , and concurrently shows high C₃ H₆ /C₃ H₈ selectivity (54.2) at 296 K and 1 bar. Single-crystal structure analysis unveil that the high-density binding sites in ZJU-75a not only provide much stronger interactions with C₃ H₆ but also enable the dense packing of C₃ H₆ . Breakthrough experiments on gas mixtures afford both high separation factor of 14.7 and large C₃ H₆ uptake (2.79 mmol g^-1 ). This material is highly stable and can be easily produced at kilogram-scale using a green synthesis method, making it as a benchmark material to address major challenges for industrial C₃ H₆ /C₃ H₈ separation.

Ligand Substitution: An Effective Way for Tuning Structures of ZIF-7 Nanoparticles (NPs) and Improving Energy Recovery Performance of ZIF/PA TFN Membranes

It is an important initiative to reduce the building energy consumption using energy recovering ventilation (ERV) systems. The application of ERV systems is hindered by the low CO₂ barrier performance of commercial total heat exchange membranes (THEMs) that lead to unsatisfactory indoor air refreshing rate, and there is an urgent need for THEMs that have improved CO₂ barrier properties and effective energy recovery efficiencies. Here, we report the formation of novel ZIF/PA TFN THEMs based on ZIF-7-X nanoparticles (NPs) with "core-shell" structures and tunable particle sizes, formed from benzimidazole (BIM) ligands and BIM substituted by -NH₂, -CH₃, -C₂H₅, and -C₃H₇ functional groups. The NPs were mixed with pyr omellitic triformyl chloride (TMC) in the organic phase during the interface polymerization process to form ZIF/PA TFN membranes. The total heat exchange performance of ZIF/PA TFN membranes could be effectively modified by the type and quantity of ZIF-7-X NPs added. The CO₂ barrier properties and water vapor permeability of ZIF/PA TFN membranes could be improved by the addition of optimal levels of ZIF-7-X NPs, showing low CO₂ permeance of 7.76 GPU, high H₂O permeance of 663.8 GPU, and excellent enthalpy exchange efficiency of 72.1%. This work provided an effective strategy for tuning not only the nanostructures of ZIF-7 fillers but also the CO₂ barrier properties of the formed ZIF/PA TFN membranes.

Engineering DNA Crystals toward Studying DNA-Guest Molecule Interactions

Sequence-selective recognition of DNA duplexes is important for a wide range of applications including regulating gene expression, drug development, and genome editing. Many small molecules can bind DNA duplexes with sequence selectivity. It remains as a challenge how to reliably and conveniently obtain the detailed structural information on DNA-molecule interactions because such information is critically needed for understanding the underlying rules of DNA-molecule interactions. If those rules were understood, we could design molecules to recognize DNA duplexes with a sequence preference and intervene in related biological processes, such as disease treatment. Here, we have demonstrated that DNA crystal engineering is a potential solution. A molecule-binding DNA sequence is engineered to self-assemble into highly ordered DNA crystals. An X-ray crystallographic study of molecule-DNA cocrystals reveals the structural details on how the molecule interacts with the DNA duplex. In this approach, the DNA will serve two functions: (1) being part of the molecule to be studied and (2) forming the crystal lattice. It is conceivable that this method will be a general method for studying drug/peptide-DNA interactions. The resulting DNA crystals may also find use as separation matrices, as hosts for catalysts, and as media for material storage.

Highly Selective Separation of C2H2/CO2 and C2H2/C2H4 in an N-Rich Cage-Based Microporous Metal-Organic Framework

The separation of acetylene (C2H2) from carbon dioxide (CO2) and the purification of ethylene (C2H4) from C2H2 are quite essential processes for the chemical industry. However, these processes are challenging due to their similar physical properties, including molecule sizes and boiling points. Herein, we report an N-rich cage-based microporous metal-organic framework (MOF), [Cd5(Tz)9](NO3) (termed as Cd-TZ, TZ stands for tetrazole), and its highly efficient separation of C2H2/CO2 and C2H2/C2H4. Single-component gas adsorption isotherms reveal that Cd-TZ exhibits high C2H2 adsorption capacity (3.10 mmol g-1 at 298 K and 1 bar). The N-rich cages in Cd-TZ can trap C2H2 with a higher isosteric heat of adsorption (40.8 kJ mol-1) than CO2 and C2H4 owing to the robust host-guest interactions between the noncoordinated N atoms and C2H2, which has been verified by molecular modeling studies. Cd-TZ shows a high IAST selectivity for C2H2/CO2 (8.3) and C2H2/C2H4 (13.3). The breakthrough simulations confirm the potential for separating C2H2/CO2 and the purification of C2H4 from C2H2.

A Robust Molecular Porous Material for C2 H2 /CO2 Separation

A molecular porous material, MPM-2, comprised of cationic [Ni₂ (AlF₆ )(pzH)₈ (H₂ O)₂ ] and anionic [Ni₂ Al₂ F₁₁ (pzH)₈ (H₂ O)₂ ] complexes that generate a charge-assisted hydrogen-bonded network with pcu topology is reported. The packing in MPM-2 is sustained by multiple interionic hydrogen bonding interactions that afford ultramicroporous channels between dense layers of anionic units. MPM-2 is found to exhibit excellent stability in water (>1 year). Unlike most hydrogen-bonded organic frameworks which typically show poor stability in organic solvents, MPM-2 exhibited excellent stability with respect to various organic solvents for at least two days. MPM-2 is found to be permanently porous with gas sorption isotherms at 298 K revealing a strong affinity for C₂ H₂ over CO₂ thanks to a high (ΔQ_st )_AC [Q_st (C₂ H₂ ) - Q_st (CO₂ )] of 13.7 kJ mol^-1 at low coverage. Dynamic column breakthrough experiments on MPM-2 demonstrated the separation of C₂ H₂ from a 1:1 C₂ H₂ /CO₂ mixture at 298 K with effluent CO₂ purity of 99.995% and C₂ H₂ purity of >95% after temperature-programmed desorption. C-H···F interactions between C₂ H₂ molecules and F atoms of AlF₆ ^3- are found to enable high selectivity toward C₂ H₂ , as determined by density functional theory simulations.

Strengthening Intraframework Interaction within Flexible MOFs Demonstrates Simultaneous Sieving Acetylene from Ethylene and Carbon Dioxide

Efficient separation of acetylene (C₂ H₂ )/ethylene (C₂ H₄ ) and acetylene/carbon dioxide (CO₂ ) by adsorption is an industrially promising process, but adsorbents capable of simultaneously capturing trace acetylene from ethylene and carbon dioxide are scarce. Herein, a gate-opening effect on three isomorphous flexible metal-organic frameworks (MOFs) named Co(4-DPDS)₂ MO₄ (M = Cr, Mo, W; 4-DPDS = 4,4-dipyridyldisulfide) is modulated by anion pillars substitution. The shortest CrO₄ ^2- strengthens intraframework hydrogen bonding and thus blocks structural transformation after activation, striking a good balance among working capacity, separation selectivity, and trace impurity removal of flexible MOFs out of nearly C₂ H₂ /C₂ H₄ and C₂ H₂ /CO₂ molecular sieving. The exceptional separation performance of Co(4-DPDS)₂ CrO₄ is confirmed by dynamic breakthrough experiments. It reveals the specific threshold pressures control in anion-pillared flexible materials enabled elimination of the impurity leakage to realize high purity products through precise control of the intraframework interaction. The adsorption mechanism and multimode structural transformation property are revealed by both calculations and crystallography studies. This work demonstrates the feasibility of modulating flexibility for controlling gate-opening effect, especially for some cases of significant aperture shrinkage after activation.

Amide Functionalized Mesoporous MOF LOCOM-1 as a Stable Highly Active Basic Catalyst for Knoevenagel Condensation Reaction

Acyl-amide is extensively used as functional group and is a superior contender for the design of MOFs with the guest accessible functional organic sites. A novel acyl-amide-containing tetracarboxylate ligand, bis(3,5-dicarboxy-pheny1)terephthalamide, has been successfully synthesized. The H₄L linker has some fascinating attributes as follows: (i) four carboxylate moieties as the coordination sites confirm affluent coordination approaches to figure a diversity of structure; (ii) two acyl-amide groups as the guest interaction sites can engender guest molecules integrated into the MOF networks through H-bonding interfaces and have a possibility to act as functional organic sites for the condensation reaction. A mesoporous MOF ([Cu₂(L)(H₂O)₃]·4DMF·6H₂O) has been prepared in order to produce the amide FOS within the MOF, which will work as guest accessible sites. The prepared MOF was characterized by CHN analysis, PXRD, FTIR spectroscopy, and SEM analysis. The MOF showed superior catalytic activity for Knoevenagel condensation. The catalytic system endures a broad variety of the functional groups and presents high to modest yields of aldehydes containing electron withdrawing groups (4-chloro, 4-fluoro, 4-nitro), offering a yield > 98 in less reaction time as compared to aldehydes with electron donationg groups (4-methyl). The amide decorated MOF (LOCOM-1-) as a heterogeneous catalyst can be simply recovered by centrifugation and recycled again without a flagrant loss of its catalytic efficiency.

Collaboration of two-star nanomaterials: The applications of nanocellulose-based metal organic frameworks composites

Nanocellulose, as the star nanomaterial in carbohydrate polymers, has excellent mechanical properties, biodegradability, and easy chemical modification. However, further practical applications of nanocellulose are limited by their inadequate functionalization. Metal-organic frameworks (MOFs), as the star nanomaterial in functional polymers, have a large surface area, high porosity, and adjustable structure. The collaboration of nanocellulose and MOFs is a desirable strategy to make composites especially interesting for multifunctional and multi-field applications. What sparks will be produced by the collaboration of two-star nanomaterials? In this review article, we highlight an up-to-date overview of nanocellulose-based MOFs composites. The sewage treatment, gas separation, energy storage, and biomedical applications are mainly summarized. Finally, the challenges and research trends of nanocellulose-based MOFs composites are prospected. We hope this review may provide a valuable reference for the development and applications of carbohydrate polymer composites soon.

Electrodeposition of Ag/ZIF-8-Modified Membrane for Water Remediation

Metal-organic framework (MOF)-based membranes have been widely used in gas and liquid separation due to their porous structures and tunable compositions. Depending on the guest components, heterostructured MOFs can exhibit multiple functions. In the present work, we report a facile and rapid preparation of zeolitic imidazolate framework-8 (ZIF-8) and silver nanoparticle incorporated ZIF-8 (Ag/ZIF-8)-based membranes on stainless-steel mesh (SSM) through a "green" electrodeposition method. The SSM was first coated with a Zn-plated layer which contains mainly zinc hydroxide nitrate (Zn₅(OH)₈(NO₃)₂·2H₂O) with a "leaf-like" morphology, providing anchoring points for the deposition of ZIF-8 and Ag/ZIF-8. It takes only 10 min to prepare a uniform coating of Zn₅(OH)₈(NO₃)₂·2H₂O in aqueous conditions without the use of a strong base; this is by far the most efficient way of making zinc hydroxide nitrate nanocrystals. Following a similar electrodeposition approach, ZIF-8 and Ag/ZIF-8-coated SSM can be prepared within 20 min by applying a small current. The encapsulation of Ag does not alter the chemical composition nor the crystal structure of ZIF-8. The resulting ZIF-8 and Ag/ZIF-8-coated SSM have been tested for their effectiveness for rhodamine B dye removal in a fast vacuum filtration setting. Additionally, growth of E. coli was significantly inhibited after overnight incubation with Ag/ZIF-8-coated SSM. Overall, we demonstrate a fast synthesis procedure to make ZIF-8 and Ag/ZIF-8-coated SSM membranes for organic dye removal with excellent antimicrobial activity.

Molecular Engineering of Metal-Organic Layers for Sustainable Tandem and Synergistic Photocatalysis

Metal-organic layers (MOLs), a monolayered version of metal-organic frameworks (MOFs), have recently emerged as a novel two-dimensional molecular material platform to design multifunctional catalysts. MOLs inherit the intrinsic molecular tunability of MOFs and yet have more accessible and modifiable building blocks. Here we report molecular engineering of six MOLs via modulated solvothermal synthesis between HfCl4 and three photosensitizing ligands followed by postsynthetic modification with two carboxylate-containing cobaloximes for tandem and synergistic photocatalysis. Morphological and structural characterization by transmission electron microscopy and atomic force microscopy and compositional analysis by inductively coupled plasma-mass spectrometry and nuclear magnetic resonance spectroscopy establish the MOLs as flat nanoplates with a periodic lattice structure of hexagonal symmetry. The MOLs efficiently catalyze tandem dehydrogenative coupling reactions and synergistic Heck-type coupling reactions. The most active MOL catalyst was used for the gram-scale synthesis of vesnarinone, a cardiotonic agent, in 80% yield with a turnover number of 400 and in eight consecutive reaction cycles without significant loss of activities.

In Silico High-Throughput Design and Prediction of Structural and Electronic Properties of Low-Dimensional Metal-Organic Frameworks

The advent of π-stacked layered metal-organic frameworks (MOFs), which offer electrical conductivity on top of permanent porosity and high surface area, opened up new horizons for designing compact MOF-based devices such as battery electrodes, supercapacitors, and spintronics. Permutation of structural building blocks, including metal nodes and organic linkers, in these electrically conductive (EC) materials, results in new systems with unprecedented and unexplored physical and chemical properties. With the ultimate goal of providing a platform for accelerated material design and discovery, here we lay the foundations for the creation of the first comprehensive database of EC-MOFs with an experimentally guided approach. The first phase of this database, coined EC-MOF/Phase-I, is composed of 1,057 bulk and monolayer structures built by all possible combinations of experimentally reported organic linkers, functional groups, and metal nodes. A high-throughput screening (HTS) workflow is constructed to implement density functional theory calculations with periodic boundary conditions to optimize the structures and calculate some of their most relevant properties. Because research and development in the area of EC-MOFs has long been suffering from the lack of appropriate initial crystal structures, all of the geometries and property data have been made available for the use of the community through an online platform that was developed during the course of this work. This database provides comprehensive physical and chemical data of EC-MOFs as well as the convenience of selecting appropriate materials for specific applications, thus accelerating the design and discovery of EC-MOF-based compact devices.

Explosive and pollutant nitroaromatic sensing through a Cd(II) based ladder shaped 1D coordination polymer

In the existing leanings of environmental and national security issues, establishment of appropriate sensors for explosive as well as pollutant nitroaromatic compounds may be considered as one of the most prodigious job for material researchers. In the current study a new Cd(II) based 1D ladder coordination polymer (CP), [Cd(4-bpd)(3-cbn)₂]_n, has been synthesized and well characterized through single crystal X-ray diffraction analysis. Interestingly, the supramolecular assembly of this compound has efficiently identified 2,4,6-trinitrophenol through fluorescence quenching method. The Stern-Volmer coefficient (K_sv) has been calculated as 6.047 × 10³ M^-1, which can be attributed to the quenching of the emission intensity. The limit of detection (LOD) has been determined as 0.260 μM following the 3σ method along with almost 95% fluorescence intensity reduction. FESEM study revealed that the crystalline nature of the compound has been altered upon interaction with the above mentioned nitroaromatic analyte. Theoretical studies were performed to get the insight idea of fluorescence quenching mechanism which also substantiated the experimental observation. The present study can pave the way for the fabrication of future generation technology in sensor field.

A novel flower-shaped Ag@ZIF-67 chemiluminescence sensor for sensitive detection of CEA

In this work, a chemiluminescence (CL) aptasensor for sensitive carcinoembryonic antigen (CEA) detection was constructed based on the CL system of luminol-H₂O₂-NaOH. Magnetic carbon nanotubes (MCNTs), as the base material, was modified with CEA-aptamer and DNA1, and was combined with the novel flower-shaped Ag@ZIF-67 of modified with DNA2 through the principle of base complementary pairing. CEA combined with aptamer when it existed in the solution. At the same time, MCNTs was adsorbed at the bottom of the container under the influence of external magnetic field, and Ag@ZIF-67 enhanced the CL signal. The CL aptasensor demonstrated high selectivity and sensitivity for CEA in human serum sample with (1-4): a detection limit of 4.53 × 10^-3 ng/mL in case the detection range was 0.05-500 ng/mL. Furthermore, the proposed method had been shown great potential in cancer diagnosis.

Solvent-free mechanochemical multicomponent preparation of 4H-pyrans catalyzed by Cu2(NH2-BDC)2(DABCO) metal-organic framework

4H-pyrans have been prepared through a mechanochemical multicomponent reaction (MCR) of different aldehydes, malononitrile, and various 1,3-dicarbonyl compounds, catalyzed by an amine-functionalized metal-organic framework (MOF) Cu₂(NH₂-BDC)₂(DABCO) as a heterogeneous catalyst with good to excellent yields.

Creating hierarchical pores in metal-organic frameworks via postsynthetic reactions

Metal-organic frameworks (MOFs) demonstrate promise for a multitude of applications owing to their high porosity and surface area. However, the majority of conventional MOFs possess only micropores with very limited accessibility to substances larger than 2 nm-especially functional biomacromolecules like some proteins. It is challenging to create an appropriately large pore size while avoiding framework collapse in MOFs. Herein, we present the generation of mesopores in microporous MOFs through three facile and effective techniques, namely Soxhlet washing, linker hydrolysis and linker thermolysis. These postsynthetic elimination approaches have been applied in selected MOFs, including PCN-250, PCN-160 and UiO-66, and controllably generate MOFs with hierarchical pores and high stability. Our work demonstrates reproducible and straightforward methods resulting in hierarchically porous materials that possess the benefits of mesoporosity while borrowing the robustness of a micropore framework. All the procedures can be conducted reliably at a multigram scale and operation time less than 6 h, representing a significant effort in the field of MOF synthesis. These hierarchically porous MOFs show great promise in a wide range of applications as efficient adsorbents, catalysts and drug carriers.

Programmed Polarizability Engineering in a Cyclen-Based Cubic Zr(IV) Metal-Organic Framework to Boost Xe/Kr Separation

Efficient separation of xenon (Xe) and krypton (Kr) mixtures through vacuum swing adsorption (VSA) is considered the most attractive route to reduce energy consumption, but discriminating between these two gases is difficult due to their similar properties. In this work, we report a cubic zirconium-based MOF (Zr-MOF) platform, denoted as NU-1107, capable of achieving selective separation of Xe/Kr by post-synthetically engineering framework polarizability in a programmable manner. Specifically, the tetratopic linkers in NU-1107 feature tetradentate cyclen cores that are capable of chelating a variety of transition-metal ions, affording a sequence of metal-docked cationic isostructural Zr-MOFs. NU-1107-Ag(I), which features the strongest framework polarizability among this series, achieves the best performance for a 20:80 v/v Xe/Kr mixture at 298 K and 1.0 bar with an ideal adsorbed solution theory (IAST) predicted selectivity of 13.4, placing it among the highest performing MOF materials reported to date. Notably, the Xe/Kr separation performance for NU-1107-Ag(I) is significantly better than that of the isoreticular, porphyrin-based MOF-525-Ag(II), highlighting how the cyclen core can generate relatively stronger framework polarizability through the formation of low-valent Ag(I) species and polarizable counteranions. Density functional theory (DFT) calculations corroborate these experimental results and suggest strong interactions between Xe and exposed Ag(I) sites in NU-1107-Ag(I). Finally, we validated this framework polarizability regulation approach by demonstrating the effectiveness of NU-1107-Ag(I) toward C₃H₆/C₃H₈ separation, indicating that this generalizable strategy can facilitate the bespoke synthesis of polarized porous materials for targeted separations.

Morphology control through the synthesis of metal-organic frameworks

Designable morphology and predictable properties are the most challenging goals in material engineering. Features such as shape, size, porosity, agglomeration ratio significantly affect the final properties of metal-organic frameworks (MOFs) and can be regulated throughout synthesis parameters but require a deep understanding of the mechanisms of MOFs formation. Herein, we systematically summarize the effects of the individual synthesis factors, such as pH of reaction mixture, including acidic or basic character of modulators, temperature, solvents types, surfactants type and content and ionic liquids on the morphology of growing MOFs. We identified main mechanisms of MOFs' growth leading to different morphology of final particles and next systematically discuss the effect of miscellaneous parameters on MOFs morphology based on the main mechanisms related to the nucleation, growth and formation of final MOFs structure, including coordination modulation, protonation/deprotonation acting and modulation by surfactants or capping agents. The effect of microwaves and ultrasound employment during synthesis is also considered due to their affecting especially nucleation and particles growing steps during MOFs formation.