Selective sorting of polymers with different terminal groups using metal-organic frameworks

High-Precision Separation and Refinement of Fatty Acid Derivatives by Metal-Organic Frameworks

High-precision separation of fatty acid (FA) derivatives is essential for differentiating between structural variations such as E/Z isomerism and unsaturated bond (C═C) positions, which determine their properties and physiological functions. However, current separation and purification methods lack the necessary resolution, efficiency, and scalability. Herein, we report that metal-organic frameworks (MOFs) with configured nanopores enable the precise separation of long-chain FA derivatives. Two pillared-layer-type isoreticular MOFs featuring sub-nanometer channels were employed as adsorbents and stationary phases in liquid chromatography (LC). The MOF-packed LC columns demonstrated high-resolution separation of C18 fatty acid methyl esters (FAMEs), effectively distinguishing E/Z isomers and C═C positional isomers through a nanopore insertion-based recognition mechanism. Thermodynamic analysis and molecular dynamics simulations revealed an unprecedented recognition mechanism for C═C positional isomers, driven by specific multi-site interactions between the functional groups on the FAME chains and the regularly arranged organic ligands within the MOF nanopores. Moreover, MOFs enable the purification of fats and oils (triacylglycerols) by effectively separating them from associated process contaminants that may pose carcinogenic risks to humans. This approach facilitates the scalable and efficient refinement of edible oils, achieving contaminant elimination efficiencies exceeding 99%.

Tailoring zero-point energies in nanocrystalline 3D Hofmann-type spin-crossover networks {Fe1-xMx(pz)[Pd(CN)4]}: impact of size, composition, and surrounding matrices

We report the variation in zero-point energies, and their distribution, investigated through changes in thermal spin relaxation behavior and cooperativity, in the 3D Hofmann-type guest-free, different-sized nanocrystalline spin-crossover coordination networks, {Fe1-xMx(pz)[Pd(CN)4]}, 0 ≤ x ≤ 1, where M(II) = Zn(II), Co(II), and Ni(II). Additionally, we synthesize the [Fe(pz)Pd(CN)4] nanocrystals embedded in different polymeric matrices, including Poly(methyl methacrylate) (PMMA), Polyethylene glycol 6000 (PEG-6000), and Polyvinylpyrrolidone K-30 (PVP K-30). The resulting nanostructures are phase-pure, well-crystallized and exhibit a tetragonal phase. High-resolution transmission electron microscopy (HRTEM) confirms that the nanostructures are nearly square-shaped, with well-defined sizes. The abrupt, incomplete, and gradual nature of the thermal spin relaxation behavior observed from the magnetic data for pure, doped, and polymer-embedded nanocrystals is collectively explained by the local and long-range fluctuations in the crystal fields experienced by the Fe(II) spin-crossover centers, variation in nucleation barrier energy influencing elastic properties, kinetic effects linked to modification in nucleation preferential sites during spin-state switching, as well as chemical pressure, lattice-strains and imperfections, thus altering the in-plane and out-of-plane interactions that influence the cooperativity variation and are responsible for the relative stabilization of the high-spin or low-spin states by modifying the . A 3D mechanoelastic model is employed to interpret the observed magnetic behavior of pure, doped, and polymer-embedded nanocrystals, offering deeper insights into the underlying mechanisms governing spin-state transitions at the nanoscale.

An ecofriendly iron MOF-based immunosensor for sensitive detection of vascular endothelial growth factor in the serum of cancer patients

This work demonstrates the potential of an iron-based metal-organic framework, MIL-100(Fe), to effectively modify a multi-wall carbon nanotube (MWCNT) screen-printed electrode (SPE) for enhanced electrochemical immunosensing of vascular endothelial growth factor (VEGF), which has been recently considered a promising tumor biomarker. MIL-100(Fe) has been synthesized using an ecofriendly, sustainable, heatless water-based technique at various synthesis reaction times. The morphological, structural and electrochemical properties of the different samples of MIL-100(Fe) were evaluated using several physical and electrochemical techniques. MIL-100(Fe) after 48 h has a crystalline microporous-mesoporous structure, with superior properties, that is a larger BET surface area of 1082 ± 18 m2 g-1, a larger pore volume of 0.696 cm3 g-1 and better electroconductivity. After optimizing the experimental conditions, the MIL-100(Fe) 48 h/MWCNTs/SPE-based immunosensor showed a linear range between 100 and 480 pg mL-1, a LOD of 50 pg mL-1 (3σ/S), a sensitivity of 0.017 mA mL pg-1, good reproducibility and high selectivity. In addition, the developed immunosensor was used to satisfactorily detect VEGF in human serum samples of cancer patients, compared to the traditional ELISA method. Considering the sustainable and easy fabrication of the proposed platform, it may provide a promising application as a point-of-care (PoC) device for VEGF detection for diagnosis of cancer.

Hydrophilic Ultra-Fine SiC Nanowires Enhance the Performance of Hydrated Salt Phase-Change Energy Storage Materials

In this study, ultrafine linear nanostructured SiC with high wettability and large specific surface area were synthesized via the carbothermal reduction method. These nanowires were impregnated with Na2SO4 ⋅ 10H2O, CaCl2 ⋅ 6H2O, MgCl2 ⋅ 6H2O, and CaMg2Cl6 ⋅ 12H2O to obtain composite phase change materials (CPCMs), which demonstrated improved phase separation and significantly reduced supercooling. In particular, the supercooling degree of CaCl2 ⋅ 6H2O was minimized to 0.1 °C. The SiC nanowires effectively prevented issues of dehydration and deliquescence in hydrated salts. The thermal storage capacities of the CPCMs exceeded 90 %, with Na2SO4 ⋅ 10H2O and MgCl2 ⋅ 6H2O reaching 107.10 % and 103.35 %, respectively. Furthermore, the CPCMs exhibited greater sensitivity to changes in temperature compared with the pure hydrated salt phase change materials (PCMs). These results indicate that ultra-fine SiC nanowires can act as a versatile carrier for hydrated salt PCMs at low and intermediate temperatures.

Near-identical macromolecules spontaneously partition into concentric circles

Although separation is entropically unfavourable, it is often essential for our life1,2. The separation of very similar macromolecules such as deoxyribonucleic acids (DNAs) and their single nucleotide variants is difficult but holds great advantage for the progress of life science3. Here we report that a particular liquid-liquid phase separation (LLPS) at a solid-liquid interface led to the partitioning of DNAs with nearly identical structures. We found this intriguing phenomenon when we did drop-casting onto a glass plate an aqueous ammonium sulfate dispersion of phase-separated droplets comprising a homogeneous mixture of poly(ethylene glycol) (PEG) samples with different termini. Even when the molecular weights of their PEG parts were identical to each other, terminally different PEGs spread competitively at the solid-liquid interface and partitioned into micrometre-scale concentric circles. We found that this competitive spreading was induced by an ammonium sulfate layer spontaneously formed on the glass surface. We successfully extended the above mechanism to partitioning a mixture of nearly identical DNAs into concentric circles followed by their selective extraction using the salting-in effect. We could isolate a human cancer-causing single nucleotide variant in 97% purity from its 1:1 mixture with the original DNA.

Isolation of Polyethylene Glycol with Larger Molecular Weights via Metal-Organic Frameworks

Polymer products typically present as mixtures with a range of molecular weights, which notably influence the expression of their properties. In this study, a technique is proposed to separate polyethylene glycol (PEG) mixtures of varying molecular weights using metal-organic frameworks (MOFs), thereby narrowing down their molecular weight distribution. Due to the hydrogen bond interactions between PEG and -OH groups in the pores of NU-1000, NU-1000 can selectively adsorb PEG with larger molecular weights from PEG mixture. This separation method consistently yields with narrower molecular weight distribution across multiple cycles. This is the first application of MOFs in regulating the dispersity (Ð) of polymers in solution, providing a novel approach for separating and purifying mixed molecular weight polymers.

Recent advances on metal-organic framework-based electrochemical sensors for determination of organic small molecules

Metal-organic frameworks (MOFs) are an extraordinarily versatile class of porous materials renowned for their intricate three-dimensional skeletal architectures and exceptional chemical properties. These extraordinary attributes have pushed MOFs into the vanguard of diverse disciplines such as microporous conduction, catalysis, separation, biomedical engineering, and electrochemical sensing. The focus of this review is to offer a comprehensive summary of recent advancements in designing MOF-based electrochemical sensors for detecting organic small molecules. offer a comprehensive survey of the recent progress in the methodologies adopted for the construction of MOF composites, covering template-assisted synthesis, Modification in synthesis, and post-synthesis modification. In addition, we discuss the practical application of MOF-based electrochemical sensors in the detection of organic small molecules. Our findings highlight the superior electrochemical sensing capabilities of these novel composites compared to those of their pristine counterparts. In conclusion, we provide a condensed perspective on the potential future trajectories in this domain, underscoring the impetus for continued enquiry and enhancement of MOF composite assemblies. With sustained investigation, the horizon appears bright for electrochemical sensing of small organic molecules and their myriad applications.

Porous Supramolecular Crystalline Probe that Detects Non-Covalent Interactions Involved in Molecular Recognition of Furanic Compounds

Selective separation and conversion of furan-based biomass-derived compounds, which are closely related to biorefineries, is currently an important issue. To improve their performance, it is important to deepen the understanding of non-covalent interactions that act on the molecular recognition of furanic compounds on separation or catalyst matrices. Here, a new method is reported to comprehensively visualize such intermolecular interactions using a porous supramolecular crystalline probe with polar and non-polar binding sites within a low-symmetric nanochannel consisting of four isomeric PdII 3-macrocycles. Single-crystal X-ray diffraction analysis of the crystals including 5-hydroxymethylfurfural, furfural, furfuryl alcohol, or 2-acetylfuran reveals a variety of interactions involving their furan rings and polar substituents. It is also found that cooperative and competitive effects between guest and solvent molecules significantly change their recognition mode.

Detecting single-point isomeric differences in polymer chains by MOF column chromatography

Liquid chromatography with a metal-organic framework (MOF) as the stationary phase enables nanopore threading-based recognition of polymers and identification of single-point isomeric structural differences in the polymer main chain. The polymer adsorption affinity to the MOF and transient kinetics of polymer insertion into the nanopores play crucial roles in the recognition process.

Pyrolytic Depolymerization of Polyolefins Catalysed by Zirconium-based UiO-66 Metal-Organic Frameworks

Polyolefins such as polyethylenes and polypropylenes are the most-produced plastic waste globally, yet are difficult to convert into useful products due to their unreactivity. Pyrolysis is a practical method for large-scale treatment of mixed, contaminated plastic, allowing for their conversion into industrially-relevant petrochemicals. Metal-organic frameworks (MOFs), despite their tremendous utility in heterogeneous catalysis, have been overlooked for polyolefin depolymerization due to their perceived thermal instabilities and inability of polyethylenes and polypropylenes to penetrate their pores. Herein, we demonstrate the viability of UiO-66 MOFs containing coordinatively-unsaturated zirconium nodes, as effective catalysts for pyrolysis that significantly enhances the yields of valuable liquid and gas hydrocarbons, whilst halving the amounts of residual solids produced. Reactions occur on the Lewis-acidic UiO-66 nodes, without the need for noble metals, and yield aliphatic product distributions distinctly different from the aromatic-rich hydrocarbons that can be obtained from zeolite catalysis. We also demonstrate the first unambiguous characterization of polyolefin penetration into UiO-66 pores at pyrolytic temperatures, allowing access to the abundant Zr-oxo nodes within the MOF interior for efficient C-C cleavage. Our work highlights the potential of MOFs as highly-designable heterogeneous catalysts for depolymerisation of plastics, which can complement conventional catalysts in reactivity.

Selective Removal of Denatured Proteins Using MOF Nanopores

Here we present, for the first time, the selective adsorption of denatured proteins using a metal-organic framework (MOF), demonstrating promising potential for protein purification. Typical proteins, such as lysozyme and carbonic anhydrase B, enter the pores of MIL-101 through their narrow apertures when they are denatured to an unfolded state. Selective adsorption is achieved by finely tuning two key features: the sizes of the aperture and cage of the MOF nanopores, which are responsible for sorting unfolded polypeptide chains and inhibiting the translocation of the native form into the pores, respectively. By leveraging this selective adsorption, we successfully purified a mixture of native and denatured proteins by adding MOF to the mixture, achieving a native purity of over 99%.

Metal Organic Frameworks: Current State and Analysis of Their Use as Modifiers of the Vulcanization Process and Properties of Rubber

The interest in and application of metal organic frameworks (MOF) is increasing every year. These substances are widely used in many places, including the separation and storage of gases and energy, catalysis, electrochemistry, optoelectronics, and medicine. Their use in polymer technology is also increasing, focusing mainly on the synthesis of MOF-polymer hybrid compounds. Due to the presence of metal ions in their structure, they can also serve as a component of the crosslinking system used for curing elastomers. This article presents the possibility of using zeolitic imidazolate framework ZIF-8 or MOF-5 as activators for sulfur vulcanization of styrene-butadiene rubber (SBR), replacing zinc oxide in conventional (CV) or effective (EF) curing systems to different extents. Their participation in the curing process and influence on the crosslinking density and structure, as well as the mechanical and thermal properties of the rubber vulcanizates, were examined.

Developing Mixed Matrix Membranes with Good CO2 Separation Performance Based on PEG-Modified UiO-66 MOF and 6FDA-Durene Polyimide

The use of mixed matrix membranes (MMMs) comprising metal-organic frameworks (MOFs) for the separation of CO2 from flue gas has gained recognition as an effective strategy for enhancing gas separation efficiency. When incorporating porous materials like MOFs into a polymeric matrix to create MMMs, the combined characteristics of each constituent typically manifest. Nevertheless, the inadequate dispersion of an inorganic MOF filler within an organic polymer matrix can compromise the compatibility between the filler and matrix. In this context, the aspiration is to develop an MMM that not only exhibits optimal interfacial compatibility between the polymer and filler but also delivers superior gas separation performance, specifically in the efficient extraction of CO2 from flue gas. In this study, we introduce a modification technique involving the grafting of poly(ethylene glycol) diglycidyl ether (PEGDE) onto a UiO-66-NH2 MOF filler (referred to as PEG-MOF), aimed at enhancing its compatibility with the 6FDA-durene matrix. Moreover, the inherent CO2-philic nature of PEGDE is anticipated to enhance the selectivity of CO2 over N2 and CH4. The resultant MMM, incorporating 10 wt% of PEG-MOF loading, exhibits a CO2 permeability of 1671.00 Barrer and a CO2/CH4 selectivity of 22.40. Notably, these values surpass the upper bound reported by Robeson in 2008.

MOF-Thermogel Composites for Differentiated and Sustained Dual Drug Delivery

In recent years, multidrug therapy has gained increasing popularity due to the possibility of achieving synergistic drug action and sequential delivery of different medical payloads for enhanced treatment efficacy. While a number of composite material release platforms have been developed, few combine the bottom-up design versatility of metal-organic frameworks (MOFs) to tailor drug release behavior, with the convenience of temperature-responsive hydrogels (or thermogels) in their unique ease of administration and formulation. Yet, despite their potential, MOF-thermogel composites have been largely overlooked for simultaneous multidrug delivery. Herein, we report the first systematic study of common MOFs (UiO-66, MIL-53(Al), MIL-100(Fe), and MOF-808) with different pore sizes, geometries, and hydrophobicities for their ability to achieve simultaneous dual drug release when embedded within PEG-containing thermogel matrices. After establishing that MOFs exert small influences on the rheological properties of the thermogels despite the penetration of polymers into the MOF pores in solution, the release profiles of ibuprofen and caffeine as model hydrophobic and hydrophilic drugs, respectively, from MOF-thermogel composites were investigated. Through these studies, we elucidated the important role of hydrophobic matching between MOF pores and loaded drugs in order for the MOF component to distinctly influence drug release kinetics. These findings enabled us to identify a viable MOF-thermogel composite containing UiO-66 that showed vastly different release kinetics between ibuprofen and caffeine, enabling temporally differentiated yet sustained simultaneous drug release to be achieved. Finally, the MOF-thermogel composites were shown to be noncytotoxic in vitro, paving the way for these underexploited composite materials to find possible clinical applications for multidrug therapy.

Mid-Infrared Optical Force Chromatography of Microspheres Containing Siloxane Bonds

Recent interest in particle sorting using optical forces has grown due to its ability to separate micro- and nanomaterials based on their optical properties. Here, we present a mid-infrared optical force manipulation technique that enables precise sorting of microspheres based on their molecular vibrational properties using a mid-infrared quantum cascade laser. Utilizing the optical pushing force driven by a 9.3 μm mid-infrared evanescent field generated on a prism through total internal reflection, a variety of microspheres, including those composed of Si-O-Si bonds, can be separated in accordance with their absorbance values at 9.3 μm. The experimental results are in good agreement with the optical force calculations using finite-difference time-domain simulation. Thus, each microsphere's displacement and velocity can be predicted from the absorbance value; conversely, the optical properties (e.g., absorbance and complex refractive index in the mid-infrared region) of individual microspheres can be estimated by monitoring their velocity.

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.

Topological entrapment of macromolecules during the formation of metal-organic framework

Here we present our preliminary results on a novel approach to encapsulate large guest molecules in nanoporous materials, metal-organic frameworks (MOFs), via a newly discovered in situ crystal formation. This method has exciting prospects not only in the design of new organic/inorganic hybrids but also in capturing and separating molecules that are significantly larger than the actual pore size of the host MOF.

Photoinduced movement: how photoirradiation induced the movements of matter

Pioneered by the success on active transport of ions across membranes in 1980 using the regulation of the binding properties of crown ethers with covalently linked photoisomerizable units, extensive studies on the movements by using varied interactions between moving objects and environments have been reported. Photoinduced movements of various objects ranging from molecules, polymers to microscopic particles were discussed from the aspects of the driving for the movements, materials design to achieve the movements and systems design to see and to utilize the movements are summarized in this review.

Foldable Solid-State Batteries Enabled by Electrolyte Mediation in Covalent Organic Frameworks

Solid-state electrolytes with high Li⁺ conductivity, flexibility, durability, and stability offer an attractive solution to enhance safety and energy density. However, meeting these stringent requirements poses challenges to the existing solid polymeric or ceramic electrolytes. Here, an electrolyte-mediated single-Li⁺ -conductive covalent organic framework (COF) is presented, which represents a new category of quality solid-state Li⁺ conductors. In situ solidification of a tailored liquid electrolyte boosts the charge-carrier concentration in the COF channels, decouples Li⁺ cations from both COF walls and molecular chains, and eliminates defects by crystal soldering. Such an altered microenvironment activates the motion of Li⁺ ions in a directional manner, which leads to an increase in Li⁺ conductivity by 100 times with a transference number of 0.85 achieved at room temperature. Moreover, the electrolyte conversion cements the ultrathin COF membrane with fortified mechanical toughness. With the COF membrane, foldable solid-state pouch cells are demonstrated.

Zinc-Based Metal-Organic Frameworks in Drug Delivery, Cell Imaging, and Sensing

The design and structural frameworks for targeted drug delivery of medicinal compounds and improved cell imaging have been developed with several advantages. However, metal-organic frameworks (MOFs) are supplemented tremendously for medical uses with efficient efficacy. These MOFs are considered as an absolutely new class of porous materials, extensively used in drug delivery systems, cell imaging, and detecting the analytes, especially for cancer biomarkers, due to their excellent biocompatibility, easy functionalization, high storage capacity, and excellent biodegradability. While Zn-metal centers in MOFs have been found by enhanced efficient detection and improved drug delivery, these Zn-based MOFs have appeared to be safe as elucidated by different cytotoxicity assays for targeted drug delivery. On the other hand, the MOF-based heterogeneous catalyst is durable and can regenerate multiple times without losing activity. Therefore, as functional carriers for drug delivery, cell imaging, and chemosensory, MOFs' chemical composition and flexible porous structure allowed engineering to improve their medical formulation and functionality. This review summarizes the methodology for fabricating ultrasensitive and selective Zn-MOF-based sensors, as well as their application in early cancer diagnosis and therapy. This review also offers a systematic approach to understanding the development of MOFs as efficient drug carriers and provides new insights on their applications and limitations in utility with possible solutions.

Revisiting molecular adsorption: unconventional uptake of polymer chains from solution into sub-nanoporous media

Adsorption of polymers from the solution phase has been extensively studied to cope with many demands not only for separation technologies, but also for the development of coatings, adhesives, and biocompatible materials. Most studies hitherto focus on adsorption on flat surfaces and mesoporous adsorbents with open frameworks, plausibly because of the preconceived notion that it is unlikely for polymers to enter a pore with a diameter that is smaller than the gyration diameter of the polymer in solution; therefore, sub-nanoporous materials are rarely considered as a polymer adsorption medium. Here we report that polyethylene glycols (PEGs) are adsorbed into sub-nanometer one-dimensional (1D) pores of metal-organic frameworks (MOFs) from various solvents. Isothermal adsorption experiments reveal a unique solvent dependence, which is explained by the balance between polymer solvation propensity for each solvent and enthalpic contributions that compensate for potential entropic losses from uncoiling upon pore admission. In addition, adsorption kinetics identify a peculiar molecular weight (MW) dependence. While short PEGs are adsorbed faster than long ones in single-component adsorption experiments, the opposite trend was observed in double-component competitive experiments. A two-step insertion process consisting of (1) an enthalpy-driven recognition step followed by (2) diffusion regulated infiltration in the restricted 1D channels explains the intriguing selectivity of polymer uptake. Furthermore, liquid chromatography using the MOFs as the stationary phase resulted in significant PEG retention that depends on the MW and temperature. This study provides further insights into the mechanism and thermodynamics behind the present polymer adsorption system, rendering it as a promising method for polymer analysis and separation.

Metal-Organic Frameworks as Versatile Media for Polymer Adsorption and Separation

Molecular recognition is of paramount importance for modern chemical processes and has now been achieved for small molecules using well-established host-guest chemistry and adsorption-science principles. In contrast, technologies for recognizing polymer structure are relatively undeveloped. Conventional polymer separation methods, which are mostly limited in practice to size-exclusion chromatography and reprecipitation, find it difficult to recognize minute structural differences in polymer structures as such small structural alterations barely influence the polymer characteristics, including molecular size, polarity, and solubility. Therefore, most of the polymeric products being used today contain mixtures of polymers with different structures as it is challenging to completely control polymer structures during synthesis even with state-of-the-art substitution and polymerization techniques. In this context, development of novel techniques that can resolve the challenges of polymer recognition and separation is in great demand, as these techniques hold the promise of a new paradigm in polymer synthesis, impacting not only materials chemistry but also analytical and biological chemistry.In biological systems, precise recognition and translation of base monomer sequences of mRNA are achieved by threading them through small ribosome tunnels. This principle of introducing polymers into nanosized channels can possibly help us design powerful polymer recognition and separation technologies using metal-organic frameworks (MOFs) as ideal and highly designable recognition media. MOFs are porous materials comprising organic ligands and metal ions and have been extensively studied as porous beds for gas separation and storage. Recently, we found that MOFs can accommodate large polymeric chains in their nanopores. Polymer chains can spontaneously infiltrate MOFs from neat molten and solution phases by threading their terminals into MOF nanochannels. Polymer structures can be recognized and differentiated due to such insertion processes, resulting in the selective adsorption of polymers on MOFs. This enables the precise recognition of the polymer terminus structure, resulting in the perfect separation of a variety of terminal-functionalized polymers that are otherwise difficult to separate by conventional polymer separation methods. Furthermore, the MOFs can recognize polymer shapes, thus enabling the large-scale separation of high purity cyclic polymers from the complex crude mixtures of linear polymers, which are used as precursor materials in common cyclization reactions. In solution-phase adsorption, many factors, including molecular weight, terminal groups, polymer shape, polymer-MOF interaction, and coexisting solvent molecules, influence the selective adsorption behavior; this yields a new liquid chromatography-based polymer separation technology using an MOF as the stationary phase. MOF-packed columns, in which a novel separation mode based on polymer insertion into the MOF operates under a dynamic insertion/rejection equilibrium at the liquid/solid interface, exhibited excellent polymer separation capability. The polymer recognition principle described in this study thus has a high probability for realizing previously unfeasible polymer separations based on monomer composition and sequences, stereoregularity, regioregularity, helicity, and block sequences in synthetic polymers and biomacromolecules.

Formulation of Metal-Organic Framework-Based Drug Carriers by Controlled Coordination of Methoxy PEG Phosphate: Boosting Colloidal Stability and Redispersibility

Metal-organic framework nanoparticles (nanoMOFs) have been widely studied in biomedical applications. Although substantial efforts have been devoted to the development of biocompatible approaches, the requirement of tedious synthetic steps, toxic reagents, and limitations on the shelf life of nanoparticles in solution are still significant barriers to their translation to clinical use. In this work, we propose a new postsynthetic modification of nanoMOFs with phosphate-functionalized methoxy polyethylene glycol (mPEG-PO3) groups which, when combined with lyophilization, leads to the formation of redispersible solid materials. This approach can serve as a facile and general formulation method for the storage of bare or drug-loaded nanoMOFs. The obtained PEGylated nanoMOFs show stable hydrodynamic diameters, improved colloidal stability, and delayed drug-release kinetics compared to their parent nanoMOFs. Ex situ characterization and computational studies reveal that PEGylation of PCN-222 proceeds in a two-step fashion. Most importantly, the lyophilized, PEGylated nanoMOFs can be completely redispersed in water, avoiding common aggregation issues that have limited the use of MOFs in the biomedical field to the wet form-a critical limitation for their translation to clinical use as these materials can now be stored as dried samples. The in vitro performance of the addition of mPEG-PO3 was confirmed by the improved intracellular stability and delayed drug-release capability, including lower cytotoxicity compared with that of the bare nanoMOFs. Furthermore, z-stack confocal microscopy images reveal the colocalization of bare and PEGylated nanoMOFs. This research highlights a facile PEGylation method with mPEG-PO3, providing new insights into the design of promising nanocarriers for drug delivery.

PEG-stabilized coaxial stacking of two-dimensional covalent organic frameworks for enhanced photocatalytic hydrogen evolution

Two-dimensional covalent organic frameworks (2D COFs) featuring periodic frameworks, extended π-conjugation and layered stacking structures, have emerged as a promising class of materials for photocatalytic hydrogen evolution. Nevertheless, the layer-by-layer assembly in 2D COFs is not stable during the photocatalytic cycling in water, causing disordered stacking and declined activity. Here, we report an innovative strategy to stabilize the ordered arrangement of layered structures in 2D COFs for hydrogen evolution. Polyethylene glycol is filled up in the mesopore channels of a β-ketoenamine-linked COF containing benzothiadiazole moiety. This unique feature suppresses the dislocation of neighbouring layers and retains the columnar π-orbital arrays to facilitate free charge transport. The hydrogen evolution rate is therefore remarkably promoted under visible irradiation compared with that of the pristine COF. This study provides a general post-functionalization strategy for 2D COFs to enhance photocatalytic performances.

Metal-Organic Frameworks for Practical Separation of Cyclic and Linear Polymers

The purification step in the manufacturing of cyclic polymers is difficult as complete fractionation to eliminate linear impurities requires considerable effort. Here, we report a new polymer separation methodology that uses metal-organic frameworks (MOFs) to discriminate between linear and cyclic polyethylene glycols (PEGs) via selective polymer insertion into the MOF nanopores. Preparation of a MOF-packed column allowed analytical and preparative chromatographic separation of these topologically distinct pairs. In addition, gram-scale PEGs with only cyclic structures were successfully obtained from a crude reaction mixture by using MOF as an adsorbent.

A comparative analysis of biochar, activated carbon, expanded graphite, and multi-walled carbon nanotubes with respect to PCM loading and energy-storage capacities

To obtain high thermal performance composite phase change materials (PCMs), various other supporting materials have been utilized to encapsulate organic PCMs. In this study, four carbon materials (biochar, activated carbon, carbon nanotubes, and expanded graphite) were introduced to support heptadecane. The composite PCMs were designed using vacuum impregnation techniques. The structural stability, chemical compatibility, thermal stability, and thermal energy storage capacity of the as-prepared materials were systematically characterized using differential scanning calorimetry, Fourier-transform infrared spectroscopy, etc. Among the supporting materials, expanded graphite had a high PCM content of 94.5%, whereas it was low for biochar-supported PCM (25.7%). Meanwhile, the latent heat storage capacity ranged from 53.3 J/g to 195.9 J/g. It was observed that the intermolecular interactions between the PCM and supporting materials and the surface functionality of the encapsulating agents play a leading role in the thermal performance of the composite PCMs. Furthermore, pore structures such as specific surface area, total pore volume, and pore size distribution have a combined effect on the crystallinity of heptadecane in the composite PCMs. The study will provide insight into developing and designing carbon-based composite PCMs for heat-storage purposes.

Potential utility of HKUST-1-graphite nanocomposite to endow alkane with high thermal properties and low electrical resistivity

It is desirable to develop novel multipurpose phase change materials (PCMs) with improved energy storage and release characteristics. In this study, the utility of a nanocomposite composed of a metal-organic framework (MOF) and graphite was explored for shape-stable PCMs. The prepared MOF-integrated graphite featured favorable structural characteristics (such as large specific surface area (550.6 m²/g), increased total pore volume, and dominant mesopore structure). The obtained composite with a high energy storage capacity (111.4 J/g) exhibited an electrical resistivity that was at least 7 orders of magnitude lower than that of the pristine PCM. In addition, the alkane possessed enhanced chemical compatibility with the supporting scaffolds, outstanding shape, and thermal stabilities. The strong structural connectivity, high specific surface area, and pore size distributions (micro/mesopores) of the scaffolds play a remarkable role in large PCM infiltration ratio, high electrical conductivity, and improved thermal properties of as-prepared composites. It was also suggested that the cavities of the MOF, filled with graphite and the π-π interactions between strand ligands, generate favorable pathways in the nanocomposites. Subsequently creates a supramolecular "wire-like" paths and reduce the resistivity of the parent materials. Therefore, this multifunctional material shows the potential for applications in electro/thermal energy management systems.

Unimolecularly thick monosheets of vinyl polymers fabricated in metal-organic frameworks

Polymers with two-dimensional (2D) network topologies are currently gaining significant attention due to their unique properties that originate from their regulated conformations. However, in contrast to conventional 1D- and 3D-networked macromolecules, the synthesis of such 2D networks provides challenges for polymer chemists because of the nature of the networking polymerisation reaction, which occurs in a spatially random fashion when conventional solution-phase synthesis is performed. Here we report a versatile synthesis of polymeric monosheets with unimolecularly thick networking architectures by exploiting the 2D nanospaces of metal–organic frameworks (MOFs) as reaction templates. Crosslinking radical polymerisation in the 2D nanospaces of pillared-layer-type MOFs affords monosheets of typical vinyl polymers and can be carried out on the gram scale. Remarkably, the prepared polymer monosheets are highly soluble in organic solvents and show atypical thermal and rheological properties that result from their 2D-regulated conformations that cannot be adopted by their 1D or 3D analogues.

Unlike 1D and 3D-networked macromolecules, the synthesis of 2D molecular networks is challenging because of the nature of the polymerisation reaction. Here the authors report the synthesis of polymeric monosheets with unimolecularly thick networks by exploiting the 2D nanospaces of metal–organic frameworks as reaction templates.

Construction of a polyMOF using a polymer ligand bearing the benzenedicarboxylic acid moiety in the side chain

Here we report a new synthetic strategy of a polyMOF consisting of a side chain ligand polymer. The polyMOF was consisting of a crystalline MOF-like structure in the polymer despite its film form.

Metal-Organic Frameworks in Polymer Science: Polymerization Catalysis, Polymerization Environment, and Hybrid Materials

The development of metal-organic frameworks (MOFs) has had a significant impact on various fields of chemistry and materials science. Naturally, polymer science also exploited this novel type of material for various purposes, which is due to the defined porosity, high surface area, and catalytic activity of MOFs. The present review covers various topics of MOF/polymer research beginning with MOF-based polymerization catalysis. Furthermore, polymerization inside MOF pores as well as polymerization of MOF ligands is described, which have a significant effect on polymer structures. Finally, MOF/polymer hybrid and composite materials are highlighted, encompassing a range of material classes, like bulk materials, membranes, and dispersed materials. In the course of the review, various applications of MOF/polymer combinations are discussed (e.g., adsorption, gas separation, drug delivery, catalysis, organic electronics, and stimuli-responsive materials). Finally, past research is concluded and an outlook toward future development is provided.

Fast Ion Transport Pathway Provided by Polyethylene Glycol Confined in Covalent Organic Frameworks

Covalent organic frameworks (COFs) with well-tailored channels are able to accommodate ions and offer their conduction pathway. However, due to strong Coulombic interaction and the lack of transport medium, directly including lithium salts into the channels of COFs results in limited ion transport capability. Herein, we propose a strategy of incorporating low-molecular-weight polyethylene glycol (PEG) into COFs with anionic, neutral, or cationic skeletons to accelerate Li⁺ conduction. The PEG confined in the well-aligned channels retains high flexibility and Li⁺ solvating ability. The ion conductivity of PEG included in a cationic COF can reach 1.78 × 10^-3 S cm^-1 at 120 °C. The simplicity of this strategy as well as the diversity of crystalline porous materials holds great promise to design high-performance all-solid-state ion conductors.