Pure Metal-organic Framework Research Articles

Imparting functionality into porphyrin metal–organic framework aerogels with uniform distributions for diversified applications

The incorporation of various functional nanoentities into pure metal–organic framework (MOF) aerogels can not only introduce additional functionality but also expands the application scenarios of MOF aerogels. Herein, a general and simple strategy for uniform incorporation of various functional nanomaterials into a porphyrin MOF aerogel is presented. Specifically, this strategy primarily involves the introduction of a surfactant polyvinylpyrrolidone (PVP) to disperse the nanomaterials in lipophilic solvents, followed by a direct solvothermal reaction with the precursors of the porphyrin MOF aerogel. Additionally, uniform aerogel composites consisting of two MOF components have also been developed by careful optimizing the reaction conditions. The resulting nanoentity@MOF aerogel composites exhibit positive properties that stem from the synergistic effects between the nanoentities and MOF aerogel, offering advanced applications in areas such as photochemical electrochemistry, adsorption and photodegradation, electrochemical oxygen reduction reaction, and fluorescence.

Synthesis of a MOF derived porous graphene and pyrolytic carbon supported zinc stannate nanohybrid electrode with enhanced lithium-ion storage performances

Compositing nano-sized zinc stannate (Zn2SnO4) with supportive carbon skeleton usually brings in improved lithium-ion storage performances. One of the most challenging tasks is to effectively stabilize Zn2SnO4 nanocrystals via simplified preparation routes from eco-friendly raw materials. In this work, the water-soluble natural molecule gallic acid (GA) is directly employed to coordinate with Zn2+/Sn2+ ions, and the corresponding metal-organic framework (MOF) precursor samples of pure Zn-GA MOF and bimetallic ZnSn-GA MOF can be synthesized. The Zn-GA MOF and ZnSn-GA MOF precursors are further converted to a three-dimensional (3D) porous graphene sample (ZMG) and a pyrolytic carbon domain supported Zn2SnO4 nanocomposite (Zn2SnO4@C), respectively, by taking the advantages of the unique micro-structures and compositions of MOF materials. By rationally mixing the ZMG and Zn2SnO4@C in electrode fabrication, the finally obtained Zn2SnO4@C/ZMG nanohybrid electrode exhibits a high reversible capacity of 1117 mAh·g−1 after 500 cycles at a current density of 1000 mA g−1 in half-cells as well as inspiring full-cell performance. The favorable synergistic effect in lithium-ion storage for the Zn2SnO4@C/ZMG electrode has been investigated. The MOF derived samples and involved sustainable synthesis protocols can be further developed for wider applications.

Fabrication Methods of Continuous Pure Metal-Organic Framework Membranes and Films: A Review.

Metal-organic frameworks (MOFs) have drawn intensive attention as a class of highly porous, crystalline materials with significant potential in various applications due to their tunable porosity, large internal surface areas, and high crystallinity. This paper comprehensively reviews the fabrication methods of pure MOF membranes and films, including in situ solvothermal synthesis, secondary growth, electrochemical deposition, counter diffusion growth, liquid phase epitaxy and solvent-free synthesis in the category of different MOF families with specific metal species, including Zn-based, Cu-based, Zr-based, Al-based, Ni-based, and Ti-based MOFs.

N-doped CuFe-MOF-919 derivatives in activation of peroxymonosulfate for enhanced degradation of organic pollutants: 1O2 dominated non-radical pathway

Metal organic framework (MOF)-derived carbon materials have received significant attention as catalysts for peroxymonosulfate (PMS)-mediated degradation of organic pollutants. Despite the growing interest, the challenge persists in designing MOF derivatives where non-radicals serve as the primary active species. This study introduces an N-doped carbon-based material denoted as CuFe@NC-10, featuring highly dispersed Cu and Fe bimetallic active sites. The design involves co-doping MOF-919(Fe) with melamine. Under identical experimental conditions, CuFe@NC-10 exhibited remarkable performance, degrading 99.5 % of Rhodamine B (RhB) within 30 min, with a mineralization rate of 60 %. Notably, the pseudo-primary kinetic constant was 5.8 times higher than that observed for the pure MOF derivative (CuFe@NC). CuFe@NC-10 displayed consistent activation capacity across a broad pH range, and its catalytic performance remained largely unaffected by the coexistence of inorganic anions and humic acid. Quenching experiments and electron paramagnetic resonance (EPR) analysis indicated that singlet oxygen (1O2) primarily drove RhB degradation. X-ray photoelectron spectroscopy (XPS) findings suggested that the valence transition between Cu and Fe facilitated 1O2 generation, confirming PMS as the primary source of 1O2. The RhB degradation pathway was deduced through Q Exactive mass spectrometer and density-functional theory (DFT) calculations. Additionally, the study evaluated the ecotoxicity of RhB and its intermediates, providing essential insights into ecological risks associated with its degradation.

Application of Raman and chemometrics to the mechanochemical synthesis of 4,4-bipyridine/cobalt based MOF using twin screw extrusion

The process optimization of 4,4-bipyridine based metal organic framework (MOF) synthesis by twin screw extrusion (TSE) is investigated using cobalt nitrate hexahydrate (Co(NO3)2·6H2O) as the metal precursor. The effects of operating parameters including liquid to solid ratio (L/S), screw speed and feeding rate on the product composition are examined. The collected MOF samples were characterized offline by powder X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, and scanning electron microscopy. It was found that the explored feeding and screw rates are insufficient to generate a pure MOF. However the MOF product was obtained using an optimum L/S ratio i.e., 0.5, which improved the wettability and mixing of reactants to allow effective interactions at a molecular level, facilitating the complete reaction inside the extruder. Partial least square based multivariate analysis of the collected Raman spectra was used to obtain predictive models to quantify MOF purity, which reached a maximum of 87.0 wt% using 0.5 L/S, 100 g/h feeding rate and 100 rpm screw speed.

In Situ Grown Cu‐Metal–Organic Frameworks on Graphitic Carbon Nitride (g‐C3N4) as an Efficient Bifunctional Electrocatalyst for Water Splitting

Creating an economical, and highly active catalyst poses the greatest challenge in achieving an effective water‐splitting process. To address this challenge, investigating metal–organic framework (MOF) materials holds immense promise. However, pure MOFs show limited conductivity, and durability for water splitting. This research aims to study modifying pure MOF with 2D material to alter the morphology and the electrocatalytic capabilities of both compounds, benefiting from the synergistic interplay between the two constituent materials. The authors have devised a synthesis strategy to modify the nanoscale Cu‐MOF‐based catalyst with graphitic carbon nitride (g‐C3N4). Hybrids of 5, 10, and 15 mg of g‐C3N4 embedded in Cu–MOF are prepared and studied for over all water‐splitting in alkaline media. 15 mg g‐C3N4 hybrid needs only 131 mV of overpotential at 10 mA cm−2 and has a Tafel value of 59 mV dec−1. This also shows very good OER performance needing only 185 mV of overpotential and a Tafel value of 53 mV dec−1 and is stable for a more extended period. The improved performance can be attributed to exposed active sites, increased ability of charge transfer, highly porous nanostructure, and high stability. The results indicate that hybrids combining MOFs with 2D material hold great potential as economical and effective electrocatalysts for comprehensive water splitting.

Metal-Organic Framework Gels for Adsorption and Catalytic Detoxification of Chemical Warfare Agents: A Review.

Chemical warfare agents (CWAs) have brought great threats to human life and social stability, and it is critical to investigate protective materials. MOF (metal-organic framework) gels are a class with an extended MOF architecture that are mainly formed using metal-ligand coordination as an effective force to drive gelation, and these gels combine the unique characteristics of MOFs and organic gel materials. They have the advantages of a hierarchically porous structure, a large specific surface area, machinable block structures and rich metal active sites, which inherently meet the requirements for adsorption and catalytic detoxification of CWAs. A series of advances have been made in the adsorption and catalytic detoxification of MOF gels as chemical warfare agents; however, overall, they are still in their infancy. This review briefly introduces the latest advances in MOF gels, including pure MOF gels and MOF composite gels, and discusses the application of MOF gels in the adsorption and catalytic detoxification of CWAs. Meanwhile, the influence of microstructures (pore structures, metal active site, etc.) on the detoxification performance of protective materials is also discussed, which is of great significance in the exploration of high-efficiency protective materials. Finally, the review looks ahead to next priorities. Hopefully, this review can inspire more and more researchers to enrich the performance of MOF gels for applications in chemical protection and other purification and detoxification processes.

Synthesis of Aluminum-Based Metal-Organic Framework (MOF)-Derived Carbon Nanomaterials and Their Water Adsorption Isotherm.

The characteristics of water vapor adsorption depend on the structure, porosity, and functional groups of the material. Metal-organic framework (MOF)-derived carbon (MDC) is a novel material that exhibits a high specific area and tunable pore sizes by exploiting the stable structure and porosity of pure MOF materials. Herein, two types of aluminum-based MOFs were used as precursors to synthesize hydrophobic microporous C-MDC and micro-mesoporous A-MDC via carbonization and activation depending on the type of ligands in the precursors. C-MDC and A-MDC have different pore characteristics and exhibit distinct water adsorption properties. C-MDC with hydrophobic properties and micropores exhibited negligible water adsorption (108.54 mgg-1) at relatively low pressures (P/P0~0.3) but showed a rapid increase in water adsorption ability (475.7 mgg-1) at relative pressures of about 0.6. A comparison with the isotherm model indicated that the results were consistent with the theories, which include site filling at low relative pressure and pore filling at high relative pressure. In particular, the Do-Do model specialized for type 5 showed excellent agreement.

Engineering Metal-Organic-Framework (MOF)-Based Membranes for Gas and Liquid Separation.

Separation is one of the most energy-intensive processes in the chemical industry, and membrane-based separation technology contributes significantly to energy conservation and emission reduction. Additionally, metal-organic framework (MOF) materials have been widely investigated and have been found to have enormous potential in membrane separation due to their uniform pore size and high designability. Notably, pure MOF films and MOF mixed matrix membranes (MMMs) are the core of the "next generation" MOF materials. However, there are some tough issues with MOF-based membranes that affect separation performance. For pure MOF membranes, problems such as framework flexibility, defects, and grain orientation need to be addressed. Meanwhile, there still exist bottlenecks for MMMs such as MOF aggregation, plasticization and aging of the polymer matrix, poor interface compatibility, etc. Herein, corresponding methods are introduced to solve these problems, including inhibiting framework flexibility, regulating synthesis conditions, and enhancing the interaction between MOF and substrate. A series of high-quality MOF-based membranes have been obtained based on these techniques. Overall, these membranes revealed desired separation performance in both gas separation (e.g., CO2, H2, and olefin/paraffin) and liquid separation (e.g., water purification, organic solvent nanofiltration, and chiral separation).

Development of carbon nanotube-metal organic framework (MOF) hybrid antiviral microfiltration membrane

We present the development of novel antiviral membranes by immobilizing metal organic framework (MOF) and carbon nanotubes (CNTs) on polymeric microfiltration membranes. The CNTs and the copper-based MOF (HKUST-1) were tested individually and in a hybrid form (MOF-CNT) against MS2 bacteriophage which was used as a surrogate virus. The membranes were synthesized at three different loading (5, 8 and 12% by weight) on a PVDF filtration membrane. The membranes were characterized using scanning electron microscopy, energy dispersive x-ray spectroscopy, thermogravimetric analysis, water contact angle, gas permeation tests and x-ray diffraction. Amongst the CNT immobilized (CNIM), MOF immobilized (MIM) and MOF-CNT (MCNIM) immobilized membranes, the permeate flux was highest for the CNIM (170% higher than MIM at 5% loading) followed by MCNIM (149% higher than MIM at 5% loading). This was because the small MOF particles blocked the membrane pores. No rejection of bacteriophages was observed with the plain PVDF membrane, but with the immobilization of MOF and CNTs, the antiviral activities increased with nano particles loading. The MCNIM with 12% loading exhibited a 99.6% phage deactivation. Kinetics of phage deactivation was studied for MOF, CNTs and MOF-CNT. The median lethal dose to kill 50% of the virus population (LD50) for MOF-CNT was as much as 70% lower than the CNTs and 30% lower than the pure MOF. Similarly, the time taken to deactivate 80% of the viral population (T80) for MOF-CNT was 50% less than the pure CNTs and 24% less than the pure MOF. Overall, the MOF-CNT immobilized membranes appear to be best option for antiviral activity.

Fabrication of MIL-125 Membrane with Unprecedented CO2/N2 Selectivity Using Ti6-oxo Cluster Source

Using metal-oxo clusters as metal source of metal–organic framework (MOF) membranes warrants not only more precise control over their multiscale structure but also milder reaction conditions for maintaining membrane continuity. In this study, a Ti6-oxo cluster was utilized as the titanium source of Ti-MOF membranes. Compared with the Ti8-oxo cluster precursor, which resulted in the fabrication of MIL-125(Ti) membranes via ligand exchange, employing a Ti6-oxo cluster source resulted in more precise control over epitaxial growth kinetics of MIL-125(Ti) seeds and, therefore, the formation of well-intergrown c-oriented MIL-125(Ti) membranes with higher linker deficiencies in the framework. Gas permeation results revealed an ideal CO2/N2 selectivity of 52.7, which ranked the highest among pure MOF membranes tested under similar conditions, thereby showing great promise for efficient CO2 capture from flue gases.

A LDH Template Triggers the Formation of a Highly Compact MIL‐53 Metal‐Organic Framework Membrane for Acid Upgrading

AbstractHighly compact metal–organic framework (MOF) membranes offer hope for the ambition to cope with challenging separation scenarios with industrial implications. A continuous layer of layered double hydroxide (LDH) nanoflakes on an alumina support as a template triggered a chemical self‐conversion to a MIL‐53 membrane, with approximately 8 hexagonal lattices (LDH) traded for 1 orthorhombic lattice (MIL‐53). With the sacrifice of the template, the availability of Al nutrients from the alumina support was dynamically regulated, which resulted in synergy for producing membranes with highly compact architecture. The membrane can realize nearly complete dewatering from formic acid and acetic acid solutions, respectively, and maintain stability in a continuous pervaporation over 200 h. This is the first success in directly applying a pure MOF membrane to such a corrosive chemical environment (lowest pH value of 0.81). The energy consumption is saved by up to 77 % when compared with the traditional distillation.

A LDH Template Triggers the Formation of a Highly Compact MIL-53 Metal-Organic Framework Membrane for Acid Upgrading.

Highly compact metal-organic framework (MOF) membranes offer hope for the ambition to cope with challenging separation scenarios with industrial implications. A continuous layer of layered double hydroxide (LDH) nanoflakes on an alumina support as a template triggered a chemical self-conversion to a MIL-53 membrane, with approximately 8 hexagonal lattices (LDH) traded for 1 orthorhombic lattice (MIL-53). With the sacrifice of the template, the availability of Al nutrients from the alumina support was dynamically regulated, which resulted in synergy for producing membranes with highly compact architecture. The membrane can realize nearly complete dewatering from formic acid and acetic acid solutions, respectively, and maintain stability in a continuous pervaporation over 200 h. This is the first success in directly applying a pure MOF membrane to such a corrosive chemical environment (lowest pH value of 0.81). The energy consumption is saved by up to 77 % when compared with the traditional distillation.

Fabrication of Hierarchically Porous CuBTC@PA-PEI Composite for High-Efficiency Elimination of Cyanogen Chloride.

Cyanogen chloride (CNCl) is highly toxic and volatile, and it is difficult to effectively remove via porous substances such as activated carbon due to the weak interaction between CNCl and the adsorbent surface. Developing a highly effective elimination material against CNCl is of great importance in military chemical protection. In this work, a new metal-organic framework (MOF) CuBTC@PA-PEI (polyacrylate-polyethyleneimine) composite was prepared and exhibited excellent CNCl elimination performance in the breakthrough tests. PEI was used for the functionalization of PA with amino groups, which is beneficial to anchor with metal ions of MOF. Afterward, the growth of MOF occurred on the surface and in the pores of the matrix by molecular self-assembly via our newly proposed stepwise impregnation layer-by-layer growth method. Breakthrough tests were performed to evaluate the elimination performance of the composites against CNCl. Compared with the pristine CuBTC powder, the CuBTC@PA-PEI composite exhibited better adsorption capacity and a longer breakthrough time. By compounding with the PA matrix, a hierarchically porous structure of CuBTC@PA-PEI composite was constructed, which provides a solution to the mass transfer problem of pure microporous MOF materials. It also solves the problems of MOF molding and lays a foundation for the practical application of MOF.

Template‐assisted Preparation of Self‐standing 2D‐MOF Membranes for Application in Cascade Reactions

AbstractSelf‐standing metal‐organic framework (MOF) membranes open up several application areas where their use in the powder form is either not possible or non‐sustainable. Most MOF membranes are prepared as a thin layer either on a supporting substrate or used as a composite membrane with additional supporting material. In this work, we present the preparation procedure for making highly stable, easy‐to‐handle, reusable, efficient pure MOF membranes (UiO‐66‐SO3H and UiO‐66‐NH2 membranes; thickness 240±12 μm and 265±10 μm, respectively) with hollow fiber morphology and their use in cascade reactions in one‐pot catalyzed by incompatible acid‐base in tea‐bag‐type concept. The catalytic performance of the catalyst membranes was tested by reacting benzaldehyde dimethyl acetal with three active methylene compounds. The membranes exhibited excellent catalytic activity in cascade reactions in one pot (the yield of the product was as high as 99.9 %) and can be reutilized up to 15 times without any significant loss in activity. Stable pure MOF membranes, as shown in this work, would be of interest for several other applications beyond catalysis.

Synthesis and uranium adsorption studies of UiO-66 (Ce) based metal organic frameworks from aqueous solutions

Ce based Metal Organic Framework (MOF) UiO-66 (Ce) and a MOF-composite CeO2@UiO-66 (Ce) were prepared by conventional heating and hydrothermal method respectively. Both the MOFs were characterized using X-ray Diffraction (XRD) technique, Fourier Transform Infra Red (FT-IR) spectroscopy, Field Emission-Secondary Electron Microscopy (FE–SEM), Small Angle X-ray Scattering (SAXS), Thermogravimetric Analysis (TGA), Differential Thermal Analysis (DTA) and Transmission Electron Microscopy (TEM). N2 adsorption-desorption isotherms of UiO-66 (Ce) showed large specific surface area of ∼981 m2/g and a reasonably large pore volume compared to the composite sample. Their uranium adsorption capacity in aqueous solutions was investigated in the pH range 2–6. Uranium adsorption experiments indicated reasonably higher uranium adsorption capacity of 239 mg/g for CeO2@UiO-66 (Ce) compared to UiO-66 (Ce) (190 mg/g). Kinetic studies revealed rapid uranium adsorption in pure MOF compared to the composite material which was attributed to the blocking of pores by CeO2 nanoparticles in the composite material. These frameworks showed good thermal stability as revealed by the thermogravimetric studies. The synthesized MOFs exhibit moderate recyclability using dilute acid and can be utilized in successive cycles. The selectivity studies showed that these MOFs are highly selective to U (VI) compared to Fe (III), Co (II), Ni (II) and Sr (II). This study could pave a way for more advanced material synthesis involving MOFs which could prove very beneficial for the wastewater remediation thus creating a safer environment to live in.

Scalable Formation of Diamine-Appended Metal–Organic Framework Hollow Fiber Sorbents for Postcombustion CO2 Capture

We describe a straightforward and scalable fabrication of diamine-appended metal–organic framework (MOF)/polymer composite hollow fiber sorbent modules for CO2 capture from dilute streams, such as flue gas from natural gas combined cycle (NGCC) power plants. A specific Mg-MOF, Mg2(dobpdc) (dobpdc4– = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate), incorporated into poly(ether sulfone) (PES) is directly spun through a conventional “dry-jet, wet-quench” method. After phase separation, a cyclic diamine 2-(aminomethyl)piperidine (2-ampd) is infused into the MOF within the polymer matrix during postspinning solvent exchange. The MOF hollow fibers from direct spinning contain as high as 70% MOF in the total fibers with 98% of the pure MOF uptake. The resulting fibers exhibit a step isotherm and a “shock-wave-shock” breakthrough profile consistent with pure 2-ampd-Mg2(dobpdc). This work demonstrates a practical method for fabricating 2-ampd-Mg2(dobpdc) fiber sorbents that display the MOF’s high CO2 adsorption capacity while lowering the pressure drop during operation.

Metal-organic framework-based hydrogel with structurally dynamic properties as a stimuli-responsive localized drug delivery system for cancer therapy

Metal-organic framework (MOF) is an exciting class of porous biomaterials that have been considered as a carrier to store and deliver therapeutic drugs. However, similar to other nanomaterials, the application of MOF in clinical settings is still limited because of premature diffusion of their payloads and tissue off-targeting behavior. To overcome these challenges, we designed an MOF-based hydrogel with structurally dynamic properties, i.e., self-healing and shear-thinning, as an injectable localized drug delivery platform. The drug-encapsulating MOF hydrogel is formed through a dynamic coordination bond cross-linkage between a doxorubicin-loaded MOF (MOF@DOX) particle and a homemade bisphosphonate-modified hyaluronic acid (HA-BP) polymeric binder. The HA-BP·MOF@DOX hydrogel demonstrates pH- and ATP-responsive drug release characteristic and efficiently kills cancer cells in vitro. The animal experiments reveal that the HA-BP·MOF@DOX hydrogel has enhanced capability in terms of tumor growth suppression as compared to the MOF@DOX group, which can be attributed to drug localization in hydrogel superstructure and sustained release at the tumor site. The presented injectable dynamic MOF-based hydrogel is a promising in vivo localized drug delivery system for cancer treatment. Herein, we report the self-healing and shear-thinning of MOF-based drug carrier cross-linked by coordinate bonds for the first time and provide new insights and a facile chemical strategy for designing and fabricating MOF-based biomaterials by using bisphosphonate-zinc interaction. Statement of significanceBisphosphonate-zinc interaction is a facile chemical strategy to cross-link metal-organic framework (MOF)-based hydrogel. The presented MOF-based hydrogel demonstrates structurally dynamic properties, including smooth injectability, self-healing, and shear-thinning. The developed MOF-based hydrogel possesses pH- and ATP-responsive drug release characteristic and kills cancer cells in vitro efficiently. The dynamic MOF-based hydrogel shows enhanced in vivo anticancer activity as compared to pure MOF particles. Self-healing and shear-thinning of metal-ligand cross-linked MOF-based drug delivery system are reported for the first time, thus providing new insights for the design and fabrication of MOF-based biomaterials.

Rational Design of Metal–Organic Framework‐Based Materials for Photocatalytic CO2 Reduction

Photocatalytic carbon dioxide (CO2) reduction can utilize solar light to convert CO2 to high value‐added products, which thus are recognized as an intriguing strategy to solve excessive CO2 emissions. Metal–organic framework (MOF)‐based photocatalysts have shown high potential in the field of CO2 reduction due to their high porosity and tunable structure. In this review, the recent progress achieved in the rational design of MOF‐based photocatalysts, including the pure MOF materials, MOF‐based composites, and the derivatives of MOFs, for the reduction of CO2, are summarized and the developed modification strategies to enhance the photocatalytic performance of MOF‐based photocatalysts are highlighted. The current pending issues and the outlook for the future development are also discussed.

Pyrrolic N wrapping strategy to maximize the number of single-atomic Fe-Nx sites for oxygen reduction reaction

Iron-nitrogen-carbon (Fe–N–C) catalysts with a representative single-atomic structure are promising platinum group metal-free catalysts for the oxygen reduction reaction (ORR) as they exhibit comparable activity to commercial catalysts. To enhance the ORR activity of Fe–N–C catalysts, the number of single Fe atoms coordinated N (Fe-Nx) should be maximized. In this study, a strategy is devised to increase the number of Fe-Nx sites using electrostatic interactions between electronegative pyrrolic-N and electropositive Fe ions. Pyrrolic N-rich carbon (pNC) is dispersed on the surface of the metal-organic framework (MOF) to form composite supports ([email protected]). Owing to the well-dispersed pNC and electrostatic interactions, the number of Fe-Nx sites on the [email protected] hollow carbon framework (Fe/[email protected]) increases dramatically compared to that on the pristine MOF (Fe/HCF). The original shape of the Fe-absorbed MOF is maintained by the conversion of pNC into carbon layer within the framework by pyrolysis at 1000 °C even though pure Fe-absorbed MOF collapses. An anion exchange membrane fuel cell (AEMFC) with Fe/[email protected] is fabricated, and it shows a high current density of 437 mA cm−2 at 0.6 V and a power density of 343 mW cm−2. This performance suggests that the synthesized catalysts are excellent potential cathodic catalysts for AEMFCs.