Mesoporous Metal-organic Framework Research Articles

Application of Mesoporous COK-15 Metal-Organic Framework as Medication Carrier for Acetaminophen and Clindamycin

In recent years, metal-organic frameworks (MOFs) have attracted considerable interest in a variety of fields, including catalysis, energy storage and conversion, gas storage and separation, sensing, and controlled drug delivery. COK-15 is a mesoporous MOF with substantially wide permanent pores, which make it a right candidate for drug delivery. In this work, the behavior of COK-15 as a medication carrier for entrapment of selected medications (acetaminophen and clindamycin) and then controlled releasing of the medications in a PBS (Phosphate Buffered Saline) solution is studied. COK-15 has been synthesized and characterized by X-ray powder diffraction, scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET), Fourier-Transform Infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). The medication releasing has been studied by UV-Vis technique at different time intervals. The release kinetics has been investigated by employing different kinetic models.

A window-space-directed assembly strategy for the construction of supertetrahedron-based zeolitic mesoporous metal-organic frameworks with ultramicroporous apertures for selective gas adsorption.

Despite their scarcity due to synthetic challenges, supertetrahedron-based metal–organic frameworks (MOFs) possess intriguing architectures, diverse functionalities, and superb properties that make them in-demand materials. Employing a new window-space-directed assembly strategy, a family of mesoporous zeolitic MOFs have been constructed herein from corner-shared supertetrahedra based on homometallic or heterometallic trimers [M3(OH/O)(COO)6] (M3 = Co3, Ni3 or Co2Ti). These MOFs consisted of close-packed truncated octahedral cages possessing a sodalite topology and large β-cavity mesoporous cages (∼22 Å diameter) connected by ultramicroporous apertures (∼5.6 Å diameter). Notably, the supertetrahedron-based sodalite topology MOF combined with the Co2Ti trimer exhibited high thermal and chemical stability as well as the ability to efficiently separate acetylene (C2H2) from carbon dioxide (CO2).

The role of temperature and adsorbate on negative gas adsorption transitions of the mesoporous metal-organic framework DUT-49.

Unusual adsorption phenomena, such as breathing and negative gas adsorption (NGA), are rare and challenge our thermodynamic understanding of adsorption in deformable porous solids. In particular, NGA appears to break the rules of thermodynamics in these materials by exhibiting a spontaneous release of gas accompanying an increase in pressure. This anomaly relies on long-lived metastable states. A fundamental understanding of this process is desperately required for the discovery of new materials with this exotic property. Interestingly, NGA was initially observed upon adsorption of methane at relatively low temperature, close to the respective standard boiling point of the adsorptive, and no NGA was observed at elevated temperatures. In this contribution, we present an extensive investigation of adsorption of an array of gases at various temperatures on DUT-49, a material which features an NGA transition. Experiments, featuring a wide range of gases and vapors at temperatures ranging from 21-308 K, were used to identify for each guest a critical temperature range in which NGA can be detected. The experimental results were complemented by molecular simulations that help to rationalize the absence of NGA at elevated temperatures, and the non-monotonic behavior present upon temperature decrease. Furthermore, this in-depth analysis highlights the crucial thermodynamic and kinetic conditions for NGA, which are unique to each guest and potentially other solids with similar effects. We expect this exploration to provide detailed guidelines for experimentally discovering NGA and related "rule breaking" phenomena in novel and already known materials, and provide the conditions required for the application of this effect, for example as pressure amplifying materials.

Core-shell gold nanorod@mesoporous-MOF heterostructures for combinational phototherapy.

Despite the increasing usage of porphyrinic metal-organic frameworks (MOFs) for combination therapy, the controlled encapsulation of inorganic nanoparticle-based therapeutics into such MOFs with specific structures has remained a major obstacle for improved tumor therapy. Here, we report the synthesis of a mesoporous MOF shell on the surface of gold nanorods (AuNRs), wherein a single AuNR is captured individually in single-crystalline MOFs with a controlled crystallographic orientation, for combinational phototherapy against solid tumors. The core-shell heterostructures have the benefits of a mesoporous structure and photoinduced singlet oxygen generation behavior characterized by the porphyrinic MOF shell, together with the plasmonic photothermal conversion characteristic of AuNRs. We demonstrated that the AuNR@MOF nanoplatform enables an efficient tumor treatment strategy by combining photodynamic therapy and photothermal therapy. We should emphasize that such systems could have applications beyond the field of cancer therapy, like plasmonic harvesting of light energy to induce and accelerate catalytic reactions within MOFs and multifunctional nanocarriers for agricultural formulations.

Constructing Mesoporous Adsorption Channels and MOF-Polymer Interfaces in Electrospun Composite Fibers for Effective Removal of Emerging Organic Contaminants.

Recently, metal-organic framework (MOF)-based electrospun fibers have attracted considerable attention as adsorbents for organic contaminant removal from water. To prepare these fibers, two common strategies including blending electrospinning and surface coating are employed. However, fibers obtained from the two strategies still have some disadvantages, such as adsorption site blockage and unstable loading. Here, we constructed interconnected mesopores in the electrospun zeolitic imidazolate framework-8 (ZIF-8)/polyacrylonitrile (PAN) fibers with the assistance of poly(vinylpyrrolidone) to expose more adsorption sites of ZIF-8 and make ZIF-8 more stable. Moreover, the mesopores could also enhance the diffusion of contaminant molecules and create MOF-polymer interfaces in the fiber, which improve the adsorption rate and adsorption capacity, respectively. The obtained fibers were used to adsorb antibiotic tetracycline from water. Benefiting from the mesoporous adsorption channels and the MOF-polymer interface, porous ZIF-8/PAN fibers showed faster adsorption kinetics than ZIF-8/PAN blending fibers and larger adsorption capacity than ZIF-8-coated PAN fibers and ZIF-8/PAN blending fibers. The maximum adsorption capacity of porous ZIF-8/PAN fibers was 885.24 mg/g, which is close to that of pure ZIF-8. After 10 adsorption-desorption cycles, the removal efficiency was still above 97%. In addition, porous ZIF-8/PAN fibers could act as the membrane adsorbents to dynamically separate tetracycline with a treated capacity of 9.93 × 103 bed volumes. These results demonstrate that our prepared porous ZIF-8/PAN fibers have great potential in antibiotic drug removal.

Iron-Mineralization-Induced Mesoporous Metal-Organic Frameworks Enable High-Efficiency Synergistic Catalysis of Natural/Nanomimic Enzymes.

Metal-organic frameworks (MOFs) have become a promising accommodation for enzyme immobilization and protection. However, the integration of multienzymes into MOFs may result in compromise of individual enzymatic activity. In this work, we report an iron mineralization strategy to facilely construct a mesoporous MOF, possessing excellent peroxidase-mimic bioactivity. Furthermore, the feasibility of in situ encapsulating natural enzymes within the developed mesoporous MOF nanozymes endows these natural/nanomimic enzyme hybrids with remarkably enhanced synergistic catalysis ability. Such activity enhancement is mainly due to (1) the fast flux rate of substances through the interconnected mesoporous channels and (2) the simultaneously increased loading amount of enzymes and iron within the MOFs caused by the iron mineralization process.

Desensitization of high explosives by encapsulation in metal-organic frameworks

High explosives (HEs) that contain a large amount of potential energy are used in various fields, including the military, mining, and construction industries. The detonation of these high-energy materials should be initiated by a desired and expected external energy; however, unintentional initiation occurs owing to internal voids inside the high explosives, referred to as hotspots. To address this issue, in this study, one of the representative HEs, 1,3,5-trinitro-1,3,5-triazinane (RDX), was confined in nanoporous metal-organic frameworks (MOFs) with high surface areas and high pore volumes to decrease the hotspots and provide a rigid shield. The RDX-encapsulated mesoporous MOF (pore volume of 1.4 cm3/g) showed lower impact sensitivity (23%) and friction sensitivity (125%) compared to those of the non-encapsulated RDX, owing to the decrease in hotspots due to the nano-sizing of the HE and protection from external impact provided by the rigid MOF structure.

Purified mesoporous nickel metal organic framework as electrocatalyst for hydrogen evolution reaction (HER) in basic medium

Metal organic framework or MOFs are found to be a good catalyst for hydrogen evolution in view of its excellent structural features like porous nature and well-defined morphology. This report describes the synthesis of Nickel-MOF prepared by solvothermal approach and further purified by a chemical process. Both impure and purified Nickel-MOFs are fabricated as electrodes for evaluating HER reaction. The performance towards electrocatalytic activity is affected due to the impurities present in the porous structure. In view of investigating the effect of activation/purification process towards morphology and in-turn HER activity, activation and purification is carried out to enhance the performance of MOFs. The electrochemical characterization proves high electrocatalytic activity for purified Ni-MOF with high rate kinetics towards HER than impure Ni-MOF. The Tafel slope of purified Nickel MOF is estimated to be 73.7 mV/dec with a low charge transfer resistance of 1.84 Ω, whereas the unpurified Ni-MOF shows 87.47 mV/dec and 3.85 Ω. Results show that pure Ni-MOF has abundant catalytic active edge sites and obeys Volmer-Heyrvosky mechanism with makes desorption of hydrogen as rate determining step.

Nanoscale Hierarchically Micro- and Mesoporous Metal-Organic Frameworks for High-Resolution and High-Efficiency Capillary Electrochromatographic Separation.

Metal-organic frameworks (MOFs) have been widely applied in a variety of fields. However, most of the developed MOFs are micrometer scale in crystal size and contain only micropores, which will limit the mass transport and diffusion of various analytes into their internal interaction sites, severely restricting the potential of MOFs in separation science. Herein, nanoscale hierarchically porous MOFs (NHP-MOFs) were first explored as a novel MOF-based stationary phase with excellent mass transfer performance and abundant accessible interaction sites for high-performance chromatographic separation. As a proof-of-concept demonstration, the nanoscale hierarchically micro- and mesoporous UiO-66 (NHP-UiO-66) was firmly immobilized on the capillary inner surface and utilized as the porous stationary phase for high-resolution and high-efficiency electrochromatographic separation. A wide range of low-, medium-, and high-molecular-weight analytes, including substituted benzenes, chlorobenzenes, polycyclic aromatic hydrocarbons, nucleosides, polypeptides, and proteins were all separated well on a NHP-UiO-66-coated column with excellent resolution and repeatability, exhibiting significantly improved column efficiency and separation ability compared to those of a microporous UiO-66-modified column. The maximum column efficiencies for all the six kinds of analytes reached up to 1.2 × 105 plates/m, and the relative standard deviations of the migration times of substituted benzenes for intraday, interday, and column-to-column were all lower than 5.8%. These results reveal that NHP-MOFs can effectively combine the advantages of the high specific surface area of microporous MOFs and the excellent mass transfer performance and abundant accessible interaction sites of NHP materials, possessing great prospect for high-performance chromatographic separation.

Regioselective Functionalization of the Mesoporous Metal-Organic Framework, NU-1000, with Photo-Active Tris-(2,2'-bipyridine)ruthenium(II).

Solvent-assisted ligand incorporation is an excellent method for the post-synthetic functionalization of Zr-based metal–organic frameworks (MOFs), as carboxylate-derivative functionalities readily coordinate to the Zr6 nodes by displacing node-based aqua and terminal hydroxo ligands. In this study, a photocatalytically active ruthenium complex RuII(bpy)2(dcbpy), that is, bis-(2,2′-bipyridine)-(4,4′-dicarboxy-2,2′-bipyridine)ruthenium, was installed in the mono-protonated (carboxylic acid) form within NU-1000 via SALI. Crystallographic information regarding the siting of the ruthenium complex within the MOF pores is obtained by difference envelope density analysis. The ruthenium-functionalized MOF, termed Ru-NU-1000, shows excellent heterogeneous photocatalytic activity for an oxidative amine coupling reaction.

A Mesoporous Zirconium-Isophthalate Multifunctional Platform

<h2>Summary</h2> Mesoporous materials suffer from poor crystallinity and hydrolytic stability, lack of chemical diversity, insufficient pore accessibility, complex synthesis, and toxicity issues. Here the association of Zr-oxo clusters and isophthalate via a homometallic-multicluster-dot strategy results in a robust mesoporous metal-organic framework, denoted as MIP-206 (MIP stands for materials of the Institute of Porous Materials of Paris), that overcomes the aforementioned limitations. MIP-206, with a combination of Zr₆ and Zr₁₂ oxo-cluster inorganic building units into a single structure, exhibits meso-channels of ca. 2.6 nm and displays excellent chemical stability. Owing to the abundant variety of functionalized isophthalic acid linkers, the chemical environment of MIP-206 can be tuned without hampering pore accessibility. MIP-206 loaded with palladium nanoparticles acts as an efficient and durable catalyst for the dehydrogenation of formic acid, outperforming benchmark mesoporous materials. This paves the way toward the utilization of MIP-206 as a mesoporous platform for a wide range of potential applications.

MIL-100(Fe)-derived carbon sponge as high-performance material for oil/water separation

High hydrophobic and oleophilic hybrid porous sponges were prepared by coating low cost commercial melamine-formaldehyde sponges with a metal-organic framework (MOF) derived porous carbon. A mesoporous metal-organic framework MIL-100(Fe), obtained under mild conditions, was used as precursor material to obtain highly porous carbon, which was incorporated by a simple method onto the three-dimensional skeleton of the commercial sponge. Due to the porous structure and high hydrophobic (water contact angle of 145 ± 6°) and oleophilic (oil contact angle of 0°) properties of the developed hybrid sponges, they were successfully applied for oil-water separation. The carbon coated sponge exhibited excellent selectivity, good absorption capacity of different oils and the advantage of being easily regenerable. Moreover, the hybrid sponge was used in conjunction with a vacuum system for continuous separation of oil pollutants from the water surface showing excellent oil-absorption abilities even in the case of real saltwater samples.

CO2 adsorption at low pressure over polymers-loaded mesoporous metal organic framework PCN-777: effect of basic site and porosity on adsorption

Selective capture of CO2 from offgas is highly important for our sustainability, including mitigating global warming. Here, we investigated the CO2 and N2 adsorption under low pressure by using a mesoporous Zr-based metal organic framework PCN-777 with or without modification with polymers like polyethyleneimine (PEI) and polystyrene (PS). The polymers were applied in this study in order to reduce the pore size of PCN-777 (P777) and to introduce basic sites when PEI was used. PCN-777 s loaded with both the PEI and PS were effective in CO2 adsorption because of reduced pore size; and [email protected] s were highly effective in CO2 capture owing to basic sites on PEI. For example, the best adsorbent (among the studied PCN-777-based adsorbents), PEI(20%)@P777, showed around 2.3 and 5.7 times of adsorption capacity (at 0.15 atm) and selectivity (CO2/N2), respectively, as much as those of the pristine P777. Moreover, this MOF is recyclable and has the recommended heat of adsorption when adsorbed CO2 is not much. Therefore, it might be suggested that mesoporous MOFs, not suitable for CO2 capture under low pressure (because of too big pore), can be modified facilely for effective CO2 adsorption (especially under low pressure of 1 atm or less) by loading polymers with basicity onto the mesoporous MOFs.

The encapsulation of POM clusters into MIL-101(Cr) at molecular level: LaW10O36@MIL-101(Cr), an efficient catalyst for oxidative desulfurization

The anchoring of Weakley-type polyoxometalate (POM) Na 7 [H 2 LaW 10 O 36 ] in mesoporous metal-organic framework (MOF) MIL-101(Cr) to prepare a novel host-guest composite is here reported for the first time. The successful encapsulation of LaW 10 into MIL-101(Cr) has been achieved via facile tandem post-synthetic modification strategy and confirmed by several instrumental techniques. The LaW 10 guests were dispersed homogeneously in MIL-101(Cr) nanocages at molecular level. The as-synthesized composite combines both the merits of the POMs (remarkable efficiency and reversible redox) and MOF (sufficient recyclability and exceptional porosity), thus displaying obvious host-guest synergistic effect. The LaW 10 O 36 @MIL-101(Cr) composite served as heterogeneous single-site catalyst for ODS process and exhibited excellent catalytic performance, with removal efficiency of 99.1, 94.5 and 84.7% for DBT, 4,6-DMDBT and BT, respectively. Thanks to the confinement effect from Cr···O W coordinative interaction, the catalyst provided outstanding recyclability and stability, and can be reused for seven times without leaching, structural alteration and deactivation. Moreover, the structure-activity relationship was investigated in detail, as well as the proposed mechanism. • The Weakley structure POMs were encapsulated into MIL-101(Cr) for the first time. • The LaW 10 O 36 were dispersed uniformly within MIL-101(Cr) at molecular level. • The host-guest synergistic effect enhanced remarkably ODS efficiency and durability. • The confinement effect of MIL-101(Cr) on LaW 10 O 36 results in excellent ODS recyclability.

Preparation and application of peptide molecularly imprinted material based on mesoporous metal-organic framework

In this study, a new molecularly imprinted material, MIP@UiO-66-NH2, was synthesized with glutathione (GSH) as template and mesoporous metal organic framework (UiO-66-NH2) as matrix. The molecularly imprinted polymer was modified on the surface and into the pores of the UiO-66-NH2 by surface molecular imprinting method with thin polymer layer. Based on high specific surface area (1091.93 m2 g−1) and appropriate pore size (35 nm) of the ordered mesoporous UiO-66-NH2, the adsorption capacity for GSH reached 94.43 mg g−1, and the adsorption equilibrium could be achieved within 30 min. The adsorption isotherm data of MIP@UiO-66-NH2 could be described well by Freundlich model and the kinetic data complied well with pseudo-second-order model. In addition, the MIP@UiO-66-NH2 showed low adsorption capacity to GSH structural analogs (QL-cys = 6.51 mg g−1), suggesting great selectivity for GSH recognition. Finally, the MIP@UiO-66-NH2 was successfully applied for selective separation of GSH from BSA, skim milk and egg white tryptic digest.

Supported Palladium Nanocatalysts: Recent Findings in Hydrogenation Reactions

Catalysis has witnessed a dramatic increase on the use of metallic nanoparticles in the last decade, opening endless opportunities in a wide range of research areas. As one of the most investigated catalysts in organic synthesis, palladium finds numerous applications being of significant relevance in industrial hydrogenation reactions. The immobilization of Pd nanoparticles in porous solid supports offers great advantages in heterogeneous catalysis, allowing control of the major factors that influence activity and selectivity. The present review deals with recent developments in the preparation and applications of immobilized Pd nanoparticles on solid supports as catalysts for hydrogenation reactions, aiming to give an insight on the key factors that contribute to enhanced activity and selectivity. The application of mesoporous silicas, carbonaceous materials, zeolites, and metal organic frameworks (MOFs) as supports for palladium nanoparticles is addressed.

Facile Ultrasonic Synthesis of Zirconium Based Porphyrinic MOFs for Enhanced Adsorption Performance Towards Anionic and Mixed Dye Solutions

A porphyrinic mesoporous metal–organic framework (PCN-222(M) (M = Mn, Fe, Cu)) has been synthesized by a simple sonochemical preparation method without high temperature in a short period of time. The ultrasonic method for the preparation of PCN-222(M) was found to be an efficient procedure with a good quantitative yield (PCN-222(M)-U). Harmful cationic and anionic dyes have been removed from wastewater using PCN-222(M). The comparative study of the influences of metalloporphyrin and non-metal porphyrin frameworks (PCN-222) on the adsorption process has been performed. Remarkably high adsorption capacity over PCN-222(M) for the anionic dyes is reported. The porphyrinic metal center of frameworks and pH values affected dye adsorption capacity, indicating the effective role of electrostatic interactions on dye adsorption. Due to the aggregation of MB and MO, a significant increase in the adsorption capacity was observed in a mixture of MB-MO solution at pH 7. High adsorption capacity over PCN-222(M) has been estimated using Langmuir and Freundlich equations. The adsorption kinetics, thermodynamic parameters, stability and reusability of adsorbents have also been reported. The stability of PCN-222(M) in water over three months was investigated (PCN-222(M)-3).

Mesoporous Metal-Organic Framework MIL-101 at High Pressure.

The chromium terephthalate MIL-101 is a mesoporous metal-organic framework (MOF) with unprecedented adsorption capacities due to the presence of giant pores. The application of an external pressure can effectively modify the open structure of MOFs and its interaction with guest molecules. In this work, we study MIL-101 under pressure by synchrotron X-ray diffraction and infrared (IR) spectroscopy with several pressure transmitting media (PTM). Our experimental results clearly show that when a solid medium as NaCl is employed, an irreversible amorphization of the empty structure occurs at about 0.4 GPa. Using a fluid PTM, as Nujol or high-viscosity silicone oil, results in a slight lattice expansion and a strong modification of the peak frequency and shape of the MOF hydroxyl vibration below 0.1 GPa. Moreover, the framework stability is enhanced under pressure with the amorphization onset shifted to about 7 GPa. This coherent set of results points out the insertion of the fluid inside the MIL-101 pores. Above 7 GPa, concomitantly to the nucleation of the amorphous phase, we observe a peculiar medium-dependent lattice expansion. The behavior of the OH stretching vibrations under pressure is profoundly affected by the presence of the guest fluid, showing that OH bonds are sensitive vibrational probes of the host-guest interactions. The present study demonstrates that even a polydimethylsiloxane silicone oil, although highly viscous, can be effectively inserted into the MIL-101 pores at a pressure below 0.2 GPa. High pressure can thus promote the incorporation of large polymers in mesoporous MOFs.

Mesoporous Silica Encapsulated Metal-Organic Frameworks for Heterogeneous Catalysis

Encapsulation of metal-organic frameworks (MOFs) with a shell of mesoporous silica can boost overall performance of MOFs, offering versatility for synthetic architecture of integrated nanocatalysts with reactor-like features. Recently, Yu et al. report a green approach to make yolk-shell nanoreactors.

Gold-Containing Catalysts Based on Mesoporous Metal–Organic Frameworks of the MIL Type for Regioselective Hydroamination Reaction of Phenylacetylene

Catalyst systems based on gold nanoparticles introduced into the matrices of mesoporous metal–organic frameworks of the MIL type based on trivalent metal ions (Al, Fe) manifest activity in the regioselective hydroamination of phenylacetylene with aniline according to the Markovnikov rule. The activity of the synthesized gold-containing systems significantly depends on the nature of organic and inorganic building units, metal ions, and organic linkers, which form the framework, as well as on the catalyst preparation procedure.