Microporous Metal-organic Framework Research Articles

Mechanistic Insights into C–H Borylation of Arenes with Organoiridium Catalysts Embedded in a Microporous Metal–Organic Framework

Organometallic iridium catalysts can be used in conjunction with bispinacolatodiboron (B2Pin2) to effect the borylation of a variety of substrates such as arenes, alkanes, heteroarenes, and oxygena...

A Microporous Metal–Organic Framework Catalyst for Solvent-free Strecker Reaction and CO2 Fixation at Ambient Conditions

The self-assembly of zinc(II) acetate tetrahydrate, a flexible tetrapyridyl ligand, tetrakis(3-pyridyloxymethylene)methane (3-tpom), a bent dicarboxylic acid, and 4,4'-(dimethylsilanediyl)bis- benzoic acid (H2L) under solvothermal conditions has resulted in the formation of a microporous zinc(II)-organic framework, {[Zn2(3-tpom)(L)2]·2H2O}n (1). The framework exhibits very good thermal stability as evident from the thermogravimetric analysis, which is further supported by variable temperature powder X-ray diffraction analysis. The microporous nature of the framework has been established by the gas adsorption analysis. The framework exhibits exceptionally selective carbon dioxide adsorption in contrast with other gases having comparatively larger kinetic diameters (3.64 Å for N2 and 3.8 Å for CH4) under ambient conditions (298 K and 1 bar pressure). Further, the framework decorated with catalytically active unsaturated metal sites acts as a good catalyst toward the cycloaddition reaction of CO2 with epoxides and the three-component Strecker reaction at ambient conditions and without the requirement of any solvent. The heterogeneous nature along with good catalytic activity at ambient and solvent-free conditions entitles 1 as an excellent catalyst for these organic transformations.

Confined crystallization of microporous metal-organic framework within mesoporous silica with enhanced hydrostability: Ultrafast removal of organic dyes from aqueous solutions by MIL-68(Al)@SBA-15 composite

In this study, MIL-68(Al), a metal-organic framework, and SBA-15 (Santa Barbara Amorphous-15), a well-known silica material, were chosen for fabrication of composite material 1 by reflux method. The composite 1 named MIL-68(Al)@SBA-15 was characterized fully. TEM images and BET results confirmed the crystallization of MIL-68(Al) inside SBA-15 channels. Interestingly the BET surface area increased from 797 m2 g−1 for SBA-15 to 947 m2 g−1 for composite 1. Herein for the first time, we synthesized and used composite 1 for the adsorption of dye pollutants from water. The adsorption ability of composite 1 was investigated towards different dye solutions and was compared with the ability of bare MIL-68(Al) and SBA-15. The results revealed that the composite 1 adsorbed 100 % of MB solution in 0.5 min with a maximum adsorption capacity of 68.93 mg g−1. Furthermore, the composite 1 was used for adsorption of binary, ternary, and quaternary mixed dye solutions and showed high adsorption efficiency for removal of all the mixed dye solutions in short time. The kinetics of the adsorption process follows the pseudo-second-order model, and the Langmuir isotherm model provides the best fitting for the adsorption of MB onto composite 1. Also, for investigation of the effect of synthesis route on the prepared composite material, the composite 2 named MIL-68(Al)/SBA-15 was synthesized by solid-state grinding and its adsorption ability toward dye solutions was compared with composite 1.

Charge percolation in metal-organic framework (HKUST-1)‒graphene nanocomposites

Modulating the conductivity of microporous metal-organic frameworks (MOFs) through formulation of composites with graphene (G), as the conductive element, is demonstrated, without being limited to a particular MOF composition or topology. The synthesis allows for varying G content within the composite systematically, resulting in highly electrically conductive composites beyond 30 wt% G. The charge percolation model can effectively be utilized to describe the macroscopic electrical conductivity of the synthesized composites. Starting from a non-conductive MOF (HKUST-1, σ = 2*10−8 S m−1), enhanced conductivity can be accessed through increasing the G wt%, reaching more than nine orders of magnitude increase in conductivity up to 23.3 S m−1 for the composite containing 59.4 wt% G. A charge percolation threshold of 30 wt% G was observed, where sufficient G-G contacts were established within the composite. The ab initio DFT calculations on Cu-paddlewheel@G model indicated several non-covalent interactions, including OH⋯π and π‒π interactions, governing the deposition of the MOF on top of G (range of ‒101.3 kJ/mol to −113.8 kJ/mol). This approach is potentially transferable to the vast majority of MOFs, as surface functionalization of the conductive filler is not a prerequisite for the attainment of bottom-up assembly of the MOF@G.

Immobilization of Oxygen Atoms in the Pores of Microporous Metal–Organic Frameworks for C2H2 Separation and Purification

The development of porous metal–organic framework (MOF) solids displaying efficient separation and purification of acetylene is of cardinal significance but challenging in the chemical industry. Am...

Fabrication of Microporous Metal–Organic Frameworks in Uninterrupted Mesoporous Tunnels: Hierarchical Structure for Efficient Trypsin Immobilization and Stabilization

AbstractHierarchically porous metal–organic frameworks (HP‐MOFs) are promising in various applications. Most reported HP‐MOFs are prepared based on the generation of mesopores in microporous frameworks, and the formed mesopores are connected by microporous channels, limiting the accessibility of mesopores for bulky molecules. A hierarchical structure is formed by constructing microporous MOFs in uninterrupted mesoporous tunnels. Using the confined space in as‐prepared mesoporous silica, highly dispersed metal precursors for MOFs are coated on the internal surface of mesoporous tunnels. Ligand vapor‐induced crystallization is employed to enable quantitative formation of MOFs in situ, in which sublimated ligands diffuse into mesoporous tunnels and react with metal precursors. The obtained hierarchically porous composites exhibit record‐high adsorption capacity for the bulky molecule trypsin. The thermal and storage stability of trypsin is improved upon immobilization on the composites.

Fabrication of Microporous Metal-Organic Frameworks in Uninterrupted Mesoporous Tunnels: Hierarchical Structure for Efficient Trypsin Immobilization and Stabilization.

Hierarchically porous metal-organic frameworks (HP-MOFs) are promising in various applications. Most reported HP-MOFs are prepared based on the generation of mesopores in microporous frameworks, and the formed mesopores are connected by microporous channels, limiting the accessibility of mesopores for bulky molecules. A hierarchical structure is formed by constructing microporous MOFs in uninterrupted mesoporous tunnels. Using the confined space in as-prepared mesoporous silica, highly dispersed metal precursors for MOFs are coated on the internal surface of mesoporous tunnels. Ligand vapor-induced crystallization is employed to enable quantitative formation of MOFs in situ, in which sublimated ligands diffuse into mesoporous tunnels and react with metal precursors. The obtained hierarchically porous composites exhibit record-high adsorption capacity for the bulky molecule trypsin. The thermal and storage stability of trypsin is improved upon immobilization on the composites.

Phase Transitions in Metal-Organic Frameworks Directly Monitored through In Situ Variable Temperature Liquid-Cell Transmission Electron Microscopy and In Situ X-ray Diffraction.

Zr6-based metal-organic frameworks (MOFs) with tetratopic organic linkers have been extensively investigated owing to their versatile structural tunability. While diverse topologies and polymorphism in the resulting MOFs are often encountered with tetratopic linkers and Zr6 nodes, reports on phase transitions within these systems are rare. Thus, we have a limited understanding of polymorph transformations, hindering the rational development of pure phase materials. In this study, a phase transition from a microporous MOF, scu-NU-906, to a mesoporous MOF, csq-NU-1008, was discovered and monitored through in situ variable temperature liquid-cell transmission electron microscopy (VT-LCTEM), high-resolution transmission electron microscopy (HRTEM), and in situ variable temperature powder X-ray diffraction (VT-PXRD). It was found that the microporous- to-mesoporous transformation in the presence of formic acid occurs via a concomitant dissolution-reprecipitation process.

A microporous metal-organic framework with basic sites for efficient C2H2/CO2 separation

Acetylene is an important chemical feedstock that is very challenging to separate/purify from the common impurity CO2 generated during the manufacture processes. Adsorptive separation by porous material is environmentally friendly and energy efficient, and therefore is regarded as an attractive approach. The microporous MOF Cu2(ade)2(PA)2 (ade ​= ​adenine, PA ​= ​propionic acid) with accessible basic sites was evaluated for C2H2/CO2 separation. The C2H2 adsorption capacity and C2H2/CO2 selectivity are comparable to those of the benchmark materials making this material promising candidate for the important C2H2/CO2 separation.

Microporous metal-organic framework with specific functional sites for efficient removal of ethane from ethane/ethylene mixtures

The separation of low concentration ethane (C2H6) from ethylene (C2H4) is of great importance in petrochemical processes; however, it is widely considered to be a challenging task. Nonetheless, utilizing suitable C2H6 selective adsorbents, adsorptive separation technology approaches can be employed to obtain high purity ethylene with high energy efficiency. Herein, we report a series of MOF materials, namely M-PNMI (M = Mn, Zn, Cd), which were synthesized using N,N′-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxdiimide. Cooperative single component adsorption analysis, as well as Ideal Adsorbed Solution Theory (IAST) calculation, and Grand Canonical Monte Carlo (GCMC) simulation revealed that these MOF materials exhibit distinctly higher adsorption capacity and preferential binding affinity for C2H6 over C2H4. These observations are due to the presence of favorable pore environments in the MOFs, which result in strong C2H6 adsorption potential. The specific C2H6 binding sites were clearly determined by density functional theory (DFT) calculations. Thus, the described M-PNMI materials can efficiently remove C2H6 from C2H6/C2H4 (1/9 and 1/15, v/v) mixtures to directly produce high purity C2H4 (>99.99%) under ambient conditions.

A zinc mixed-ligand microporous metal-organic framework as solid-phase microextraction coating for priority polycyclic aromatic hydrocarbons from water samples

For the first time, a novel triple catenated Zn2+-pillared metal-organic framework (PUM 210) is proposed as solid-phase microextraction coating for the extraction of 16 priority pollutant polycyclic aromatic hydrocarbons (PAHs) from water samples and their subsequent quantitation via gas chromatography-mass spectrometry. Extraction was optimized by using a central composite face centered design followed by the multicriteria method of the desirability functions. The best conditions for the extraction of the sixteen analytes were found in correspondence to an extraction temperature of 30 °C and an extraction time of 30 min.Method validation allowed to obtain quantitation limits in the 1–7 ng/L range, a repeatability within 16% relative standard deviation (RSD), an intermediate precision within 22% RSD at limits of quantitation, and recovery rates in the 85 (±5) – 117 (±21)% range. As for selectivity, PAHs extraction proved to be feasible also in the presence of high concentration levels of potentially competing compounds like benzene, toluene, ethylbenzene and xylenes with steric hindrance playing a key role in analyte inclusion. Enrichment factors in the 300 (±5) – 14-950 (±150) range were obtained, being the heaviest compounds better extracted with respect to commercial coatings. Finally, the method was applied for the quantitation of PAHs in sixty-nine underground water samples during a monitoring campaign carried out in 2018.

Microporous Metal-Organic Framework with a Completely Reversed Adsorption Relationship for C2 Hydrocarbons at Room Temperature.

As a new type of porous material, metal-organic frameworks (MOFs) have been widely studied in gas adsorption and separation, especially in C2 hydrocarbons. Considering the stronger interaction between the unsaturated molecules and the metal sites, and the smaller molecular size of unsaturated molecules, the usual relationship of affinities and adsorption capacities among C2 hydrocarbons in most common MOFs is C2H2 > C2H4 > C2H6. Herein, a unique microporous metal-organic framework, NUM-7a (activated NUM-7), with a completely reversed adsorption relationship for C2 hydrocarbons (C2H6 > C2H4 > C2H2) has been successfully synthesized, which breaks the traditional concept of the adsorption relationship of MOFs for C2 hydrocarbons. Based on this unique adsorption relationship, a green and simple one-step separation purification for a large amount of C2H4 can be expected to be achieved through the selective adsorption of C2H6. In addition, NUM-7a also shows good selectivities in C2H2/CO2 and CO2/CH4.

Microporous MOF with open metal sites for CO2 fixation and protective effect on osteoarthritis by regulating the activation of PI3K/AKT pathway

A novel microporous metal-organic framework (MOF) based on Zn(II) ion as node with the chemical formula of {[Zn(H2O)(HL)]·(DMF)2(H2O)2}n (1, H3L ​= ​2-(4-carboxyphenyl)-1H-benzo[d]imidazole-5-carboxylic acid, DMF ​= ​N,N-dimethylformamide), which has rich water-coordinated metal centers and high density of free N-donor groups has been successfully prepared via H3L ligand and Zn(NO3)2·6H2O reaction within H2O, EtOH along with DMF mixed solvent. The presence of open metal sites along with the basic N-donor sites in the resulting activated 1a induces a moderate high sorption capacity of CO2. In addition, because of basic N-donor groups along with Lewis acidic Zn2+ ions, 1a has become an efficient heterogeneous catalyst, which can chemically fix CO2 in the carbonate of cyclic annular at mild room temperature. Furthermore, the influence of compound on the activation of PI3K/AKT signaling pathway was studied by Western blot. The ELISA was carried out the evaluate the IL-18 and IL-6 content in synovial cells after compound treatment.

A microporous metal-organic framework with naphthalene diimide groups for high methane storage.

We reported a microporous MOF FJU-101 with open naphthalene diimide functional groups for room temperature (RT) high methane storage. At RT and 65 bar, the total volumetric CH4 storage capacity of 212 cm3 (STP) cm-3 of FJU-101a is significantly higher than those of the isoreticular MFM-130a and UTSA-40a. The enhanced methane uptake in FJU-101a is attributed to the polar carbonyl sites, which can generate strong electrostatic interactions with CH4 molecules.

Hexane isomers separation on an isoreticular series of microporous Zr carboxylate metal organic frameworks

The microporous MOF MIL-140B can separate hexane isomers according to the degree of branching, linear >mono-branched >di-branched, with a remarkably high selectivity up to 10 at 343 K. GCMC simulations confirm the origins of the molecular separation.

Hierarchically macro-meso-microporous metal-organic framework for photocatalytic oxidation.

The macro-meso-microporous and defective metal-organic framework constructed by transition metal Zn and 2,2'-bipyridine-5,5'-carboxylate was synthesized in CO2-expanded solvent. It shows high photocatalytic activity and selectivity for the oxidation of amines to imines under mild conditions, i.e., air as an oxidant, room temperature, and involving no photosensitizer or cocatalyst.

Enzyme immobilization in highly ordered macro–microporous metal–organic frameworks for rapid biodegradation of hazardous dyes

HRP immobilized in highly ordered macro–microporous metal–organic frameworks for biodegradation of hazardous dyes selectively and rapidly.

Self-supported rhodium catalysts based on a microporous metal–organic framework for polymerization of phenylacetylene and its derivatives

Highly efficient, cis-selective, stable, recyclable and reusable heterogeneous single-site MOF-supported rhodium catalysts polymerize PA and its derivatives, producing cis-transoidal PPAs and their functional derivatives having a helical configuration or AIE properties.

Separation of ethane and ethylene by a robust ethane-selective calcium-based metal–organic framework

Adsorption and separation of ethane and ethylene has been studied on a robust Ca-based microporous metal–organic framework which shows ethane-selective adsorption over ethylene.

Construction of a functionalized hierarchical pore metal-organic framework via a palladium-reduction induced strategy.

Hierarchical porosity and functionalization are recognized as two crucial parameters in mediating the catalytic performance of heterogeneous catalysts, however, they are rarely achieved simultaneously in the development of metal-organic frameworks (MOFs). In this work, a simple and efficient method has been developed to synchronously construct hierarchical porosity and functionalization within a sulfonic acid group functionalized microporous MOF via a palladium-reduction induced strategy, for the first time. The generation mechanism of the mesopore has been explained using two-dimensional 1H DQ-SQ MAS NMR. The content of the mesopore and the active sites within mesoPd@NUS-6 could be finely tuned by simply controlling Pd loading. Particularly, the combination of hierarchical porosity and functionalization, as well as the ultra-stable structure endow the composites with great potential in bulk, for adsorption and heterogeneous catalysis.