Zeolitic Metal Organic Frameworks Research Articles

Six-Membered Ring Directed Assembly of a Zirconium Zeolitic Metal-Organic Framework for Efficient Separation of Hexane Isomers.

The synthesis of zirconium MOFs with zeolite net is quite challenging due to the high connectivity of Zr6 clusters, which is far from tetrahedral connection, a requisite for zeolite net. In this work, we demonstrate a six-membered ring (6MR) strategy through mimicking of mineral zeolites with mixed ditopic and tritopic carboxylate linkers. With this strategy, the ditopic linker cross-links Zr6 clusters to form 4-connected zeolite-like nets, while the tritopic one is used to direct the formation of 6MR and simultaneously consumes extra coordination sites on the cluster. The feasibility of this strategy is shown by one zeolitic metal-organic framework (NNM-5) and this strategy has also led to the synthesis of the other dia-type zirconium MOF (NNM-6). Interestingly, as the tritopic linker not only directs the formation of 6MR but also partitions 6MR into small segments, NNM-5 with SOD topology shows a structural feature of small aperture and big cage, which has led to efficient separation of hexane isomers. With both exceptionally high n-hexane uptake (65.9 cm3 g-1) and size-exclusion selectivity, an exceptional separation capability is verified by breakthrough experiments. Calculation results demonstrate that the large difference of diffusion energy barrier due to the small aperture accounts for the underlying separation mechanism.

Robust and Multifunctional Wetting Resistance of de novo Engineered Nonfluorinated Metal–Organic Nanocrystals for Environmental Sustainability

Direct synthesis of zeolitic imidazole framework crystals using bulky alkyl ligands is challenging. Herein, a bottom‐up approach to de novo synthesis of a superhydrophobic zeolitic metal–organic framework called mZIF, using mixed ligands, is developed. The mZIF nanocrystals contain a newly designed alkyl chain‐substituted 4‐imidazolate ligand, achieving tailorable hydrophobicity by varying the alkyl tail length. The molecular structure presenting appropriate ligands coupled with the porosity and roughness of the coated surfaces imparts superhydrophobic properties to various coated surfaces such as glass, steel, aluminum, and plastic. The resulting surfaces exhibit a high contact angle of ≥157° and a minimal rolling‐off angle (<5°), enabling efficient oil–water separation in a filtration setup. Furthermore, dip coating the mZIF nanocrystals onto a melamine sponge modifies its water wettability, allowing for facile and efficient removal and recovery of oil from diverse oil–water mixtures with exceptional reusability. Additionally, the mZIF‐modified surfaces showcase notable self‐cleaning and anti‐icing properties. The mZIF‐coated surface shows remarkable storage stability (>1 year), durability against harsh environmental conditions, and notable resistance to mechanical abrasion. This research represents a significant advancement in the facile engineering of multifunctional metal–organic framework‐based systems tailored for diverse practical applications.

A Bismuth-Based Zeolitic Organic Framework with Coordination-Linked Metal Cages for Efficient Electrocatalytic CO2 Reduction to HCOOH.

Zeolitic metal-organic frameworks (ZMOFs) have emerged as one of the most promsing catalysts for energy conversion, but they suffer from either weak bonding between metal-organic cubes (MOCs) that decrease their stability during catalysis processes or low activity due to inadequate active sites. In this work, through ligand-directing strategy, we successfully obtain an unprecedented bismuth-based ZMOF (Bi-ZMOF) featuring a ACO topological crystal structure with strong coordination bonding between the Bi-based cages. As a result, it enables efficient reduction of CO2 to formic acid (HCOOH) with Faradaic efficiency as high as 91 %. A combination of in situ surface-enhanced infrared absorption spectroscopy and density functional theory calculation reveals that the Bi-N coordination contributes to facilitating charge transfer from N to Bi atoms, which stabilize the intermediate to boost the reduction efficiency of CO2 to HCOOH. This finding highlights the importance of the coordination environment of metal active sites on electrocatalytic CO2 reduction. We believe that this work will offer a new clue to rationally design zeolitic MOFs for catalytic reaction.

Two Stable Sodalite-Cage-Based MOFs for Highly Gas Selective Capture and Conversion in Cycloaddition Reaction.

Stable metal-organic frameworks, containing periodically arranged nanosized cages or pores and active Lewis acid-base sites, are considered ideal candidates for efficient heterogeneous catalysis. Herein, based on the light of reticular chemistry design principles, the ingenious assembly of two pyridine N-rich multifunctional triangular linkers, H3TBA [3,5-di (1h-tetrazol-5-yl) benzoic acid] and H2TZI [5-(1H-tetrazol-5-yl)isophthalic acid], with MnII formed PCP-33(Mn) and PCP-34(Mn), respectively. PCP-33(Mn) and PCP-34(Mn) are typical sod topology zeolitic metal-organic frameworks (ZMOFs) with hierarchical tetragonal micropores and metal organic polyhedral sodalite-like cages. The inner walls of these cages are modified by open metal sites MnII and Lewis acid-base sites of halide ions and N pyridine atoms. The characteristics of the cages' structures make two MOFs exhibit high surface area and a small window, which promote their outstanding gas capture ability (C2H2, 131.8 cm3 g-1; CO2, 77.9 cm3 g-1 at 273 K) and selective separation performance (C2H2/CH4, 226.2, CO2/CH4, 50.3 at 298 K), and are also suitable as catalytic reactors for metal/solvent-free chemical fixation of CO2 with epoxides to achieve high-efficiency CO2 conversion. Furthermore, they are greatly recyclable for several cycles while retaining their structural rigidity and catalytic activity.

Drug release and solubility properties of two zeolitic metal-organic frameworks influenced by their hydrophobicity/hydrophilicity.

Metal-organic frameworks (MOFs) have shown significant potential for drug delivery applications. However, there remains a scarcity of comprehensive research addressing the influence of surface properties of MOFs on drug release kinetics and drug solubility. This study focuses on examining the influence of MOFs hydrophilicity and hydrophobicity on the controlled release and solubility of drugs. To achieve this, we prepared drug-loaded nanoparticles through in situ synthesis and created a drug-MOF co-amorphous system using the ball milling technique. Under neutral conditions, the hydrophilic MOF-based drug delivery system demonstrated a comparatively slower drug release profile than its hydrophobic counterpart. This observation suggests that the hydrophilic system holds promise in mitigating drug side effects by enabling improved control over drug release. The implementation of hydrophobic MOFs in co-amorphous systems yields a more pronounced effect on enhancing solubility compared to hydrophilic MOFs. This study offers valuable insights for achieving optimal drug release kinetics and solubility by delicately manipulating surface properties of MOFs.

Hydrogenation of pyrolysis gasoline by novel Ni-doped MOF derived catalysts from ZIF-8 and ZIF-67

Pyrolysis gasoline is the valuable byproduct of the thermal breakdown of heavier oil fractions in an olefin unit with high aromatic content. To separate such aromatic components, firstly, this product should be hydrogenated. In this contribution, new nanostructure catalysts derived from the zeolitic metal–organic framework, namely ZIF-8 and ZIF-67, were used to investigate their hydrogenation capability. Owing to its great hydrogenation capability of Nickle, the structures of the ZIF-8 and ZIF-67 were improved by Nickle through in situ synthesis. Moreover, to enhance the pore size of catalysts and their electronic properties, the synthesized catalysts were pyrolyzed under nitrogen media at 450 °C, and five catalysts, namely Co/NC, ZnCo/NC, ZnNi/NC, CoNi/NC, and ZnCoNi/NC were created. Results indicated that the CoNi/NC showed a superior hydrogenation performance (69.5% conversion of total olefins) to others. In addition, the synthesized catalysts without the carbonization process had no conversion in the hydrogenation process because there is no active site in these structures. The current synthesized catalysts can compete with the costly Pt or Pd-based hydrogenation catalysts due to their high surface area and great electronic properties.

Efficient enrichment of pesticides from environmental water samples by cobalt-nickel double metal hydroxide nanocage/multiwalled carbon nanotube composites

建立高效、灵敏的农药分离、富集和检测方法具有重要意义。该实验采用一步法合成了钴基沸石咪唑骨架/多壁碳纳米管(ZIF-67/MWCNTs)复合物,并以该复合物为模板通过溶剂热法合成了钴镍笼状双金属氢氧化物/多壁碳纳米管(CoNi-LDH/MWCNTs)复合材料,将CoNi-LDH/MWCNTs用作固相微萃取(SPME)的纤维涂层富集环境水样中的6种农药,结合高效液相色谱(HPLC)测定了环境水样中的6种农药。通过扫描电镜、能谱分析、红外光谱、粉末X射线衍射和N2吸附/脱附对所制备的各种材料进行了表征。利用正交设计试验优化SPME的萃取条件,包括萃取温度、萃取时间、搅拌速率、解吸时间和盐浓度。在最优化的条件下,该方法具有较宽的线性范围(百菌清为0.015~200 μg/L,戊唑醇为0.140~200 μg/L,毒死蜱为0.250~200 μg/L,仲丁灵为0.077~200 μg/L,溴氰菊酯为1.445~200 μg/L,哒螨灵为0.964~200 μg/L)、较低的检出限(0.004~0.434 μg/L)和良好的重复性。单个纤维和不同批次纤维间的相对标准偏差(RSD)分别为0.5%~5.7%和0.5%~4.8%。在10.0 μg/L和50.0 μg/L 2个水平下的加标回收率为83.9%~108.2%, RSD< 5.3%。此外,与其他涂层纤维相比,CoNi-LDH/MWCNTs涂层对农药具有更高效的富集能力,这归因于它的高比表面积以及CoNi-LDH/MWCNTs涂层与目标分析物之间存在的π-π堆积作用、疏水作用、阳离子-π相互作用和氢键作用。该方法可以实现环境水样中农药残留的高选择性、高灵敏度及高准确性的分析测定。

Nanoconfinement of tetraphenylethylene in zeolitic metal-organic framework for turn-on mechanofluorochromic stress sensing

Mechanofluorochromic materials are of great significance for the fabrication of innovative sensors and optoelectronics. However, efficient mechanofluorochromic materials are rarely explored due to the deficiency of existing design strategies. Here, we demonstrate the incarceration of aggregation-induced emission (AIE) materials within metal-organic framework (MOF) single crystals to construct a composite system with turn-on mechanofluorochromism. A new type of AIE@MOF material was designed: integrating a zeolitic MOF (ZIF-71) and tetraphenylethylene (TPE, a topical AIE material) to generate a TPE@ZIF-71 system with exceptional turn-on type mechanofluorochromism. Using terahertz vibrational spectroscopy, we show the unique fluorochromism mainly emanates from the enhanced nanoconfinement effect exerted by ZIF-71 host on TPE guest under pressure. Compared with pure TPE, we demonstrate the nanoconfinement in AIE@MOF not only changes the TPE's turn-off type sensing behavior to a turn-on type, but boosts the original sensitivity markedly by tenfold. Significantly, because ZIF-71 prevents the spontaneous recrystallization of TPE upon unloading, this allows TPE@ZIF-71 to record the stress history. This is the first demonstration of the Guest@MOF system combining the concepts of AIE and MOF; its promising properties and potential engineering applications will stimulate new directions pertaining to luminescent stress sensors and smart optics.

Effect of zeolitic metal–organic framework on thermal, mechanical, and electrical properties of Ca/Zn‐stabilized polyvinyl chloride

AbstractIn order to enhance the heat stability of polyvinyl chloride (PVC), several heat stabilizing parameters such as metal content, antioxidant percentage, primary‐to‐secondary antioxidant ratios, stearic‐to‐acetylacetonate ratio, the amounts of pentaerythritol and β‐diketone were studied using oven and Congo red tests. Results indicated that the percentage contribution of the calcium‐to‐zinc molar ratio in the static heat stability was 60.78%. Due to the synergistic effects of the calcium/zinc stabilizer and the zeolitic metal–organic framework (MOF) as an effective co‐stabilizer, the heat stability was increased from 109 to 148 min. The EDX analysis was carried out to determine the mechanism of HCl gas absorption by the zeolitic imidazolate framework‐8 (ZIF‐8) existing in the PVC compound. Furthermore, the Ca/Zn thermal stabilizer showed poor electrical insulating properties, but the ZIF‐8 improved electrical resistivity of the PVC compounds. Volume resistivity of ZIF‐8 was significantly higher than that of the commonly used Ca/Zn stabilizers. Dynamic mechanical thermal analysis and tensile test of the PVC compound containing the ZIF‐8 showed increased Tg and enhanced toughness.

Molecular Intermediate in the Directed Formation of a Zeolitic Metal–Organic Framework

Directed synthesis promises control over architecture and function of framework materials. In practice, however, designing such syntheses requires a detailed understanding of the multistep pathways of framework formations, which remain elusive. By identifying intermediate coordination complexes, this study provides insights into the complex role of a structure-directing agent (SDA) in the synthetic realization of a promising material. Specifically, a novel molecular intermediate was observed in the formation of an indium zeolitic metal-organic framework (ZMOF) with a sodalite topology. The role of the imidazole SDA was revealed by time-resolved in situ powder X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS).

Supercritical Carbon Dioxide Enables Rapid, Clean, and Scalable Conversion of a Metal Oxide into Zeolitic Metal–Organic Frameworks

Supercritical carbon dioxide (CO2) is an established medium for synthesizing molecular compounds and activation of microporous solids, but is much less explored for transformations of high-melting ionic reactants, such as metal oxides. We show that supercritical CO2 enables direct, clean, and rapid transformation of zinc oxide into zeolitic imidazolate frameworks (ZIFs), without requiring toxic or corrosive metal nitrate or chloride precursors, organic or aqueous solvents, additives, or auxiliaries. While recent syntheses of coordination polymers and metal–organic frameworks from supercritical CO2 highlighted the need for specialized metal reagents designed for solubility, we unexpectedly find that ZnO is quantitatively converted into grams of diverse ZIFs in minutes, with hundred grams of popular ZIF-8 accessible within an hour.

An anionic sod-type terbium-MOF with extra-large cavities for effective anthocyanin extraction and methyl viologen detection.

An anionic sod-type zeolitic metal-organic framework [(CH3)2NH2]9{Tb6(η6-TATAT)4(H2O)12}·3Cl·DMA·7H2O [1, H6TATAT = 5,5',5''-(1,3,5-triazine-2,4,6-triyltriimino)tri-1,3-benzenedicarboxylic acid] has been synthesized by metal-ligand directed assembly of hexacarboxylic acid units and Tb3+ ions. Compound 1 with extra-large cavities can efficiently extract natural product anthocyanins from blackberries and release them rapidly into NaCl aqueous solution. And, the nature of the anionic framework makes it very sensitive to detect cationic methyl viologen (MV2+) with a detection limit as low as 1 × 10-8 M.

Synthesis of homochiral zeolitic metal–organic frameworks with amino acid and tetrazolates for chiral recognition

By mixing amino acids and tetrazolate ligands, a series of homochiral zeolitic metal–organic frameworks (ZMOFs) with ABW topology have been synthesized, which show permanent microporosity and potential enantioselective recognition ability.

Tuning crystalline structure of zeolitic metal–organic frameworks by supersonic spraying of precursor nanoparticle suspensions

The deposition of sodalite zeolitic imidazolate framework-7 (ZIF7) films by a supersonic cold-spraying technique was successfully accomplished for the first time. The high-speed impact of supersonic cold spraying increased the monodispersity of the ZIF7 crystalline structure. However, the intensity of the structural change decreased with increasing the amount of nylon in the ZIF7 suspension. Mitigating phase changes in ZIF7 occurred by the impact dampening conferred by the polymeric nature of nylon, which preserved the original three-dimensional crystalline structure of ZIF7. The inclusion of N,N-dimethylformamide (DMF) in a nylon–ZIF7 suspension improved the dispersion of ZIF7 nanoparticles, which in turn eliminated the dampening effect from the nylon and recovered the distinctive monodispersity arising from the high-speed impact. This characteristic was observed at all impact speeds for ZIF7 suspensions containing DMF. We show that high-rate cold spraying of ZIF7 particles can be combined with nylon and other pressure-transmitting media to control the formation of three distinctive phases. The unique capability to tune the crystalline structure of ZIF7 allows customization of the film functionality for specific applications.

Two Dynamic ABW-Type Metal Organic Frameworks Built of Pentacarboxylate and Zn2+ as Photoluminescent Probes of Nitroaromatics

Self-assembly reactions of Zn2+ and L5– (H5L = 2,5-(6-(4-carboxyphenylamino)-1,3,5-triazine-2,4-diyldiimino) diterephthalic acid) lead to the formation of two new ABW-type zeolitic metal–organic frameworks (Z-MOFs): (Me2NH2)[Zn2L]·3.5DMF (1) and (Me2NH2)[Zn2L(H2O)]·2DMF·8H2O (2) (DMF = N,N-dimethylformamide). They are the first two Z-MOFs which are built of the same pentacarboxylate ligand and metal ion but have two configurations and channel shapes (distorted honeycomb- and herringbone-shaped channels for 1 and 2 respectively). They can demonstrate interesting structural transformations triggered by vacuum heating or soaking in different solvents. While direct transformations between 1 and 2 were revealed to be not feasible, 2 could be first transformed to a crystalline intermediate 3 and then into 1. Furthermore, while transformations between 2 and 3 are irreversible, those between 1 and 3 are reversible, accompanied by a 26 nm shift of their emission peak positions. In comparison to the ligand, 1, 2, a...

Dynamic molecular interactions between polyurethane and ZIF-8 in a polymer-MOF nanocomposite: Microstructural, thermo-mechanical and viscoelastic effects

Polymer-based nanocomposites incorporating porous hybrid materials is fast becoming a staple in addressing environmental and sustainability challenges. Herein we investigate the intricate dynamics underpinning the molecular interactions between the porous nanoparticles of a zeolitic metal-organic framework (ZIF-8) and a hyperelastic polymer matrix (polyurethane, PU). We fabricated novel PU/ZIF-8 mixed-matrix nanocomposite membranes (∼100 μm thickness) with up to 40 wt.% ZIF-8 nanoparticles, and characterised their quasi-static and dynamic thermo-mechanical properties via dynamic mechanical measurements, nanoindentation, thermogravimetric and tensile experiments. ZIF-8 nanoparticles significantly modify the thermo-mechanical properties of polyurethane matrix, improving overall stiffness, fracture energy, and yield strength at the cost of ductility (beyond ∼30 wt.%). Thermal stability was enhanced, likewise dynamic responses and phase changes were stabilised with increasing nanoparticle loading. Secondary molecular interactions between ZIF-8 nanoparticles and polyurethane chains are responsible for the salient thermo-mechanical and dynamic behaviour observed. Our findings may guide developments of resilient rubbery-MOF nanocomposite systems for practical applications.

Supersonic cold spraying for zeolitic metal–organic framework films

We describe the first use of high-rate supersonic spray coating to deposit thin films of ZIF-8, a zeolitic metal–organic framework (MOF), adopting a sodalite architecture. This cold-spray technique is versatile and scalable, with tunable processing parameters capable of generating either a textured crystalline film or a randomly oriented polycrystalline coating on both metallic and non-metallic substrates. We provide evidence that guest occupancy by organic solvents (dimethylformamide, dimethylacetamide, and dimethylsulfoxide) in the sodalite cage of ZIF-8 structurally stabilizes the framework against high-velocity impact, resulting in the preferred orientations observed. Moreover, we show that amorphous ZIF-8 films can be straightforwardly obtained at high air pressure exceeding 7bars in which the particle velocity is ∼500m/s. It is anticipated that this high-throughput approach can be adapted to fabricate microstructurally compact and strongly adhered ZIF-8 films.

Explaining the mechanical mechanisms of zeolitic metal-organic frameworks: revealing auxeticity and anomalous elasticity.

The comprehensive elastic properties of Zeolitic Imidazolate Frameworks (ZIF-1 to ZIF-4) have been computed using density functional theory (DFT). We employed the periodic CRYSTAL14 code to calculate the single-crystal elastic coefficients (Cij) at the B3LYP level of theory. While the chemical compositions of ZIFs-1 to -4 are the same, each structure features a distinct network topology, crystal symmetry and porosity configuration, which translate into differential structure-function mechanical correlations. We elucidate the anisotropic mechanical response with respect to the directionally dependent Young's and shear moduli properties. Our theoretical results suggest that ZIF-3 adopting a dft topology has an extremely low shear resistance (Gmin = 0.1 GPa), which is also underpinning the flexible mechanism responsible for its negative Poisson's ratio (auxetic νmin = -0.43). Interestingly, we identified that ZIF-1, ZIF-2, and ZIF-4 could exhibit a nearly zero Poisson's ratio for certain crystal orientations, which is reminescent of a rare "cork-like" phenomenon where there is practically no lateral deformation corresponding to an applied axial strain. Furthermore, we determined the bulk moduli and linear compressibilities, alongside the averaged elastic properties of the ZIF polycrystals.

Enantiopure anion templated synthesis of a zeolitic metal-organic framework.

Utilizing (R)-H3CIA as a chiral template, an unprecedented homochiral metal-organic framework (MOF) with zeotype GIS topology is obtained from achiral 1.4-DIB ligands and Zn(II) ions, which opens up a feasible approach to create zeolitic MOFs with homochirality.

Mechanical properties of zeolitic metal–organic frameworks: mechanically flexible topologies and stabilization against structural collapse

We report the low elastic modulus of a zeolitic MOF, along with stabilization against structural collapse by filling with solvent.