Hierarchical Metal-organic Frameworks Research Articles

Portable and highly enhanced surface enhanced Raman scattering and photocatalytic activity of cost-effective hierarchical hollow metal organic frameworks heterostructures induced by etched titanium sheet

In order to effectively detect and remove organic toxics in wastewater, the facile construction of plug and play bifunctional materials is very vital. Herein, a kind of metal-organic frameworks (MIL-53 (Fe) with hollow tubular structure was induced by an etched Ti sheet (ET), and then small sized Ag nanoparticles (Ag NPs) were in-situ anchored evenly on the internal and external surfaces of MIL-53 (Fe). Subsequently, a new type of bifunctional material (ETMA) was assembled. Surface enhanced Raman scattering (SERS) and photocatalytic activity of the material were investigated with crystal violet (CV, a carcinogenic and teratogenic toxic) as an analyte. The results found that trace amount of CV (1 × 10−12 M) can still be sensitively detected by the fabricated ETMA, and analysis enhancement factors as high as 6.9 × 105 even though only 1.39 wt % Ag was contained in the ETMA. Moreover, nearly 100 % of CV can be rapidly degraded by the ETMA after irradiated for 15 min, which was 44.47 times and 7.27 times faster than those of ET-Ag (ETA) and ET-MIL-53 (Fe) (ETM), respectively. Additionally, the removal efficiency of total organic carbon (TOC) was as high as 75.44 %. The remarkable enrichment effect, the strong interaction among components, and the synergistic effect in the target ETMA material were responsible to the dramatically enhanced SERS and photocatalytic performances. In addition, the cost-effective ETMA exhibited excellent uniformity, repeatability, stability, and recyclability towards the detection and removal of CV in actual water samples, showing great potentials in monitoring and removing organic pollutants in practical ecological environment.

A Hierarchical Metal-Organic Framework Composite Aerogel Catalyst Containing Integrated Acid, Base, and Metal Sites for the One-Pot Catalytic Synthesis of Cyclic Carbonates.

Catalysis has played a decisive role in the development of unique chemical reactions to produce important chemicals. However, conventional stepwise synthetic routes that rely on individual catalysts to promote each step often suffer from ponderous processes for the isolation of intermediates that result in massive material losses and large economic expenditures. In addition, traditional powder forms of these catalysts suffer from poor processability and recoverability. Herein, we designed and prepared a hierarchical metal-organic framework (MOF) composite monolithic catalyst IL-Au@UiO-66-NH2/CMC that contains integrated acid (Zr4+), base (ionic liquid (IL)), and metal sites (Au nanoparticles (NPs)) to promote the one-pot preparation of cyclic carbonates from styrene derivatives and CO2. Highly dispersed Au NPs, IL 1-aminoethyl-3-methylimidazolium bromide ([C2NH2 MIM] [Br]), and MOF-positioned Lewis acid sites within this composite aerogel are separately responsible for catalyzing selective epoxidation of the styrene derivatives and the subsequent cycloaddition reaction of CO2 with intermediate styrene oxides. Importantly, inclusion of the imidazolium-based IL effectively modulates the size and chemical microenvironment of the Au NPs via electrostatic protection, leading to catalyst stability and its selective oxidation of styrene. Benefiting from the rapid mass transfer and high exposure of active sites within the pore-rich hierarchical nanostructure, IL-Au@UiO-66-NH2/CMC promotes high conversion (90.5%) of the styrene and selectivity (80.5%) for styrene carbonate (SC) formation in the one-pot process, a performance level that far exceeds those of related catalysts containing only Au NPs or IL (the selectivity of SC < 42%). Furthermore, the composite aerogel catalyst can be readily separated and recycled at least five times without a remarkable loss of activity and selectivity. The controllable integration of various active components in the hierarchical MOF composite aerogel herein should serve as the foundation for the design of multifunctional monolithic catalysts for other valuable tandem processes.

Controlled Growth of Highly Defected Zirconium-Metal-Organic Frameworks via a Reaction-Diffusion System for Water Remediation.

The relentless growth of metal-organic framework (MOF) chemistry is paralleled by the persistent urge to control the MOFs physical and chemical properties. While this control is mostly achieved by solvothermal syntheses, room temperature procedures stand out as more convenient and sustainable pathways for the production of MOF materials. Herein, a novel approach to control the crystal size and defect numbers of a dihydroxy-functionalized zirconium-based metal-organic framework (UiO-66(OH)2) at room temperature is reported. Through a reaction-diffusion method in a 1D system, zirconium salt was diffused into an agar gel matrix containing the organic linker to form nanocrystals of UiO-66(OH)2 with tailored structural features that include crystal size distribution, surface area, and defect number. By variation of the synthesis parameters of the system, hierarchical MOF nanocrystals with an average size ranging from 30 nm up to 270 nm and surface areas between 201 and 500 m2 g-1 were obtained in a one-pot synthetic route. To stress the importance of crystal size, morphology, and structural defects on the adsorption properties of UiO-66(OH)2, the adsorption capacity of the MOF toward methylene blue dye was tested with the largest and most defected crystals achieving the best performance of 202 mg/g. The distinctive structural characteristics including the hierarchical micromesoporous frameworks, the nanosized particles, and the highly defective crystals obtained by our synthesis procedure are deemed challenging through the conventional synthesis methods. This work paves the way for engineering MOF crystals with tunable physical and chemical properties, using a green synthesis procedure, for their advantageous use in many desirable applications.

Isolation of Sensing Units and Adsorption Groups Based on MOF-on-MOF Hierarchical Structure for Both Highly Sensitive Detection and Removal of Hg2.

Bifunctional materials have attracted ongoing interest in the field of detection and removal of contaminants because of their integration of two functions, but they exhibit commonly exceptional performance in only one of these two aspects. The interaction between the two functional units of the bifunctional materials may compromise their sensing and adsorption abilities. Guided by the concept of domain building blocks (DBBs), a hierarchical metal-organic framework (MOF)-on-MOF hybrid was designed by growing gold nanoclusters (AuNCs)-embedded zeolitic imidazolate framework 8 (AuNCs/ZIF-8) on the surface of Zr-MOF (UiO-66-NH2) for the simultaneous detection and removal of Hg2+. In the hybrid, the amino groups (-NH2) and AuNCs─which were the adsorption groups and sensing units, respectively, were isolated from each other. Specifically, the adsorption groups (-NH2) were assembled in the inner UiO-66-NH2 layer, while the sensing units (AuNCs) were confined in the outer ZIF-8 layer. This hierarchical structure not only spatially hindered the electron transfer between these two units but also triggered the aggregation-induced emission of AuNCs because of the confinement of ZIF-8 on the AuNCs, thus changing the fluorescence of AuNCs from quenching to enhancement. The newly prepared UiO-66-NH2@AuNCs/ZIF-8 hybrid, as expected, showed an ultralow detection limit (0.42 ppb) and a high adsorption capacity (129.9 mg·g-1) for Hg2+. Overall, this work provides a feasible approach to improve the integrated performance of MOF-based composites based on DBBs.

Flexible hierarchical polypyrrole-coated Cu-BTC MOFs photothermal textile for efficiently solar water evaporation and wastewater purification

Solar-driven interfacial water evaporation (SDIWE) endures a significant potential for producing clean water from seawater and wastewater because it requires no additional energy source. Photothermal materials with efficient solar absorption and pollutant removal capabilities are critical for SDIWE. However, an efficient and facile strategy to prepare a high-performance and flexible photothermal material and simultaneously prevent the salt accumulation for efficient and long-term steady evaporation to produce potable water from seawater and wastewater is still a challenge. Herein, based on the MS and ALD processes, two novel flexible photothermal materials are synthesized using the flexible polyester fabric substrate, hierarchical metal–organic framework Cu-BTC MOFs, and polypyrrole (PPy) as a light-absorption layer. In particular, under the synergistic effect of the hierarchical porous Cu-BTC MOFs and PPy with excellent solar absorption, the flexible photothermal material possesses excellent light absorption (92.58 % ∼ 93.98 %), super hydrophilicity, low thermal conductivity, high evaporation rate (1.53 ∼ 1.56 kg m-2h−1 for 15 days), outstanding salt resistance (1.42 kg m-2h−1 at a salinity of 15 wt%), and excellent metal ions and organic pollutants removal capacity after solar evaporation. These multifunctional properties ensure its great application prospect for future freshwater production while also providing a new reference for other applications.

Recent Advances in Hierarchical Porous Engineering of MOFs and Their Derived Materials for Catalytic and Battery: Methods and Application.

Hierarchical porous materials have attracted the attention of researchers due to their enormous specific surface area, maximized active site utilization efficiency, and unique structure and properties. In this context, metal-organic frameworks (MOFs) offer a unique mix of properties that make them particularly appealing as tunable porous substrates containing highly active sites. This review focuses on recent advances in the types and synthetic strategies of hierarchical porous MOFs and their derived materials. Furthermore, it highlights the relationship between the mass diffusion and transport of hierarchical porous structures and the pore size with examples and simulations, while identifying their potential and limitations. On this basis, how the synthesis conditions affect the structure and electrochemical properties of MOFs based hierarchical porous materials with different structures is discussed, highlighting the prospects and challenges for the synthetization, as well as further scientific research and practical applications. Finally, some insights into current research and future design ideas for advanced MOFs based hierarchical porous materials are presented.

Fast Gas-Adsorption Kinetics in Supraparticle-Based MOF Packings with Hierarchical Porosity.

Metal-organic frameworks (MOFs) are microporous adsorbents for high-throughput gas separation. Such materials exhibit distinct adsorption characteristics owing to the flexibility of the crystal framework in a nanoparticle, which can be different from its bulk crystal. However, for practical applications, such particles need to be compacted into macroscopic pellets, creating mass-transport limitations. In this work, this problem is addressed by forming materials with structural hierarchy, using a supraparticle-based approach. Spherical supraparticles composed of nanosized MOF particles are fabricated by emulsion templating and they are used as the structural component forming a macroscopic material. Zeolitic imidazolate framework-8 (ZIF-8) particles are used as a model system and the gas-adsorption kinetics of the hierarchical material are compared with conventional pellets without structural hierarchy. It is demonstrated that a pellet packed with supraparticles exhibits a 30 times faster adsorption rate compared to an unstructured ZIF-8 powder pellet. These results underline the importance of controlling structural hierarchy to maximize the performance of existing materials. In the hierarchical MOFs, large macropores between the supraparticles, smaller macropores between individual ZIF-8 primary particles, and micropores inherent to the ZIF-8 framework collude to combine large surface area, defined adsorption sites, and efficient mass transport to enhance performance.

Multilength Scale Hierarchy in Metal‐Organic Frameworks: Synthesis, Characterization and the Impact on Applications

AbstractEvolutionary selection in nature has led to hierarchical structuring as a fundamental optimization strategy for biological structures, maximizing functional performance while minimizing resource usage. Precise hierarchical organization of natural materials over a wide range of length scales gives rise to unique synergistic properties that could not be achieved by single components. Despite the clear advantages offered by hierarchically structuring matter, mastering hierarchical control based on the current synthetic toolbox is still a challenge. In this review, some recent advancements in the fabrication of hierarchical metal organic framework (MOF) materials are highlighted and the advantages that arise due to different kinds of MOF hierarchy are critically analyzed. The special focus of the review lies in highlighting the applications where MOF hierarchical materials can be most impactful and describing characterization techniques currently at the disposal of scientists for the precise characterization of MOF hierarchical structures across all length scales. Finally, the intent is to inspire reticular chemists to master hierarchical control of MOF materials so as to fully utilize the advantages MOFs offer for various applications.

Controlled Partial Linker Thermolysis in Metal-Organic Framework UiO-66-NH2 to Give a Single-Site Copper Photocatalyst for the Functionalization of Terminal Alkynes.

Metal-organic frameworks (MOFs) with expanding porosity and tailored pore environments are intriguing for catalytic applications. We report herein a straightforward method of controlled partial linker thermolysis to introduce desirable mesopores into mono-ligand MOFs, which is different from the classical thermolyzing method that starts from mixed-linker MOFs. UiO-66-NH2 , after partial ligand thermolysis, exhibits significant mesoporosity, retained crystal structure, improved charge photogeneration and abundant anchoring sites, which is ideal to explore single-site photocatalysis. Atomically dispersed Cu is then accommodated in the tailored pore. The resulting single-site Cu catalyst exhibits excellent performance for photocatalytic alkylation and oxidation coupling for the functionalization of terminal alkynes. The study highlights the advantage of controlled partial linker thermolysis to synthesize hierarchical MOFs to achieve the advanced single-site photocatalysis.

Enhancing Ru(bpy)32+@TMU-13 electrochemiluminescence for ultrasensitive detection of AFP by a signal amplification strategy based on flower-like Au NPs/CoFe LDO/MoS2 NFs as double coreaction accelerators

A signal amplification strategy based on a Ru(bpy)32+ luminescence functionalized metal-organic framework (MOF) and double coreaction accelerators was developed for the detection of alpha-fetoprotein (AFP) by electrochemiluminescence (ECL). The high porosity and rich functional groups of MOF can improve the binding rate of biomolecules. Therefore, Ru(bpy)32+ was encapsulated by the three-dimensional hierarchical porous MOF TMU-13 as the luminescence nanoreactor. The complex exhibits stable and excellent luminescence efficiency and rich carboxyl functional groups, which can support enough antibodies. In addition, the process of K2S2O8 reduction was promoted by double coreaction accelerators, including MoS2 grown in CoFe LDOs in situ and in situ reduction of gold nanoparticle (AuNPs) nanoflower structures (AuNPs/CoFe LDO/MoS2 NFs), the ECL signal in the cathode was significantly increased. Under optimal conditions, the established AFP detection method exhibited a wide linear range of 10−5 ng·mL−1 to 100 ng·mL−1, and the detection limit was as low as 3.23 fg·mL−1. Importantly, this strategy shows great potential for application in the field of bioanalysis.

In-situ confined growth of defective MIL-100(Fe) in macroporous polyacrylate spherical substrate at room temperature for high-efficient toluene removal

The hazard caused by toluene has attracted worldwide attention, and it is of practical significance to study the efficient adsorption of toluene for environmental governance. In this work, a hierarchical metal–organic framework (MOF), MIL-100(Fe), was crystallized on the surface of a macroporous polyacrylate (PAA) spherical substrate at room temperature through an in-situ confinement growth strategy to form MIL-100(Fe)@PAA composite. By decreasing the nucleation energy barrier, the average size of MIL-100(Fe) crystals was reduced from 400 nm to 55 nm and defects as adsorption sites for toluene were able to install in the crystal lattices. Therefore, the composite provided excellent static and dynamic adsorption properties for toluene, much better than the pristine MIL-100(Fe). The potential mechanism for crystal defects to significantly improve the adsorption performance was subsequently explored through kinetic fitting and density functional theory (DFT) calculation. All results indicated that the innovative MIL-100(Fe)@PAA prepared using defect engineering and effective molding technology was potent in both toluene removal and regeneration, which was expected to provide a new avenue for the facile synthesis of molded MOF composites.

A Composite of Hierarchical Porous MOFs and Halloysite Nanotubes as Single-Ion-Conducting Electrolyte Toward High-Performance Solid-State Lithium-Ion Batteries.

Metal-organic frameworks (MOFs), as a promising rechargeable electrochemical energy storage material have emerged in the field of solid-state lithium batteries. However, low ionic conductivity and high interfacial impedance still severely hamper the application of MOF-based solid-state electrolytes (SSE). In this work, a novel hierarchical porous H-ZIF-8 solid-state electrolyte (SSE) material is harvested through the in situ growth of zinc nitrate hydroxide nanosheets, expressing excellent ion conductivity of 1.04 × 10-3 Scm-1 and Li+ -transference number of 0.71. Moreover, the morphology and structure of H-ZIF-8 is further optimized to obtain a composite H-ZIF-8/HNT by decorating halloysite nanotubes (HNT). Notably, functionalized H-ZIF-8/HNT as an electrolyte presents obvious enhancement on electrochemical properties: higher ionic conductivity of 7.74 × 10-3 Scm-1 , better single-ion transmittability ( = 0.84), good interfacial compatibility as well as excellent rate performance. More importantly, the Li/LiFePO4 battery equipped with H-ZIF-8/HNT SSE has efficient lithium-dendrite suppression and up to 84% capacity retention (104.16mAhg-1 ) after 200 times galvanostatic charge/discharge cycles. This work enriches the solid-state lithium-ion composite electrolyte materials, opening an entirely new way for enhancing electrochemical performance.

A novel bienzymatic bioreactor based on magnetic hierarchical porous MOF for improved catalytic activity and stability: Kinetic analysis, thermodynamics properties and biocatalyst applications

Metal-organic frameworks (MOFs) have been regarded as ideal carriers for enzyme immobilization owing to their unique structural characteristics. Whereas, enzyme activity and catalytic efficiency are seriously influenced owing to the conformation change of enzyme molecules during immobilization and the increase of substrate mass transfer resistance during catalysis. Herein, for the first time, we designed a novel magnetic hierarchical micro- and mesoporous metal-organic framework (mH-UiO-66(Zr)) as a platform for co-immobilizing horseradish peroxidase (HRP) and glucose oxidase (GOx). The obtained mH-UiO-66(Zr) with magnetic performance and hierarchical structure can effectively inhibit enzyme leakage, and reduce the material loss caused by centrifugation and the mass transfer resistance of substrate. Notably, the bienzyme bioreactor (GOx&HRP@mH-UiO-66(Zr)) was accurately constructed online in situ by microcalorimetry, which exhibited outstanding catalytic efficiency and superior stability against organic solvents, pH and temperature and favourable reusability, maintaining 95.1% of the original activity after 1 h incubation at 70 °C and over 90% initial activity after 15 cycles. Kinetics and thermodynamics investigation revealed the enhanced affinity of GOx&HRP@mH-UiO-66(Zr) for substrates. Furthermore, GOx&HRP@mH-UiO-66(Zr) has been utilized for the rapid detection and efficient degradation of 2,4-dichlorophenol (2,4-DCP), ensuring bio-catalytic material a bright potential application in environmental remediation.

Constructing cactus-like mixed dimensional MOF@MOF as sorbent for extraction of bisphenols from environmental water

Metal-organic frameworks (MOFs) received considerable attention to adsorption and removal of various environmental pollutants because of some inherent advantages. However, it is challenging but meaningful to design and fabricate hierarchical mixed-dimensional MOFs with synergistic effects to enhance the performance for removal and preconcentration of environmental pollutants. Herein, a new hierarchical two-dimensional (2D)-three-dimensional (3D) mixed-dimensional cactus‐like MOF@MOF hybrid material (PCN-134@Zr-BTB) was prepared by in-situ growth of 2D MOF nanosheets (Zr-BTB) on the surface of 3D MOF (PCN-134). The PCN-134@Zr-BTB composites combine the advantages of 2D and 3D MOFs with extensive mesoporous structures and large surface area for effective removal and enrichment of bisphenols (BPs). In comparison with pristine PCN-134 and Zr-BTB materials, the PCN-134@Zr-BTB hybrid material presented excellent adsorption performance for BPs. The adsorption isotherms are consistent with the Langmuir model, and the maximum adsorption capacity of four bisphenols (BPs) ranged from 135.1 mg/g to 628.9 mg/g. The adsorption kinetics are in accordance with the pseudo-second-order model. The recoveries ranged from 72.8% to 108%. The limits of detection were calculated at 0.02–0.03 ng/mL. The enrichment factors were calculated in the range of 310–374. According to FT-IR and XPS analysis, the main adsorption mechanisms are hydrogen bonding and π-π stacking. Nevertheless, this work provides a new and convenient strategy for the preparation of new hierarchical mixed-dimensional MOF@MOF (PCN-134@Zr-BTB) hybrid material for extraction and enrichment of BPs from aqueous matrix.

Rapid synthesis of hierarchical cerium-based metal organic frameworks for carbon dioxide adsorption and selectivity

The creation of innovative porous materials for CO2 capture and separation is proving extremely relevant for environmental sustainability and global warming mitigation. In this study, modified Ce-UiO-66 MOFs were synthesized in 10 min using simultaneous microwave and ultrasound irradiation method. The porosity of the MOF was altered using the soft-templating approach. This strategy resulted in the construction of a hierarchically micro-mesoporous structure with an average mesopore size of 11.10 nm. The as-obtained MOFs, abbreviated as CUT, were characterized with SEM, XRD, FTIR, TGA, BET, and evaluated as CO2 adsorbents. The results displayed preserved crystal structure, higher thermal stability up to 570 °C. The heightened diffusion of CO2 molecules to the micropores promoted by mesopore channels, endued CUT with an over-all CO2 adsorption uptake of 2.53 mmol/g at 273 K at 1 bar outperforming equivalent Ce-UiO-66 MOFs. Notably, the CUT adsorbent showed improved CO2/N2 IAST selectivity (34.2 vs 24.6) and CO2 isosteric heat of adsorption (Qst = 30.15 vs 25 kJ/mol) in contrast to pristine UiO-66 (Zr).

Facile synthesis of hierarchical porous MOFs via competition coordination strategy: A sustainable adsorbent for efficient removal of fluorine-containing drugs

Construction of hierarchically porous structure of metal–organic frameworks (MOFs) can improve the accessibility of active sites and mass transfer rate to improve practical applications effects such as adsorption efficiency. Rapid synthesis of hierarchically porous MOFs (HP-MOFs) at an industrial scale is extremely important from the perspective of sustainable development and economical practicality. Here, we propose a strategy to rapidly synthesize HP-MOFs at room temperature, using hydroxy double salts (HDS) as an intermediate to combine two ligands with different electronegativity to generate competitive coordination during the nucleation stage. Using this method, we can obtain HP-Zn-MOFs within 20 min at room temperature, with larger pores (average pore size > 8 nm) and higher space–time yield (STY > 3000 kg m−3 d−1). All the raw materials are low cost and low toxicity, which is consistent with the concept of green chemistry. More than that, the as-synthesized HP-Zn-MOFs have an excellent adsorption effect in removing fluorine-containing drugs (FCDs) through multiple interactions, showing good reusability, practical application, and good adsorption for other drugs. This work demonstrates the feasibility of the green synthesis of HP-MOFs through competition coordination methods at room temperature, which highlights the potential for the elimination of contaminants.

ZIF-8@Zn-MOF-74 core–shell metal–organic framework (MOF) with open metal sites: Synthesis, characterization, and gas adsorption performance

In this paper, an efficient hierarchical metal–organic framework (MOF), namely ZIF-8@Zn-MOF-74 with core–shell structure and coordinately open/unsaturated metal sites (OMS) was successfully synthesized. For this purpose, the facile post-synthetic ligand exchange (PSE) method at ambient temperature was applied. In the fabricated core–shell porous structure, the SOD-type ZIF-8 acts as the core, providing molecular sieving features, resulting in greater adsorption selectivity values. On the other hand, Zn-MOF-74 as the shell part, owing to the larger pore size, makes entrance and diffusion of the guest gas molecules more convenient. In addition, due to the presence of OMS in the Zn-MOF-74 structure, a greater adsorption capacity would be achieved. The prepared MOFs were characterized by FESEM, EDS, HRTEM, FTIR, XRD, BET, and TGA analyses, and formation of the core–shell structure was confirmed. The FESEM and HRTEM images demonstrated rather smooth coverage of the core (ZIF-8) with a layer of the shell (Zn-MOF-74). The rather high BET surface area (633.2 m2/g) and total pore volume (0.671 cm3 g−1) of the core–shell structure, make it promising for gas adsorption applications. The gas adsorption measurements were conducted for CO2, N2, H2, O2, CH4, C2H6, C3H8, C2H4, and C3H6 pure gases at 308 K and equilibrium pressures up to 4 bar. It was found that the CO2 adsorption capacity of ZIF-8@Zn-MOF-74 nanoparticles (3.27 mmol g−1) has enhanced ∼63.5 % compared to the pristine ZIF-8 (∼2 mmol/g). The CO2/N2 and CO2/CH4 selectivity values were also increased by 85.4 % and 74.4 %, respectively, that indicates overcoming the trade-off between adsorption capacity and selectivity.

Crystal Growth Blocking Strategy Enabling Efficient Solvent-Free Synthesis of Hierarchical UiO-66 for Large-Molecule Catalysis

Metal–organic frameworks (MOFs) with rich hierarchical structures have attracted great attention in processes with large molecules, such as catalysis and adsorption. However, efficiently and cost-effectively fabricating hierarchical MOFs with robust stability remains challenging. Herein, we report a crystal growth blocking strategy to prepare hierarchical UiO-66 by a solvent-free method. The addition of FeCl3 to the synthetic system blocks the overgrowth of UiO-66 crystals and limits the particle size to around just 12 nm. After the removal of Fe by ethanol treatment, these small particles loosely aggregate and gain intercrystalline mesopores. The optimal sample Mes-UiO-66 exhibits a well-developed hierarchical structure, the BET surface area reaches 1161.9 m2 g–1, and the mesopore volume attains a state-of-the-art 1.21 cm3 g–1. The superior catalytic performance and the robust stability of Mes-UiO-66 are demonstrated by the oxidation of DBT, in which the DBT conversion surpasses 99% and shows a slight decrease after five cycles. Our finding may provide a novel platform for efficiently fabricating hierarchical MOFs for large-molecule catalysis.

Surfactant-assisted mesopores in hierarchical metal-organic frameworks for the immobilization of model protein Cyt c.

A hierarchical metal-organic framework, H-mMOF-1 (representing hierarchical medi-MOF-1), was successfully synthesized by the coassembly of MOF starting reagents and a triblock copolymer surfactant F127. The obtained H-mMOF-1 retained its microporous structure but also exhibited mesopores with a size range from 3 to 10 nm. The mesopores were able to accommodate protein Cyt c with a loading capacity of 160 mg g-1. The surfactant-assisted synthesis of hierarchical MOFs provides promising applications for enzyme immobilization.

Molecular dissolution behaviors on porous membrane surface using hierarchical metal–organic framework lamellar membrane

AbstractLamellar membranes, especially assembled by microporous framework nanosheets, have excited interest for fast molecular permeation. However, the underlying molecular dissolution behaviors on membrane surface, especially at pore entrances, remain unclear. Here, hierarchical metal–organic framework (MOF) lamellar membranes with 7 nm‐thick surface layer and 553 nm‐thick support layer are prepared. Hydrophilic (–NH2) or hydrophobic (–CH3) groups are decorated at pore entrances on surface layer to manipulate wettability, while –CH3 groups on support layer provide comparable, low‐resistance paths. We demonstrate that molecular dissolution behaviors are determined by molecule–molecule and molecule–pore interactions, derived from intrinsic parameters of molecule and membrane. Importantly, two dissolution model equations are established: for hydrophobic membrane surface, dissolution activation energy (ES) obeys ES = Kmln[(γL‐γC)μd2], while turns to ES=Kaln[(γL‐γC)δeμd2] for hydrophilic one. Particularly, hydrophilic pore entrances exert strong interaction with polar molecules, thus compensating the energy consumed by molecule rearrangement, giving fast permeation (&gt;270 L m−2 h−1 bar−1).