Metal-Organic Frameworks in Surface Enhanced Raman Spectroscopy-Based Analysis of Volatile Organic Compounds

Volatile Organic Compounds (VOC) are a major class of environmental pollutants hazardous to human health, but also highly relevant in other fields including early disease diagnostics and organoleptic perception of aliments. Therefore, accurate analysis of VOC is essential, and a need for new analytical methods is witnessed for rapid on-site detection without complex sample preparation. Surface-Enhanced Raman Spectroscopy (SERS) offers a rapidly developing versatile analytical platform for the portable detection of chemical species. Nonetheless, the need for efficient docking of target analytes at the metallic surface significantly narrows the applicability of SERS. This limitation can be circumvented by interfacing the sensor surface with Metal-Organic Frameworks (MOF). These materials featuring chemical and structural versatility can efficiently pre-concentrate low molecular weight species such as VOC through their ordered porous structure. This review presents recent trends in the development of MOF-based SERS substrates with a focus on elucidating respective design rules for maximizing analytical performance. An overview of the status of the detection of harmful VOC is discussed in the context of industrial and environmental monitoring. In addition, a survey of the analysis of VOC biomarkers for medical diagnosis and emerging applications in aroma and flavor profiling is included.

Exploring Synthesis Strategies and Interactions between MOFs and Drugs for Controlled Drug Loading and Release, Characterizing Interactions Through Advanced Techniques

This study explores various aspects of Metal-Organic Frameworks (MOFs), focusing on synthesis techniques to adjust pore size and key ligands and metals for crafting carrier MOFs. It investigates MOF-drug interactions, including hydrogen bonding, van der Waals, and electrostatic interactions, along with kinetic studies. The multifaceted applications of MOFs in drug delivery systems are elucidated. The morphology and structure of MOFs are intricately linked to synthesis methodology, impacting attributes like crystallinity, porosity, and surface area. Hydrothermal synthesis yields MOFs with high crystallinity, suitable for catalytic applications, while solvothermal synthesis generates MOFs with increased porosity, ideal for gas and liquid adsorption. Understanding MOF-drug interactions is crucial for optimizing drug delivery, affecting charge capacity, stability, and therapeutic efficacy. Kinetic studies determine drug release rates and uniformity, vital for controlled drug delivery. Overall, comprehending drug-MOF interactions and kinetics is essential for developing effective and controllable drug delivery systems.

Impact of copper and cobalt-based metal-organic framework materials on the performance and stability of hole-transfer layer (HTL)-free perovskite solar cells and carbon-based

This article investigates the impact of metal-organic frameworks (MOFs) on the performance and stability of perovskite solar cells (PSCs), specifically focusing on the type of metal and the morphology of the MOF. Two types of MOFs, copper-benzene-1,3,5-tricarboxylate (Cu-BTC MOF) with spherical morphology and cobalt-benzene-1,3,5-tricarboxylate (Co-BTC MOF) with rod morphology, are synthesized and spin-coated on TiO2 substrates to form FTO/TiO2/MOF/CH3NH3PbI3/C-paste PSCs. The morphology and size of the MOFs are characterized by scanning electron microscopy (SEM), and the crystallinity and residual PbI2 of the perovskite films are analyzed by X-ray diffraction (XRD). The results show that the Co-BTC MOF PSC exhibits the highest power conversion efficiency (PCE) of 10.4% and the best stability, retaining 82% of its initial PCE after 264 h of storage in ambient air. The improved performance and stability are attributed to the enhanced crystallinity and reduced residual PbI2 of the perovskite film after Co-BTC MOF modification. The paper showcases the immense potential of MOF-based interlayers to revolutionize PSC technology, offering a path toward next-generation solar cells with enhanced performance and longevity.

Dual-Functional Manganese-Doped ZnO-MOF Hybrid Material with Enhanced Hydrolytic Stability: A Fluorescent Photoinduced Electron Transfer Sensor for the Ultraselective Detection of Acetic Acid and Chromium (VI)

In recent years, the synthesis of metal-organic framework (MOF)─nanocomposites has received wide attention from the scientific fraternity due to the presence of a tunable hierarchical architecture and invasive versatility in applications. The present work focuses on the solvothermal synthesis of a novel hybrid MOF-nanocomposite through the impregnation of Mn-doped ZnO nanoparticles onto the matrix of a pioneer metal-organic framework that is composed of zinc metal connected with terephthalic acid linkers (MOF-5). The hierarchical arrangements of the prepared material were further assessed by Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), high-resolution transmission electron microscopy (HR-TEM), UV-visible, photoluminescence (PL), and dynamic light scattering (DLS) measurements. The porosity analysis via nitrogen sorption measurements at 77 K showed that the material is porous with hierarchical micro-, wide micro-, and mesopores. The SAED pattern confirms the polycrystallinity of the material, which is in good agreement with the data obtained from PXRD analysis. Effective integration of Mn-doped ZnO onto the MOF structure was confirmed by XPS analysis, and the study further identified the oxidation state of the elements present. The synthesized analyte is an efficient fluorescent chemosensor for the detection of acetic acid, which can find further potential applications in intracellular imaging. Interestingly, the same compound also selectively detects the presence of Cr(VI) ions, thereby acting as a dual sensor, which finds applications in the sensing and removal of environmental contaminants. The material showed a sharp and intense emission at 569 nm at an excitation wavelength of 320 nm, and it exhibits high quenching efficiencies of 99.87 and 71.43% toward the sensing of μM level concentration of acetic acid and Cr2O72-, respectively. The highly efficient fluorescent sensing of pollutants, even at a shorter linear range, discarded the possibility of sensing the pollutants at higher concentration ranges. The Ksv value for the detection of acetic acid and Cr(VI) is found to be 3.7017 × 106 and 11.0324 × 106 M-1, respectively, which further confirms the higher sensing ability of the synthesized fluorophore. The mechanistic studies and density functional theory calculations of Mn-doped ZnO@MOF-5 reveal that photoinduced electron transfer plays a significant role in the turn-off response toward acetic acid and Cr2O72- ions. In the case of acetic acid, in addition to photoinduced electron transfer, hydrogen bonding interactions may also lead to fluorescence quenching. To the best of our knowledge, no precedent work has been reported for the sensing of acetic acid in the solution state. All other fluorescent sensing reports put forward the sensing and adsorption of acetic acid in the gaseous state, which makes this material a pioneer among others for the detection of acetic acid in the solution phase.

Synthesis of hierarchically porous zirconium-based metal-organic framework@silica core-shell stationary phase through etching strategy for liquid chromatography

Metal organic frameworks (MOFs) show promise to be employed as stationary phase for high performance liquid chromatography (HPLC), however, the microporous structures of MOFs seriously restrict the diffusion and mass transfer of solute molecules, leading to a low column efficiency. In this paper, the fabrication of hierarchically porous UiO-66@SiO2 (HP- UiO-66@SiO2) core-shell microspheres via H2O2 etching has been proposed as a viable approach to enhance the separation performance of MOFs-based columns for HPLC. Through the direct treatment of the preliminary prepared UiO-66@SiO2 microspheres with H2O2 etching, HP-UiO-66@SiO2 core-shell microspheres were successfully synthesized with an enlarged pore size of up to 9 nm, facilitating efficient mass transfer in chromatographic separation. The prepared HP-UiO-66@SiO2 core-shell microspheres were then explored as stationary phase in HPLC to separate the nonpolar alkyl benzene homologues, the polar aromatic alcohol homologues and the xylene isomers. The results indicated that the baseline separations of these solutes were achieved successfully with narrow peak width and higher resolution than the UiO-66@SiO2 column. The HP-UiO-66@SiO2 column exhibited superior separation performance, reaching a maximum plate number of 134,459/m for fluorene, and showing good reproducibility. As a result, this template-free approach suggests that the fabrication of hierarchically porous MOFs@silica core-shell microspheres is a successful approach to enhance the column efficiency of MOFs-based columns in HPLC.

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.

Construction and application of carbon aerogels in microwave absorption

Electromagnetic pollution that threatens human health, the ecological environment and electronic equipment has been recognized as a serious environmental issue. In view of this, microwave absorbing materials (MAMs) are urgently required in modern society. Compared with traditional MAMs, carbon aerogels have inherent advantages in microwave absorption because of their high porosity and controllable conductive networks. Moreover, they are self-supporting 3D architectures with tailorable shapes, which satisfy most application scenarios. Therefore, carbon aerogels have aroused great interest in recent years and are being developed as promising absorption materials. In this review, we emphasize recent developments in carbon-aerogel-based MAMs constructed with some typical carbon nanomaterials, including graphene, carbon nanotubes and pyrolytic carbon. Their preparation methods, especially some newly developed strategies, are introduced as well as their influence on the structures and properties of aerogels. With a brief analysis of classic microwave absorption processes, we propose the requirements and strategies for modifying carbon aerogels to achieve ideal microwave absorption performance. Finally, we provide comprehensive comparisons of the MA performances of various carbon aerogels that show application potential and set forth the challenges and prospects of this kind of MAM.

Protein-directed synthesis of ZIF-8 functionalized with a polymer as core-shell drug coatings with antibacterial and anti-inflammatory properties

We developed a strategy to use lysozyme (Lys) as a template to produce mesoporous zeolitic imidazolate framework (ZIF-8) structures under physiological conditions. Thereafter, an amphiphilic triblock copolymer, PEG-PPG-PEG, was used to form protective core-shell ZIF-8 nanocomposite coatings to protect the encapsulated drug epigallocatechin-3-gallate (EGCG), to achieve notable antibacterial properties against E. coli, S. aureus and MRSA strains. Moreover, nanocomposites exhibited anti-inflammatory activity by counteracting the secretion of cytokines in THP-1 macrophages.

Metal-Organic Framework-Based Hierarchically Porous Materials: Synthesis and Applications

Metal-organic frameworks (MOFs) have been widely recognized as one of the most fascinating classes of materials from science and engineering perspectives, benefiting from their high porosity and well-defined and tailored structures and components at the atomic level. Although their intrinsic micropores endow size-selective capability and high surface area, etc., the narrow pores limit their applications toward diffusion-control and large-size species involved processes. In recent years, the construction of hierarchically porous MOFs (HP-MOFs), MOF-based hierarchically porous composites, and MOF-based hierarchically porous derivatives has captured widespread interest to extend the applications of conventional MOF-based materials. In this Review, the recent advances in the design, synthesis, and functional applications of MOF-based hierarchically porous materials are summarized. Their structural characters toward various applications, including catalysis, gas storage and separation, air filtration, sewage treatment, sensing and energy storage, have been demonstrated with typical reports. The comparison of HP-MOFs with traditional porous materials (e.g., zeolite, porous silica, carbons, metal oxides, and polymers), subsisting challenges, as well as future directions in this research field, are also indicated.

A hafnium-based metal-organic framework for the entrapment of molybdenum hexacarbonyl and the light-responsive release of the gasotransmitter carbon monoxide

A carbon monoxide-releasing material (CORMA) has been prepared by inclusion of molybdenum hexacarbonyl in a hafnium-based metal-organic framework (MOF) with the UiO-66 architecture. Mo(CO)₆ was adsorbed from solution to give supported materials containing 6.0-6.6 wt% Mo. As confirmed by powder X-ray diffraction (PXRD) and SEM coupled with energy dispersive X-ray spectroscopy, neither the crystallinity nor the morphology of the porous host was affected by the loading process. While the general shape of the N₂ physisorption isotherms (77 K) did not change significantly after encapsulation of Mo(CO)₆, the micropore volume decreased by ca. 20%. Thermogravimetric analysis of the as-prepared materials revealed a weight loss step around 160 °C associated with the decomposition of Mo(CO)₆ to subcarbonyl species. Confirmation for the presence of encapsulated Mo(CO)₆ complexes was provided by FT-IR and ¹³C{¹H} cross-polarization magic-angle spinning NMR spectroscopies. To test the capability of these materials to behave as CORMAs and transfer CO to heme proteins, the standard myoglobin (Mb) assay was used. While stable in the dark, photoactivation with low-power UV light (365 nm) liberated CO from the encapsulated hexacarbonyl molecules in Mo(6.0)/UiO-66(Hf), leading to a maximum amount of 0.26 mmol CO released per gram of material. Under the simulated physiological conditions of the Mb assay (37 °C, pH 7.4 buffer), minimal leaching of molybdenum occurred, PXRD showed only slight amorphization, and FT-IR spectroscopy confirmed the high chemical stability of the MOF host.

Defective Hierarchical Pore Engineering of a Zn-Ni MOF by Labile Coordination Bonding Modulation

The construction and modulation of hierarchical pore structure in metal-organic frameworks (MOFs) has become a hot topic owing to the advantages of hierarchical pore MOFs (HP-MOFs) in matter storage and mass transfer related applications. Herein, we report the engineering of crystalline defect in a bimetallic MOF for the construction and tuning of HP-MOF. A microporous MOF system showing metal-center-dependent water stability, namely, {[M₃F(bdc)₃ tpt] (solvents)}_n (M = Zn²⁺ and Ni²⁺, H₂bdc = 1,4-benzenedicarboxylic acid, tpt = 2,4,6-tris(4-pyridyl)triazine), was utilized as a platform for the construction of HP-MOF. By tuning the Zn²⁺/Ni²⁺ ratio in the reactant, a bimetallic MOF with a highly tunable Zn²⁺/Ni²⁺ ratio could be obtained. The relatively labile Zn²⁺-based coordination bonding in the bimetallic MOF could be readily and targeted broken through water treatment for the engineering of crystalline defects-based hierarchical pore structure. The resultant HP-MOF reveals a dramatically increased pore volume with the presence of mesopore and macropore. In addition, the anionic framework of HP-MOF could be utilized for the selective adsorption of a cationic dye methylene blue, and a relatively high capacity (250 mg·g^-1, five times compared with the pristine microporous MOF) could be achieved.

Catalytic Performance of CPM-200-In/Mg in the Cycloaddition of CO2 and Epoxides

Crystalline porous materials (CPM)-200-In and CPM-200-In/Mg metal-organic frameworks (MOFs) were synthesized by a solvothermal method and were characterized by using powder X-ray diffraction (PXRD), FT-IR, Brunauer–Emmett–Teller (BET), temperature programmed desorption (TPD), TGA, XPS, and SEM-EDS. They were used as heterogeneous catalysts for the cycloaddition of CO2 with epoxides and found to be highly efficient toward the cycloaddition reaction at moderate reaction conditions under solvent-free conditions. The catalyst was easily separated by a simple filtration and can be reused up to five consecutive times without any considerable decrease of its initial activity. CPM-200-In/Mg showed excellent catalytic performance in the cycloaddition reaction due to the synergistic role of the acidic sites and basic sites. A plausible reaction mechanism for the CPM-200-In/Mg MOF catalyzed cycloaddition reaction is proposed based on the experimental results and our previously reported DFT (Density Functional Theory) studies.

Modulating the stacking modes of nanosized metal-organic frameworks by morphology engineering for isomer separation

Modulating different stacking modes of nanoscale metal-organic frameworks (MOFs) introduces different properties and functionalities but remains a great challenge. Here, we describe a morphology engineering method to modulate the stacking modes of nanoscale NU-901. The nanoscale NU-901 is stacked through solvent removal after one-pot solvothermal synthesis, in which different morphologies from nanosheets (NS) to interpenetrated nanosheets (I-NS) and nanoparticles (NP) were obtained successfully. The stacked NU-901-NS, NU-901-I-NS, and NU-901-NP exhibited relatively aligned stacking, random stacking, and close packing, respectively. The three stacked nanoscale NU-901 exhibited different separation abilities and all showed better performance than bulk phase NU-901. Our work provides a new morphology engineering route for the modulation of the stacking modes of nano-sized MOFs and improves the separation abilities of MOFs.

Hierarchically porous metal-organic frameworks: synthesis strategies, structure(s), and emerging applications in decontamination

Metal-organic frameworks (MOFs) with high porosity have received much attention as promising materials for many applications owing to their unique properties. However, to date, most of the reported MOFs have microporous structures, which slow down diffusion/mass transfer and limit the accessibility of bulky molecules to its internal surface. Thus, it is crucial to develop an efficient way to create larger pores (mesoporous and/or macroporous) into microporous MOFs to form hierarchical porous metal-organic frameworks (HP-MOFs), which facilitate the diffusion and mass transfer of guest molecules. HP-MOFs are excellent and promising candidates for environmental applications under the background of environmental contaminations. In this review paper, we are primarily focusing on the latest progress in the preparation of HP-MOFs by employing template-assisted and template-free synthetic approaches for environmental cleaning applications. Particularly, the adsorptive purification of the most common toxic substances, including gases, dyes, heavy metal ions, and antibiotics from the environment using HP-MOFs as adsorbents is briefly discussed. The overall results clearly showed that the superiority of HP-MOFs compared with conventional microporous MOFs. Finally, we summarize the remaining challenges and provide personal perspectives on possible future development of HP-MOFs.

Rapid Room-Temperature Preparation of Hierarchically Porous Metal-Organic Frameworks for Efficient Uranium Removal from Aqueous Solutions

The effective removal of uranium from an aqueous solution is a highly valuable process for the environment and health. In this study, we developed a facile and rapid method to synthesize hierarchically porous Cu-BTC (RT-Cu-BTC) using a cooperative template strategy. The as-synthesized RT-Cu-BTC exhibited hierarchically porous structure and excellent thermostability, as revealed by X-ray powder diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. Compared with conventional metal-organic frameworks (MOFs) and zeolites, the obtained RT-Cu-BTC exhibited enhanced adsorption capacity (839.7 mg·g-1) and high removal efficiency (99.8%) in the capture of uranium (VI) from aqueous solutions. Furthermore, the conditions such as adsorbent dose, contact time, and temperature in adsorption of uranium (VI) by RT-Cu-BTC were investigated in detail. The thermodynamics data demonstrated the spontaneous and endothermic nature of the uranium (VI) adsorption process. The Langmuir isotherm and pseudo-second-order models could better reflect the adsorption process of uranium (VI) onto RT-Cu-BTC. In addition, the as-synthesized RT-Cu-BTC showed excellent stability in removing uranium (VI) from an aqueous solution. This work provides a facile and rapid approach for fabricating hierarchically porous MOFs to realize a highly efficient removal of uranium (VI) from aqueous systems.

Synthesis of ordered microporous/macroporous MOF-808 through modulator-induced defect-formation, and surfactant self-assembly strategies

Ordered materials with interconnected porosity allow the diffusion of molecules within their inner porous structure to access the active sites located in the microporous core. As a follow-up of our work on engineering of MOF-808, in this contribution, we study the synthesis of defective MOF-808 using two different strategies: the use of modulators and the surfactant-assisted synthesis to obtain materials with ordered and interconnected pores. The results of the study indicated that (i) the use of modulators of different chain length led to the formation of microporous/mesoporous MOFs through the formation of missing linker defects. However, the use of the acetic acid contributes to the formation of MOFs with larger mesoporous size distributions compared to materials synthesized with formic and propionic acids as modulators, and (ii) the self-assembly of CTAB surfactant produced an ordered microporous/macroporous network which enhanced crystallinity. However, the surface properties of the materials seem to be unaffected by the use of surfactants during synthesis. These results contribute to the development of ordered materials with a broad range of pore size distributions and give rise to new opportunities to extend the applications of MOF-808.

Coupling Structural and Adsorption Properties of Metal-Organic Frameworks: From Pore Size Distribution to Pore Type Distribution

Metal-organic frameworks (MOFs) attract a rapidly growing attention across the disciplines due to their multifarious pore structures and unique ability to selectively adsorb, store, and release various guest molecules. Pore structure characterization and coupling of adsorption and structural properties are imperative for rational design of advanced MOF materials and their applications. The pore structure of MOFs represents a three-dimensional network comprised of several types of pore compartments: interconnected cages and channels distinguished by their size, shape, and chemistry. Here, we propose a novel methodology for pore structure characterization of MOF materials based on matching of the experimental adsorption isotherms to in silico-generated fingerprint isotherms of adsorption in individual pore compartments of the ideal crystal. The proposed approach couples structural and adsorption properties, determines the contributions of different types of pores into the total adsorption, and estimates to what extent the pore structure of the sample under investigation is different from the ideal crystal. The MOF pore structure is characterized by the pore type distribution (PTD), which is more informative than the traditional pore size distribution that is based on oversimplistic pore models. The method is illustrated on the example of Ar adsorption at 87 K on hydrated and dehydrated structures of Cu-BTC, one of the most well-known MOF materials. The PTD determined from the experimental isotherm provides an estimate of the crystal fraction in the sample and the accessibility and degree of hydration of different types of pore compartments. In addition, the PTD determined from the experimental adsorption isotherm is used to predict the isosteric heat of adsorption that provides important information on the specifics of adsorption interactions. The results are found to be in excellent agreement with experimental data. Such detailed information about the pore structure and adsorption properties of practical MOF samples cannot be obtained with currently available methods of adsorption characterization.

Ultrafast room-temperature synthesis of hierarchically porous metal–organic frameworks with high space–time yields

We developed a facile and general approach to rapidly synthesize four hierarchically porous MOFs (HKUST-1, ZIF-8, ZIF-61, and ZIF-90) under ambient conditions.

Defective hierarchical porous copper-based metal-organic frameworks synthesised via facile acid etching strategy

Introducing hierarchical pore structure to microporous materials such as metal-organic frameworks (MOFs) can be beneficial for reactions where the rate of reaction is limited by low rates of diffusion or high pressure drop. This advantageous pore structure can be obtained by defect formation, mostly via post-synthetic acid etching, which has been studied extensively on water-stable MOFs. Here we show that a water-unstable HKUST-1 MOF can also be modified in a corresponding manner by using phosphoric acid as a size-selective etching agent and a mixture of dimethyl sulfoxide and methanol as a dilute solvent. Interestingly, we demonstrate that the etching process which is time- and acidity- dependent, can result in formation of defective HKUST-1 with extra interconnected hexagonal macropores without compromising on the bulk crystallinity. These findings suggest an intelligent scalable synthetic method for formation of hierarchical porosity in MOFs that are prone to hydrolysis, for improved molecular accessibility and diffusion for catalysis.

Rising Up: Hierarchical Metal-Organic Frameworks in Experiments and Simulations

Controlled synthesis across several length scales, ranging from discrete molecular building blocks to size- and morphology-controlled nanoparticles to 2D sheets and thin films and finally to 3D architectures, is an advanced and highly active research field within both the metal-organic framework (MOF) domain and the overall material science community. Along with synthetic progress, theoretical simulations of MOF structures and properties have shown tremendous progress in both accuracy and system size. Further advancements in the field of hierarchically structured MOF materials will allow the optimization of their performance; however, this optimization requires a deep understanding of the different synthesis and processing techniques and an enhanced implementation of material modeling. Such modeling approaches will allow us to select and synthesize the highest-performing structures in a targeted rational manner. Here, recent progress in the synthesis of hierarchically structured MOFs and multiscale modeling and associated simulation techniques is presented, along with a brief overview of the challenges and future perspectives associated with a simulation-based approach toward the development of advanced hierarchically structured MOF materials.

Templated fabrication of hierarchically porous metal-organic frameworks and simulation of crystal growth

Hierarchically porous metal-organic frameworks (MOFs) have recently emerged as a novel crystalline hybrid material with tunable porosity. Many efforts have been made to develop hierarchically porous MOFs, yet their low-energy fabrication remains a challenge and the underlying mechanism is still unknown. In this study, the rapid fabrication of two hierarchically porous MOFs (Cu-BTC and ZIF-8) was carried out at room temperature and ambient pressure for 10 min using a novel surfactant as the template in a (Cu, Zn) hydroxy double salt (HDS) solution, where the (Cu, Zn) HDS accelerated the nucleation of crystals and the anionic surfactants served as templates to fabricate mesopores and macropores. The growth mechanism of hierarchically porous MOFs was analyzed via mesodynamics (MesoDyn) simulation, and then the synthetic mechanism of hierarchically porous MOFs at the molecular level was obtained. The as-synthesized hierarchically porous Cu-BTC showed a high uptake capacity of 646 mg g^-1, which is about 25% higher as compared with microporous Cu-BTC (516 mg g^-1) for the capture of toluene. This study provides a theoretical basis for the large-scale fabrication of hierarchically porous MOFs and offers a reference for the understanding of their synthetic mechanism.

A novel ammonium pentaborate – poly(ethylene-glycol) templated polymer-inclusion compound

Reaction of ammonia borane with poly-ethylene glycol at slightly elevated temperatures leads to the formation of the first known example of a borate-based polymer inclusion compound with a pentaborate framework structure.

Hierarchically porous metal-organic frameworks: rapid synthesis and enhanced gas storage

Large pore sizes, high pore volumes, facile synthesis conditions, and high space-time yields are recognized as four crucial criteria in the fabrication of metal-organic frameworks (MOFs). However, these four objectives are rarely realized together. Herein, we have developed a simple and versatile method that employs 1,4-butanediamine (BTDM) as a template for rapidly fabricating four stable hierarchically porous MOFs (H-MOFs), including HKUST-1, ZIF-8, ZIF-67, and ZIF-90. The synthesis conditions are simple and facile at room temperature and ambient pressure, and the synthesis time can be shortened to 1 min. The resultant H-MOFs exhibit multimodal hierarchically porous structures with meso- and macropores interconnected with micropores, as well as high pore volumes (0.76 cm3 g-1). The maximum space-time yield for the hierarchically porous HKUST-1 reaches 7.4 × 104 kg m-3 d-1, at least one order of magnitude higher than previous reported yields. Notably, the additive BTDM not only facilitates crystal growth but also guides the formation of meso- and macropores. The synthesis route is highly versatile, as analogues (e.g., tetramethyl-1,3-diaminopropane and tetramethyldiaminomethane) can also be employed as templates to prepare diverse H-MOFs. Furthermore, the porosities of the H-MOFs are readily tuned by controlling the metal source, template amount and type of template. The as-synthesized H-MOFs act as adsorbents with significantly improved performances relative to those of microporous MOFs used for CH4 and CO2 gas storage. This strategy may aid in the large-scale industrial synthesis of desirable H-MOFs for gas storage.

Selective Adsorption of Ethane over Ethylene in PCN-245: Impacts of Interpenetrated Adsorbent

The separation of ethane from ethylene using cryogenic distillation is an energy-intensive process in the industry. With lower energetic consumption, the adsorption technology provides the opportunities for developing the industry with economic sustainability. We report an iron-based metal-organic framework PCN-245 with interpenetrated structures as an ethane-selective adsorbent for ethylene/ethane separation. The material maintains stability up to 625 K, even after exposure to 80% humid atmosphere for 20 days. Adsorptive separation experiments on PCN-245 at 100 kPa and 298 K indicated that ethane and ethylene uptakes of PCN-245 were 3.27 and 2.39 mmol, respectively, and the selectivity of ethane over ethylene was up to 1.9. Metropolis Monte Carlo calculations suggested that the interpenetrated structure of PCN-245 created greater interaction affinity for ethane than ethylene through the crossing organic linkers, which is consistent with the experimental results. This work highlights the potential application of adsorbents with the interpenetrated structure for ethane separation from ethylene.

Hierarchically porous metal–organic frameworks with single-crystal structures and their enhanced catalytic properties

Stable hierarchically porous metal–organic frameworks (HP-MOFs) have been successfully synthesized under hydrothermal conditions using a template strategy.

Hierarchically structured metal–organic frameworks assembled by hydroxy double salt–template synergy with high space–time yields

A simple, green, and versatile method to rapidly synthesize hierarchically structured metal–organic frameworks at room temperature using a cooperative template strategy.