1D-2D-3D Transformation Synthesis of Hierarchical Metal–Organic Framework Adsorbent for Multicomponent Alkane Separation

2D Materials Nanoarchitectonics for 3D Structures/Functions

It has become clear that superior material functions are derived from precisely controlled nanostructures. This has been greatly accelerated by the development of nanotechnology. The next step is to assemble materials with knowledge of their nano-level structures. This task is assigned to the post-nanotechnology concept of nanoarchitectonics. However, nanoarchitectonics, which creates intricate three-dimensional functional structures, is not always easy. Two-dimensional nanoarchitectonics based on reactions and arrangements at the surface may be an easier target to tackle. A better methodology would be to define a two-dimensional structure and then develop it into a three-dimensional structure and function. According to these backgrounds, this review paper is organized as follows. The introduction is followed by a summary of the three issues; (i) 2D to 3D dynamic structure control: liquid crystal commanded by the surface, (ii) 2D to 3D rational construction: a metal-organic framework (MOF) and a covalent organic framework (COF); (iii) 2D to 3D functional amplification: cells regulated by the surface. In addition, this review summarizes the important aspects of the ultimate three-dimensional nanoarchitectonics as a perspective. The goal of this paper is to establish an integrated concept of functional material creation by reconsidering various reported cases from the viewpoint of nanoarchitectonics, where nanoarchitectonics can be regarded as a method for everything in materials science.

Potential of nonporous adaptive crystals for hydrocarbon separation

Hydrocarbon separation is an important process in the field of petrochemical industry, which provides a variety of raw materials for industrial production and a strong support for the development of national economy. However, traditional separation processes involve huge energy consumption. Adsorptive separation based on nonporous adaptive crystal (NAC) materials is considered as an attractive green alternative to traditional energy-intensive separation technologies due to its advantages of low energy consumption, high chemical and thermal stability, excellent selective adsorption and separation performance, and outstanding recyclability. Considering the exceptional potential of NAC materials for hydrocarbon separation, this review comprehensively summarizes recent advances in various supramolecular host-based NACs. Moreover, the current challenges and future directions are illustrated in detail. It is expected that this review will provide useful and timely references for researchers in this area. Based on a large number of state-of-the-art studies, the review will definitely advance the development of NAC materials for hydrocarbon separation and stimulate more interesting studies in related fields.

Performance of Rod-Shaped Ce Metal-Organic Frameworks for Defluoridation

The performance of a Ce(III)-4,4',4″-((1,3,5-triazine-2,4,6-triyl) tris (azanediyl)) tribenzoic acid-organic framework (Ce-H3TATAB-MOFs) for capturing excess fluoride in aqueous solutions and its subsequent defluoridation was investigated in depth. The optimal sorption capacity was obtained with a metal/organic ligand molar ratio of 1:1. The morphological characteristics, crystalline shape, functional groups, and pore structure of the material were analyzed via SEM, XRD, FTIR, XPS, and N₂ adsorption-desorption experiments, and the thermodynamics, kinetics, and adsorption mechanism were elucidated. The influence of pH and co-existing ions for defluoridation performance were also sought. The results show that Ce-H3TATAB-MOFs is a mesoporous material with good crystallinity, and that quasi-second kinetic and Langmuir models can describe the sorption kinetics and thermodynamics well, demonstrating that the entire sorption process is a monolayer-governed chemisorption. The Langmuir maximum sorption capacity was 129.7 mg g^-1 at 318 K (pH = 4). The adsorption mechanism involves ligand exchange, electrostatic interaction, and surface complexation. The best removal effect was reached at pH 4, and a removal effectiveness of 76.57% was obtained under strongly alkaline conditions (pH 10), indicating that the adsorbent has a wide range of applications. Ionic interference experiments showed that the presence of PO₄^3- and H₂PO₄^- in water have an inhibitory effect on defluoridation, whereas SO₄^2-, Cl^-, CO₃^2-, and NO₃^- are conducive to the adsorption of fluoride due to the ionic effect.

Metal-Organic Frameworks for Greenhouse Gas Applications

Using petrol to supply energy for a car or burning coal to heat a building generates plenty of greenhouse gas (GHG) emissions, including carbon dioxide (CO₂ ), water vapor (H₂ O), methane (CH₄ ), nitrous oxide (N₂ O), ozone (O₃ ), fluorinated gases. These up-and-coming metal-organic frameworks (MOFs) are structurally endowed with rigid inorganic nodes and versatile organic linkers, which have been extensively used in the GHG-related applications to improve the lives and protect the environment. Porous MOF materials and their derivatives have been demonstrated to be competitive and promising candidates for GHG separation, storage and conversions as they shows facile preparation, large porosity, adjustable nanostructure, abundant topology, and tunable physicochemical property. Enormous progress has been made in GHG storage and separation intrinsically stemmed from the different interaction between guest molecule and host framework from MOF itself in the recent five years. Meanwhile, the use of porous MOF materials to transform GHG and the influence of external conditions on the adsorption performance of MOFs for GHG are also enclosed. In this review, it is also highlighted that the existing challenges and future directions are discussed and envisioned in the rational design, facile synthesis and comprehensive utilization of MOFs and their derivatives for practical applications.

Synthesis of Carborane-Backbone Metallacycles for Highly Selective Capture of n-Pentane

The specific recognition and separation of alkanes with similar molecular structures and close boiling points face significant scientific challenges and industrial demands. Here, rectangular carborane-based metallacycles were designed to selectively encapsulate n-pentane from n-pentane, iso-pentane, and cyclo-pentane mixtures in a simple-to-operate and more energy-efficient way. Metallacycle 1, bearing 1,2-di(4-pyridyl) ethylene, can selectively separate n-pentane from these three-component mixtures with a purity of 97%. The selectivity is ascribed to the capture of the preferred guest with matching size, C-H···π interactions, and potential B-H^δ-···H^δ+-C interactions. Besides, the removal of n-pentane gives rise to original guest-free carborane-based metallacycles, which can be recycled without losing performance. Considering the variety of substituted carborane derivatives, metal ions, and organic linkers, these new carborane-based supramolecular coordination complexes (SCCs) may be broadly applicable to other challenging recognition and separation systems with good performance.

Simultaneous Recognition and Separation of Organic Isomers Via Cooperative Control of Pore-Inside and Pore-Outside Interactions

Despite the desirability of organic isomer recognition and separation, current strategies are expensive and complicated. Here, a simple strategy for simultaneously recognizing and separating organic isomers using pillararene-based charge-transfer cocrystals through the cooperative control of pore-inside and pore-outside intermolecular interactions is presented. This strategy is illustrated using 1-bromobutane (1-BBU), which is often produced as an isomeric mixture with 2-bromobutane (2-BBU). According to its structure, perethylated pillar[5]arene (EtP5) and 3,5-dinitrobenzonitrile (DNB) are strategically chosen as a donor and an acceptor. As a result, their cocrystal exhibited stronger pore-inside interactions and much weaker pore-outside interactions with 1-BBU than with 2-BBU. Consequently, nearly 100% 1-BBU selectivity is achieved in two-component mixtures, even in those containing trace 1-BBU (1%), whereas free EtP5 only achieved 89.80% selectivity. The preference for linear bromoalkanes is retained in 1-bromopentane/3-bromopentane and 1-bromohexane/2-bromohexane mixtures, demonstrating the generality of this strategy. Selective adsorption of linear bromoalkanes induced a naked-eye-detectable color change from red to white. Moreover, the cocrystal are used over multiple cycles without losing selectivity.

A well-defined hierarchically porous metal-organic framework and its application in separation and purification of steviol glycosides

The separation and removal of stevioside from natural product steviol glycosides to obtain high-purity rebaudioside A is of great significance for the application of steviol glycosides in food, medicine and other fields. Here, in order to explore the adsorbent pore structure suitable for the separation of stevioside and rebaudioside A, a hierarchically porous amino-functionalized metal-organic framework (HP-NH₂ -MIL-53) with an appropriate and narrow pore size distribution was prepared using a modulator induced defect-formation strategy. The results showed that the hierarchically porous structure with micropores and mesopores increased the specific surface area and exposed amino groups compared with original metal organic framework (NH₂ -MIL-53), and the maximum adsorption capacity of HP-NH₂ -MIL-53 for stevioside and rebaudioside A was 233.89 mg/g. The narrow pore size distribution close to 3.80 nm promoted the screening effect, resulting in a maximum adsorption selectivity of 4.13. This work proves that when the pore size of the adsorbent is between 1.41-3.80 nm, it has a certain pore size screening effect on stevioside and rebaudioside A, and the hierarchically porous metal-organic frameworks provide a pre-design idea of adsorbent structure for the separation of natural products with molecular weight of 800-1000 Da. This article is protected by copyright. All rights reserved.

Hierarchical COK-X Materials for Applications in Catalysis and Adsorptive Separation and Controlled Release

Over the years, COK has developed a family of silicate materials and metal–organic framework hybrids with hierarchical porosity and functionality, coined zeogrids, zeotiles, and COK-x (stemming from the Flemish name of the laboratory “Centrum voor Oppervlaktechemie en Katalyse”). Several of these materials have unique features relevant to heterogeneous catalysis, molecular separation, and controlled release and found applications in the field of green chemistry, environmental protection, and pharmaceutical formulation. Discovery of a new material typically occurs by serendipity, but the research was always guided by hypothesis. This review provides insight in the process of tuning initial research hypotheses to match material properties to specific applications. This review describes the synthesis, structure, properties, and applications of 12 different materials. Some have simple synthesis protocols, facilitating upscaling and reproduction and rendering them attractive also in this respect.

Spray drying-assisted construction of hierarchically porous ZIF-8 for controlled release of doxorubicin

The intrinsic properties and structure of carrier materials, as well as the drug-loading method, are crucial to the fabrication of high-performance controlled drug release systems. Metal-organic frameworks (MOFs) have attracted great attention in drug delivery due to their rich variety and very precisely designable structures, but their inherent small pores limit their application towards large-size drug molecules. Herein, we report a facile and efficient approach for the construction of hierarchically porous ZIF-8 (HP-ZIF-8) by spray drying. The homogeneously distributed mesopores, which result from the interspaces in the closely arranged nanosized ZIF-8 (N-ZIF-8), can be tuned by adjusting the primary particle size. More importantly, a drug (doxorubicin (DOX), for example) can be simultaneously encapsulated during the fabrication process of HP-ZIF-8, achieving a high loading rate of 79% and an encapsulation efficiency of 79%. Furthermore, we demonstrate that the obtained DOX@HP-ZIF-8 is a pH-responsive system and the release can also be controlled by the mesopore size. Although HP-ZIF-8 shows obvious advantages in drug loading and release performance compared with N-ZIF-8 loaded with DOX by the same solvent adsorption approach, DOX@HP-ZIF-8 displays significantly increased loading capacity (more than 3 times) and the slowest release rate due to its drug-loading method. Their therapeutic efficacy on HeLa cells has also been proved. These findings have important implications for the construction of HP-MOFs as drug carriers and will also present a new platform for controlled drug release and biomedical applications.

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.

Adsorptive removal of aflatoxin B1 from vegetable oils via novel adsorbents derived from a metal-organic framework

Vegetable oils are essential daily diet, but they are simply contaminated with aflatoxin B₁ (AFB₁), a serious toxic compound to human health. Adsorption method due to the easy operation, high efficiency and low costing is set to become a main detoxification technique for AFB₁. Unfortunately, previous reported adsorbents were rarely used for detoxification in food industry since they cannot meet the criteria of large-scale production of edible oils. Metal-organic frameworks (MOFs) with unique textural properties could be favorable precursors for synthesis of advanced materials. In this research, three kinds of Cu-BTC MOF-derived porous materials were prepared by different carbonization temperature and characterized by XRD, SEM, FT-IR, and nitrogen adsorption-desorption techniques. Isotherm and kinetic studies on the adsorption behaviour of AFB₁ onto the three porous carbonaceous materials have been systematically conducted. The results revealed that the porous carbonaceous materials could act as the excellent adsorbents that were of enough adsorption sites for AFB₁, mainly due to the hierarchical porous structure and large surface areas for the enhancement of adsorption capacity. Notably, the porous carbonaceous materials could not only remove more than 90% of AFB₁ from real vegetable oils within 30 min, but also remain the treated oils at low cytotoxicity. Meanwhile, the detoxification process could little affect the quality of oils. Thus, the Cu-BTC MOF-derived porous carbonaceous materials with high efficiency, safe, practical and economic characteristics could be novel potential adsorbents used in the application of AFB₁ removal from contaminated vegetable oils.

Calcination activation of three-dimensional cobalt organic phosphate nanoflake assemblies for supercapacitors

Three-dimensional organic phosphate nanoflake assemblies were obtained by calcination activation. In the two-electrode system, 3D COP assemblies showed excellent cycle stability, and the capacity retention was 99.61% after 3000 long cycles.

Recent advances in the adsorptive remediation of wastewater using two-dimensional transition metal carbides (MXenes): a review

MXenes, since their discovery in 2011, have garnered significant research attention for a variety of applications due to their exciting physico-chemical properties.

Selective guest inclusion of linear C6 hydrocarbons in a Zn(ii) 1D coordination polymer

Trapping of volatile unbranched C₆ hydrocarbons (hexane, 1-hexene, and 1-hexyne) in a 1D coordination polymer is reported.

Structural elucidation of microcrystalline MOFs from powder X-ray diffraction

Ab initio powder XRD structure solution and MOFs.

Metal-Organic Framework Materials for the Separation and Purification of Light Hydrocarbons

The separation and purification of light hydrocarbons (LHs) mixtures is one of the most significantly important but energy demanding processes in the petrochemical industry. As an alternative technology to energy intensive traditional separation methods, such as distillation, absorption, extraction, etc., adsorptive separation using selective solid adsorbents could potentially not only lower energy cost but also offer higher efficiency. The need to develop solid materials for the efficiently selective adsorption of LHs molecules, under mild conditions, is therefore of paramount importance and urgency. Metal-organic frameworks (MOFs), emerging as a relatively new class of porous organic-inorganic hybrid materials, have shown promise for addressing this challenging task due to their unparalleled features. Herein, recent advances of using MOFs as separating agents for the separation and purification of LHs, including the purification of CH₄ , and the separations of alkynes/alkenes, alkanes/alkenes, C₅ -C₆ -C₇ normal/isoalkanes, and C₈ alkylaromatics, are summarized. The relationships among the structural and compositional features of the newly synthesized MOF materials and their separation properties and mechanisms are highlighted. Finally, the existing challenges and possible research directions related to the further exploration of porous MOFs in this very active field are also discussed.

Microporous Metal-Organic Frameworks for Adsorptive Separation of C5-C6 Alkane Isomers

The separation of alkane isomers, particularly C5-C6 alkanes, is of paramount importance in the petrochemical industry to achieve high quality gasoline. Upon catalytic isomerization reactions, less branched alkanes (with lower octane number) need to be separated from their more branched isomers (with higher octane number) in order to improve the octane rating of gasoline. To reduce the high energy input associated with distillations, the primary separation technique currently used in industry, adsorptive separation by porous solids has been proposed. For example, zeolite 5A has been used as the adsorbent material for adsorptive separation of linear alkanes from their branched isomers, as a supplement technology to distillations. However, due to the limited number of zeolite structures and the lack of porosity tenability in these compounds, the task has not been fully fulfilled by using zeolites. Metal-organic frameworks (MOFs), in light of their structural diversity and high tunability in terms of surface area, pore size, and pore shape, offer new opportunities for resolving industrially relevant separation of alkanes through selective adsorption. This Account summarizes recent development of microporous MOFs for the separation of alkanes, with an emphasis on C5-C6 alkane isomers, including early examples of alkane separation by MOFs, as well as the latest advancement on tailor-made microporous MOFs for size sieving of C5-C6 alkane isomers. The limitation of zeolite 5A as a sorbent material for the separation of C5-C6 alkane isomers lies in its relatively low adsorption capacity. In addition, it is not capable of separating branched alkanes, which is a crucial step for further improving the octane rating of gasoline. The high porosity and tunable pore size and pore shape of MOFs may afford them higher adsorption capacity and selectivity when used for alkane separation. MOFs with pore size slightly larger than the kinetic diameter of branched alkanes can effectively separate alkane isomers through thermodynamically controlled separation, as seen in the case of Fe₂(bdp)₃ (bdp^2- = 1,4-benzenedipyrazolate). This MOF is capable of separating a mixture of hexane isomers by the degrees of branching, with higher adsorption capacity than zeolites under similar conditions but with relatively low selectivity. One effective strategy for obtaining MOFs with optimal pore size and pore shape for highly selective adsorption is to make use of reticular chemistry and precise ligand design. By applying topologically directed design strategy and precisely controlling the pore structure or ligand functionality, we have successfully synthesized a series of highly robust MOFs built on tetratopic carboxylate linkers that demonstrate high performance for the separation of C5-C6 alkane isomers. Zr-bptc (bptc^4-= 3,3',5,5'-biphenyltetracarboxylate) adsorbs linear alkanes only and excludes all branched isomers. This size-exclusion mechanism is very similar to that of zeolite 5A. Yet, Zr-bptc has a significantly enhanced adsorption capacity for n-hexane, 70% higher than that of zeolite 5A under identical conditions. Zr-abtc (abtc^4- = 3,3',5,5'-azobenzenetetracarboxylate) is capable of discriminating all three C6 alkane isomers via a thermodynamically controlled process, yielding a high separation factor for monobranched over dibranched isomers. MOFs with flexible framework may exhibit unexpected but desired adsorption properties. Ca(H₂tcpb) (tcpb^4- = 1,2,4,5-tetrakis(4-carboxyphenyl)-benzene) can fully separate binary or ternary mixtures of C5-C6 alkane isomers into pure form through selective molecular sieving as a result of its temperature- and adsorbate-dependent framework flexibility. The intriguing structural properties and exceptional tunability of these MOFs make them promising candidates for industrial implementation of adsorptive separation of alkane isomers.

Untwisted restacking of two-dimensional metal-organic framework nanosheets for highly selective isomer separations

The stacking between nanosheets is an intriguing and inevitable phenomenon in the chemistry of nano-interfaces. Two-dimensional metal-organic framework nanosheets are an emerging type of nanosheets with ultrathin and porous features, which have high potential in separation applications. Here, the stacking between single-layer metal-organic framework nanosheets is revealed to show three representative conformations with tilted angles of 8°, 14°, and 30° for Zr-1, 3, 5-(4-carboxylphenyl)-benzene framework as an example. Efficient untwisted stacking strategy by simple heating is proposed. A detailed structural analysis of stacking modes reveals the creation of highly ordered sub-nanometer micropores in the interspacing of untwisted nano-layers, yielding a high-resolution separator for the pair of para-/meta-isomers over the twisted counterparts and commercial HP-5MS and VF-WAXMS columns. This general method is proven by additional nanosheet examples and supported by Grand Canonical Monte Carlo simulation. This finding will provide a synthetic route in the rational design of functionalities in two-dimensional metal-organic framework nanosheet.

Metal-organic framework nanosheets are promising for separations, but interactions among them, affecting the performance, are largely unexplored. The authors reveal the favored stacking modes in a model system, and that untwisted restacking by thermal treatment improves isomer separation performance in gas chromatography capillary columns.

Adsorption/desorption kinetics and breakthrough of gaseous toluene for modified microporous-mesoporous UiO-66 metal organic framework

In this work, micro-mesoporous UiO-66 was successfully prepared with P123 (EO₂₀PO₇₀EO₂₀) as structure-directing agent by a simple solvothermal method. Adsorption/desorption kinetics of gaseous toluene over pristine UiO-66 and micro-mesoporous UiO-66 were investigated by breakthrough experiments, toluene vapor adsorption isotherm measurements and temperature programmed desorption (TPD) experiments. The interactions between toluene and UiO-66 samples were assessed through the Henry's law constant (K_H) and the isosteric adsorption heat (ΔH_ads). The micro-mesoporous UiO-66 crystal demonstrated 2.6 times toluene adsorption capacity of the pristine UiO-66 when the P123/Zr⁴⁺ molar ratio was 0.2. Results showed that micropore adsorption was the main adsorption process and the larger pores in micro-mesoporous UiO-66 increased molecular diffusion rate and reduced the mass transfer resistance. This result indicated that micro-mesoporous structures and defect sites had a positive effect on toluene molecules capture. The breakthrough times and the working capacities decreased with the increase of the relative humidity and adsorption temperature. A good thermal stability and reproducibility were revealed over the micro-mesoporous UiO-66 in this paper.

Flexible all-solid-state supercapacitors of polyaniline nanowire arrays deposited on electrospun carbon nanofibers decorated with MOFs

Porous carbons derived from metal-organic frameworks (MOFs) are promising materials for a number of energy- and environment-related applications. To integrate the powder MOFs-derived carbon into feasible engineered materials, a facile strategy to fabricate integrated flexible film is developed by growing MOFs nanoparticles on polyimide electrospun nanofibers, followed by calcination, to fabricate freestanding carbon nanofiber membranes decorated with porous carbon. Then vertically polyaniline nanowire arrays are uniformly deposited on the hierarchical porous carbon substrates by in situ polymerization. Thanks to the good distribution of MOFs-derived porous carbon on carbon nanofibers and the compact configuration interwoven by conducting polymers, the designed hybrid electrode could be used directly as a freestanding electrode for supercapacitors, which displayed a high specific capacitance of 1268 F g^-1. The assembled flexible solid-state supercapacitor based on the integrated electrodes demonstrated a high volumetric capacitance of 1973 mF cm^-3 and a good capacitance retention of 84.9% after 10 000 cycles, which could power a commercial light emitting diode. This strategy may shed light on the design of MOFs-based flexible materials for practical applications of supercapacitors and other electrochemical devices.

Mesoporous Metal-Organic Frameworks: Synthetic Strategies and Emerging Applications

Metal-organic frameworks (MOFs) have attracted much attention over the past two decades due to their highly promising applications not only in the fields of gas storage, separation, catalysis, drug delivery, and sensors, but also in relatively new fields such as electric, magnetic, and optical materials resulting from their extremely high surface areas, open channels and large pore cavities compared with traditional porous materials like carbon and inorganic zeolites. Particularly, MOFs involving pores within the mesoscopic scale possess unique textural properties, leading to a series of research in the design and applications of mesoporous MOFs. Unlike previous Reviews, apart from focusing on recent advances in the synthetic routes, unique characteristics and applications of mesoporous MOFs, this Review also mentions the derivatives, composites, and hierarchical MOF-based systems that contain mesoporosity, and technical boundaries and challenges brought by the drawbacks of mesoporosity. Moreover, this Review subsequently reveals promising perspectives of how recently discovered approaches to different morphologies of MOFs (not necessarily entirely mesoporous) and their corresponding performances can be extended to minimize the shortcomings of mesoporosity, thus providing a wider and brighter scope of future research into mesoporous MOFs, but not just limited to the finite progress in the target substances alone.

Study on the Desorption Process of n-Heptane and Methyl Cyclohexane Using UiO-66 with Hierarchical Pores

UiO-66 (UiO for University of Oslo) is a zirconium-based metal-organic framework with reverse shape selectivity, which gives an alternative way to produce high-purity n-heptane ( nHEP) used for the manufacture of high-purity pharmaceuticals. A couple of studies have shown that UiO-66 gives a high selectivity on the separation of n-/iso-alkanes. However, the microporous structure of UiO-66 causes poor mass transport during the desorption process. In this work, hierarchical-pore UiO-66 (H-UiO-66) was synthesized and utilized as an adsorbent of nHEP and methyl cyclohexane (MCH) for systematically studying the desorption process of n-/iso-alkanes. A suite of physical methods, including X-ray diffraction patterns, verified the UiO-66 structures, and high-resolution transmission electron microscopy showed the existence of hierarchical pores. N₂ adsorption-desorption isotherms further confirmed the size distribution of hierarchical pores in H-UiO-66. Of particular note, the MCH/ nHEP selectivity of H-UiO-66 is similar to that of UiO-66 under the same adsorption conditions, and the desorption process of nHEP/MCH from H-UiO-66 is dramatically enhanced; namely, the desorption rates for nHEP/MCH from H-UiO-66 is enhanced by 30%/23% compared with UiO-66 at most. Moreover, desorption activation energy ( E_d) derived from temperature-programmed desorption experiments indicate that the E_d for nHEP/MCH is lower on H-UiO-66; that is, the E_d of MCH on H-UiO-66 is ∼37% lower than that on UiO-66 at most, leading to a milder condition for the desorption process. The introduction of hierarchical structures will be applicable for the optimization of the desorption process during separation on porous materials.

Fumarate-based metal-organic frameworks as a new platform for highly selective removal of fluoride from brick tea

Adsorption and removal of fluoride from brick tea is very important but challenging. In this work, two fumarate-based metal-organic frameworks (MOFs) were synthesized for the selective removal of fluoride from brick tea infusion. MOFs were examined for adsorption time, effect of dose, and uptake capacity at different initial concentrations and temperatures. Remarkably, over 80% fluoride removal was achieved by MOF-801 within 5 min at room temperature, while no significant adsorption occurred for the catechins and caffeine in the brick tea infusion. Further, with the use of the Langmuir equation, the maximum fluoride uptake capacity for the nontoxic calcium fumarate (CaFu) MOF was calculated to be as high as 166.11 mg g⁻¹ at 373 K. As observed from FTIR, EDX and XPS results, hydroxyl group in MOFs were substituted by fluoride. This work demonstrates that the novel fumarate-based MOFs are promising materials for the selective removal of fluoride from brick tea infusion.

Uncovering a reconstructive solid-solid phase transition in a metal-organic framework

A nanoporous three-dimensional metal-organic framework (MOF), ZnPurBr undergoes a transition to a previously unreported high-temperature phase, ZnPurBr-ht. The transition, which proceeds without mass loss, is uncovered through the use of differential scanning calorimetry (DSC). The new crystal structure was solved using single-crystal X-ray diffraction, and the mechanical properties of both phases investigated by nanoindentation and density functional theory. The anisotropy of the calculated Young's moduli showed good agreement with the crystallographic alignment of the stiff purinate organic linker. The results provide a prototypical example of the importance of the use of DSC in the MOF field, where its use is not currently standard in characterization.

Kinetic assembly of coordination networks

Kinetic assembly is an important method for obtaining desired materials in chemical synthesis and materials science. We highlight the kinetic assembly of porous coordination networks, which promote the production of interactive pore sites. The interactive pore sites can activate or stabilize guest molecules. The properties of interactive pores are typified by iodine chemisorption and small sulfur encapsulation. Using interactive pores, we trapped small sulfur allotropes, such as S₂, cyclo-S₃, bent-S₃, and S₆, demonstrating the importance of interactive pore sites. Here, we address the important aspects of interactive pore sites created by kinetic assembly of porous coordination networks.

Synthesis, structures and magnetic properties of two chiral mixed-valence iron(ii,iii) coordination networks

Two rare chiral mixed-valence iron(ii,iii) coordination networks have been synthesized through spontaneous asymmetrical crystallization from achiral units in the assembly process.

Magnetically recyclable Cu-BTC@Fe3O4 composite-catalyzed C(aryl)–S–P bond formation using aniline, P(O)H compounds and sulfur powder

A magnetically recyclable Cu-BTC@Fe₃O₄-catalyzed synthesis of S-aryl phosphorothioates using aniline as the aryl source and sulfur powder as the sulfur source has been developed.

Synergic effect of copper-based metal–organic frameworks for highly efficient C–H activation of amidines

A Cu–MOF-catalyzed C–H functionalization of substituted amidines was developed for the facile and efficient synthesis of benzimidazoles.