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.
The recent advances of using metal–organic framework (MOF) materials as separating agents in the separation and purification of light hydrocarbons mixtures are summarized. The existing challenges and possible research directions related to the further exploration of porous MOFs in this very active field are also presented.
Flexible metal–organic frameworks (MOFs) receive much attention owing to their attractive properties that originate from their flexibility and dynamic behavior, and show great potential applications ...in many fields. Here, recent progress in the discovery, understanding, and property investigations of flexible MOFs are reviewed, and the examples of their potential applications in storage and separation, sensing, and guest capture and release are presented to highlight the developing trends in flexible MOFs.
Flexible metal–organic frameworks are widely investigated as functional materials based on their remarkable properties, and potential applications of these materials are found in many fields. The most recent advances in the discovery, understanding and property investigations are reviewed, and new trends for their applications are highlighted.
The design and development of efficient catalytic materials with synergistic catalytic sites always has long been known to be a thrilling and very dynamic research field. Crystalline porous materials ...(CPMs) mainly including metal–organic frameworks and zeolites with high scientific and industrial impact have recently been the subject of extensive research due to their essential role in modern chemical industrial processes. The rational incorporation of guest species in CPMs can synergize the respective strengths of these components and allow them to collaborate with each other for synergistic catalysis, leading to enhanced catalytic activity, selectivity, and stability in a broad range of catalytic processes. In this review, the recent advances in the development of CPMs‐confined active metal species, including metal nanoparticles, metal/metal oxides heteroparticles, metal oxide, subnanometric metal clusters, and polyoxometalates, for heterogeneous catalysis, with a particular focus on synergistic effects between active components that result in an enhanced performance are highlighted. Insights into catalysts design strategies, host–guest interactions, and structure–property relationships have been illustrated in detail. Finally, the existing challenges and possible development directions in CPMs‐based encapsulation‐structured synergistic catalysts are discussed.
Incorporation of active metal species in crystalline porous materials (CPMs) can synergize the respective strengths and allow them to collaborate with each other for synergistic catalysis. In this review, the state‐of‐the art progress in the encapsulation of catalytically active metal species by CPMs as well as their synergy functions for enhanced catalytic performance is summarized in detail.
Organic donor–acceptor systems have attracted much attention due to their various potential applications. However, the rational construction and modulation of highly ordered donor–acceptor systems ...could be a challenge due to the complicated self‐assembly process of donor and acceptor species. Considering the well‐defined arrangement of species at the molecule level, a crystalline host–guest system could be an ideal platform for the rational construction of donor–acceptor systems. Herein, it is shown how the rational construction of highly tunable donor–acceptor materials can be achieved based on a crystalline host–guest platform. Within the well‐established metal–organic framework NKU‐111 as the crystalline host enabled by the relatively stable coordination‐directed assembly, the introduction and arrangement of guest molecules in the crystals allow the rational construction of the NKU‐111⊃guest donor–acceptor system. The donor–acceptor interaction in the systems can be readily modulated with different guest molecules, which can be justified by the well‐demonstrated guest‐dependent characteristics. Accordingly, the NKU‐111⊃guest reveals highly tunable donor–acceptor properties such as charge‐transfer‐based emissions and electrical conductivity. This work indicates the potential of crystalline host–guest systems as an ideal platform for systematic investigations of donor–acceptor materials.
A donor–acceptor material based on a host–guest crystalline material platform is raised. As a proof of concept, a metal–organic framework (NKU‐111) is utilized as a host acceptor for the accommodation of aromatic donor guests. The resulting donor–acceptor system features highly tunable charge‐transfer‐based emissions and conductivity, indicating the rationality and efficiency of this strategy.
With H2O or NH3 stimuli, the blue cobalt‐based metal–organic framework (MOF) BP can reversibly transform to red RP. The removal/recovery of terephthalate ligands accompanied by the transformation ...leads to a gate effect, which allows the encapsulation and release of small solvent molecules under certain conditions. This is the first example of topology transformation from a self‐penetrating to interpenetrating net in 3D MOFs.
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•The recent progress in exploiting reverse-selective MOF materials for the efficient separation and purification of light hydrocarbons has been summarized.•The performance evaluation ...of reverse adsorptive separation has been presented and the strategies adopted to realize the reverse adsorption behaviors have been summarized.•The structure–property relationship of reverse-selective MOFs has been exhibited.•The existing challenges and the future prospects of reverse-selective MOFs in the separation of hydrocarbons mixtures are discussed.
The separation and purification process of hydrocarbons is one of the crucial and daunting challenges in the petrochemistry field, which is widely depended on cryogenic distillation by heat-driven for separation. Advanced alternative methods have been proposed, such as extraction, membrane separation, adsorptive separation. Adsorptive separation process based on selective porous solid adsorbent is particularly noteworthy due to the advantages of high efficiency and low energy consumption. Metal-organic frameworks (MOFs), as one kind of novel crystalline organic–inorganic hybrid porous solid materials, have been widely used in the field of separation and purification benefiting from their unique structure features. There are many reverse adsorption behaviors during the separations of hydrocarbons mixtures using MOFs, that is it could directly adsorb a small part of impurities and the desired target substance could be directly obtained, which could eliminate the desorption process and make the separation process more energy efficient, greener and environmentally friendly. Recent years, such studies are increasing rapidly and therefore need to be summarized for at a glance. In this review, we intend to exhibit the development of reverse-selective MOFs, which is superior to other types porous materials for the separation of light hydrocarbons. The evaluation of reverse adsorptive separation has been described and the strategies adopted to realize the reverse adsorption behaviors have been summarized. Furthermore, the existing challenges and the future prospects of reverse-selective MOFs in this active field are discussed elaborately.
A microporous three-dimensional hydrogen-bonded organic framework (HOF-5) has been constructed from a new organic linker 4,4′,4″,4‴-tetra(2,4-diamino-1,3,5-triazin-6-yl)tetraphenylethene. Activated ...HOF-5a exhibits a stepwise N2 adsorption isotherm at 77 K, suggesting framework flexibility. The structure of activated HOF-5a has been established by powder X-ray diffraction studies, indicating a significant framework contraction from as-synthesized HOF-5 to activated HOF-5a of ∼21% by volume. HOF-5a shows moderately high porosity with a Brunauer–Emmett–Teller (BET) surface area of 1101 m2/g, and takes up a large amount of acetylene and carbon dioxide under ambient conditions. Powder neutron diffraction studies and theoretical calculations reveal that suitable pore sizes, curvatures, and functional sites collectively enable HOF-5a to encapsulate a high density of carbon dioxide molecules packed in a pseudo-one-dimensional array along the pore channel.
Physical adsorption of gas molecules in microporous materials is an exothermic process, with desorption entropy driving a decrease in uptake with temperature. Enhanced gas sorption with increasing ...temperature is rare in porous materials and is indicative of sorbate initiated structural change. Here, sorption of C2H6, C3H6, and C3H8 in a flexible microporous metal–organic framework (MOF) {Cu(FPBDC)·DMF} n (NKU-FlexMOF-1) (H2FPBDC = 5-(5-fluoropyridin-3-yl)-1,3-benzenedicarboxylic acid) that increases with rising temperature over a practically useful temperature and pressure range is reported along with other small molecule and hydrocarbon sorption isotherms. Single X-ray diffraction studies, temperature-dependent gas sorption isotherms, in situ and variable temperature powder X-ray diffraction experiments, and electronic structure calculations were performed to characterize the conformation-dependent sorption behavior in NKU-FlexMOF-1. In total, the data supports that the atypical sorption behavior is a result of loading-dependent structural changes in the flexible framework of NKU-FlexMOF-1 induced by sorbate-specific guest–framework interactions. The sorbates cause subtle adaptations of the framework distinct to each sorbate providing an induced-fit separation mechanism to resolve chemically similar hydrocarbons through highly specific sorbate–sorbent interactions. The relevant intermolecular contacts are shown to be predominantly repulsion and dispersion interactions. NKU-FlexMOF-1 is also found to be stable in aqueous solutions including toleration of pH changes. These experiments demonstrate the potential of this flexible microporous MOF for cost and energy efficient industrial hydrocarbon separation and purification processes. The efficacy for the separation of C3H6/C3H8 mixtures is explicitly demonstrated using NKU-FlexMOF-1a (i.e., activated NKU-FlexMOF-1) for a particular useful temperature range.
Metal-organic frameworks (MOFs) constructed with metal ions/clusters and organic ligands have emerged as an important family of porous materials for various applications. However, the stability of ...this class of materials is crucial for their practical applications, which might be improved by varying their chemical composition and/or structurally tuning them. To fabricate MOFs with high stability, several strategies for enhancing the stability of MOFs have been developed, in which the strength of metal-ligand bonds is especially considered: the use of highly charged cations and higher p
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ligands, and varying the chemical functionality of linkers. On the other hand, the regulation of their structural architectures is also investigated: interpenetrated frameworks, multi-walled frameworks, and self-strengthening of the frameworks. In addition, the surface modification can also improve the stability of the materials. In this review, we introduce and summarize these strategies from the viewpoint of structural tuning and component choosing, providing useful instructions for the further design and synthesis of MOFs with high-level stability.
Stability of MOFs is a crucial issue for their practical applications, which might be improved by varying their chemical composition and/or structurally tuning them. Several strategies for enhancing the stability of MOFs were provided.
Direct hydrogenation of CO2 to methanol using green hydrogen has emerged as a promising method for carbon neutrality, but qualifying catalysts represent a grand challenge. In2O3/ZrO2 catalyst has ...been extensively applied in methanol synthesis due to its superior activity; however, the electronic effect by strong oxides‐support interactions between In2O3 and ZrO2 at the In2O3/ZrO2 interface is poorly understood. In this work, abundant In2O3/ZrO2 heterointerfaces are engineered in a hollow‐structured In2O3@ZrO2 heterostructure through a facile pyrolysis of a hybrid metal–organic framework precursor MIL‐68@UiO‐66. Owing to well‐defined In2O3/ZrO2 heterointerfaces, the resultant In2O3@ZrO2 exhibits superior activity and stability toward CO2 hydrogenation to methanol, which can afford a high methanol selectivity of 84.6% at a conversion of 10.4% at 290 °C, and 3.0 MPa with a methanol space‐time yield of up to 0.29 gMeOH gcat−1 h−1. Extensive characterization demonstrates that there is a strong correlation between the strong electronic In2O3–ZrO2 interaction and catalytic selectivity. At In2O3/ZrO2 heterointerfaces, the electron tends to transfer from ZrO2 to In2O3 surface, which facilitates H2 dissociation and the hydrogenation of formate (HCOO*) and methoxy (CH3O*) species to methanol. This study provides an insight into the In2O3‐based catalysts and offers appealing opportunities for developing heterostructured CO2 hydrogenation catalysts with excellent activity.
The direct hydrogenation of CO2 into methanol has been regarded as the one of the most economical and effective ways to reduce CO2 emissions. Here, we constructed a hollow‐structured In2O3@ZrO2 by a hybrid MOF template‐directed strategy. The resultant In2O3@ZrO2 heterostructure shows high CO2 hydrogenation activity towards CH3OH (gMeOHgcat−1) with a selectivity of 84.6%.
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