Membrane separation is very promising in solving energy and environmental challenges of separation process, and it has developed rapidly in recent decades. Metal-organic frameworks (MOFs) are a new type of microporous material with adjustable pores with uniform size, thus MOF membranes show promising potential for separation applications. With the rapid development of two-dimensional (2D) materials, 2D MOF membranes constructed with 2D MOF nanosheets, have attracted increasing attentions, where the pores of MOF could achieve molecular sieving, while both the nanochannels between the nanosheets and the pores of MOF nanosheets would provide mass transfer pathway for fast permeation. Therefore, 2D MOF membranes are expected to show both high permeability and selectivity, which might become a kind of high-performance membrane for industrial separations.

Metal-organic frameworks (MOFs) are a growing class of organic-inorganic hybrid crystalline porous materials, showing high levels of structural and chemical diversity. They have a wide range of applications in gas adsorption and separation, catalysis, sensing, biomedicine and other fields. Due to their intriguing properties such as high porosity, adjustable pore size and tunable surface functionality, MOFs have been gaining popularity as a promising platform for integration of various organic/inorganic functional nanomaterials in a predictable and controllable way. The combination of MOFs and functional components offers a possibility to generate synergetic effect between functional units, thus leading to the creation of multifunctional materials with performance superior to each individual components. In this review, we summarized recent research progress on controllable synthesis of MOF composites. There are basically two strategies, including “bottle in ship” and “ship in bottle”. Following that, preparation methods including solution infiltration, deposition, solid grinding and template synthesis, were discussed in detail. Light-to-heat conversion materials have always been a research focus due to their important applications in solar powered water evaporation and near-infrared (NIR) excited bioimaging and noninvasive cancer treatment. MOFs can not only show intrinsic structure-dependent photoresponse activity, but also serve as porous supports to facilitate the stabilization and spatial distribution of photothermal nanoparticles. Recently, MOF composites with photothermal effects have aroused increasing attention in the fields like tumor diagnosis and treatment, bacterial disinfection and synergistic catalysis. This review mainly focused on the recent research progress on photothermal MOF composites. We discussed the integration of functional MOFs with various inorganic/organic photothermal nanoparticles (e.g. Au, Pt, porphyrin, polydopamine etc.), along with the structure and photothermal application of the composites. Research about MOFs based light-to-heat conversion is at the stage of rapid development. Finally, we also give a prospect to the future development of multifunctional and photothermal MOF composites.

The conventional separation process of olefin/paraffin with cryogenic and high-pressure distillation usually exhibits high energy consumption and low efficiency. The adsorption separation technology is widely promising in the field of olefin/paraffin separation because of its mild operation conditions and high energy efficiency. In this work, high-throughput screening was adopted to find the optimal adsorbents from 12723 real metal-organic framework (MOF) materials, which is available for adsorption separation of 1,3-butadiene from C4 olefin/paraffin mixture. Firstly, 7681 adsorbents with suitable pore size and specific surface area were selected from the total database according to their structural parameters. Then their mechanical properties were computed by molecular mechanics. The mechanical properties of UIO-66 were used as the threshold to obtain 959 candidate MOFs with stable structure. Secondly, the grand canonical Monte Carlo (GCMC) simulation was performed to calculate the selective adsorption behavior of a quinary equimolar C4 olefin mixture in different candidate MOFs at 298 K and 0.1 MPa. According to their adsorption performance scores (APS) of 1,3-butadiene, the candidate MOFs are ranked to obtain 8 MOFs with the optimal adsorption and separation performance. The structural characteristics of MOFs with high adsorption and separation performance are revealed through quantitative structure-activity relationship, adsorption isotherm and ideal adsorption solution theory. The breakthrough curve simulation further verified that 2-cis-butene could effectively separate from 1,3-butadiene in the fixed bed filled with the optimal adsorbent RIGPEE01. Finally, it is determined that the preferential adsorption mechanism of 1,3-butadiene in RIGPEE01 is mainly due to the strong adsorption sites of Cu(I), π bond coupling effect and the size sieving effect based on the radial distribution function and binding energy analysis. The high-throughput screening method and the molecule-level insights on the olefin separation mechanism of MOFs proposed in this work have laid a theoretical foundation for the further development of new adsorbents for the separation of olefin/paraffin mixtures.

Selective catalytic reduction of NO_x with CO technology (CO-SCR) is supposed to be a cost-effective and environmentally friendly technique for NO_x abatement in the flue gas under CO-rich conditions. As a promising class of porous hybrid inorganic-organic materials, bimetallic metal-organic frameworks exhibit great physicochemical properties in catalysis area, whereas their application in low-temperature CO-SCR system are seldom reported. In this study, a series of bimetal organic-frameworks catalysts with different Ag contents were successfully prepared by a post-synthesis method and were assessed for NO reduction by CO. The typical experimental procedure for the synthesis of bimetallic Ag-Ni-MOF-74 catalysts is as follows: First, a light yellow Ni-MOF-74 sample was prepared by a hydrothermal method. Then 250 mg Ni-MOF-74, 1 mmol of NaBH₄ and AgNO₃ with different molar ratio (0.25, 0.5, 1 mmol) were added into 40 mL N,N-dimethylformamide (DMF) solution, and were stirred for 6 h. The mixtures were further moved into a Teflon-lined autoclave at 150 ℃ for 12 h. After washing with DMF and methanol, the obtained Ag_x-Ni-MOF-74 catalysts were dried at 60 ℃ under vacuum for 12 h. Totally, bimetallic Ag-Ni-MOF-74 catalysts exhibited a better low-temperature CO-SCR efficiency than monometallic Ni-MOF-74 catalysts. Especially, Ag₁-Ni-MOF-74 achieved a nearly 100% NO conversion in the temperature range from 200 ℃ to 300 ℃. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and hydrogen temperature programmed reduction (H₂-TPR) techniques were used to investigate the structure and properties of the samples. It was found that Ag addition not only enriched the form of more active sites, but also increased the specific surface area of the catalysts, which promote the activation and transfer of reactants. The synergistic effect between Ag and Ni species also contributed to enhancement of surface oxygen vacancies and accelerated the electron transfer in NO+CO reaction. By combining XPS and in situ FT-IR results, the mechanism of CO-SCR reaction over Ag-Ni-MOF-74 was proposed to follow Langmuir- Hinshelwood (L-H) mechanism, which exhibits a more readily low-temperature reaction rate and a lower reaction barrier than Eley-Rideal (E-R) mechanism.

This perspective summarizes the research progress of metal-organic frameworks (MOFs) materials used in lithium-ion battery/lithium-metal electrolytes. By summarizing several long-standing defects of lithium-ion batteries/lithium- metal batteries, MOFs materials are subsequently used as ion sieves, artificial electrode protective layers, quasi-solid electrolytes and used to adjust electrolytes’ configuration, the performance of batteries has been significantly improved. Finally, based on the characteristics of MOFs materials themselves, this perspective also makes a reasonable forward-looking outlook on the subsequent applications of MOFs materials in the field of electrochemical energy storage.

Hydrogen-bonded organic frameworks (HOFs), usually self-assembled by organic or metal-organic building blocks via intermolecular H-bonding interactions, have become a unique type of crystalline porous material. Although the weak and flexible nature of hydrogen bonds makes most HOFs fragile, the high stability and permanent porosity could be realized by the judicious selection of rigid building blocks with special spatial configuration as well as the introduction of framework interpenetration and/or other intermolecular interactions like π-π stacking and electrostatic interactions, etc. Compared with other crystalline porous materials like metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs), HOFs feature mild preparation condition, high crystallinity, permissible solution processability, easy healing and regeneration, etc. These distinguishing merits make HOFs capable to be used as unique multifunctional porous materials. Herein, we first review the basic rules to design and synthesize stable and porous HOFs, and then systematically summarize the representative supramolecular synthons and backbones that have been used to build stable and porous HOFs. Emphasis is put on the potential applications of HOFs in gas adsorption and separation, proton conduction, heterogeneous catalysis, luminescence and sensing, biological applications, enantiomeric resolution and aromatic compounds separation, pollutants removal, and structure determination, etc.

Proton exchange membranes (PEMs) are important components for novel fuel cells. A significant effort has been made by researchers towards proton conductive materials and membranes, some of which have been successfully commercialized. However, commercial perfluorosulfonic acid membranes like Nafion suffer key issues which limit their large-scale applications in a wide temperature range, including high cost and low operation temperature. Therefore, it is highly desirable to prepare new-type PEMs possessing high proton conductivity, thermal and chemical stability, water uptake and excellent durability. Metal organic frameworks (MOFs) are attractive candidates for proton exchange membranes due to their high porosity, ordering pore structures and excellent designability. This review focuses on the recent progress on proton-conductive MOF structures and their proton exchange membranes. In the first section, the authors briefly introduce the proton conducting mechanism of MOFs and their testing methods. The Grotthuss mechanism refers to the proton transferring process in a continuous and long-range hydrogen network, whereas the Vehicular mechanism involves in the diffusion of proton carrier molecules. Then in the next section, the authors summarize the progress on bulk MOFs proton conductors. According to the work condition, proton-conducting MOFs can be divided into two types, namely working under humid and anhydrous environment. These works show the potential of proton-conductive MOFs to be applied in a wide temperature range, and some of them even have reached a relatively high conductivity larger than 10^-2 S·cm^-1, comparable with Nafion. In the third section, a review on the MOFs-based proton exchange membranes is shown. Researchers have proven that MOFs thin films have huge potential on proton conduction. Nevertheless, most of the MOFs-based PEMs are still mixed matrix membrane (MMM) structure. In order to boost the performance of MMMs-type MOFs-based PEMs, several strategies can be applied such as modifying MOF with functional groups, using 1D/2D MOFs structure and introducing the third phase into membranes. Last, the authors discuss the current issues and perspectives on MOFs proton conductors and their PEMs.

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) are representative crystalline porous polymers. Due to their high surface area, high porosity, open channels, abundant functional groups and easy functionalization, they show great applications in gas storage and separation, catalysis, energy storage, photovoltaic devices, etc. Amino acids are the basic structural units that constitute peptides and proteins, which not only have important biological functions, but also play an important role in industrial applications such as pharmaceutical production, biodegradable plastics, and chiral catalysts. The introduction of amino acids into MOFs and COFs could endow them with diverse and flexible frameworks, special pore environment, and chiral sites, improving their biocompatibility and degradability to some extent and enriching their functions and applications. This review focuses on the progress of the amino acid functionalized MOFs and COFs, including their synthetic strategies, such as employing amino acids and their derivatives as building unit, covalent modification of amino acids onto the framework, and utilizing amino acids as modulators. The advantages and disadvantages of these strategies are compared and their challenges are discussed. In addition, we also introduce their applications in chiral separation, catalysis, adsorption and proton conduction. Finally, we summarize the current challenges in the preparation of amino acid functionalized crystalline porous polymers and outlook the future research direction in this field.

Metal-organic frameworks (MOFs), featuring the ultrahigh surface area, high porosity, tunable geometrical and chemical properties, show potential applications in gas adsorption/separation, heterogenous catalysis, etc. As the ubiquity of water vapor in the ambient environment and industrial gas streams, it is necessary to study on interaction mechanism between MOFs and water molecules and develop highly water-stable MOFs with desirable water adsorption/desorption behaviors. It not only has the scientific significance, but also great importance in promoting the practical applications of MOFs. Given the tailorable abilities of pore size, pore volume, cavity hydrophilicity and water stability, MOFs provide unprecedented advantages to explore the well-defined porous sorbents in molecular level, which facilitates the realization of reversible water vapor uptake and release at expected relative pressure and temperature together with high working capacity. For now, a wide range of hydrolytically stable MOFs including high-valence metal (e.g. Cr³⁺, Al³⁺, Zr⁴⁺, Ti⁴⁺) based frameworks have emerged as the advanced and promising porous sorbents for energy efficient applications, by utilizing water as eco-friendly adsorbate media and renewable heat. This review focuses on the following aspects:(1) the degradation mechanism of MOFs in liquid phase of water and the design concepts of hydrolytically stable MOFs by modulating their coordination bond based on the Pearson' hard/soft acid/base principle; (2) the physical or chemical water ad/desorption properties of MOFs; (3) the classification of numerous MOFs sorbents and conventional desiccants based on their hydrophilicity, which is approximately reflected by the relative humidity (RH) value of the inflection points (the RH where the steep uptake starts) in isotherms; (4) a variety of water adsorption-based applications of MOFs such as industrial gas dehydration, drinking water harvesting in the desert area, adsorption-based heat pump and indoor humidity regulation. Finally, the research priorities and development outlook are summarized and the future challenge with respect to water adsorption-based applications for the next-generation MOFs are outlined.

The reticular frameworks have crystalline and extended porous structures, which can not only orderly organize a variety of building blocks to form mesoscopic materials in a programmable way, but also perform an excellent platform for basic scientific research because of the regulatable and precise structures. The representative systems of reticular frameworks are metal organic frameworks (MOFs) and covalent organic frameworks (COFs). Mechanically interlocked structures are molecular aggregations interacted through mechanical bond to realize complex functions. The combination of reticular frameworks and mechanically interlocked structures can promote the basic research of the microscopic interlocked behaviors in solid states; and also organize the interlocked structures in a regular way to achieve more complex functions. The mechanically interlocked structures can be introduced into reticular frameworks in two strategies, using mechanically interlocked structures as building blocks participating in the construction of reticular frameworks; and forming woven or interlocked frameworks with whole interlocked skeleton from unlocked precursors. This review summarizes the important progresses in the emerging research field combining the reticular frameworks and mechanically interlocked structures. In the first section, after the brief introduction of reticular frameworks and mechanically interlocked structures respectively, the significances and strategies of the combination of the above two fields is described. In the second section, we reveal the systematic and representative research of mechanically interlocked structure as a part of building blocks participating in the construction of reticular frameworks, including rotaxane, shuttle and catenate. The mechanical motions of rotaxanes and shuttle within MOFs are intensively studied. The representative methods and structures of introducing rotaxane or catenate into reticular frameworks are presented. In the third section, we exhibit the reticular frameworks constructed through mechanical bond as the main interaction within the whole skeleton from unlocked precursors, including resilient woven frameworks and mechanically interlocked frameworks. The typical woven or interlocked frameworks are mostly templated from special metal complexes and showing reversible transition between crystal and non-crystal maintaining the whole interlocked skeleton. Finally, we summarize the whole paper and discuss the future development in this crossing field, such as the applications of these combined systems should be expanded and the mechanically interlocked frameworks constructed through interlocking discrete molecular rings are expected due to the potential excellent elastic properties.

Metal-organic frameworks (MOFs), a class of promising heterogeneous catalysts, though readily recyclable, usually suffer from poor dispersity and ease of sedimentation in liquid-phase reaction systems, which may lead to limited exposure of active sites and unsatisfied activity. Conventional hydrothermal synthesis often results in large MOF particles in bulk form and poor dispersity. The homogenization of MOF catalysts is an exciting but challenging task to integrate the advantages of both homogeneous and heterogeneous catalysts. Herein, by means of microwave-assisted synthetic approach, a soluble porphyrinic MOF, denoted as S-Al-PMOF, has been successfully fabricated. In contrast to the Bulk-Al-PMOF synthesized by the conventional hydrothermal route, which requires 180℃ and 16 h, the S-Al-PMOF obtained by the microwave-assisted method is very efficient and takes 30 min only at 140℃. While the as-synthesized S-Al-PMOF can be completely soluble in acetonitrile by ultrasonic dispersion to give a clear and transparent colloidal solution, the Bulk-Al-PMOF can form a turbid suspension liquid by continuous stirring, which easily aggregate with sedimentation in a short time after standing. Furthermore, the S-Al-PMOF can be easily separated from the solution by suction filtration and then re-dissolved in acetonitrile. This separation and re-dissolution process can be repeated several times to prove its good recovery and recycling. Given the outstanding light harvesting ability of Al-PMOF, photocatalytic H₂ production by water splitting has been adopted to examine the activity of both S-Al-PMOF and Bulk-Al-PMOF. As a result, the activity of S-Al-PMOF is around 14 times higher than that of Bulk-Al-PMOF, owing to excellent solubility of the former. Moreover, S-Al-PMOF also exhibits good recyclability in the consecutive three cycles of reaction. We believe that the successful synthesis of soluble Al-PMOF opens a new avenue to the homogenization of heterogeneous catalysts.

With the accelerating process of industrialization and urbanization, as well as the increasing proportion of the elderly in the world's population, we are facing more complex health threats related to bacterial infection. While the vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, the continued abuse and misuse of antibiotics has accelerated the spread of antibiotic-resistant bacterial strains and has resulted in substantial new challenges with respect to modern-day antibiotic-based treatments. Therefore, intelligent design of new antibacterial modalities to be used for treating human and livestock diseases is an extremely urgent priority for researchers in the fields of chemistry, chemical engineering, materials and biomedical sciences. Toward this end, the most intriguing of the new developments are metal-organic frameworks (MOFs). MOFs are versatile crystalline porous lattices of organic ligands and metal ion/clusters that formed by self-assembly via coordination bonds. Due to their unique characteristics, including relatively straight forward and simple methods for synthesis, large surface areas, novel and diverse structures, and adjustable porosity, MOFs not only play strong roles with respect to novel methods for gas storage and separation, they may also be utilized in unique applications associated with sensors mechanisms and catalysis. These features contribute to our current understanding of MOFs as promising candidates for the development of pharmaceutical and specifically antibacterial applications. In this review, antibacterial mechanisms, and the development of resistance to current antibiotic strategies are summarized and discussed. The main mechanisms by which bacteria show resistance to antibiotics include altered metabolic pathways, regulation of target sites, and inactivation, modification, and/or reduction in the capacity to accumulate antibacterial drugs. We consider recent progress on the development of MOFs, including the use of specific metal centers and ligands, metal nanoparticles, and drug-encapsulation, all of which have important applications with respect to antibacterial activities, and wound healing. Finally, the challenges and prospects of MOF-based antibacterial materials are discussed, including critical findings, which will help toward the development of the next generation antibacterial MOFs for human use.

Recovering C₂H₄ from refinery gas is an effective way to broaden the source of ethylene. However, it's a challenging task to separate C₂H₄ and C₂H₆ due to their very close physical properties and molecular size. Metal-organic frameworks (MOFs) are shown broad prospects in the field of light hydrocarbon separation in recent years. In this work, NH₃ is used to modify the structure of UTSA-280, the efficient separation of C₂H₄/C₂H₆ can be achieved through the adjustment of one-dimensional channels. UTSA-280 has undergone stepwise adsorption of ammonia gas at 298 K and 100 kPa. After partial ammonia removal, we obtained the modified UTSA-280 that ammonia adsorption modification with a mass loading of 5.6% for UTSA-280-M1 and 2.8% for UTSA-280-M2. The NH₃ modified UTSA-280 shows a unique ultramicroporous structure that can enhance the adsorption of C₂H₄ and does not adsorb the slightly larger C₂H₆, achieving the ideal C₂H₄/C₂H₆ adsorption selectivity (more than 1000). Ammonia molecules play the role of perfectly adjusting the size of one-dimensional channels and realize the ideal screening effect of C₂H₄/C₂H₆. The C₂H₄ adsorption capacity of NH₃ modified UTSA-280-M2 can be improved to 2.83 mmol/g at 298 K and 100 kPa (an increase of 29% compared with initial material). And its ultramicroporous structure can fully block the adsorption of C₂H₆, which finally achieves a C₂H₄/C₂H₆ selectivity over 1200. Grand Canonical Monte Carlo (GCMC) simulation of C₂H₄/C₂H₆ mixed gases (equal volume) adsorption results showed that the modified UTSA-280 had more C₂H₄ adsorption distribution in the mixed components than C₂H₆. Through the C₂H₄/C₂H₆ mixed gases breakthrough test at 298 K, NH₃ modified UTSA-280-M2 shows a separation time of more than 48 min, which is more than the initial 25 min. Compared with the unmodified material, the separation performance is nearly doubled. Scalable synthesis, stable structure, and the advantages of controllable performance after ammonia modification have prompted this material to have great prospects in the industrialization of C₂H₄/C₂H₆ separation.

As important chemical raw materials and energy source, C₄~C₆ hydrocarbons are mainly used to produce polymer rubber, plastics and high-quality gasoline, which requires high purity of the raw materials. For example, the purity requirement in 1,3-butadiene polymerization reactor is higher than 99.5%. When producing butyl rubber, tert-butylamine, pivalic acid, etc., the purity of isobutylene should surpass 99%. In the traditional petrochemical industry, C₄~C₆ hydrocarbons are mostly separated and purified through distillation, yet suffering from large energy consumption, high equipment cost and poor economic benefits. Adsorption separation with solid adsorbents can not only reduce energy cost and environmental footprints, but also improve separation efficiency. Metal-organic frameworks (MOFs) are a class of crystalline porous materials assembled from metal ions or clusters and organic linkers. Compared with zeolite, activated carbon and silica gel, MOFs feature high porosity, well-defined open channels, rich functional groups and diverse structures, showing great potentials in gas storage and separation, sensing, catalysis, photoelectric devices, drug release and delivery. Up to now, there have been many reports on separation and purification of C₄~C₆ hydrocarbons using MOFs by different mechanisms. Specifically, highly selective separation can be achieved by precisely adjusting the size and shape of the MOF channels to match the size of the target molecule. Besides, selecting MOFs with specific functional groups, open metal sites or flexible skeletons to regulate the interactions between the gas molecules and backbone, can also achieve efficient separation. This review introduced the importance of C₄~C₆ hydrocarbons separation and summarized the current research progress of using MOFs to separate and purify C₄~C₆ hydrocarbons. In addition, we also summed up the challenges of using MOFs as industrial adsorbents and pointed out the possible research directions in the future, which may provide ideas for designing new MOFs with high performance for crucial separation processes.

In this work, the separation performance of methane/ethane/propane (C₁, C₂ and C₃) mixture in the 137953 hypothetical metal-organic frameworks (MOFs) is calculated by high throughput computational screening and multiple machine learning (ML) algorithms. First, to avoid the competitive adsorption of water vapor, 31399 hydrophobic MOFs (hMOFs) were screened out. Then, grand canonical Monte Carlo (GCMC) simulations were employed to calculate the adsorption behavior of a mixture with a mole ratio of C₁:C₂:C₃=7:2:1 in these hMOFs, respectively. Second, the relationships among six MOF structures/energy descriptors (the largest cavity diameter (LCD), void fraction (f), volumetric surface area (VSA), Henry coefficient (K), heat of adsorption (Q_st), density of MOF (ρ)) and three performance indicators of MOFs (selectivities (S), adsorption capacities (N) of C₁, C₂, C₃ and their trade-offs (TSN)) were established. The LCDs were calculated by Zeo++software, and VSAs were calculated using RASPA software using He and N₂ as probes, respectively, and Q_st and K were calculated in an infinite dilution of each gas molecule in an infinite dilution state using NVT-MC method in RASPA software. Then, we found that there existed the "second peaks" of N and S in part of structure-property relationships, and all the optimal MOFs located in the range of second peaks, especially for the separation of C₁ or C₂. Third, the above-mentioned six MOF descriptors and three MOF performance indicators were trained, tested and predicted by four ML algorithms, including decision tree, random forest (RF), support vector machine and Back Propagation neural network. Although the predictive effect for the selectivity was very low, the introduction of TSN can significantly improve the accuracy of ML prediction, especially for RF algorithm (R=0.99). Therefore, the RF was used to quantitatively analyze the relative importance of each MOF descriptor, and found that three descriptors (K, LCD and ρ) possessed the highest importance for the separation of C₁ and C₂, and three other descriptors (K, Q_st and ρ) for the separation of C₃. Moreover, three simple and clear paths of optimal MOFs for C₁, C₂ and C₃ adsorption were designed by the decision tree model with the descriptors. Based on those paths, there were 96%, 85%, 95% probability that we can search for high-performance MOFs, respectively. Finally, the best 18 MOFs were identified for different separation applications of C₁, C₂ and C₃. This study reveals the second peaks and key MOF descriptors governing the adsorption of light alkane, develops quantitative structure-property relationships by ML, and identifies the best adsorbents from a large collection of MOFs for the separation of C₁, C₂ and C₃ from natural gas.

Oxygen evolution reaction (OER) is a crucial half reaction of electrochemical water splitting and metal-air batteries. But its sluggish four-electron reaction leads to a high overpotential. Current commercial OER catalysts are mainly noble metal-based materials, but their high cost restricts their broad application. Therefore, extensive efforts have been devoted to exploring low-cost and efficient OER catalysts. Nonprecious metal-based materials have been regarded as promising OER catalyst candidates, due to their abundancy on the earth, controllable morphologies and tunable chemical states. Among various nonprecious metal-based materials, metal-organic frameworks (MOFs) have attracted much attention, because of their large specific surface area and rich metal centers. However, their poor electrochemical activities, stabilities and conductivities severely affect their application in OER catalysis. To improve the activities of MOFs, several methods have been adopted, such as synthesizing ultrathin nanosheets, growing MOFs on nickel foam or carbon cloth, doping heteroatoms, and introducing synergistic interactions between two materials. In 1970, Wagner proposed a space-charge theory, which indicates that the carrier property can be tuned through adjusting interface. Inspired by this theory, constructing metal oxide-catalyst interface seems to be a promising strategy to improve activities of catalysts. CeO₂ is a well-known cocatalyst due to its reversible Ce³⁺/Ce⁴⁺ redox. Previous works have demonstrated that OER performance can be effectively improved through introducing CeO₂ since it can speed up the electron mobility and induce strong interaction between CeO₂ and metal sites. In this work, an efficient OER catalyst was achieved through introducing CeO₂ into FeNi MOF catalyst. FeNi MOF nanosheet arrays grown on nickel foam was firstly prepared via a solvothermal process. Then CeO₂ nanoclusters (5 nm) were coated onto FeNi MOF surface by electrodeposition. A series of characterizations were employed to study the morphology, structure and surface electronic state information of the as-obtained CeO₂/FeNi MOF. From X-ray photoelectron spectroscopic analysis, the doping of CeO₂ clusters and the strong electronic interaction between CeO₂ clusters and FeNi MOF induce the formation of Fe/Ni-O-Ce bonds and optimize the electronic structures of Fe/Ni sites, which will enhance OER activities. The OER performance tests confirm that CeO₂/FeNi MOF indeed exhibits a superior OER activity than FeNi MOF alone. The hybrid catalyst delivers a higher mass activity (235.4 A·g^-1) and a faster turnover frequency (0.065 s^-1) than those of FeNi MOF (43.8 A·g^-1, 0.018 s^-1). Compared with FeNi MOF, CeO₂/FeNi MOF also shows better OER kinetics, as evidenced by a decreased Tafel slope, a reduced charge transfer resistance. Besides, CeO₂/FeNi MOF presents an outstanding stability (50 h, 50 mA·cm^-2). All these features make our CeO₂/FeNi MOF a potential catalyst in the future application. The interfacial strategy through introducing CeO₂ to modulate Fe and Ni active sites may open a door for developing high-performance OER catalysts in future.

The pressure-swing adsorption (PSA) technology is the promising approach for O₂/N₂ separation because of its low cost and facile manipulation, in which adsorbents dominate the separation performance. In recent years, metal-organic frameworks (MOFs) have been recognized as the most potential adsorbents in gas adsorption and separation due to their ultrahigh surface area. In this work, MIL-101(Cr) with different weight percentages of graphene oxide (5%, 15% and 35%) was prepared by growing MIL-101(Cr) on pre-synthesized GO materials. The final product was activated under vacuum at 180℃ for 12 h. Structure characterization of different MIL-101(Cr)/GO composites revealed that MIL-101(Cr)/GO-15 with 15% GO additive exhibited the highest specific surface area (3486 m²·g^-1) and pore volume (2.39 cm³·g^-1) compared with pristine MIL-101(Cr) and the composites with 5% and 35% GO additives. The high surface area and pore volume are beneficial for the O₂ uptake of MIL-101(Cr)/GO-15. Compared with the O₂ uptake of MIL-101(Cr)/GO-5 (0.35 mmol·g^-1) and MIL-101(Cr)/GO-35 (0.31 mmol·g^-1), MIL-101(Cr)/GO-15 exhibited the highest uptake of 0.54 mmol·g^-1. Further pore size distribution analysis demonstrated that the enhanced O₂ uptake of MIL-101(Cr)/GO-15 can be ascribed to its increased fraction of mesopores. On the other hand, O₂/N₂ selectivity of different MIL-101(Cr)/GO composites was also calculated according to ideal adsorbed solution theory (IAST), from which it was found that MIL-101(Cr)/GO-15 displayed the highest O₂/N₂ selectivity (1.2) in a binary gas mixture with the volume fraction of O₂/N₂=1/4. Compared with pristine MIL-101, O₂/N₂ selectivity of MIL-101(Cr)/GO-15 was increased by 17.65%. Recyclability is one of the most important criteria to evaluate the gas adsorption performance of adsorbents. Therefore, the recyclability of MIL-101(Cr)/GO-15 was tested by measuring the O₂ adsorption and desorption isotherms for three cycles. It was revealed that 80% of O₂ uptake of MIL-101(Cr)/GO-15 was remained after three adsorp-tion/desorption cycles, implicating the outstanding recyclability of MIL-101(Cr)/GO-15.

Metal organic frameworks (MOFs) have unique advantages in adsorption and preconcentration of heavy metal ions due to their structure and composition characteristics, which make them show great potential in optical sensing of heavy metal ions. However, their applications in the field of electrochemical sensing is greatly limited because of their poor conductivity. In this work, a functionalized MOF composite, thermally reduced graphene oxide-Au nanoparticles-zeolitic imidazolate skeleton material (RGO-Au-ZIF-8), was fabricated. It exhibits much improved electrochemical properties compared with the pristine MOF. A novel electrochemical sensing platform was constructed based on it, and simultaneous detection of lead ions (Pb²⁺) and copper ions (Cu²⁺) in aqueous solution was realized. Specifically, the Au-ZIF-8 was prepared by adding polyvinylpyrrolidone (PVP)-stabilized Au nanoparticles (AuNPs) to the reaction solution of ZIF-8. The modification of AuNPs effectively improved the conductivity of the material. After compounding with RGO, the RGO-Au-ZIF-8 composite was prepared. The RGO was used as scaffold for the Au-ZIF-8 in the composite to increase the effective surface area of electrode and improve conductivity. The morphology and structure of the prepared materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-visible absorption spectroscopy (UV-Vis). The electrochemical properties of the modified electrodes were characterized by various electrochemical techniques. The experimental parameters, such as pH value of working solution, accumulation potential, accumulation time and composition ratio of Au-ZIF-8 to RGO were optimized. Under the optimized conditions, simultaneous and sensitive detection of Pb²⁺ and Cu²⁺ on the prepared electrochemical sensor was realized with the detection limits of 2.6×10^-9 and 7.8×10^-9 mol·L^-1 for Pb²⁺ and Cu²⁺, respectively (S/N=3). The interference test showed that the electrochemical sensor has good selectivity for the detection of Pb²⁺ and Cu²⁺, and further electrochemical studies revealed that the designed sensor has excellent reproducibility and good stability. The result of recovery test indicated that the prepared electrochemical sensor has great potential in Pb²⁺ and Cu²⁺ detection in real water samples. This work provides a new platform for simultaneous, rapid and sensitive detection of heavy metal ions, and greatly expands the electrochemical applications of MOF materials.

This work aims to explore a new method for the efficient enrichment of baicalin in Scutellaria baicalensis Georgi by using metal organic frameworks (MOFs) materials, and to open up new applications for MOFs in the adsorption direction. The zeolitic imidazolate framework-8 (ZIF-8) was synthesized by solvothermal method and characterized by structure to ensure its accurate synthesis. Baicalin was extracted from Scutellaria baicalinsis Georgi by ethanol extraction and acid precipitation method. The ZIF-8 was used to carry out the static adsorption experiment on the crude extract of Radix Scutellariae. After the adsorption equilibrium was reached, the mixture was centrifuged, and the residual concentration of baicalin was detected by high performance liquid chromatography method (HPLC). The recovered saturated adsorbed ZIF-8 material was washed with water and dried, and the phosphate buffered saline (PBS) solution of pH 6.8 was used as a desorption solution, and the desorption was performed by shaking. The content of baicalin in the desorbed solution was determined by HPLC to calculate the desorption rate and achieve the purpose of adsorbent recovery. In the adsorbing process, the effects of adsorbent dosage, pH and adsorbate concentration of the crude extract of Radix Scutellariae were also optimized, and the response surface test (RSM) was performed using Design Expert software to obtain optimal adsorption conditions. Under these conditions, the adsorption rate of ZIF-8 to baicalin in Radix Scutellariae was as high as 98.22%, and the adsorption effect was not significant on other components in Radix Scutellariae. The desorption rate of ZIF-8 adsorbed baicalin in pH 6.8 solution was 62.46%, and the purity of baicalin increased from 21.55% before adsorption to 64.27% after desorption, and ZIF-8 had good stability before and after adsorption, and the recovery rate reached 83.50%. Therefore, ZIF-8 has potential application value in the adsorption and purification of baicalin. The adsorption law and mechanism of ZIF-8 on baicalin were studied:The adsorption of baicalin on ZIF-8 accorded with the quasi-second-order kinetic equation, and the equilibrium adsorption data accorded with the Langmuir adsorption isotherm model.

Malignant tumor is considered to be one of the most threatening diseases to human health because it is easy to metastasis and relapse, hard to cure with high mortality. Construction of anti-tumor drug delivery systems would effectively improve the therapeutic efficiency of traditional tumor therapy agents. However, the complicated tumor micro-environment as well as the individual diversity of tumor would lead to low efficiency or treatment failure. The conventional tumor treatments, such as chemotherapy, radiotherapy and surgery, have been unable to satisfy the demand for tumor therapy owing to the severe side effect and low therapeutic efficiency. In recent years, researchers have designed a lot of multifunctional nano-drug carriers for efficient tumor therapy with reduced side effects. Metal-organic frameworks (MOFs), a class of ordered porous crystal materials, have received significant research attention for their applications in gas adsorption and separation, catalysis, drug delivery, immobilized bio-macromolecules and tumor therapy. Due to tunable inorganic building blocks and organic linkers, MOFs can not only integrate drugs or photosensitizers into periodic arrays, but also possess large pore sizes and high surface areas for drug encapsulation. Currently, the biomedical research of MOFs mainly includes the preparation of multifunctional biocompatible nanomaterials through controllable synthesis and reasonable surface modification. MOFs based nanomaterials with desired physiological functions have been widely used for targeting tumor imaging and therapy by utilizing their unique physical and chemical properties. The recent progress on the bio-functionalization of MOFs, including new design strategies and application in tumor therapy is summarized. Particularly, the construction of MOF-based nanoplatforms for tumor therapy on the basis of biomedical polymer modified MOFs is also described in detail. The development trends of MOFs for biomedical application are also prospected. We believe that this work will offer a preliminary understanding to design MOF-based drug delivery systems and acquire the therapeutic strategies of MOF-based nano-medicine for future clinical biomedical applications.

A series of bimetallic MOF-74-CoMn catalysts with different metal ratios have been successfully synthesized by hydrothermal method and applied in selective catalytic reduction of NO with CO (CO-SCR). The experimental procedure for the preparation of MOF-74-CoMn catalyst is as follows:The reaction solution was a 3.28 mmol mixture of Co(NO₃)₂·6H₂O and Mn(NO₃)₂·6H₂O, 1.09 mmol 2,5-dihydroxyterephthalic acid (H₄DOBDC) and 90 mL ethanol-DMF-water. The molar ratio of mixture (Co/Mn) was 1:0, 1:1, 1:2, 1:4, 1:6, respectively. The reactant solution was ultrasonically stired for 30 min until homogeneous. Then, the mixture was transferred into a 100 mL Teflon autoclave then kept in an oven at 100℃ for 24 h. Finally, after purified with DMF and methanol, the products were dried in a vacuum oven at 80℃ for 24 h to obtain a purple MOF-74-CoMn catalyst, which were stored in vacuum or an inert atmosphere. The prepared sample is referred to as MOF-74-Co1Mnx, where x represents a molar ratio of Co to Mn is 1:x (x=0, 1, 2, 4, 6). The SCR catalytic activities were carried out in a fixed-bed flow reactor in gas stream. The experimental results show that the NO_x conversion rate of bimetallic MOF-74-CoMn catalyst is generally higher than that of single metal MOF-74-Co catalyst, and their reaction temperature window is wider. Especially, MOF-74-Co1Mn2 exhibited the highest selective catalytic reduction of NO with CO (CO-SCR) performance which is close to 100% with a temperature range from 175 to 275℃. Further, the bimetallic MOFs catalysts were characterized by X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), N₂ adsorption/desorption, X-ray photoelectron spectroscopy (XPS), Hydrogen-temperature programed reduction (H₂-TPR) and Infrared spectroscopy (FTIR) techniques. The results showed that the synergistic effect between Co and Mn metals could obviously promote the formation of unsaturated metal sites and oxygen vacancies, thereby promoting their catalytic reduction efficiency of selective catalytic reduction of NO with CO (CO-SCR).

During the past decades, extensive investigations on metal-organic frameworks (MOFs) with ultrahigh surface area for gas adsorption and separation have been reported. With the increasing number of possible MOFs, it has been a great challenge to discover high-performing MOFs of interest from numerous structures. High-throughput computational screening (HTCS) is a powerful tool to accelerate the development of MOFs for application of interest and explores the quantitative structure-property relationship (QSPR) to facilitate the rational design of top-performing MOFs. In this review, we summarize the MOF databases used for HTCS, mainly including MOFs collected from experimentally synthesized MOFs (i.e. eMOFs), and the hypothetical MOFs constructed by computer-aided tools (i.e. hMOFs). Moreover, there are currently two important screening strategies, molecular simulation and machine learning-based HTCS. A vast majority of HTCS have been performed by molecular simulations including grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations, in which the accuracy of force field parameters play a criticl role in the reliability of HTCS. GCMC is able to predict the adsorption performance of MOFs such as adsorption capacity, selectivity and heat of adsorption, whereas MD is commonly used to estimate the dynamic property of adsorbates, e.g. diffusion coefficient and permeability. Additionally, lattice GCMC and classical density functional theory (cDFT) are also highlighted for computational screening of MOFs in this review. Machine learning consisting of various algorithms is a recently developed strategy with high efficiency and low computational cost, which is a more powerful and promising technique in future. At last, the investigations on the utilization of HTCS in CH₄ storage, H₂ storage, CO₂ capture and gas separation were outlined. By reviewing the recent research progress in HTCS, we pointed out the current challenges and opportunities for the furture development of HTCS for MOFs, which will be the major engine for the commercialization of MOFs in various applications of interests.

The worldwide climate issues such as the global warming and the sea level rising are becoming serious. In order to relieve the stress of environment, a lot of attempts have been made to reduce the emission of CO₂, which is the main component of greenhouse gases. CO₂ capture and conversion (C3) is an emerging technology, which directly converts the captured CO₂ into high value-added compounds or fuels such as formic acid, methanol and methane. Porphyrin metal-organic frameworks (PMOFs) are based on porphyrin or metalloporphyrin ligands and metal nodes. The combination of excellent thermal/chemical stability, strong absorption of visible light and long lifetime of excited state, and high CO₂ capture capacity paves the way for the applications of PMOFs in C3. In this review, we have firstly introduced the synthesis strategies of PMOFs, which are guided by framework topology, pillar-layer and metal-organic cage (MOC). With the good control of the pore sizes and thermal/chemical stability, the catalytic performances of PMOFs can be easily tuned:PMOFs that are prepared via the pillar-layer and MOC strategies are of relatively lower stability, and the ones that are guided by framework topology are of higher stability. Next, we have classified the types of PMOFs according to the secondary building units (SBUs). There are four types of PMOFs, and the SBUs include (1) the low-valence metal ions such as Cu²⁺ and Cd²⁺; (2) the paddle-wheel M₂(COO)₄ (M=Cu²⁺, Zn²⁺) units; (3) the infinite metal (such as Al³⁺, Ga³⁺ and In³⁺) oxide chains; (4) the hard metal (such as Cr³⁺, Fe³⁺, Ti⁴⁺, Zr⁴⁺, Hf⁴⁺, and rare earth metals) oxide clusters. The structure characters and stability have been described afterwards. The coordination bonds in the first and second types of SBUs are relatively weak. For comparison, most of the PMOFs based on the infinite metal oxide chains and hard metal oxide cluster exhibit high thermal/chemical stabilities, which could be used for practical applications towards C3. Then, we have summarized the recent works about applications of PMOFs in C3, which are divided into four parts, including the selective capture of CO₂, organic transformations with CO₂, CO₂ photoreduction and CO₂ electroreduction. Selective capture of CO₂ from a mixture of gases is one of the most important applications, considering that less energy and lower temperatures/pressures are required. Through the catalytic cycloaddition reaction of CO₂ and epoxides, the important products of cyclic carbonates can be produced. Some of the catalytic reactions can be carried out at 0.1 MPa and room temperature with high yields. With the assistance of environmentally friendly visible light, CO₂ can be photoreduced into fuels such as formate ion, methanol and methane. In addition, two typical examples of CO₂ electroreduction have been discussed in this review. Through the process of photoreduction and electroreduction, clean energies such as solar light and electricity can be employed to help transfer the green gas CO₂ into fuels. At the end, we have discussed the merits and challenges of PMOFs in the applications of C3. Selective adsorption of CO₂ from other gases, especially NO_x, SO_x and other flue gases, is highly required. The efficiency of the catalytic cycloaddition reaction should be further improved, especially cutting down the reaction time. Reaction efficiency and product selectivity of photoreduction and electroreduction should be improved. Photoelectrocatalytic reduction of CO₂, which combines both advantages of photoreduction and electroreduction, should be a hot topic in the future. The ideal system should include both a photoanode for water oxidation and a photocathode for CO₂ reduction that are linked by a wire without external applied bias, achieving the dream of artificial photosynthesis.