Occurrence, toxicity and adsorptive removal of the chloramphenicol antibiotic in water: a review

Chloramphenicol is a broad-spectrum bacterial antibiotic used against conjunctivitis, meningitis, plague, cholera, and typhoid fever. As a consequence, chloramphenicol ends up polluting the aquatic environment, wastewater treatment plants, and hospital wastewaters, thus disrupting ecosystems and inducing microbial resistance. Here, we review the occurrence, toxicity, and removal of chloramphenicol with emphasis on adsorption techniques. We present the adsorption performance of adsorbents such as biochar, activated carbon, porous carbon, metal-organic framework, composites, zeolites, minerals, molecularly imprinted polymers, and multi-walled carbon nanotubes. The effect of dose, pH, temperature, initial concentration, and contact time is discussed. Adsorption is controlled by π-π interactions, donor-acceptor interactions, hydrogen bonding, and electrostatic interactions. We also discuss isotherms, kinetics, thermodynamic data, selection of eluents, desorption efficiency, and regeneration of adsorbents. Porous carbon-based adsorbents exhibit excellent adsorption capacities of 500-1240 mg g^-1. Most adsorbents can be reused over at least four cycles.

Functionalization of a stable AIE-based hydrogen-bonded organic framework for white light-emitting diodes

Hydrogen-bonded organic frameworks (HOFs) have received tremendous attention in recent years due to the good designability. However, the pure organic nature of HOFs sometimes limits the application development and performance improvement. Functionalizing is an effective strategy to control and modulate material properties, which can achieve properties that cannot be achieved by a pristine material. Herein, a series of HOF-76⊃DSMI were synthesized through functionalizing the stable AIE-based HOF-76 by incorporating a red dye which complements the deficiency of the red component of HOF-76. Then, a single matrix white light-emitting diode (WLED) was fabricated by coating the HOF-76⊃DSMI material on a 460 nm blue LED with CIE chromaticity coordinates of (0.333, 0.329), a correlated colour temperature (CCT) of 5490 K and a colour rendering index (CRI) of 80.

We successfully fabricated a white light-emitting diode by coating functionalized AIE-based HOF-76 material on a 460 nm blue LED chip.

Hexahydric Components Metal Organic Frameworks Constructed by Multiple Ligands and Mixed-Valence Ions

In this work, we report two multi-component MOFs [CH3NH2CH3]2[FeIII2MII10(tz)11(HCO2)12(btc)5/3] (MII10 = FeII10 for 1 and MII10 = FeII2CoII8 for 2) obtained by solvothermal assembling formate, benzene-1,3,5-tricarboxylate (btc) and 1,2,4 triazole...

Preparation of monosodium 2-sulfoterephthalate to make a MIL-101(Cr)–SO3H catalyst

MIL-101(Cr)-SO3H has excellent thermal and chemical stabilities, making it an ideal porous acid catalyst for many organic reactions and petrochemical industries. It's starting ligand can be lab-prepared.

Post-synthetic modification within MOFs: a valuable strategy for modulating their ferroelectric performance

It is a great route designing new MOF ferroelectrics to enrich the scope of ferroelectrics or improving the ferroelectric performance to enhance the opportunity of applications through the strategy of post-synthetic modification (PSM).

Metal-organic frameworks in pursuit of size: the development of macroscopic single crystals REMINDER: Personal invitation to contribute to Dalton Transactions - CoordNetworks

Metal-organic frameworks are versatile structures with many different applications, from the industry to the clinic. Despite multiple synthesis approaches are possible to coordinate metals and organic ligands, some common strategies...

Linking metal-organic cages pairwise as a design approach for assembling multivariate crystalline materials

Using metal-organic cages (MOCs) as preformed supermolecular building-blocks (SBBs) is a powerful strategy to design functional metal-organic frameworks (MOFs) with control over the pore architecture and connectivity. However, introducing chemical complexity into the network via this route is limited as most methodologies focus on only one type of MOC as the building-block. Herein we present the pairwise linking of MOCs as a design approach to introduce defined chemical complexity into porous materials. Our methodology exploits preferential Rh-aniline coordination and stoichiometric control to rationally link Cu4L4 and Rh4L4 MOCs into chemically complex, yet extremely well-defined crystalline solids. This strategy is expected to open up significant new possibilities to design bespoke multi-functional materials with atomistic control over the location and ordering of chemical functionalities.

Chemically-Engineered Porous Molecular Coatings as Reactive Oxygen Species Generators and Reservoirs for Long-Lasting Self-Cleaning Textiles

Wearable personal protective equipment that is decorated with photoactive self-cleaning materials capable of actively neutralizing biological pathogens is in high demand. Here, we developed a series of solution-processable, crystalline porous materials capable of addressing this challenge. Textiles coated with these materials exhibit a broad range of functionalities, including spontaneous ROS generation upon absorption of daylight, and long-term ROS storage in dark conditions. The ROS generation and storage abilities of these materials can be further improved through chemical engineering of the precursors without altering the three-dimensional assembled superstructures. In comparison with traditional TiO 2 or C 3 N 4 self-cleaning materials, the fluorinated molecular coating material HOF-101-F shows a 10- to 60-fold enhancement of ROS generation and 10- to 20- fold greater ROS storage ability. Our results pave the way for further developing self-cleaning textile coatings for the rapid deactivation of highly infectious pathogenic bacteria under both daylight and light-free conditions.

Applications of water-stable metal-organic frameworks in the removal of water pollutants: A review

Because the pollutants produced by human activities have destroyed the ecological balance of natural water environment, and caused severe impact on human life safety and environmental security. Hence the task of water environment restoration is imminent. Metal-organic frameworks (MOFs), structured from organic ligands and inorganic metal ions, are notable for their outstanding crystallinity, diverse structures, large surface areas, adsorption performance, and excellent component tunability. The water stability of MOFs is a key requisite for their possible actual applications in separation, catalysis, adsorption, and other water environment remediation areas because it is necessary to safeguard the integrity of the material structure during utilization. In this article, we comprehensively review state-of-the-art research progress on the promising potential of MOFs as excellent nanomaterials to remove contaminants from the water environment. Firstly, the fundamental characteristics and preparation methods of several typical water-stable MOFs include UiO, MIL, and ZIF are introduced. Then, the removal property and mechanism of heavy metal ions, radionuclide contaminants, drugs, and organic dyes by different MOFs were compared. Finally, the application prospect of MOFs in pollutant remediation prospected. In this review, the synthesis methods and application in water pollutant removal are explored, which provide ways toward the effective use of water-stable MOFs in materials design and environmental remediation.

Two transition complexes based on 1H-benzimidazole-5,6-dicarboxylic acid: Synthesis, structure and photocatalytic degradation of dyes

Metal-organic frameworks [Co(Hbidc)(H2O)2] (1) and [Mn(Hbidc)(H2O)] (2), with multidentate 1H-benzimidazole-5,6-dicarboxylic acid (H3bidc) ligand, have been synthesized under hydro/solvothermal conditions and structurally characterized by elemental analysis, IR spectrum, and single-crystal X-ray diffraction. Single-crystal X-ray diffraction analysis revealed that the center Co atom of complex 1 is six-coordinated with three-dimensional supramolecular structure and center Mn of complex 2 is five-coordinated with exhibiting a 2D layered network. The photodegradation of Crystal violet dye and Methylene blue dye were studied firstly by complexes 1 and 2 as photocatalysts. Research result indicates that the degradation rate for complex 1 can reach 89.85% , 90.6% and that for complex 2 can reach 88.28% , 79.48% . At the same time, corresponding to photocatalytic kinetics was performed.

Symmetry-Guided Synthesis of N,N'-Bicarbazole and Porphyrin-Based Mixed-Ligand Metal-Organic Frameworks: Light Harvesting and Energy Transfer

In the past decades, many attempts have been made to mimic the energy transfer (EnT) in photosynthesis, a key process occurring in nature that is of fundamental significance in solar fuels and sustainable energy. Metal-organic frameworks (MOFs), an emerging class of porous crystalline materials self-assembled from organic linkers and metal or metal cluster nodes, offer an ideal platform for the exploration of directional EnT phenomena. However, placing energy donor and acceptor moieties within the same framework with an atomistic precision appears to be a major synthesis challenge. In this work, we report the design and synthesis of a highly porous and photoactive N,N'-bicarbazole- and porphyrin-based mixed-ligand MOF, namely, NPF-500-H₂TCPP (NPF = Nebraska porous framework; H₂TCPP = meso-tetrakis(4-carboxyphenyl)porphyrin), where the secondary ligand H₂TCPP is incorporated precisely through the open metal sites of the equatorial plane of the octahedron cage resulting from the underlying (4,8) connected network of NPF-500. The efficient EnT process from N,N'-bicarbazole to porphyrin in NPF-500-H₂TCPP was captured by time-resolved spectroscopy and exemplified by photocatalytic oxidation of thioanisole. These results demonstrate not only the capability of NPF-500 as the scaffold to precisely arrange the donor-acceptor assembly for the EnT process but also the potential to directly utilize the EnT process for photocatalytic applications.

Four Inorganic-Organic Hybrid Borates: From 2D Layers to 3D Oxoboron Cluster Organic Frameworks

Four inorganic-organic hybrid borates, K[B₆O₉(OH)(en)]·H₂O (1, en = ethylenediamine), K[B₆O₉(OH)(1,3-dap)]·H₂O (2, 1,3-dap = 1,3-diaminopropane), K[B₆O₉(OH)(1,6-dah)_0.5]·H₂O (3, 1,6-dah = 1,6-diaminlhexane) and [(1,3-dap)Cd@B₅O₈(OH)]·0.5H₂O (4), were made under solvothermal conditions. 1 and 2 are isostructural and feature a 2D layer built by B₆O₉(OH) clusters and modified by en and 1,3-dap via B-N-C linkages. By replacing en and 1,3-dap with longer and more flexible 1,6-dah, a new type of oxoboron cluster organic framework 3 was obtained, which was composed of the same B₆O₉(OH) cluster layers as in 1 and 2 and 1,6-dah linkers. By replacing alkali metal K with transition metal Cd under similar synthetic conditions, another type of oxoboron cluster organic framework 4 was made in which the Cd-centered wheel cluster layers and 1,3-dap linkers were connected via Cd-N-C linkages.

Fabrication of stable multivariate metal-organic frameworks with excellent adsorption performance toward bisphenols from environmental samples

As a type of environmental endocrine disrupting chemicals, bisphenols (BPs) have a certain embryonic toxicity and teratogenicity, which can significantly increase the risks of breast cancer, prostate cancer, leukemia and other cancers. In this work, stable multivariate metal-organic frameworks (UiO-66-NH₂/TCPP_x) were synthesized via in situ one-pot method and used as miniaturized dispersive solid-phase extraction (dμSPE) sorbents for extraction of trace BPs from environmental samples. The phase purity, crystal morphology and physical properties of UiO-66-NH₂/TCPP_x samples were varied by adjusting the mass ratio of TCPP. The extraction performance of UiO-66-NH₂/TCPP_x samples were investigated and UiO-66-NH₂/TCPP_1.0 exhibited the highest adsorption efficiency. Besides, UiO-66-NH₂/TCPP_1.0 possessed excellent recycling stability for the adsorption and desorption of BPs more than 20 cycles. The experimental parameters including amount of adsorbent, adsorption time, sample solution pH, temperature, desorption time and desorption solvents which affecting the efficiency of dμSPE were studied, respectively. Good linearity (R² > 0.9992) in range of 0.1-200 ng mL^-1 was obtained. The detection limits (S/N = 3) and quantification limits (S/N = 10) were achieved at 0.03-0.08 ng mL^-1 and 0.1-0.5 ng mL^-1, respectively. The relative standard deviations (RSDs) of intra-day and inter-day ranged from 2.5 to 5.5% and 1.1-6.8%. Enrichment factors were calculated in the range of 303-338. The obtained recoveries of bisphenol F (BPF), bisphenol A (BPA), bisphenol B (BPB) and bisphenol AF (BPAF) were 81.26-91.03% (RSDs = 0.96-6.47%), 82.2-97.27% (RSDs = 0.45-6.15%), 87.56-97.26% (RSDs = 1.1-6.22%) and 82.2-100.8% (RSDs = 0.46-4.07%). The UiO-66-NH₂/TCPP_1.0 can be employed as potential dμSPE sorbents for the enrichment of trace BPs in the environmental samples.

Multifunctional Magnesium Organic Framework-Based Microneedle Patch for Accelerating Diabetic Wound Healing

Diabetic wound healing is one of the major challenges in the biomedical fields. The conventional single drug treatments have unsatisfactory efficacy, and the drug delivery effectiveness is restricted by the penetration depth. Herein, we develop a magnesium organic framework-based microneedle patch (denoted as MN-MOF-GO-Ag) that can realize transdermal delivery and combination therapy for diabetic wound healing. Multifunctional magnesium organic frameworks (Mg-MOFs) are mixed with poly(γ-glutamic acid) (γ-PGA) hydrogel and loaded into the tips of MN-MOF-GO-Ag, which slowly releases Mg²⁺ and gallic acid in the deep layer of the dermis. The released Mg²⁺ induces cell migration and endothelial tubulogenesis, while gallic acid, a reactive oxygen species-scavenger, promotes antioxidation. Besides, the backing layer of MN-MOF-GO-Ag is made of γ-PGA hydrogel and graphene oxide-silver nanocomposites (GO-Ag) which further enables excellent antibacterial effects for accelerating wound healing. The therapeutic effects of MN-MOF-GO-Ag on wound healing are demonstrated with the full-thickness cutaneous wounds of a diabetic mouse model. The significant improvement of wound healing is achieved for mice treated with MN-MOF-GO-Ag.

In Situ Investigation of Multicomponent MOF Crystallization during Rapid Continuous Flow Synthesis

Access to the potential applications of metal-organic frameworks (MOFs) depends on rapid fabrication. While there have been advances in the large-scale production of single-component MOFs, rapid synthesis of multicomponent MOFs presents greater challenges. Multicomponent systems subjected to rapid synthesis conditions have the opportunity to form separate kinetic phases that are each built up using just one linker. We sought to investigate whether continuous flow chemistry could be adapted to the rapid formation of multicomponent MOFs, exploring the UMCM-1 and MUF-77 series. Surprisingly, phase pure, highly crystalline multicomponent materials emerge under these conditions. To explore this, in situ WAXS was undertaken to gain an understanding of the formation mechanisms at play during flow synthesis. Key differences were found between the ternary UMCM-1 and the quaternary MUF-7, and key details about how the MOFs form were then uncovered. Counterintuitively, despite consisting of just two ligands UMCM-1 proceeds via MOF-5, whereas MUF-7 consists of three ligands but is generated directly from the reaction mixture. By taking advantage of the scalable high-quality materials produced, C6 separations were achieved in breakthrough settings.

Advanced strategies in Metal-Organic Frameworks for CO2 Capture and Separation

The continuous carbon dioxide (CO₂ ) gas emissions associated with fossil fuel production, valorization, and utilization are serious challenges to the global environment. Therefore, several developments of CO₂ capture, separation, transportation, storage, and valorization have been explored. Consequently, we documented a comprehensive review of the most advanced strategies adopted in metal-organic frameworks (MOFs) for CO₂ capture and separation. The enhancements in CO₂ capture and separation are generally achieved due to the chemistry of MOFs by controlling pore window, pore size, open-metal sites, acidity, chemical doping, post or pre-synthetic modifications. The chemistry of defects engineering, breathing in MOFs, functionalization in MOFs, hydrophobicity, and topology are the salient advanced strategies, recently reported in MOFs for CO₂ capture and separation. Therefore, this review summarizes MOF materials' advancement explaining different strategies and their role in the CO₂ mitigations. The study also provided useful insights into key areas for further investigations.

Tailoring Heterogeneous Catalysts at the Atomic Level: In Memoriam, Prof. Chia-Kuang (Frank) Tsung

Professor Chia-Kuang (Frank) Tsung made his scientific impact primarily through the atomic-level design of nanoscale materials for application in heterogeneous catalysis. He approached this challenge from two directions: above and below the material surface. Below the surface, Prof. Tsung synthesized finely controlled nanoparticles, primarily of noble metals and metal oxides, tailoring their composition and surface structure for efficient catalysis. Above the surface, he was among the first to leverage the tunability and stability of metal-organic frameworks (MOFs) to improve heterogeneous, molecular, and biocatalysts. This article, written by his former students, seeks first to commemorate Prof. Tsung's scientific accomplishments in three parts: (1) rationally designing nanocrystal surfaces to promote catalytic activity; (2) encapsulating nanocrystals in MOFs to improve catalyst selectivity; and (3) tuning the host-guest interaction between MOFs and guest molecules to inhibit catalyst degradation. The subsequent discussion focuses on building on the foundation laid by Prof. Tsung and on his considerable influence on his former group members and collaborators, both inside and outside of the lab.

Synchronous Construction of the Hierarchical Pores and High Hydrophobicity of Stable Metal-Organic Frameworks through a Dual Coordination-Competitive Strategy

Hierarchical-pore construction and functionalities are critical to further extend the applications of some stable MOFs, such as water remediation, fuel purification, oil/water separation, and self-cleaning, which are rarely achieved simultaneously. Herein, we demonstrate a method of synchronously constructing high-hydrophobicity Zr-based metal-organic frameworks with hierarchical pores (HP-UiO-66) through a dual coordination-competitive strategy. The addition of alkanoic acids and Zn²⁺ ions as coordination-competitors could reduce the coordinative degree between the ligand and Zr⁴⁺ ions to effectively induce defect formation. The resulting unsaturated Zr⁴⁺ ions could fully combine with the existing alkanoic acid with a long chain to afford HP-UiO-66 with high-hydrophobicity characteristics. In addition, the particle size of pristine UiO-66 could be adjusted effectively from around 280 to 120 nm using different alkanoic acids when Zn²⁺ ions are not added. This study provided a simple way for effectively controlling the morphology and structure of UiO-66 at the same time. Moreover, this kind of high-hydrophobicity HP-UiO-66 showed potential applications in oil/water separation and selective adsorption of organic mixtures.

Laterally Engineering Lanthanide-MOFs Epitaxial Heterostructures for Spatially Resolved Planar 2D Photonic Barcoding

Metal-organic frameworks (MOFs) heterostructures with domain-controlled emissive colors have shown great potential for achieving high-throughput sensing, anti-counterfeit and information security. Here, a strategy based on steric-hindrance effect is proposed to construct lateral lanthanide-MOFs (Ln-MOFs) epitaxial heterostructures, where the channel-directed guest molecules are introduced to rebalance in-plane and out-of-plane growth rates of the Ln-MOFs microrods and eventually generate lateral MOF epitaxial heterostructures with controllable aspect ratios. A library of lateral Ln-MOFs heterostructures are acquired through a stepwise epitaxial growth procedure, from which rational modulation of each domain with specific lanthanide doping species allows for definition of photonic barcodes in a two-dimensional (2D) domain with remarkably enlarged encoding capacity. The results provide molecular-level insight into the use of modulators in governing crystallite morphology for spatially assembling multifunctional heterostructures.

Double-Walled Zn36@Zn104 Multicomponent Senary Metal-Organic Polyhedral Framework and Its Isoreticular Evolution

Metal-organic polyhedral frameworks are attractive in gas storage and separation due to large voids with windows that can serve as traps for guest molecules. Introducing multivariant/multicomponent functionalities in them are ways of improving performances for certain targets. The high compatibility of organic linkers can generate multivariant MOFs, but by far, the diversity of secondary building units (SBUs) in a single metal-organic framework is still limited (no more than two in most cases). Here we report a new double-walled Zn₃₆@Zn₁₀₄ metal-organic polyhedral framework (HHU-8) with five types of topologically distinct SBUs and its isoreticular evolution to the Zn₃₆@Zn₁₃₆ counterpart (HHU-8s). Both MOFs are the first to be constructed with such high numbers of topologically distinct SBUs as well as topologically distinct nodes, and their formation and evolution provide new insight into SBU's controllability.

Programmable Logic in Metal-Organic Frameworks for Catalysis

Metal-organic frameworks (MOFs) have emerged as one of the most widely investigated materials in catalysis mainly due to their excellent component tunability, high surface area, adjustable pore size, and uniform active sites. However, the overwhelming number of MOF materials and complex structures has brought difficulties for researchers to select and construct suitable MOF-based catalysts. Herein, a programmable design strategy is presented based on metal ions/clusters, organic ligands, modifiers, functional materials, and post-treatment modules, which can be used to design the components, structures, and morphologies of MOF catalysts for different reactions. By establishing the corresponding relationship between these modules and functions, researchers can accurately and efficiently construct heterometallic MOFs, chiral MOFs, conductive MOFs, hierarchically porous MOFs, defective MOFs, MOF composites, and MOF-derivative catalysts. Further, this programmable design approach can also be used to regulate the physical/chemical microenvironments of pristine MOFs, MOF composites, and MOF-derivative materials for heterogeneous catalysis, electrocatalysis, and photocatalysis. Finally, the challenging issues and opportunities for the future research of MOF-based catalysts are discussed. Overall, the modular design concept of this review can be applied as a potent tool for exploring the structure-activity relationships and accelerating the on-demand design of multicomponent catalysts.

Stable DNA Aptamer-Metal-Organic Framework as Horseradish Peroxidase Mimic for Ultra-Sensitive Detection of Carcinoembryonic Antigen in Serum

Carcinoembryonic antigen (CEA) is an important broad-spectrum tumor marker. For CEA detection, a novel type of metal-organic framework (MOF) was prepared by grafting CEA aptamer-incorporated DNA tetrahedral (TDN) nanostructures into PCN-222 (Fe)-based MOF (referred as CEAapt-TDN-MOF colloid nanorods). The synthesized CEAapt-TDN-MOF is a very stable detection system due to the vertex phosphorylated TDN structure at the interface, possessing a one-year shelf-life. Moreover, it exhibits a significant horseradish peroxidase mimicking activity due to the iron porphyrin ring, which leads to a colorimetric reaction upon binding toward antibody-captured CEA. Using this method, we successfully achieved the highly specific and ultra-sensitive detection of CEA with a limit of detection as low as 3.3 pg/mL. In addition, this method can detect and analyze the target proteins in clinical serum samples, effectively identify the difference between normal individuals and patients with colon cancer, and provide a new method for the clinical diagnosis of tumors, demonstrating a great application potential.

Evolution of water structures in metal-organic frameworks for improved atmospheric water harvesting

[Figure: see text].

Nanoscale Metal-Organic Frameworks: Recent developments in synthesis, modifications and bioimaging applications

Porous Metal-Organic Frameworks (MOFs) have emerged as eye-catching materials in recent years. They are widely used in numerous fields of chemistry thanks to their desirable properties. MOFs have a key role in the development of bioimaging platforms that are hopefully expected to effectually pave the way for accurate and selective detection and diagnosis of abnormalities. Recently, many types of MOFs have been employed for detection of RNA, DNA, enzyme activity and small-biomolecules, as well as for magnetic resonance imaging (MRI) and computed tomography (CT), which are valuable methods for clinical analysis. The optimal performance of the MOF in the bio-imaging field depends on the core structure, synthesis method and modifications processes. In this review, we have attempted to present crucial parameters for designing and achieving an efficient MOF as bioimaging platforms, and provide a roadmap for researchers in this field. Moreover, the influence of modifications/fractionalizations on MOFs performance has been thoroughly discussed and challenging problems have been extensively addressed. Consideration is mainly focused on the principal concepts and applications that have been achieved to modify and synthesize advanced MOFs for future applications.

Fine-Tuning the Micro-Environment to Optimize the Catalytic Activity of Enzymes Immobilized in Multivariate Metal-Organic Frameworks

The artificial engineering of an enzyme's structural conformation to enhance its activity is highly desired and challenging. Anisotropic reticular chemistry, best illustrated in the case of multivariate metal-organic frameworks (MTV-MOFs), provides a platform to modify a MOF's pore and inner-surface with functionality variations on frameworks to optimize the interior environment and to enhance the specifically targeted property. In this study, we altered the functionality and ratio of linkers in zeolitic imidazolate frameworks (ZIFs), a subclass of MOFs, with the MTV approach to demonstrate a strategy that allows us to optimize the activity of the encapsulated enzyme by continuously tuning the framework-enzyme interaction through the hydrophilicity change in the pores' microenvironment. To systematically study this interaction, we developed the component-adjustment-ternary plot (CAT) method to approach the optimal activity of the encapsulated enzyme BCL and revealed a nonlinear correlation, first incremental and then decremental, between the BCL activity and the hydrophilic linker' ratios in MTV-ZIF-8. These findings indicated there is a spatial arrangement of functional groups along the three-dimensional space across the ZIF-8 crystal with a unique sequence that could change the enzyme structure between closed-lid and open-lid conformations. These conformation changes were confirmed by FTIR spectra and fluorescence studies. The optimized BCL@ZIF-8 is not only thermally and chemically more stable than free BCL in solution, but also doubles the catalytic reactivity in the kinetic resolution reaction with 99% ee of the products.

Perovskite Quantum Dots Encapsulated in a Mesoporous Metal-Organic Framework as Synergistic Photocathode Materials

Metal halide perovskite quantum dots, with high light-absorption coefficients and tunable electronic properties, have been widely studied as optoelectronic materials, but their applications in photocatalysis are hindered by their insufficient stability because of the oxidation and agglomeration under light, heat, and atmospheric conditions. To address this challenge, herein, we encapsulated CsPbBr₃ nanocrystals into a stable iron-based metal-organic framework (MOF) with mesoporous cages (∼5.5 and 4.2 nm) via a sequential deposition route to obtain a perovskite-MOF composite material, CsPbBr₃@PCN-333(Fe), in which CsPbBr₃ nanocrystals were stabilized from aggregation or leaching by the confinement effect of MOF cages. The monodispersed CsPbBr₃ nanocrystals (4-5 nm) within the MOF lattice were directly observed by transmission electron microscopy and corresponding mapping analysis and further confirmed by powder X-ray diffraction, infrared spectroscopy, and N₂ adsorption characterizations. Density functional theory calculations further suggested a significant interfacial charge transfer from CsPbBr₃ quantum dots to PCN-333(Fe), which is ideal for photocatalysis. The CsPbBr₃@PCN-333(Fe) composite exhibited excellent and stable oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic activities in aprotic systems. Furthermore, CsPbBr₃@PCN-333(Fe) composite worked as the synergistic photocathode in the photoassisted Li-O₂ battery, where CsPbBr₃ and PCN-333(Fe) acted as optical antennas and ORR/OER catalytic sites, respectively. The CsPbBr₃@PCN-333(Fe) photocathode showed lower overpotential and better cycling stability compared to CsPbBr₃ nanocrystals or PCN-333(Fe), highlighting the synergy between CsPbBr₃ and PCN-333(Fe) in the composite.

Achieving High Performance Metal-Organic Framework Materials through Pore Engineering

Achieving high performance functional materials has been a long-term goal for scientists and engineers that can significantly promote science and technology development and thus benefit our society and human beings. As well-known porous materials, metal-organic frameworks (MOFs) are crystalline open frameworks made up of molecular building blocks linked by strong coordination bonds, affording pore space for storing and trapping guest molecules. In terms of porosity, MOFs outperform traditional porous materials including zeolites and activated carbon, showing exceptional porosity with internal surface area up to thousands of square meters per gram of sample and with periodic pore sizes ranging from sub-nanometer to nanometers. Numerous MOFs have been synthesized with potential applications ranging from storing gaseous fuels to separating intractable industrial gas mixtures, sensing physical and chemical stimulus, and transmitting protons for conduction. Compared to traditional porous materials, MOFs are distinguished for their exceptional capability for pore adjustment and interior modification through pore engineering, which have made them a preeminent platform for exploring functional materials with high performance.Rational combinations of rigid building units of different geometry and multibranched organic linkers have provided MOFs with diverse pore structures, ranging from spherical to cylindrical, slit, and tubular ones isolating or interconnecting in different directions, which can be optimized for high-capacity gas storage. Based on the isoreticular principle and building blocks approach in MOF chemistry, the pore adjustment of porous materials can be performed with exquisite precision, making them suitable to address industrially important gas separation. The large pore cavities in MOFs are readily available for encapsulation of different functional guest species, resulting in novel MOF composite materials with various functions.In this Account, we summarize our recent research progress on pore engineering to achieve high-performance MOF materials. We have been able to tune and optimize pore structures, immobilize specific functional sites, and incorporate guest species into target MOF materials for hydrogen storage, methane storage, light-hydrocarbon purification, and proton conduction, especially for various industrially important gas separations including acetylene removal and ethylene and propylene purification. By engineering the porosity and pore chemistry that endows MOFs with multiple functionalities, our research endeavors have brought about the customization of high-performance MOF materials for corresponding application scenarios.

Co-Heteroatom-Based MOFs for Bifunctional Electrocatalysts for Oxygen and Hydrogen Evolution Reactions

Herein, a Co(II) heteroatom metal-organic framework was successfully post-modified via unsaturated coordinated S precisely capturing Ni²⁺ on the surface of the porous structure. The newly pristine bimetallic MOFs have increasing active edge sites (Ni(II) and S), boosting electrocatalytic activity toward oxygen evolution reaction and hydrogen evolution reaction.

Simultaneous improvement to solubility and bioavailability of active natural compound isosteviol using cyclodextrin metal-organic frameworks

Cyclodextrin metal-organic framework (CD-MOF) as a highly porous supramolecular carrier could be one of the solutions to the insolubility of isosteviol (STV). The solubility of STV was lower than 20.00 ng/mL at pH 1.0 and pH 4.5, whilst its solubility increased to 20,074.30 ng/mL at pH 6.8 and 129.58 ng/mL in water with a significant pH-dependence. The in vitro release profiles of STV from STV@CD-MOF (0.5:1) were pH-independent in distinct pH media and closed to be thoroughly released but no such release profiles were observed for STV@CD-MOF (1:1) owing to nanoclusters formation. The bioavailability of STV@CD-MOF (1:1) in rats was 8.67-fold higher than that of STV, and was 1.32- and 1.27-fold higher than that of STV@CD and STV@CD-MOF (0.5:1). Our results indicated that the inclusion mechanism played a primary role when STV in CD-MOF was at a low loading ratio, while the increasement in bioavailability at a high loading ratio, which was attributed to the nanocluster mechanism. This was confirmed by molecular simulation. In conclusion, CD-MOF is a promising system for STV loading, overcoming the insolubility and to improve the bioavailability of this natural compound.

A Dynamic Chemical Clip in Supramolecular Framework for Sorting Alkylaromatic Isomers using Thermodynamic and Kinetic Preferences

Adsorptive chemical separation is at the forefront of future technologies, for use in chemical and petrochemical industries. In this process, a porous adsorbent selectively allows a single component from a mixture of three or more chemical components to be adsorbed or permeate. To separate the unsorted chemicals, a different adsorbent is needed. A unique adsorbent which can recognize and separate each of the chemicals from a mixture of three or more components is the necessity for the next generation porous materials. In this regard, we demonstrate a "dynamic chemical clip" in a supramolecular framework capable of thermodynamic and kinetics-based chemical separation. The dynamic space, featuring a strong preference for aromatic guests through π-π and C-H⋅⋅⋅π interactions and adaptability, can recognize the individual chemical isomers from mixtures and separate those based on thermodynamic and kinetic factors. The liquid-phase selectivity and separation of the aromatic isomers are possible by the adaptability of the "chemical clip" and here we elucidate the prime factors in a combinatorial approach involving crystallographic evidence and detailed computational studies.

Ultrathin porous amine-based solid adsorbent incorporated zeolitic imidazolate framework-8 membrane for gas separation

A novel gas separation approach is proposed in this work by combining an amine-based solid adsorbent with a zeolitic imidazolate framework-8 (ZIF-8) membrane. This was achieved by incorporating the amine-based solid adsorbent during the fabrication of the ZIF-8 membrane on a macroporous substrate. An amine-based solid adsorbent was prepared using porous ZIF-8-3-isocyanatopropyltrimethoxysilane (IPTMS) and N-[(3-trimethoxysilyl)propyl]diethylenetriamine (3N-APS) amine compounds. The as-prepared porous amine-based solid adsorbent (denoted as ZIF-8-IPTMS-3N-APS) possessed excellent adsorptive CO₂/N₂ and CO₂/CH₄ separation performances. As the adsorbent needs to be regenerated, this could indicate that the CO₂ adsorption separation process cannot be continuously operated. In this work, an amine-based solid adsorbent was applied during the preparation of the ZIF-8 membranes owing to the following reasons: (i) gas separation by the membrane can be operated continuously; (ii) the amino group provides a heterogeneous nucleation site for ZIF-8 to grow; and (iii) the reparation of surface defects on the macroporous substrate can be performed prior to the growth of the ZIF-8 membrane. Herein, the ZIF-8 membrane was successfully fabricated, and it possessed excellent CO₂/CH₄, CO₂/N₂, and H₂/CH₄ separation performances. The 0.6 μm ultrathin ZIF-8 membrane demonstrated a high CO₂ permeance of 4.75 × 10^-6 mol m^-2 s^-1 Pa^-1 at 35 °C and 0.1 MPa, and ideal CO₂/N₂ and CO₂/CH₄ selectivities of 4.67 and 6.02, respectively. Furthermore, at 35 °C and 0.1 MPa, the ideal H₂/CH₄ selectivity of the ZIF-8 membrane reached 31.2, and a significantly high H₂ permeance of 2.45 × 10^-5 mol m^-2 s^-1 Pa^-1.

Defect Engineering in Metal‒Organic Frameworks as Futuristic Options for Purification of Pollutants in an Aqueous Environment

Clean water scarcity is becoming an increasingly important worldwide issue. The water treatment industry is demanding the development of novel effective materials. Defect engineering in nanoparticles is among the most revolutionary of technologies. Because of their high surface area, structural diversity, and tailorable ability, Metal‒Organic Frameworks (MOFs) can be used for a variety of purposes including separation, storage, sensing, drug delivery, and many other issues. The application in wastewater treatment associated with water stable MOF‒based materials has been an emerging research topic in recent decades. Defect engineering is a sophisticated technique used to manufacture defects and to change the geometric framework of target compounds. Since MOFs have a series of designable structures and active sites, tailoring properties in MOFs by defect engineering is a novel concept. Defect engineering can excavate hidden active sites in MOFs, which can lead to better performance in many fields. Therefore, this technology will open new opportunities in water purification processes. However, there has been little effort to comprehensively discuss this topic. In this review, we provide an overview of the development of defect engineered MOFs for water purification processes. Furthermore, we discuss the potential applications of defect engineered materials.

Hydrogen Evolving Activity of Dithiolene-Based Metal-Organic Frameworks with Mixed Cobalt and Iron Centers

Electrocatalytic systems based on metal-organic frameworks (MOFs) have attracted great attention due to their potential application in commercially viable renewable energy-converting devices. We have recently shown that the cobalt 2,3,6,7,10,11-triphenylenehexathiolate (CoTHT) framework can catalyze the hydrogen evolution reaction (HER) in fully aqueous media with Tafel slopes as low as 71 mV/dec and near-unity Faradaic efficiency (FE). Taking advantage of the high synthetic tunability of MOFs, here, we synthesize a series of iron and mixed iron/cobalt THT-based MOFs. The incorporation of the iron and cobalt dithiolene moieties is verified by various spectroscopic techniques, and the integrity of the crystalline structure is maintained regardless of the stoichiometries of the two metals. The hydrogen evolving activity of the materials was explored in pH 1.3 aqueous electrolyte solutions. Unlike CoTHT, the FeTHT framework exhibits minimal activity due to a late catalytic onset [-0.440 V versus reversible hydrogen electrode (RHE)] and a large Tafel slope (210 mV/dec). The performance of the mixed-metal MOFs is adversely affected by the incorporation of Fe, where increasing Fe content results in MOFs with lower HER activity and diminished long-term stability and FE for H₂ production. It is proposed that the FeTHT domains undergo alternative Faradaic processes under catalytic conditions, which alter its local structure and electrochemical behavior, eventually resulting in a material with diminished HER performance.

Construction of Stable Helical Metal-Organic Frameworks with a Conformationally Rigid "Concave Ligand"

A helical metal-organic framework was prepared by using a conformationally rigid tetratopic benzoic acid ligand with binding units pointing toward each other (concave ligand). To avoid the obvious intramolecular interactions between binding units, matching spacing groups were applied to introduce atropic repulsion, thereby allowing the formation of extended frameworks for the first time. With this new ligand design, a helical-shaped MOF with significantly improved air and moisture stability was successfully prepared, thus providing a new strategy for ligand design toward porous material constructions.