Postsynthetic Modification: An Enabling Technology for the Advancement of Metal-Organic Frameworks

Translocation and Confinement of Tetraamines in Adaptable Microporous Cavities

Metal-Organic Frameworks can be grafted with amines by coordination to metal vacancies to create amine-appended solid adsorbents, which are being considered as an alternative to using aqueous amine solutions for CO2 capture. In this study, we propose an alternative mechanism that does not rely on the use of neutral metal vacancies as binding sites but is enabled by the structural adaptability of heterobimetallic Ti2Ca2 clusters. The combination of hard (Ti4+) and soft (Ca2+) metal centers in the inorganic nodes of the framework enables MUV-10 to adapt its pore windows to the presence of triethylenetetramine molecules. This dynamic cluster response facilitates the translocation and binding of tetraamine inside the microporous cavities to enable the formation of bis-coordinate adducts that are stable in water. The extension of this grafting concept from MUV-10 to larger cavities not restrictive to CO2 diffusion will complement other strategies available for the design of molecular sorbents for decarbonization applications.

Biphenyl tetracarboxylic acid-based metal-organic frameworks: a case of topology-dependent thermal expansion

The large inherent flexibility and highly modular nature of metal-organic frameworks (MOFs) make them ideal candidates for the study of negative thermal expansion (NTE). Among diverse organic ligands, the biphenyl unit, which can unrestrictedly rotate along its C-C single bond, can largely enhance the structural flexibility. Herein, we explored the thermal expansion behaviors of four indium biphenyl tetracarboxylates (BPTCs). Owing to the different dihedral angles of BPTC ligands and coordination mode of In3+, they show distinct topologies: InOF-1 (nti), InOF-2 (unc), InOF-12 (pts) and InOF-13 (nou). Intriguingly, it is found that the thermal expansion is highly dependent on the specific topology. The MOFs featuring mononuclear nodes show normal positive thermal expansion (PTE), and the magnitudes of coefficients follow the trend of InOF-2 < InOF-12 < InOF-13, inversely related to averaged molecular volumes. In contrast, the InOF-1, composed of a 1D chain of corner-shared InO6 octahedrons, shows pronounced NTE. Detailed high-resolution synchrotron powder X-ray diffraction and lattice dynamic analyses shed light on the fact that NTE in the InOF-1 is a synergy effect of the spring-like distortion of the inorganic 1D helical chain and twisting of the BPTC ligands. The present work shows how the topological arrangement of building blocks governs the thermal expansion behaviors.

Recent advances in manipulating strategies of NH2-functionalized metallic organic frameworks-based heterojunction photocatalysts for the sustainable mitigation of various pollutants

NH2-functionalized metal-organic frameworks (NH2-functionalized MOFs) can abate organic pollutants, predominantly favored by their chemical, mechanical, and thermal stabilities. The present review stated the chemistry of identifying NH2-functionalization and its role in enhancing the properties of bare MOFs. The integration of the amine group bestows several advantages: 1.) enabling band structure modification, 2.) establishing strong metal-NH2 bonds, 3.) preserving MOF structures from reactive oxygen species, and 4.) shielding MOF structures against pH alterations. Consequently, the NH2-functionalized MOFs are promising materials for the photodegradation of organic contaminants. The following section illustrates the two approaches (pre-synthetic and post-synthetic) for NH2-functionalized MOFs. Nevertheless, specific intrinsic limitations, entailing a high recombination rate of charge carriers and inadequate optical adsorption, restrain the applicability of NH2-functionalized MOFs. Accordingly, the succeeding segment presents strategies to elevate the photocatalytic activities of NH2-functionalized MOFs via heterojunction fabrication. The importance of the NH2-functionalized MOFs-based heterojunction has been evaluated in terms of the effect on the enhancement of charge separation, optical adsorption, and redox ability of charge carriers. Subsequently, the potential application for organic pollutant degradation via NH2-functionalized MOFs-based heterojunctions has been scrutinized, wherein the organic pollutants. Eventually, the review concluded with challenges and potential opportunities in engaging and burgeoning domains of the NH2-functionalized MOFs-based heterojunctions.

Metal-Organic Framework-Supported Mono Bipyridyl-Iron Hydroxyl Catalyst for Selective Benzene Hydroxylation into Phenol

Direct hydroxylation of benzene to phenol is more appealing in the industry for the economic and environmentally friendly phenol synthesis than the conventional cumene process. We have developed a UiO-metal-organic framework (MOF)-supported mono bipyridyl-Iron(II) hydroxyl catalyst [bpy-UiO-Fe(OH)2] for the selective benzene hydroxylation into phenol using H2O2 as the oxidant. The heterogeneous bpy-UiO-Fe(OH)2 catalyst showed high activity and remarkable phenol selectivity of 99%, giving the phenol mass-specific activity up to 1261 mmolPhOHgFe-1 h-1 at 60 °C. Bpy-UiO-Fe(OH)2 is significantly more active and selective than its homogeneous counterpart, bipyridine-Fe(OH)2. This enhanced catalytic activity of bpy-UiO-Fe(OH)2 over its homogeneous control is attributed to the active site isolation of the bpy-Fe(OH)2 moiety by the solid MOF that prevents intermolecular decomposition. Moreover, the exceptional selectivity of bpy-UiO-Fe(OH)2 in benzene to phenol conversion is originated via shape-selective catalysis, where the confined reaction space within the porous UiO-MOF prevents the formation of larger overoxidized products such as hydroquinone or benzoquinone, leading to the formation of only smaller-sized phenol after monohydroxylation of benzene. Spectroscopic and controlled experiments and theoretical calculations elucidated the reaction pathway, in which the in situ generated •OH radical mediated by bpy-UiO-FeII(OH)2 is the key species for benzene hydroxylation. This work underscores the significance of MOF-supported earth-abundant metal catalysts for sustainable production of fine chemicals.

Selective monoborylation of methane by metal-organic framework confined mononuclear pyridylimine-iridium(I) hydride

Chemoselective monoborylation of methane in high yield is a grand challenge. We have developed a metal-organic framework confined pyridylimine-iridium hydride catalyst, which is efficient in methane C-H borylation using bis(pinacolato)diboron to afford methyl boronic acid pinacol ester in 98% GC-yield at 130 °C with a TON of 196. Mechanistic investigation suggests the oxidative addition of methane to IrIII(Bpin)2(H) species to form IrV(Bpin)2(CH3)(H)2 as the turnover limiting step.

Metalation of metal-organic frameworks: fundamentals and applications

Metalation of metal-organic frameworks (MOFs) has been developed as a prominent strategy for materials functionalization for pore chemistry modulation and property optimization. By introducing exotic metal ions/complexes/nanoparticles onto/into the parent framework, many metallized MOFs have exhibited significantly improved performance in a wide range of applications. In this review, we focus on the research progress in the metalation of metal-organic frameworks during the last five years, spanning the design principles, synthetic strategies, and potential applications. Based on the crystal engineering principles, a minor change in the MOF composition through metalation would lead to leveraged variation of properties. This review starts from the general strategies established for the incorporation of metal species within MOFs, followed by the design principles to graft the desired functionality while maintaining the porosity of frameworks. Facile metalation has contributed a great number of bespoke materials with excellent performance, and we summarize their applications in gas adsorption and separation, heterogeneous catalysis, detection and sensing, and energy storage and conversion. The underlying mechanisms are also investigated by state-of-the-art techniques and analyzed for gaining insight into the structure-property relationships, which would in turn facilitate the further development of design principles. Finally, the current challenges and opportunities in MOF metalation have been discussed, and the promising future directions for customizing the next-generation advanced materials have been outlined as well.

Fe-based MOFs as promising adsorbents and photocatalysts for re-use water contained arsenic: Strategies and challenges

Arsenic (As) contaminated water, especially groundwater reservoirs, is a major issue worldwide owing to its hazardous consequences on human health and the global environment issues. Also, irrigating agricultural fields with As-contaminated water not only produces an accumulation of As in the soil but also compromises food safety due to As entering into agricultural products. Hence, there is an urgent need to develop an efficient method for As removal in water. Fe-based MOFs have attained special attention due to their low toxicity, high water stability, better physical and chemical properties, and high abundance of iron. The arsenic species removal by Fe-MOF follows the adsorption and oxidation mechanism where As (III) converts into As (V). Moreover, the adsorption mechanism is facilitated by electrostatic interactions, H-bonding, acid-base interaction, hydrophobic interactions, van der Waals forces, π-π stacking interactions, and coordinative bindings responsible for Fe-O-As bond generation. This review thoroughly recapitulates and analyses recent advancements in the facile synthesis and potential application of Fe-based MOF adsorbents for the elimination of As ions. The most commonly employed hydro/solvothermal, ultrasonic, microwave-assisted, mechanochemical, and electrochemical synthesis for Fe-MOF has been discussed along with their adsorptive and oxidative mechanisms involved in arsenic removal. The effects of factors like pH and coexisting ions have also been discussed. Lastly, the article also proposed the prospects for developing the application of Fe-based MOF in treating As-contaminated water.

Enhanced adsorption and removal of Cd(II) from aqueous solution by amino-functionalized ZIF-8

Zeolite imidazolate framework-8 (ZIF-8), which is a special subgroup of metal-organic frameworks (MOFs), was synthesized and modified by ethylenediamine (ZIF-8-EDA) to prepare an efficient adsorbent for the high sorption of Cd2+ ions from solution. The synthesized and modified ZIF-8 (ZIF-8-EDA) were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, Brunauer-Emmett-Teller (BET), field emission scanning electron microscopy (FE-SEM) with energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM) analysis. The optimum conditions for dosage of adsorbent, initial ion concentration, pH, and contact time were 0.05 g/l, 50 mg/l, 6, and 60 min, respectively, for cadmium ion sorption from aqueous solutions with a removal efficiency of 89.7% for ZIF-8 and 93.5% for ZIF-8-EDA. Adsorption kinetics and equilibrium data were analyzed using the Langmuir and Freundlich equations. The Langmuir model fitted the equilibrium data better than the Freundlich model. According to the Langmuir equation, the maximum uptake for the cadmium ions was 294.11(mg/g). The calculated thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicated that the adsorption process was feasible, spontaneous, and endothermic at 20-50 °C. Based on the results, the amino functionalized ZIF-8 had improved adsorption performance due to the replacing of the starting linker with organic ligands that had effective functional groups, leading to chemical coordination due to the interaction of metal ions with the non-bonding pair of electrons on the N atoms of the amino functional group. The selectivity toward metal ion adsorption by ZIF-8-EDA was Cd2+ > Pb2+ > Ni2+‏.

Cobalt metal replaces Co-ZIF-8 mesoporous material for effective adsorption of arsenic from wastewater

The high cost and low adsorption capacity of primary metal-organic frameworks (ZIF-8) limit their application in heavy metal removal. In this paper, Co/Zn bimetallic MOF materials were synthesized with excellent adsorption performance for As5+. The adsorption reached equilibrium after 180 min and the maximum adsorption was 250.088 mg/g. In addition, Co-ZIF-8 showed strong selective adsorption of As5+. The adsorption process model of Co-ZIF-8 fits well with the pseudo-second-order kinetic model (R2=0.997) and Langmuir isotherm model (R2=0.994), and it is demonstrated that the adsorption behavior of the adsorbent is a single layer of chemical adsorption. In addition, when the adsorbent enters the arsenic-containing solution, the surface of Co-ZIF-8 is hydrolyzed to produce a large number of Co-OH active sites, and As5+ arrives at the surface of Co-ZIF-8 by electrostatic adsorption and combines with the active sites to generate the arsenic-containing complex As-O-Co. After four cycles, Co-ZIF-8 showed 80% adsorption of As5+. This study not only provides a new method to capture As5+ in water by preparing MOF with partial replacement of the central metal, but also has great significance for the harmless disposal of polluted water.

Scaling-Up Microwave-Assisted Synthesis of Highly Defective Pd@UiO-66-NH2 Catalysts for Selective Olefin Hydrogenation under Ambient Conditions

The need to develop green and cost-effective industrial catalytic processes has led to growing interest in preparing more robust, efficient, and selective heterogeneous catalysts at a large scale. In this regard, microwave-assisted synthesis is a fast method for fabricating heterogeneous catalysts (including metal oxides, zeolites, metal-organic frameworks, and supported metal nanoparticles) with enhanced catalytic properties, enabling synthesis scale-up. Herein, the synthesis of nanosized UiO-66-NH2 was optimized via a microwave-assisted hydrothermal method to obtain defective matrices essential for the stabilization of metal nanoparticles, promoting catalytically active sites for hydrogenation reactions (760 kg·m-3·day-1 space time yield, STY). Then, this protocol was scaled up in a multimodal microwave reactor, reaching 86% yield (ca. 1 g, 1450 kg·m-3·day-1 STY) in only 30 min. Afterward, Pd nanoparticles were formed in situ decorating the nanoMOF by an effective and fast microwave-assisted hydrothermal method, resulting in the formation of Pd@UiO-66-NH2 composites. Both the localization and oxidation states of Pd nanoparticles (NPs) in the MOF were achieved using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray photoelectron spectroscopy (XPS), respectively. The optimal composite, loaded with 1.7 wt % Pd, exhibited an extraordinary catalytic activity (>95% yield, 100% selectivity) under mild conditions (1 bar H2, 25 °C, 1 h reaction time), not only in the selective hydrogenation of a variety of single alkenes (1-hexene, 1-octene, 1-tridecene, cyclohexene, and tetraphenyl ethylene) but also in the conversion of a complex mixture of alkenes (i.e., 1-hexene, 1-tridecene, and anethole). The results showed a powerful interaction and synergy between the active phase (Pd NPs) and the catalytic porous scaffold (UiO-66-NH2), which are essential for the selectivity and recyclability.

Chiral Metal-Organic Frameworks with Spectroscopic Methods: Towards Chemical Sensor Devices

Chiral Metal-Organic Frameworks (CMOFs) are a rapidly growing field reflecting their potential as selective and sensitive chemical sensors for chiral analytes. The highly tuneable nature of CMOFs enables the size, shape, and non-covalent interactions to be optimised towards specific analytes to engender strong intermolecular interactions and sensing responses. While CMOFs as chiral chemical sensor devices have been explored with electrochemical methods including differential pulse voltammetry (DPV), bipolar and chemiresistive sensing techniques, the CMOFs as chiral chemical sensors using spectroscopic methods has received significantly less attention. This review examines the synthesis of CMOFs for chemical sensors with spectroscopic methods such as photoluminescence, circular dichroism, and solid-state nuclear magnetic resonance with a view towards their incorporation into chemical sensor devices. Future directions of the field are highlighted for the generation of functional devices.

Monitoring water harvesting in metal-organic frameworks, one water molecule at a time

Metal-organic frameworks (MOFs) have gained prominence as potential materials for atmospheric water harvesting, a vital solution for arid regions and areas experiencing severe water shortages. However, the molecular factors influencing the performance of MOFs in capturing water from the air remain elusive. Among all MOFs, Ni2X2BTDD (X = F, Cl, Br) stands out as a promising water harvester due to its ability to adsorb substantial amounts of water at low relative humidity (RH). Here, we use advanced molecular dynamics simulations carried out with the state-of-the-art MB-pol data-driven many-body potential to monitor water adsorption in the three Ni2X2BTDD variants as a function of RH. Our simulations reveal that the type of halide atom in the three Ni2X2BTDD frameworks significantly influences the corresponding molecular mechanisms of water adsorption: while water molecules form strong hydrogen bonds with the fluoride atoms in Ni2F2BTDD, they tend to form hydrogen bonds with the nitrogen atoms of the triazolate linkers in Ni2Cl2BTDD and Ni2Br2BTDD. Importantly, the large size of the bromide atoms reduces the void volume in the Ni2Br2BTDD pores, which enable water molecules to initiate an extended hydrogen-bond network at lower RH. These findings not only underscore the prospect for precisely tuning structural and chemical modifications of the frameworks to optimize their interaction with water, but also highlight the predictive power of simulations with the MB-pol data-driven many-body potential. By providing a realistic description of water under different thermodynamic conditions and environments, these simulations yield unique, molecular-level insights that can guide the design and optimization of energy-efficient water harvesting materials.

Selective Reduction of Nitro Compounds by Organosilanes Catalyzed by a Zirconium Metal-Organic Framework Supported Salicylaldimine-Cobalt(II) Complex

Reducing nitro compounds to amines is a fundamental reaction in producing valuable chemicals in industry. Herein, the synthesis and characterization of a zirconium metal-organic framework-supported salicylaldimine-cobalt(II) chloride (salim-UiO-CoCl) and its application in catalytic reduction of nitro compounds are reported. Salim-UiO-Co displayed excellent catalytic activity in chemoselective reduction of aromatic and aliphatic nitro compounds to the corresponding amines in the presence of phenylsilane as a reducing agent under mild reaction conditions. Salim-UiO-Co catalyzed nitro reduction had a broad substrate scope with excellent tolerance to diverse functional groups, including easily reducible ones such as aldehyde, keto, nitrile, and alkene. Salim-UiO-Co MOF catalyst could be recycled and reused at least 14 times without noticeable losing activity and selectivity. Density functional theory (DFT) studies along with spectroscopic analysis were employed to get into a comprehensive investigation of the reaction mechanism. This work underscores the significance of MOF-supported single-site base-metal catalysts for the sustainable and cost-effective synthesis of chemical feedstocks and fine chemicals.

The Promise and Potential of Metal-Organic Frameworks and Covalent Organic Frameworks in Vaccine Nanotechnology

The immune system's complexity and ongoing evolutionary struggle against deleterious pathogens underscore the value of vaccination technologies, which have been bolstering human immunity for over two centuries. Despite noteworthy advancements over these 200 years, three areas remain recalcitrant to improvement owing to the environmental instability of the biomolecules used in vaccines─the challenges of formulating them into controlled release systems, their need for constant refrigeration to avoid loss of efficacy, and the requirement that they be delivered via needle owing to gastrointestinal incompatibility. Nanotechnology, particularly metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), has emerged as a promising avenue for confronting these challenges, presenting a new frontier in vaccine development. Although these materials have been widely explored in the context of drug delivery, imaging, and cancer immunotherapy, their role in immunology and vaccine-related applications is a recent yet rapidly developing field. This review seeks to elucidate the prospective use of MOFs and COFs for biomaterial stabilization, eliminating the necessity for cold chains, enhancing antigen potency as adjuvants, and potentializing needle-free delivery of vaccines. It provides an expansive and critical viewpoint on this rapidly evolving field of research and emphasizes the vital contribution of chemists in driving further advancements.

Reversible Postsynthetic Modification in a Metal-Organic Framework

Postsynthetic modification (PSM) of metal-organic frameworks (MOFs) provides access to functional materials and advanced porous solid engineering. Herein, we report the reversible PSM of a multivariate isoreticular MOF by applying dynamic furan-maleimide Diels-Alder (DA) chemistry. The key step involves incorporating a furan group into the MOF via "click" PSM, which can then undergo repeated cycles of modification and de-modification with maleimides. The structural integrity, crystallinity, and porosity of the furan-appended MOF remained intact even after three consecutive PSM/de-modification cycles using three different functionalized maleimides.

Pore-Networked Soft Materials Based on Metal-Organic Polyhedra

ConspectusThe last two decades have witnessed a tremendous development of crystalline microporous adsorbents in a wide range of applications including molecular adsorption, storage and separation, purification, as well as catalysis. The main players as porous materials that have contributed to the developments are extended molecular frameworks (e.g., metal-organic frameworks, MOFs; covalent-organic frameworks, COFs) or discrete porous molecules (e.g., metal-organic cages, MOCs; porous organic cages, POCs) thanks to the high degrees of freedom in their structural designability and tunability. To overcome the processability issue originating from their powder forms after synthesis, one main strategy is to hybridize the microporous adsorbents as pore-containing fillers with solvents or polymers as processable matrices to produce porous soft materials, such as porous liquids, gels/aerogels, and mixed-matrix membranes, depending on the form of matrix used. Nevertheless, the fabrication of "ideal" hybrid materials relies on the homogeneous distribution of the pore-containing fillers within the matrices. It is still challenging to find a versatile way to solve the aggregation issues of fillers and their insufficient interaction with the matrices, which are concerned with inhibiting the translation of the distinctive properties of microporous adsorbents into the obtained hybrid soft materials.Herein, we describe a new bottom-up approach for the fabrication of "pore-networked soft materials" based on the concept of directly interconnecting the pore-containing fillers into a continuous pore network within the matrices. The advantages of the pore-networking strategy lie in two main aspects: (i) the elimination of the need to struggle with the aggregation issue of fillers due to their overall interconnection throughout the matrices; (ii) the generation of continuous pore networks that guarantee the efficient molecular mass transfer in the materials. In this Account, we summarize our state-of-the-art progress of pore-networked soft materials based on the use of MOCs, alternatively called metal-organic polyhedra (MOPs) herein, as pore units for the pore network construction. The good solubility of MOPs in organic solvents allows them to be feasibly processed in solution, wherein the coordination of MOPs with organic linkers leads to the formation of linked MOP gels featuring not only intrinsic MOP cavities but also tunable extrinsic porosities generated between linked MOPs through the control of MOP/linker structures and network connectivity. Furthermore, the matrix of the linked MOP network, here referred to as the continuous phase with respect to the entire porous MOP network, is not limited to the solvents. We anticipate that the implementation of air, liquids, and polymers as the matrices could result in different forms of pore-networked soft materials like aerogels, foams, gels, monoliths, and membranes. For instance, we demonstrate the fabrication of linked MOP aerogel and permanently porous gel with their potential applications on selective CO2 photoreduction and gas sorption, respectively. We believe that the pore-network strategies will advance the development of porous soft materials featuring unique advantages and properties beyond the current hybrid systems.

Advances and Applications of Metal-Organic Frameworks (MOFs) in Emerging Technologies: A Comprehensive Review

Metal-organic frameworks (MOFs) that are the wonder material of the 21st century consist of metal ions/clusters coordinated to organic ligands to form one- or more-dimensional porous structures with unprecedented chemical and structural tunability, exceptional thermal stability, ultrahigh porosity, and a large surface area, making them an ideal candidate for numerous potential applications. In this work, the recent progress in the design and synthetic approaches of MOFs and explore their potential applications in the fields of gas storage and separation, catalysis, magnetism, drug delivery, chemical/biosensing, supercapacitors, rechargeable batteries and self-powered wearable sensors based on piezoelectric and triboelectric nanogenerators are summarized. Lastly, this work identifies present challenges and outlines future opportunities in this field, which can provide valuable references.

Aptamer-functionalized MOFs and AI-driven strategies for early cancer diagnosis and therapeutics

Metal-Organic Frameworks (MOFs) have exceptional inherent properties that make them highly suitable for diverse applications, such as catalysis, storage, optics, chemo sensing, and biomedical science and technology. Over the past decades, researchers have utilized various techniques, including solvothermal, hydrothermal, mechanochemical, electrochemical, and ultrasonic, to synthesize MOFs with tailored properties. Post-synthetic modification of linkers, nodal components, and crystallite domain size and morphology can functionalize MOFs to improve their aptamer applications. Advancements in AI and machine learning led to the development of nonporous MOFs and nanoscale MOFs for medical purposes. MOFs have exhibited promise in cancer therapy, with the successful accumulation of a photosensitizer in cancer cells representing a significant breakthrough. This perspective is focused on MOFs' use as advanced materials and systems for cancer therapy, exploring the challenging aspects and promising features of MOF-based cancer diagnosis and treatment. The paper concludes by emphasizing the potential of MOFs as a transformative technology for cancer treatment and diagnosis.

Maximizing the Potential of Electrically Conductive MOFs

ConspectusElectrically conductive metal-organic frameworks (EC-MOFs) have emerged as a compelling class of materials, drawing increasing attention due to their unique properties facilitating charge transport within porous structures. The synergy between electrical conductivity and porosity has opened a wide range of applications, including electrocatalysis, energy storage, chemiresistive sensing, and electronic devices that have been underexplored for their insulating counterparts. Despite these promising prospects, a prevalent challenge arises from the predominant adoption of two-dimensional (2D) structures by most EC-MOFs. These 2D frameworks often show modest surface areas and short interlayer distances, hindering molecular accessibility, which deviates from the inherent characteristics of conventional MOFs. Furthermore, the quest for efficient charge transport imposes design constraints, leading to a restricted selection of functional building blocks. Additionally, there is a lack of established functionalization methods within EC-MOFs, limiting their functional diversity. Thus, these challenges have impeded EC-MOFs from reaching their full potential.In this Account, we summarize and discuss our group's efforts aimed at enhancing molecular accessibility and deploying the functional diversity of EC-MOFs. Our focus on enhancing molecular accessibility involves several strategies. First, we employed macrocyclic ligands with intrinsic pockets as the building blocks for EC-MOFs. The integrated intrinsic pockets in the frameworks supplement surface areas and additional pores to enhance molecular accessibility. The resulting macrocyclic ligand-based EC-MOFs exhibit exceptionally high surface areas and confer advantages in electrochemical performances. Second, our efforts extend to addressing the structural limitations, frequently associated with EC-MOFs' 2D structures. Through the pillar insertion strategy, we transformed a 2D EC-MOF platform into a three-dimensional (3D) structure, thereby achieving higher porosity and enhanced molecular accessibility. In pursuing functional diversity, we have delved into molecular-level tuning of EC-MOF building blocks. We demonstrated that electron-rich alkyne-based pockets in the macrocyclic ligands can host transition metals and alkali ions, enabling ion selectivity and showcasing diverse use of EC-MOFs. We utilized a postsynthetic approach to further functionalize metal nodes on the molecular level within an EC-MOF framework, introducing a proton-conducting pathway while preserving its electrical conductivity.We aspire for this Account to provide practical insights and strategies to surmount structural and functional diversity limitations in the realm of EC-MOFs. By integrating enhanced molecular accessibility and diverse functionality, our endeavor to propel the utility of these materials will inspire further rational development for future EC-MOFs and unlock their full potential.

Cd-MOF and Its Ln3+-Post Modification Products: Regulation of Luminescence Properties and Improved Detection of Uric Acid, Quinine, and Quinidine

One 3D Cd-MOF, namely, {[(HDMA)2][Cd3(L)2]·5H2O·2DMF}n (LCU-124, LCU indicates Liaocheng University), was synthesized from an ether-containing ligand 1,3-bis(3,5-dicarboxylphenoxy)benzene (H4L). Its Ln3+-postmodified samples, Eu3+@LCU-124 and Tb3+@LCU-124, were obtained through cation exchange of dimethylamine cation (HDMA) with Eu3+ and Tb3+. The successful entry of rare earth into LCU-124 by cation exchange modification was verified by IR, XRD, XPS, EDS mapping, and luminescence spectra. The proportion of Eu3+/Tb3+ was adjusted during the modification process, leading to fluorescent materials with different emissions. Luminescence measurements indicated that these complexes exhibited interesting multiresponsive sensing activities toward biomarkers urine acid (UA), quinine (QN), and quinidine (QND). First, LCU-124 has a pronounced quenching effect toward UA with the detection limit of 31.01 μM. After modification, the visualization of the detection was improved significantly and the detection limit of Eu3+@LCU-124 was reduced to 0.868 μM. Second, when QN and QND were present in the suspensions of Eu3+@LCU-124 and Tb3+@LCU-124, strong blue light emission peaks occurred, while the characteristic emission of Eu3+/Tb3+ decreased, forming ratiometric fluorescent sensors with the detection limit in the range of 0.199-9.49 μM. The fluorescent probes have high selectivity, excellent sensitivity recycling, and fast response time (less than 1 min). Besides, a simple logic gate circuit and a range of luminescent mixed matrix membranes were designed to provide simple and fast detection of above biomarkers. Our work indicated that modification of Eu3+/Tb3+ could improve the detection ability significantly.

Impact of Ligand Substitution and Metal Node Exchange in the Electronic Properties of Scandium Terephthalate Frameworks

The search for sustainable alternatives to established materials is a sensitive topic in materials science. Due to their unique structural and physical characteristics, the composition of metal-organic frameworks (MOFs) can be tuned by the exchange of metal nodes and the functionalization of organic ligands, giving rise to a large configurational space. Considering the case of scandium terephthalate MOFs and adopting an automatized computational framework based on density-functional theory, we explore the impact of metal substitution with the earth-abundant isoelectronic elements Al and Y, and ligand functionalization of varying electronegativity. We find that structural properties are strongly impacted by metal ion substitution and only moderately by ligand functionalization. In contrast, the energetic stability, the charge density distribution, and the electronic properties, including the size of the band gap, are primarily affected by the termination of the linker molecules. Functional groups such as OH and NH2 lead to particularly stable structures thanks to the formation of hydrogen bonds and affect the electronic structure of the MOFs by introducing midgap states.

Progress and Advances in Porous Silica-based Scaffolds for Enhanced Solid-state Hydrogen Storage: A Systematic Literature Review

Hydrogen plays a crucial role in the future energy landscape owing to its high energy density. However, finding an ideal storage material is the key challenge to the success of the hydrogen economy. Various solid-state hydrogen storage materials, such as metal hydrides, have been developed to realize safe, effective, and compact hydrogen storage. However, low kinetics and thermodynamic stability lead to a high working temperature and a low hydrogen sorption rate of the metal hydrides. Using scaffolds made from porous materials like silica to confine the metal hydrides is necessary for better and improved hydrogen storage. Therefore, this article reviews porous silica-based scaffolds as an ideal material for improved hydrogen storage. The outcome showed that confining the metal hydrides using scaffolds based on porous silica significantly increases their storage capacities. It was also found that the structural modifications of the silica-based scaffold into a hollow structure further improved the storage capacity and increased the affinity and confinement ability of the metal hydrides, which prevents the agglomeration of metal particles during the adsorption/desorption process. Hence, the structural modifications of the silica material into a fibrous and hollow material are recommended to be crucial for further enhancing the metal hydride storage capacity.

Isoreticular Metal-Organic Frameworks Confined Mononuclear Ru-Hydrides Enable Highly Efficient Shape-Selective Hydrogenolysis of Polyolefins

Upcycling nonbiodegradable plastics such as polyolefins is paramount due to their ever-increasing demand and landfills after usage. Catalytic hydrogenolysis is highly appealing to convert polyolefins into targeted value-added products under mild reaction conditions compared with other methods, such as high-temperature incineration and pyrolysis. We have developed three isoreticular zirconium UiO-metal-organic frameworks (UiO-MOFs) node-supported ruthenium dihydrides (UiO-RuH2), which are efficient heterogeneous catalysts for hydrogenolysis of polyethylene at 200 °C, affording liquid hydrocarbons with a narrow distribution and excellent selectivity via shape-selective catalysis. UiO-66-RuH2 catalyzed hydrogenolysis of single-use low-density polyethylene (LDPE) produced a C12 centered narrow bell-shaped distribution of C8-C16 alkanes in >80% yield and 90% selectivity in the liquid phase. By tuning the pore sizes of the isoreticular UiO-RuH2 MOF catalysts, the distribution of the products could be systematically altered, affording different fuel-grade liquid hydrocarbons from LDPE in high yields. Our spectroscopic and theoretical studies and control experiments reveal that UiO-RuH2 catalysts enable highly efficient upcycling of plastic wastes under mild conditions owing to their unique combination of coordinatively unsaturated single-site Ru-active sites, uniform and tunable pores, well-defined porous structure, and superior stability. The kinetics and theoretical calculations also identify the C-C bond scission involving β-alkyl transfer as the turnover-limiting step.

Modular Gating of Ion Transport by Postsynthetic Charge Transfer Complexation in a Metal-Organic Framework

Nature's design of biological ion channels that demonstrates efficient gating and selectivity brings to light a very promising model to mimic and design for achieving selective and tunable ion transport. Functionalized nanopores that permit modulation of the pore wall charges are a compelling approach to gain control over the ion transport mechanism through the pores. This makes way for employing a noncovalent supramolecular approach for attaining charge reversal of the MOF pore walls using donor-acceptor pairs that can demonstrate strong charge transfer interactions. Herein, robust Zr4+-based mesoporous MOF-808 was postsynthetically modified into an anion-selective nanochannel (MOF-808-MV) by modification with dicationic viologen-based motifs. Charge modulation and even reversal of the MOF-808-MV pore walls were then explored taking advantage of strong charge transfer interactions between the grafted dicationic viologen acceptor moieties and anionic, π-electron-rich donor guest molecules such as pyranine (PYR) and tetrathiafulvalene tetrabenzoic acid (TTF-TA). Tunability of the MOF pore charge from positive to neutral to negative was achieved via simple methodologies such as diffusion control in case of guest molecule like PYR and by pH modulation for pH-responsive guest like TTF-TA. This results in a concomitant modulation in the selectivity of the nanochannel, rendering it from anion-selective to ambipolar to cation-selective. Furthermore, as a real-time application of this ion channel, Na+ ion conductivity (σ = 3.5 × 10-5 S cm-1) was studied at ambient temperature.

Utility of all-pyrazole heteroscorpionates in f-element chemistry

Since their discovery in 1966, scorpionate ligands have been utilized to make coordination compounds for a variety of applications such as: studying organometallic reactions, biomimetic complexes, light-emitting materials and single-ion magnets. The recent development of a solvent-free pyrazole substitution chemistry has yielded the quantitative synthesis of asymmetrically functionalized all-pyrazole heteroscorpionate ligands. In this frontier article, we highlight the utility of all-pyrazole heteroscorpionates, specifically, nitro-trispyrazolylborates, in f-element chemistry. They offer great versatility in coordinating ability, donor strength, steric bulk and even optical charge transfer properties, all of which can be used to tune the properties of resultant complexes with metal ions. We show how they can impart structural diversity, sensitize Ln3+ luminescence and engender magnetic anisotropy and slow magnetic relaxation in the ion they coordinate. Additionally, we comment on the future of functionalized trispyrazolyl scorpionates, which includes enabling post-synthetic modifications of f-element complexes and becoming a platform to study the electronic properties of low oxidation state actinides.

Unlocking Solid-State Organometallic Photochemistry with Optically Transparent, Porous Salt Thin Films

Synthetic porous materials continue to garner attention as platforms for solid-state chemistry and as designer heterogeneous catalysts. Applications in photochemistry and photocatalysis, however, are plagued by poor light harvesting efficiency due to light scattering resulting from sample microcrystallinity and poor optical penetration that arises from inner filter effects. Here we demonstrate the layer-by-layer growth of optically transparent, photochemically active thin films of porous salts. Films are grown by sequential deposition of cationic Zr-based porous coordination cages and anionic Mn porphyrins. Photolysis facilitates the efficient reduction of Mn(III) sites to Mn(II) sites, which can be observed in real-time by transmission UV-vis spectroscopy. Film porosity enables substrate access to the Mn(II) sites and facilitates reversible O2 activation in the solid state. These results establish optically transparent, porous salt thin films as versatile platforms for solid-state photochemistry and in operando spectroscopy.

Multivariate metal-organic frameworks generated through post-synthetic modification: impact and future directions

Reticular chemistry has proven to be invaluable over time, thanks to the structural versatility, and tailored porosity observed in structures like metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and metal-organic polyhedra (MOPs). Despite the wide array of ligands and metals available for synthesizing MOFs, they are still somewhat constrained by the reliance on de novo conditions and the focus on generating MOFs with single ligand and metal. To surpass these limitations, researchers have established strategies to generate multivariate (MTV) MOF structures incorporating more than one ligand/metal into the crystal lattice. MTV-MOFs have demonstrated enhanced properties by virtue of the additional functionalities incorporated within their structures. One approach to developing MTV-MOFs is through post-synthetic modification (PSM), where new functionalities are introduced after the initial synthesis, thereby achieving the enhanced properties of MTV-MOFs even in cases where the new functionalities are incompatible with MOF synthesis.

Single-Crystal Transformation Engineering the Spin Change of Metal-Organic Frameworks via Cluster Deconstruction

Spin crossover (SCO) materials with new architectures will expand and enrich the research in the SCO field. Here, we report two metal-organic frameworks (MOFs) containing tetradentate organic ligands and hexatopic linkers [Ag8 X8 (CN)6 ]6- (X=Br and I), which represents the first SCO MOF with clusters as building blocks. The silver halide cluster can be further removed after reacting with lithium tetracyanoquinodimethan (LiTCNQ). Such post-synthetic modification (PSM) is realized via single-crystal to single-crystal (SCSC) transformation from urk to nbo topology. Accordingly, the spin state and fluorescence properties are greatly modified by cluster deconstruction. Therefore, these achievements will provide new ideas for the design of new SCO systems and the development of PSM methods.

Utilization of 2D materials in aqueous zinc ion batteries for safe energy storage devices

Aqueous rechargeable battery has been an intense topic of research recently due to the significant safety issues of conventional Li-ion batteries (LIBs). Amongst the various candidates of aqueous batteries, aqueous zinc ion batteries (AZIBs) hold great promise as a next generation safe energy storage device due to its low cost, abundance in nature, low toxicity, environmental friendliness, low redox potential, and high theoretical capacity. Yet, the promise has not been realized due to their limitations, such as lower capacity compared to traditional LIB, dendrite growth, detrimental degradation of electrode materials structure as ions intercalate/de-intercalate, and gas evolution/corrosion at the electrodes, which remains a significant challenge. To address the challenges, various 2D materials with different physiochemical characteristics have been utilized. This review explores fundamental physiochemical characteristics of widely used 2D materials in AZIBs, including graphene, MoS2, MXenes, 2D metal organic framework, 2D covalent organic framework, and 2D transition metal oxides, and how their characteristics have been utilized or modified to address the challenges in AZIBs. The review also provides insights and perspectives on how 2D materials can help to realize the full potential of AZIBs for next-generation safe and reliable energy storage devices.

Structure and properties of metal-organic frameworks modulated by sulfate ions

Anions play a significant role in the construction of metal-organic frameworks (MOFs). Anions can affect coordination between metal ions and organic ligands, and the formation of crystal structures, thereby affecting the structure and properties of MOFs. Two novel 3D porous MOFs ({[Cd3(TIPE)2(SO4)1.6(H2O)2.4]·2.8OH·6.2H2O}n (MOF-1) and {[Cd3(TIPE)2(SO4)3(H2O)2]·10H2O}n (MOF-2)) were successfully synthesized, by introducing SO42- to design and adjust their structure and properties, in which the sulfate ions not only participated in coordination but also played a bridging role. Both MOF-1 and MOF-2 exhibited high stability and strong fluorescence properties, and their fluorescence properties also changed compared to those of previously reported 2D nonporous MOF-3 ({[Cd2(TIPE)2Cl3(ACN)]·CdCl3·3H2O}n) with an identical ligand. They could also be used in combination with MOF-3 to distinguish between Fe3+ and Cr2O72- ions, due to a change in their fluorescence properties. In this work, the structure was reshaped by introducing sulfate ions, and the role and function of the sulfate ions in the structure were studied, providing a feasible idea for the design and precise regulation of MOFs.

Spatial Distribution of Nitrogen Binding Sites in Metal-Organic Frameworks for Selective Ethane Adsorption and One-Step Ethylene Purification

The one-step purification of ethylene (C2 H4 ) from mixtures containing ethane (C2 H6 ) and acetylene (C2 H2 ) is an industrially important yet challenging process. In this work, we present a site-engineering strategy aimed at manipulating the spatial distribution of binding sites within a confined pore space. We realized successfully by incorporating nitrogen-containing heterocycles, such as indole-5-carboxylic acid (Ind), benzimidazole-5-carboxylic acid (Bzz), and indazole-5-carboxylic acid (Izo), into the robust MOF-808 platform via post-synthetic modification. The resulting functionalized materials, namely MOF-808-Ind, MOF-808-Bzz, and MOF-808-Izo, demonstrated significantly improved selectivity for C2 H2 and C2 H6 over C2 H4 . MOF-808-Bzz with two uniformly distributed nitrogen binding sites gave the optimal geometry for selective ethane trapping through multiple strong C-H⋅⋅⋅N hydrogen bonds, leading to the highest C2 H2 /C2 H4 and C2 H6 /C2 H4 combined selectivities among known MOFs. Column breakthrough experiments validated its ability to purify C2 H4 from ternary C2 H2 /C2 H4 /C2 H6 mixtures in a single step.

Experimental and Theoretical Evaluation of the Thermodynamics of the Carbonation Reaction of ZIF-8 and Its Close-Packed Polymorph with Carbon Dioxide

We report the first experimental and theoretical evaluation of the thermodynamic driving force for the reaction of metal-organic framework (MOF) materials with carbon dioxide, leading to a metal-organic carbonate phase. Carbonation upon exposure of MOFs to CO2 is a significant concern for the design and deployment of such materials in carbon storage technologies, and this work shows that the formation of a carbonate material from the popular SOD-topology framework material ZIF-8, as well as its dense-packed dia-topology polymorph, is significantly exothermic. With knowledge of the crystal structure of the starting and final phases in the carbonation reaction, we have also identified periodic density functional theory approaches that most closely reproduce the measured reaction enthalpies. This development now permits the use of advanced theoretical calculations to calculate the driving forces behind the carbonation of zeolitic imidazolate frameworks with reasonable accuracy.

Covalent connections between metal-organic frameworks and polymers including covalent organic frameworks

Hybrid composite materials combining metal-organic frameworks (MOFs) and polymers have emerged as a versatile platform for a broad range of applications. The crystalline, porous nature of MOFs and the flexibility and processability of polymers are synergistically integrated in MOF-polymer composite materials. Covalent bonds, which form between two distinct materials, have been extensively studied as a means of creating strong molecular connections to facilitate the dispersion of "hard" MOF particles in "soft" polymers. Numerous organic transformations have been applied to post-synthetically connect MOFs with polymeric species, resulting in a variety of covalently connected MOF-polymer systems with unique properties that are dependent on the characteristics of the MOFs, polymers, and connection modes. In this review, we provide a comprehensive overview of the development and strategies involved in preparing covalently connected MOFs and polymers, including recently developed MOF-covalent organic framework composites. The covalent bonds, grafting strategies, types of MOFs, and polymer backbones are summarized and categorized, along with their respective applications. We highlight how this knowledge can serve as a basis for preparing macromolecular composites with advanced functionality.

A Cu@ZIF-8 encapsulated antibacterial and angiogenic microneedle array for promoting wound healing

Skin wounds caused by external injuries remain a serious challenge in clinical practice. Wound dressings that are antibacterial, pro-angiogenic, and have potent regeneration capacities are highly desirable for wound healing. In this study, a minimally invasive and wound-friendly Cu@ZIF-8 encapsulated PEGDA/CMCS microneedle (MN) array was fabricated using the molding method to promote wound healing. The MNs had good biocompatibility, excellent mechanical strength, as well as strong antibacterial properties and pro-angiogenic effects. When incubated with H2O2, Cu@ZIF-8 nanoparticles generated reactive oxygen species, which contributed to their antibacterial properties. Due to the oxidative stress of the cupric ions released from Cu@ZIF-8 and the anti-bacterial capability of the PEGDA/CMCS hydrogel scaffold, such an MN array presents excellent antibacterial activity. Moreover, with the continuous release of Cu ions from the scaffold, such MNs are effective in terms of promoting angiogenesis. With considerable biocompatibility and a minimally invasive approach, the degradable MN array composed of PEGDA/CMCS possessed superior capabilities to continuously and steadily release the loaded ingredients and avoid secondary damage to the wound. Benefiting from these features, the Cu@ZIF-8 encapsulated degradable MN array can dramatically accelerate epithelial regeneration and neovascularization. These results indicated that the combination of Cu@ZIF-8 and degradable MN arrays is valuable in promoting wound healing, which opened a new window for treatment of skin defection.

Stimuli-Responsive Design of Metal-Organic Frameworks for Cancer Theranostics: Current Challenges and Future Perspective

Scientific fraternity revealed the potential of stimuli-responsive nanotherapeutics for cancer treatment that aids in tackling the major restrictions of traditionally reported drug delivery systems. Among stimuli-responsive inorganic nanomaterials, metal-organic frameworks (MOFs) have transpired as unique porous materials displaying resilient structures and diverse applications in cancer theranostics. Mainly, it demonstrates tailorable porosity, versatile chemical configuration, tunable size and shape, and feasible surface functionalization, etc. The present review provides insights into the design of stimuli-responsive multifunctional MOFs for targeted drug delivery and bioimaging for effective cancer therapy. Initially, the concept of cancer, traditional cancer treatment, background of MOFs, and approaches for MOFs synthesis have been discussed. After this, applications of stimuli-responsive multifunctional MOFs-assisted nanostructures that include pH, light, ions, temperature, magnetic, redox, ATP, and others for targeted drug delivery and bioimaging in cancer have been thoroughly discussed. As an outcome, the designed multifunctional MOFs showed an alteration in properties due to the exogenous and endogenous stimuli that are beneficial for drug release and bioimaging. The several reported types of stimuli-responsive surface-modified MOFs revealed good biocompatibility to normal cells, promising drug loading capability, target-specific delivery of anticancer drugs into cancerous cells, etc. Despite substantial progress in this field, certain crucial issues need to be addressed to reap the clinical benefits of multifunctional MOFs. Specifically, the toxicological compatibility and biodegradability of the building blocks of MOFs demand a thorough evaluation. Moreover, the investigation of sustainable and greener synthesis methods is of the utmost importance. Also, the low flexibility, off-target accumulation, and compromised pharmacokinetic profile of stimuli-responsive MOFs have attracted keen attention. In conclusion, the surface-modified nanosized design of inorganic diverse stimuli-sensitive MOFs demonstrated great potential for targeted drug delivery and bioimaging in different kinds of cancers. In the future, the preference for stimuli-triggered MOFs will open a new frontier for cancer theranostic applications.

A sustainable avenue for the synthesis of propargylamines and benzofurans using a Cu-functionalized MIL-101(Cr) as a reusable heterogeneous catalyst

A heterogeneous copper-catalyzed A3 coupling reaction of aldehydes, amines, and alkynes for the synthesis of propargylamines and benzofurans has been developed. Here, the modified metal-organic framework MIL-101(Cr)-SB-Cu complex was chosen as the heterogeneous copper catalyst and prepared via post-synthetic modification of amino-functionalized MIL-101(Cr). The structure, morphology, thermal stability, and copper content of the catalyst were determined by FT-IR, PXRD, SEM, TEM, EDX, TGA, XPS, and ICP-OES. The catalyst shows high catalytic activity for the aforementioned reactions under solvent-free reaction conditions. High yields, low catalyst loading, easy catalyst recovery and reusability with not much shrink in catalytic activity, and a good yield of 82% in gram-scale synthesis are some of the benefits of this protocol that drove it towards sustainability.

Rationally Tailored Mesoporous Hosts for Optimal Protein Encapsulation

Proteins play important roles in the therapeutic, medical diagnostic, and chemical catalysis industries. However, their potential is often limited by their fragile and dynamic nature outside cellular environments. The encapsulation of proteins in solid materials has been widely pursued as a route to enhance their stability and ease of handling. Nevertheless, the experimental investigation of protein interactions with rationally designed synthetic hosts still represents an area in need of improvement. In this work, we leveraged the tunability and crystallinity of metal-organic frameworks (MOFs) and developed a series of crystallographically defined protein hosts with varying chemical properties. Through systematic studies, we identified the dominating mechanisms for protein encapsulation and developed a host material with well-tailored properties to effectively encapsulate the protein ubiquitin. Specifically, in our mesoporous hosts, we found that ubiquitin encapsulation is thermodynamically favored. A more hydrophilic encapsulation environment with favorable electrostatic interactions induces enthalpically favored ubiquitin-MOF interactions, and a higher pH condition reduces the intraparticle diffusion barrier, both leading to a higher protein loading. Our findings provide a fundamental understanding of host-guest interactions between proteins and solid matrices and offer new insights to guide the design of future protein host materials to achieve optimal protein loading. The MOF modification technique used in this work also demonstrates a facile method to develop materials easily customizable for encapsulating proteins with different surface properties.

Long aliphatic chain derivatives of trigonal lanthanide complexes

The trigonal lanthanide complexes LnL (H₃L = tris(((3-formyl-5-methylsalicylidene)amino)ethyl)amine) contain three pendant aldehyde groups and are known to react with primary amines. Reacting LnL (Ln = Yb, Lu) with 1-octadecylamine yields the novel aliphatic lanthanide complexes LnL¹⁸ (H₃L¹⁸ = tris(((3-(1-octadecylimine)-5-methylsalicylidene)amino)ethyl)amine) where the three aldehyde groups are transformed to 1-octadecylimine groups. Herein the syntheses, structural characterisation and magnetic properties of LnL¹⁸ are presented. The crystal structure of YbL¹⁸ shows that the reaction of YbL with 1-octadecylamine leads to only very subtle perturbations in the first coordination sphere of Yb(III), with the Yb(III) ion retaining its heptacoordination and similar bond lengths and angles to the ligand. The three octadecyl chains in each complex were found to direct crystal packing into lipophilic arrays of van der Waals interaction-driven hydrocarbon stacking. The static magnetic properties of YbL¹⁸ were compared to those of the non-derivatised complex YbL. The energy level splitting of the ²F_7/2 ground multiplet was found, by emission spectroscopy, to be very similar between the derivatised and non-derivatised complexes. A.c. magnetic susceptibility measurements on YbL¹⁸ and YbL diluted at 4.8% and 4.2% into the diamagnetic hosts LuL¹⁸ and LuL, respectively, revealed that the spin-lattice relaxation of both complexes is governed by a low temperature direct process and a high temperature Raman process. In the high temperature regime, the derivatised complex was also found to have faster spin-lattice relaxation, which is likely due to the increased number of phonons in the octadecyl chains.

Hierarchical Mesoporous Metal-Organic Frameworks with Boric Acid Sites on the Inner Surface of Small Mesopores for the Extraction of Nucleotides in Human Plasma Samples

In this work, a boronate affinity-functionalized hierarchical mesoporous metal-organic framework adsorbent with boronate sites only in the small mesopore has been structured based on UiO-66@Fe₃O₄. The introduction of large mesopores in the adsorbent can promote the diffusion of small cis-diol-containing compounds (cis-diols) into small mesopore channels, and the removal of the adsorption sites on the external surface of materials and in large mesopores can enhance the size-exclusion effect of the adsorbent. In addition, the adsorbent has faster adsorption kinetics and excellent selectivity to small cis-diols. Finally, a magnetic dispersive solid-phase extraction coupled with high-performance liquid chromatography was established for the enrichment and detection of nucleotides in plasma. Four nucleotides achieve the recoveries from 93.25 to 118.79%, the limits of detection from 0.35 to 1.26 ng·mL^-1, and the intra-day and inter-day relative standard deviations of less than 10.2%. In conclusion, this method can be directly used for the detection of small cis-diol targets in complex biological samples without protein precipitation prior to the extraction.

Synthesis of new hybrid pyridines catalyzed by Fe3O4@SiO2@urea-riched ligand/Ch-Cl

Herein, a new heterogeneous catalytic system through modification of urea functionalized magnetic nanoparticles with choline chloride [Fe₃O₄@SiO₂@urea-riched ligand/Ch-Cl] was designed and synthesized. Then, the synthesized Fe₃O₄@SiO₂@urea-riched ligand/Ch-Cl was characterized by using FT-IR spectroscopy, FESEM, TEM, EDS-Mapping, TGA/DTG and VSM techniques. After that, the catalytic usage of Fe₃O₄@SiO₂@urea-riched ligand/Ch-Cl was investigated for the synthesis of hybrid pyridines with sulfonate and/or indole moieties. Delightfully, the outcome was satisfactory and the applied strategy represents several advantages such as short reaction times, convenience of operation and relatively good yields of obtained products. Moreover, the catalytic behavior of several formal homogeneous DESs was investigated for the synthesis of target product. In addition, a cooperative vinylogous anomeric-based oxidation pathway was suggested as rational mechanism for the synthesis of new hybrid pyridines.

Gold nanoparticle decorated post-synthesis modified UiO-66-NH2 for A3-coupling preparation of propargyl amines

In this report, the novel UiO‑66‑NH₂ based-MOF(Zr) catalytic system which further modified with nitrogen-rich organic ligand (5-aminotetrazole) using post synthetic modification (PSM) approach has been prepared here as an efficient catalyst to promote the A³-coupling preparation of propargyl amines in green aquatic media. This newly highly efficient catalyst was synthesized upon Zr-based MOF (UiO‑66‑NH₂) which successfully functionalized with 2,4,6‑trichloro‑1,3,5‑triazine (TCT) and 5‑aminotetrazole, following through stabilization of gold metal (Au) nanopartilces. The addition of N-rich organic ligand through post-synthesis modification which can be assisted to stabilize the bister and stable gold nanoparticles caused to unique structure of the final composite in favor of the progress of the A³ coupling reaction. Also several strategies comprising XRD, FT-IR, SEM, BET, TEM, TGA, ICP, EDS and elemental mapping analyzes, were used to indicate the successful preparation of the UiO-66-NH₂@ Cyanuric Chloride@ 5-amino tetrazole/Au-NPs. The results of productivity catalyst are accomplished in good to excellent yields for all sort of reactions under mild conditions which is a proof of superior activity heterogeneous catalyst containing Au-nanoparticles. In addition, the suggested catalyst represented excellent reusability with no remarkable loss in activity up 9 sequential runs.

Metal-Organic Framework-Based Nanomedicines for the Treatment of Intracellular Bacterial Infections

Metal-organic frameworks (MOFs) are a highly versatile class of ordered porous materials, which hold great promise for different biomedical applications, including antibacterial therapy. In light of the antibacterial effects, these nanomaterials can be attractive for several reasons. First, MOFs exhibit a high loading capacity for numerous antibacterial drugs, including antibiotics, photosensitizers, and/or photothermal molecules. The inherent micro- or meso-porosity of MOF structures enables their use as nanocarriers for simultaneous encapsulation of multiple drugs resulting in a combined therapeutic effect. In addition to being encapsulated into an MOF's pores, antibacterial agents can sometimes be directly incorporated into an MOF skeleton as organic linkers. Next, MOFs contain coordinated metal ions in their structure. Incorporation of Fe^2/3+, Cu²⁺, Zn²⁺, Co²⁺, and Ag⁺ can significantly increase the innate cytotoxicity of these materials for bacteria and cause a synergistic effect. Finally, abundance of functional groups enables modifying the external surface of MOF particles with stealth coating and ligand moieties for improved drug delivery. To date, there are a number of MOF-based nanomedicines available for the treatment of bacterial infections. This review is focused on biomedical consideration of MOF nano-formulations designed for the therapy of intracellular infections such as Staphylococcus aureus, Mycobacterium tuberculosis, and Chlamydia trachomatis. Increasing knowledge about the ability of MOF nanoparticles to accumulate in a pathogen intracellular niche in the host cells provides an excellent opportunity to use MOF-based nanomedicines for the eradication of persistent infections. Here, we discuss advantages and current limitations of MOFs, their clinical significance, and their prospects for the treatment of the mentioned infections.

Unveiling Unexpected Modulator-CO2 Dynamics within a Zirconium Metal-Organic Framework

Carbon capture, storage, and utilization (CCSU) represents an opportunity to mitigate carbon emissions that drive global anthropogenic climate change. Promising materials for CCSU through gas adsorption have been developed by leveraging the porosity, stability, and tunability of extended crystalline coordination polymers called metal-organic frameworks (MOFs). While the development of these frameworks has yielded highly effective CO₂ sorbents, an in-depth understanding of the properties of MOF pores that lead to the most efficient uptake during sorption would benefit the rational design of more efficient CCSU materials. Though previous investigations of gas-pore interactions often assumed that the internal pore environment was static, discovery of more dynamic behavior represents an opportunity for precise sorbent engineering. Herein, we report a multifaceted in situ analysis following the adsorption of CO₂ in MOF-808 variants with different capping agents (formate, acetate, and trifluoroacetate: FA, AA, and TFA, respectively). In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis paired with multivariate analysis tools and in situ powder X-ray diffraction revealed unexpected CO₂ interactions at the node associated with dynamic behavior of node-capping modulators in the pores of MOF-808, which had previously been assumed to be static. MOF-808-TFA displays two binding modes, resulting in higher binding affinity for CO₂. Computational analyses further support these dynamic observations. The beneficial role of these structural dynamics could play an essential role in building a deeper understanding of CO₂ binding in MOFs.

Molecular Catalysis of Energy Relevance in Metal-Organic Frameworks: From Higher Coordination Sphere to System Effects

The modularity and synthetic flexibility of metal-organic frameworks (MOFs) have provoked analogies with enzymes, and even the term MOFzymes has been coined. In this review, we focus on molecular catalysis of energy relevance in MOFs, more specifically water oxidation, oxygen and carbon dioxide reduction, as well as hydrogen evolution in context of the MOF-enzyme analogy. Similar to enzymes, catalyst encapsulation in MOFs leads to structural stabilization under turnover conditions, while catalyst motifs that are synthetically out of reach in a homogeneous solution phase may be attainable as secondary building units in MOFs. Exploring the unique synthetic possibilities in MOFs, specific groups in the second and third coordination sphere around the catalytic active site have been incorporated to facilitate catalysis. A key difference between enzymes and MOFs is the fact that active site concentrations in the latter are often considerably higher, leading to charge and mass transport limitations in MOFs that are more severe than those in enzymes. High catalyst concentrations also put a limit on the distance between catalysts, and thus the available space for higher coordination sphere engineering. As transport is important for MOF-borne catalysis, a system perspective is chosen to highlight concepts that address the issue. A detailed section on transport and light-driven reactivity sets the stage for a concise review of the currently available literature on utilizing principles from Nature and system design for the preparation of catalytic MOF-based materials.

UiO-66 framework with an encapsulated spin probe: synthesis and exceptional sensitivity to mechanical pressure

Probes sensitive to mechanical stress are in demand for the analysis of pressure distribution in materials, and the design of pressure sensors based on metal-organic frameworks (MOFs) is highly promising due to their structural tunability. We report a new pressure-sensing material, which is based on the UiO-66 framework with trace amounts of a spin probe (0.03 wt%) encapsulated in cavities. To obtain this material, we developed an approach for encapsulation of stable nitroxide radical TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl) into the micropores of UiO-66 during its solvothermal synthesis. Pressure read-out using electron paramagnetic resonance (EPR) spectroscopy allows monitoring the degradation of the defected MOF structure upon pressurization, where full collapse of pores occurs at as low a pressure as 0.13 GPa. The developed methodology can be used in and ex situ and provides sensitive tools for non-destructive mapping of pressure effects in various materials.

MOF-Triggered Synthesis of Subnanometer Ag02 Clusters and Fe3+ Single Atoms: Heterogenization Led to Efficient and Synergetic One-Pot Catalytic Reactions

The combination of well-defined Fe³⁺ isolated single-metal atoms and Ag₂ subnanometer metal clusters within the channels of a metal-organic framework (MOF) is reported and characterized by single-crystal X-ray diffraction for the first time. The resulting hybrid material, with the formula [Ag⁰₂(Ag⁰)_1.34Fe^III_0.66]@Na^I₂{Ni^II₄[Cu^II₂(Me₃mpba)₂]₃}·63H₂O (Fe³⁺Ag⁰₂@MOF), is capable of catalyzing the unprecedented direct conversion of styrene to phenylacetylene in one pot. In particular, Fe³⁺Ag⁰₂@MOF─which can easily be obtained in a gram scale─exhibits superior catalytic activity for the TEMPO-free oxidative cross-coupling of styrenes with phenyl sulfone to give vinyl sulfones in yields up to >99%, which are ultimately transformed, in situ, to the corresponding phenylacetylene product. The results presented here constitute a paradigmatic example of how the synthesis of different metal species in well-defined solid catalysts, combined with speciation of the true metal catalyst of an organic reaction in solution, allows the design of a new challenging reaction.

Guiding Metal Organic Framework Morphology via Monolayer Artificial Defect-Induced Preferential Facet Selection

Guiding metal organic framework (MOF) morphology, especially without the need for chemical additives, still remains a challenge. For the first time, we report a unique surface guiding approach in controlling the crystal morphology formation of zeolitic imidazole framework-8 (ZIF-8) and HKUST-1 MOFs on disrupted alkanethiol self-assembled monolayer (SAM)-covered Au substrates. Selective molecule removal is applied to generate diverse SAM matrices rich in artificial molecular defects in a monolayer to direct the dynamic crystal growth process. When a 11-mercaptoundecanol alkanethiol monolayer is ruptured, the hydroxyl tail groups of surface residue molecules act as nucleating sites by coordination with precursor metal ions. Meanwhile, the exposed alkane chain backbones stabilize a particular facet of MOF nuclei in the dynamic growth by slowing down their crystal growth rates along a specific direction. The competitive formation between the [110] and [100] planes of ZIF-8 ultimately regulates the crystal shapes from rhombic dodecahedron, truncated rhombic dodecahedron, and truncated cube to cube. Similarly, changeable morphologies of HKUST-1 crystals are also achieved from cube and tetrakaidekahedron to octahedron, originating from the competitive selection between the [100] and [111] planes. In addition to the artificial matrix preferred orientation of initial nucleation, parameters such as temperature also play a crucial role in the resulting crystal morphology. Standing on the additive-free MOF crystal morphology growth control, porous architectures prepared in this approach can act as templates for ligand-free metal (Au, Ag, and Cu) nanocluster synthesis. The nanocluster-embedded MOF structures represent distinct crystal morphology-dependent optical properties, and interestingly, their fluorescence emission can be highly enhanced by facet-induced nanocluster packing alignments. These findings not only provide a unique thought on MOF crystal morphology guidance but also pave a new route for the accompanied property investigation and further application.

Tailor-Made Pdn L2n Metal-Organic Cages through Covalent Post-Synthetic Modification

Post-synthetic modification (PSM) is an effective approach for the tailored functionalization of metal-organic architectures, but its generalizability remains challenging. Herein we report a general covalent PSM strategy to functionalize Pd_n L_2n metal-organic cages (MOCs, n=2, 12) through an efficient Diels-Alder cycloaddition between peripheral anthracene substituents and various functional motifs bearing a maleimide group. As expected, the solubility of functionalized Pd₁₂ L₂₄ in common solvents can be greatly improved. Interestingly, concentration-dependent circular dichroism and aggregation-induced emission are achieved with chiral binaphthol (BINOL)- and tetraphenylethylene-modified Pd₁₂ L₂₄ , respectively. Furthermore, Pd₁₂ L₂₄ can be introduced with two different functional groups (e.g., chiral BINOL and achiral pyrene) through a step-by-step PSM route to obtain chirality-induced circularly polarized luminescence. Moreover, similar results are readily observed with a smaller Pd₂ L₄ system.

Selective Methane Oxidation to Acetic Acid Using Molecular Oxygen over a Mono-Copper Hydroxyl Catalyst

Acetic acid is an industrially important chemical, produced mainly via carbonylation of methanol using precious metal-based homogeneous catalysts. As a low-cost feedstock, methane is commercially transformed to acetic acid via a multistep process involving energy-intensive methane steam reforming, methanol synthesis, and, subsequently, methanol carbonylation. Here, we report a direct single-step conversion of methane to acetic acid using molecular oxygen (O₂) as the oxidant under mild conditions over a mono-copper hydroxyl site confined in a porous cerium metal-organic framework (MOF), Ce-UiO-Cu(OH). The Ce-UiO MOF-supported single-site copper hydroxyl catalyst gave exceptionally high acetic acid productivity of 335 mmolg_cat^-1 in 96% selectivity with a Cu TON up to 400 at 115 °C in water. Our spectroscopic and theoretical studies and controlled experiments reveal that the conversion of methane to acetic acid occurs via oxidative carbonylation, where methane is first activated at the copper hydroxyl site via σ-bond metathesis to afford Cu-methyl species, followed by carbonylation with in situ-generated carbon monoxide and subsequent hydrolysis by water. This work may guide the rational design of heterogeneous abundant metal catalysts for the activation and conversion of methane to acetic acid and other valuable chemicals under mild and environmentally friendly reaction conditions.