Functional Metal-organic Frameworks Research Articles

Cluster–Cluster Co‐Nucleation Induced Defective Polyoxometalate‐Based Metal–Organic Frameworks for Efficient Tandem Catalysis

AbstractThe construction of defective sites is one of the effective strategies to create high‐activity Metal–Organic frameworks (MOFs) catalysts. However, traditional synthesis methods usually suffer from cumbersome synthesis steps and disordered defect structures. Herein, a cluster–cluster co‐nucleation (CCCN) strategy is presented that involves the in situ introduction of size‐matched functional polyoxometalates (H6P2W18O62, {P2W18}) to intervene the nucleation process of cluster‐based MOFs (UiO‐66), achieving one‐step inducement of exposed defective sites without redundant post‐processing. POM‐induced UiO‐66 ({P2W18}‐0.1@UiO‐66) exhibits a classical reo topology for well‐defined cluster defects. Moreover, the defective sites and the interaction between POM and skeletal cluster nodes are directly observed by Integrated Differential Phase Contrast in Scanning Transmission Electron Microscopy (iDPC‐STEM). Owing to the molecular‐level proximity between defective sites and POM in the same nano‐reaction space, {P2W18}‐0.1@UiO‐66 exhibits efficient tandem catalysis in the preparation of γ‐valerolactone (γ‐GVL) from laevulinic acid (LA) by the combination of Lewis and Brønsted acids with 11 times higher performance than defective UiO‐66 formed by conventional coordination modulation strategy. The CCCN strategy is applicable to different POM and has the potential to be extended to other cluster‐based MOFs, which will pave a new way for the construction of functional MOFs with multi‐centered synergistic catalysis.

Functional metal-organic framework membranes with uniform unsaturated pyridine-nitrogen sites as separators for high-performance lithium metal batteries

Lithium metal batteries are a promising successor to lithium-ion batteries due to high specific capacity, low density, and low electrochemical reduction potential. However, inhomogeneous lithium deposition on the Li surface will result in the formation of lithium dendrites and eventually puncture the separator and cause a short circuit. Herein, a functional metal-organic framework membrane with uniform unsaturated pyridine-nitrogen sites is synthesized via coating UiO-67-BPY (2,2 -bipyridine- 5,5 -dicarboxylic acid, named as BPY) on a commercial polypropylene (PP) separator. By replacing the benzene ring with a pyridine ring, the functionalization and porosity of MOF is fully utilized while maintaining the excellent porosity and pore size of MOF. The Li-ion transference number (tLi+) with the functional separator is 0.69 and the ionic conductivity is improved by order of magnitude compared to a plain PP separator. The N atom of the pyridine ring on the UiO-67-BPY has a strong electrostatic interaction force, and a weak coordination bond (N–Li bonding lattice) is formed between N and Li, which leads to an increase in the concentration of free lithium ions and makes their distribution more uniform. This allows lithium ions to migrate more smoothly, which is conducive to ionic conductivity and hinders dendrite formation.

Highly defective ultra-small tetravalent MOF nanocrystals

The size and defects in crystalline inorganic materials are of importance in many applications, particularly catalysis, as it often results in enhanced/emerging properties. So far, applying the strategy of modulation chemistry has been unable to afford high-quality functional Metal–Organic Frameworks (MOFs) nanocrystals with minimized size while exhibiting maximized defects. We report here a general sustainable strategy for the design of highly defective and ultra-small tetravalent MOFs (Zr, Hf) crystals (ca. 35% missing linker, 4–6 nm). Advanced characterizations have been performed to shed light on the main factors governing the crystallization mechanism and to identify the nature of the defects. The ultra-small nanoMOFs showed exceptional performance in peptide hydrolysis reaction, including high reactivity, selectivity, diffusion, stability, and show emerging tailorable reactivity and selectivity towards peptide bond formation simply by changing the reaction solvent. Therefore, these highly defective ultra-small M(IV)-MOFs particles open new perspectives for the development of heterogeneous MOF catalysts with dual functions.

Functionalized Metal–Organic Framework with Azo Double and Amide Groups for Highly Efficient Iodine Capture

Functionalized Metal–Organic Framework with Azo Double and Amide Groups for Highly Efficient Iodine Capture

Enhancing High Voltage Stability via Fluorination of Functionalized Metal Organic Framework Electrolyte in Lithium Metal Batteries

The electrolyte stability under high‐voltage conditions considerably limits the upper cut‐off potential of solid‐state electrolytes (SSEs) and therefore the energy density of all‐solid‐state batteries (ASSBs). In this work, metal‐organic frameworks (MOFs) were fluorinated to lower the energy level of HOMO orbital and allow access to a 4F‐MOF that exhibit enhanced anodic stability. The composited 4F‐MOF/PEO electrolyte could not only transport Li+ ions in the ordered framework channels, but also provide a remarkable high‐voltage stability up to 5.0 V, shielding oxidative decomposition that would otherwise occur at around 3.9 V for conventional PEO electrolytes. In addition, stable lithium deposition was demonstrated for more than 1,300 hours at 0.1 mA·cm‐2, while reversible charge‐discharge cycling performance was delivered in assembled Li||LiNi0.5Mn1.5O4 (LNMO) ASSBs up to 5.0 V. Post‐mortem X‐ray photoelectron spectroscopy (XPS) investigation on cathodes revealed presence of a LiF‐rich cathode electrolyte interface (CEI), supporting promoted stability towards high‐voltage ASSBs.

Metal organic frameworks as polysulfide reaction modulators for lithium sulfur batteries: advances and perspectives.

Currently, lithium sulfur (Li-S) battery with high theoretical energy density has attracted great research interest. However, the diffusion and loss process of intermediate lithium polysulfide during charge-discharge hindered the application of the Li-S batteryin modern life. To overcome this issue, metal organic frameworks (MOFs) and their composites have been regarded as effective additions to restrain the LiPS diffusion process for Li-S battery. Benefiting from the unique structure with rich active sites to adsorb LiPS and accelerate the LiPS redox, the Li-S batteries with MOFs modified exhibit superior electrochemical performance. Considering the rapid development of MOFs in Li-S battery, this review summarizes the recent researches of MOFs and their composites as the sulfur host materials, functional interlayer, separator coating layer, and separator/solid electrolyte for Li-S batteries in detail. In addition, the promising design strategies of functional MOF materials are proposed to improve the electrochemical performance of Li-S battery.

Metal‐Organic Framework‐Based Composites for Rapid and Sensitive Virus Detection: Current Status and Future Prospective

AbstractThe current spread of various viruses has negatively affected human life and health. Developing enhanced virus diagnostic techniques to mitigate future outbreaks is becoming vital. Metal‐organic frameworks (MOFs) have gained significant attention for their potential applications in virus detection because of their outstanding features, including high surface area, tunable properties, and adjustable pore size. Integrating nanomaterials with MOFs can also further enhance these properties, creating a new class of materials referred to as MOF‐based nanocomposites. This review paper provides an overview of the MOF‐based nanocomposites' status and future prospects for enhanced virus detection. The recent advances in the synthesis and functionalization of MOF and MOF‐based nanocomposites for virus detection are discussed. The paper describes the different types of detection platforms, including nucleic acid and immunological detection, as well as the mechanisms of MOF‐based sensors and the techniques used to synthesize MOFs and MOF‐based nanocomposites for virus detection. Additionally, the review paper explores the potential of integrating MOFs into real sensing devices and their prospects in real‐life applications. Finally, the paper examines the current challenges of these biosensing platforms. Overall, the review paper highlights the capability of MOFs and MOF‐based nanocomposites as versatile and practical platforms for virus detection and provides a comprehensive overview of the latest advancements in this area of research.

Structural and coordination microenvironment regulated MOF with phosphorylurea group to boost uranium adsorption

With the rapid industrial development and growing environmental awareness, the efficient extraction of uranium from seawater and wastewater has emerged as a research hotspot in nuclear energy development. Although metal–organic frameworks (MOFs) materials are widely used for uranium extraction, their low stability and poor selectivity hinder further development. Herein, a novel phosphorylurea functionalized metal–organic frameworks (MOFs) with optimized pore structure and hydrophilicity is fabricated (DUT-5-POR) by in situ induced etching strategy, which synergistically achieves the regulation of structural and coordination microenvironment. The presence of mesoporous pores can accelerate ion transport and expose abundant adsorption sites to enhance the adsorption capacity of uranium. Meanwhile, the introduction of phosphorylurea groups optimizes the hydrophilicity microenvironment and surface group density of DUT-5-POR to improve selectivity and kinetics. Consequently, DUT-5-POR shows an excellent adsorption ability (Qm = 263.4 mg⋅g−1) at pH = 6 and high selectivity for various competing metal ions, particularly in the separation of uranium and vanadium. Moreover, this work provides a feasible strategy for adjusting the structure and the coordination microenvironment of MOFs and a comprehensive perspective on the adsorption of uranium by MOF-based materials.

A ratiometric electrochemical sensor for simultaneous detection of multiple heavy metal ions in water and herbal medicines based on methylene blue-functionalized metal–organic framework

Heavy metal contamination in water and herbal medicine poses a global threat to human health. There is a pressing need for the development of a simple and rapid method for simultaneous quantification. In this study, a ratiometric electrochemical sensor was first constructed using a hybrid material composed of methylene blue functionalized metal–organic framework (MB-UiO66-NH2) and multi-walled carbon nanotubes (MWCNTs). Then, MB-UiO66-NH2/MWCNTs harnessed the large specific surface area of UiO66-NH2 and good conductivity of MWCNTs, resulting in a sensor with superior analytical performance for Cd2+, Pb2+, and Hg2+ detection. Meanwhile, the ratiometric probe uses MB as an internal reference, with the ratio signal (Imetalion/IMB) serving as output. This ratiometric electrochemical sensor was able to enhance the reproducibility and reliability and eliminate interference, particularly in complex environments. Importantly, based on this ratiometric electrochemical platform, the low detection limit were 11.08 nM for Cd2+, 5.47 nM for Pb2+, and 6.42 nM for Hg2+, which realized the simultaneous, sensitive, and reliable detection. In addition, it has been successfully applied in real water and representative herbal medicine sample analysis. Therefore, this work provides a new approach for the risk assessment of heavy metal accumulation, which is conducive to safeguarding people's lives and health.

Review on functionalized metal–organic framework as potential candidate for carbon control technologies for climate change: current status and future prospective

Review on functionalized metal–organic framework as potential candidate for carbon control technologies for climate change: current status and future prospective

Recent Development of Metal-Organic Frameworks for Water Purification.

Water contamination is an increasing concern to mankind because of the increasing amount of pollutants in aquatic ecosystems. To purify the polluted water, various techniques have been used to remove hazardous components. Unfortunately, traditional cleanup techniques with a low uptake capacity are unable to achieve water purification. Metal-organic frameworks (MOFs) have recently shown potential in effective water pollutant isolation in terms of selectivity and adsorption capacity over traditional porous materials. The high surface area and versatile functionality of MOFs allow for the development of new adsorbents. The development of MOFs in a range of water treatments in the recent five years will be highlighted in this review, along with assessments of the adsorption performance relevant to the particular task. Moreover, the outlook on future opportunities for water purification using MOFs is also provided.

Metal‐Organic Framework Catalyzed Hydrogen Atom Transfer for Photocatalytic Organic Synthetic Applications

This concept paper aims to summarize recent research on the design and synthetic applications of metal‐organic frameworks (MOFs)‐based hydrogen atom transfer (HAT) catalysts. Functional MOFs have emerged as highly promising heterogeneous catalysts, leveraging their tunable, ordered structure and abundant active sites to enhance catalytic efficiency in various reactions. HAT, a versatile method for generating active open‐shell radical species through selective hydrogen abstraction, has been well explored in homogeneous photocatalysis. In contrast, heterogeneous HAT catalysis remains less developed, albeit their great potential in industry. This paper will provide a timely overview of the advancements in MOFs‐based HAT photocatalysis, classified according to catalytic centers including aromatic ketones, polyoxometalates, xanthene dyes, thiols, and alcohols, highlighting their design principles and practical applications in photocatalytic organic synthesis.

Eu3+-functionalized metal organic framework applied as “red-green indicator” for tetracycline

The misuse of antibiotics, such as tetracycline (TC), can seriously harm human health so it is of great practical importance to sensitively and rapidly detect TC. In this paper, an Eu3+-functionalized Zr-MOF (Eu3+@UiO-66-(OH)2) was successfully prepared by a post-synthetic modification strategy as a ratiometric fluorescent sensor for ultrasensitive and specific detection of TC in aqueous medium. The proposed Eu3+@UiO-66-(OH)2 sensor possessed remarkable fluorescence enhancement properties besides high specific surface area and excellent stability. In the quantitative analysis of TC, the sensor exhibited fast response (<60 s), wide linear range (0–160 μM), high sensitivity (detection limit as low as 1.33 nM) and high selectivity for TC. Furthermore, it has been successfully utilized in determination of TC in real samples, demonstrating its application potential in complex environmental water system.

Crystalline porous materials for catalytic conversion of lignin‐related substances

AbstractThe conversion of the biomass into eco‐friendly fuels and chemicals has been extensively recognized as the essential pathway to achieve the sustainable economy and carbon neutral society. Lignin, as a kind of promising biomass energy, has been certified to produce the high‐valued chemicals and fuels. Numerous efforts have been made to develop various catalysts for lignin catalytic conversion. Both metal‐organic frameworks (MOFs) and covalent organic frameworks (COFs) belong to very important heterogeneous porous catalysts due to their regular porous structures, high specific surface area, and precisely tailored diversities. In the review, the first part focused on the catalytic conversion of lignin, lignin model compounds, and lignin derivatives using the pristine MOFs, functional MOF composites, and MOF‐derived materials. The second part summarized the catalytic conversion of lignin model compounds using pristine COFs and functional COF composites. The review here mainly concentrated on the design of the materials, screening of catalytic conditions, and explorations of the corresponded mechanisms. Specifically, (1) we summarized the MOF‐ and COF‐based materials for the effects on the catalytic transformation of lignin‐related substances; (2) we emphasized the catalytic mechanism of C–C and C–O bonds cleavage together with the structure–activity relationships; (3) we in‐depth realized the relationship between the chemical/electronic/structural properties of the MOF‐ and COF‐based catalysts and their catalytic performance for lignin‐related substances. Finally, the challenges and future perspectives were also discussed on the catalytic conversion of lignin‐related substances by MOF‐ and COF‐based catalysts.

Functionalization of Defective Zr-MOFs for Water Decontamination: Mechanistic Insight into the Competitive Roles of -NH2 and -SH Sites in the Removal of Hg(II) Ions.

Functional metal-organic frameworks (MOFs), especially those based on sulfur and nitrogen atoms, were frequently applied for the removal of Hg(II) ions. However, a systematic study on the cooperative or competitive roles of -SH and -NH2 functions in the presence of secondary mechanisms (proton transfer and redox) is still rare. In this work, the UiO-66 framework (Zr6(OH)4O4(BDC)6, BDC2- = benzene-1,4-dicarboxylate) was decorated with functional monocarboxylate linkers including glycine (Gly), mercaptopropionic acid (Mer), and cysteine (Cys). Due to the molecular similarity of these functional linkers, the coordination affinity between the amine and thiol sites with Hg(II) ions can be compared, and the effect of proton transfer and redox mechanisms on the possible thiol···Hg(II) and amine···Hg(II) interactions can be investigated. The results show that the Cys@UiO-66 framework can adsorb 1288 mg g-1 of Hg(II), while Mer@UiO-66 and Gly@UiO-66 can adsorb 593 and 313 mg g-1 at pH = 7 and 500 ppm, respectively. This is due to the facts that both the amine and the thiol functions of the Cys@UiO-66 framework show synergism in Hg(II) removal, and the secondary mechanisms reduce the affinity of thiol in Mer@UiO-66 and amine in Gly@UiO-66 frameworks in the removal process of Hg(II) ions. Free -SH sites in Mer@UiO-66 undergo a redox convert to -SO3H groups, and free protonated -NH2 sites in Gly@UiO-66 do not fully deprotonate during Hg(II) removal. Yet, in the case of Cys@UiO-66, free protonated -NH2 sites are fully deprotonated, and free SH sites did not convert to -SO3H groups during Hg(II) removal. These observations show that the redox and proton transfer mechanisms can negatively affect the adsorption capacity of functional MOFs containing free -SH and -NH2 groups. So, not only the functionalization but also control over secondary mechanisms in the removal process are necessary parameters to improve the affinity between functional MOFs and Hg(II) ions.

Metal-Organic Framework-Based Nanomaterials for Regulation of the Osteogenic Microenvironment.

As the global population ages, bone diseases have become increasingly prevalent in clinical settings. These conditions often involve detrimental factors such as infection, inflammation, and oxidative stress that disrupt bone homeostasis. Addressing these disorders requires exogenous strategies to regulate the osteogenic microenvironment (OME). The exogenous regulation of OME can be divided into four processes: induction, modulation, protection, and support, each serving a specific purpose. To this end, metal-organic frameworks (MOFs) are an emerging focus in nanomedicine, which show tremendous potential due to their superior delivery capability. MOFs play numerous roles in OME regulation such as metal ion donors, drug carriers, nanozymes, and photosensitizers, which have been extensively explored in recent studies. This review presents a comprehensive introduction to the exogenous regulation of OME by MOF-based nanomaterials. By discussing various functional MOF composites, this work aims to inspire and guide the creation of sophisticated and efficient nanomaterials for bone disease management.

Dynamic Fluorescent Metal–Organic Frameworks Utilizing a Flexible Saddle‐Like 3D Linker

AbstractDesigning single‐component fluorochromic metal–organic frameworks (MOFs) with multiple stages presents a significant challenge in the field of functional and smart MOFs. In this study, this challenge is successfully addressed by designing and synthesizing a novel ligand called cyclooctatetrathiophene‐tetrapyridine (COTTTP), and incorporating it into 3D MOFs known as Zn/Cd‐COTTTP. By exploiting the intrinsic properties of COTTTP, specifically its ability to undergo geometry changes from a bent form to a more planar form, both COTTTP as an individual molecule and the resulting Zn/Cd‐COTTTP MOFs exhibit similar fluorochromic behavior. This behavior manifests as a color change from yellow to orange to red. Characterization techniques such as single crystal X‐ray diffraction, Fourier transform infrared spectroscopy, solid‐state UV–vis and near‐infrared spectroscopy, and X‐ray photoelectron spectroscopy are employed to investigate and confirm the geometry change of COTTTP within the MOF structures. Furthermore, the introduction of an auxiliary rigid ligand to the system is explored, which effectively restricts the geometry change of COTTTP and subsequently diminishes the fluorochromic behavior. This work sheds new light on the design and application of smart porous materials, particularly in the realm of single‐component fluorochromic MOFs. The successful incorporation of COTTTP and the understanding of its geometry change provide insights into the development of functional and responsive MOFs for various applications.

Quest for Multifunctionality: Current Progress in the Characterization of Heterometallic Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) are a class of porous, crystalline materials that have been systematically developed for a broad range of applications. Incorporation of two or more metals into a single crystalline phase to generate heterometallic MOFs has been shown to lead to synergistic effects, in which the whole is oftentimes greater than the sum of its parts. Because geometric proximity is typically required for metals to function cooperatively, deciphering and controlling metal distributions in heterometallic MOFs is crucial to establish structure-function relationships. However, determination of short- and long-range metal distributions is nontrivial and requires the use of specialized characterization techniques. Advancements in the characterization of metal distributions and interactions at these length scales is key to rapid advancement and rational design of functional heterometallic MOFs. This perspective summarizes the state-of-the-art in the characterization of heterometallic MOFs, with a focus on techniques that allow metal distributions to be better understood. Using complementary analyses, in conjunction with computational methods, is critical as this field moves toward increasingly complex, multifunctional systems.

Silver Nanoparticle-Functionalized Postsynthetically Modified Thiol MOF UiO-66-NH-SH for Efficient CO2 Fixation.

Thiols are essential functional groups imparting unique properties, such as reactivity and selectivity, to many vital enzymes and biomolecules. The integration of electronically soft thiol groups within metal-organic frameworks (MOFs) yields elevated reactivity and a pronounced affinity for soft metal ions. However, the scarcity of thiol-based ligands and synthetic challenges hinder the advancement of thiol-based MOFs. To bypass the difficulties of synthesizing thiol MOFs by a direct reaction between thiol-based ligands and corresponding metal salts, postsynthetic modification (PSM) of MOFs is an efficient strategy to introduce thiol functionality. Herein, we have introduced Ag nanoparticles in postsynthetically modified thiol MOFs UiO-66-NH-SH (1) (synthesized by reaction between UiO-66-NH2 and thioglycolic acid) and UiO-66-NH-SH (2) (synthesized by reaction between UiO-66-NH2 and 3-mercaptopropionic acid) to synthesize a series of heterogeneous catalysts for CO2 fixation. Catalysts Cat 1-2 and Cat 3 - 4 were synthesized from UiO-66-NH-SH (1) and UiO-66-NH-SH (2), respectively, by using varying concentrations of silver (AgNO3). Catalyst Ag@UiO-66-NH-SH (1) (Ag = 3.45%; namely Cat 2) shows the highest efficiency for the catalytic conversion of propargylic alcohol and terminal epoxide to the corresponding cyclic carbonates. Finally, a rationalized reaction mechanism is proposed by correlating our results with the current literature. This work presents a viable strategy to utilize the thiol functionality of MOFs (avoiding the complexities associated with synthesizing thiol MOFs directly from thiol ligands) as a platform for introducing catalytically active metal centers and applying them as a heterogeneous catalyst for CO2 fixation reactions.

Improving the Separation of CO2/N2 Using Impregnation of a Deep Eutectic Solvent on a Porous MOF.

As the partial pressure of CO2 in flue gas is 0.1-0.2 bar, CO2 capture at a low pressure needs more attention. Under low pressure conditions, the functional metal-organic framework (MOF) is powerful for CO2 capture. One of the effective methods to increase the absorption capacity of the MOF is impregnation with deep eutectic solvents. In this research, NH2-MIL101(Cr) is impregnated with a deep eutectic solvent of choline chloride:urea (DES ChCl:urea) to enhance the adsorption capacity. The CO2 and N2 adsorption capacity of NH2-MIL101(Cr) and DES/NH2-MIL101(Cr) was investigated at temperatures of 288.15-303.15 K and pressures up to 1 bar. The obtained results indicate that the adsorption capacity of the MOF increases by 1.7 and 3 times with the impregnated DES for CO2 and N2, respectively. Nevertheless, the pore volume of the MOF decreased after impregnation, but the adsorption capacity of the MOF increased due to the interaction of the adsorbate with the confined DES in pores. The contribution of the impregnated DES to adsorption capacity is explained according to Henry's law. Also, high heats of adsorption are attributed to the strong interaction between modified NH2-MIL101(Cr) and CO2. Also, the sample was refined at 298 K and vacuum and was reused without considerable reduction of the CO2 capture capacity after 6 times. Moreover, the impregnation of ChCl:urea into NH2-MIL101(Cr) nanostructures was studied using density functional theory-based approaches.