Example Of Metal-organic Framework Research Articles

Switching from Molecules to Functional Materials: Breakthroughs in Photochromism With MOFs.

Photochromic materials with properties that can be dynamically tailored as a function of external stimuli are a rapidly expanding field driven by applications in areas ranging from molecular computing, nanotechnology, or photopharmacology to programable heterogeneous catalysis. Challenges arise, however, when translating the rapid, solution-like response of stimuli-responsive moieties to solid-state materials due to the intermolecular interactions imposed through close molecular packing in bulk solids. As a result, the integration of photochromic compounds into synthetically programable porous matrices, such as metal-organic frameworks (MOFs), has come to the forefront as an emerging strategy for photochromic material development. This review highlights how the core principles of reticular chemistry (on the example of MOFs) play a critical role in the photochromic material performance, surpassing the limitations previously observed in solution or solid state. The symbiotic relationship between photoresponsive compounds and porous frameworks with a focus on how reticular synthesis creates avenues toward tailorable photoisomerization kinetics, directional energy and charge transfer, switchable gas sorption, and synergistic chromophore communication is discussed. This review not only focuses on the recent cutting-edge advancements in photochromic material development, but also highlights novel, vital-to-pursue pathways for multifaceted functional materials in the realms of energy, technology, and biomedicine.

First Examples of Metal-Organic Frameworks with Pore-Encapsulated [Co(CO)4]− Anions: Facile Synthesis, Crystal Structures and Stability Studies

Three ionic metal-organic frameworks (MOFs) with pore-capsulated Co(CO)4− anions, formulated as [Co(bix)3][Co(CO)4]2 (1), [Co(bibp)3][Co(CO)4]2 (2), and [Co(bmibp)2][Co(CO)4]2 (3); (bix = 1,4-bis(imidazol-1-yl-methyl)-benzene); bibp = 4,4′-bis(imidazolyl)biphenyl); bmibp = 4,4′-bis(2-methyl-imidazolyl)biphenyl), have been facilely synthesized for the first time through direct reactions of Co2(CO)8 with the respective bis(imidazole) ligands under mild hydro(solvo)thermal conditions. Single-crystal X-ray diffraction analysis reveals distinct structural motifs among the frameworks: MOF 1 exhibits a single pcu net, MOF 2 features a 3-fold interpenetrating pcu net, both based on 6-connected Co2+ centers and ditopic bix or bibp ligands, while MOF 3 forms a 2-fold interpenetrating sql layer constructed by 4-connected Co2+ ions and bmibp linkers. The [Co(CO)4]− anions reside within the channels of the cationic frameworks. Moreover, these MOFs, characterized by periodically ordered tetracarbonylcobaltate arrays, demonstrate notable thermal stability and maintain structural integrity in air, water, and alkaline solutions for several days.

Loading co-amorphous on Metal-Organic Frameworks for gelation elimination and anti-cancer drug delivery enhancement

Troublesome gelation occurring during the dissolution of special co-amorphous (COAM) systems poses a limitation on their further applications. Metal-Organic Frameworks (MOFs) are promising porous materials for nano-scale drug delivery due to their high loading capacity and ability to control drug release. Examples of MOFs as drug carriers with the confinement effect for COAM drugs have never been reported. In this study, to eliminate the gelation of the COAM of an anti-cancer drug gefitinib (GTB) and co-former saccharin (SAC) for enhancing their anti-cancer drug delivery, a Zr-based MOF, nanoUiO-67, was selected as drug carrier. The loading process of GTB-SAC COAM on nanoUiO-67 was revealed via a real-time spinning disk confocal fluorescence microscope. The maintenance of molecular interactions between GTB and SAC in GTB-SAC COAM after loaded on nanoUiO-67 was proven experimentally and computationally, along with the host (nanoUiO-67)-guest (drug) interactions. The combined advantages of porous materials nanoMOFs and GTB-SAC COAM were fully demonstrated in terms of excellent physical stability, desirable drug release, good bio-compatibility and higher cytotoxicity towards HeLa cells. It is expected that this novel strategy could have potential application in gelation elimination and developing multi-component drug-loaded MOFs.

Metal organic frameworks in biomedicine: Innovations in drug delivery

Metal-organic frameworks (MOFs) have emerged as a class of versatile materials, finding extensive applications in drug delivery because of their unique properties and flexible design. This comprehensive review aims to give a broad perspective on the recent advancements in the area of drug delivery applications using MOFs. The fundamental characteristics of MOFs, highlighting their exceptional porosity, high surface area, and tuneable framework structures, enable MOFs to serve as ideal drug carriers, allowing efficient drug loading and controlled release. The review delves into the various ligands and metal ions employed for drug encapsulation. These include physical encapsulation, covalent bonding, and host-guest interactions, each offering distinct advantages for diverse types of drugs and therapeutic applications. The importance of tailoring MOF properties to optimize drug loading capacity, stability, and release kinetics has been emphasized. Additionally, the explorations involve delving into the mechanisms of drug release from MOFs, with factors such as pH, temperature, and external stimuli that can be harnessed to trigger controlled drug release. The utilization of MOFs in combination therapies, such as co-delivery of multiple drugs or integrating imaging agents, has also been examined. Numerous examples of MOFs used for drug delivery, encompassing both in-vitro and in-vivo studies, covering a wide range of therapeutic areas, including cancer treatment, antimicrobial therapy, and targeted drug delivery, are included. Additionally, the review addresses the challenges and future perspectives in the development of MOFs for drug delivery. Strategies to improve MOF stability, biocompatibility, and scalability are discussed, along with the understanding of MOF-drug interaction and potential toxicity concerns. With their tuneable properties, high loading capacities, and controlled release capabilities, MOFs hold exceptional capabilities that promise to enhance the efficacy of therapeutic interventions. Continued research and development in this area can pave way for the translation of MOFs into clinical applications in the near future.

An anthraquinone-based bismuth-iron metal-organic framework as an efficient photoanode in photoelectrochemical cells.

Metal-organic frameworks (MOFs) are appealing candidate materials to design new photoelectrodes for use in solar energy conversion because of their modular nature and chemical versatility. However, to date there are few examples of MOFs that can be directly used as photoelectrodes, for which they must be able to afford charge separation upon light absorption, and promote the catalytic dissociation of water molecules, while maintaining structural integrity. Here, we have explored the use of the organic linker anthraquinone-2, 6-disulfonate (2, 6-AQDS) for the preparation of MOFs to be used as photoanodes. Thus, the reaction of 2, 6-AQDS with Bi(iii) or a combination of Bi(iii) and Fe(iii) resulted in two new MOFs, BiPF-10 and BiFePF-15, respectively. They display similar structural features, where the metal elements are disposed in inorganic-layer building units, which are pillared by the organic linkers by coordination bonds through the sulfonic acid groups. We show that the introduction of iron in the structure plays a crucial role for the practical use of the MOFs as a robust photoelectrode in a photoelectrochemical cell, producing as much as 1.23 mmol H2 cm-2 with the use of BiFePF-15 as photoanode. By means of time-resolved and electrochemical impedance spectroscopic studies we have been able to unravel the charge transfer mechanism, which involves the formation of a radical intermediate species, exhibiting a longer-lived lifetime by the presence of the iron-oxo clusters in BiFePF-15 to reduce the charge transfer resistance.

Applications and Outlooks for MOFs in Food Engineering

Food detection and food packaging play critical roles in the realm of food engineering in maintaining food safety and quality. Because of the specific large surface area (SSA) and customizable topologies, metal-organic frameworks (MOFs) have become recognized as promising materials with distinctive features. Examples of MOFs employed as photochemical and electrochemical sensors for food detection are provided in this research. These MOF-based sensors have great selectivity and sensitivity, making it possible to quickly and accurately identify pollutants or signs of food rotting in samples. Additionally, the use of MOFs in food packaging has advantages including a longer shelf life and antibacterial qualities. Food is protected from outside influences by being enclosed within MOF structures, which delays deterioration and rotting. Additionally, MOFs with antibacterial qualities can successfully stop the growth of microbes, ensuring the safety of food. MOFs have the potential to be used in new application areas, such as the controlled release of dietary supplements and flavor enhancers, in addition to food detection and packaging. To guarantee the stability and effectiveness of MOFs in various applications, additional study is necessary. The relevance of food detection and packaging in food engineering is highlighted in this paper's conclusion, which also explores the potential of MOFs as adaptable tools in both fields. The examples shown show how important MOFs are as sensors and packaging materials, but further study is needed to fully utilize their potential and address any issues that might arise.

Two robust dual-functional Cd(II) MOFs as luminescent sensors for quantitatively detection of nitrofurazone and Fe3+ ions

Developing luminescent sensors based metal organic framework (MOFs) for the detection of antibiotics and metal ions is still a major challenge. The two new ternary Cd(II)-based MOFs, namely, {[Cd(BTA)0.5(L)0.5]n} (1) and {[Cd(HBTC)(L)]n} (2) (H4BTA = 1,2,4,5-benzenetetracarboxylic acid, H3BTC = 1,2,4-benzenetricarboxylic acid, and L = 1,4-bis(2-((1H-imidazol-1-yl)methyl)-1H-benzo[d]imidazol-1-yl)but‑2-ene), were hydrothermally synthesized and characterized. 1 displays a 4,4-connected sqc183 topological framework with point symbol {42.84}, while 2 exhibits a 4,5-connected sqc65 framework with point symbol {42.64}{43.67}2. Both 1 and 2 display remarkable luminescence emission and enable selective detection of NFZ and Fe3+ ions with high anti-interference ability as well as excellent thermal and pH stability. The limits of detection (LOD) of 1 and 2 for nitrofurazone (NFZ) are 4.5 × 10−7 mol·L−1 and 9.0 × 10−7 mol·L−1, respectively. The LOD toward Fe3+ for 1 is 1.4 × 10−5 mol·L−1, for 2 is 6.2 × 10−6 mol·L−1. To the best of our knowledge, this is the first example of MOFs bearing L ligands as dual-functional luminescent sensors for sensing NFZ and Fe3+ ions. In addition, the mechanism of luminescence quenching was investigated.

Binding Materials for MOF Monolith Shaping Processes: A Review towards Real Life Application

Metal–organic frameworks (MOFs) could be utilized for a wide range of applications such as sorption, catalysis, chromatography, energy storage, sensors, drug delivery, and nonlinear optics. However, to date, there are very few examples of MOFs exploited on a commercial scale. Nevertheless, progress in MOF-related research is currently paving the way to new industrial opportunities, fostering applications and processes interconnecting fundamental chemistry with engineering and relevant sectors. Yet, the fabrication of porous MOF materials within resistant structures is a key challenge impeding their wide commercial use for processes such as adsorptive separation. In fact, the integration of nano-scale MOF crystallic structures into bulk components that can maintain the desired characteristics, i.e., size, shape, and mechanical stability, is a prerequisite for their wide practical use in many applications. At the same time, it requires sophisticated shaping techniques that can structure nano/micro-crystalline fine powders of MOFs into diverse types of macroscopic bodies such as monoliths. Under this framework, this review aims to bridge the gap between research advances and industrial necessities for fostering MOF applications into real life. Therefore, it critically explores recent advances in the shaping and production of MOF macro structures with regard to the binding materials that have received little attention to date, but have the potential to give new perspectives in the industrial applicability of MOFs. Moreover, it proposes future paths that can be adopted from both academy and industry and can further boost MOF exploitation.

Metal-Organic Frameworks with Zero and Low-Valent Metal Nodes Connected by Tetratopic Phosphine Ligands.

Metal-organic frameworks (MOFs) constructed with M0 nodes are attractive targets due to the reactivity of these low-valent metals, but examples of these MOFs remain exceedingly rare. The rational design of three-dimensional MOFs with Pd0 and Pt0 nodes using tetratopic phosphine ligands is reported. Five new MOFs have been synthesized by systematic variation of the phosphine ligands and metal precursors employed, and these represent the first examples of MOFs constructed using phosphine-metal bonds as the sole structural component. The MOFs display solid-state luminescence, with emission maxima that are significantly red-shifted compared to Pd(PPh3 )4 . In addition, a RhI low-valent coordination solid based on the same linker design is reported, which displays solid-state luminescence that is not observed for the molecular analogue.

A copper-based metal-organic framework for ratiometric detection of hydrogen sulfide with high sensitivity and fast response.

Metal-organic framework (MOF) is a class of crystalline porous solid materials which could be designed as sensors for bioactive molecules. In this study, charge transition between the ligand and the metal ions related emission and the ligand-based emission were formed simultaneously within a novel luminescent MOF with the copper reactive site as nodes. It can serve as a rare example of MOFs implicated ratiometric sensor for selective luminescent detection of H2S. The luminescent detection limitations for H2S is 0.21μM, and it possesses a fast response of 30s. The sensing mechanism is also discussed.

Polymer Matrix Incorporated with ZIF-8 for Application in Nonlinear Optics.

Polymers with embedded metal–organic frameworks (MOFs) have been of interest in research for advanced applications in gas separation, catalysis and sensing due to their high porosity and chemical selectivity. In this study, we utilize specific MOFs with high thermal stability and non-centrosymmetric crystal structures (zeolitic imidazolate framework, ZIF-8) in order to give an example of MOF–polymer composite applications in nonlinear optics. The synthesized MOF-based polymethyl methacrylate (PMMA) composite (ZIF-8–PMMA) demonstrates the possibility of the visualization of near-infrared laser beams in the research lab. The resulting ZIF-8–PMMA composite is exposed to a laser under extreme conditions and exhibits enhanced operating limits, much higher than that of the widely used inorganic materials in optics. Overall, our findings support the utilization of MOFs for synthesis of functional composites for optical application.

Alkaline earth-organic frameworks with amino derivatives of 2,6-naphthalene dicarboxylates: structural studies and fluorescence properties.

Alkaline earth metal ion organic frameworks (AEMOFs) represent a relatively underexplored subcategory of metal-organic frameworks (MOFs). In this contribution, we present the synthesis and structural study of the new MOFs 1-8 based on the alkaline earth ions Mg2+, Ca2+, Sr2+ and Ba2+ and the amino substituted bridging ligands 4-aminonaphthalene-2,6-dicarboxylate (ANDC2-) and 4,8-diaminonaphthalene-2,6-dicarboxylate (DANDC2-). Compounds 1, 5, 6, 7 and 8 constitute rare examples of three-dimensional MOFs which feature square planar M4 secondary building units (SBUs) surrounded by eight bridging ditopic ligands. The underlying topology of MOFs 1, 5, 7 and 8 conforms to the 4-c pcb net which can be simplified to the 8-c bcu net, while 6 adopts the 4-c lta net which simplifies to the 8-c reo net. To the best of our knowledge these are the first examples of MOFs of their structural types formed by linear dicarboxylates instead of trigonal tricarboxylates or tetrahedral tetracarboxylates. Compounds 2, 3 and 4 also feature three dimensional networks with linear rod-shaped SBUs with the Ba2+ MOF 3 displaying an sra rod-net and MOFs 2 and 4 showing very complex rod-nets with so far unique topologies. Fluorescence studies revealed that the free ligands exhibit strong blue-green emission displaying considerable positive solvatochromism thereby pointing towards charge transfer excited states involving the shift of electron density from the amino groups to the aromatic core. Correspondingly, the MOFs display ligand based fluorescence with small differences in emission maxima possibly attributable to the difference in the charge density of the metal ions combined with the different environments around ligands in the crystal structures.

Water Stable [Tb4] Cluster-Based Metal-Organic Framework as Sensitive and Recyclable Luminescence Sensor of Quercetin.

A novel 3D metal-organic framework (MOF){[Tb3(CBA)2(HCOO)(μ3-OH)4(H2O)]·2H2O·0.5DMF} n (S-1) was synthesized by the solvothermal method. The crystal structure indicates that [Tb4O4] cubane clusters self-assemble into an infinite chain by sharing vertex, which is further linked to adjacent chains through 1,1-cyclobutanedicarboxylic acid ligand (H2CBA), resulting in a honeycomb arrayed framework. S-1 possesses excellent water stability and still retains intact structure after exposure to water for 10 weeks or boiling water for 10 weeks. Interestingly, S-1 acts as a luminescence sensor to selectively and sensitively detect quercetin with the limit of detection (LOD) as low as 0.23 ppm (7.6 × 10-7 M). The relationship between relative luminescence intensity and concentration obeys linear in the range of 0-300 ppm (0-993 μM), which allows quantitative detection of quercetin. Importantly, S-1 can be reused at least six times with almost no change in luminescent intensity. Compared with the high performance liquid chromatography-mass spectrometry (HPLC-MS) method, S-1 was used to determine the content of quercetin in onionskin and apple peel samples with satisfactory results. Furthermore, a portable S-1 test paper is also developed and expected to be applied in practice. To our knowledge, S-1 is the first example of MOFs as luminescent sensor for quercetin.

Photochromic properties of three 2D MOFs based on 1-carboxyethyl-4,4'-bipyridinine.

Viologen units have been widely used to impart metal–organic frameworks (MOFs) with photochromic properties. However, construction of a stable photochromic system in viologen MOFs has not been fully explored. Herein, we report three examples of MOFs, namely, {[Cd(CEbpy)(m-BDC)(DMF)]·2H2O}n (1), {[Cd(CEbpy)(p-BDC)(H2O)]·H2O}n (2), and {[Zn(CEbpy)(p-HBDC)(p-BDC)0.5]·H2O}n (3) based on benzenedicarboxylic acids (m-H2BDC = 1,3-benzenedicarboxylic acid, p-H2BDC = 1,4-benzenedicarboxylic acid) and a viologen-derived ligand 1-carboxyethyl-4,4′-bipyridine (L = CEbpy). As expected, the incorporation of the viologen unit into the frameworks results in the predefined photochromism upon both sunlight and UV-light. Compounds 1–3 feature a two-dimensional (2D) layered structure and are all photochromic due to the formation of CEbpy radicals by photoinduced electron transfer (PET). The aggregates build an interesting stable crystalline framework that exhibits long-lived color constancy in the solid state.

Microporous and Flexible Framework Acoustic Metamaterials for Sound Attenuation and Contrast Agent Applications.

The low-frequency (100-1250 Hz) acoustic properties of metal-organic framework (MOF) materials were examined in impedance tube experiments. The anomalously high sound transmission loss of HKUST-1, FeBTC, and MIL-53(Al) quantitatively demonstrated that these prototypical MOFs are absorptive acoustic metamaterials. To the best of our knowledge, this is the first example of MOFs that have been demonstrated to be acoustic metamaterials. Low-frequency acoustic dampening by subwavelength MOF metamaterials is likely due to sound dissipation and absorption facilitated by multiple internal reflections within the microporous framework structure. Modification of MIL-53(Al) with flexible organic linkers clarified that acoustic signatures of the MOFs may be tailored to add or alter certain diagnostic acoustic signatures. These results may be applied to the rational design of lightweight sound-insulating construction materials and acoustic contrast agents for subsurface mapping and monitoring applications at low frequency (100-1250 Hz).

Chelating Bis(N-Heterocyclic Carbene) Palladium-Catalyzed Reactions.

N-Heterocyclic carbenes (NHCs) have been widely employed in the construction of various metal complexes and applied in the field of catalysis. In this review, a series of palladium complexes comprising chelating bis(NHC) donors (Pd-bis(NHC) complexes) are outlined according to their application in homogeneous catalysis. Examples of metal-organic frameworks containing Pd-bis(NHC) moieties are briefly discussed, in terms of their use in heterogeneous catalysis. The catalytic applications of Pd-bis(NHC) complexes (or moieties in heterogeneous catalysts) are mainly focused on the Mizoroki-Heck, Suzuki-Miyaura, and Sonogashira coupling reactions. Another 14 types of reactions are also summarized beyond these three types of reactions.

Enriching the Reticular Chemistry Repertoire: Merged Nets Approach for the Rational Design of Intricate Mixed-Linker Metal-Organic Framework Platforms.

Rational design and construction of metal-organic frameworks (MOFs) with intricate structural complexity are of prime importance in reticular chemistry. We report our latest addition to the design toolbox in reticular chemistry, namely the concept of merged nets based on merging two edge-transitive nets into a minimal edge-transitive net for the rational construction of intricate mixed-linker MOFs. In essence, a valuable net for design enclosing two edges (not related by symmetry) is rationally generated by merging two edge-transitive nets, namely (3,6)-coordinated spn and 6-coordinated hxg. The resultant merged-net, a (3,6,12)-coordinated sph net with net transitivity [32] enclosing three nodes and two distinct edges, offers potential for deliberate design of intricate mixed-linker MOFs. We report implementation of the merged-net approach for the construction of isoreticular rare-earth mixed-linker MOFs, sph-MOF-1 to -4, based on the assembly of 12-c hexanuclear carboxylate-based molecular building blocks (MBBs), displaying cuboctahedral building units, 3-c tritopic ligands, and 6-c hexatopic ligands. The resultant sph-MOFs represent the first examples of MOFs where the underlying net is merged from two 3-periodic edge-transitive nets, spn and hxg. Distinctively, the sph-MOF-3 represents the first example of a mixed-linker MOF to enclose both trigonal and hexagonal linkers. The merged-nets approach allows the logical practice of isoreticular chemistry by taking into account the mathematically correlated dimensions of the two ligands to afford the deliberate construction of a mixed-linker mesoporous MOF, sph-MOF-4. The merged-net equation and two key parameters, ratio constant and MBB constant, are disclosed. A merged-net strategy for the design of mixed-linker MOFs by strictly controlling the size ratio between edges is introduced.

3D metal-organic frameworks based on lanthanide-seamed dimeric pyrogallol[4]arene nanocapsules

Two novel 3D metal-organic frameworks (MOFs) with cds network, {[MeNH3]7[Ln8(PgC2)2(H2O)y(HCOO)7]} n · x (Solvent) ( FJI-Y4 , FJI =Fujian Institute, Ln=Gd, y =12; FJI-Y5 , Ln=Dy, y =11; PgC2= C -ethylpyrogallol[4]arene), based on unprecedented dimeric pyrogallol[4]arene-based Ln8 metal-organic nanocapsule (MONC) supramolecular building blocks and formate linkers, have been prepared under solvothermal conditions. To our best of knowledge, they present not only the first two examples of 3D hierarchical structures constructed from MONCs in metal-pyrogallol[4]arene system, but also the first two examples of MOFs based on lanthanide MONCs. Remarkably, the inner cavity volume of the Ln8 capsule in FJI-Y4 and FJI-Y5 is approximately 151 A3, which is larger than those found in previous transition metal-seamed dimeric PgC n -based MONCs. Magnetic investigation on FJI-Y4 suggests a significant magnetocaloric effect (23.97 J kg−1 K−1, Δ H = 7 T, 2.5 K), while FJI-Y5 exhibits slow relaxation of the magnetization.

Porous Liquid: A Stable ZIF-8 Colloid in Ionic Liquid with Permanent Porosity.

We reported an example of metal-organic framework (MOF)-based porous liquid by dispersing ZIF-8 ({Zn(mim)2}, mim = 2-methylimidazole) nanocrystallites in ionic liquid (IL) of [Bpy][NTf2] ( N-butyl pyridinium bis(trifluoromethyl sulfonyl)imide). Two essential challenges, stable colloid formation and porosity retention, have been overcome to prepare MOF-based porous liquid. Preventing ZIF-8 nanocrystals from aggregation before dispersing is vital to form a stable ZIF-8 colloid in IL via enhancing the interaction between ZIF-8 and IL. The resultant ZIF-8-[Bpy][NTf2] colloid is able to be stable over months without precipitating. [Bpy][NTf2] with larger ion sizes cannot occupy pores in ZIF-8, leaving the ZIF-8 cage empty for enabling access by guest molecules. The porosity of this porous liquid system was verified by positron (e+) annihilation lifetime spectroscopy and I2 adsorption in ZIF-8 in the colloid. MOF-based porous liquids could provide a new material platform for liquid-bed-based gas separations.

Novel CO2 Fluorescence Turn-On Quantification Based on a Dynamic AIE-Active Metal-Organic Framework.

Traditional CO2 sensing technologies suffer from the disadvantages of being bulky and cross-sensitive to interferences such as CO and H2O, these issues could be properly tackled by innovating a novel fluorescence-based sensing technology. Metal-organic frameworks (MOFs), which have been widely explored as versatile fluorescence sensors, are still at a standstill for aggregation-induced emission (AIE), and no example of MOFs showing a dynamic AIE activity has been reported yet. Herein, we report a novel MOF, which successfully converts the aggregation-caused quenching of the autologous ligand molecule to be AIE-active upon framework construction and exhibits bright fluorescence in a highly viscous environment, resulting in the first example of MOFs exhibiting a real dynamic AIE activity. Furthermore, a linear CO2 fluorescence quantification for mixed gases in the concentration range of 2.5-100% was thus well-established. These results herald the understanding and advent of a new generation in all solid-state fluorescence fields.