Magnetic metal-organic frameworks

Synthesis and characterisation of antimicrobial metal-organic frameworks as multi-drug carriers

Antibiotic resistance is a significant global concern, necessitating the development of either new antibiotics or advanced delivery methods. With this in mind, we report on the synthesis and characterisation of a new family of Metal-Organic Frameworks (MOFs), OnG6 MOFs, designed to act as multi-drug carriers for bacterial infection treatment. OnG6 is based on the pro-drug 4,4'-azodisalicylic acid (AZDH4), which in vivo produces two equivalents of para-aminosalicylic acid (ASA), a crucial drug for M. tuberculosis treatment. X-ray and computational studies revealed that OnG6 MOFs are mesoporous MOFs with etb topology and an [M2(AZD)] formula (M = Zn, OnG6-Zn; Mg, OnG6-Mg; Cu, OnG6-Cu; and Co, OnG6-Co), featuring 1-dimensional channel type pores of 25 Å diameter. OnG6 MOFs are the first reported MOFs bearing the ligand AZDH4, joining the family of mesoporous MOFs arranged in a honeycomb pattern. They absorb isoniazid (INH) and ciprofloxacin (CIPRO) with the former being a specific antibiotic for M. tuberculosis, and the latter being a broader-spectrum antibiotic. The stability of the MOFs and their capacity for antibiotic uptake depend on the nature of the metal ion, with OnG6-Mg demonstrating the highest drug absorption. The antimicrobial activity of these species was assessed against S. aureus and E. coli, revealing that the carriers containing CIPRO displayed optimal efficacy.

Urea production via photocatalytic coupling of mixed gases (CO2/NH3) using Mo(MnO4)5 supported on Ce-BTC as nano-composite catalyst

Urea used in fertilization and feed supplement, as well as a starting material for the manufacture of plastics and drugs. Urea is most commonly produced by reacting carbon dioxide with ammonia at high temperature. Photocatalysis has gained attention as a sustainable pathway for performing urea. This work focus on designing very active photocatalysts based on cerium organic framework (Ce-BTC) doped with metal oxide nanoparticles (molybdenum permanganate, Mo(MnO4)5) for production of urea from coupling of ammonia with carbon dioxide. The prepared materials were characterized using different spectral analysis and the morphology was analysed using microscopic data. The effect of catalyst loading on the production rate of urea was investigated and the obtained results showed speed rate of urea production with high production yield at low temperature. The recyclability tests confirmed the sustainability of the prepared photocatlysts (Mo(MnO4)5@Ce-BTC) which supported the beneficial of the photocatalysis process in urea production.

Utilization of a trinuclear Cu-pyrazolate inorganic motif to build multifunctional MOFs

The current work aims to generate multifunctional MOFs by incorporating a well-known inorganic motif, a trinuclear Cu-pyrazolate [Cu3(μ3-OH)(μ-Pyz)3] (T-CuP) unit, as a node of the network. Accordingly, we report herein the synthesis and properties of five new compounds using five V-shaped dicarboxylic acids as auxiliary ligands. The structural features are consistent with the theme of grafting T-CuP units as nodal points of architectures whose chassis are primarily made of bent acids. V-shaped acids also induce a helical nature inside resulting frameworks. Beside their structural and physical features, T-CuP unit-based MOFs also vindicate our thematic approach of the trinuclear Cu-pyrazolate unit imparting specific physicochemical properties, such as magnetic, electrical, and catalytic properties, to resultant MOFs. The MOFs show excellent catalytic properties in reducing 4-nitrophenol, which could be attributed to the porous nature of the network along with the presence of metal centres with unsaturated coordination within the T-CuP unit. Furthermore, efficient photocatalytic degradation of harmful organic dyes confirms their importance for environmental remediation. The presence of a T-CuP unit and various functional groups also make some of the MOFs suitable candidates for electrical applications, which is indeed manifested in encouraging proton conductivity. Finally, the potential of current MOFs, fitted with a magnetically important trinuclear Cu-pyrazolate motif, as magnetic materials has also been thoroughly investigated.

Recent Advances of Bimetallic-Metal Organic Frameworks: Preparation, Properties, and Fluorescence-Based Biochemical Sensing Applications

Bimetallic-metal organic frameworks (BiM-MOFs) or bimetallic organic frameworks represent an innovative and promising class of porous materials, distinguished from traditional monometallic MOFs by their incorporation of two metal ions alongside organic linkers. BiM-MOFs, with their unique crystal structure, physicochemical properties, and composition, demonstrate distinct advantages in the realm of biochemical sensing applications, displaying improvements in optical properties, stability, selectivity, and sensitivity. This comprehensive review explores into recent advancements in leveraging BiM-MOFs for fluorescence-based biochemical sensing, providing insights into their design, synthesis, and practical applications in both chemical and biological sensing. Emphasizing fluorescence emission as a transduction mechanism, the review aims to guide researchers in maximizing the potential of BiM-MOFs across a broader spectrum of investigations. Furthermore, it explores prospective research directions and addresses challenges, offering valuable perspectives on the evolving landscape of fluorescence-based probes rooted in BiM-MOFs.

Ti-based MOFs with acetic acid pendings as an efficient catalyst in the preparation of new spiropyrans with biological moieties

The strategy of designing heterogeneous porous catalysts by a post-modification method is a smart strategy to increase the catalytic power of desired catalysts. Accordingly, in this report, metal-organic frameworks based on titanium with acetic acid pending were designed and synthesized via post-modification method. The structure of the target catalyst has been investigated using different techniques such as FT-IR, XRD, SEM, EDX, Mapping, and N2 adsorption/desorption (BET/the BJH) the correctness of its formation has been proven. The catalytic application of Ti-based MOFs functionalized with acetic acid was evaluated in the preparation of new spiropyrans, and the obtained results show that the catalytic performance is improved by this modification. The strategy of designing heterogeneous porous catalysts through post-modification methods presents a sophisticated approach to enhancing the catalytic efficacy of desired catalysts. In this context, our study focuses on the synthesis and characterization of metal-organic frameworks (MOFs) based on titanium, functionalized with acetic acid pendants, using a post-modification method. Various characterization techniques, including Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), mapping, and N2 adsorption/desorption (BET/BJH), were employed to investigate the structure and composition of the synthesized catalyst. These techniques collectively confirmed the successful formation and structural integrity of the target catalyst. The structure of the synthesized products was confirmed by melting point, 1H-NMR and 13C-NMR and FT-IR techniques. Examining the general process of catalyst synthesis and its catalytic application shows that the mentioned modification is very useful for catalytic purposes. The presented catalyst was used in synthesis of a wide range of biologically active spiropyrans with good yields. The simultaneous presence of several biologically active cores in the synthesized products will highlight the biological properties of these compounds. The present study offers a promising insight into the rational design, synthesis, and application of task-specific porous catalysts, particularly in the context of synthesizing biologically active candidate molecules.

Functionalization of Magnetic UiO-66-NH2 with a Chiral Cu(l-proline)2 Complex as a Hybrid Asymmetric Catalyst for CO2 Conversion into Cyclic Carbonates

In this study, a chiral [Cu(l-proline)2] complex-modified Fe3O4@SiO2@UiO-66-NH2(Zr) metal-organic framework [Fe3O4@SiO2@UiO-66-NH-Cu(l-proline)2] via multifunctionalization strategies was designed and synthesized. One simple approach to chiralize an achiral MOF-structure that cannot be directly chiralized using a chiral secondary agent like 4-hydroxy-l-proline. Therefore, this chiral catalyst was synthesized with a simple and multistep method. Accordingly, Fe3O4@SiO2@UiO-66-NH2 has been synthesized via Fe3O4 modification with tetraethyl orthosilicate and subsequently with ZrCl4 and 2-aminoterephthalic acid. The presence of the silica layer helps to stabilize the Fe3O4 core, while the bonding between Zr4+ and the -OH groups in the silica layer promotes the development of Zr-MOFs on the Fe3O4 surface, and then the surfaces of the synthesized magnetic MOFs composite are functionalized with 1,2-dichloroethane and Cu(II) complex with 4-hydroxy-l-proline, [Cu(l-proline)2] to afford the magnetically chiral nanocatalyst. Multiple techniques were employed to characterize this magnetically chiral nanocatalyst such as Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), powder X-ray diffraction (PXRD), circular dichroism (CD), inductively coupled plasma (ICP), thermogravimetric analysis (TGA), vibrating-sample magnetometry (VSM), and Brunauer-Emmett-Teller (BET) analyses. Moreover, a magnetically chiral nanocatalyst shows the asymmetric CO2 fixation reaction under solvent-free conditions at 80 °C and in ethanol under reflux conditions with up to 99 and 98% ee, respectively. Furthermore, the reaction mechanism was illustrated concerning the total energy of the reactant, intermediates and product, and the structural parameters were analyzed.

Solvation/desolvation induced reversible distortion change and switching between spin crossover and single molecular magnet behaviour in a cobalt(II) complex

Coexistence and switching between spin-crossover (SCO) and single molecular magnet (SMM) behaviours in one single complex may lead to materials that exhibit bi-stable and stimuli sensitive properties in a wide temperature range and under multiple conditions; unfortunately, the conflict and dilemma in the principle of approaching SCO and SMM molecules make it particularly difficult; at low temperature, low spin (LS) SCO molecules possess highly symmetrical geometry and isotropic spins, which are not suitable for SMM behaviour. Herein, we overcome this issue by using a rationally designed Co(II) mononuclear complex [Co(MeOphterpy)2] (ClO4)2 (1; MeOphterpy = 4'-(4-methoxyphenyl)-2,2':6',2''-terpyridine), the magnetic properties of which reversibly respond to desolvation and solvation. The solvated structure reinforced a low distortion of the coordination sphere via hydrogen bonding between ligands and methanol molecules, while in the desolvated structure a methoxy group flipping occurred, increasing the distortion of the coordination sphere and stabilising the HS state at low temperature, which exhibited a field-induced slow magnetic relaxation, resulting in a reversible switching between SCO and SMM properties within one molecule.

Construction of Indium(III)-Organic Framework Based on a Flexible Cyclotriphosphazene-Derived Hexacarboxylate as a Reusable Green Catalyst for the Synthesis of Bioactive Aza-Heterocycles

The constant demand for eco-friendly methods of synthesizing complex organic compounds inspired researchers to design and develop modern, highly efficient heterogeneous catalytic systems. Herein, In-HCPCP metal-organic framework (SRMIST-1), a heterogeneous Lewis acid catalyst containing less toxic indium and eco-friendly robust cyclotriphosphazene and exhibiting notable chemical and thermal stability, durable catalytic activity, and exceptional reusability was produced through the reaction between indium(III) nitrate hydrate and hexakis(4-carboxylatophenoxy)-cyclotriphosphazene. In the SRMIST-1 structure, secondary building units {InO7} are assembled by a connection of η2- and η1-carboxylic oxo atoms from different HCPCP ligands, forming a three-dimensional network. The occurrence of regularly distributed In(III) sites in SRMIST-1 confers superior reactivity on the catalyst toward the synthesis of 2,3-dihydroquinazolin-4(1H)-ones and 3,4-dihydro-2H-1,2,4-benzothiadiazine-1,1-dioxides by the cyclization reaction of 2-aminobenzamides and 2-aminobenzenesulphonamides with aldehydes under optimized reaction conditions, respectively. The notable features of this method include broad functional group compatibility, low catalyst loading (1-5 mol %), mild reaction conditions, easy workup procedures, good to excellent reaction yields, ethanol as a green solvent, reusability of the catalyst (five cycles), and economic attractiveness, which is mainly due to sustainability of SRMIST-1 as a reusable green catalyst. Our findings demonstrate that the highly reactive and reusable green catalyst finds widespread applications in medicinal chemistry.

Recent advances in metal-organic frameworks for stimuli-responsive drug delivery

After entering the human body, drugs for treating diseases, which are prone to delivery and release in an uncontrolled manner, are affected by various factors. Based on this, many researchers utilize various microenvironmental changes encountered during drug delivery to trigger drug release and have proposed stimuli-responsive drug delivery systems. In recent years, metal-organic frameworks (MOFs) have become promising stimuli-responsive agents to release the loaded therapeutic agents at the target site to achieve more precise drug delivery due to their high drug loading, excellent biocompatibility, and high stimuli-responsiveness. The MOF-based stimuli-responsive systems can respond to various stimuli under pathological conditions at the site of the lesion, releasing the loaded therapeutic agent in a controlled manner, and improving the accuracy and safety of drug delivery. Due to the changes in different physical and chemical factors in the pathological process of diseases, the construction of stimuli-responsive systems based on MOFs has become a new direction in drug delivery and controlled release. Based on the background of the rapidly increasing attention to MOFs applied in drug delivery, we aim to review various MOF-based stimuli-responsive drug delivery systems and their response mechanisms to various stimuli. In addition, the current challenges and future perspectives of MOF-based stimuli-responsive drug delivery systems are also discussed in this review.

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.

Metallic nanostructure-based aptasensors for robust detection of proteins

There is a significant need for fast, cost-effective, and highly sensitive protein target detection, particularly in the fields of food, environmental monitoring, and healthcare. The integration of high-affinity aptamers with metal-based nanomaterials has played a crucial role in advancing the development of innovative aptasensors tailored for the precise detection of specific proteins. Aptamers offer several advantages over commonly used molecular recognition methods, such as antibodies. Recently, a variety of metal-based aptasensors have been established. These metallic nanomaterials encompass noble metal nanoparticles, metal oxides, metal-carbon nanotubes, carbon quantum dots, graphene-conjugated metallic nanostructures, as well as their nanocomposites, metal-organic frameworks (MOFs), and MXenes. In general, these materials provide enhanced sensitivity through signal amplification and transduction mechanisms. This review primarily focuses on the advancement of aptasensors based on metallic materials for the highly sensitive detection of protein targets, including enzymes and growth factors. Additionally, it sheds light on the challenges encountered in this field and outlines future prospects. We firmly believe that this review will offer a comprehensive overview and fresh insights into metallic nanomaterials-based aptasensors and their capabilities, paving the way for the development of innovative point-of-care (POC) diagnostic devices.

Quality-dependent performance of hydrophobic ZIF-67 upon high-pressure water intrusion-extrusion process

Zeolitic imidazolate framework (ZIF) microporous materials have already been employed in many fields of energetic and environmental interest since the last decade. The commercial scale production of some of these materials makes them more accessible for their implementation in industrial processes; however, their massive synthesis may entail modifications to the preparation protocols, which may result in a loss in the optimization of this process and a drop in the material's quality. This fact may have implications for the performance of these materials during their lifetime, especially when they are used in applications such as energy dissipation, in which they are subjected to several operating cycles under high pressures. This study focuses on ZIF-67, a material that has demonstrated in the past its ability to dissipate energy through the water intrusion-extrusion process under high pressure. Two ZIF-67 samples were synthesized using different protocols, and 2 batches of different qualities (labelled as high quality (HQ) and low quality (LQ)) were obtained and analysed by water porosimetry to study their performance in the intrusion-extrusion process. Unexpectedly, minor structural differences, which are typically neglected especially under production conditions, had a dramatic effect on their performance. The results presented in this study reiterate the importance of quality control with respect to reproducibility of experimental results. In a broader perspective, they are critical to the technology transfer from academia to industry.

Three-Dimensional Hydrogen-Bonded Porous Metal-Organic Framework for Natural Gas Separation with High Selectivity

A 3D hydrogen-bonded metal-organic framework, [Cu(apc)2]n (TJU-Dan-5, Hapc = 2-aminopyrimidine-5-carboxylic acid), was synthesized via a solvothermal reaction. The activated TJU-Dan-5 with permanent porosity exhibits a moderate uptake of 1.52 wt% of hydrogen gas at 77 K. The appropriate BET surface areas and decoration of the internal polar pore surfaces with groups that form extensive hydrogen bonds offer a more favorable environment for selective C2H6 adsorption, with a predicted selectivity for C2H6/CH4 of around 101 in C2H6/CH4 (5:95, v/v) mixtures at 273 K under 100 kPa. The molecular model calculation demonstrates a C-H···π interaction and a van der Waals host-guest interaction of C2H6 with the pore walls. This work provides a strategy for the construction of 3D hydrogen-bonded MOFs, which may have great potential in the purification of natural gas.

Origin of Weak Magnetic Coupling in a Dimanganese(II) Complex Bridged by the Tetrathiafulvalene-Tetrathiolate Radical

Magnetic exchange coupling (J) between different spin centers plays a crucial role in molecule-based magnetic materials. Direct exchange coupling between an organic radical and a metal is frequently stronger than superexchange through diamagnetic ligands, and the strategy of using organic radicals to engender desirable magnetic properties has been an area of active investigation. Despite significant advances and exciting bulk properties, the magnitude of J for radical linkers bridging paramagnetic centers is still difficult to rationally predict. It is thus important to elucidate the features of organic radicals that govern this parameter. Here, we measure J for the tetrathiafulvalene-tetrathiolate radical (TTFtt3-•) in a dinuclear Mn(II) complex. Magnetometry studies show that the antiferromagnetic coupling in this complex is much weaker than that in related Mn(II)-radical compounds, in contrast to what might be expected for the S-based chelating donor atoms of TTFtt. Experimental and computational analyses suggest that this small J coupling may be attributed to poor overlap between Mn- and TTFtt-based magnetic orbitals coupled with insignificant spin density on the coordinating S-atoms. These factors override any expected increase in J from the comparatively strong S-donors. This work elucidates the magnetic coupling properties of the TTFtt3-• radical for the first time and also demonstrates how multiple competing factors must be considered in rationally designing organic radical ligands for molecular-based magnetic compounds.

Interlayer interaction-force-tuned magnetic responses in CoII-tetrazolate-carboxylate system from canted antiferromagnet to field-induced metamagnet

Interlayer magnetic couplings of low-dimensional magnets have significantly dominated magnetic behavior through skillful regulation of interlayer interacting forces. To identify interaction-force-regulated interlayer magnetic communications, two air-stable Co(II)-based coordination polymers (CPs), a well-isolated layered structure with approximately 12.6 Å interlayer separation and a carboxylate-extended three-dimensional framework with an inter-ribbon distance of 5.8 Å, have been solvothermally fabricated by varying polycarboxylate mediators in a ternary CoII-tetrazolate-carboxylate system. The layered CP with antiparallel-arranged {Co2(COO)2}n chains interconnected only via cyclic tetrazolyl linkages behaves as a spin-canted antiferromagnet with a Néel temperature of 2.6 K, due to strong intralayer antiferromagnetic couplings and negligible interlayer magnetic interactions. In contrast, the compact three-dimensional framework with corner-sharing Δ-ribbons tightly aggregated through μ2-η1:η1-COO- is a field-induced metamagnet from a canted antiferromagnet to a weak ferromagnet with a small critical field of Hc = 90 Oe. Apparently, these interesting magnetic responses reveal the importance of an interacting force from the magnetic subunits for the magnetic behavior of the molecular magnet, greatly enriching the magnetostructural correlations of transition-metal-based molecular magnets.

Intrinsic room-temperature ferromagnetism in a two-dimensional semiconducting metal-organic framework

The development of two-dimensional (2D) magnetic semiconductors with room-temperature ferromagnetism is a significant challenge in materials science and is important for the development of next-generation spintronic devices. Herein, we demonstrate that a 2D semiconducting antiferromagnetic Cu-MOF can be endowed with intrinsic room-temperature ferromagnetic coupling using a ligand cleavage strategy to regulate the inner magnetic interaction within the Cu dimers. Using the element-selective X-ray magnetic circular dichroism (XMCD) technique, we provide unambiguous evidence for intrinsic ferromagnetism. Exhaustive structural characterizations confirm that the change of magnetic coupling is caused by the increased distance between Cu atoms within a Cu dimer. Theoretical calculations reveal that the ferromagnetic coupling is enhanced with the increased Cu-Cu distance, which depresses the hybridization between 3d orbitals of nearest Cu atoms. Our work provides an effective avenue to design and fabricate MOF-based semiconducting room-temperature ferromagnetic materials and promotes their practical applications in next-generation spintronic devices.

Crystal structure and photocatalytic activity of luminescent 3D-Supramolecular metal organic framework of dysprosium

A 3D supramolecular metal organic framework of dysprosium has been fabricated through a facile hydrothermal procedure with the ligand, 2,6-naphthalene disulphonic acid and the co-ligand, 4,4'-bipyridine. The MOF has been characterized as [C60H81DyN8O30S4] by routine analytical procedures. SXRD studies of the MOF show the existence of a hydrogen-bonded 3D supramolecular structure with high porosity. It crystallizes in monoclinic space group P21/n with unit cell parameters, a = 16.5424(6) Å, b = 37.0052(14) Å, c = 24.4361(9) Å, β = 100.7410°, α = γ = 90°. The Dy-MOF has eight coordinated water molecules around the metal centre and exhibits square anti-prismatic geometry. The band gap is 3.11 eV. The degradation experiments under visible light confirmed that Dy-MOF can act as a photocatalyst. Addition of hydrogen peroxide remarkably increases the degradation efficiency of the MOF through an advanced oxidation process. The newly synthesized MOF produced sharp emission peaks characteristic of dysprosium ion.

Metamagnetism in a coordination polymer built of trimeric cobalt units and melamine

A coordination polymer of linear trimeric cobalt units and melamine has been synthesized. The magnetic isotherms of violet coloured crystals as long as 400 μm show a field-induced transition in an external field of about 2 T at temperatures approximately below 2 K. It is addressed that by assuming the coexistent positive and negative exchange between the nearest-neighbour spins in the linear trimer, this metamagnetism can be interpreted as a transition from antiferromagnetic to ferromagnetic exchange within each trimeric spin cluster. Although weak inter-cluster or inter-chain exchange to yield a long-range magnetic order is another possible and often attributed origin of metamagnetism in low-dimensional spin systems, this study demonstrates the significance of the exchange flip within each cluster in clustered spin networks.

Synthesis and analytical characterization of Ca-BTC metal organic framework

Metal Organic framework (MOF) has been a class of great interest during the past few years owing to its decidedly applicative, easily synthesized and improved characteristics. Ca-BTC MOF is synthesized by Hydrothermal technique and reported for the first time. Its structural morphology was analyzed using XRD, SEM, and EDS, showing the tetragonal crystal structure having grain size of 24.92 nm and purity of sample respectively. FTIR, Raman Spectroscopy ensures the metal organic framework between Calcium and the tri-carboxylic group. Photoluminescence measures the energy gap of 3.792 eV, showing approximately the semiconducting behavior of synthesized material. Zeta potential having value of -13.5 mV confirms the instability having good microbial activity and conductivity i.e 0.290 mS/cm which reveals important insights into its electrical properties.

An efficient synthesis and characterization of La@MOF-808: A promising strategy for effective arsenic ion removal from water

Addressing serious waterborne arsenic issues, for the first time, lanthanum-doped MOF-808 (La@MOF-808) has been developed to remove total arsenic (Total As) and arsenite [As(III)] from water. This study involves the solvothermal synthesis of La@MOF-808, its characterization via FTIR, XRD, TGA, and SEM, in which distinct physicochemical attributes were identified, and the adsorption capacity of arsenic ions. The saturated adsorption capacity of La@MOF-808 for Total As and As(III) reached 282.9 mg g-1 and 283.5 mg g-1, as compared to 229.7 mg g-1 and 239.1 mg g-1 for pristine MOF-808, respectively. XRD and ATR-FTIR analyses underscored the central roles of electrostatic interactions and hydroxyl groups in the pollutant adsorption process. The impact of temperature, concentration, pH, and exposure duration times on adsorption performance was thoroughly investigated. The Langmuir model showed the maximum adsorption capacities (qmax) of La@MOF-808 was 307.7 mg g-1 for Total As and 325.7 mg g-1 for As(III), surpassing those of MOF-808 adsorbent, which suggests that monolayer adsorption occurred. Optimal adsorption was observed in a pH range of 2.0-7.0, and thermodynamic studies classified the process as spontaneous and endothermic. The adsorbent retains high capacity across repeated cycles, outperforming many standard adsorbents. Lanthanum doping markedly enhances MOF-808's arsenic removal, underscoring its potential for water treatment.

Modulating Photoinduced Electron Transfer between Photosensitive MOF and Co(II) Proton Reduction Sites for Boosting Photocatalytic Hydrogen Production

Photocatalytic hydrogen production via water splitting is the subject of intense research. Photoinduced electron transfer (PET) between a photosensitizer (PS) and a proton reduction catalyst is a prerequisite step and crucial to affecting hydrogen production efficiency. Herein, three photoactive metal-organic framework (MOF) systems having two different PET processes where PS and Co(II) centers are either covalently bonded or coexisting to drive photocatalytic H2 production are built. Compared to these two intramolecular PET systems including CoII -Zn-PDTP prepared from the post-synthetic metalation toward uncoordinated pyridine N sites of Zn-PDTP and sole cobalt-based MOF Co-PDTP, the CoII (bpy)3 @Zn-PDTP system impregnated by molecular cocatalyst possessing intermolecular PET process achieves the highest H2 evolution rate of 116.8 mmol g-1 h-1 over a period of 10 h, about 7.5 and 9.3 times compared to CoII -Zn-PDTP and Co-PDTP in visible-light-driven H2 evolution, respectively. Further studies reveal that the enhanced photoactivity in CoII (bpy)3 @Zn-PDTP can be ascribed to the high charge-separation efficiency of Zn-PDTP and the synergistic intermolecular interaction between Zn-PDTP and cobalt complexes. The present work demonstrates that the rational design of PET process between MOFs and catalytic metal sites can be a viable strategy for the development of highly efficient photocatalysts with enhanced photocatalytic activities.

Cooperative Spin-State Switching and Vapochromism of Mononuclear Ni(II) Complexes by Pyridine Coordination/Decoordination

Two mononuclear Ni(II) complexes (1 and 2) have been found to display color changes upon coordination/decoordination of pyridine, resulting in their structural transformation between square-planar and octahedral geometries as well as a change in their spin state. Compound 1 changes between red (1r) and yellow (1y) upon exposure to or elimination of pyridine, while 2 undergoes a two-step transformation, changing orange 2o (S = 0) ⇄ gray 2g' (S = 1) → yellow 2y' (S = 1) depending on the reaction time. The first step (2o → 2g') takes less than 45 min, which is significantly faster than the previously reported reaction time of 1 day for a Ni(II) complex/pyridine vapor system. Compound 2o reacting with pyridine can be easily prepared by dispersing 2g in methanol instead of annealing at high temperatures (130 °C), which can be applied to develop chemical sensors for pyridine utilizing color changes and/or magnetic switching.

In Situ Oxidation of Pyridyl-Dihydrobenzoimidazoquinazoline and the Synthesis of a Highly Luminescent Cd(II) Coordination Polymer: A Promising Candidate for Mutagenic Nitroaromatic Detection and Device Fabrication

Pyridyl-substituted imidazoquinoline, a potent fluorescent framework, is advantageous to architect multifunctional coordination networks for sensing and fabricating emergent electrical conductors. In this work, a Cd(II)-based one-dimensional (1D) coordination polymer (1D CP), [Cd(glu)2(pbiq)2(H2O)]n (1), [H2glu = glutaric acid and pbiq = 4-(6-(pyridin-4-yl)benzo[4,5]imidazo[1,2-c]quinazoline)], has been structurally confirmed by single-crystal X-ray crystallography. The H-bonding and π···π interactions built a three-dimensional (3D) supramolecular structure that strongly emits at 416 nm in acetonitrile suspension. Potentially intrusive nitroaromatics (NAs) and trinitrophenol (TNP) selectively quench the strong emission of 1, and the highest quenching is noted in the case of TNP. A detection limit (limit of detection (LOD)) of 1.51 × 10-7 M for TNP is determined. The band gap (3.31 eV) of 1 recognizes semiconducting behavior, and an electronic device is fabricated. The correlation of current vs voltage (I-V plot) reveals a substantial non-ohmic electrical conductivity of 1 (Λ: 1.10 × 10-5 S m-1) along with a low energy barrier (ΦB: 0.69), and the series resistance (Rs) becomes 6.21 kΩ.

Creation of a Field-Induced Co(II) Single-Ion Magnet by Doping into a Zn(II) Diamagnetic Metal-Organic Framework

The combination of single-ion magnets (SIMs) and metal-organic frameworks (MOFs) is expected to produce new quantum materials. The principal issue to be solved in this regard is the development of new strategies for the synthesis of SIM-MOFs. This work demonstrates a new simple strategy for the synthesis of SIM-MOFs where a diamagnetic MOF is used as the framework into which the SIM sites are doped. 1, 0.5, and 0.2 mol% of the Co(II) ions are doped into the Zn(II) sites of [CH6 N3 ][ZnII (HCOO)3 ]. The doped Co(II) sites in the MOFs perform as SIM with a positive D term of zero-field splitting. The longest magnetic relaxation time is 150 ms (0.2 mol% Co) at 1.8 K under a static field of 0.1 T. Temperature dependency of the relaxation time suggests suppressing magnetic relaxation by reduction of spin-spin interaction upon doping in the rigid framework. Thus, this work represents a proof of concept for the creation of a single-ion doped magnet in the MOF. This simple synthetic strategy will be widely applied for the creation of quantum magnetic materials.

Gasoil removal from aqueous solution using magnetic metal-organic framework adsorbent based on the cellulosic fibrous of Prosopis farcta plant

Recently, the leakage of Gasoil and other petroleum substances into the seas, surface water, and wastewater has become a global problem; therefore, providing a solution to remove these pollutants seems vital. In the current research, we investigated the removal of floating Gasoil from aqueous solutions. First, the magnetic metal-organic framework was prepared as a new adsorbent based on the cellulosic fibrous of the Prosopis farcta plant (magnetic- cellulose@MIL-53(Fe) carbon aerogel). Using design of experiment, the effect of parameters pH, Gasoil concentration, and adsorbent weight on Gasoil removal were investigated. The adsorbent prepared under optimal parameters can remove 100% floating Gasoil from the aqueous solution. The adsorption capacity of the magnetic- cellulose@MIL-53 (Fe) carbon aerogel is 7.48 g.g-1, which is almost 100 times more than other Fe-based adsorbents. The study of the effect of time showed that the adsorption of Gasoil by the adsorbent is not dependent on time. Gasoil adsorption on magnetic- cellulose@MIL-53(Fe) carbon aerogel follows the Freundlich isotherm with a correlation coefficient of 0.9933. Thermodynamic factors Gibbs free energy, enthalpy, and entropy changes have been calculated. Accordingly, magnetic- cellulose @MIL-53(Fe) carbon aerogel has rapid separation and high stability, and it could be used as a good adsorbent to remove Gasoil from an aqueous solution. With good cycling stability of 86% retention of the initial adsorption value after ten adsorption/desorption cycles.

All-electron APW+lo calculation of magnetic molecules with the SIRIUS domain-specific package

We report APW+lo (augmented plane wave plus local orbital) density functional theory (DFT) calculations of large molecular systems using the domain specific SIRIUS multi-functional DFT package. The APW and FLAPW (full potential linearized APW) task and data parallelism options and the advanced eigen-system solver provided by SIRIUS can be exploited for performance gains in ground state Kohn-Sham calculations on large systems. This approach is distinct from our prior use of SIRIUS as a library backend to another APW+lo or FLAPW code. We benchmark the code and demonstrate performance on several magnetic molecule and metal organic framework systems. We show that the SIRIUS package in itself is capable of handling systems as large as a several hundred atoms in the unit cell without having to make technical choices that result in the loss of accuracy with respect to that needed for the study of magnetic systems.

Magnetic coupling modulation in meta-nitroxide-functionalized isoalloxazine magnets with redox-active units as efficient side-modulators

Magnetic conversion can be accomplished in a variety of ways, as organic molecules with switchable magnetic characteristics offer numerous technological applications. It is crucial to find magnetism-switchable systems because, in the field of organic magnetic materials, the redox-induced magnetic reversal is very simple to achieve and shows significant applications. Herein, we computationally design isoalloxazine-based diradicals through oxidizing N10 and adding a nitroxide to C8 as the spin source (i.e. 8-nitroxide-isoalloxazine 10-oxide, an m-phenylene-like nitroxide diradical expanded with a redox unit as a side-modulator) and its N1/N5-hydrogenated/protonated diradical derivatives and introducing substituents (-OH, -NH₂, and -NO₂) to C6. We demonstrate that the basically modified structure exhibits ferromagnetic (FM) characteristics with a magnetic coupling constant (J) of 561.3 cm^-1 calculated at the B3LYP/6-311+G(d,p) level, obeying the meta-phenylene-mediated diradical character, and dihydrogenation can lead to an AFM diradical with considerably large J (-976.1 cm^-1). Surprisingly, protonation at N1 or N5 can lead to distinctly different magnetic variations (561.3 → -1602.9 cm^-1 at N1 versus 561.3 → 379.1 cm^-1 at N5). Analyses indicate that small singlet-triplet energy gaps and small energy gaps between the highest occupied and lowest unoccupied molecular orbitals (HOMO, LUMO) of the closed shell singlet state are the key features of these isoalloxazine diradicals, and aromaticity variations, significant spin delocalization from the π-conjugated structure and spin polarization from the non-Kekule structure induced by modification are responsible for the magnetic conversion. Furthermore, the spin alternation rule, the singly occupied molecular orbital (SOMO) effect, and the SOMO-SOMO energy splitting of the triplet state are used to analyze these distinct variations. This work provides a novel understanding of the structures and characteristics of modified isoalloxazine diradicals, as well as essential details for the intricate design and characterization of new isoalloxazine-based potential organic magnetic switches.

Application of Nanomagnetic Metal-Organic Frameworks in the Green Synthesis of Nicotinonitriles via Cooperative Vinylogous Anomeric-Based Oxidation

In the current study, we synthesized a new nanomagnetic metal-organic framework Fe₃O₄@MIL-53(Al)-N(CH₂PO₃)₂ and characterized it using various techniques. This nanomagnetic metal-organic framework was used for the synthesis of a wide range of nicotinonitrile derivatives as suitable drug candidates by a four-component reaction of 3-oxo-3-phenylpropanenitrile or 3-(4-chlorophenyl)-3-oxopropanenitrile, ammonium acetate (NH₄OAc), acetophenone derivatives, and various aldehydes including those bearing electron-donating, electron-withdrawing, and halogen groups, which afforded desired products (27 samples) via a cooperative vinylogous anomeric-based oxidation (CVABO) mechanism under solvent-free conditions in excellent yields (68-90%) and short reaction times (40-60 min). Increasing the surface-to-volume ratio, easy separation of the catalyst using an external magnet, and high chemical and temperature stability are the advantages of the described nanomagnetic metal-organic frameworks.

Permanent Porosity in the Room-Temperature Magnet and Magnonic Material V(TCNE)2

Materials that simultaneously exhibit permanent porosity and high-temperature magnetic order could lead to advances in fundamental physics and numerous emerging technologies. Herein, we show that the archetypal molecule-based magnet and magnonic material V(TCNE)₂ (TCNE = tetracyanoethylene) can be desolvated to generate a room-temperature microporous magnet. The solution-phase reaction of V(CO)₆ with TCNE yields V(TCNE)₂·0.95CH₂Cl₂, for which a characteristic temperature of T* = 646 K is estimated from a Bloch fit to variable-temperature magnetization data. Removal of the solvent under reduced pressure affords the activated compound V(TCNE)₂, which exhibits a T* value of 590 K and permanent microporosity (Langmuir surface area of 850 m²/g). The porous structure of V(TCNE)₂ is accessible to the small gas molecules H₂, N₂, O₂, CO₂, ethane, and ethylene. While V(TCNE)₂ exhibits thermally activated electron transfer with O₂, all the other studied gases engage in physisorption. The T* value of V(TCNE)₂ is slightly modulated upon adsorption of H₂ (T* = 583 K) or CO₂ (T* = 596 K), while it decreases more significantly upon ethylene insertion (T* = 459 K). These results provide an initial demonstration of microporosity in a room-temperature magnet and highlight the possibility of further incorporation of small-molecule guests, potentially even molecular qubits, toward future applications.

Cd(II)/Mn(II)/Co(II)/Ni(II)/Zn(II) Coordination Polymers Built from Dicarboxylic Acid/Tetracarboxylic Acid Ligands: Their Structural Diversity and Fluorescence Properties

Six Cd(II)/Mn(II)/Co(II)/Ni(II)/Zn(II) coordination complexes are formulated as [Cd₂(X^2-)₂(μ₃-O)_2/3]_n (1), [Mn₂(X^2-)₂(μ₃-O)_2/3]_n (2), {[Co_1.5(Y^4-)_0.5(4,4'-bpy)_1.5(OH^-)]·2H₂O}_n (3), {[Ni(X^2-)(4,4'-bpy)(H₂O)₂]·4H₂O}_n (4), [Zn(m-bdc^2-)(bebiyh)]_n (5), and [Cd(5-tbia^2-)(bebiyh)]_n (6) (H₂X = 3,3'-(2,3,5,6-tetramethyl-1,4-phenylene) dipropionic acid. H₄Y = 2,2'-(2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene) dimalonic acid, bebiyh = 1,6-bis(2-ethyl-1H-benzo[d]imidazol-1-yl)hexane, m-H₂bdc = 1,3-benzenedicarboxylic acid, and 5-H₂tbia = 5-(tert-butyl)isophthalic acid) were obtained by hydrothermal reactions and structurally characterized. Complexes 1 and 2 have a 6-connected 3D architecture and with several point symbols of (3⁶·4⁶·5³). Complex 3 features a 5-connected 3D net structure with a point symbol of (5·6⁹). Complex 4 possesses a 4-connected 2D net with a vertex symbol of (4⁴·6²). Complex 5 is a 3-connected 2D network with a point symbol of (6³). Complex 6 is a (3,3)-connected 2D network with a point symbol of (6³)₂. In addition, complexes 1 and 4 present good photoluminescence behaviors. The electronic structures of 1 and 4 were investigated with the density functional theory (DFT) method to understand the photoluminescence behaviors.

Exploring Spin-Phonon Coupling in Magnetic 2D Metal-Organic Frameworks

Layered magnetic metal-organic frameworks (MOFs) are an emerging class of materials that can combine the advantages of both MOFs and 2D magnetic crystals. The recent discovery of large coercivity and long-range magnetic ordering up to 515 K in a layered MOF of general formula MCl₂(pyz)₂ (M = transition metal, pyz = pyrazine) offers an exciting versatile platform to achieve high-T_C magnetism at the 2D limit. In this work, we investigate the exfoliation feasibility down to the monolayer of VCl₂(pyz)₂ and CrCl₂(pyz)₂ by means of first-principles calculations. We explore their structural, electronic, magnetic and vibrational properties, as well as the effect of halide substitution. Then, we provide a full analysis of the spin-phonon coupling (SPC) in both 2D derivatives. Our calculations reveal a low SPC and thermal evolution of the magnetic exchange interactions and single-ion anisotropy mainly governed by low-frequency phonon modes. Finally, we provide chemical insights to improve the performance of these magnetic 2D MOFs based on the effective manipulation of the phonon modes that can present a major impact on their magnetic properties.

A rapid self-healing glassy polymer/metal-organic-framework hybrid membrane at room temperature

The development of repairable MOF-polymer hybrid materials will greatly extend their service life by repairing fractured parts on the spot; however, it is difficult for robust glassy polymers to self-heal below the glass transition temperature (T_g) as the polymer network is frozen. We herein report glassy polyMOF-RHP hybrid membranes by integrating lanthanide polyMOF (polyLnMOF) with randomly hyperbranched polymers (RHP) bearing a high density of hydrogen bonds. Since crystalline lanthanide MOFs act as multiconnected cross-linking agents and cross-link the interpenetrating polymer network, the obtained polyLnMOF-polymer membrane shows enhanced mechanical strength with a storage modulus of 3.09 GPa and a T_g up to 49 °C. Meanwhile, the high intersegment migration ability of the polyLnMOF-polymer network facilitates the exchange of hydrogen-bonded pairs even in the glassy state, leading to an instantaneous room-temperature self-healing ability. The polyLnMOF-polymer membranes inherit the ratiometric temperature-sensing behavior of pristine lanthanide MOFs, resulting in more processable temperature-sensing membranes. This work provides an appealing strategy for the design of mechanically robust, yet self-healing, MOF-polymer functional materials.

Synthesis, Molecular, and Supramolecular Structures of Two Azide-Bridged Cd(II) and Cu(II) Coordination Polymers

Two 1D coordination polymers were synthesized by reaction of two ligands, 2-amino-4-picoline (2A4Pic) and quinoline-6-carboxylic acid (Qu-6-COOH) with two metal (II) nitrate (M = Cd and Cu) in the presence of azide as a linker. The synthesized metal complexes [Cd(2A4Pic)2(N3)2]n; (1) and [Cu(Qu-6-COO)(N3)(H2O)]n; (2) were isolated in single crystals and their X-ray structures revealed a 1D polymeric structure. Due to symmetry considerations, the asymmetric formula is half a [Cd(2A4Pic)2(N3)2] unit for 1 and one [Cu(Qu-6-COO)(N3)(H2O)] unit for 2. In complex 1, the Cd(II) is hexa-coordinated with two 2A4Pic molecules and four μ(1,1) azide units. Hence, the CdN6 coordination environment has a slightly distorted octahedral geometry. In 2, the Cu(II) is hexa-coordinated with three different ligands (Qu-6-COO¯, H2O and μ(1,1) N3¯) where all are connectors between the crystallographically related Cu(II) sites. Additionally, complex 2 distorted CuN2O4 octahedral geometry. In both complexes, the polymer arrays are connected by N…H hydrogen bonds and π–π stacking interactions. Based on Hirshfeld analysis, the percentages of N…H contacts are 43.1 and 27.4% for 1 and 2, respectively, while %C...C are 5.6 and 9.3%, respectively. Analysis of Cu-N, Cu-O, and Cd-N bonds using DFT calculations showed predominantly closed-shell coordination interactions with little covalent characters. Additionally, the negatively charged ligand groups were found to compensate the positive charge of the central metal ion to a larger extent than the electrically neutral ligands.

Solvent-free mechanochemical multicomponent preparation of 4H-pyrans catalyzed by Cu2(NH2-BDC)2(DABCO) metal-organic framework

4H-pyrans have been prepared through a mechanochemical multicomponent reaction (MCR) of different aldehydes, malononitrile, and various 1,3-dicarbonyl compounds, catalyzed by an amine-functionalized metal-organic framework (MOF) Cu₂(NH₂-BDC)₂(DABCO) as a heterogeneous catalyst with good to excellent yields.

The Versatility of Ethylene Glycol to Tune the Dimensionality and Magnetic Properties in DyIII-Anilato-Based Single-Ion Magnets

We exploit the high versatility of the solvent ethylene glycol (eg = CH₂OH-CH₂OH) acting as a ligand with three different coordination modes: terminal (κO), chelate (κ²O,O'), and bridge (1κO,2κO') to prepare a novel family of six different coordination polymers with Dy^III and three different anilato ligands (3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone dianion = C₆O₄X₂^2-, with X = H, Cl, and Br). With the X = H derivative (dhbq^2-), we have prepared [Dy₂(dhbq)₃(eg)₂(μ-eg)]·4eg·2H₂O (1), a 3D diamond-like network with a chelate and bridging eg molecules. With the X = Cl derivative (chloranilato), we have prepared [Dy₂(C₆O₄Cl₂)₃(eg)₄]·2eg·H₂O (2) and [Dy₂(C₆O₄Cl₂)₃(μ-eg)(H₂O)₄]·2eg·7H₂O (3). Compound 2 has a 2D (6,3)-gon brick-wall lattice and contains a chelate and a terminal eg molecule. Compound 3 has a 3D diamond-like topology as 1, although now the chelate eg has been replaced by two water molecules. Finally, with the X = Br derivative (bromanilato), we have obtained [Dy₂(C₆O₄Br₂)₃(eg)₂(CH₃OH)₂]·2eg·4CH₃OH (4), [Dy₂(C₆O₄Br₂)₃(eg)₄]·4eg (5), and [Dy₂(C₆O₄Br₂)₃(eg)₃(H₂O)]·2eg·H₂O (6). Compound 4 has a 2D (6,3)-gon herringbone topology and contains a chelate eg and a MeOH molecule. Compounds 5 and 6 have a 2D (6,3)-gon brick-wall topology with a chelate and a terminal eg molecules (in 5 and in one of the two independent Dy centers of 6). The other Dy center in 6 has a chelate eg and a water molecule. All the compounds show slow relaxation of the magnetization at low temperatures (in compounds 1, 2, and 5 with no applied DC field). The magnetization of compounds 1-6 relaxes through Orbach and direct mechanisms when a DC field is applied and through an Orbach and/or quantum tunneling mechanism when no DC field is applied.

Noncentrosymmetric Supramolecular Hydrogen-Bonded Assemblies Based on Achiral Pyrazine-Bridged Zinc(II) Coordination Polymers with Pyrazinedione Derivatives

Reaction of M(OAc)2·xH2O (M, x = Zn, 2 and Co, 4), 1,4-dihydro-5,6-dicyano-2,3-pyrazinedione (H2CN2pyzdione), and pyrazine (pyz) affords two compounds of the same molecular formula {[M(H2O)6][M(CN2pyzdione)2(pyz)]·6H2O}n (M = Zn for 1 and Co for 2) in which discrete units of [M(H2O)6]2+ are linked to one-dimensional chains of [M(CN2pyzdione)2(pyz)]2– via multiple O–H···O hydrogen-bonding interactions and M2+-bound H2O molecules in [M(H2O)6]2+ also serve as linkers of hydrogen-bonded interstitial H2O molecules. Remarkably, 1 crystallizes in the monoclinic crystal system, the similar crystal system and unit cell parameters as 2, but with a space group distinct from 1 and 2, i.e., 1 is the noncentrosymmetric space group C2, whereas 2 is the centrosymmetric space group C2/m. This polar structure for 1 is induced by the presence of alternating arrangements of distinguishable two axial Zn–N bonds within [Zn(CN2pyzdione)2(pyz)]2– chains. Indeed, solid-state circular dichroism spectra of 1 exhibit significant Cotton effects, as evidenced by the polar space group C2. Moreover, these Cotton effects show clear temperature-dependence depending on contents of H2O molecules of 1.

Inter-layer magnetic tuning by gas adsorption in π-stacked pillared-layer framework magnets

Magnetism of layered magnets depends on the inter-layer through-space magnetic interactions (J NNNI). Using guest sorption to address inter-layer pores in bulk-layered magnets is an efficient approach to magnetism control because the guest-delicate inter-layer distance (l trans) is a variable parameter for modulating J NNNI. Herein, we demonstrated magnetic changes induced by the adsorption of CO2, N2, and O2 gases in various isostructural layered magnets with a π-stacked pillared-layer framework, , (M = Co, 1, Fe, 2, Cr, 3; Cp* = η5-C5Me5; 2,3,5,6-F4PhCO2 - = 2,3,5,6-tetrafluorobenzoate; TCNQ = 7,7,8,8-tetracyano-p-quinodimethane). Each compound had almost identical adsorption capability for the three types of gases; only CO2 adsorption was found to have a gated profile. A breathing-like structural modulation involving the extension of l trans occurred after the insertion of gases into the isolated pores between the [Ru2]2-TCNQ ferrimagnetic layers, which is more significant for CO2 than for O2 and N2, due to the CO2-gated transition. While adsorbent 1 with M = Co (S = 0) was an antiferromagnet with T N = 75 K, 1⊃CO2 was a ferrimagnet with T C = 76 K, whereas 1⊃N2 and 1⊃O2 were antiferromagnets with T N = 68 K. The guest-insertion effect was similarly confirmed in 2 and 3, and was characteristically dependent on the type of sandwiched spin in as M = Fe (S = 1/2) and Cr (S = 3/2), respectively. This study reveals that common gases such as CO2, O2, and N2 can serve as crucial triggers for the change in magnetism as a function of variable parameter l trans.

Aerogel-Based Single-Ion Magnets: A Case Study of a Cobalt(II) Complex Immobilized in Silica

The chemical immobilization of cobalt(II) ions in a silica aerogel matrix enabled the synthesis of the first representative example of aerogel-based single-ion magnets. For the synthesis of the lyogels, methyl-trimethoxysilane and N-3-(trimethoxysilyl)propyl ethylenediamine were co-hydrolyzed, then the ethylenediamine groups that were immobilized on the silica matrix enabled the subsequent binding of cobalt(II) ions. Lyogels with various amounts of ethylenediamine moieties (0.1-15 mol %) were soaked in isopropanol solutions of cobalt(II) nitrate and further supercritically dried in carbon dioxide to obtain aerogels with a specific surface area of 210-596 m²·g^-1, an apparent density of 0.403-0.740 cm³·g^-1 and a porosity of 60-78%. The actual cobalt content in the aerogels was 0.01-1.50 mmol per 1 g of SiO₂, which could easily be tuned by the concentration of ethylenediamine moieties in the silica matrix. The introduction of cobalt(II) ions into the ethylenediamine-modified silica aerogel promoted the stability of the diamine moieties at the supercritical drying stage. The molecular prototype of the immobilized cobalt(II) complex, bearing one ethylenediamine ligand [Co(en)(MeCN)(NO₃)₂], was synthesized and structurally characterized. Using magnetometry in the DC mode, it was shown that cobalt(II)-modified silica aerogels exhibited slow magnetic relaxation in a nonzero field. A decrease in cobalt(II) concentration in aerogels from 1.5 mmol to 0.14 mmol per 1 g of SiO₂ resulted in a weakening of inter-ion interactions; the magnetization reversal energy barrier likewise increased from 4 to 18 K.

Graphene-Based Metal-Organic Framework Hybrids for Applications in Catalysis, Environmental, and Energy Technologies

Current energy and environmental challenges demand the development and design of multifunctional porous materials with tunable properties for catalysis, water purification, and energy conversion and storage. Because of their amenability to de novo reticular chemistry, metal-organic frameworks (MOFs) have become key materials in this area. However, their usefulness is often limited by low chemical stability, conductivity and inappropriate pore sizes. Conductive two-dimensional (2D) materials with robust structural skeletons and/or functionalized surfaces can form stabilizing interactions with MOF components, enabling the fabrication of MOF nanocomposites with tunable pore characteristics. Graphene and its functional derivatives are the largest class of 2D materials and possess remarkable compositional versatility, structural diversity, and controllable surface chemistry. Here, we critically review current knowledge concerning the growth, structure, and properties of graphene derivatives, MOFs, and their graphene@MOF composites as well as the associated structure-property-performance relationships. Synthetic strategies for preparing graphene@MOF composites and tuning their properties are also comprehensively reviewed together with their applications in gas storage/separation, water purification, catalysis (organo-, electro-, and photocatalysis), and electrochemical energy storage and conversion. Current challenges in the development of graphene@MOF hybrids and their practical applications are addressed, revealing areas for future investigation. We hope that this review will inspire further exploration of new graphene@MOF hybrids for energy, electronic, biomedical, and photocatalysis applications as well as studies on previously unreported properties of known hybrids to reveal potential "diamonds in the rough".

"Caught in the Act" @ disruption of A-ET-E process in the recognition of F- by a lamellar EuIII-MOF in heterogeneous manner with logic gate construction: From protagonist idea to implementation world

Development of cost-effective and reliable fluoride sensor for assessing water quality of natural water samples is of immense importance in developing countries as they can provide an easy platform for safeguarding human health. These sensors should be as simple as possible to be fabricated locally by layman. In this context, Eu^III-based MOFs provide trustable platform with bright luminescence in the visible region due to their absorbance-energy transfer-emission (A-ET-E) process. Herein the designed synthesis of a 2D porous coordination polymer, Eu@CMERI, has been carried out following a solvothermal reaction route. The compound shows selective "turn-off" sensing of fluoride in heterogeneous manner from purely aqueous phase and other biological matrices with a detection limit of 28.4 ppb and it carries enormous importance for drinking water analysis under internal regulations. Prohibition of A-ET-E cycle of the Eu^III-MOF is proposed to be the prime reason for fluorescence quenching upon interaction with F^-. DFT studies also revealed that lowest △E_HOMO-LUMO and highest chemical potential value (μ) of F^- are the driving forces for selectivity of Eu^III-MOF towards the targeted anion. The high stability of the porous frameworks along with its interesting sensing features, including fast response and wide linear detection range etc. instigated us not to restrict the chemistry of Eu^III-MOFs at protagonist idea rather to explore its application to real-world analysis. Based on the fluorescence signal exhibited by the targeted analyte, an integrated AND-OR logic gate has also been fabricated which depicts its applicability in molecular electronics. In view of the modular design principle of our polymeric probe, the proposed strategy could open a new horizon to construct powerful sensing materials for ultrafast detection of other important pollutants in the domain of supramolecular chemistry in coming days.