Two Unusual Nanocage-Based Ln-MOFs with Triazole Sites: Highly Fluorescent Sensing for Fe3+ and Cr2 O7 2- , and Selective CO2 Capture

Dual Stimulus Responsive GO-Modified Tb-MOF toward a Smart Coating for Corrosion Detection

Smart-sensing coatings that exhibit multistimulus response, rapid indication, and reusability are in urgent need to effectively enhance the practicability of coatings while accurately detecting metal corrosion. In this work, a reusable corrosion self-reporting coating with multiple pH and Fe3+ stimulus responses was first constructed by the integration of a composite fluorescent probe into the resin matrix. This composite sensor was constructed by combining a lanthanide metal-organic framework (Ln-MOF) based on terbium and trimeric acid (H3BTC) with graphene oxide (GO) nanosheets (GO@Tb-BTC). The incorporation of GO formed a sea-urchin-like structure, thereby increasing the specific surface area and active sites of the probe. The coatings were characterized by using electrochemical impedance spectroscopy (EIS), visual observation, and fluorescence spectrophotometry. The surface morphology, wettability, and adhesion of the coating samples were analyzed using SEM, XPS, hydrostatic contact angle test, and an adhesion test. EIS measurements in 3.5 wt % NaCl solution for 72 h demonstrated the superior corrosion protection performance of the 0.3 wt %/GO@Tb-BTC/WEP coating compared to blank coating, with the charge-transfer resistance reaching 4.33 × 107 Ω·cm2, which was 9.5 times higher than that of the pure coating. The bright green fluorescence of GO@Tb-BTC/WEP coating exhibited a turn-off response when there was an excess of OH-/H+, but it demonstrated a reversible turn-on fluorescence when the ambient pH returned to neutral. Furthermore, such Fe3+-triggered fluorescence quenching responded to concentrations as low as 1 × 10-6 M. The fluorescence quenching rate of both intact and damaged coatings surpassed that of visual and EIS detection methods. Significantly, the fluorescence in scratches was effectively quenched within 25 min using 0.3 wt %/GO@Tb-BTC/WPU coating for visual observation. GO@Tb-BTC demonstrated exceptional corrosion self-reporting capabilities in both epoxy and polyurethane systems, making it a versatile option beyond single-coating applications.

Luminescent Papers with Asymmetric Complexes of Eu(III) and Tb(III) in Polymeric Matrices and Suggested Combinations for Color Tuning

Complexes of lanthanide ions, such as Eu(III) (red light emission) and Tb(III) (green light emission), with proper ligands can be highly luminescent and color-tunable, also attaining yellow and orange emission under UV radiation. The ligands employed in this work were poly(sodium acrylate), working as polymeric matrix, and 1,10-phenanthroline, taking advantage of its antenna effect. Possibilities of color display were further enhanced by incorporating a cationic polyfluorene with blue emission. This strategy allowed for obtaining cyan and magenta, besides the aforementioned colors. Uncoated cellulose paper was impregnated with the resulting luminescent inks, observing a strong hypsochromic shift in excitation wavelength upon drying. Hence, while a cheap UV-A lamp sufficed to reveal the polyfluorene's blue emission, shorter wavelengths were necessary to visualize the emission due to lanthanide ions as well. The capacity to reveal, with UV-C radiation, a full-color image that remains invisible under natural light is undoubtedly useful for anti-counterfeiting applications. Furthermore, both lanthanide ion complexes and polyfluorenes were shown to have their luminescence quenched by Cu(II) ions and nitroarenes, respectively.

Highly Luminescent Europium(III) Complexes in Solution and PMMA-Doped Films for Bright Red Electroluminescent Devices

This paper reports the synthesis, structure, photophysical, and optoelectronic properties of five eight-coordinate Europium(III) ternary complexes, namely, [Eu(hth)₃(L)₂], bearing 4,4,5,5,6,6,6-heptafluoro-1-(2-thienyl)-1,3-hexanedione (hth) as a sensitizer and L = H₂O (1), dpso (diphenyl sulphoxide, 2), dpsoCH₃ (4,4'-dimethyl diphenyl sulfoxide, 3), dpsoCl (bis(4-chlorophenyl)sulphoxide, 4), and tppo (triphenylphosphine oxide, 5) as co-ligands. The NMR and the crystal structure analysis confirmed the eight-coordinate structures of the complexes in solution and in a solid state. Upon UV-excitation on the absorption band of the β-diketonate ligand hth, all complexes showed the characteristic bright red luminescence of the Europium ion. The tppo derivative (5) displayed the highest quantum yield (up to 66%). As a result, an organic light-emitting device, OLED, was fabricated with a multi-layered structure-ITO/MoO₃/mCP/SF3PO:[complex 5] (10%)/TPBi:[complex 5] (10%)/TmPyPB/LiF/Al-using complex 5 as the emitting component.

Development of Cationic Benzimidazole-Containing UiO-66 through Step-by-Step Linker Modification to Enhance the Initial Sorption Rate and Sorption Capacities for Heavy Metal Oxo-Anions

Effective and rapid capture of heavy metal oxo-anions from wastewater is a fascinating research topic, but it remains a great challenge. Herein, benzimidazole and -CH₃ groups were integrated into UiO-66 in succession via a step-by-step linker modification strategy that was performed by presynthesis modification (to give Bim-UiO-66) and subsequently by postsynthetic ionization (to give Bim-UiO-66-Me). The UiO-66s (UiO-66, Bim-UiO-66, and Bim-UiO-66-Me) were applied in the removal of heavy metal oxo-anions from water. The two benzimidazole derivatives (Bim-UiO-66 and Bim-UiO-66-Me) showed much better performance than UiO-66, as both the initial sorption rate and sorption capacities decreased in the order Bim-UiO-66-Me > Bim-UiO-66 > UiO-66. The maximum performances of Bim-UiO-66 are 5.1 and 1.7 times those of UiO-66. Remarkably, Bim-UiO-66-Me shows 7.5 and 3.0 times better performance than UiO-66. The higher absorptivity of cationic Bim-UiO-66-Me compared with UiO-66 can be attributed to a strong Coulombic interaction as well as an anion-π interaction and hydrogen bonding between the benzimidazolium functional group and heavy metal oxo-anions. The as-synthesized Bim-UiO-66-Me not only provides a promising candidate for application in removal of heavy metal oxo-anions in wastewater treatment but also opens up a new strategy for the design of high-performance adsorbents.

Current status and prospects of metal-organic frameworks for bone therapy and bone repair

With the development of society, traumatic bone defects caused by accidents, diseases and surgeries have become common, eventually resulting in an increase in bone defects. The treatment of bone defects is characterized by a long period of treatment, high cost and uncontrollable outcomes. Also, it results in complications such as infection and bone discontinuity. Hence, due to this situation, the physical, mental and financial aspects of the patient are severely affected. What's more, such outcomes pose a challenge to orthopaedic surgeons. As a result, bone therapy and bone repair have become a hot topic of interest. In repairing bone defects, materials other than autogenous bone are still unable to provide good biocompatibility, osteogenesis, osteoconductivity and osteoinduction properties at the same time. In addition, the scarcity of autologous bone sources has forced the search for new autologous bone replacement materials. Metal organic frameworks (MOFs) are a new class of developed functional materials that have been widely used in the biomedical field during the recent years due to their porous nature, large specific surface area and diverse structures. With the progress in the investigation into bone treatment and repair, more and more investigators are using MOFs in bone therapy and bone repair. With these viewpoints, in the present perspective, the use of MOFs in bone therapy and bone repair has been summarized, and an insight into the future of MOFs in bone therapy and bone repair has been provided.

Porous Carbons Derived from Desiliconized Rice Husk Char and Their Applications as an Adsorbent in Multivalent Ions Recycling for Spent Battery

Recycling of spent lithium-ion batteries (LIBs) has attracted increasing attentions recently on account of continuous growth demand for corresponding critical metals/materials and environmental requirement of solid waste disposal. In this work, rice husk as one of the most abundant renewable fuel materials in the world was used to prepare rice husk char (RC) and applied to recycle multivalent ions in waste water from hydrometallurgical technology dispose of spent LIBs. Rice husk char with specific surface area and abundant pores was obtained via pickling and desilication process (DPRC). The structural characterization of the obtained rice husk char and its adsorption capacity for multivalent ions in recycled batteries were studied. XRD, TEM, SEM, Raman, and BET were used for the characterization of the raw and the modified samples. The results show rice husk chars after desilication has more flourishing pore structure and larger pore size about 50–60 nm. Meanwhile, after desilication, the particle size of rice husk char decreased to 31.392 μm, and the specific surface area is about 402.10 m2/g. Its nitrogen adsorption desorption curve (BET) conforms to the type IV adsorption isotherm with H3 hysteresis ring, indicating that the prepared rice husk char is a mesoporous material. And the adsorption capacity of optimized DPRC for Ni, Co, and Mn ions is 7.00 mg/g, 4.84 mg/g, and 2.67 mg/g, respectively. It also demonstrated a good fit in the Freundlich model for DPRC-600°C, and a possible adsorption mechanism is proposed. The study indicates biochar materials have great potential as an adsorbent to recover multivalent ions from spent batteries.

Heterometallic Dual-Liganded AE-Ln-CPs Luminescent Probes for Efficient Sensing of Fe(III) Ions

Iron ion is widely present in the environment and in biological systems, and are indispensable trace elements in living organisms, so development of an efficient and simple sensor for sensing Fe(III) ions has attracted much attention. Here, six heterometallic AE-Ln coordination polymers (CPs) [Ln₂ (pda)₄(Hnda)₂Ca₂(H₂O)₂]·MeOH (Ln = Eu (1), Tb (2); H₂pda = 2,6-pyridinedicarboxylic acid, H₂nda = 2,3-naphthalenedicarboxylic acid), [Ln (pda)₂ (nda)AE₂(HCOO)(H₂O)] (AE = Sr, Ln = Eu (3), Tb (4); AE = Ba, Ln = Eu (5), Tb (6)) with two-dimensional (2D) layer structures were synthesized by hydrothermal method. All of them were characterized by elemental analysis, XRD, IR, TG, as well as single crystal X-ray diffraction. They all show infinite 2D network structure, where complexes 1 and 2 are triclinic with space group of P1¯, while 3-6 belong to the monoclinic system, space group P2_1/n. The solid-state fluorescence lifetimes of complexes 1, 3 and 5 are τ_obs1 = 1930.94, 2049.48 and 2,413.04 µs, respectively, and the quantum yields Ф_total are 63.01, 60.61, 87.39%, respectively, which are higher than those of complexes 2, 4 and 6. Complexes 1-6 all exhibited efficient fluorescence quenching response to Fe³⁺ ions in water, and were not interfered by the following metal ions: Cu²⁺, Cd²⁺, Mg²⁺, Ni²⁺, Co²⁺, Ca²⁺, Ba²⁺, Sr²⁺, Li⁺, Na⁺, K⁺, Al³⁺, Fe²⁺, Pb²⁺, Cr³⁺, Mn²⁺ and Zn²⁺. The quenching coefficient K_SV for complexes 1-6 is 1.41 × 10⁵ M⁻¹, 7.10 × 10⁴ M⁻¹, 1.70 × 10⁵ M⁻¹, 1.57 × 10⁵ M⁻¹, 9.37 × 10⁴ M⁻¹, 1.27 × 10⁵ M⁻¹, respectively. The fluorescence quenching mechanism of these complexes towards Fe³⁺ ions was also investigated. It is possible that the weak interaction formed between the complexes and the Fe³⁺ ions reduce the energy transfer from the ligand to the Ln³⁺ ion, producing the emission burst effect. This suggests that complexes 1-6 can be candidate for efficient luminescent sensor of Fe³⁺.

Efficient photodegradation of dyes by a new 3D Cd(II) MOF with rare fsh topology

Metal–organic frameworks (MOFs) can be regarded as 3D coordination polymers that adopt ordered porous structures and possess abundant active sites, which make them promising photocatalysts for the degradation of organic...

Impact of N-donor auxiliary ligands on two new Co(II)-based MOFs with N-heterocyclic ligands and magnetism study

Two new cobalt(II) MOFs, namely [Co2(L)2(4,4′-bipy)]n (1) and {[Co(L)(dib)0.5(H2O)2]·H2O}n (2) were obtained by the self-assembly of Co(NO3)2·6H2O with V-shaped 2,4-[6-(4-carboxyphenyl)pyrazin-2-yl]benzoic acid (H2L) in the presence of two bridging auxiliary N-donor...

Recyclable europium functionalized metal-organic fluorescent probe for detection of tryptophan in biological fluids and food products

An europium functionalized metal-organic fluorescent probe, Eu³⁺@UiO-66-FDC was constructed by post-synthetic modification through coordination interactions. Eu³⁺@UiO-66-FDC displayed high selectivity and sensitivity toward Tryptophan (Trp) among all the 20 natural amino acids and other general compounds in food and biological samples, with a wide linear concentration range (0-1000 μM), low detection limit (0.29 μM), and a rapid response (<1 min). Besides, this probe was utilized to detect Trp in rabbit blood serum and milk samples with good recoveries, which were verified by high-performance liquid chromatography (HPLC). Notably, this fluorescent probe proved to be a recyclable material. Hence, this work provides a reliable and recyclable fluorescent probe applicable toward the detection of Trp in biological fluids and/or food products.

Recent advances in MOF-based nanoplatforms generating reactive species for chemodynamic therapy

Still today, cancer remains a threat to human health. Possible common treatments to cure this disease include chemotherapy (CT), radiotherapy (RT), photothermal therapy (PTT), and surgical resection, which give unreasonable results because of their limited efficiency and also lead to side-effects. Hence, different strategies are now being exploited to not only enhance the efficiency of these traditional therapeutic methods or treat the tumor cells but also curtail the side effects. A latest method with authentic proof of chemodynamic therapy (CDT) utilizing the Fenton reaction is now gaining importance. This approach, which is developed based on the high level of hydrogen peroxide (H2O2) in a tumor microenvironment (TME), can be used to catalyze the Fenton reaction to generate cancer cell-killing reactive oxygen species (ROS). The selection of materials is extremely important and nanomaterials offer the most likely method to facilitate CDT. Among various materials, metal-organic frameworks (MOFs) which have been extensively applied in medical areas are regarded as a promising material and possess potential for the next generation of nanotechnology. This review focuses on summarizing the use of MOFs in CDT and their synergetic therapeutics as well as the challenges, obstacles, and development.

Devising Mixed-Ligand Based Robust Cd(II)-Framework From Bi-Functional Ligand for Fast Responsive Luminescent Detection of Fe3+ and Cr(VI) Oxo-Anions in Water With High Selectivity and Recyclability

Environmental issue related applications have globally surfaced as hottest areas of research, wherein luminescent metal-organic frameworks (LMOFs) with functionalized pores put unique signature in real-time monitoring of multiple classes of toxic compounds, and overcome many of the challenges of conventional materials. We report a two-fold interpenetrated, mixed-ligand Cd(II)-organic framework (CSMCRI-11) [Cd_1.5(L)₂(bpy)(NO₃)]·DMF·2H₂O (CSMCRI = Central Salt and Marine Chemical Research Institute, HL = 4- (1H-imidazol-1-yl)benzoic acid, bpy = 4,4'-bipyridine) that exemplifies bipillar-layer structure with two different Cd(II) nodes, and displays notable robustness in diverse organic solvents and water. Intense luminescence signature of the activated MOF (11a) is harnessed in extremely selective and fast responsive sensing of Fe³⁺ ions in aqueous phase with notable quenching constant (1.91 × 10⁴ M^-1) and impressive 166 ppb limit of detection (LOD). The framework further serves as a highly discriminative and quick responsive scaffold for turn-off detection of two noxious oxo-anions (Cr₂O₇ ^2- and CrO₄ ^2-) in water, where individual quenching constants (CrO₄ ^2-: 1.46 × 10⁴ M^-1; Cr₂O₇ ^2-: 2.18 × 10⁴ M^-1) and LOD values (CrO₄ ^2-: 179 ppb; Cr₂O₇ ^2-: 114 ppb) rank among best sensory MOFs for aqueous phase detection of Cr(VI) species. It is imperative to stress the outstanding reusability of the MOF towards detection of all these aqueous pollutants, besides their vivid monitoring by colorimetric changes under UV-light. Mechanism of selective quenching is comprehensively investigated in light of absorption of the excitation/emission energy of the host framework by individual studied analyte.

Selective and recyclable tandem sensing of PO43- and Al3+ by a water-stable terbium-based metal-organic framework

Herein, a luminescent water-stable terbium-based metal-organic framework (MOF) {[Tb(Cmdcp)(H₂O)₃]₂(NO₃)₂·5H₂O}_n (1, H₃CmdcpBr = N-carboxymethyl-(3,5-dicarboxyl)pyridinium bromide) has been synthesized and used for the recyclable sensing of PO₄^3- and Al³⁺ in tandem. MOF 1 acts as a fluorescent sensor for PO₄^3- by the luminescence "turn-off" mechanism with high selectivity over other anions, such as F^-, Cl^-, Br^-, I^-, NO₃^-, H₂PO₄^-, HSO₄^-, HCO₃^-, HSO₃^-, SO₄^2-, CO₃^2- and HPO₄^2-. The formed PO₄^3-@1 complex further acts as the Al³⁺ sensor with the luminescence "turn-on" mechanism, also with high selectivity over diverse inorganic cations of Fe²⁺, Mn²⁺, Co²⁺, Ni²⁺, Hg²⁺, Na⁺, K⁺, Li⁺, Ag⁺, Mg²⁺, Ca²⁺, Cd²⁺, Pb²⁺, Cu²⁺, and Zn²⁺. The detection process for both PO₄^3- and Al³⁺ can be directly observed with naked eyes under the UV light at 365 nm. The detection limits for PO₄^3- and Al³⁺ are 1.1 μM and 6.6 μM, respectively. Such a sensing cycle is further transferable to urine and serum samples with a satisfactory near-quantitative recovery, highlighting its good potential in biologically relevant applications.

Four structural diversity MOF-photocatalysts readily prepared for the degradation of the methyl violet dye under UV-visible light

The photocatalytic results demonstrated that all of them displayed efficient photocatalytic performances towards the degradation of methyl violet. The mechanism has been proposed.

Recent progress in lanthanide metal–organic frameworks and their derivatives in catalytic applications

Research progress in lanthanide metal–organic frameworks and their derivatives in the field of catalysis has been presented on the basis of different organic reactions.

Syntheses of a series of lanthanide metal–organic frameworks for efficient UV-light-driven dye degradation: experiment and simulation

Three Ln-MOFs show unique 3,8-connected 3D networks and have been used as photocatalysts for the degradation of organic dye methyl violet under UV light.

Efficient photocatalytic degradation of methyl violet using two new 3D MOFs directed by different carboxylate spacers

Both the MOFs proved to be good candidates for the photocatalytic degradation of methyl violet. The mechanism of these photocatalytic degradations is discussed.

Two new luminescent Cd(ii)-based coordination polymers by regulating the asymmetrical tetracarboxylate and auxiliary ligands displaying high sensitivity for Fe3+ and CrO42−

The results showed luminescence spectra with emission intensities significantly quenched towards Fe³⁺ and CrO₄²⁻. The low concentrations of the two ions indicate high sensitivities of the synthesized compounds towards analytes.

Recent advances in cell membrane coated metal-organic frameworks (MOFs) for tumor therapy

In improving the tumor-targeting ability of metal-organic frameworks (MOFs) for tumor therapy and avoiding the clearance as well as capture by the immune system, there are still several challenges, which limit the development and bio-applications of MOFs. To overcome these challenges, various targeted modification strategies have been proposed. Amongst all the strategies, a promising cell membrane coating method has been explored and utilized for the syntheses of new cell membrane biomimetic MOFs (CMMs). Through such coating, various source cell membranes (e.g., red blood cell, immune cell, cancer cell, platelet, and fusion cell membranes) can be endowed with excellent properties such as long blood circulation, immune escape, and targeting ability. In the presented perspective, the synthetic method, characterization, and research progress in tumor therapy based on CMMs have been summarized. This is because, like many other technologies, the cell membrane coating technology also has several challenges to overcome. Hence, addressing and overcoming such challenges will promote and extend the bio-applications of MOFs which in the future may become a prospective carrier for cancer nano-medicine. Finally, the prospects and challenges of utilizing CMMs for tumor therapy have been discussed.

The construction of a multifunctional luminescent Eu-MOF for the sensing of Fe3+, Cr2O72− and amines in aqueous solution

A 3D Eu(iii)-based metal–organic framework has been synthesized as a multiresponsive chemosensor for highly sensitive and selective detection of Fe3+, Cr2O72− and amines in water.

Pyridinyl Conjugate of UiO-66-NH2 as Chemosensor for the Sequential Detection of Iron and Pyrophosphate Ion in Aqueous Media

A new chemosensor UiO-66-N-Py (Py = 2-methinepyridine, N = imine nitrogen) based on isoreticular UiO-66 (University of Oslo) Metal–Organic Framework (MOF) containing 2-methinepyridine functionalized organic linker was solvothermally synthesized and characterized. This UiO-66-N-Py was very selective and sensitive for detecting the Fe3+ ion and sequential detection of the pyrophosphate (PPi) anion. The limits of detection for the Fe3+ ion and PPi were calculated to be 10 ppb (0.19 μM) and 50 ppb (0.3 μM), respectively. The quenching constant Ksv for Fe3+ and the binding constant for PPi were 1.4 × 105 M−1 and 1.7 × 105 M−1, respectively. The functionalization of UiO-66-NH2 with 2-methinepyridine enhanced its fluorescence emission properties and introduced more binding sites for the analytes. We additionally studied the interaction of the sensor and the analytes with Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). This chemosensor also demonstrated a regenerative emission property without loss in the detection ability for six consecutive cycles.

Recent Progress on Luminescent Metal-Organic Framework-Involved Hybrid Materials for Rapid Determination of Contaminants in Environment and Food

The high speed of contaminants growth needs the burgeoning of new analytical techniques to keep up with the continuous demand for monitoring and legislation on food safety and environmental pollution control. Metal-organic frameworks (MOFs) are a kind of advanced crystal porous materials with controllable apertures, which are self-assembled by organic ligands and inorganic metal nodes. They have the merits of large specific surface areas, high porosity and the diversity of structures and functions. Latterly, the utilization of metal-organic frameworks has attracted much attention in environmental protection and the food industry. MOFs have exhibited great value as sensing materials for many targets. Among many sensing methods, fluorometric sensing is one of the widely studied methods in the detection of harmful substances in food and environmental samples. Fluorometric detection based on MOFs and its functional materials is currently one of the most key research subjects in the food and environmental fields. It has gradually become a hot research direction to construct the highly sensitive rapid sensors to detect harmful substances in the food matrix based on metal-organic frameworks. In this paper, we introduced the synthesis and detection application characteristics (absorption, fluorescence, etc.) of metal-organic frameworks. We summarized their applications in the MOFs-based fluorometric detection of harmful substances in food and water over the past few years. The harmful substances mainly include heavy metals, organic pollutants and other small molecules, etc. On this basis, the future development and possible application of the MOFs have prospected in this review paper.