Mitochondria-derived methylmalonic acid aggravates ischemia-reperfusion injury by activating reactive oxygen species-dependent ferroptosis.

Ferroptosis is a regulatory cell death process pivotal in myocardial ischemia-reperfusion (I/R) injury. However, the precise mechanism underlying myocardial ferroptosis remains less known. In this study, we investigated the pathophysiological mechanisms of methylmalonic acid (MMA) associated with ferroptosis activation in cardiomyocytes after I/R. We found an increase level of MMA in patients with acute myocardial injury after reperfusion and AC16 cells under hypoxia/reoxygenation (H/R) condition. MMA treatment was found to be associated with excessive oxidative stress in cardiomyocytes, leading to ferroptosis-related myocardial injury. In mice with I/R injury, MMA treatment aggravated myocardial oxidative stress and ferroptosis, which amplified the myocardial infarct size and cardiac dysfunction. Mechanistically, MMA promoted NOX2/4 expression to increase reactive oxygen species (ROS) production in cardiomyocytes, aggravating myocardial injury. Notably, the increased ROS further activated ferroptosis by inhibiting solute carrier family 7 member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4) expression. In addition, MMA decreased the ectopic nuclear distribution of nuclear factor E2-related factor 2 (NRF2) by increasing the interaction between NRF2 and kelch-like ECH-associated protein 1 (KEAP1). This impeded the activation of GPX4/SLC7A11, downstream of NRF2, activating ferroptosis and aggravating myocardial cell injury. Collectively, our study indicates that MMA activates oxidative stress and ROS generation, which induces ferroptosis to exacerbate cardiomyocyte injury in an I/R model. These findings may provide a new perspective for the clinical treatment of I/R injury and warrant further investigation.

Eosin Y-Based Metal-Organic Framework Synergistic with Cobalt(II) Complex for Hydrogen Evolution through Photoinduced Intermolecular Electron Transfer.

Photocatalytic hydrogen evolution reaction (HER) is a promising approach for producing clean energy and has the potential to play an important role in the transition toward a more sustainable and environmentally friendly energy system. Optimizing the photoinduced electron transfer (PET) process and increasing visible-light utilization play a central role in photocatalysis. Herein, we built a novel Eosin Y-based metal-organic framework (Zn-EYTP) by synergizing a cobalt(II) complex for boosting the H2 evolution efficiency through photoinduced intermolecular electron transfer. Under optimized conditions, the maximum H2 evolution efficiency for Zn-EYTP was determined to be a turnover number (TON) value of 11,100 under green LED irradiation. And the synthesized Zn-EYTP photocatalysts could be easily recycled to restore the initial photocatalytic activity even after 3 cycles. Detailed studies reveal that the significantly enhanced HER activity in Zn-EYTP could be ascribed to the effective separation of photogenerated charges and the synergistic intermolecular interaction between Zn-EYTP and [Co(bpy)3]Cl2. The present work enables a deeper understanding of the importance of the PET process for enhanced HER photocatalytic activities, which will provide a viable strategy for the development of highly efficient photocatalysts.

Post-Synthetic Modification of an Amino-Functionalized Metal-Organic Framework for Highly In Situ Luminescent Detection of Mercury (II).

A sulfur-containing metal-organic framework, donated as UiO-66-NSMe, was prepared by the post-synthetic modification (PSM) of UiO-66-NH2 with 2-(Methylthio)benzaldehyde, and the successful synthesis of PSM was confirmed by X-ray photoelectron spectroscopy (XPS), FT-IR and 1H NMR studies. According to the characteristics of mercury thiophilic, UiO-66-NSMe could be used as a luminescent sensor for Hg2+ detection with a high selectivity and sensitivity (Ksv = 2.5 × 104 M-1; LOD = 20 nM), which could be attributed to the coordination between sulfur sites and Hg2+ based on XPS results. In practical applications, UiO-66-NSMe yielded satisfactory recovery rates (ranging from 96.1% to 99.5%) when it was employed for detecting Hg2+ in spiked environmental samples. Furthermore, UiO-66-NSMe was successfully employed to detect mercury (II) residues with the in situ rapid nondestructive imaging in simulated fresh agricultural products. Thus, this PSM strategy could provide good guidance for environmental protection methodologies in the future.

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.

Zirconium metal-organic cage decorated with squaramides imparts dual activation for chemical fixation of CO2 under mild conditions.

A "two-in-one" dual activation strategy has been developed to give high-density hydrogen-bonding (HB) active units and Lewis acid (LA) active centres by immobilizing squaramides into metal-organic cages (MOCs). The obtained MOC served as an efficient catalyst for the chemical fixation of CO2 under mild conditions up to 99% yields with good recyclability, and the mechanism of high catalytic activity has been further explored.

An Ultrasensitive Picric Acid Sensor Based on a Robust 3D Hydrogen-Bonded Organic Framework.

Hydrogen-bonded organic frameworks (HOFs), as a newly developed porous material, have been widely used in various fields. To date, several organic building units (OBUs) with tri-, tetra-, and hexa-carboxylic acid synthons have been applied to synthesize HOFs. To our knowledge, di-carboxylic acids have rarely been reported for the construction of HOFs, in particular, di-carboxylic acid-based HOFs with fluorescence sensing properties have not been reported. In this study, a rare example of a di-carboxylic acid-based, luminescent three-dimensional hydrogen-bonded organic framework has been successfully constructed and structurally characterized; it has a strong electron-rich property originated from its organic linker 9-phenylcarbazole-3,6-dicarboxylic acid. It represents the first example of HOF-based sensors for the highly selective and sensitive detection of PA (Picric acid) with reusability; the LOD is less than 60 nM. This work thus provides a new avenue for the fabrication of fluorescent HOFs sensing towards explosives.

Selective detection of sulfasalazine antibiotic and its controllable photodegradation into 5-aminosalicylic acid by visible-light-responsive metal-organic framework.

The extensive use of sulfasalazine (SSZ) antibiotics has brought potential threats to aquatic ecosystems and human health. Thus, necessary measures for the removal of SSZ must be taken to prevent arbitrary antibiotic exposure to the aquatic environment. However, not all the recent photocatalysts that have been used for the degradation of SSZ could not achieve the controlled release of SSZ and hence are losing their medicinal values. Herein, by utilizing an Eosin Y moiety as an efficient light-harvesting and emission site, an Eosin Y-based visible-light-responsive metal-organic framework has been synthesized and characterized, which exhibits high selectivity for detecting the antibiotic SSZ in water and simulated physiological conditions, with a detection limit of below 1 µM (0.4 µg mL-1). It also represents the first example of a MOF-based photocatalyst for the controllable degradation of SSZ into 5-aminosalicylic acid with excellent catalytic activity and recyclability.

Triphenylamine-containing imine-linked porous organic network for luminescent detection and adsorption of Cr(VI) in water.

In this study, an imine-linked luminescent porous organic network (PON) has been successfully synthesized by the Schiff-base condensation reaction between 1,2-diphenylethylenediamine and tris(4-formylphenyl)amine. It exhibits strong fluorescence in an aqueous dispersion and can be applied as a luminescent probe for Cr(VI) (CrO42- and Cr2O72-) with high selectivity and sensitivity (LOD for Cr2O72- and CrO42- were below 0.35 µM and 0.4 µM, respectively) in a turn-off manner. The possible luminescence sensing mechanism and the adsorption capacity of Cr(VI) are also discussed in detail.

A Two-Fold Interpenetrated Dual-Emitting Luminescent Metal-Organic Framework as a Ratiometric Sensor for Chromium(III).

A novel two-fold interpenetrated metal-organic framework, namely Co-EDDA, was synthesized by hydrothermal reaction of 5,5'-[ethane-1,2-diylbis(oxy)]diisophthalic acid (H4EDDA), Co(NO3)2·6H2O, and 1,4-di(1H-imidazol-1-yl)benzene in water in an alkaline environment and structurally characterized. Co-EDDA could display clear dual-emission signals at 350 and 430 nm, representing the charge transfer emission between metal ions and the ligand and the ligand-based emission, respectively, which represents the ratiometric luminescence response to chromium(III) with high selectivity and sensitivity (limit of detection of 0.54 µM). Comprehensive studies indicate that the detection can be attributed to the interaction between the Cr3+ ions and the O atoms on the ether bond in Co-EDDA.

Amino and triazole-containing metal-organic frameworks for highly efficient CO2 fixation.

In this study, a novel porous metal-organic framework (MOF) functionalized with amino and triazole moieties has been synthesized. Attributed to the high affinity to CO2 and unsaturated zinc centers, the MOF exhibits high catalytic activity for the CO2 to epoxide cycloaddition reaction, with a turnover number value of up to 10 000 per cycle, and can be reused at least for 20 cycles.

Luminescent metal-organic frameworks as chemical sensors based on "mechanism-response": a review.

Metal-organic frameworks (MOFs), composed of metal ions/clusters and organic ligands and possessing inherent crystallinity, a definite structure, a tunable pore, and multiple functionalizations, have shown potential for numerous applications. Recently, luminescent MOFs (LMOFs) have attracted much attention as sensing materials because their structural and chemical tunability can afford good selectivity through pore-sieving functions with different pore sizes or host framework-guest interactions. Meanwhile, MOFs with high internal surface areas can concentrate analytes to a high density, thereby decreasing detection limits and exhibiting high sensitivity. Numerous LMOFs have been synthesized and employed for sensing applications. Here, the recent advances of LMOFs as chemical sensors based on "mechanism-response" were summarized, including collapse of frameworks, overlap, cation exchange, ligand exchange, reaction- and redox-based mechanisms, electron transfer, energy transfer, hydrogen bonding, linker-analyte interaction, synergistic effects, and multiple interactions. Moreover, in this review, present challenges and future opportunities in this field are discussed. This review could be a valuable reference for the rational construction and sensing applications of LMOFs.

Metal-organic frameworks containing xanthene dyes for photocatalytic applications.

Metal-organic frameworks (MOFs) have recently emerged as a new type of prospective photocatalytic material due to their characteristics such as tunable structures, pore modification, crystalline nature with eliminated structural defects, unique semiconductor properties, etc. However, most of these systems also suffer from low activity, high cost, and low visible light utilization. Xanthene dyes are eco-friendly organic dyes used in photocatalysis. They possess the advantages of low cost, low toxicity, and high visible light response; so, they can be directly used as building blocks to fabricate MOF materials or as proper cocatalysts to increase the absorbance of irradiation leading to the construction of a reasonable photocatalytic system. Herein, we have summarized the recent developments in the study of MOFs containing xanthene dyes for photocatalytic applications. The paper can be divided into two sections depending on whether the xanthene dyes are coordinated in the MOF structure: (i) MOFs synergized with xanthene dyes for photocatalytic applications and (ii) MOFs with xanthene dyes incorporated within ligand backbones for photocatalytic applications. Moreover, in this paper, the present challenges and future opportunities in this field are also discussed.

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 0.21 µM, and it possesses a fast response of 30 s. The sensing mechanism is also discussed.

Lanthanide-Based Metal-Organic Frameworks Containing "V-Shaped" Tetracarboxylate Ligands: Synthesis, Crystal Structures, "Naked-Eye" Luminescent Detection, and Catalytic Properties.

Three lanthanide-based metal-organic frameworks, [Tb(HMDIA)(H2O)3]·H2O (Tb-MDIA), [Ho(HMDIA)(H2O)3]·(H2O)2 (Ho-MDIA), and [Nd(HMDIA)(H2O)3]·(H2O)2 (Nd-MDIA) from the same V-shaped ligand 5,5'-methylenediisophthalic acid (H4MDIA), were prepared by mixing Ln3+ and H4MDIA under solvothermal conditions. The crystal structures of the three complexes were determined by single-crystal X-ray diffraction. The different coordination modes of the organic ligands resulted in different framework structures among the three complexes. The luminescent properties of Ln-MDIA in the ultraviolet-visible region were also studied. Interestingly, the bright-green emitter Tb-MDIA showed high selectivity and sensitivity to allow the naked-eye visualization of Fe3+ ions and picric acid (PA) explosive, and both sensing mechanisms were revealed. Finally, Ho-MDIA and Nd-MDIA were shown to work as heterogeneous catalysts for the cyanosilylation reaction of aromatic aldehydes, and the catalysts could be recycled at least three times without any decrease in activity.

Post-imparting Brønsted acidity into an amino-functionalized MOF as a bifunctional luminescent turn-ON sensor for the detection of aluminum ions and lysine.

A novel aldehyde- and amino-functionalized luminescent metal-organic framework, Cd-TCHO, was constructed through the solvothermal reaction of 4,4',4''-tricarboxytriphenylamine, 2-amino-3-pyridinecarboxaldehyde and cadmium nitrate and was characterized. Post-synthetically oxidizing the aldehyde groups into carboxylate groups afforded a new complex, Cd-TCOOH, and this successful conversion process was confirmed by FT-IR and 1H NMR studies. With the Brønsted acidic sites inside the cavities of Cd-TCOOH, it could be used as a luminescent sensor for Al3+ detection with a high selectivity and sensitivity (LOD = 0.54 ppb), which could be attributed to the coordination between free Brønsted acidic sites and Al3+. Importantly, it could also detect Lys among 20 kinds of natural amino acids; the selectivity, sensitivity and the sensing mechanism are discussed in detail. Also, both of the sensing processes were carried out in the HEPES buffer.

Carbon dioxide capture and efficient fixation in a dynamic porous coordination polymer.

Direct structural information of confined CO2 in a micropore is important for elucidating its specific binding or activation mechanism. However, weak gas-binding ability and/or poor sample crystallinity after guest exchange hindered the development of efficient materials for CO2 incorporation, activation and conversion. Here, we present a dynamic porous coordination polymer (PCP) material with local flexibility, in which the propeller-like ligands rotate to permit CO2 trapping. This process can be characterized by X-ray structural analysis. Owing to its high affinity towards CO2 and the confinement effect, the PCP exhibits high catalytic activity, rapid transformation dynamics, even high size selectivity to different substrates. Together with an excellent stability with turnover numbers (TON) of up to 39,000 per Zn1.5 cluster of catalyst after 10 cycles for CO2 cycloaddition to form value-added cyclic carbonates, these results demonstrate that such distinctive structure is responsible for visual CO2 capture and size-selective conversion.

A nanoporous metal-organic framework as a renewable size-selective hydrogen-bonding catalyst in water.

A novel squaramide-containing metal-organic framework (MOF) material has been designed and synthesized. A detailed X-ray crystal structure analysis showed that four squaramides of this MOF adopted two orientations in each dependent nanopore, confirming that two carbonyl and two N-H groups pointed simultaneously to the inside of the one-dimensional nanometer channel. The MOF was applied as an efficient bifunctional hydrogen-bonding catalyst for Michael additions of 1,3-dicarbonyl compounds to nitroalkenes in pure water, boosting the catalytic efficiency by up to approximately five times the value afforded by the homogeneous control and exhibiting a highly size-selective catalytic performance and good renewability. The catalytic mechanism was also discussed in detail. The present study provides a highly promising approach to achieving dual-activation catalytic centers in a single system, which function as microscopic chemical reactors that allow the interaction and fast transport of substrate molecules in their cavities.

Cobalt(II)-Based Metal-Organic Framework as Bifunctional Materials for Ag(I) Detection and Proton Reduction Catalysis for Hydrogen Production.

A novel cobalt(II)-based metal-organic framework, Co-MB, was prepared by hydrothermal reaction of Co(NO3)2·6H2O, 3,3'-methylenediphthalic acid (H4mda), and 1,4-bis(imidazol-1-ylmethyl)-benzene in sodium hydroxide aqueous solution and structurally characterized. It shows a high stability in water within the pH range from 2.2 to 11.6, which could be used as a highly selective and sensitive luminescent sensor for Ag(I) detection in a luminescent enhancement manner, with LOD about 23 nM. Importantly, such stable Co-MB could also work as proton reduction catalyst for photodriven hydrogen production coupled with visible-light organic dyes as photosensitizer. The influence factors of hydrogen production including pH, TEA (triethylamine) contents, and kinds of organic dyes are studied in detail. Under optimal condition, the TON value was up to 5133 per cycle, and this Co-MB could also be reused at least 3 times.

Photoactive metal-organic framework as a bifunctional material for 4-hydroxy-4'-nitrobiphenyl detection and photodegradation of methylene blue.

Environmental pollution resulting from organic pollutants is becoming an overwhelming problem throughout the world, and how to efficiently detect or eliminate these organic pollutants remains an important issue for environmental protection. Herein, a cadmium(ii)-based MOF, Cd-TCAA, was successfully prepared by the hydrothermal reaction of 4,4',4''-tricarboxyltriphenylamine (H3tca), (E)-1,2-di(pyridin-4-yl)diazene (abp) and cadmium nitrate. Because the H3tca moiety is a typically versatile functional material that exhibits good hole-transporting capabilities, efficient light harvesting, and excellent electron-donating properties, this novel photoactive metal-organic framework operates as a bifunctional material for the detection and degradation of organic pollutants. It exhibits excellent selectivity and sensitivity towards 4-hydroxy-4'-nitrobiphenyl (HNBP) with a detection limit of 50 nM in solution, and represents the first example of a MOF-based sensor for the detection of HNBP. The photocatalytic activity of Cd-TCAA was also determined by investigating the photo-induced degradation of methylene blue (MB). Cd-TCAA has the advantages of excellent catalytic activity, stability, and recyclability.

A squaramide-based metal-organic framework as a luminescent sensor for the detection of lactose in aqueous solution and in milk.

A novel squaramide-containing metal-organic framework (MOF) has been designed and synthesized, which represents the first example of the luminescence selective detection of lactose over other monosaccharides and disaccharides. It was also used for the quantitative determination of lactose in milk.