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.

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.

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.

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.

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.

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.

Highly Efficient Visible-Light-Driven H2 Production via an Eosin Y-Based Metal-Organic Framework.

A simple and effective strategy was developed to immobilize ecofriendly dye inside a porous metal-organic framework (MOF) built from Eosin Y with [Cd2(COO)2(µ2-H2O)] secondary building units for the first time. The MOF exhibited efficient photocatalytic activity for H2 evolution under visible-light irradiation with a turnover number of 13920 and an initial turnover frequency of 7433 h-1, which was approximately 31 times the photocatalytic efficiency of Eosin Y.

A Highly Chemically Stable Metal-Organic Framework as a Luminescent Probe for the Regenerable Ratiometric Sensing of†pH.

A heteroatom-rich 3D noninterpenetrating metal-organic framework (MOF) Cd-EDDA constructed from an ethylene glycol ether bridging tetracarboxylate ligand H4 EDDA (5,5'-(ethane-1,2-diylbis(oxy))diisophthalic acid) shows good chemical resistance to both acidic and alkaline solutions with a pH ranging from 2.0 to 12.2. There is a corresponding ratiometric luminescence response to pH from 2.0 to 11.5, and the sensing mechanism is also discussed through ion chromatography and molecular force field-based calculations. Importantly, the probe can easily be regenerated simply by modulating the pH of the solution, thus being the first example of a regenerable MOF-based ratiometric luminescent probe for pH.

Photoactive Metal-Organic Framework and Its Film for Light-Driven Hydrogen Production and Carbon Dioxide Reduction.

The design of a new photocatalytic system and integrating the essential components in a structurally controlled manner to create artificially photosynthetic systems is high desirable. By incorporating a photoactive triphenylamine moiety to assemble a Gd-based metal-organic framework as a heterogeneous photosensitizer, new artificial systems were constructed for the proton and carbon dioxide reduction under irradiation. The assembled MOFs exhibited a one-dimensional metal-oxygen pillar that was connected together by the depronated TCA(3-) ligands to form a three-dimensional noninterpenetrating porous framework. The combining of proton reduction and/or the carbon dioxide reduction catalysts, i.e., the Fe-Fe hydrogenase active site models and the Ni(Cyclam) complexes, initiated a photoinduced single electron transfer from its excited state to the substrate. The system exhibited an initial TOF of 320 h(-1) of hydrogen per catalyst and an overall quantum yield of about 0.21% and is able to reduce carbon dioxide under irradiation. The deposit of the photoactive Gd-TCA into the film of an α-Al2O3 plate provided a platform for the practical applications through prolonging the lifetime of the artifical system and allowed the easily operated devices being recyclable as a promising photocatalytic system.

Multifunctional Luminescent Eu(III)-Based Metal-Organic Framework for Sensing Methanol and Detection and Adsorption of Fe(III) Ions in Aqueous Solution.

A novel lanthanide-organic framework (Eu-HODA), consisting of 2,2',3,3'-oxidiphthalic acids as efficient sensitizing units, is assembled and characterized. Eu-HODA features rare chiral helical channels despite the achiral nature of H4ODA. It is found that this MOF shows a unique luminescent response to methanol, in contrast to n-propanol and ethanol. Eu-HODA reveals a turn-off luminescence switching initiated by acetone molecules with an EC50 of 0.03 vol %, which is below the occupational exposure limit of acetone stipulated by the American Conference of Governmental Industrial Hygienists. Furthermore, it also exhibits high sensitivity (Stern-Volmer constant KSV = 2.09 × 104 L/mol) and low detection limit (6.4 ppb) for Fe3+ ions in pure water because of the existence of uncoordinated carboxyl groups within open frameworks. Eu-HODA-based test paper provides a simple and reliable detection method for Fe3+ in practical applications.

Cadmium-Based Metal-Organic Framework as a Highly Selective and Sensitive Ratiometric Luminescent Sensor for Mercury(II).

A novel cadmium-based metal-organic framework (MOF) material with dual-emission signals has been constructed that can act as the first example of MOF-implicated ratiometric sensor for mercury(II) in pure water with a fast response, high selectivity, and sensitivity. The sensing mechanism is also discussed.

Cerium-based M4L4 tetrahedra as molecular flasks for selective reaction prompting and luminescent reaction tracing.

The application of metal-organic polyhedra as "molecular flasks" has precipitated a surge of interest in the reactivity and property of molecules within well-defined spaces. Inspired by the structures of the natural enzymatic pockets, three metal-organic neutral molecular tetrahedral, Ce-TTS, Ce-TNS and Ce-TBS (H6TTS: N',N'',N'''-nitrilotris-4,4',4''-(2-hydroxybenzylidene)-benzohydrazide; H6TNS: N',N'',N'''-nitrilotris-6,6',6''-(2-hydroxybenzylidene)-2-naphthohydrazide; H6TBS: 1,3,5-phenyltris-4,4',4''-(2-hydroxybenzylidene)benzohydrazide), which exhibit different size of the edges and cavities, were achieved through self-assembly by incorporating robust amide-containing tridentate chelating sites into the fragments of the ligands. They acted as molecular flasks to prompt the cyanosilylation of aldehydes with excellent selectivity towards the substrates size. The amide groups worked as trigger sites and catalytic driven forces to achieve efficient guest interactions, enforcing the substrates proximity within the cavity. Experiments on catalysts with the different cavity radii and substrates with the different molecular size demonstrated that the catalytic performance exhibited enzymatical catalytic mechanism and occurred in the molecular flask. These amides were also able to amplify guest-bonding events into the measurable outputs for the detection of concentration variations of the substrates, providing the possibility for metal-organic hosts to work as smart molecular flasks for the luminescent tracing of catalytic reactions.

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.

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.

Photoactive chiral metal-organic frameworks for light-driven asymmetric α-alkylation of aldehydes.

Chiral metal-organic frameworks (MOFs) with porous and tunable nature show promise as heterogeneous asymmetric catalysts. Through incorporating the stereoselective organocatalyst L- or D-pyrrolidin-2-ylimidazole (PYI) and a triphenylamine photoredox group into a single framework, we have developed two enantiomeric MOFs, Zn-PYI1 and Zn-PYI2, to prompt the asymmetric α-alkylation of aliphatic aldehydes in a heterogeneous manner. The strong reductive excited state of the triphenylamaine moiety within these MOFs initiated a photoinduced electron transfer, rendering an active intermediate for the α-alkylation. The chiral PYI moieties acted as cooperative organocatalytic active sites to drive the asymmetric catalysis with significant stereoselectivity. Control experiments using the lanthanide-based metal-organic frameworks Ho-TCA and MOF-150, assembled from 4,4',4"-nitrilotribenzoic acid, as catalysts suggested that both the photosensitizer triphenylamine moiety and the chiral organocatalyst D-/L-PYI moiety were necessary for the light-driven α-alkylation reactions. Further investigations demonstrated that the integration of both photocatalyst and asymmetric organocatalyst into a single MOF makes the enantioselection superior to that of simply mixing the corresponding MOFs with the chiral adduct. The easy availability, excellent stereoselectivity, great separability, and individual components fixed with their well-defined porous and repeating structures make the MOF a versatile platform for a new type of tandem catalyst and cooperative catalyst.

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.

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.

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.

An amide-containing metal-organic tetrahedron responding to a spin-trapping reaction in a fluorescent enhancement manner for biological imaging of NO in living cells.

Metal-organic polyhedra represent a unique class of functional molecular containers that display interesting molecular recognition properties and fascinating reactivity reminiscent of the natural enzymes. By incorporating a triphenylamine moiety as a bright blue emitter, a robust cerium-based tetrahedron was developed as a luminescent detector of nitronyl nitroxide (PTIO), a specific spin-labeling nitric oxide (NO) trapper. The tetrahedron encapsulates molecules of NO and PTIO within the cavity to prompt the spin-trapping reaction and transforms the normal EPR responses into a more sensitively luminescent signaling system with the limit of detection improved to 5 nM. Twelve-fold amide groups are also functionalized within the tetrahedron to modify the hydrophilic/lipophilic environment, ensuring the successful application of biological imaging in living cells.

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.