Multimetal-Based Metal-Organic Framework System for the Sensitive Detection of Heart-Type Fatty Acid Binding Protein in Electrochemiluminescence Immunoassay.

In this work, an electrochemiluminescence (ECL) quenching system using multimetal-organic frameworks (MMOFs) was proposed for the sensitive and specific detection of heart-type fatty acid-binding protein (H-FABP), a marker of acute myocardial infarction (AMI). Bimetallic MOFs containing Ru and Mn as metal centers were synthesized via a one-step hydrothermal method, yielding RuMn MOFs as the ECL emitter. The RuMn MOFs not only possessed the strong ECL performance of Ru(bpy)32+ but also maintained high porosity and original metal active sites characteristic of MOFs. Moreover, under the synergistic effect of MOFs and Ru(bpy)32+, RuMn MOFs have more efficient and stable ECL emission. The trimetal-based MOF (FePtRh MOF) was used as the ECL quencher because of the electron transfer between FePtRh MOFs and RuMn MOFs. In addition, active intramolecular electron transfer from Pt to Fe or Rh atoms also occurred in FePtRh MOFs, which could promote intermolecular electron transfer and improve electron transfer efficiency to enhance the quenching efficiency. The proposed ECL immunosensor demonstrated a wide dynamic range and a low detection limit of 0.01-100 ng mL-1 and 6.8 pg mL-1, respectively, under optimal conditions. The ECL quenching system also presented good specificity, stability, and reproducibility. Therefore, an alternative method for H-FABP detection in clinical diagnosis was provided by this study, highlighting the potential of MMOFs in advancing ECL technology.

Direct Synthesis of N-formamides by Integrating Reductive Amination of Ketones and Aldehydes with CO2 Fixation in a Metal-Organic Framework.

Formamides are important feedstocks for the manufacture of many fine chemicals. State-of-the-art synthesis of formamides relies on the use of an excess amount of reagents, giving copious waste and thus poor atom-economy. Here, we report the first example of direct synthesis of N-formamides by coupling two challenging reactions, namely reductive amination of carbonyl compounds, particularly biomass-derived aldehydes and ketones, and fixation of CO2 in the presence of H2 over a metal-organic framework supported ruthenium catalyst, Ru/MFM-300(Cr). Highly selective production of N-formamides has been observed for a wide range of carbonyl compounds. Synchrotron X-ray powder diffraction reveals the presence of strong host-guest binding interactions via hydrogen bonding and parallel-displaced π⋅⋅⋅π interactions between the catalyst and adsorbed substrates facilitating the activation of substrates and promoting selectivity to formamides. The use of multifunctional porous catalysts to integrate CO2 utilisation in the synthesis of formamide products will have a significant impact in the sustainable synthesis of feedstock chemicals.

Ultra-fast Proton Conduction and Photocatalytic Water Splitting in a Pillared Metal-Organic Framework.

Proton-exchange membrane fuel cells enable the portable utilization of hydrogen (H2) as an energy resource. Current electrolytic materials have limitation, and there is an urgent need to develop new materials showing especially high proton conductivity. Here, we report the ultra-fast proton conduction in a novel metal-organic framework, MFM-808, which adopts an unprecedented topology and a unique structure consisting of two-dimensional layers of {Zr6}-clusters. By replacing the bridging formate with sulfate ligands within {Zr6}-layers, the modified MFM-808-SO4 exhibits an exceptional proton conductivity of 0.21 S·cm-1 at 85 °C and 99% relative humidity. Modeling by molecular dynamics confirms that proton transfer is promoted by an efficient two-dimensional conducting network assembled by sulfate-{Zr6}-layers. MFM-808-SO4 also possesses excellent photocatalytic activity for water splitting to produce H2, paving a new pathway to achieve a renewable hydrogen-energy cycle.

Direct Conversion of Methane to Ethylene and Acetylene over an Iron-Based Metal-Organic Framework.

Conversion of methane (CH4) to ethylene (C2H4) and/or acetylene (C2H2) enables routes to a wide range of products directly from natural gas. However, high reaction temperatures and pressures are often required to activate and convert CH4 controllably, and separating C2+ products from unreacted CH4 can be challenging. Here, we report the direct conversion of CH4 to C2H4 and C2H2 driven by non-thermal plasma under ambient (25 °C and 1 atm) and flow conditions over a metal-organic framework material, MFM-300(Fe). The selectivity for the formation of C2H4 and C2H2 reaches 96% with a high time yield of 334 µmol gcat-1 h-1. At a conversion of 10%, the selectivity to C2+ hydrocarbons and time yield exceed 98% and 2056 µmol gcat-1 h-1, respectively, representing a new benchmark for conversion of CH4. In situ neutron powder diffraction, inelastic neutron scattering and solid-state nuclear magnetic resonance, electron paramagnetic resonance (EPR), and diffuse reflectance infrared Fourier transform spectroscopies, coupled with modeling studies, reveal the crucial role of Fe-O(H)-Fe sites in activating CH4 and stabilizing reaction intermediates via the formation of an Fe-O(CH3)-Fe adduct. In addition, a cascade fixed-bed system has been developed to achieve online separation of C2H4 and C2H2 from unreacted CH4 for direct use. Integrating the processes of CH4 activation, conversion, and product separation within one system opens a new avenue for natural gas utility, bridging the gap between fundamental studies and practical applications in this area.

Direct photo-oxidation of methane to methanol over a mono-iron hydroxyl site.

Natural gas, consisting mainly of methane (CH4), has a relatively low energy density at ambient conditions (~36 kJ l-1). Partial oxidation of CH4 to methanol (CH3OH) lifts the energy density to ~17 MJ l-1 and drives the production of numerous chemicals. In nature, this is achieved by methane monooxygenase with di-iron sites, which is extremely challenging to mimic in artificial systems due to the high dissociation energy of the C-H bond in CH4 (439 kJ mol-1) and facile over-oxidation of CH3OH to CO and CO2. Here we report the direct photo-oxidation of CH4 over mono-iron hydroxyl sites immobilized within a metal-organic framework, PMOF-RuFe(OH). Under ambient and flow conditions in the presence of H2O and O2, CH4 is converted to CH3OH with 100% selectivity and a time yield of 8.81 ± 0.34 mmol gcat-1 h-1 (versus 5.05 mmol gcat-1 h-1 for methane monooxygenase). By using operando spectroscopic and modelling techniques, we find that confined mono-iron hydroxyl sites bind CH4 by forming an [Fe-OH···CH4] intermediate, thus lowering the barrier for C-H bond activation. The confinement of mono-iron hydroxyl sites in a porous matrix demonstrates a strategy for C-H bond activation in CH4 to drive the direct photosynthesis of CH3OH.

Highly Efficient Proton Conduction in the Metal-Organic Framework Material MFM-300(Cr)·SO4(H3O)2.

The development of materials showing rapid proton conduction with a low activation energy and stable performance over a wide temperature range is an important and challenging line of research. Here, we report confinement of sulfuric acid within porous MFM-300(Cr) to give MFM-300(Cr)·SO4(H3O)2, which exhibits a record-low activation energy of 0.04 eV, resulting in stable proton conductivity between 25 and 80 °C of >10-2 S cm-1. In situ synchrotron X-ray powder diffraction (SXPD), neutron powder diffraction (NPD), quasielastic neutron scattering (QENS), and molecular dynamics (MD) simulation reveal the pathways of proton transport and the molecular mechanism of proton diffusion within the pores. Confined sulfuric acid species together with adsorbed water molecules play a critical role in promoting the proton transfer through this robust network to afford a material in which proton conductivity is almost temperature-independent.

Bimetallic Aluminum- and Niobium-Doped MCM-41 for Efficient Conversion of Biomass-Derived 2-Methyltetrahydrofuran to Pentadienes.

The production of conjugated C4-C5 dienes from biomass can enable the sustainable synthesis of many important polymers and liquid fuels. Here, we report the first example of bimetallic (Nb, Al)-atomically doped mesoporous silica, denoted as AlNb-MCM-41, which affords quantitative conversion of 2-methyltetrahydrofuran (2-MTHF) to pentadienes with a high selectivity of 91 %. The incorporation of AlIII and NbV sites into the framework of AlNb-MCM-41 has effectively tuned the nature and distribution of Lewis and Brønsted acid sites within the structure. Operando X-ray absorption, diffuse reflectance infrared and solid-state NMR spectroscopy collectively reveal the molecular mechanism of the conversion of adsorbed 2-MTHF over AlNb-MCM-41. Specifically, the atomically-dispersed NbV sites play an important role in binding 2-MTHF to drive the conversion. Overall, this study highlights the potential of hetero-atomic mesoporous solids for the manufacture of renewable materials.

Neighboring Zn-Zr Sites in a Metal-Organic Framework for CO2 Hydrogenation.

ZrZnOx is active in catalyzing carbon dioxide (CO2) hydrogenation to methanol (MeOH) via a synergy between ZnOx and ZrOx. Here we report the construction of Zn2+-O-Zr4+ sites in a metal-organic framework (MOF) to reveal insights into the structural requirement for MeOH production. The Zn2+-O-Zr4+ sites are obtained by postsynthetic treatment of Zr6(µ3-O)4(µ3-OH)4 nodes of MOF-808 by ZnEt2 and a mild thermal treatment to remove capping ligands and afford exposed metal sites for catalysis. The resultant MOF-808-Zn catalyst exhibits >99% MeOH selectivity in CO2 hydrogenation at 250 °C and a high space-time yield of up to 190.7 mgMeOH gZn-1 h-1. The catalytic activity is stable for at least 100 h. X-ray absorption spectroscopy (XAS) analyses indicate the presence of Zn2+-O-Zr4+ centers instead of ZnmOn clusters. Temperature-programmed desorption (TPD) of hydrogen and H/D exchange tests show the activation of H2 by Zn2+ centers. Open Zr4+ sites are also critical, as Zn2+ centers supported on Zr-based nodes of other MOFs without open Zr4+ sites fail to produce MeOH. TPD of CO2 reveals the importance of bicarbonate decomposition under reaction conditions in generating open Zr4+ sites for CO2 activation. The well-defined local structures of metal-oxo nodes in MOFs provide a unique opportunity to elucidate structural details of bifunctional catalytic centers.

[Endocytic recycling pathways and the regulatory mechanisms].

Endocytic transport is imperative for the exchange of information between cells and the external environment. Specifically, the process of endocytic transport comprises precise regulation of uptake and sorting of extracellular macromolecules, phospholipids, and membrane proteins. In the endocytic transport system, the recycling pathways are responsible for delivering membrane proteins and phospholipids back to the plasma membrane. Thus, endocytic recycling plays critical roles in various biological processes, including nutrient absorption, cell polarity establishment, cell migration, cell division, synaptic plasticity, immune response, and growth factor receptor regulation. There are two essential types of recycling pathways in eukaryotic cells, recycling of clathrin-dependent endocytic cargos (CDE recycling) and recycling of clathrin-independent endocytic cargos (CIE recycling). The transferrin receptor TfR and the low-density lipoprotein receptor LDLR, which have essential physiological roles in vivo, are representative membrane proteins of the CDE recycling transport. In recent years, various membrane proteins governed by CIE recycling transport have been identified, including IL2 receptor α-subunit, major histocompatibility complex MHC Class I, and glucose transporter GLUT4. Therefore, the investigation of the regulatory mechanisms of CIE recycling has drawn notable attention in the field. Moreover, CIE recycling research presents fundamental significance in cell biology, which also provides scientific evidence and potential therapeutic clues for the diagnosis and treatment strategies of diseases such as type 2 diabetes and cancer. Compared with the CDE recycling, the study on CIE recycling started later, and there is much to be learned of its regulatory mechanisms. To this end, this review summarizes the features of endocytic recycling pathways, focuses on the molecular basis of CIE recycling regulation and elaborates on the latest progress and newly developed research model systems in the field of CIE recycling.

A Dynamically Stabilized Single-Nickel Electrocatalyst for Selective Reduction of Oxygen to Hydrogen Peroxide.

On-location electrochemical generation of H2 O2 is of great current interest. Herein, selective two-electron reduction of O2 to H2 O2 by a single [NiII (H2 O)6 ]2+ cation that is dynamically associated with a negatively charged metal-organic layer (MOL) by hydrogen bonding and coulombic interactions is reported. In contrast, NiII centers covalently immobilized on the MOL reduce O2 to H2 O in a four- electron process. Oxygen adsorption by [NiII (H2 O)6 ]2+ followed by two-electron reduction generates neutral [NiII (H2 O)4 (OH)(OOH)]0 , which momentarily disconnects from the negatively charged MOL to avoid the injection of additional electrons. Release of H2 O2 from [NiII (H2 O)4 (OH)(OOH)]0 regenerates [NiII (H2 O)6 ]2+ , which regains affinity to the MOL. Such dynamically associated NiII single-metal electrocatalysts ensure high selectivity and represent a new strategy for generating selective catalysts for electrochemical production of important chemicals.

Confinement of Ultrasmall Cu/ZnOx Nanoparticles in Metal-Organic Frameworks for Selective Methanol Synthesis from Catalytic Hydrogenation of CO2.

The interfaces of Cu/ZnO and Cu/ZrO2 play vital roles in the hydrogenation of CO2 to methanol by these composite catalysts. Surface structural reorganization and particle growth during catalysis deleteriously reduce these active interfaces, diminishing both catalytic activities and MeOH selectivities. Here we report the use of preassembled bpy and Zr6(µ3-O)4(µ3-OH)4 sites in UiO-bpy metal-organic frameworks (MOFs) to anchor ultrasmall Cu/ZnOx nanoparticles, thus preventing the agglomeration of Cu NPs and phase separation between Cu and ZnOx in MOF-cavity-confined Cu/ZnOx nanoparticles. The resultant Cu/ZnOx@MOF catalysts show very high activity with a space-time yield of up to 2.59 gMeOH kgCu-1 h-1, 100% selectivity for CO2 hydrogenation to methanol, and high stability over 100 h. These new types of strong metal-support interactions between metallic nanoparticles and organic chelates/metal-oxo clusters offer new opportunities in fine-tuning catalytic activities and selectivities of metal nanoparticles@MOFs.

Molecular Iridium Complexes in Metal-Organic Frameworks Catalyze CO2 Hydrogenation via Concerted Proton and Hydride Transfer.

Molecular iridium catalysts immobilized in metal-organic frameworks (MOFs) were positioned in the condensing chamber of a Soxhlet extractor for efficient CO2 hydrogenation. Droplets of hot water seeped through the MOF catalyst to create dynamic gas/liquid interfaces which maximize the contact of CO2, H2, H2O, and the catalyst to achieve a high turnover frequency of 410 h-1 under atmospheric pressure and at 85 °C. H/D kinetic isotope effect measurements and density functional theory calculations revealed concerted proton-hydride transfer in the rate-determining step of CO2 hydrogenation, which was difficult to unravel in homogeneous reactions due to base-catalyzed H/D exchange.

Surface Modification of Two-Dimensional Metal-Organic Layers Creates Biomimetic Catalytic Microenvironments for Selective Oxidation.

Microenvironments in enzymes play crucial roles in controlling the activities and selectivities of reaction centers. Herein we report the tuning of the catalytic microenvironments of metal-organic layers (MOLs), a two-dimensional version of metal-organic frameworks (MOFs) with thickness down to a monolayer, to control product selectivities. By modifying the secondary building units (SBUs) of MOLs with monocarboxylic acids, such as gluconic acid, we changed the hydrophobicity/hydrophilicity around the active sites and fine-tuned the selectivity in photocatalytic oxidation of tetrahydrofuran (THF) to exclusively afford butyrolactone (BTL), likely a result of prolonging the residence time of reaction intermediates in the hydrophilic microenvironment of catalytic centers. Our work highlights new opportunities in using functional MOLs as highly tunable and selective two-dimensional catalytic materials.

Metal-Organic Frameworks Stabilize Mono(phosphine)-Metal Complexes for Broad-Scope Catalytic Reactions.

Mono(phosphine)-M (M-PR3; M = Rh and Ir) complexes selectively prepared by postsynthetic metalation of a porous triarylphosphine-based metal-organic framework (MOF) exhibited excellent activity in the hydrosilylation of ketones and alkenes, the hydrogenation of alkenes, and the C-H borylation of arenes. The recyclable and reusable MOF catalysts significantly outperformed their homogeneous counterparts, presumably via stabilizing M-PR3 intermediates by preventing deleterious disproportionation reactions/ligand exchanges in the catalytic cycles.

Förster Energy Transport in Metal-Organic Frameworks Is Beyond Step-by-Step Hopping.

Metal-organic frameworks (MOFs) with light-harvesting building blocks designed to mimic photosynthetic chromophore arrays in green plants provide an excellent platform to study exciton transport in networks with well-defined structures. A step-by-step exciton random hopping model made of the elementary steps of energy transfer between only the nearest neighbors is usually used to describe the transport dynamics. Although such a nearest neighbor approximation is valid in describing the energy transfer of triplet states via the Dexter mechanism, we found it inadequate in evaluating singlet exciton migration that occurs through the Förster mechanism, which involves one-step jumping over longer distance. We measured migration rates of singlet excitons on two MOFs constructed from truxene-derived ligands and zinc nodes, by monitoring energy transfer from the MOF skeleton to a coumarin probe in the MOF cavity. The diffusivities of the excitons on the frameworks were determined to be 1.8 × 10(-2) cm(2)/s and 2.3 × 10(-2) cm(2)/s, corresponding to migration distances of 43 and 48 nm within their lifetimes, respectively. "Through space" energy-jumping beyond nearest neighbor accounts for up to 67% of the energy transfer rates. This finding presents a new perspective in the design and understanding of highly efficient energy transport networks for singlet excited states.

Highly sensitive photoelectrochemical biosensing detection of early cardiac injury enabled by novel self-assembled Bi2O3/MgIn2S4 photoelectrode coupled with ZnSnO3 quencher.

The development of photoelectrochemical (PEC) biosensors plays a critical role in enabling timely intervention and personalized treatment for cardiac injury. Herein, a novel approach is presented for the fabrication of highly sensitive PEC biosensor employing Bi2O3/MgIn2S4 heterojunction for the ultrasensitive detection of heart fatty acid binding protein (H-FABP). The Bi2O3/MgIn2S4 heterojunction, synthesized through in-situ growth of MgIn2S4 on Bi2O3 nanoplates, offers superior attributes including a larger specific surface area and more homogeneous distribution, leading to enhanced sensing sensitivity. The well-matched valence and conduction bands of Bi2O3 and MgIn2S4 effectively suppress the recombination of photogenerated carriers and facilitate electron transfer, resulting in a significantly improved photocurrent signal response. And the presence of the secondary antibody marker (ZnSnO3) introduces steric hindrance that hinders electron transfer between ascorbic acid and the photoelectrode, leading to a reduction in photocurrent signal. Additionally, the competition between the ZnSnO3 marker and the Bi2O3/MgIn2S4 heterojunction material for the excitation light source further diminishes the photocurrent signal response. After rigorous repeatability and selectivity tests, the PEC biosensor exhibited excellent performance, and the linear detection range of the biosensor was determined to be 0.05 pg/mL to 100 ng/mL with a remarkable detection limit of 0.029 pg/mL (S/N = 3).

Development of reusable electrochemiluminescence sensing microchip for detection of vomitoxin.

In this work, a reusable DNA sensing microchip was developed for detection of vomitoxin (deoxynivalenol, DON) in sorghum using Cd-based core-shell CdSe@CdS quantum dots (QDs) as promising electrochemiluminescence (ECL) emitter. The size-adjustable aqueous phase CdSe@CdS QDs were prepared through homogeneous method, exhibiting strong cathodic ECL emission with a central wavelength of 520 nm in S2O82- coreactant. And gold nanoparticles-modified iron cobalt cyanide hydrate (Fe-Co-Au) was introduced as an accelerator to amplify the ECL signal. ECL signal was quenched after the formation of a double-stranded (dsDNA) S1-S2 by generating an electron transfer system between the emitter and ferrocene (Fc), which are modified on the aptamer (ssDNA S1) and its complement sequence (ssDNA S2), respectively. When the target DON is presence, the aptamer ssDNA S1 will bind to the DON and trigger the unbinding of double strands DNA and the release of the ssDNA S2, thus the signal can be generated. This approach offers a feasible method for the detection of DON within the range of 1 ng/mL to 200 ng/mL.

Lightweight Co3O4/CC Composites with High Microwave Absorption Performance.

With the rapid development of electronic and communication technology for military radars, the demand for microwave-absorbing materials in the low-frequency range with thin layers is growing. In this study, flexible Co3O4/CC (carbon cloth) composites derived from Co-MOFs (metal-organic frameworks) and CC are prepared using hydrothermal and thermal treatment processes. The flexible precursors of the Co-MOFs/CC samples are calcined with different calcination temperatures, for which the material structure, dielectric properties, and microwave absorption performance are changed. With the increases in calcination temperature, the minimum reflection loss of the corresponding Co3O4/CC composites gradually moves to the lower frequency with a thinner thickness. In addition, the Co3O4/CC composites with the 25 wt% filler loading ratio exhibit the minimum reflection loss (RL) of -46.59 dB at 6.24 GHz with a 4.2 mm thickness. When the thickness is 3.70 mm, the effective absorption bandwidth is 3.04 GHz from 5.84 to 8.88 GHz. This study not only proves that the Co3O4/CC composite is an outstanding microwave-absorbing material with better flexibility but also provides useful inspiration for research on wideband microwave absorption materials below 10 GHz.

Nerve growth factor causes epinephrine release dysfunction by regulating phenotype alterations and the function of adrenal medullary chromaffin cells in mice with allergic rhinitis.

The presence of allergic rhinitis (AR) is an increased risk factor for the occurrence of bronchial asthma (BA). Nerve growth factor (NGF), in addition to its key role in the development and differentiation of neurons, may also be an important inflammatory factor in AR and BA. However, the pathogenesis of the progression of AR to BA remains to be elucidated. The present study aimed to investigate the ability of NGF to mediate nasobronchial interactions and explore possible underlying molecular mechanisms. In the present study, an AR mouse model was established and histology of nasal mucosa tissue injury was determined. The level of phenylethanolamine N­methyl transferase in adrenal medulla was determined by immunofluorescence. Primary adrenal medullary chromaffin cells (AMCCs) were isolated and cultured from the adrenal medulla of mice. The expression levels of synaptophysin (SYP), STAT1, JAK1, p38 and ERK in NGF­treated and untreated AMCCs were detected by reverse­transcription­quantitative PCR and western blotting. The epinephrine (EPI) and norepinephrine (NE) concentrations were measured by ELISA. It was found that the expression of SYP in AMCCs was enhanced in the presence of NGF, whereas, the concentration of EPI decreased significantly under the same conditions. Furthermore, NGF mediated the phenotypic and functional changes of AMCCs, resulting in decreased EPI secretion via JAK1/STAT1, p38 and ERK signaling. In conclusion, these findings could provide novel evidence for the role of NGF in regulating neuroendocrine mechanisms.