Incorporation of Mn into the vacant T-atom sites of a BEA zeolite as isolated, mononuclear Mn: FTIR, XPS, EPR and DR UV-Vis studies

Local Charge Transfer Unveils Antideactivation of Ru at High Potentials for the Alkaline Hydrogen Oxidation Reaction

The activity of Ru-based alkaline hydrogen oxidation reaction (HOR) electrocatalysts usually decreases rapidly at potentials higher than 0.1 V (vs a reversible hydrogen electrode (RHE)), which significantly limits the lifetime of fuel cells. It is found that this phenomenon is caused by the overadsorption of the O species due to the overcharging of Ru nanoparticles at high potentials. Here, Mn1Ox(OH)y clusters-modified Ru nanoparticles (Mn1Ox(OH)y@Ru/C) were prepared to promote charge transfer from overcharged Ru nanoparticles to Mn1Ox(OH)y clusters. Mn1Ox(OH)y@Ru/C exhibits high HOR activity and stability over a wide potential range of 0-1.0 V. Moreover, a hydroxide exchange membrane fuel cell with a Mn1Ox(OH)y@Ru/C anode delivers a high peak power density of 1.731 W cm-2, much superior to that of a Pt/C anode. In situ X-ray absorption fine structure (XAFS) analysis and density functional theory (DFT) calculations reveal that Mn in Mn1Ox(OH)y clusters could receive more electrons from overcharged Ru at higher potentials and significantly decrease the overadsorption of the O species on Ru, thus permitting the HOR on Ru to proceed at high potentials. This study provides guidance for the design of alkaline HOR catalysts without activity decay at high potentials.

M-Ge-Si thermolytic molecular precursors and models for germanium-doped transition metal sites on silica

The synthesis, thermolysis, and surface organometallic chemistry of thermolytic molecular precursors based on a new germanosilicate ligand platform, -OGe[OSi(OtBu)3]3, is described. Use of this ligand is demonstrated with preparation of complexes containing the first-row transition metals Cr, Mn, and Fe. The thermolysis and grafting behavior of the synthesized complexes, Fe{OGe[OSi(OtBu)3]3}2 (FeGe), Mn{OGe[OSi(OtBu)3]3}2(THF)2 (MnGe) and Cr{OGe[OSi(OtBu)3]3}2(THF)2 (CrGe), was evaluated using a combination of thermogravimetric analysis; nuclear magnetic resonance (NMR), ultraviolet-visible (UV-Vis), and electron paramagnetic resonance (EPR) spectroscopies; and single-crystal X-ray diffraction (XRD). Grafting of the precursors onto SBA-15 mesoporous silica and subsequent calcination in air led to substantial changes in transition metal coordination environments and oxidation states, the implications of which are discussed in the context of low-coordinate and low oxidation state thermolytic molecular precursors.

Coordination-assembled phosphorescent microstructure from RTP HOF and Eu3+-doping ZGO:Mn phosphors for cancer biomarker amplification detection and information encryption

The ultra-long room temperature phosphorescent hydrogen-bonded organic framework (RTP HOF) materials can achieve long afterglow via ligand hydrogen bond interaction and water implement to suppress the non-radiative decays by matrices rigidification, and its electron donor conjugated structure is first developed as a phosphorescent quencher. The Eu3+/Mn2+ co-doped Zn2GeO4 phosphors (ZGO:Mn, Eu) with abundant metal sites and enhanced phosphorescence were synthesized as response factors and electron acceptors, combined with RTP HOFs to form microstructures featuring multi-color modulation, as an high-level anti-counterfeiting platform and lysophosphatidic acid (LPA) detection unit. LPA is an ideal plasma biomarker for early diagnosis of ovarian and other gynecologic cancers. This detection strategy relies on the differential coordination substitution to restore ZGO:Mn, Eu phosphorescence through synergistic coordination of LPA and the hydrophobic assistance of LPA, and dual functional groups identification of LPA achieve specific detection at the nanomolar level. The anti-counterfeiting platform can fetch specific information by controlling the afterglow distinction and excited light from ZGO:Mn, Eu and RTP HOF. This study not only provides a typical case of the preparation of two phosphors with heterogeneous optical properties, but also expands the application field of combined phosphors as intelligent luminescent materials.

Metal Sites in Zeolites: Synthesis, Characterization, and Catalysis

Zeolites with ordered microporous systems, distinct framework topologies, good spatial nanoconfinement effects, and superior (hydro)thermal stability are an ideal scaffold for planting diverse active metal species, including single sites, clusters, and nanoparticles in the framework and framework-associated sites and extra-framework positions, thus affording the metal-in-zeolite catalysts outstanding activity, unique shape selectivity, and enhanced stability and recyclability in the processes of Brønsted acid-, Lewis acid-, and extra-framework metal-catalyzed reactions. Especially, thanks to the advances in zeolite synthesis and characterization techniques in recent years, zeolite-confined extra-framework metal catalysts (denoted as metal@zeolite composites) have experienced rapid development in heterogeneous catalysis, owing to the combination of the merits of both active metal sites and zeolite intrinsic properties. In this review, we will present the recent developments of synthesis strategies for incorporating and tailoring of active metal sites in zeolites and advanced characterization techniques for identification of the location, distribution, and coordination environment of metal species in zeolites. Furthermore, the catalytic applications of metal-in-zeolite catalysts are demonstrated, with an emphasis on the metal@zeolite composites in hydrogenation, dehydrogenation, and oxidation reactions. Finally, we point out the current challenges and future perspectives on precise synthesis, atomic level identification, and practical application of the metal-in-zeolite catalyst system.

Degradable Magnetic Nanoplatform with Hydroxide Ions Triggered Photoacoustic, MR Imaging, and Photothermal Conversion for Precise Cancer Theranostic

Theranostic agents based on inorganic nanomaterials are still suffered from the nonbiodegradable substances with long-term retention in body and unavoidable biological toxicity, as well as nonspecificity biodistribution with potential damage toward normal tissues. Here, we develop magnetic ions (Fe^III, Fe^II, Gd^III, Mn^II, and Mn^III) coordinated nanoplatform (MICN) with framework structure and modify them with PEG (MICN-PEG). Notably, MICN-PEG demonstrates hydroxide ions (OH^-) triggered the structure collapse along with responsive near-infrared photoacoustic (PA) signal, magnetic resonance imaging (MRI), and photothermal therapy (PTT) performances. Thereby, MICN-PEG is able to remain stable in tumors and exert excellent PA/MRI and PTT effects for multimodal imaging-guided cancer treatment. In contrast, MICN-PEG is gradually collapsed in normal tissues, resulting in the significant improvement of imaging accuracy and treatment specificity. MICN-PEG is gradually cleared after administration, minimizing concerns about the long-term toxicity.

Constructing an unprecedented {MnII38} matryoshka doll with a [Mn18(CO3)9] inorganic core and magnetocaloric effect

An unprecedented inner [Mn₁₈(CO₃)₉] inorganic core and [Mn₂₀] metal-organic periphery compose a high-nuclearity homometallic single-valent {Mn^II₃₈} molecular aggregate with a [Mn₆] ⊂ [Mn₁₂] ⊂ [Mn₈] ⊂ [Mn₁₂] matryoshka doll-like skeleton that displays a significant magnetocaloric effect (MCE).

Photo-driven selective CO2 reduction by H2O into ethanol over Pd/Mn–TiO2: suitable synergistic effect between Pd and Mn sites

The Mn–Pd interaction of Pd/Mn–TiO₂ is a promising catalyst to enhance C₂H₅OH selectivity since Pd with a strong ability to capture and transport electrons and Mn with multifarious activation of the reactant (CO₂ and H₂O).

Simultaneous removal of iron and manganese from acid mine drainage by acclimated bacteria

A bacterial consortium for efficient decontamination of high-concentration Fe-Mn acid mine drainage (AMD) was successfully isolated. The removal efficiencies of Fe and Mn were effective, reaching 99.8 % and 98.6 %, respectively. High-throughput sequencing of the 16S rRNA genes demonstrated that the microbial community had changed substantially during the treatment. The Fe-Mn oxidizing bacteria Flavobacterium, Brevundimonas, Stenotrophomonas and Thermomonas became dominant genera, suggesting that they might play vital roles in Fe and Mn removal. Moreover, the pH of culture increased obviously after incubation, which was benefit for depositing Fe and Mn from AMD. The specific surface area of the biogenic Fe-Mn oxides was 108-121 m²/g, and the surface contained reactive oxygen functional groups (-OH and -COOH), which also improved Fe and Mn removal efficiency. Thus, this study provides an alternative method to treat AMD containing high concentrations of Fe and Mn.

Microporous Frameworks as Promising Platforms for Antibacterial Strategies Against Oral Diseases

Nowadays, the heavy burden of oral diseases such as dental caries, periodontitis, endodontic infections, etc., and their consequences on the patients' quality of life indicate a strong need for developing effective therapies. Bacterial infections played an important role in the field of oral diseases, in-depth insight of such oral diseases have given rise to the demand for antibacterial therapeutic strategies. Recently, microporous frameworks have attracted tremendous interest in antibacterial application due to their well-defined porous structures for drug delivery. In addition, intensive efforts have been made to enhance the antibacterial performance of microporous frameworks, such as ion doping, photosensitizer incorporation as building blocks, and surface modifications. This review article aims on the major recent developments of microporous frameworks for antibacterial applications against oral diseases. The first part of this paper puts concentration on the cutting-edge researches on the versatile antibacterial strategies of microporous materials via drug delivery, inherent activity, and structural modification. The second part discusses the antibacterial applications of microporous frameworks against oral diseases. The applications of microporous frameworks not only have promising therapeutic potential to inhibit bacterial plaque-initiated oral infectious diseases, but also have a wide applicability to other biomedical applications.

Oxalato bridged coordination polymer of manganese(iii) involving unconventional O⋯π-hole(nitrile) and antiparallel nitrile⋯nitrile contacts: antiproliferative evaluation and theoretical studies

Unconventional O⋯π-hole(nitrile) and antiparallel nitrile⋯nitrile contacts have been theoretically investigated for a Mn(iii) coordination polymer considering cytotoxicity, apoptosis, ROS generation, molecular docking and pharmacophore features.

Mn Modified Ni/Bsentonite for CO2 Methanation

To enhance the low-temperature catalytic activity and stability of Ni/bentonite catalyst, Ni-Mn/bentonite catalyst was prepared by introducing Mn into Ni/bentonite catalyst and was used for CO2 methanation. The results indicated that the addition of Mn enhanced the interaction between the NiO and the bentonite carrier, increased the dispersion of the active component Ni and decreased the grain size of the active component Ni, increased the specific surface area and pore volume of the Ni/bentonite catalyst, and decreased the average pore size, which suppressed the aggregation of Ni particles grown during the CO2 methanation process. At the same time, the Mn addition increased the amount of oxygen vacancies on the Ni/bentonite catalyst surface, which promoted the activation of CO2 in the methanation reaction, increasing the low-temperature activity and stability of the Ni/bentonite catalyst. Under the reaction condition of atmospheric pressure, 270 °C, V(H2):V(CO2) = 4, and feed gas space velocity of 3600 mL·gcat−1·h−1, the CO2 conversion on the Ni-Mn/bentonite catalyst with 2wt% Mn was 85.2%, and the selectivity of CH4 was 99.8%. On the other hand, when Mn was not added, the CO2 conversion reached 84.7% and the reaction temperature only raised to 300 °C. During a 150-h stability test, the CO2 conversion of Ni-2wt%Mn/bentonite catalyst decreased by 2.2%, while the CO2 conversion of the Ni/bentonite catalyst decreased by 6.4%.

A novel 2-D Mn selenidostannate(iv) incorporating high-nuclear Mn clusters with spin canting behavior

A solvothermal reaction of SnCl₄·5H₂O, Mn and Se in ethanolamine (Hea) yielded a novel 2-D Mn selenidostannate(iv) [Mn₇(ea)₆(SnSe₄)₂]_n (1), which not only provides the first example of the incorporation of a hepta-nuclear Mn cluster [Mn₇(ea)₆]⁸⁺ into a selenidostannate(iv) framework, but also shows unusual spin canting behavior.

Influence of the nature and environment of manganese in Mn-BEA zeolites on NO conversion in selective catalytic reduction with ammonia

Manganese-containing BEA zeolites, Mn_xSiBEA (x = 1-4 wt%) and Mn_(I.E.)AlBEA, were prepared by a two-step post-synthesis method and a conventional wet ion-exchange, respectively, and applied as catalysts in the selective catalytic reduction of NO with ammonia (NH₃-SCR). The physicochemical analysis of zeolite properties by high-energy-resolution fluorescence-detected XANES (HERFD-XANES) and X-ray emission spectroscopy (XES) uncovered that the coordination, geometry and oxidation state of Mn species are strongly related to the preparation method. Additionally, the study of catalyst acidity by FTIR spectroscopy with CO and pyridine probe molecules provided important insight into the number and type of acidic centres present on the catalyst surface. The catalytic results revealed that NO conversion depended on the state and content of Mn. The zeolites obtained by the two-step post-synthesis method and with a low Mn content were very active in the medium temperature range (NO conversion ∼100%) with simultaneous high selectivity to N₂ due to the presence of isolated, framework Mn(iii) and Mn(ii) species. The N₂O formation was especially high in the case of catalysts containing extra-framework polynuclear Mn species and negligible in the case of Mn_(I.E.)AlBEA containing predominantly isolated, extra-framework Mn(ii) species.

Insights into the mechanism for the selective catalytic reduction of NOxwith NH3on (MnO)2+/ZSM-5: A DFT study

In this work, the reaction mechanisms for the selective catalytic reduction (SCR) of nitrogen oxides (NOx) with NH3on a (MnO)[Formula: see text]/ZSM-5 catalyst were investigated based on the density functional theory (DFT) method. Our calculations showed that the NH3could strongly adsorb on the (MnO)[Formula: see text]/ZSM-5 catalyst as compared to NO. The proposed reaction pathway, NH3(ads)[Formula: see text]NH[Formula: see text]H[Formula: see text]NH2(ads) [Formula: see text] NO(ads)[Formula: see text] NH2NO[Formula: see text]NHNO [Formula: see text] H[Formula: see text]N[Formula: see text]H2O, was more favorable with smaller activation barrier (1.40[Formula: see text]eV) of the rate-determining step. The compared reaction process that the adsorbed NH3reacted directly with adsorbed NO was difficult to happen for the higher activation barrier. Meanwhile, the framework oxygen participated in the oxidation process from ammonia to NH2, thereby increasing its availability for the reaction. In addition, the regeneration process of active site in the presence of NH3and NO2was explored, and the rate-limiting step possessed an activation barrier of 1.46[Formula: see text]eV. The NH2NO species was formed as the crucial intermediate and subsequently decomposed into the N2and H2O.

Selective Chemical Conversion of Sugars in Aqueous Solutions without Alkali to Lactic Acid Over a Zn-Sn-Beta Lewis Acid-Base Catalyst

Lactic acid is an important platform molecule in the synthesis of a wide range of chemicals. However, in aqueous solutions without alkali, its efficient preparation via the direct catalysis of sugars is hindered by a side dehydration reaction to 5-hydroxymethylfurfural due to Brønsted acid, which originates from organic acids. Herein, we report that a previously unappreciated combination of common two metal mixed catalyst (Zn-Sn-Beta) prepared via solid-state ion exchange synergistically promoted this reaction. In water without a base, a conversion exceeding 99% for sucrose with a lactic acid yield of 54% was achieved within 2 hours at 190 °C under ambient air pressure. Studies of the acid and base properties of the Zn-Sn-Beta zeolite suggest that the introduction of Zn into the Sn-Beta zeolite sequentially enhanced both the Lewis acid and base sites, and the base sites inhibited a series of side reactions related to fructose dehydration to 5-hydroxymethylfurfural and its subsequent decomposition.