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The activation of N₂ under mild conditions remains a significant challenge in chemistry. Understanding how the composition of ligands modulates the reactivity of metal centers is pivotal for the rational design of efficient catalysts for nitrogen fixation. Herein, the reactions between polynuclear niobium oxynitride anions Nb4N5‐xOx− (x=0–5) and N2 were investigated by employing mass spectrometry, photoelectron imaging spectroscopy, and theoretical calculations. The rate constants of Nb4N5‐xOx−/N2 gradually decrease for x=0 to x=4, and then increase again for x=5. The sharp increase of the rate constants of Nb4O5−/N2 corresponds to a decrease in the electron detachment energy of the Nb4O5− cluster in the photoelectron spectroscopic experiments. Theoretical calculations suggest that the low‐coordinated Nb−Nb sites in Nb4N5‐xOx− (x=0–5) behaves as the active centers to bind N2 in the side‐on/end‐on manner. Mechanistic analysis reveals that reducing the N/O ratio leads to higher electron densities on the active Nb−Nb centers and decreased positive charge on the metal atoms, which hinders the approach of N2 to the clusters. This finding discloses fundamental insights into the impact of N/O ratio in fine‐tuning the reactivity of metal centers toward N2 adsorption in related catalytic processes. [ABSTRACT FROM AUTHOR]

Searching the global minimum (GM) structures of metal clusters is of great importance in cluster science. Very recently, the global optimization method based on deep neural network combined with transfer learning (DNN-TL) was developed to improve the efficiency of optimizing the GM structures of metal clusters by greatly reducing the number of samples to train the DNN. Aiming to further enhance the sampling efficiency of the potential energy surface and the global search ability of the DNN-TL method, herein, an advanced global optimization method by embedding genetic algorithm (GA) into the DNN-TL method (DNN-TL-GA) is proposed. In the case of the global optimization of Ptn (n=9–15) clusters, the DNN-TL-GA method requires only a half number of samples at most with respect to the DNN-TL method to find the GM structures. Meanwhile, the DNN-TL-GA method saves about 70%-80% of computational costs, suggesting the significant improved efficiency of global search ability. There are much more samples distributed in the area of the potential energy surface with low energies for DNN-TL-GA (25% for Pt14) than for DNN-TL (<1% for Pt14). The success of the DNNTL-GA method for global optimization is evidenced by finding unprecedented GM structures of Pt16 and Pt17 clusters. [ABSTRACT FROM AUTHOR]

A fundamental understanding of the exact structural characteristics and reaction mechanisms of interface active sites is vital to engineering an energetic metal–support boundary in heterogeneous catalysis. Herein, benefiting from a newly developed high-temperature ion trap reactor, the reverse water–gas shift (RWGS) (CO2 + H2 → CO + H2O) catalyzed by a series of compositionally and structurally well-defined RhnVO3,4− (n = 3–7) clusters were identified under variable temperatures (298–773 K). It is discovered that the Rh5–7VO3,4− clusters can function more effectively to drive RWGS at relatively low temperatures. The experimentally observed size-dependent catalytic behavior was rationalized by quantum-chemical calculations; the framework of RhnVO3,4− is constructed by depositing the Rhn clusters on the VO3,4 "support", and a sandwiched base–acid–base [Rhout−–Rhin+–VO3,4−; Rhout and Rhin represent the outer and inner Rh atoms, respectively] feature in Rh5–7VO3,4− governs the adsorption and activation of reactants as well as the facile desorption of the products. In contrast, isolated Rh5–7− clusters without the electronic modification of the VO3,4 "support" can only catalyze RWGS under relatively high-temperature conditions. [ABSTRACT FROM AUTHOR]

BACKGROUND: Phenolic endocrine‐disrupting chemicals (EDCs) are widespread and easily ingested through the food chain. They pose a serious threat to human health. Magnetic solid‐phase extraction (MSPE) is an effective sample pre‐treatment technology to determine traces of phenolic EDCs. RESULTS: Magnetic covalent organic framework (COF) (Fe3O4@COF) nanospheres were prepared and characterized. The efficient and selective extraction of phenolic EDCs relies on a large specific surface and the inherent porosity of COFs and hydrogen bonding, π–π, and hydrophobic interactions between COF shells and phenolic EDCs. Under optimal conditions, the proposed magnetic solid‐phase extraction‐high‐performance liquid chromatography–ultra violet (MSPE‐HPLC‐UV) based on the metallic covalent organic framework method for phenolic EDCs shows good linearities (0.002–6 μg mL−1), with R2 of 0.995 or higher, and low limits of detection (6–1.200 ng mL−1). CONCLUSION: Magnetic covalent organic frameworks (Fe3O4@COFs) with good MSPE performance for phenolic EDCs were synthesized by the solvothermal method. The magnetic covalent organic framework‐based MSPE‐HPLC‐UV method was applied successfully to determine phenolic EDCs in beverage and water samples with satisfactory recoveries (90.200%–123%) and relative standard deviations (2.100%–12.100%). © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Catalytic NO reduction by CO into N 2 and CO 2 is imperative owing to the increasingly rigorous emission regulation. Identifying the nature of active sites that govern the reactivity and selectivity of NO reduction is pivotal to tailor catalysts, while it is extremely challenging because of the complexity of real-life systems. Guided by our newly discovered triatomic Lewis acid-base-acid (LABA, Ce δ+ -Rh δ- -Ce δ+ ) site that accounts for the selective reduction of NO into N 2 catalyzed by the RhCe 2 O 3 - cluster in gas-phase experiments, the reactivity of the RhM 2 O 3 - (M = Ta, V, and Al) clusters in catalytic NO reduction by CO was explored. We determined theoretically that the LABA site still prevails to reduce NO to N 2 mediated by RhTa 2 O 3 - and RhV 2 O 3 - , and the strong M-oxygen affinity was emphasized to construct the LABA site. An overall assessment highlights that RhV 2 O 3 - functions as a more promising catalyst because the well-fitting V-O bonding strength facilitates both elementary reactions of NO reduction and CO oxidation.

Background: Helicobacter pylori ( H. pylori ) infection can cause extensive apoptosis of gastric epithelial cells, serving as a critical catalyst in the progression from chronic gastritis, gastrointestinal metaplasia, and atypical gastric hyperplasia to gastric carcinoma. Prompt eradication of H. pylori is paramount for ameliorating the pathophysiological conditions associated with chronic inflammation of the gastric mucosa and the primary prevention of gastric cancer. Acacetin, which has multifaceted pharmacological activities such as anti-cancer, anti-inflammatory, and antioxidative properties, has been extensively investigated across various domains. Nevertheless, the impact and underlying mechanisms of action of acacetin on H. pylori -infected gastric mucosal epithelial cells remain unclear., Aim: To explore the defensive effects of acacetin on apoptosis in H. pylori -infected GES-1 cells and to investigate the underlying mechanisms., Methods: GES-1 cells were treated with H. pylori and acacetin in vitro. Cell viability was assessed using the CCK-8 assay, cell mortality rate via lactate dehydrogenase assay, alterations in cell migration and healing capacities through the wound healing assay, rates of apoptosis via flow cytometry and TUNEL staining, and expression levels of apoptosis-associated proteins through western blot analysis., Results: H. pylori infection led to decreased GES-1 cell viability, increased cell mortality, suppressed cell migration, increased rate of apoptosis, increased expressions of Bax and cle-caspase3, and decreased Bcl-2 expression. Conversely, acacetin treatment enhanced cell viability, mitigated apoptosis induced by H. pylori infection, and modulated the expression of apoptosis-regulatory proteins by upregulating Bcl-2 and downregulating Bax and cleaved caspase-3., Conclusion: Acacetin significantly improved GES-1 cell viability and inhibited apoptosis in H. pylori -infected GES-1 cells, thereby exerting a protective effect on gastric mucosal epithelial cells., Competing Interests: Conflict-of-interest statement: The authors declare that they have no competing interests., (©The Author(s) 2024. Published by Baishideng Publishing Group Inc. All rights reserved.)

Gas-phase metal clusters are ideal models to explore transition-metal-mediated N 2 activation mechanism. However, the effective design and search of reactive clusters in N 2 activation are currently hindered by the lack of clear guidelines. Inspired by the Sabatier principle, we discovered in this work that N 2 initial adsorption energy (Δ E ads ) is an important parameter to control the N 2 activation reactivity of metal clusters in the gas phase. This mechanistic insight obtained from high-level calculations rationalizes the N 2 activation reactivity of many previously reported metal clusters when combined with the known factor determining the N≡N cleavage process. Furthermore, based on this guideline of Δ E ads , we successfully designed several new reactive clusters for cleaving N≡N triple bond under mild conditions, including FeV 2 S 2 - , TaV 2 C 2 - , and TaV 2 C 3 - , the high N 2 activation reactivity of which has been fully corroborated in our gas phase experiments employing mass spectrometry with collision-induced dissociation. The importance of Δ E ads revealed in this work not only reshapes our understanding of N 2 activation reactions in the gas phase but also could have implication for other N 2 activation processes in the condensed phase. The more general establishment of this new perspective on N 2 activation reactivity warrants future experimental and computational studies.

A fundamental understanding of the exact structural characteristics and reaction mechanisms of interface active sites is vital to engineering an energetic metal-support boundary in heterogeneous catalysis. Herein, benefiting from a newly developed high-temperature ion trap reactor, the reverse water-gas shift (RWGS) (CO 2 + H 2 → CO + H 2 O) catalyzed by a series of compositionally and structurally well-defined Rh n VO 3,4 - ( n = 3-7) clusters were identified under variable temperatures (298-773 K). It is discovered that the Rh 5-7 VO 3,4 - clusters can function more effectively to drive RWGS at relatively low temperatures. The experimentally observed size-dependent catalytic behavior was rationalized by quantum-chemical calculations; the framework of Rh n VO 3,4 - is constructed by depositing the Rh n clusters on the VO 3,4 "support", and a sandwiched base-acid-base [Rh out - -Rh in + -VO 3,4 - ; Rh out and Rh in represent the outer and inner Rh atoms, respectively] feature in Rh 5-7 VO 3,4 - governs the adsorption and activation of reactants as well as the facile desorption of the products. In contrast, isolated Rh 5-7 - clusters without the electronic modification of the VO 3,4 "support" can only catalyze RWGS under relatively high-temperature conditions.