Chemistry methods : new approaches to solving problems in chemistry最新文献

In recent years, lithium manganese iron phosphate (LiMn_xFe_1–xPO₄, LMFP) has attracted considerable interest, primarily because of its high energy density, remarkable thermal stability, and relatively low manufacturing costs, thus positioning it as a highly promising contender for the next generation of lithium-ion battery cathodes. However, low electronic conductivity and ionic diffusion rate of LMFP hinder its ability in rapid charging applications. Currently, systematic reviews on this topic are still relatively scarce, and thus the aim of this review is to offer a thorough summary of the advancements in research concerning LMFP cathode materials. This review focuses on the structural and performance characteristics of LMFP, along with the effects of various modification strategies on its electrochemical performance. An in-depth analysis is conducted on exotic element doping, surface coating, and material nanostructuring, with a focus on their mechanisms for improving the electrochemical characteristics of LMFP. In conclusion, the review outlines potential future development directions for LMFP in the realms of interface engineering and structural design. This review aims to provide valuable perspectives into the research and innovation of LMFP materials, promote the advancement of high-performance, low-cost LMFP cathode materials, and ultimately advance the technology and commercial applications of lithium-ion batteries.

Hypervalent halogen-containing compounds are recognized as green reagents for chemical synthesis. Iodonium (III) salts are regarded as the most beneficial classes of hypervalent halogen derivatives because of their advantageous reactivity and biological activities. A solvent-free, high-yielding, mechanochemical route is developed for the synthesis of diphenyleneiodonium (III) salts (DPI⁺X⁻). The optimal synthesis of several DPI salts, including triflate, mesylate, esylate, besylate, tosylate, and saccharinate, is reported in the study with high reaction yields. All reported salts are thoroughly characterized with the help of powder and single-crystal X-ray diffraction analysis. We also report the isolation of a new polymorph of DPI chloride salt, DPI-CHL2 which appears concomitantly with the known polymorph, DPI-CHL1. A optimized protocol for obtaining the pure bulk phases of the polymorphs is also presented in the study. We also performed a detailed computational analysis of the synthesized diphenyleneiodonium salts with the help of morphology predictions, and Hirshfeld surface analysis, to understand the effect of crystal morphology, crystal packing, and counterions on their solid-state reactivities. The reactivity comparison can help choose the most reactive DPI salts for further use as reagents or catalysts in mechanochemical solid-state reactions.

Crystalline porous materials formed through intermolecular interactions such as hydrogen bonding interactions and van der Waals forces are known as hydrogen-bonded organic frameworks (HOFs). As a type of HOFs, charge-assisted HOFs are composed of organic acids and bases jointly interacted through hydrogen bonding and electrostatic interactions. Charge-assisted HOFs show the advantages of high crystallinity, ease of processing, recyclability, and low toxicity. Moreover, the introduction of additional electrostatic interactions can enhance the binding energy of hydrogen bonds, which not only improves the stability of the framework but also endows the channels with unique charge-separation characteristics. This review highlights the important factors affecting the design and synthesis of charge-assisted HOFs, including the acidity and basicity of monomers, solvent effects, and the role of topology in guiding the design. Additionally, it briefly introduces the applications of charge-assisted HOFs in the fields of negative linear compressibility, proton conduction, atmospheric water harvesting, gas adsorption and separation, molecular rotors, optics, and biological applications. The challenges and future prospects in the design and synthesis of charge-assisted HOFs are also explored.

Biochar materials have become an emerging choice for electromagnetic interference (EMI) shielding functional materials due to their inherent layered porous structure and sustainability. However, previous studies have primarily focused on the compositional and structural design of biochar with functional nanomaterials and overlooked the relationship between its intrinsic physicochemical properties and EMI shielding performance. In this study, the relationship between the preparation conditions of bamboo charcoal (BC) and its subsequent microstructure evolution, phase composition, electrical conductivity, and EMI shielding properties is investigated. BC with abundant hierarchical pores and continuous conductive networks is prepared by a one-step pyrolysis process. This structure facilitates the internal conduction of electrons, thereby enhancing EMI shielding performance. Notably, the electrical conductivity of BC is sharply improved from 1.3 × 10⁻⁵ to 31.2 S cm⁻¹ as the pyrolysis temperature increases from 600 to 1000 °C. Correspondingly, the EMI shielding effectiveness (EMI SE) improves from 0.29 to 73.63 dB with a shielding efficiency exceeding 99.99%, demonstrating exceptional EM wave shielding capabilities. The continuous conductive networks induced by increased carbonization degree cause a pronounced impedance mismatch between the air and the BC surface, leading to intense EM wave reflections. This work unlocks a novel prospect for the high-value utilization of bamboo resources.

This review provides comprehensive aspects of the interaction of water with zeolites, focusing on its influence on the structural and catalytic properties of zeolites. It details how water can alter zeolite acidity by forming hydrogen bonding or hydronium ions through different modes of water in zeolite topologies. Moreover, it summarizes the risks of zeolite stability loss via hydrolysis of Si−O−T bonds to influence the stability, structure, and catalytic reactivity of zeolites. To address water interference, various strategies for water removal from zeolite frameworks are reviewed and proposed from the structural perspective of the zeolites. By combining advanced in-situ techniques, FTIR and solid-state NMR have proven effective in providing atomic-level insights, as they eliminate the masking effects of water to enable precise characterization of the zeolite framework. This work underscores the importance of these methods in minimizing the influence of water, enhancing the reliability of zeolite characterization for catalytic applications, and providing insights into recent advancements, challenges, and future directions in the related fields.

Block copolymer self-assembly into nanoparticles of defined size and morphology is facilitated via continuous flow synthesis methods. Using flow, nanoparticles are obtained at higher rates, with improved consistency, under greener conditions and with significantly reduced batch-to-batch variability when compared to traditional batch processes. The methodology to formulate block copolymers in a flow setup is described, and design strategies explained. Further, the purification of the obtained particles via flow dialysis is described, marking a second important step in synthesis, which when performed in batch is time and resource intensive. The described methods open the pathway for reproducible block copolymer nanoparticle synthesis, and towards automation and high-throughput screening of materials.

Ligand-protected atomically precise metal nanoclusters (MNCs) have attracted peculiar interest not only for their distinct molecular structure but also for their unique physiochemical properties, providing an ideal platform for developing structure-activity correlation at the atomic level. In this work, we have presented the isolation of two nanoclusters (NCs) [Cu₁₄H₁₀(DMBT)₃(PPh₃)₈][BF₄] (Cu₁₄) and [Cu₄₁H₂₁Cl₈(DMBT)₁₂(PPh₃)₆] (Cu₄₁) [DMBT=2,4-dimethylbenzenethiol and PPh₃=Triphenylphosphine] upon manipulating the concentration of thiol ligand. A correlation between thiolate ligand's concentration and product selectivity was noticed. Further, the presence of R and S isomerism was observed in Cu₁₄ unit cell. Single Crystal X-ray Diffraction (SC-XRD) data revealed that Cu₁₄ crystallized in the cubic space group Pa-3, while Cu₄₁ in hexagonal space group P6₃/m. The crystal structure of Cu₁₄ and Cu₄₁ NCs were supported using high resolution electrospray mass spectrometry (ESI MS) and other spectroscopic approaches. We believe this study will serve as a guide for controllable synthesis of MNCs.

Understanding structural dynamics on the nanoscale is essential for progress in current research areas such as catalysis, energy storage, and nanotechnology. In this study, we introduce an in-house electrochemical flow cell for real-time small-angle X-ray scattering (SAXS) experiments to monitor cobalt hydroxide (Co(OH)₂) electrocrystallization under controlled conditions. Co(OH)₂ films were produced via cathodic electrochemical deposition (CED) from a Co(NO₃)₂ solution. SAXS data, complemented by electron microscopy and spectroscopy, reveal the formation of nanoscale Co(OH)₂ platelets with an average thickness of ~13 nm and a lateral size of ~600 nm. Time-resolved in-situ SAXS tracks the steady growth of these platelets, from 7.8 nm to 15.7 nm thickness over 120 min. In addition, SAXS measurements demonstrate the influence of citrate ligands, which initially suppress platelet formation and stabilize spherical nanostructures. As citrate depletes in the electrolyte, platelets begin to form, indicating a dynamic shift in crystallization mechanism. By employing in-situ SAXS, we successfully monitor the temporal evolution of nanoscale structures, offering insights into the mechanisms governing crystallization under electrochemically controlled conditions. These findings underscore the versatility of in-house SAXS setups for real-time analysis of material formation and growth processes, with implications for tailoring the synthetic parameters towards materials with dedicated nanostructures for various technological applications.

The fundamentals of in situ formation of iron carbides are required for the tailored design of Fe-based catalysts for the efficient conversion of CO₂ to higher hydrocarbons. Herein, time-resolved in situ X-ray absorption spectroscopy has been used to elucidate the mechanism of the formation of Fe₅C₂ from ferrous oxalate (FeC₂O₄) at 350 °C using a H₂/CO=3 reaction feed. Regardless of the kind of alkali metal promoter and reaction pressure (1 or 7.5 bar), FeC₂O₄ is first decomposed to FeO followed by the conversion of the latter to Fe₅C₂. Further insights into the above transformations were derived by kinetic analysis using a Johnson–Mehl–Avrami–Erofeev–Kolmogorov model and kinetics-constrained neural ordinary differential equations method. Both approaches revealed that the formation of FeO at 1 bar follows a nucleation mechanism, while a diffusion mechanism has a higher contribution at 7.5 bar. The latter mechanism is valid for the conversion of FeO to Fe₅C₂ at both pressures. Alkali metal promoters were found to accelerate the rate of Fe₅C₂ formation. This rate decreases with increasing total pressure due to the stabilization of FeO.

The Front Cover illustrates that by paw-holding, wild sea otters ensure they stay together and do not drift apart in their sleep. This comes from a concept of no herd member being left behind. If the experimental conditions are met, the same phenomenon is observed in the study by Renaud Blaise Jolivet and co-workers, where K⁺ ions and cage molecules interact in the solution, forming species with significantly higher Xe encapsulation rates. The preferential caging of Xe by CB[6]-alkali pairs is seen as an analogy to the paw-holding-based social gathering of sea otters. For more details, see the Research Article by Renaud Blaise Jolivet and co-workers (DOI: 10.1002/cmtd.202400033).