Modulated Structure Research Articles

Research Progress on the Application of MOF Materials in Lithium‐Ion Batteries

ABSTRACTLithium‐ion batteries (LIBs) have established themselves as the preferred power sources for both pure electric and hybrid vehicles, attributable to their exceptional characteristics, including prolonged cycle life, elevated energy density, and minimal self‐discharge rates. Metal‐organic frameworks (MOFs), as innovative functional molecular crystal materials, exhibit promising application prospects in LIBs. This paper provides a comprehensive overview of the latest advancements in the synthesis techniques and structural modulation of MOFs and their derivative materials. It particularly emphasizes a thorough exploration of the utilization of MOFs and their derivatives in the anode, cathode, and separators of LIBs. Additionally, this paper delves into the current obstacles encountered by MOFs in LIB applications and offers insights into their potential future development.

Towards High-Performance Li-Rich Cathode Materials: from Morphology Design to Electronic Structure Modulation.

Lithium-rich cathode materials (LRMs) have garnered significant interest owing to their high reversible discharge capacity (exceeding 250 mAh g⁻¹), which is attributed to the redox reactions of transition metal (TM) ions as well as the distinctive redox processes of oxygen anions. However, there are still many problems, such as their relatively poor rate performance and voltage fading and hysteresis, hindering their practical applications. Herein, the recent insights into the mechanisms and the latest advancements in the research of LRMs are discussed. Strategies to promote the performance of LRMs are discussed following a top-down approach from the morphology design to electronic structure modulation. Finally, the ongoing efforts in this area are also discussed to inspire more new ideas for the future development of LRMs.

Tuning Strategies of Indium‐Based Catalysts for Electrocatalytic Carbon Dioxide Reduction

In electrocatalytic carbon dioxide reduction (CO2RR), indium (In)‐based catalysts with low toxicity and environmental benefits are renowned for their specific high selectivity for formic acid and intrinsic inertia for the competing hydrogen evolution reaction. However, recent studies have reported various products over In‐based catalysts showing comparable or even higher selectivity for carbon monoxide (CO) than for formic acid (HCOOH), puzzling the reaction pathway for CO2 reduction. This article presents a comprehensive review of recent studies on electrocatalytic CO2RR over In‐based catalysts highlighting the formation pathway of specific products. First, the mechanism of electrocatalytic CO2RR with the multiple reaction pathways is concluded considering the relationship between reaction intermediates and selectivity. Furthermore, the regulation strategies for multiple product formation are summarized, including crystalline phase engineering, alloying, nanostructuring, and structural modulation of In single atom, where the effect of key intermediates (*COOH, *OOCH, and *OCHO) on product generation is systematically discussed to achieve high selectivity. Finally, the intrinsic regulation mechanisms of these strategies are analyzed and the challenges and opportunities for the development of next‐generation In‐based catalysts are proposed.

Zero-valent Transition Metal Intercalation into 2D Materials: Electronic Structure Modulation and Applications.

With state-of-the-art modulation of the electronic structure, novel physiochemical properties are anticipated for two-dimensional (2D) materials for a wide variety of potential applications. Due to the presence of charge transfer from transition metal guests and 2D material hosts, intercalation of zero-valent transition metal atoms into the van-der Waals gap of 2D materials are ideal approach to tuning the electronic structure of 2D materials. In this paper, several electronic structure and activity investigations of zero-valent transition metal intercalations of 2D materials, as well as the general concepts behind the experimental exploration, were introduced. Specifically, the transition metal intercalation render 2D materials novel physicochemical properties with potential applications ranges from electrocatalysis, small molecule identification to spintronics. Based on the works and concepts introduced in this paper, several challenges and opportunities related to this field were proposed from our perspective.

Energy-Level Alignment at TiO2@NH2-MIL-125 Interface for High-Performance Gas Sensing.

Metal oxide (MO)-based chemiresistive sensors have great potential in environmental monitoring, security protection, and disease diagnosis. However, the thermally activated sensing mechanism in pristine MOs leads to high working temperature and poor selectivity, which are the main challenges impeding practical applications. Precise modulation of the band structure at the heterojunction interfaces of MOs offers the opportunity to unlock unique electrical and optical properties, enabling us to overcome these challenges. Metal-organic frameworks (MOFs) with tunable structures are promising materials for aligning the energy levels at the heterojunctions of MOs. Herein, we report the energy-level structural engineering of MO@MOF heterojunctions to optimize chemiresistive sensing performance. The interface was flexibly modulated from a straddling gap to a staggered gap by -NH2 functionalization of TiO2@(NH2)x-MIL-125, varying x from 0 to 1 and 2, respectively. TiO2@(NH2)x-MIL-125 combines the advantages of MOs and MOFs to synergistically improve gas-sensing properties. As a result, TiO2@NH2-MIL-125 is the first light-activated material to detect NO2 at 1 ppb with a response time of < 0.3 min at room temperature. It also exhibited excellent selectivity and long-term stability. Our study underscores the potential of energy band engineering in creating high-performance sensors, offering a strategy to overcome current material limits.

Pseudohalide Anions Driven Structural Modulation in Distorted Tetrahedral Manganese(II) Hybrids Toward Tunable Green‐Red Emissions

AbstractMn(II)‐based halides have recently garnered significant interest as emerging luminescence materials for diverse photonic applications. Generally, Mn(II) hybrids with tetrahedral coordination show green emission, however, ones with octahedral coordination give red emission. Herein, we design the synthesis of tetrahedral Mn(II) pseudohalide hybrids, (RPh3P)2MnBrxNCS4−x (R=phenyl, pentyl or methyl; Ph3P=triphenylphosphine; x=1–3), achieved by gradually substituting bromides with pseudohalides (NCS−). Compared to the green‐emitting A2MnBr4 (512 nm), the mixed hybrids exhibit significantly distorted [MnBrxNCS4−X] tetrahedra with high dipole moment, thus leading to the distinct Stokes shift energies and noticeable red shift emission in the range of 549–613 nm. Furthermore, the photoluminescence quantum yield (PLQY) of these hybrids correlates strongly with the pair correlation function of Mn(II) ions, specifically the Mn⋅⋅⋅Mn distance. These findings highlight the critical role of dipole moments in determining the emission properties and expand the luminescent family of Mn(II) pseudohalide hybrids.

Exploring stress-dependent impedance behavior via magnetization dynamics in amorphous magnetic fibers in high frequency: Experimental and modeling

The magnetoelastic effect plays a crucial role in influencing the magnetization dynamics and impedance characteristics of magnetic fibers (MFs). In this work, we investigate the modulation of the domain structure and impedance behaviors under stress within Co-based MFs aided by experimental and theoretical approaches. The remarkable changes of natural ferromagnetic resonance and the transition of domain inclination angles indicate that the stress-impedance effect derives from the evolution of the magnetic domain structure and anisotropy field, which are induced by magnetoelastic coupling. The ferromagnetic resonance linewidths over a range of applied tensile strains (0–0.54%) serve to elucidate the contribution of magnetoelastic coupling to magnetic damping in ferromagnetic fibers. By utilizing the shell domain expansion method, we derive circular dynamic permeability and compute the impedance properties at high frequencies of MFs under multi-field stimulus. The theoretical model accurately predicts key features of magnetization dynamics, the evolution of ferromagnetic resonance, and impedance curves of MFs, in good agreement with experimental results including very fine observation of domain evolution. This comprehensive approach provides profound insights into the stress modulation of impedance characteristics, with implications for sensing applications of MFs.

Multi-plateau water adsorption of pyrene-based covalent organic frameworks for potential humidity control

Indoor air humidity significantly influences air quality, human health, and work performance. Covalent organic frameworks (COFs) have been proven effective in humidity regulation; however, challenges remain in broadening their range of humidity control. This study designs and synthesizes a series of pyrene-based crystalline COFs as humidity control materials, investigating the moisture adsorption–desorption characteristics under structural modulation. Among these, PY-3,3′-BPY-COF exhibits unique multi-step adsorption isotherms, achieving the highest water uptake capacity (1 g/g) and efficient water uptake-release cycles. Theoretical and experimental analyses reveal a linear relationship between the maximum water uptake rate and the specific surface area, while the adsorption inflection points are influenced by the water binding energy and pore size distribution. Importantly, the introduction of strong binding sites promotes multi-step adsorption phenomena, significantly enhancing the humidity control capabilities of COFs across a wide range of humidity levels. This research introduces an innovative approach for broad-spectrum indoor humidity control and reveals the fundamental relationship between the structure characteristics of COFs and their capabilities in water adsorption and release.

Efficient electrochemical water oxidation catalyzed by a novel nickel complex: Critical effect of the flexibility of pyridine-amine based pentadentate ligand on catalytic property

Efficient electrochemical water oxidation can be realized by reasonable modulation of the ligand structure of metal complex-based molecular water oxidation catalysts (WOCs). Herein, the synthesis and prowess in electrocatalytic water oxidation of a mononuclear water-soluble nickel complex, [Ni(tmbptu)(OH2)](ClO4)2 (1, tmbptu = 2,6,10-trimethyl-1,11-bis(2-pyridyl)-2,6,10-triazaundecanone), is reported for the first time. Complex 1 is found to be an efficient homogeneous WOCs under near neutral condition with long-term catalytic stability by a series of characterizations, including dynamic light scattering (DLS) measurement, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray (EDX) analysis, chelation experiment, and Fe3+ test. Electrochemical tests reveal that water oxidation is accomplished via the generation of NiIV species generated by two successive e−/H+ proton coupled electron transfer (PCET) processes. Astonishingly, compared to the homologous complex [Ni(tmbptn)(OH2)](ClO4)2 (2, tmbptn = 2,5,8-trimethyl-1,9-bis(2-pyridyl)-2,5,8-triazanonane), which is a well-defined molecular WOC with high catalytic onset overpotential, 1 displays lower onset overpotential and much higher catalytic activity. This work suggesting that though the tertiary amine coordination environment have gain effect on the redox potential of metal center due to its poor sigma-donor effect, resulting in high onset overpotential of metal complex for water oxidation, this negative impact of the pyridine-amine ligand on the catalytic properties of complex can be weaken by adjusting the flexibility of backbone of those ligands.

Electronic structure modulation and peroxymonosulfate activation mechanism of N-doped MnCo2O4: A study on the efficient catalytic degradation of sulfamethoxazole

In this study, a nitrogen-doped MnCo2O4 composite material (nN-MCO) was successfully synthesized via a urea-assisted thermal treatment method and applied for the activation of peroxymonosulfate (PMS) to degrade sulfamethoxazole (SMX). By introducing metal-N (M−N) bonds, the concentration of oxygen vacancies on the catalyst surface and its electron transfer capability with PMS were significantly enhanced. Experimental characterizations demonstrated that nitrogen doping not only strengthened the covalency of the metal-O (M−O) bonds but also facilitated the formation of electron-rich metal sites through electronic rearrangement, further improving the adsorption and activation of PMS. The 2 N-MCO catalyst successfully degraded 98.0 % of SMX within 5 min and maintained a removal efficiency of 85.0 % after four consecutive cycles. The study revealed that 1O2, SO4−, OH and O2− were all involved in the degradation of SMX, with 1O2 identified as the dominant reactive oxygen species. This work presents a simple and effective nitrogen-doping strategy for surface modification of spinel-based catalysts, enhancing the MnCo2O4 composite’s electronic structure, strengthening metal–oxygen bonds, and creating electron-rich sites. These modifications promote oxygen vacancies, improve electron transfer, and enable efficient reactive oxygen species (ROS) generation, offering valuable insights and theoretical support for PMS-based oxidation processes in pollutant treatment.

Understanding the Structural Modulations in Twisted Donor-Acceptor-Donor (D-A-D) Systems for Boosting Type I Photosensitizing Photocatalytic Activity.

Supramolecular assemblies based on the twisted donor-acceptor-donor (D-A-D) building block Qx-Ind have been developed, which interestingly, due to the balanced angle of twist (38.28°), high intermolecular charge transfer, and crystallization induced emission (CIE) characteristics, exhibit high molar absorptivity and a long-lived "lighted" excited state at the supramolecular level. The validity of the design concept was examined by preparing CIE active D-A-D system Qx-Indaz (weak donor, low angle of twist: 35.45°), in which, due to the insertion of an additional binding site for noncovalent interactions, a drastic change in the photophysical behavior is observed. The combined spectroscopic studies of all the compounds unveil the strong impact of modulation of the angle of twist and intermolecular charge transfer upon photophysical behavior in the aggregated state. Due to the favorable photophysical behavior, the supramolecular assemblies of Qx-Ind exhibit high type I photosensitizing activity in comparison to Qx-Indaz. The superior type I photosensitizing activity of Qx-Ind assemblies is manifested in their ability to efficiently catalyze the aerobic oxidative synthesis of quinazolin-4(3H)-ones (via type I ROS) from 2-aminobenzamide and aromatic aldehydes in the absence of additional additives (base/oxidant). Unlike photocatalytic nanoassemblies reported in the literature, due to the CIE characteristics, Qx-Ind does not require preliminary preparation and could be directly introduced in the solid state to reaction media. Thus, the present work demonstrates a simple strategy of upgrading type I photosensitizing activity by improving the ground/excited state behavior of a twisted D-A-D system through modulation of the angle of twist and charge transfer characteristics.

A general strategy for enhancing the performance of Ga2O3-based self-powered solar-blind photodetectors through band structure engineering

Abstract The spectral response of Ga2O3 almost perfectly covers the 200~280 nm solar-blind ultraviolet wavelength range, making it an ideal semiconductor material for fabricating solar-blind ultraviolet photodetectors. However, due to the considerably deep valence band energy of Ga2O3 the construction of heterojunctions typically induces a significant valence band offset (EV). Herein, we present a band engineering approach to improve the performance of Ga2O3 bases photodetectors. This pronounced valence band barrier can strongly influence the transport of photo-generated charge carriers, especially the extraction of holes in the depletion region. By introducing nitrogen (N) during the growth process, we elevated the valence band of Ga2O3 by 0.43 eV. The organic high-molecular-weight material of PEDOT:PSS has been utilized in conjunction with Ga2O3 to construct heterojunction photodetectors. The photodetectors exhibit excellent self-powered characteristics, with responsivity, detectivity, and response time being nearly ten times higher than those of Ga2O3 photodetectors before band structure modulation. The investigation into modulating the band structure of Ga2O3 carried out in this study will lay the theoretical foundation and provide technical solutions for developing satisfactory self-powered photodetectors.

Revealing light-induced charge density wave melting and carrier redistribution in 1T-TiSe2

Abstract Capturing the ultrafast dynamics over a large momentum space is critical for revealing the relationship between the electronic and structural modulation in quantum materials. Here, by performing time- and angle-resolved photoemission spectroscopy measurements at Synergetic Extreme Condition User Faclity (SECUF) equipped with extreme ultraviolet light source, we reveal the ultrafast dynamics of a charge density wave (CDW) material 1T-TiSe2 upon photo-excitation. The pump-induced CDW melting is revealed from two aspects, a gap closing of CDW at the Brillouin zone (BZ) center and a weakening of the CDW folded band at the BZ boundary. By comparing the transient electronic structure and spectral weight over a large momentum space, we further reveal the carrier redistribution involving excitation of electrons from the Γ point to the M point. Our work provides a comprehensive picture on the physics and ultrafast dynamics of a CDW material across the entire BZ.

Gastrointestinal health anti-diarrheal mixture relieves spleen deficiency-induced diarrhea through regulating gut microbiota.

This study evaluated the therapeutic efficacy of the gastrointestinal health anti-diarrheal mixture (GHAM) on diarrhea induced by spleen deficiency, focusing on its modulation of gut microbiota. Using specific pathogen-free Wistar rats, a spleen deficiency model was created through senna leaf gavage. Rats were divided into control, model, positive control, and GHAM treatment groups. After a 14-day treatment, fecal samples were analyzed via 16S rDNA sequencing to assess microbiota alterations. GHAM significantly mitigated diarrhea and enhanced food intake and fecal quality. It increased the abundance of beneficial bacteria, such as Romboutsia and Clostridium_sensu_stricto_1, and decreased the levels of diarrhea-associated bacteria, such as Prevotellaceae and Bacillus, thereby improving microbiota functionality. GHAM's modulation of gut microbiota structure and function effectively alleviated spleen deficiency-induced diarrhea, positioning it as a potential natural herbal treatment for gastrointestinal ailments. This study lays the groundwork for further exploration of GHAM's regulatory impact on gut health.

Enhancing photocatalytic H2O2 production of donor−acceptor polymers by modulation of polymerization modes

The photoelectrical properties of donor−acceptor (D−A) polymers are largely determined by the chemical structure. Thus, the modulation of molecular structure is critical for improving the photocatalytic performance of D−A polymers. Herein, three D−A polymers (NMP, NMT, and NMB) with tunable acceptor moieties are synthesized via controlling polymerization modes between donor and acceptor units. Such regulation of molecular structure not only endows optimal D−A polymers (NMP) with highly efficient photoinduced exciton dissociation, enhanced O2 adsorption/activation, and optimized photocatalytic reaction pathway, but also restrains the decomposition of formed H2O2. Furthermore, experimental characterizations and theoretical calculations verify that the O2 adsorption sites in NMP also serve as active centers for the catalysis, which accelerates the photocatalytic kinetics. Thanks to these merits, NMP exhibits an enhanced performance for H2O2 photosynthesis with a yield of 2552.5 μmol h−1 g−1 in the air atomosphere under AM 1.5G irradiation and possesses a high photostability. This work provides an effective strategy to design the highly efficient D−A polymers for photocatalytic energy conversion.

Polar-Twisted, Nano-Modulated Nematics: Form Chirality and Physical Properties

Recently, two new polymorphs have been added to the nematic class: the polar-twisted nematic (NPT) in 2016 and the ferroelectric nematic (NF) in 2020. Comprised of achiral molecules, both exhibit local polar ordering and adopt modulated structures, right- and left-handed helical organizations—form chirality—albeit on vastly different dimensional scales; modulations have a ~10 nanometer pitch in the NPT and ~500 nm in the NF. Here, we focus on the structure and symmetries of the NPT phase and the ensuing physical properties. Based on an array of order parameters that fully describe the molecular ordering and the nano-modulations thereof, we present a consistent formulation of the dielectric, optical, surface anchoring, and elasticity properties of the NPT materials. We show that these properties are distinctly different from those associated with an elastically modulated, locally uniaxial, nematic.

Pseudohalide Anions Driven Structural Modulation in Distorted Tetrahedral Manganese(II) Hybrids toward Tunable Green-Red Emissions.

Mn(II)-based halides have recently garnered significant interest as emerging luminescence materials for diverse photonic applications. Generally, Mn(II) hybrids with tetrahedral coordination show green emission, however, ones with octahedral coordination give red emission. Herein, we design the synthesis of tetrahedral Mn(II) pseudohalide hybrids, (RPh3P)2MnBrxNCS4-x (R= phenyl, pentyl or methyl; Ph3P = triphenylphosphine; x = 1 - 3), achieved by gradually substituting bromides with pseudohalides (NCS-). Compared to the green-emitting A2MnBr4 (512 nm), the mixed hybrids exhibit significantly distorted [MnBrxNCS4-X] tetrahedra with high dipole moment, thus leading to the distinct Stokes shift energies and noticeable red shift emission in the range of 549 ~ 613 nm. Furthermore, the photoluminescence quantum yield (PLQY) of these hybrids correlates strongly with the pair correlation function of Mn(II) ions, specifically the Mn···Mn distance. These findings highlight the critical role of dipole moments in determining the emission properties and expand the luminescent family of Mn(II) pseudohalide hybrids.

Highly dispersive optical solitons with polarization–mode dispersion for non–local law of self–phase modulation

Highly dispersive optical solitons with polarization–mode dispersion for non–local law of self–phase modulation

Review and Outlooks on Electron Migration and Structural Modulation of Metal–Organic Frameworks for Sustainable Fuel Generation

Review and Outlooks on Electron Migration and Structural Modulation of Metal–Organic Frameworks for Sustainable Fuel Generation

Entropy-engineered perovskite cathodes: A novel approach for efficient and durable CO2 electrolysis

The application of solid oxide electrolysis cells (SOECs) for high-temperature CO2 reduction reaction (CO2RR) is constrained by the electrochemical activity and stability of the cathode materials. In this study, a series of iron-based perovskite oxides, designed by systematically varying A-site configurational entropy, are investigated as cathode materials for the CO2RR. Experimental results reveal that these high-entropy materials, derived from La1/2Sr1/2FeO3−δ (LSF), exhibit high electrocatalytic activity and durability. Notably, the SOEC with La1/5Sr1/5Pr1/5Ba1/5Ca1/5FeO3-δ (LSPBCF) cathode achieves a remarkable current density of 2.14 A cm−2 at 800 °C and 1.5 V, maintaining excellent stability over 120 h of operation with negligible fluctuations. Density functional theory (DFT) calculations further unveil the electronic structure modulation mechanism of the high-entropy material, revealing that A-site entropy engineering could enhance CO2 adsorption and activation by reducing the oxygen vacancy formation energy. This study underscores the potential of entropy engineering to improve the electrocatalytic performance and stability of other energy conversion systems.