Heavy-metal fluoride (HMF) glasses exhibit a combination of broad infrared transparency, low phonon energy, and potential fluoride-ion conductivity, rendering them promising candidates for optical and electrochemical applications. However, the atomic-scale environment of La3+ ions, which governs these properties, remains inadequately characterized. In this work, we systematically examine NaF-LaF3 and LiF-LaF3 binary mixtures as model systems using a suite of solid-state nuclear magnetic resonance (NMR) techniques. Our findings reveal markedly distinct behaviors of the alkali cations. NaF readily reacts with LaF3 to form a crystalline NaLaF4 phase, as unambiguously confirmed by 19F and 23Na NMR, along with 2D 19F-23Na HETCOR and CP/MAS experiments. In contrast, LiF exhibits no evidence of forming Li-La-F coordination structures, instead persisting as a phase-separated LiF/ LaF3 composite. This divergence is attributed to the stronger Li-F bonding and the limited coordination flexibility of Li+, which hinders disruption of the LaF3 lattice. These mechanistic insights highlight the critical influence of alkali cation identity on the structural evolution in mixed fluoride systems and offer valuable design principles for ZBLAN and related HMF glasses.

[Background]Fluoride molten salt is a key coolant and fuel carrier for thorium-based molten salt reactors(TMSR).Its microstructure directly determines the physicochemical properties at high temperatures,and ultraviolet-visible(UV-Vis)absorption spectroscopy is an effective method to detect the oxidation states and coordination environments of metal ions in molten salts.Limited by extreme conditions such as high temperature(>500℃),strong corrosion,high volatility and sensitivity to trace H2O/O2,conventional instruments are difficult to realize in-situ characterization of fluoride molten salts.[Purpose]This study aims to develop an in-situ high-temperature UV-Vis absorption spectroscopy system specifically designed for corrosive fluoride molten salts.[Methods]The core of in-situ high-temperature UV-Vis absorption spectroscopy system for corrosive fluoride molten salts was a high-temperature optical furnace with optical paths,integrated with inert atmosphere protection,high-precision temperature control,efficient thermal insulation and corrosion-resistant structure.Performance verifications for this developed spectrometer included temperature calibration,mechanical repeatability and room-temperature benchmark comparison.Using this system,experiments were conducted on FLiNaK and FLiBe molten salts,where the salts were heated to elevated temperatures under an inert atmosphere,and the spectrometer was employed to collect absorption spectra and to monitor the dynamic evolution of chromium species during the reaction process.[Results]Experimental results show that the system operates stably up to 800℃without optical window degradation or baseline drift.At 650℃,FLiNaK-CrF3 exhibits two well-resolved absorption peaks at approximately 450 nm and 700 nm,corresponding to the characteristic d-d transitions of Cr3+.FLiBe-UF4 shows a characteristic absorption spectrum consistent with literature reports.These peak positions deviate from literature values by less than±2 nm.During real-time monitoring of Cr3+in FLiBe at 650℃,the absorbance at 450 nm decreases from 1.28 to 0.39 within 120 min.[Conclusions]The developed UV-Vis absorption spectroscopy system in this study has the ability of in-situ characterization of molten salt species and redox processes in high-temperature and strong corrosion environments,providing an experimentally verified key test platform for the research of molten salt chemistry and corrosion mechanism of TMSR.

Correction for ‘High-temperature and solid-state NMR investigation of the structural evolution and special phase transition in LiF–NaF–BeF 2 mixed salts’ by Jianchao Sun et al. , Phys. Chem. Chem. Phys. , 2025, 27 , 8903–8909.

ABSTRACT Molecular antiferroelectrics (AFEs) with antiparallel dipole alignment are promising for energy‐storage capacitor applications. However, it is challenging to design new molecular AFEs with superior breakdown resistance, owing to the lack of knowledge on the atomic‐level origin regarding AFE orders. Here, we present stable breakdown resistance in 2D perovskite AFE, (2‑MBA) 2 CsPb 2 Br 7 (2‑MBA = 2‑methylbutylammonium), involved with the confinement‐dependent atomic displacement. It shows antiferroelectricity with a large spontaneous polarization of 5.0 µC/cm 2 . Particularly, the cage‑confined Cs + cations display atomic displacement to create stable antifatigue merits, including high breakdown field up to 175 kV/cm and the fatigue endurance beyond ∼10 6 cycles, falling in the range of the highest level for molecular AFEs. Combination of energy barrier calculation and in situ solid‐state NMR spectroscopy was used to reveal the crucial role of displacive dynamics. Contrary to order‐disordering dynamics, it is the high energy barrier ( E a = 2.91 eV) of cage‐confined Cs + cation displacement that leads to the increase in Curie temperature ( ∼ 327 K) and forward coercive field (∼56.8 kV/cm). Such attributes allow for AFE switching under stronger external stimuli, thus endowing stable fatigue resistance even at higher breakdown fields. This work provides a feasible principle of delicately manipulating cage‐confined dynamics to design new electric‐ordered candidates.

Molten fluorides, recognized as a vital class of high-temperature functional materials, have attracted considerable interest in advanced nuclear energy systems and high-temperature metallurgical processes due to their outstanding thermal stability, broad electrochemical window, and low neutron absorption cross-section. The physicochemical properties of these melts are primarily dictated by the dynamic coordination equilibrium between fluoride ions (F-) and metal ions. This review provides a comprehensive overview of recent progress in understanding the structure-activity relationship between Lewis acidity/basicity (quantified by the F- activity) and the macroscopic physicochemical behavior of molten fluorides. Advanced characterization techniques, such as nuclear magnetic resonance (NMR) and electrochemical methods, have played a critical role in uncovering the dynamic interplay between microscopic coordination environments and acid-base characteristics. Key findings highlight that the acid-base properties of molten fluorides significantly influence essential thermophysical parameters, including viscosity, thermal conductivity, and thermal stability. Moreover, these properties critically affect the corrosion behavior of structural materials and the dissolution mechanisms of oxides through coordination chemistry. By integrating insights across multiple scales, this review establishes a micro-to-macro correlation framework that offers both fundamental understanding and practical guidance for the design and optimization of molten fluoride systems in nuclear and metallurgical applications.

Fluoride ion batteries (FIBs) are considered a promising high-energy-density alternative to conventional lithium-ion batteries. Tetragonal BaSnF4 exhibits high fluoride-ion conductivity; however, its detailed conduction mechanism, particularly regarding the occurrence of the cubic phase in the tetragonal phase, remains to be further clarified. In this work, a sample predominantly composed of t-phase BaSnF4 with a trace amount of c-phase, prepared by ball milling followed by sintering, achieved a high room-temperature conductivity of 2.71 & times; 10(-4) S & centerdot;cm(-1). This enhanced conductivity is attributed to fluoride vacancies generated at the heterointerface between the cubic and the tetragonal phase. Solid-state F-19 nuclear magnetic resonance (NMR) reveals the exchange of fluoride ions between the two phases, suggesting that fluoride ions can migrate across the phase boundary. These findings demonstrate that the common existence of a cubic phase in tetragonal BaSnF4 can be exploited through controllable preparation parameters to enhance ionic conductivity.

Rashba-Dresselhaus (RD) spin splitting provides a crucial physical basis for realizing various advanced spintronic applications. Nevertheless, rationally regulating the RD splitting coefficient (αRD) continues to be a difficult task owing to the still unclear structure-property relationship. In this work, we propose a molecular dipole engineering, the core of which involves introducing halogen atoms with different electronegativities into organic cations, aiming to design and synthesize two-dimensional (2D) ferroelectric semiconductors with strong RD spin splitting. By substituting the organic spacer cations in the parent compound (PMA)2PbCl4 (PMA = benzylammonium), we obtained two new 2D ferroelectric semiconductors, namely, (2F4ClPMA)2PbCl4 (2F4ClPMA = 2-fluoro-4-chlorobenzylammonium) and (2F4BrPMA)2PbCl4 (2F4BrPMA = 2-fluoro-4-bromobenzylammonium). Both variants exhibit significantly enhanced RD splitting coefficients. In particular, (2F4ClPMA)2PbCl4 possesses a large αRD value of 1.878 eV·Å and a persistent spin texture region, which helps amplify its circular photogalvanic effect (CPGE). Through the spin-selective optical transition rule, the effect can enable the differentiation of carriers excited by circularly polarized light (CPL) in momentum space. A photodetector fabricated based on a (2F4ClPMA)2PbCl4 single crystal shows a high asymmetry factor of 0.53 under excitation by UV CPL at 325 nm. This work not only confirms the effectiveness of the molecular dipole engineering in tuning RD spin splitting, but also lays an important material foundation for the development of novel low-power, high-sensitivity spin-optoelectronic devices.

TMSR represents a promising pathway for sustainable nuclear energy, where ThF4 serves as a fuel dissolved in fluoride carrier salts such as FLiBe. However, the solubility and structural behavior of ThF4 in FLiBe remain poorly understood. This study integrates HT-NMR, ss-NMR, and AIMD simulations to systematically investigate the coordination structure and dissolution mechanisms of ThF4 in FLiBe melts. The results show that at low ThF4 concentration (1.2 mol%), Th4+ predominantly exists as isolated coordinated ThF84− complexes with an average Th–F coordination number (CN) of approximately 8.0. As the ThF4 concentration increases, the average Th–Th CN rises from nearly 0 to approximately 2.0, indicating the progressive formation of fluoride-bridged Th–F–Th oligomers. An independent 19F NMR resonance at +43 ppm is directly observed in the molten state at 600 °C, providing experimental evidence for poorly soluble Th–F–Th oligomeric species that do not participate in rapid ionic exchange. Structural analysis indicates that the formation of these oligomers originates from the depletion of free F− ions and discrete BeF42− units, while the weakened spatial separation effect of Li+ ions further promotes Th–F–Th bridge formation. Concentration-dependent ss-NMR measurements reveal that the characteristic signals of these bridged species emerge above approximately 5.5 mol% ThF4, accompanied by new resonances at −3, 20, and 50 ppm. These oligomeric species exhibit poor solubility, which limits the dissolution of ThF4 in FLiBe. These findings elucidate a molecular-scale mechanism underlying the limited solubility of ThF4 in FLiBe, which offers a valuable method for investigating the structural behavior of other actinide fuels and fission products in molten salts.

[This corrects the article DOI: 10.1021/jacsau.4c00177.].

Wearable sensors and flexible energy storage devices impose distinct requirements on ionic conductive hydrogels, particularly regarding the balance between flexibility and conductivity. However, existing hydrogels lack a simple and scalable approach to tailor these properties for targeted applications, meeting the requirements of different applications. Here, we propose a strategy to regulate the microstructure of cellulose-based ionic conductive hydrogels (ICH) by leveraging competitive hydration effects between Zn2+ and Li+ ions, enabling single-step performance tuning. When Zn2+ dominates (ICH-1), hydrated ions expand cellulose chain spacing, enhancing ion mobility and yielding good conductivity (18.48 mS·cm-1). The resulting asymmetric flexible capacitor (ICH-1) achieves a 0-2.0 V voltage window, with exceptional energy density (50.6 Wh·kg-1) and power density (1000.1 W·kg-1). Conversely, Li⁺-dominant ICH-3 exhibits compact cellulose chains, endowing good flexibility (311.84 kPa at 35% strain), ionic conductivity (13.16 mS·cm-1) and sensitive electromechanical performance (GF=2.78). This enables its application as a biomimetic e-skin sensor for real-time human motion monitoring and human-computer interaction. Our method addresses the limitations of conventional ICH fabrication, offering scalable production and demonstrating significant industrial potential.

Molten salts are extensively used in the aluminum production and recycling industries. In this study, we discovered that metallic Al can directly dissolve into molten salts in its zero-valent state, forming nanoclusters-an unusual phenomenon as metals typically dissolve in molten salts in various oxidation states due to corrosion. The dissolved Al can gradually oxidize due to water or oxygen impurities during its diffusion within the molten salts. We thoroughly investigated the interactions between Al and molten salts and analyzed the structure of the reaction products using HT-NMR methods. These findings provide a novel explanation of the interactions and corrosion processes between metals and molten salts.

Antiferroelectric-antiferromagnetic (AFE-AFM) multiferroic materials have received extensive attention due to their applications in high-energy storage devices. However, achieving AFE-AFM properties in a hybrid molecular material is particularly challenging, because electric dipole orders and magnetic dipole orders are often mutually exclusive. Here, we report a molecular strategy that utilizes polar rotors combined with magnetic modules to overcome the above exclusion in a quasi-two-dimensional (Q-2D) hybrid perovskite platform. Based on non-ferroic [CBA]2CoCl4 (CBA = cyclobutylaminium, CBC), F-substituted [DFCBA]2CoCl4 (DFCBA = 3,3-difluorocyclobutylamine, DFCBC) with polar rotors shows AFE-AFM properties. Systematic experimental results reveal that the freezing of rotor movement forms antiparallel arranged dipole arrays, which is the origin of the AFE feature. Moreover, DFCBC exhibits antiferromagnetism from the inorganic [CoCl4]2- component, reaching 1.73N beta at 50 kOe. Our study presents the advantages of the Ruddlesden-Popper (RP) hybrid perovskite molecular rotor platform for realizing AFE-AFM properties. It gives insight into the molecular design for controlling the macroscopic physical properties.

Introducing S vacancies into tin disulfide (SnS2) is crucial for regulating its electrocatalytic CO2 reduction activity. However, conventional methods for generating vacancies often result in uncontrolled defect concentrations. In this study, SnS2 with identical nanolayer structures but varying S-vacancy concentrations was synthesized by reacting different tin salts with high-temperature molten potassium thiocyanate. The results show that although SnS2 derived from SnCl2 exhibits a high S-vacancy concentration, its Faradaic efficiency (FE) for formic acid reaches only 48.2%. In contrast, SnS2 derived from SnSO4 contains fewer vacancies and exhibits an FE of 85.6%. Adjusting the KSCN/Sn salt ratio and applying H2 posttreatment can further optimize the S-vacancy concentration and enhance the CO2 reactivity. DFT calculations confirm that introducing an appropriate S-vacancy concentration can enhance the CO2 adsorption capacity, improve the affinity for the *OCHO intermediate, and accelerate the CO2RR kinetics. This precise vacancy engineering highlights the significance of balancing the defect concentration and catalytic efficiency.

Ionic conductive hydrogels have attracted great attention due to their good flexibility and conductivity in flexible electronic devices. However, because of the icing and water loss problems, the compatibility issue between the mechanical properties and conductivity of hydrogel electrolytes over a wide temperature range remains extremely challenging to achieve. Although, antifreezing/water-retaining additives could alleviate these problems, the reduced performance and complex preparation methods seriously limit their development. In this work, a simple strategy without additives was provided to prepare an ionic conductive cellulose hydrogel (ICH) in one step through molten salt hydrate. The hydrogel featured controllable mechanical properties (0.19 MPa- 0.67 MPa), high ionic conductivity (78.96 mS/cm), excellent freezing resistance (-80 degrees C). More importantly, due the existing metal salts component, the ICH exhibited long-term stability in water-retention ability (75.6 %, after 90 days) and ionic conductivity (85 %, after 90 days) over a wide working temperature range (-80 degrees C to 40 degrees C). Benefiting from these advantages, the ICH exhibited excellent electromechanical performance in human movement detection and movement direction identification, indicating a promising apply for flexible electronic device.

Photoferroelectrics are capturing the growing interest for their unique light-polarization coupling and optoelectronic applicability. However, the formidable challenge persists in coupling electric order and strong photoactivity through precise molecular design, hindering their further application in the field of optoelectronic memory. Herein, the molecular dynamics of aromatic cations in the 2D constrained environments are customized to construct perovskite photoferroelectrics, (4-tert-butylbenzylammonium)2(ethylammonium)2Pb3I10, showing a narrow bandgap (≈1.96 eV) and strong visible-photosensitivity. Notably, multi-level dynamic states of aromatic cations provide the impetus for inducing ferroelectric order and photo-ferroelectric effects. Such captivating characteristics can achieve light-induced multiple polarization, dielectric, and conductivity states. Accordingly, photoferroelectrics are integrated into heterojunction phototransistors that display robust electrical and optical modulation, including diversified synaptic plasticity with low optical program power (≈20 pJ) for each training process. As a noteworthy advancement in the photoferroelectric field, this work will enrich the understanding of the structure-property relationship and shed light on further exploration toward neuromorphic computing.

Interfacial water networks dynamically orchestrate photocatalytic CO2 reduction by concurrently mediating proton relay pathways and regulating CO2 adsorption kinetics, where their evolving microstructure dictates active-site accessibility and proton conduction efficiency. To achieve molecular-level control over water configurations, we engineer a Cu single-atoms and P-sites co-regulated catalyst (Cu-CNP) that modulates interfacial water populations (shifting equilibrium from confined clusters to free water molecules), while restructuring hydrogen-bond networks into strong/weak domains. This dual-functional interface synergistically accelerates proton transport and strengthens CO2 enrichment through competitive confinement effects, as validated by a series of advanced NMR experiment (including chemical exchange saturation transfer and 2D correlation spectroscopy) coupled with in situ C-13-lable CO2 ((CO2)-C-13) NMR adsorption experiments. Consequently, the reconfigured microenvironment accelerates proton migration and intensifies CO2 adsorption affinity, thus driving a 4.46-fold enhancement in CO generation rate versus pristine g-C3N4 and establishing a structure-activity relationship for interfacial water networks that laying a crucial foundation for a deeper understanding of solid-liquid interface catalytic mechanisms.

Optimizing ferroelectric properties is critical for molecule‐based ferroelectrics toward practical applications, including enhanced saturation polarization ( P s ), elevated Curie temperature ( T C ), and reduced coercive field ( E c ). Recent advances in ferroelectrochemistry have provided efficient synthetic strategies to tailor these properties, with a focus on functionalizing organic components. However, the impact of combined molecular symmetry and geometry on ferroelectricity remains less understood. In this work, we construct a series of one‐dimensional ferroelectric hybrid metal halides (HMHs) using C 3v ‐symmetric trigonal pyramidal polar cations to systematically investigate how molecular symmetry and geometry modulate ferroelectric behavior. The model compound (TMS)PbI 3 (TMS = trimethylsulfonium) exhibits ferroelectricity up to its decomposition temperature (530 K), the highest among known HMH ferroelectrics, alongside an exceptionally low E c (0.25 kV cm −1 at 298 K). We demonstrate that the unique C 3v symmetry and trigonal pyramidal geometry of the TMS cation facilitate energy‐favorable uniaxial rotation about the polar 3‐fold axis and 90° polarity flipping during disordering in the ferroelectric–ferroelectric phase transition near 271 K. This partial disorder transition underpins the remarkable high‐temperature ferroelectric phase and low E c . Selenium‐ and phosphorus‐based analogs show similar properties with E c values of 0.55 and 0.47 kV cm −1 , respectively.

Molten salt mixtures of LiF, NaF, and BeF2 are widely recognized as potential solvents and coolants in molten salt reactor applications. The structural effects of LiF addition to the ternary salt were investigated using HT-NMR and solid-state NMR techniques. A distinct phase transition was identified using HT-NMR during the melting process of LiF-NaF-BeF2 ternary salts. The results indicated that the addition of LiF facilitates the transition from a crystalline to an amorphous structure. The influence of Li+ and Na+ on the amorphous structure was analyzed, revealing that Li+ ions exhibit relatively strong interactions with Be-F oligomers. Furthermore, as the temperature increases, the rapid dynamics weaken the interactions between Li+ ions and Be-F oligomers. This weakening of interactions results in the remarkable phase transformation of Be-F oligomers into polymeric chains and networks.

Hydrogen evolution from water, catalyzed by solar energy, is a promising yet challenging endeavor. Small-sized catalysts usually exhibit high utilization and high performance in the hydrogen evolution field. However, the high surface energy tends to make them aggregate. In this study, we introduce a novel molten salt synthesis technique to develop a composite catalyst featuring a TiO2/C3N4 heterojunction to stabilize the small-sized TiO2. High-temperature molten salts create a highly polarized environment that facilitates the formation of a smaller-sized Ti precursor, thereby enhancing the integration of the heterojunction with C3N4 structures and significantly improving the photocatalytic hydrogen evolution performance. Additionally, the oxidation of sacrificial reagents was examined using a quasi-in-situ NMR technique, with a comprehensive discussion of the reaction products and mechanisms. This research offers valuable insights for employing the molten salt approach in the development of photocatalysts and other functional materials.

The rational synthesis of metal–organic frameworks (MOFs) plays a critical role in studying the correlation between their structure and properties. Among various synthesis strategies, electrosynthesis has emerged as a promising approach for the rapid and controllable preparation of various MOFs. Herein, a novel MOF single crystal featuring the porphyrin block and the coordinated linkage between pyridine and cadmium (Cd2+) ions is electrolytically synthesized as millimeter‐sized single crystal under mild ambient condition. Temperature‐dependent changes in its 3D cross‐interpenetrating topology are systematically investigated. Moreover, the as‐synthesized MOF single crystal exhibits typical semiconductive behavior with a narrow bandgap of 1.12 eV. This study exploits the potential of electrosynthesis as a clean and scalable approach to address the synthesis of MOF single crystal.