Halogen Bond Unlocks Ultra-High Birefringence.

Anisotropy is crucial for birefringence (Δn) in optical materials, but optimizing it remains a formidable challenge (Δn >0.3). Supramolecular frameworks incorporating π-conjugated components are promising for achieving enhanced birefringence because of their structural diversity and inherent anisotropy. Herein, we first synthesized (C6H6NO2)+Cl- (NAC) and then constructed a halogen-bonded supramolecular framework I+(C6H4NO2)- (INA) by halogen aliovalent substitution of Cl- with I+. The organic moieties are protonated and deprotonated nicotinic acid (NA), respectively. The antiparallel arrangement of birefringent-active units in NAC and INA leads to significant differences in the bonding characteristics between the interlayer and intralayer domains. Moreover, the [O⋅⋅⋅I+⋅⋅⋅N] halogen bond in 1D [I+(C6H4NO2)-] chain exhibits stronger interactions and stricter directionality, resulting in a more pronounced in-plane anisotropy between the intrachain and interchain directions. Consequently, INA exhibits exceptional birefringent performance, with a value of 0.778 at 550 nm, twice that of NAC (0.363 at 550 nm). This value significantly exceeds those of commercial birefringent crystals, such as CaCO3 (0.172 at 546 nm), and is the highest reported value among ultraviolet birefringent crystals. This work presents a novel design strategy that employs halogen bonds as connection sites and modes for birefringent-active units, opening new avenues for developing high-performance birefringent crystals.

A Highly Deficient Medium-Entropy Perovskite Ceramic for Electromagnetic Interference Shielding under Harsh Environment.

Materials that can provide reliable electromagnetic interference (EMI) shielding in highly oxidative atmosphere at elevated temperature are indispensable in the fast-developing aerospace field. However, most of conductor-type EMI shielding materials such as metals can hardly withstand the high-temperature oxidation, while the conventional dielectric-type materials cannot offer sufficient shielding efficiency in gigahertz (GHz) frequencies. Here, a highly deficient medium-entropy (ME) perovskite ceramic as an efficient EMI shielding material in harsh environment, is demonstrated. The synergistic effect of entropy stabilization and aliovalent substitution on A-site generate abnormally high concentration of Ti and O vacancies that are stable under high-temperature oxidation. Due to the clustering of vacancies, the highly deficient perovskite ceramic exhibits giant complex permittivity and polarization loss in GHz, leading to the specific EMI shielding effectiveness above 30 dB/mm in X-band even after 100 h of annealing at 1000 °C in air. Along with the low thermal conductivity, the aliovalent ME perovskite can serve as a bifunctional shielding material for applications in aircraft engines and reusable rockets.

Efficacious destruction of typical aromatic hydrocarbons over CoMn/Ni foam monolithic catalysts with boosted activity and water resistance.

Developing cost-effective monolith catalyst with superior low-temperature activity is critical for oxidative efficacious removal of industrial volatile organic compounds (VOCs). However, the complexity of the industrial flue gas conditions demands the need for high moisture tolerance, which is challenging. Herein, CoMn-Metal Organic Framework (CoMn-MOF) was in situ grown on Ni foam (NiF) at room temperature to synthesize the cost-effective monolith catalyst. The optimized catalyst, Co1Mn1/NiF, exhibited excellent performance in toluene oxidation (T90 = 239 °C) due to the substitution of manganese into the cobalt lattice. This substitution weakened the Co-O bond strength, creating more oxygen vacancies and increasing the active oxygen species content. Additionally, experimentally and computationally evidence revealed that the mutual inhibiting effect of three typical aromatic hydrocarbons (benzene, toluene and m-xylene) over the Co1Mn1/NiF catalyst was attributed to the competitive adsorption occurring on the active site. Furthermore, the Co1Mn1/NiF catalyst also presents outstanding water resistance, particularly at a concentration of 3 vol%, where the activity is even enhanced. This was attributed to the lower water adsorption and dissociation energy derived from the interaction between the bimetals. Results demonstrate that the dissociation of water vapor enables more reactive oxygen species to participate in the reaction which reduces the formation of intermediates and facilitates the reaction. This investigation provides new insights into the preparation of oxygen vacancy-rich monolith catalysts with high water resistance for practical applications.

High-Humidity-Tolerant Chloride Solid-State Electrolyte for All-Solid-State Lithium Batteries.

Halide solid-state electrolytes (SSEs) hold promise for the commercialization of all-solid-state lithium batteries (ASSLBs); however, the currently cost-effective zirconium-based chloride SSEs suffer from hygroscopic irreversibility, low ionic conductivity, and inadequate thermal stability. Herein, a novel indium-doped zirconium-based chloride is fabricated to satisfy the abovementioned requirements, achieving outstanding-performance ASSLBs at room temperature. Compared to the conventional Li2ZrCl6 and Li3InCl6 SSEs, the hc-Li2+xZr1-xInxCl6 (0.3 ≤ x ≤ 1) possesses higher ionic conductivity (up to 1.4 mS cm-1), and thermal stability (350 °C). At the same time, the hc-Li2.8Zr0.2In0.8Cl6 also shows obvious hygroscopic reversibility, where its recovery rate of the ionic conductivity is up to 82.5% after 24-h exposure in the 5% relative humidity followed by heat treatment. Theoretical calculation and experimental results reveal that those advantages are derived from the lattice expansion and the formation of Li3InCl6 ·2H2O hydrates, which can effectively reduce the migration energy barrier of Li ions and offer reversible hydration/dehydration pathway. Finally, an ASSLB, assembled with reheated-Li2.8Zr0.2In0.8Cl6 after humidity exposure, single-crystal LiNi0.8Mn0.1Co0.1O2 and Li-In alloy, exhibits capacity retention of 71% after 500 cycles under 1 C at 25 °C. This novel high-humidity-tolerant chloride electrolyte is expected to greatly carry forward the ASSLBs industrialization.

LiGa(IO3 )4 : An Excellent NLO Material with Unprecedented 2D [Ga(IO3 )4 ]∞ - Layer Synthesized by Aliovalent Substitution.

Nonlinear optical (NLO) crystals are indispensable for the solid-state lasers for their ability to expand wavelength spectral to the regions where the directing lasing is difficult or even impossible, yet the rational design of a high-performance NLO crystal remains a great challenge owing to the severe structural and properties' requirements. Herein, a new noncentrosymmetric (NCS) and polar gallium iodate, LiGa(IO3 )4 , with a novel 2D anionic layer, is successfully designed and synthesized by the aliovalent substitution strategy based on classic α-LiIO3 . The 2D [Ga(IO3 )4 ]∞ - layer in LiGa(IO3 )4 is built from the GaO6 octahedra and highly polarizable units IO3 . Compared with its parent compound, the partial replacement of A-site Li+ cation with main group Ga3+ cation facilitates LiGa(IO3 )4 to possess excellent NLO properties, including the large second-harmonic generation (SHG) response (14 × KH2 PO4 (KDP) @ 1064 nm), wide bandgap (4.25 eV), large birefringence (0.23 @ 1064 nm), and wide optical transparency from UV to mid-IR. These reveal that LiGa(IO3 )4 will be a promising NLO crystal.

Enhancing interface stability and ionic conductivity in the designed Na3SbP0.4xS4-xOx sulfide solid electrolyte through bridging oxygen.

The all-solid-state sodium battery has emerged as a promising candidate for energy storage. However, the limited electrochemical stability of the solid electrolyte, particularly in the presence of Na metal at the anode, along with low ionic conductivity, hinders its widespread application. In this work, the design of P and O elements in Na3SbS4 solid electrolyte was investigated through a series of structural tests and characterizations. The electrochemical stability was remarkably improved in the Na/Na3SbP0.16S3.6O0.4/Na battery, exhibiting a stability of 260 h under a current of 0.1 mA cm-2. Additionally, the room temperature conductivity of Na3SbP0.16S3.6O0.4 was enhanced to 3.82 mS cm-1, maintaining a value comparable to commercial standards. The proposed design strategy provides an approach for developing sodium ion solid-state batteries with high energy density and long lifespan. The stability of the solid electrolyte interface at the Na | solid electrolyte interface proves critical for the successful assembly of all-solid-state sodium ion batteries.

Electrochemically Stable Li3-xIn1-xHfxCl6 Halide Solid Electrolytes for All-Solid-State Batteries.

Halide solid electrolytes (SEs) stand out among the many different types of SEs owing to their high ionic conductivity and excellent oxidative stability. Aliovalent substitution is a common strategy to enhance the ionic conductivity of halide electrolytes, but this strategy significantly decreases their electrochemical stability. Herein, we report Hf-substituted Li3InCl6 (Li3-xIn1-xHfxCl6, 0 ≤ x ≤ 0.7) SEs, in which a low concentration (0.1 ≤ x ≤ 0.5) of Hf enhances the ionic conductivity without affecting the electrochemical stability. Among them, Li2.7In0.7Hf0.3Cl6 exhibits a high ionic conductivity of 1.28 mS cm-1 and a wide electrochemical stability window of 2.68-4.22 V. All-solid-state batteries fabricated using Li2.7In0.7Hf0.3Cl6 SE present high discharge capacity and good cycling stability at 25 °C. Furthermore, we summarize the methods of crystal structure regulation by which aliovalent substitution of halide SEs is achieved and discuss potential research directions in the design of novel halide SEs with high ionic conductivity and electrochemical stability.

Cobalt-Enhanced Mass Transfer and Catalytic Production of Sulfate Radicals in MOF-Derived CeO2 • Co3 O4 Nanoflowers for Efficient Degradation of Antibiotics.

Antibiotics discharge has been a critical issue as the abuse in clinical disease treatment and aquaculture industry. Advanced oxidation process (AOPs) is regarded as a promising approach to degrade organic pollutants from wastewater, however, the catalysts for AOPs always present low activities, and uncontrollable porosities, thus hindering their further wider applications. In this work, an aliovalent-substitution strategy is employed in metal-organic framework (MOF) precursors assembly, aiming to introduce Co(II/III) into Ce-O clusters which could modify the structure of the clusters, then change the crystallization, enlarge the surface area, and regulate the morphology. The introduction of Co(II/III) also enlarges the pore size for mass transfer and enriches the active sites for the production of sulfate radicals (SO4• - ) in MOF-derived catalysts, leading to excellent performance in antibiotics removal. Significantly, the CeO2 •Co3 O4 nanoflowers could efficiently enhance the generation of sulfate radical SO4• - and promote the norfloxacin removal efficiency to 99% within 20 min. The CeO2 •Co3 O4 nanoflowers also present remarkable universality toward various antibiotics and organic pollutants. The aliovalent-substitution strategy is anticipated to find wide use in the exploration of high-performance MOF-derived catalysts for various applications.

Anionic Aliovalent Substitution from Structure Models of ZnS: Novel Defect Diamond-like Halopnictide Infrared Nonlinear Optical Materials with Wide Band Gaps and Large SHG Effects.

To design pnictide nonlinear optical materials with wide band gap and large second-harmonic generation, the heavy halogen I was introduced into pnictides through anionic aliovalent substitution with diamond-like ZnS as templates. Thus, four excellent halopnictide-based infrared nonlinear optical crystals, MII 3 PnI3 (MII =Zn, Cd; Pn=P, As), were obtained. They all exhibited defect diamond-like structures with highly parallel-oriented [MII PnI3 ] mixed-anionic tetrahedral groups, leading to excellent physical properties including wide band gaps (2.38-2.85 eV), large second harmonic generation responses (2.7-5.1×AgGaS2 ), high laser-induced damage thresholds (5.5-10.7×AgGaS2 ), and good IR transparency. In particular, Cd3 PI3 and Cd3 AsI3 achieved phase-matching (Δn=0.035 and 0.031) that their template ß-ZnS could not do. Anionic aliovalent substitution provides a feasible strategy to design novel promising halopnictide IR NLO materials.

Enhanced Proton Conductivity by Aliovalent Substitution of Cadmium for Indium in Dimethylaminium-Templated Metal Anilicates.

Metal-organic frameworks (MOFs) with excellent proton conducting ability are crucial to fuel cells, chemical sensors, and redox flow batteries, but achieving them remain a challenge because of the difficulty in simultaneous fulfillment of large number of proton carriers, high mobility of protons, and long-term durable proton conduction. To explore a simple, efficient, and general route toward highly proton-conducting MOFs, we propose herein an aliovalent substitution metal strategy for isostructural aminium-templated MOFs which benefit the acquisition of rich proton sources without modifying ligands or exchanging protic organic molecules. This idea is verified by 100-fold enhancement of conductivity in compounds (Me2NH2)2[Cd(mdhbqdc)2] (Cd-BQ) and (Me2NH2) (Me2NH)[In(mdhbqdc)2] (In-BQ) (H2mdhbqdc = dimethyl 3,6-dihydroxy-2,5-benzoquinone-1,4-dicarboxylic acid) that feature three-dimensional diamond-like structures with two-dimensional intersected channels. Accompanied by the in situ formation of an anilicate ligand, a great number of -OH groups are grafted onto the inner wall of pores, which interact with neutral Me2NH and/or protonated Me2NH2+ cations via N-H···O hydrogen bonds. The high concentration of protons and dynamics of protic amines in the porous framework readily leads to a moderate conductivity of In-BQ (2.10 × 10-4 S cm-1, at 303 K under 95% RH) and an activation energy of 0.73 eV (95% RH). It should be noted that the aliovalent substitution of Cd(II) for In(III) results in the doubling of dimethylaminium proton carriers in Cd-BQ, indicating more frequent hopping and multiple proton-transfer pathways. This indication is supported by a very high protonic conductivity of 2.30 × 10-2 S cm-1 and a reduced activation energy of 0.48 eV under the same conditions. Molecular dynamics simulations visually elucidate the fact that compared with In-BQ, aliovalent-substituted Cd-BQ has shorter proton-migration distances, which in combination with more proton numbers results in more frequent hopping and sliding of protons, in agreement with the experimental results.

LiMII (IO3 )3 (MII =Zn and Cd): Two Promising Nonlinear Optical Crystals Derived from a Tunable Structure Model of α-LiIO3.

Excellent nonlinear optical materials simultaneously meet the requirements of large SHG response, phase-matching capability, wide transparency windows, considerable energy band-gap, good thermal stability and structure stability. Herein, two new promising nonlinear optical (NLO) crystals LiMII (IO3 )3 (MII =Zn and Cd) are rationally designed by the aliovalent substitution strategy from the commercialized α-LiIO3 with the perfect parallel alignment of IO3 groups. Compared with parent α-LiIO3 and related AI 2 MIV (IO3 )6 , the title compounds exhibit more stable covalent 3D structure, and overcome the racemic twinning problem of AI 2 MIV (IO3 )6 . More importantly, both compounds inherit NLO-favorable structure merits of α-LiIO3 and show larger SHG response (≈14× and ≈12×KDP), shorter absorption edge (294 and 297 nm) with wider energy band-gap (4.21 and 4.18 eV), good thermal stability (460 and 430 °C), phase-matching behaviors, wider optical transparency window and good structure stability, achieving an excellent balance of NLO properties.

Exploration of New Birefringent Crystals in Bismuth d0 Transition Metal Selenites.

The first examples of bismuth fluoride selenites with d0 -TM/TeVI polyhedrons, namely, Bi4 TiO2 F4 (SeO3 )4 (1), Bi4 NbO3 F3 (SeO3 )4 (2), Bi4 TeO4 F2 (TeO3 )2 (SeO3 )2 (3), Bi2 F2 (MoO4 )(SeO3 ) (4) and Bi2 ZrO2 F2 (SeO3 )2 (5) have been successfully synthesized under hydrothermal reactions by aliovalent substitution. The five new compounds feature three different types of structures. Compounds 1-3, containing TiIV , NbV and TeVI respectively, are isostructural, exhibiting a new 3D framework composed of a 3D bismuth oxyfluoride architecture, with intersecting tunnels occupied by d0 -TM/TeVI octahedrons and selenite/tellurite groups. Interestingly, compound Bi4 TeO4 F2 (TeO3 )2 (SeO3 )2 (3) is the first structure containing SeIV and mixed-valent TeIV /TeVI cations simultaneously. Compound 4 features a new 3D structure formed by a 3D bismuth oxyfluoride network with MoO4 tetrahedrons and selenites groups imbedded in the 1D tunnels. Compound 5 displays a novel pillar-layered 3D open framework, consisting of 2D bismuth oxide layers bridged by the [ZrO2 F2 (SeO3 )2 ]6- polyanions. Theoretical calculations revealed that the five compounds displayed very strong birefringence. The birefringence values of compounds 1-3, especially, are above 0.19 at 1064 nm, which are larger than the mineral calcite. Based on the structure and property analysis, it was found that the asymmetric SeO3 groups (and TeO3 in compound 3) displayed the largest anisotropy, compared with the bismuth cations and the d0 -TM/Te polyhedra, which is beneficial to the birefringence.

A Facile Route to Nonlinear Optical Materials: Three-Site Aliovalent Substitution Involving One Cation and Two Anions.

Two mixed-metal gallium iodate fluorides, namely, α- and ß-Ba2 [GaF4 (IO3 )2 ](IO3 ) (1 and 2), have been designed by the aliovalent substitutions of α- and ß-Ba2 [VO2 F2 (IO3 )2 ](IO3 ) (3 and 4) involving one cationic and two anionic sites. Both 1 and 2 display large second-harmonic generation responses (≈6×KH2 PO4 (KDP)), large energy band gaps (4.61 and 4.35 eV), wide transmittance ranges (≈0.27-12.5 µm), and high relevant laser-induced damage thresholds (29.7× and 28.3×AgGaS2 , respectively), which indicates that 1 and 2 are potential second-order nonlinear optical materials in the ultraviolet to mid-infrared. Our studies propose that three-site aliovalent substitution is a facile route for the discovery of good NLO materials.

Unique Features of the Photocatalytic Reduction of H2O and CO2 by New Catalysts Based on the Analogues of CdS, Cd4P2X3 (X = Cl, Br, I).

Photochemical reduction of H2O and CO2 has been investigated with a new family of catalysts of the formula Cd4P2X3 (X= Cl, Br, I), obtained by the complete aliovalent substitution of the sulfide ions in CdS by P and X (Cl, Br, I). Unlike CdS, the Cd4P2X3 compounds exhibit hydrogen evolution and CO2 reduction from water even in the absence of a sacrificial agent or a cocatalyst. Use of NixPy as the cocatalyst, enhances hydrogen evolution, reaching 3870 (apparent quantum yield (AQY) = 4.11) and 9258 (AQY = 9.83) µmol h-1 g-1, respectively, under artificial and natural (sunlight) irradiation, in the case of Cd4P2Br3/NixPy. Electrochemical and spectroscopic studies have been employed to understand the photocatalytic activity of this family of compounds. Unlike most of the semiconductor-based photocatalysts, Cd4P2X3 catalysts reduce CO2 to CO and CH4 in the absence of sacrificial-agent or cocatalyst using water as the electron source. CO, CH4, and H2 have been obtained with these catalysts under artificial as well as sun-light irradiation. First-principles, calculations have been carried out to understand the electronic structure and catalytic features of these new catalysts.