Crystal Growth & Design最新文献

The separation of chlorobenzene (ClBz) and chlorocyclohexane (ClCy) represents a critical industrial challenge owing to their similar boiling points and polarities, which renders traditional distillation energy-intensive and inefficient. Herein, we report a novel flexible hydrogen-bonded organic framework (HOF), X−HOF−12, assembled from a non-planar tetracyano-functionalized 1,4-dihydropyrrolo[3,2-b]pyrrole building block (DPTCN). Single-crystal X-ray diffraction demonstrates that X−HOF−12 adopts a three-dimensional hydrogen-bonded network with penetrating channels, where guest ClBz molecules are stabilized by multiple CN···Cl and C−H···π interactions. Upon thermal removal of ClBz, X−HOF−12 undergoes a reversible structural transformation to a dense, nonporous phase (X−HOF−12a). X−HOF−12a displays exceptional selective adsorption of ClBz over ClCy through a guest-responsive “open-gate” adsorption mechanism, and the purity of ClBz released from the HOF reaches 94.81%. Furthermore, the material preserves high selectivity and structural integrity over multiple adsorption−desorption cycles. This work not only offers a high-performance flexible HOF adsorbent for energy-efficient ClBz/ClCy separation but also provides a design principle for constructing guest-responsive porous materials for precise molecular separations.

The electrical properties of Si-doped β-Ga₂O₃ homoepitaxial films are governed by the interaction between Si donor activation and native point defects formed during metal−organic chemical vapor deposition (MOCVD) growth. Although growth pressure directly affects precursor transport, boundary-layer evolution, gas-phase reactions, and surface kinetics, its role in regulating defect-mediated carrier transport remains insufficiently understood. Here, we systematically investigate the effect of the growth pressure on the structural, electrical, and defect properties of MOCVD-grown Si-doped β-Ga₂O₃ (100) homoepitaxial films. The film grown at 40 mbar exhibits a carrier concentration of 4.7 × 10¹⁷ cm⁻³ and a Hall mobility of 120.0 cm²/(V·s). As the growth pressure increases from 50 mbar to 80 mbar, the β-Ga₂O₃ films show a much lower dopant activation efficiency and lower Hall mobility. Combined temperature-dependent Hall, cathodoluminescence, and X-ray photoelectron spectroscopy analyses indicate that elevated pressure reduces the concentration of electrically active Si_Ga(I) donors, which dominates the decrease in carrier concentration, while increasing vacancy-related defects, including gallium-oxygen divacancy (V_Ga-V_O) complexes and oxygen vacancy (V_O)-related oxygen-deficient environments, which act as scattering centers and lower the mobility. Lateral MOSFETs fabricated on the film grown at 40 mbar achieve a drain on/off ratio above 10⁹, a specific on-resistance of 169.8 mΩ·cm², and a breakdown voltage exceeding 3 kV. This work reveals how growth pressure modulates the formation of native defects and defect-mediated carrier transport in Si-doped β-Ga₂O₃ homoepitaxy, providing mechanistic insight into developing high-mobility channel layers for β-Ga₂O₃ power devices.

The crystal packing of five atropisomers with two C(aryl)-N(heterocyle) chiral axes, namely, four 1,3-bis[thioxo-thiazolinyl]- and one 1,3-[oxo/thioxo-thiazolinyl] aromatic compounds, was investigated by single-crystal X-ray diffraction. The aim is to establish the relevance of S···S/S···O chalcogen interactions and S···H weak hydrogen bonds in the crystalline network. The high number of alkyl substituents, together with hindered rotation about the C−N bonds, suggests that dispersion is the primary contributor to crystal cohesion. However, even weak, highly directional contacts such as C−H···S and S···S could be emphasized as significant forces in the crystalline supramolecular network. Chalcogen S···S/OC synthon was identified as a pattern along the series of compounds, and replacing S···SC with S···OC confirmed the propensity of these chalcogen interactions, CO being a stronger nucleophile. DFT, NBO, and QTAIM methods were used to define the type and features of the S···S/S···O interactions even at distances 10% beyond the sum of the Bondi van der Waals radii (ΣvdW). SAPT analysis revealed dispersion-driven interactions even when σ-hole interactions were geometrically within the chalcogen bond definition.

Thin-film strontium titanate (SrTiO₃, STO) layers grown on silicon require accurate stoichiometry and single-crystalline order to exploit their functional properties optimally. Oxide molecular beam epitaxy can provide an epitaxial interface, but suffers from source oxidation and resulting flux instabilities, yielding only a narrow growth process window for cationic stoichiometry control. Here, we investigate post-growth annealing in oxygen as a pathway to drive the STO layer toward stoichiometry in intentionally Sr-rich epitaxial STO films on silicon (001). Annealing over a broad temperature range revealed two distinct Sr-segregation mechanisms. Below 800 °C, excess Sr segregates toward the surface, forming SrO outgrowths that progressively sublimate at elevated temperatures. Above 800 °C, a second mechanism dominates: Sr accumulates within the interfacial SiO₂ layer formed by oxygen diffusion at the STO/Si interface. Together, these mechanisms effectively remove excess Sr from the STO lattice, yielding a more stoichiometric perovskite layer. Our results demonstrate that growing slightly Sr-rich STO templates followed by controlled annealing provides a practical route to improve crystalline quality, offering a scalable strategy for high-quality STO integration on silicon.

Synthetic methods of heterospin compounds based on copper hexafluoroacetylacetonate [Cu(hfac)₂] and nitronyl nitroxide radicals containing fluorinated alkyl substituents in the pyrazole ring 2-(1-R-3-pyrazol-4-yl)-4,4,5,5-tetramethyl-2-imidazoline-3-oxide-1-oxyl, where R = CHF₂ (L¹²), CH₂CH₂F (L²¹), CH₂CHF₂ (L²²) or CH₂CF₃ (L²³) were developed. Single crystals of two chain polymers [Cu(hfac)₂(L¹²)]_n and [Cu(hfac)₂L²³]_n·0.5C₆H₁₄ and solvates of molecular [Cu₃(hfac)₆(L²¹)₂]·C₆H₁₄, [Cu₃(hfac)₆(L²²)₂]·2CH₂Cl₂, [Cu₅(hfac)₁₀(L²¹)₄]·solv (solv = C₆H₁₄, 2CH₂Cl₂) and [Cu₅(hfac)₁₀(L²²)₄]·C₆H₁₄ complexes were grown. Their structures and magnetic properties were studied. It was established that upon cooling of the [Cu₅(hfac)₁₀(L²¹)₄]·2CH₂Cl₂ crystal, a magneto-structural phase transition associated with a reduction in the Cu−O_NO distances in the environment of the central Cu atom is realized. The transformation of this three-spin exchange cluster {>N−O^•−Cu(II)−^•O−N<} leads to a change in the nature of the exchange interactions from ferro-to antiferromagnetic, which is reflected in the type of temperature dependence of the effective magnetic moment.

The study of polymorphism in drug crystals is of great importance due to its implications on patentability and the biopharmaceutical attributes of an active pharmaceutical ingredient (API). The study of polymorphism, particularly in multicomponent systems, is more challenging due to greater complexity and a larger number of variables involved. We report here three polymorphs (I, II, and III) and a monohydrate (form IV) of the COX-2 inhibitor etoricoxib, with the 2,6-dihydroxybenzoic acid 1:1 salt. We noted that a choice of crystallization solvent (polar vs non-polar) and method (mechanochemical vs solution) can yield specific polymorphs (I or II). Additionally, we found that a skewed crystallization stoichiometry also influences crystallization outcomes, leading to the isolation of another metastable polymorph, III. The reported crystal forms were thoroughly studied using thermal, diffraction, spectroscopic, and microscopic methods. Additionally, the relative stabilities, phase transformations, and physicochemical properties of reported crystalline salts were studied.

Cocrystallization via VPSZ coagglomeration have emerged as promising strategies to modulate this sensitivity without sacrificing performance, however, the structural drivers that govern these effects still demand systematic exploration to unlock their full potential. This study focuses on the impact sensitivity (IS) and electric spark sensitivity (EES) of co-agglomerated crystals/co-crystals (CACs) of the cyclic nitramines RDX, β-HMX, δ-HMX, BCHMX, and β-CL-20. The impact-sensitivity values were determined using the BAM method, whereas the EES values have been evaluated in accordance with the Czech Defense Standard ČOS137601 (incorporated into STANAG 4490). All correlations of the IS and EES data with molecular-structure characteristics have confirmed that both types of sensitivities are intrinsic properties of energetic materials. Converting these nitramines into cocrystals/CACs leads to the entering coformer generally exhibiting higher shock sensitivity than it does in its pure state. However, it is also possible to prepare cocrystals with lower shock sensitivity than that of both of their pure coformers. In the conformer PANi the sensitivity of nitramine CACs to electric sparks is higher than the sensitivity of the pure nitramine coformer the composite. The principles of the sensitivity behaviour of the CACs investigatedare explained based on the FTIR analysis of symmetric N−O bond stretching vibrations and changes in the mesomeric equilibrium in the nitramine grouping. Further established - the linear correlations between IS and EES. New linear correlations are identified between the values of both sensitivity types and the specific surface areas of CACs - microcrystals, providing a practical, spectroscopic structure-based framework for anticipating and ultimately crystal engineering through crystal design the safety profile of nitramine-based energetic cocrystals.

A new heteroleptic Co(II)-based metal−organic framework (MOF), {[Co₂(L)(bib)_1.5(H₂O)]·2H₂O}_n (1), is synthesized using 5,5′-(1,3-phenylenebis(methyleneoxy)diisophthalate) (H₄L) and 4,4′-bis(imidazolyl)biphenyl (bib) as structurally complementary linkers and characterized. The structural analysis reveals that 1 adopts a robust 2-fold interpenetrated 3D framework with a (4,6)-connected fsc topology, whose highly interlocked architecture contributes to structural stability in aqueous media. The flexible V-shaped polycarboxylate ligand promotes extended connectivity, while the rigid nitrogen-rich biphenyl-imidazole linker enhances framework stability via strong coordination and π···π stacking interactions. Adsorption studies demonstrate that MOF 1 exhibits remarkable selectivity and efficiency toward the anionic dye Congo Red (CR), achieving 99.55% removal and a maximum adsorption capacity (q_max) of 5529 mg·g⁻¹ at 20 °C under mild conditions. Dosage optimization identifies 9 mg of MOF 1 as optimal, providing 98.94% removal and 5496 mg·g⁻¹ capacity under near-ambient conditions. pH-dependent studies show maximum uptake at pH 6, where electrostatic attraction, hydrogen bonding, and framework integrity act synergistically. Furthermore, MOF 1 maintains a high recovery efficiency of 87.50% over multiple cycles. The material retains an appreciable adsorption performance over repeated cycles, although some loss in capacity occurs during successive adsorption−desorption treatments. The combination of high adsorption capacity, rapid dye removal, and structural stability positions MOF 1 as a promising candidate for sustainable wastewater dye remediation.

Integrating strain and ligand effects with surface defects can precisely modulate the d-band center of Pt-based core−shell catalysts for boosting their performance in fuel cell applications. However, it remains a challenge to synthesize defect-rich Pt-based core−shell nanocrystals in a water-based protocol and to establish a clear structure−property relationship. Herein, we present a controllable synthesis of defect-rich 20 nm Pd@Pt core−shell nanobranches (NBs) via a stepwise reduction route that simultaneously exploits surface crystal defects, strain, and ligand effects to enhance both activity and stability toward electrocatalytic methanol oxidation. Multitwinned Pd NBs were first prepared through oriented attachment of primary nanocrystals in a one-pot aqueous wet-chemical method. Defect-rich Pd@Pt core−shell NBs were then obtained by introducing Pt precursors into the same protocol. By carefully tuning the precursor concentrations, we achieved precise control over shell thickness and composition, thereby strategically tuning the d-band center of the Pd@Pt NBs. Electrocatalytic evaluation revealed a distinct volcano-type relationship between the d-band center position and activity for the Pd@Pt NBs. Notably, defect-rich Pd₅@Pt₁ NBs achieved mass activities of 0.7 mA $m_{ECSA}^{-2}$ and 1.47 A ${mg}_{PGM}^{-1}$⁠, representing 11.67-fold and 4.45-fold enhancement compared to commercial Pt/C, respectively.

Effective detection of pollutants in water is of great significance for environmental detection. In this study, the complex {[Zn(Hbsal)₂(dpa)]·2CH₃CH₂OH}_n (1) (H₂bsal = 5-bromosalicylic acid, dpa = bis(4-pyridyl)amine) was successfully synthesized by hydrothermal synthesis method. 1 exhibits strong fluorescence emission, excellent anti-interference capability, and good reusability, making it an ideal material for the detection of aqueous-phase pollutants. The experimental results show that 1 has specific sensing recognition for Cr³⁺, LVX, and Cys, and the limits of detection (LOD) are 2.86 × 10⁻⁵ M, 2.51 × 10⁻⁵ M, and 5.84 × 10⁻⁵ M. These results indicate that 1 can be used as sensing fluorescent probes for Cr³⁺, LVX, and Cys in aqueous solution and has broad application prospects in environmental detection.